METHOD OF INDUCING ANGIOGENESIS

Abstract: The invention provides a method of directing blood vessel growth comprising administering an angiogenic mediator to a host, such that a gradient of angiogenic mediator of increasing concentration from an angiogenically functional source location to a potential or actual angiogenically dysfunctional target location is established, whereby blood vessel growth is directed from the source location to the target location.

Description: METHOD OF INDUCING ANGIOGENESIS TECHNICAL FIELD OF THE INVENTION The invention relates to a method for directing blood vessel growth. BACKGROUND OF THE INVENTION Angiogenesis is a complex process involving the disruption of vascular basement membranes, migration and proliferation of endothelial cells, and subsequent blood vessel formation and maturation. Several mediators are known to elicit angiogenic responses, such as promoting revascularization of ischemic tissues. Such angiogenic mediators desirably are administered in a manner such that therapeutic angiogenesis occurs without incidence of harmful side-effects associated with over- dosage (e.g., tissue damage, blindness, psoriasis, arthritis, and/or promotion of tumor metastases) and without any inefficiency in the use of the angiogenic mediator (e.g., misdirection of blood vessel growth). The angiogenic mediators can be administered using multiple applications of the angiogenic mediator to a target tissue. For example, International Patent Application WO 98/32859 discloses a method of inducing angiogenesis by administering multiple applications of a pharmaceutical composition comprising a pharmaceutically acceptable carrier and a recombinant adenoviral vector encoding an angiogenic peptide, such that the level of perfusion of blood to the target tissue is enhanced. Similarly, U.S. Patent 6,121 ,246 discloses multiple administrations of DNA constructs encoding an angiogenic protein and secretory signal sequences directly to tissue of a host. Such techniques do not provide a method of administering an angiogenic mediator such that the controlled growth of blood vessels from a source location to a target location is achieved. Thus, there remains a need for such a method of administration. The invention described herein provides such a method. These and other advantages of the invention, as well as additional inventive features, will be apparent from the description of the invention provided herein. BRIEF SUMMARY OF THE INVENTION The invention provides a method of directing blood vessel growth comprising administering an angiogenic mediator to a host, desirably to at least two different locations in the host, such that a gradient of angiogenic mediator of increasing concentration from an angiogemcally functional source location to a potential or actual angiogenically dysfunctional target location is established, whereby blood vessel growth is directed from the source location to the target location. DETAILED DESCRIPTION OF THE INVENTION The invention provides a method of directing blood vessel growth comprising administering an angiogenic mediator to a host, desirably to at least two different locations in the host, such that a gradient of angiogenic mediator of increasing concentration from an angiogenically functional source location to a potential or actual angiogenically dysfunctional target location is established, whereby blood vessel growth is directed from the source location to the target location. The angiogenic mediator can be any substance that directs the growth of blood vessels from at least one source location to at least one target location, thereby enhancing the level of perfusion of blood, particularly by initiating or enhancing angiogenesis. Angiogenesis in the context of the invention encompasses both the formation of new blood vessels (neovascularization), as well as promoting blood vessel formation, including collateral blood vessel growth. Thus, the angiogenic mediator can be any substance that induces the initiation of angiogenesis at a location not otherwise undergoing angiogenesis, enhances or heightens collateral blood vessel growth to a location already undergoing angiogenesis, or both. The angiogenic mediator can be any suitable angiogenic mediator. The angiogenic mediator typically will be an angiogenic peptide or a nucleic acid that encodes an angiogenic peptide. The angiogenic peptide desirably is an angiogenic growth factor or an angiogenically functional fragment thereof. Many angiogenic growth factors are known in the art. Examples of angiogenic growth factors include fibroblast growth factors (FGFs) (e.g., aFGF, bFGF, and FGF-4) angiogenins (e.g., angiogenin and angiogenin-2), pleiotrophin (PTN, also known as HBNF), midkine, transforming growth factors (e.g., PDGF-BB (Regranex)), (TGFs - e.g., TGF-β), placental growth factors, platelet-derived growth factors (e.g., platelet-derived endothelial cell growth factor), and vascular endothelial growth factors (VEGFs), Del- 1, angiopoietins (e.g., angiopoietin-1 and angiopoietin-2), follistatin, granulocyte colony-stimulating factor (G-CSF), scatter factor/hepatocyte growth factor (HGF), leptin, insulin like growth factors, COUP-TFIT, eNOS, iNOS, MCP-1, proliferin, and ephrins. Other angiogenic mediators include cytokines such as tumor necrosis factor- alpha (TNF-α) and interleukin-8 (IL-8) and transcription factors such as PR39 and HIF-ld. Such factors and their administration are known and described in, for example, U.S. Patents 5,338,840, 5,401,832, 5,532,343, and 5,851,797, International Patent Application WO 95/24473, European Patent Documents 441 763, 476 983, 506 477, 550 296, and 535 337, and Japanese Patent Documents 1038100, 2117698, 2279698, and 3178996. The angiogenic mediator is not limited to angiogenic peptides such as the aforementioned cytokines or growth factors, but may include any suitable compound that induces angiogenesis. Preferably, the angiogenic peptide is a growth factor specific for endothelial cell growth (e.g., an angiopoietin, placental growth factor, or a VEGF). Desirably, the angiogenic peptide strongly promotes angiogenesis in targeted tissues while not inducing the growth of tissues that are not involved in the production of new vascular. Because VEGFs are known to possess these features they are preferred angiogenic peptides. The VEGF can be any suitable VEGF. Preferably, the VEGF is a mammalian VEGF (e.g., a VEGF, VEGF II, VEGF-B, VEGF-C, VEGF-D, VEGF-E, or placental growth factor (P1GF)), an angiogenically functional fragment thereof, or a mimetic of the VEGF or angiogenically functional fragment. Alternatively, the VEGF can be a non-mammalian VEGF, fragment, or mimetic, such as ORFV2-VEGF. Preferably the VEGF is a VEGF-A (also commonly referred to as a VEGF). Preferred VEGF-A isoforms are VEGF ]21 , VEGFι 45 , VEGFι 65 , and VEGF 189 (which are described in, e.g., U.S. Patents 5,332,671, 5,240,848, and 5,219,739). As indicated, the angiogenic peptide can be a mimetic of an angiogenic peptide. Several types of peptide mimetics are known and described in, e.g., U.S. Patent 5,668,1 10 and the references cited therein. An angiogenically functional fragment of an angiogenic peptide, i.e., a fragment obtained from or corresponding to part of an angiogenic peptide which induces or promotes angiogenesis with substantially similar (e.g., at least about 80%, preferably at least about 90%) effectiveness as the corresponding complete angiogenic peptide also can be used. Preferably, the angiogenic peptide is a complete (i.e., non-fragmented) angiogenic peptide. Because of their higher biological activity, VEGF 12) and VEGFι 65 , are particularly preferred VEGFs. A notable difference between VEGF 12 ι and VEGF 165 is that VEGF 121 does not bind to heparin with a high degree of affinity, as does VEGF 165 . VEGFπi is more preferred as the angiogenic peptide than VEGFι 65 . The angiogenic peptide can be a naturally occurring angiogenic peptide or a modified peptide including one or more modifications (e.g., amino acid substitutions, deletions, additions, and/or additions of carbohydrate moieties). The angiogenic peptide can be a multimeric peptide, such as a naturally occurring VEGF heterodimer or homodimer. The angiogenic mediator can be a combination of (i.e., multiple) different angiogenic mediators (e.g., two or more angiogenic peptides and/or nucleic acid(s) encoding angiogenic peptides). In that respect, the different angiogenic mediators desirably affect different biological aspects. For example, an endothelial cell mitogen (e.g., VEGFι 21 , aFGF, or HGF) or nucleic acid encoding such an endothelial cell mitogen can be administered with a mediator that influences endothelial cell migration (e.g., Del-1), a mediator that influences vessel wall maturation (e.g., midkine), a mediator that influences vessel wall dialation (e.g. iNOS), an extracellular matrix degradation factor (e.g., TNF-α), and/or a transcription factor (e.g., PR39), or a nucleic acid encoding such factors. Other suitable combinations of such angiogenic mediators also are contemplated. Thus, the inventive method can include administration of a first angiogenic mediator and a second angiogenic mediator that direct blood vessel growth in different manners. The different angiogenic mediators (e.g., at least three, at least four, at least five, or more co-administered angiogenic mediators) desirably have a synergistic effect when in each other's presence. Examples of preferred combinations of angiogenic mediators include a VEGF-A (particularly or VEGF 165 ) in combination with angiopoietin-1, aFGF (also known as FGF-1), HBNF, a combination thereof, or one or more nucleic acids encoding such combinations. A particularly preferred angiogenic mediator combination comprises an angiogenic mediator that initiates new blood vessel development (e.g., a VEGF), and an angiogenic mediator that is involved in blood vessel maturation (e.g., an angiopoietin), or one or more nucleic acids encoding such a combination. Combinations of angiogenic mediators which result in reduced angiogenic potential typically are not desirable (e.g., angiopoietin-1 is not desirably co-administered with angiopoietin-2 due to potential cross-inhibition of each other's angiogenic potential). The angiogenic mediator can be or comprise a nucleic acid encoding an angiogenic peptide. The nucleic acid can be any suitable nucleic acid molecule. In most instances, because of their greater stability and manipulability, DNA nucleotide angiogenic mediators are preferred. Alternatively, naked RNA nucleotide angiogenic mediators can be advantageous, such as in aspects where transitory expression is sought using a naked polynucleotide vector, or where delivery of the nucleotide is accomplished by positioning the nucleic acid into a retroviral vector. The nucleic acid can encode any suitable angiogenic peptide. For example, the nucleic acid can encode any of the aforementioned angiogenic peptides, or angiogenically functional fragments thereof (e.g., one or more angiogenically functional domains of such peptides). The nucleic acid can include multiple copies of one or more angiogenic genes (e.g., two copies of a VEGF gene). The nucleic acid also can encode any combination of the angiogenic peptides described herein. Preferably the nucleic acid encodes an endothelial specific angiogenic mediator, more preferably a VEGF. Where the nucleic acid encodes multiple angiogenic peptides preferably encodes one of the preferred combinations of co-administered angiogenic peptides described elsewhere herein (e.g., a VEGF and an angiopoietin). The nucleic acid additionally or alternatively can encode an angiogenic peptide receptor. Suitable angiogenic peptide receptors include, for example, VEGF receptors such as FLT-1, KDR (and its homologue FLK-1), FLT-4 (alternative or alternatively-named VEGF receptors include VEGFR-1 , VEGFR-2, and VEGFR-3), and receptors for other angiogenic factors such as FGFR-1, RYK, tie receptor, tie2 receptor, and Eph receptors. When the nucleic acid encoding the angiogenic receptor is expressed, the receptor is incorporated in the cell in which it is expressed, thereby increasing the uptake potential of the cell with respect to angiogenic mediators that interact with the receptor. Thus, one or more non-native receptors can be expressed in a particular cell, the number of native receptors expressed in a cell can be increased, or both. A nucleic acid encoding a substantially functional fragment of such a receptor also can be used (e.g., a receptor fragment exhibiting at least about 80%, or preferably at least about 90%, of the interaction with angiogenic mediators exhibited by the complete receptor). The nucleic acid can encode both an angiogenic peptide and an angiogenic peptide receptor such that expression of the nucleic acid desirable results in increased stimulation by the angiogenic peptide and increased uptake by the angiogenic peptide receptor. A nucleic acid also can encode an angiogenic peptide receptor in place of, rather than in addition to, an angiogenic peptide. Preferably, the nucleic acid comprises, in addition to a sequence encoding the angiogenic peptide, (i.e., "angiogenic sequence"), one or more suitable expression control sequences operably linked to the sequence encoding the angiogenic sequences. An expression control sequence is any nucleotide sequence that assists the expression (e.g., the transcription, translation, or both) of the nucleic acid encoding the angiogenic sequence. The expression control sequence can be naturally associated with the angiogenic sequence (e.g., a naturally-occurring promoter for the nucleic acid encoding angiogenic sequence), or can comprise a heterologous element with respect to the angiogenic sequence. For example, the angiogenic sequence can be operably linked to a constitutive promoters (e.g., the Rous sarcoma virus long terminal repeat (RSV LTR) promoter/enhancer or the cytomegalovirus major immediate early gene (CMV IE) promoter, which is particularly preferred), an inducible promoter, (e.g., a growth hormone promoter, metallothionein promoter, heat shock protein promoter, E1B promoter, or MLP promoter), an inducible-repressible promoter, or a tissue specific promoter (e.g., a smooth muscle cell α-actin promoter, VEGF receptor promoter, or vascular endothelial cadherin promoter). In some instances, host-native promoters may be preferred over non-native promoters (e.g., a human beta actin promoter driving expression of the angiogenic sequence may be preferred in a human host), particularly where strict avoidance of gene expression silencing due to host immunological reactions is desirable. The nucleic acid may alternatively or additionally include a promoter targeted by a controllable transcription binding protein, such as the nucleotide sequences described in U.S. Patents 5,830,462 and 6,015,709. The nucleic acid can include one or more additional elements such as an enhancer, a transcription termination sequence, a polyadenylation sequence, a splicing control sequence, a stability promoting sequence (e.g., 5' mRNA capping sequence or a UTR) and/or other transcription promoting sequences (e.g., a Kozak consensus sequence). The nucleic acid also can include sequences that effect post-translational processes, such as transmembrane leader sequences, secretion signals, organelle specific trafficking or localization signal sequences, and sequences encoding intein- like expression. The nucleic acid can include one or more other peptide-encoding sequences, for example a reporter gene (e.g., a Green Fluorescent Protein gene, firefly luciferase gene, or β-galactosidase gene), which are preferably operably linked to the same promoter as the angiogenic sequence. Additionally or alternatively, the nucleic acid can include one or more sequences encoding peptides and/or nucleic acids that assist in the development of blood vessels or the regulation of angiogenesis. For example, the nucleic acid can encode an integrin (e.g., αvβ3 integrin and/or αvβ5 integrin), which assists in migration of new blood vessels, an enzyme which dissolves tissue in the path of the developing/migrating blood vessels (e.g., a matrix metalloproteinase (MMP)), or one or more genes which attract pericytes or other blood-vessel supporting cells to the target and source locations, as well as the area therebetween. The nucleic acid can be in any form suitable for establishing a gradient between a source location and a target location in a host. Desirably, the nucleic acid is positioned in, or administered in the form of, a vector. The vector can be any suitable vector. For example, the nucleic acid can be administered as a naked DNA or RNA vector (including, for example, a linear expression element) or as a precipitated nucleic acid vector construct (e.g., a CaPO precipitated construct). Such nucleic acid vectors can be associated with salts, carriers, or formulations which aid in transfection (e.g., sodium phosphate salts, Dextran carriers, iron oxide carriers, or gold bead carriers), and other pharmaceutically acceptable carriers described herein. Alternatively or additionally, the nucleic acid can be associated with one or more transfection- facilitating molecules such as a liposome (preferably a cationic liposome), a transfection facilitating peptide or protein-complex (e.g., a poly(ethylenimine), polylysine, or viral protein-nucleic acid complex), a virosome, a modified cell or celllike structure (e.g., a fusion cell or micelle), or a viral vector. The nucleic acid is desirably positioned in a viral vector. The viral vector can be any suitable viral vector. A viral vector in the context of the invention includes any combination of nucleotides and proteins which are derived from, obtained from, or based upon proteins and or nucleic acids that are present in a wild-type virus. The viral vector preferably consists of an intact virus particle. Typically, such viral vectors consist essentially of a wild-type viral particle, or a viral particle modified in its protein and/or nucleic acid content to aid in transfection and expression of the nucleic acid. Such vectors are typically named for the type of virus they are obtained, derived from, or based upon, as applicable. Examples of preferred viral vectors include herpes viral vectors, adeno-associated viral vectors, and adenoviral vectors. Desirably, the viral vector is capable of expressing the nucleic acid, particularly the angiogenic sequence, for a sustained period (e.g., for a period of at least about 1 day, preferably about 1 week), without expressing the nucleic acid so long that promiscuous angiogenesis occurs (e.g., for a period of less than about 2 weeks, preferably about 1 week or less). Thus, the viral vector preferably is capable of therapeutic, and transient, self-terminating expression of the nucleic acid (e.g., expression for a period of about 1 week or less). Preferably, the viral vector achieves gene transfer in both dividing and non-dividing, as well as terminally differentiated cells, with high levels of expression in cardiovascular relevant sites such as the myocardium, vascular endothelium, and skeletal muscle. The viral vector desirably is safe for administration to the host. Advantageously, the viral vector operates in an epichromosomal manner without insertion of genetic material to the host. Adenoviral vectors, which possess all of these aforementioned qualities, are particularly preferred delivery vectors for nucleic acid angiogenic mediators. The nucleic acid can be positioned in any suitable adenoviral vector. Preferably, the adenoviral vector is based on, derived from, or consists of a serotype-2 or serotype-5 adenovirus. The adenoviral vector desirably is deficient in at least one gene function required for viral replication, i.e., an essential gene function. Preferably the adenoviral vector will be deficient in at least one essential gene function of the El, E2, and/or E4 regions of the adenoviral genome. Such adenoviral vectors may further include a deletion of other portions of the adenoviral genome, for example a deletion of all or part of the E3 region (which is not essential for viral replication). Preferably, the adenoviral vector is deficient in some essential gene region of the adenoviral genome, such that the adenoviral vector is prevented from replicating in the absence of a complementary cell line. For example, DNA encoding an angiogenic peptide can be inserted into at least a portion of the El region of an adenovirus genome, which is required for adenoviral replication. Thus, it is preferred that the adenoviral vector is deficient in at least some portion of the El region (e.g., the El a region and/or Elb region), alone or in combination with deficiencies of essential gene functions of other adenoviral genome regions. Examples of El -deleted and other replication deficient adenoviral vectors are disclosed in, for example, U.S. Patent 5,851,806 and International Patent Application WO 95/34671. Examples of replication deficient adenoviral vectors include adenoviral vectors having a partial deletion of the El a region, at least a partial deletion of the Elb region, and at least a partial deletion of the E3 region, of the adenoviral genome. Other examples of replication deficient adenoviral vectors include adenoviral vectors having a deletion of the entire El region, at least a partial deletion of the E3 region, and at least a partial deletion of the E4 region. The adenoviral vector desirably retains at least one adenovirus inverted terminal repeat (ITR) (preferably the 5' and 3' ITRs). The adenoviral vector also desirably retains the adenovirus packaging sequence. A particularly preferred adenoviral vector for use in the inventive method is deficient in the entire El a region, at least part of the El b region, and at least part of the E3 region of the adenoviral genome and contains the DNA encoding human or human VEGF 165 under the control of the CMV IE promoter in the El region of the adenoviral genome. Such a vector supports in vivo expression of VEGF that is maximized at one day following administration and is not detectable above baseline levels as little as one week after administration. This is ideal inasmuch as it is sufficient to provide substantial growth of new vasculature while minimizing adverse neovascularization at distal sites. In that regard, when this vector is locally administered to a target tissue, no detectable VEGF expression can be detected in blood serum using standard ELISA monitoring assays. Advantageously, local administration to a target tissue of such adenoviral vectors including a nucleic acid encoding human VEGF 12 ι or VEGFj 65 positioned in the El region of the adenoviral genome are able to increase blood flow at least 3-fold in the extremities of mammals (e.g., the hind limb of Sprague-Dawley rats) with iliac and femoral artery ligations. The adenoviral vector can be subject to any number of additional or alternative modifications. For example, the adenoviral vector's coat protein can be modified so as to incorporate a specific protein binding sequence, as described in U.S. Patent 5,432,075, or the viral vector's coat protein can be modified so as to decrease the potential for immunological recognition by the host and resultant coat-protein directed neutralizing antibody production, as described in, e.g., International Patent Application WO 98/40509. The nucleic acid can be positioned within any suitable location in the genome of the adenoviral vector. Typically, the nucleic acid will substitute one or more of the aforementioned deleted regions of the adenoviral genome (e.g., the El, E2, E3, and/or E4 region, most preferably replacing at least a portion of the El region). Alternatively, several nucleic acids encoding angiogenic peptides can be inserted as expression cassettes into multiple deleted regions (e.g., a first angiogenic sequence can be inserted in a portion of the El region and a second angiogenic sequence can be inserted in the deleted E3 region). The nucleic acid encoding the angiogenic peptide is inserted in the vector in any suitable manner and in any suitable orientation. Whereas the nucleic acid can be inserted in any suitable orientation, preferably the orientation of the nucleic acid is from right to left. By the nucleic acid having an orientation from right to left, it is meant that the direction of transcription of the nucleic acid is opposite that of the region of the vector into which the nucleic acid is inserted. The invention involves establishing a gradient of an angiogenic mediator of increasing concentration from a source location in the host to a target location in the host, such that blood vessel growth is directed from at least one source location to at least one target location, and the level of perfusion of blood to the target location in the host is enhanced. Any suitable means of administering the angiogenic mediator to the host that creates a gradient of increasing concentration from the source location to the target location can be used within the context of the invention. Preferably the angiogenic mediator is administered by direct administration (e.g., injecting or topically administering) the angiogenic mediator into or near the source and/or target locations. Other delivery techniques, such as electroporation, also can be utilized. By the term "injecting," it is meant that the angiogenic mediator is forcefully introduced into the target tissue. For example, the angiogenic mediator may be microinjected, injected directly by a needle, or injected by biolistic injection. The angiogenic mediator to be injected can be any suitable angiogenic mediator conducive to such administration, including vectors containing nucleic acid angiogenic mediators such as the adenoviral vectors described herein. Any suitable injection device can be used within the context of the invention. For example, in the context of direct injection of an angiogenic mediator that comprises an adenoviral vector comprising a DNA encoding an angiogenic substance, a suitable injection device that is capable of delivering simultaneous multiple injections is described in U.S. Patent 5,846,225. Other suitable injection devices which can be used within the context of the invention include minimally invasive injection devices. Such devices are capable of accessing a tissue (e.g., the heart) through small incisions of less than about 15 cm and are designed to provide injections through a single lumen, in contrast to the multiple injection devices described above To allow for the need for multiple injections with a specific geometry, a marking system can be employed so that the sites of previous injections are well delineated. Minimally invasive injection devices can comprise injector tips which are flexible and steerable to allow access via small incisions to the curved outer surface of the heart, for example, which exists at varying angles with respect to the limited aperture window required with minimally invasive surgeries. Suitable minimally invasive injection devices also are described in International Patent Application WO 99/44656. Administration of the angiogenic mediator to the source and/or target locations can be accomplished either in vivo or ex vivo. Therefore, for example, the tissue of interest can be removed from the recipient of the present inventive method, can be treated with the angiogenic substance, and then can be re-implanted into the recipient. Ex vivo administration of the angiogenic mediator to the tissue of interest also helps to minimize undesirable induction of angiogenesis in non-targeted tissue. A specific example of such a technique is the administration of the angiogenic mediator in a gradient forming fashion to a tissue flap in surgical procedures involving replacement and/or transfer of tissue flaps (e.g., in breast reconstruction). The gradient in such procedures can be formed by any suitable technique. For example, different amounts of the angiogenic mediator can be administered to different portions of a removed tissue (e.g., by soaking the tissue in a solution of an angiogenic mediator for different periods of time). Alternatively, the host can be administered two or more tissues or cell/tissue associated structures containing angiogenic mediators or vectors expressing angiogenic peptides which are re-implanted in the host in a gradient producing manner (e.g., by administering transfected cells expressing angiogenic peptides in a gradient forming administration pattern, e.g., by transfected-cell coated stents). The invention desirably is performed by multiple administrations (i.e., at least two administrations) of the angiogenic mediator to multiple (i.e., at least two) locations in the host, where each administration is of a relatively uniform volume of a composition having a relatively uniform concentration of an angiogenic mediator therein, but the administrations vary in number at different distances from the target location. The multiple administrations can comprise 2, 3, 4, 5, or more administrations (i.e., applications), preferably 5 or more administrations, more preferably 8 or more administrations, and most preferably at least 10 (e.g., 10, 15, 20, 25, or 30 or more) administrations. By varying the number and spacing of such administrations, a suitable gradient from the source location to the target location can be established. The specific pattern of the at least two administrations can be any suitable pattern, incorporating any suitable number of administrations. For example, an injection of an angiogenic mediator at a relatively lower concentration at or near the source location and another injection of a relatively higher concentration at or near the target location can be used to produce the gradient. Similarly, application of a relatively greater volume of a composition comprising an angiogenic mediator at a uniform concentration at or near the source location and a similar application of a lesser volume of the composition at or near the target location also can generate a suitable gradient. Thus, with respect to the use of an adenoviral vector comprising a DNA encoding an angiogenic peptide, for example, the method can comprise administering different amounts of the adenoviral vector at a uniform concentration by modifying the number of applications of the adenoviral vector to the host. More particularly, such an embodiment of the invention comprises administering fewer applications (or doses) of the adenoviral vector at or near the source location than at or near the target location to produce a gradient. The angiogenic mediator can alternatively or additionally be administered to any suitable surface, either internal or external, at or near the source and/or target locations. For example, with respect to directly injecting an angiogenic mediator into cardiac tissue, it is contemplated that such an injection can be administered from any suitable surface of the heart (i.e., the angiogenic mediator can be administered endocardially and/or epicardially). Typically and preferably, cardiac administration will be to the left free ventricular wall of the heart which is easily accessible by minimally invasive thoracotomy. Alternatively, administration to other areas of the heart (e.g., the septum and/or right ventricle) can be accomplished by use of a capillary tube or other suitable device. Such alternate techniques may be desired where the target location is positioned in the heart but away from the left free ventricular wall (e.g., where the target location is a vascular occlusion in the right coronary artery). Multiple administrations of the angiogenic mediator provide an advantage over single administration in that total administration can be manipulated by such parameters as a specific geometry defined by the source and/or target locations, as well as the area therebetween, where each application is administered. By manipulating both the specific geometry and the time differentials of the multiple applications, the induction of angiogenesis in non-targeted tissue can be minimized, while desirably causing angiogenesis to the target location. For example, the specific geometry is preferably manipulated such that angiogenesis is induced only in the tissue which require it (i.e., the target location or target tissue) and minimized in other locations. The specific geometry of the multiple applications is defined by the locations where each application of the angiogenic mediator is administered. The multiple applications can define any suitable pattern or specific geometry. For example, in two- dimensional space, the multiple applications can define a square, whereas in three- dimensional space the multiple applications can define a cube. The multiple applications preferably are spaced such that the points of application are separated by less than about 4 cm (e.g., about 0.5-4 cm), more preferably less than about 3 cm (e.g., about 1-3 cm), and most preferably less than about 2 cm (e.g., about 1-2 cm). Spacing may vary within such ranges as necessary to produce a suitable gradient. With respect to the specific geometry of the multiple applications in two- dimensional space, the specific geometry is defined by a plane (i.e., a cross-section of the target tissue) in which the multiple applications lie. The plane defined by the multiple applications can lie at a constant distance from the surface of source and/or target locations (i.e., substantially parallel to the surface of the source and/or target locations), the depth of the plane, or, alternatively, the plane can lie at an angle with respect to the surface of the target and/or source locations. Preferably, a single application will be administered for about every 0.5-15 cm 2 of the plane, more preferably for about every 1-12 cm 2 of the plane, and most preferably for about every 1.5-7 cm 2 of the plane. The depth of the plane is preferably about 1-10 mm, more preferably about 2-7 mm, and most preferably about 3-5 mm. The plane depths typically correspond to the distance from the surface of the tissue to which the angiogenic is administered, to the plane of administration within the tissue (e.g., the depth in the heart which an angiogenic mediator is administered by needle injection). In three-dimensional space, the multiple administrations are preferably administered within an area of about 50 cm 3 (e.g., about 0.5-50 cm 3 ), more preferably within an area of about 35 cm 3 (e.g., about 1-35 cm ), and most preferably within an area of about 15 cm 3 (e.g., about 0.5-15 cm 3 or even about 3-15 cm 3 ). Preferably, the multiple administrations, and the source locations, are within about 50 cπi*, more preferably within about 35 cm 3 , and most preferably within about 15 cm 3 of the target location. Another parameter of the multiple applications which can be manipulated is the time differential between each application. Preferably, each of the multiple applications is administered within about 10 minutes (e.g., about 0.5-10 minutes) of each other, more preferably within about 8 minutes (e.g., about 0.5-8 minutes) of each other, and even more preferably within about 6 minutes (e.g., about 1-6 minutes) of each other. Most preferably, all of the multiple applications of the single dose are administered within the aforementioned time frames. Optimally, each of the multiple applications is administered substantially simultaneously. When administering the angiogenic mediator, it is desirable that the administration is such that the angiogenic mediator is able to contact a region reasonably adjacent to the source and/or target locations, as well as the area therebetween. It is not believed to be necessary to have the angiogenic mediator actually contact the precise sites of the source and the terminus for collateral blood vessel formation. Preferably, the specific geometry of the multiple applications be defined to allow the angiogenic mediator to contact or reach a region including the source of collateral blood vessel formation, the terminus of collateral blood vessel formation, and the area therebetween. Preferably, most, if not all, of the angiogenic mediator is administered in close proximity to the target location. Preferably, the angiogenic mediator can be administered less than about 5 cm from the target location, more preferably less than about 4 cm from the target location, more preferably less than about 3 cm from the target location, and, optimally, about 1-2 cm from the target location. One or more of such administrations can be to or in the target location. For example, where the target location is within an ischemic tissue the method can be limited to administration only within the ischemic tissue. Where the target location is a blood vessel or a portion thereof, the angiogenic mediator preferably is administered in a distribution surrounding the diameter of the blood vessel or a portion thereof (e.g., the side nearest the source location). The angiogenic mediator desirably is administered to the host in a pharmaceutically acceptable carrier. Any suitable pharmaceutically acceptable carrier can be used within the context of the invention. The choice of carrier will be determined, in part, by the particular site to which the composition is to be administered and the particular method used to administer the composition. Various examples of suitable pharmaceutical carriers are described in, for example, Urquhart et al., Lancet, 16, 367 (1980), Lieberman et al., Pharmaceutical Dosage Forms - Disperse Systems (2nd ed., vol. 3 1998), Ansel et al., Pharmaceutical Dosage Forms & Drug Delivery Systems (7th ed. 2000), and U.S. Patent 5,994,106. Pharmaceutically acceptable carriers in connection with adenoviral vectors comprising a nucleic acid encoding an angiogenic peptide are described in, for example, International Patent Application WO 98/32859. The gradient can be any gradient of increasing concentration from the source location to the target location that promotes the growth of blood vessels from the source location to the target location. The specific gradient required for increasing the amount of blood vessel growth to the target will depend on the host, the specific target and source locations used, and the angiogenic mediator to be administered. Effective gradients for a particular angiogenic mediator, particular host, and particular source and target locations, can be identified by any suitable technique. A simple technique for identifying effective gradients comprises administering the angiogenic mediator in a gradient of increasing concentration from a source location to a target location and testing for the development of new or increased blood vessel growth between the source and target locations, or for a therapeutic angiogenic effect in a host suffering from ischemic conditions near or at the target location. Several tests to determine directed blood vessel growth are known, as well as tests for identifying characteristics associated with angiogenesis in ischemic or otherwise damaged tissue. Examples of such tests include exercise tolerance tests, magnetic resonance imaging (MRI) testing for local perfusion, rest and stress (adenosine) 99m Tc-sestamibi SPECT tests, rest and stress (dobutamine) echocardiograms, and angiography tests. The gradient can comprise a gradient in or about a single plane of administration, in multiple planes of administration, or in three dimensions. For example, the angiogenic mediator can be administered by injection in a tissue at an equal depth in a tissue but at two or more locations in the horizontal plane at the depth such that a gradient within the particular plane of injection is established. Preferably, the gradient is established in every dimension where blood vessel growth can be reasonably directed from source locations. When blood vessel growth can be accomplished from numerous locations, a three dimensional gradient of increasing concentration towards the target location may be used, by administering the angiogenic mediator such that a gradient is established in all directions from several source locations to the target location. The gradient is established between at least one source location and at least one target location. The target and source locations can be any suitable locations in a host that permit or promote blood vessel growth towards the target location when a gradient of angiogenic mediator is established between the source and target locations. Typically and preferably, the target and source locations comprise tissues, are portions of a single tissue, or are portions of separate but interconnected tissues (e.g., different positions or portions of a single organ system such as different blood vessels). Preferably, the target and source locations comprise receptors capable of binding the angiogenic mediator (e.g., any of the aforementioned growth factor receptors). For example, when the angiogenic mediator is a nucleic acid encoding a VEGF, the tissue preferably contains endothelial cells which include VEGF receptors. Desirably, both the source and target tissues comprise endothelial cells, which are susceptible to specific angiogenic mediators or angiogenic gene products described herein. Generally, the source and/or target locations will comprise tissue that is a part of, or forms, a discrete organ, e.g., a muscle, such as the heart. The source location preferably is an angiogenically functional location, i.e., a location in the host that has a sufficient level of perfusion of blood, such as an area near or imbued with existing blood vessels (e.g., a non-ischemic area, preferably with a significant amount of existing blood vessels, more preferably an area containing a physiologically normal (healthy) amount of blood vessels for the particular tissue in the host). The target location preferably is an actual or potentially angiogenically dysfunctional location, e.g., a location in the host that is either undergoing or is at risk of undergoing ischemia or any other condition wherein the growth of new, or extension of existing, blood vessels is desirable. Typically, the target location (particularly an angiogenically dysfunctional location) will be suffering from or be at risk of suffering from ischemic damage, which results when the tissue is deprived of an adequate supply of oxygenated blood. The interruption of the supply of oxygenated blood is often caused by a vascular occlusion. Such vascular occlusion can be caused by arteriosclerosis, trauma, surgical procedures, disease, and/or other indications. There are many ways to determine if a tissue is at risk of suffering ischemic damage from undesirable vascular occlusion. Such methods are well known to physicians who treat such conditions. For example, in myocardial disease these methods include a variety of imaging techniques (e.g., radiotracer methodologies such as 99m Tc-sestamibi scanning, x-ray, and MRI scanning) and other physiological tests. Therefore, induction of angiogenesis in tissue affected by or at risk of being affected by a vascular occlusion is an effective means of preventing and/or attenuating ischemia in such tissue. As a result, although any suitable tissue can be targeted for the induction of angiogenesis, the target tissue is preferably one that is affected by or at risk of being affected by a vascular occlusion. The target location may also comprise a tissue in which blood flow is attenuated by trauma, surgery, or other events. The alleviation of such attenuated blood supply, regardless of its origin, is contemplated by the invention. Thus, prevention or alleviation of damage from indications such as myocardial ischemia (particularly in patients suffering from insulin dependent diabetes), delayed wound healing, Buerger's disease, and stroke are contemplated. Additionally, the planning of a surgical procedure can be predictive of the interruption of blood supply through a particular portion of a patient' s vasculature. Prior treatment according to the present method can substantially improve the desired outcome of these surgeries. In that case, treatment preferably occurs about one day to about six weeks before the surgery, and more preferably about two to about fourteen days prior to surgery. The target and source locations can be in any suitable tissue susceptible to administration of the angiogenic mediator. For example, the target and source locations can be located in a discrete organ such as the brain, heart, pancreas, limbs, or generalized areas of the body, such as a leg or a foot. Preferably, the target location and source location comprise portions of an organ system that includes at least two arteries (e.g., a heart which comprises at least three major arteries). In such aspects, the target location typically comprises at least a portion of an angiogenically dysfunctional artery in the system (e.g., an artery suffering from vascular occlusion), and some, if not all, of the angiogenically functional arteries in the system serve as source locations. In such aspects, the angiogenic mediator preferably is administered in a distribution between the target artery and the source arteries. Where the target location is an artery suffering from vascular occlusion, the method can comprise administration of the angiogenic mediator upstream, downstream, or to the occluded region of the artery (i.e., with respect to normal blood flow), or any combination thereof, as desired, preferably such that induced collateral blood vessel development bypasses the occluded region. The method of the invention can be practiced, and is useful, in a variety of contexts and can be applied to any suitable host. Preferably, the host is a mammalian host, more preferably the host is a human host, and optimally the host is a human host suffering from either, or at risk of suffering from, ischemic conditions, and/or vascular occlusion in the target location. The desired dosage (i.e., total dosage to the host) of the angiogenic mediator is such that blood vessel growth is promoted from the source location to the target location and angiogenesis is induced in the target location, e.g., such that there is a therapeutic and/or prophylactic effect on target location. Desirably, the dosage of the angiogenic mediator is such that induction of angiogenesis in non-targeted tissue is minimized, and that the generation of disorganized vasculature beds, loss of function in the affected tissue, and promiscuous angiogenesis are avoided. The dosage also will vary depending upon the angiogenic mediator to be administered, the host, the source and target locations, and possibly the desired effect (e.g., directed blood vessel growth to bypass a vascular occlusion, induction of blood vessel growth, or maturation of blood vessels). Such dosage determinations can be made using routine experimentation and calculation and by examining the known effects of the angiogenic mediator to be administered. Generalized guidance in making such determinations can be found, for example, in Platt, Clin. Lab Med., 7, 289-99 (1987), and in "Drug Dosage," J. Kans. Med. Soc, 70(1), 30-32 (1969). Dosage is described herein with respect to adenoviral vectors containing nucleic acids encoding angiogenic peptides as an illustration of suitable dosage. It should be understood that the description of such dosages as is intended to illustrate this aspect of the invention, and does not limit the scope at the invention. The dosage of an adenoviral vector containing an angiogenic gene will vary depending upon the particular vector and the angiogenic peptide encoded by the nucleic acid positioned in the vector. A dose of an adenoviral vector containing a nucleic acid encoding an angiogenic gene typically will be at least about lxl 0 6 pfu (e.g., lxlO 6 - lxlO 13 pfu) to the target tissue, e.g., a discrete organ, such as a human heart. The dose preferably is at least about lxlO 7 pfu (e.g., about lxlO 7 - lxlO 13 pfu), more preferably at least about lxlO 8 pfu (e.g., about lxlO 8 - lxlO 11 pfu), and most preferably at least about lxlO 9 pfu (e.g., about Ixl0 9 -lxl0 10 pfu). The dose typically is for a volume of targeted tissue of about 0.5-15 cm 3 , but can be for larger tissue volumes of up to 100 cm 3 or even about 150 cm 3 . The dose desirably is administered via multiple applications, and, as such, is divided among the multiple applications. Thus, if the dose is administered via 10 administrations, each administration involves about lxlO 5 - lxlO 12 pfu. Preferably, each application involves about lxlO 6 - lxlO 12 pfu, more preferably about lxlO 7 - lxlO 10 pfu, and most preferably about lxlO 8 - lxlO 9 pfu. For purposes of considering the dose in terms of particle units (pu), also referred to as viral particles, it can be assumed that there are 100 particles/pfu (e.g., lxlO 12 pfu is equivalent to lxlO 14 pu). In a single round of vector administration, using, for example, an adenoviral vector deleted of the entire El a region, part of the Elb region, and part of the E3 region of the adenoviral genome, wherein the vector comprises a nucleic acid encoding human VEGF !21 or VEGF )65 under the control of a standard CMV immediate early promoter, about 10 7 -10 13 pfu, preferably about 10 9 -10 n pfu, are administered to the host (e.g., to a discrete organ containing the source and/or target locations) with an estimated volume of about 150 cm 3 . Under these conditions, a substantial level of VEGF production is achieved in the tissue of interest without producing detectable levels of VEGF production in distal tissues. EXAMPLE This example demonstrates the increased therapeutic angiogenic effects obtained by practicing the method of the invention over other forms of administering angiogenic mediators. While the example further illustrates the invention it should not be construed as in any way limiting its scope. Sixteen individuals (age 60 +/- 1 1 years; 1 1 male, 5 female) with severe coronary disease were tested for exercise tolerance using a standardized treadmill exercise tolerance test. Patients were administered via minimally invasive surgery, Ad u VEGF 121.10, a recombinant adenoviral vector containing a nucleic acid encoding the angiogenic mediator VEGFj 2 ι . Individuals in a first group (n=6) were administered ten 0.1 ml aliquots of a pharmaceutically acceptable solution containing a total of 4 x 10 particle units of Ad C uVEGF121.10. The 10 aliquots were administered to different points along the length of (i.e., for about 4 cm), and less than about 5 cm from, a single target coronary artery (either the left anterior descending (LAD), circumflex (Circ), or (R) artery, as applicable), suffering from poor blood perfusion, such that upon expression of the vector, the VEGF 12 ι formed an increasing concentration gradient between the other cardiac arteries and the target location coronary artery. A second group (n=5) of individuals were administered twenty 0.1 ml aliquots of the same pharmaceutically acceptable solution containing a total dosage of 4 x 10 10 particle units of Ad C u VEGF 121.10 at multiple locations surrounding two coronary arteries in a diffuse fashion, such that a reduced concentration gradient was established from the source tissues to the target coronary artery. A third group (n=5) of individuals received thirty 0.1 ml aliquots of the same pharmaceutically acceptable solution containing a total dosage of 4 x 10 10 particle units of Ad C u VEGF 121.10 around all three coronary arteries in a diffuse fashion, such that no concentration gradient was established between healthy source arteries and the damaged target artery. The individuals were assessed at 30 days and 180 days post-treatment by exercise tolerance testing using tolerance to identical treadmill activity. Results of the exercise tolerance tests conducted at 30 and 180 days post- treatment were compared with exercise tolerance levels recorded prior to treatment. Exercise tolerance for individuals who received Ad C uVEGF121.10 in a gradient-forming single coronary artery distribution were further tested at 360 days post-treatment. The change in exercise tolerance at 30, 180, and 360 days post-treatment compared to pre-treatment was determined, and the averages for each group at each time were calculated. The number of individuals in each group showing an improvement in exercise tolerance is presented in Table 1. The average change in exercise tolerance at each of the aforementioned test times for each group is presented in Table 2. Table 1 - Percentage of Individuals Exhibiting Improvement in Exercise Tolerance after Treatment with Ad cu VEGF121.10 at Different Concentration Gradients Table 2 - Average Change in Exercise Tolerance after Treatment with Ad C υVEGFl21.10 at Different Concentration Gradients The results of these experiments, as recited in Tables 1 and 2, demonstrate that a greater number of individuals with severe coronary disease exhibited improved exercise tolerance when administered Ad C u VEGF 121.10 vector in a gradient-forming distribution about a single target artery. In contrast, individuals receiving the Ad C u EGF121.10 vector in more diffuse and non-gradient-forming double or triple coronary artery distributions did not show as significant an improvement in post- treatment exercise tolerance as individuals. Furthermore, the results demonstrate that individuals receiving the Ad C uVEGF121.10 vector in a gradient forming manner exhibited greater increases in exercise tolerance post-treatment than individuals receiving the vector in a more diffuse administration pattern. The results of the above-described experiments indicate that the method of the invention can direct blood vessel growth from one or more locations to a target location by establishing a gradient of an angiogenic mediator of increasing concentration from the source location to a target location. All references, including publications, patent applications and patents, cited herein are hereby incorporated by reference to the same extent as if each reference were individually and specifically indicated to be incorporated by reference and were set forth in its entirety herein. The use of the terms "a" and "an" and "the" and similar referents in the context of describing the invention (especially in the context of the following claims) are to be construed to cover both the singular and the plural, unless otherwise indicated herein or clearly contradicted by context. The use of the terms "including," "having," "comprising," "containing," and similar terms are to be construed as open-ended terms (i.e., meaning "including, but not limited to") and encompassing the terms "consisting of and "consisting essentially of unless otherwise indicated." Recitation of ranges of values herein are merely intended to serve as a shorthand method of referring individually to each separate value falling within the range, unless otherwise indicated herein, and each separate value is incorporated into the specification as if it were individually recited herein. The use of any examples or exemplary language (e.g., "such as") herein, is intended merely to better illustrate the invention and is not intended as a limitation on the scope of the invention. No language in the specification should be construed as indicating any non- claimed element as essential to the practice of the invention. The foregoing is an integrated description of the invention as a whole, not merely of any particular element or facet thereof. The description describes "preferred embodiments" of this invention, including the best mode known to the inventors for carrying it out. Upon reading the foregoing description, variations of those preferred embodiments may become apparent to those of ordinary skill in the art. The inventors expect skilled artisans to employ such variations as appropriate, and the inventors intend the invention to be practiced otherwise than as specifically described herein. Accordingly, this invention includes all modifications and equivalents of the subject matter recited in the claims appended hereto as permitted by applicable law. Moreover, any combination of the above-described elements in all possible variations thereof is possible unless otherwise indicated herein or otherwise clearly contradicted by context.

Claims: WHAT IS CLAIMED IS: 1. A method of directing blood vessel growth comprising administering an angiogenic mediator to at least two different locations in a host such that a gradient of angiogenic mediator of increasing concentration from an angiogenically functional source location to a potentially or actual angiogenically dysfunctional target location is established, whereby blood vessel growth is directed from the source location to the target location. 2. The method of claim 1 , wherein the target location is an ischemic tissue. 3. The method of claim 1 or claim 2, wherein the angiogenic mediator comprises a nucleic acid encoding an angiogenic peptide. 4. The method of claim 3, wherein the nucleic acid encoding an angiogenic peptide is positioned within an adenoviral vector. 5. The method of claim 4, wherein the adenoviral vector is deficient in at least one essential gene function of the El region of the adenoviral genome, at least one part of the E3 region of the adenoviral genome, or both. 6. The method of claim 5 wherein the adenoviral vector is further deficient in at least one essential gene function of the E4 region of the adenoviral genome. 7. The method of any of claims 4-6, wherein the nucleic acid encoding an angiogenic peptide is oriented from right to left in the genome of the adenoviral vector. 8. The method of any of claims 3-7, wherein the nucleic acid further encodes an angiogenic peptide receptor. 9. The method of any of claims 3-8, wherein the nucleic acid encodes at least two angiogenic peptides. 10. The method of claim 9, wherein the at least two angiogenic peptides have a synergistic effect when expressed in the host. 11. The method of any of claims 9 or 10, wherein one of the at least two angiogenic peptides is a VEGF. 12. The method of any of claims 1-1 1, wherein the host is a human. 13. The method of any of claims 1-12, wherein the angiogenic mediator is administered in different amounts to the at least two different locations. 14. The method of any of claims 1-13, wherein the at least two locations are less than about 5 cm from the target location. 15. The method of any of claims 1-14, wherein the at least two locations are separated by a distance of less than about 5 cm. 16. The method of any of claims 1-15, wherein the angiogenic mediator is administered to the at least two locations less than about 10 minutes apart. 17. The method of any of claims 1-16, wherein the angiogenic mediator is administered to the at least two locations simultaneously. 18. The method of any of claims 1-17, wherein the angiogenic mediator is administered to an organ system, the target location is an angiogenically dysfunctional artery in the organ system, and the source location is an angiogenically functional artery in the organ system. 19. The method of any of claims 1-18, wherein the target location is part of the host's heart. 20. The method of any of claims 1-19, wherein the target location is an artery suffering from vascular occlusion and the at least two locations include at least one location upstream of the vascular occlusion and at least one location downstream of the vascular occlusion.

Inventors: CRYSTAL RONALD G, ROSENGART TODD K, CRYSTAL, RONALD, G., ROSENGART, TODD, K.
Applicants: CORNELL RES FOUNDATION INC, CRYSTAL RONALD G, ROSENGART TODD K, CORNELL RESEARCH FOUNDATION, INC., CRYSTAL, RONALD, G., ROSENGART, TODD, K.
Application year: 2000
Main classification: A61K38
IPC codes: A61K38, A61K45, A61K48, A61P9, C12N15