GENETICALLY-MODIFIED MYOGENIC PROGENITORS AND THEIR USE IN CELL AND GENE THERAPY

Abstract: The present invention has as an object engineered myogenic progenitors derived from bone marrow, useful in muscular dystrophy gene therapy.

Description: GENETICALLY-MODIFIED MYOGENIC PROGENITORS AND THEIR USE IN CELL AND GENE THERAPY. The object of the present invention are engineered myogenic progenitors derived from bone marrow, useful in muscular dystrophy gene therapy. Muscular- dystrophies are a heterogeneous set of severe muscle degenerative diseases due to mutations in genes encoding a membrane associated protein, dystrophin or other members of the dystrophin-associated protein complex, linking the muscle fiber cytoskeleton to the extracellular matrix. Therapies for these severe syndromes, having a long course and characterized by high social costs, are currently not available. Gene therapy of muscular dystrophies, i.e. administration of a functional copy of the mutated gene to a significant fraction of the skeletal and cardiac muscle tissue, represents a formidable scientific and medical task. Nevertheless it could result in a definitive, although only partially effective, therapy with significant medical and economical benefits. The clinical application of gene therapy to dystrophy is currently restricted by a variety of problems comprising immunogenicity of viral vectors, poor survival of transplanted cells, and the ability of the transplanted myoblasts to differentiate. Difficulty in developing an effective administration route for both vectors and genetically-modified cells is the most remarkable problem of both in vivo and ex-vivo approaches. Myoblast transplantation from histocompatible donors has currently produced only modest and discouraging results (Nature Med. 3, 970-977, 1997). Studies conducted in the the mdx mouse, the Duchenne muscular dystrophy animal model, demonstrated that the dystrophic phenotype can be corrected by introducing a sequence encoding dystrophin or a dystrophin- related protein, utrophin (Nature 364. 725-729, 1993) into germinal cell lines. In pre-clinical models, administration of dystrophin utrophin genes to mdx mouse muscle was obtained by viral or non viral vector injection. Application of such a technology to humans is currently restricted by the low efficiency of gene transfer and immunological problems (Nature Med. 3(3). 278-279, 1997; Br. Med. Bull. 51 , 123-137, 1995). The alternate approach is based on ex-vivo transplantation of genetically-modified myoblast, assuming that myogenic cells engineered to express dystrophyn would be able to participate in muscle regeneration and provide enough protein such to allow normal or nearly normal functioning of the regenerated fibers. The evidence that genetically-corrected cells could reverse clinical phenotype in humans, results from the observations of genetic normalization in muscle fibers from women afflicted with Duchenne dystrophy with chromosome X inactivation (Neurology 45, 677-690, 1995). In the mdx mouse, genetically-corrected myoblasts apparently correct abnormal phenotype (Hum. Gene Ther. 5, 165-1994). Although the general concept that human myoblasts can be transduced and permanently express a transgene upon fusion in a regenerating muscle has been proven in an immunodefϊcient mouse model, such evidence is not yet available in human muscle (Hum. Gene Ther. 4, 713-723, 1993; 5, 949-958, 1994). However, the poor recovery of satellite cells from dystrophic muscle biopsies, difficulty in developing an effective administration route, a low survival and ability to differentiate of injected fibroblast, currently represent severe limitations to the clinical application of the ex-vivo approach. Finally, it was reported that dystrophin expression generates humoral and/or cellular immune responses in dystrophin-deficient patients (New Eng. J. Med. 333, 732-733, 1995) and mice (J. Cell Biol. 131. 975-988, 1995). From the above, we can see that engineering a cell population, transplanting and then systemically delivering it to a large number of muscles can provide substantial progress in the development of cell-mediated replacement therapy. Brief summary of the invention The present invention is based on the discovery of the existence of circulating myogenic precursor, derived from bone marrow, which are able to migrate into degenerated muscle, undergo myogenic differentiation, and participate in the regeneration of damaged fibers. Therefore, in a first embodiment, the invention provides bone marrow cells, engineered to express dystrophin or related proteins (utrophin, adalin, etc.). Such cells can be transplanted into patients affected with muscular dystrophy according to the well known methods for bone marrow transplantation. Detailed description of the invention Bone marrow cells are obtained by standard methods from healthy human donors or from dystrophic patients afflicted with muscular dystrophy. In particular, cells are collected by leukapheresis upon separation from erythrocytes and neutrophils by Ficol-Hypaque density gradient centrifugation. Obtained cells are thus washed and cultivated in DMEM medium supplemented with 5% foetal calf serum or human serum in the presence of recombinant human growth factors. The introduction into such cells of corrected genes, encoding dystrophyn and associated protein or their functionally equivalent variants or derivatives, can be made by employing retroviral vectors or other conventional transduction or transfection methods, for example employing adenovirus vectors, adeno- associated virus vectors or transfected or electroporated DNA. It is particularly preferred the use of gene transfer with retroviral vectors as described in Progress in Nucleic Acid Research and Molecular Biology, 38:91-135 (1990). For this purpose, cell lines able to generate viral particles are used. Such cells can be obtained, for example by introducing plasmids encoding structural retroviral genes into cell lines from otherwise untransformed tissue, with calcium phosphate-based methods. The derived cell lines, known as "packaging" cell lines, can be used to transduce bone marrow cells by co-cultivation. Alternatively, other methods to introduce dystrophin, or associated protein, coding DNA, can be employed. Such methods rely on using vectors derived from adenoviruses, adeno-associated viruses, human papilloma virus, herpes and SV40 viruses. It is also possible to use the calcium phosphate transfection method or DEAE-dextran, electroporation, or any other non viral DNA delivery procedure. Dystrophin or associated proteinse encoding DNA, such as those described, in WO 97/22696, US 5 449 616, WO 93/17031 , can be introduced in the form of viral DNA, bacterial plasmids or episomes. The gene will be inserted into appropriate restriction sites of the employed plasmids. The existence of myogenic precursors derived from bone marrow was demonstrated by transplanting deficient mice scid/bg with genetically marked bone marrow obtained from a transgenic mouse cell line with a nlslacZ gene under the control of the muscle specific MLC3F promoter. When muscle regeneration in transplanted animals was induced following cardiotoxine damage, lacZ-positive nuclei embedded in the regenerated fibers were found. These data indicate that bone marrow-derived cells can migrate into areas of muscle degeneration, undergoing myogenic differentiation and participating in regeneration of damaged fibers. The c57/nlacZ strain was obtained by crossing the MLC3F- nlacZ-E transgenic line, described in J. Cell. Biol. 129, 383 (1995) with C57BL/6 inbred mice, followed by 3 generation of back-crossing to the C57BL/6 strain. The skinned tail sections were X-gal stained following segregation of the transgene. Bone marrow was obtained by flushing femurs of 4-X, to-7-week-old C57/MlacZ mice and injected (10^ cells/25 μl of PBS) into regenerating muscles of scid/bg mice, 24 hours after cardiotoxin injection. Mesenchymal stem cells able to undergo myogenic differentiation were described in WO 96/39035 (12/12/1996), WO 96/23059 (01/08/1996), US 5 591 625 (07/01/1997), and US 5 486 359 (23/01/1996). Particularly US 5 591 625 describes mesenchymal stem cells transduced with genes encoding a number of proteins of therapeutic interest such as adhesion proteins, cytokines, detoxifying enzymes, and proteins involved in tissue repair. On the other hand WO 96/39035 describes compositions comprising a muscle cell precursor and mesenchymal stem cell mix and the use of such compositions in muscular dystrophy treatment. Furthermore the use of a myoinductive agent such as 5- azacytidina or 5-azadeoxycytidine is described. It is evident as such approach substantially differs from that of the present invention. The latter allows transplantation of appropriately engineered bone marrow cells, preferably autologous, according to well defined procedures. Conversely, the above mentioned patent and those patent applications requiring injection of mesenchymal stem cells directly into the muscle are limiting with respect to therapeutic possibilities for muscle dystrophic forms. Allogenic or autologous bone marrow transplant procedures are well known and described for example in Ann. Intern. Med. 104, 105, 1987 and Curr. Opin. Hematol. 1, 221 , 1993 and also in Science 276, 1719-1724, 13/6/1997. In particular, transduced cells are resuspended after appropriate washing in saline solution containing 4% human albumin and re-infused into the patient at dosages ranging from 1x10 5 to 1x10 7 cells. The following examples describe the invention in further detail. Example 1 To investigate if bone marrow cells were able to undergo myogenesis under physiological stimuli, muscle degeneration was chemically induced into the tibialis anterior of ten immunodeficient, scid/bg mice injected with unfractionated bone marrow cells (10 6 cells/muscle) obtained from the C57/MlacZ transgenic mouse line, in which a lacZ gene coding a β- galactosidase with nuclear localization is under the control of the muscle-specific myosin 3F light chain promoter. The expression of this transgene is restricted to cardiac and skeletal muscle of the adult mouse, although it can be activated in other cell types upon induction of myogenic differentiation. Satellite cells were obtained from the same type of transgenic mouse and injected (5x10 5 cells/muscle) as a control in the contralateral legs of the recipient animals. Mice were sacrificed at different times after injection (from 1 to 5 weeks); tibialis anterior muscles were removed and analyzed histochemically for β- galactosidase-positive nuclei. Staining of regenerating tibialis anterior muscle 2 weeks after total bone marrow injection, showed fibers containing aligned β- galactosidase-positive nuclei similar, although less numerous, than those observed in the contralateral limb injected with satellite cells. Transverse cryostat sections showed newly-formed fibers with centrally-localized nuclei in four out of six mice at 2 to 5 weeks after injection of unfractionated bone marrow cells. No staining was observed after one week. Conversely β- galactosidase-positive, centrally-localized nuclei were observed as early as 5 days after satellite cell injection. In a second series of experiments, bone marrow from C57/MlacZ mice was fractionated in vitro into adherent and non- adherent components, which were then separately injected into the regenerating tibialis anterior muscles of 15 scid/bg mice, and analyzed after 1 , 2, and 6 weeks after injection. Both fractions gave rise to fibers containing β-galactosidase- positive nuclei, although they were apparently more abundant in muscles injected with adherent cells. Activation of the MCL3F-MlacZ transgene expression in blood or bone marrow cells was never observed in a non muscle environment, in vitro or in vivo (for example, in inflammatory cells elicited by the intraperitoneal injection of thioglycollate). These results demonstrate that a bone marrow cell population could enter a myogenic differentiation pathway when exposed to the regenerating muscle environment and actively participate in the formation of new fibers. Example 2 To test whether myogenic progenitors could be physiologically recruited from the bone marrow and access a muscle regeneration site from the peripheral circulation, genetically-marked bone marrow from C57/MlacZ mice was transplanted into 12 irradiated scid/g mice selected as recipient because they lack a suitable co-isogenic host. Five weeks after bone marrow transplantation, muscle regeneration was induced in both tibialis anterior muscles of the surviving mice. Mice were sacrificed 1-3 weeks after induction and reconstitution of both the immune and non immune component of the hematopoietic system was monitored by analysis of the morphology and phenotype of bone marrow, spleen, and peripheral blood. FACS analysis of nucleated cells showed that all transplanted animals had a circulating lymphocyte cell population which was present in immunocompetent and virtually absent in scid/bg animals. CD4 and CD8 marker analysis confirmed that mature lymphocytes were present in a proportion comparable to that of normal donors. FACS analysis of the H-2b (donor) haplotype showed that transplanted scid/g mice were fully donor chimeras. Virtually complete chimerism (80-90%) was also found in bone marrow and spleen cells. Muscle regeneration was analyzed histochemically in the tibialis anterior muscles of all transplanted mice. Transverse cryostat sections showed regenerating fibers containing β- galactosidase nuclei in 5 out of 6 mice at 2 or 3 weeks after induction of muscle injury. Hoechst nuclear staining showed that β-galactosidase nuclei were present in both immature and more mature centrally-nucleated fibers. Blue nuclei were observed in none of the three mice analyzed after 1 week, when tibialis anterior muscles showed an early regeneration pattern characterized by heavy infiltration of mononuclear cells and a majority of small, newly-formed myofibers. In rare instances, β-galactosidase-positive mononuclear cells apparently localized outside the fibers were observed in the infiltrate surrounding the areas of muscle regeneration. In other instances β-galactosidase-positive nuclei were observed in a similar position of activated satellite cells with respect to a centrally-nucleated regenerating fiber. These data confirm the existence of bone marrow-derived myogenic progenitors that can migrate into a degenerating muscle, participate in the regeneration process, and give rise to fully-differentiated muscle fibers. Example 3 To test the possibility to obtain de novo protein synthesis in regenerated muscle fibers starting from bone marrow derived progenitors, genetically- modified by transgene integration into genome DNA, total bone marrow from C57BL/6 strain mice was transduced ex-vivo with a retroviral vector coding the β -galactosidase protein with cytoplasm localization, described in Hum. Gene Ther. 4, 713-723, 1993, according to the procedure described, for example, in Science 270, 470-475, 1995, or in Hum. Gene Ther., 8, 1611-1623, 1997. Transduced bone marrow was transplanted in immunocompetent mice of co- isogenic C57BL/6-Ly5.1 strain, previously sub-lethally irradiated. Transplant engraftment was monitored 5 weeks after transplantation by percent expression of the Ly5.1 in bone marrow and circulating blood of recipient mice. Muscle regeneration was thus induced in the tibialis anterior muscle of the same mice as described in examples 1 and 2. After a further 2-4 weeks, transgene expression was monitored by cytochemical reaction for β-galactosidase in transverse and longitudinal sections of the tibial muscles as described in previous experiments. The presence of β-galactosidase in the regenerating muscle fibers indicated that the transgene introduced into the bone marrow cells was expressed in the muscle fibers, and that, starting from ex-vivo genetically- modified bone marrow, de novo protein synthesis is obtained in muscle tissue (for example dystrophin in muscle fibers from dystrophic patients).

Claims: CLAIMS 1. Bone marrow cells engineered with genes coding for dystrophin or distrophin-associated proteins. 2. Bone marrow cells according to claim 1 transduced with retroviral vector coding dystrophyn or associated proteins. 3. Bone marrow cells according to claim 1 coding for human dystrophyn, human utrophyn, human adalin, and variants thereof or functionally equivalent derivatives. 4. Bone marrow cells according to claim 1 coding for other proteins absent In other forms of muscular dystrophy. 5. Use of the cells according to anyone of claims 1-4 in the preparation of compositions for muscular dystrophy treatment.

Inventors: MAVILIO FULVIO, MAVILIO, FULVIO
Applicants: GENERA SPA, MAVILIO FULVIO, GENERA S.P.A, MAVILIO, FULVIO
Application year: 1998
Main classification: C12N5
IPC codes: A61K35, A61K48, A61P21, C12N5, C12N15