Abstract:
Brain stimulators are used to treat a variety of disorders, and their range of uses continues expand. However, one problem with long-term stimulation of neural tissue is the need to increase the stimulation parameters to continue to maintain the same clinical effect. This is thought to be due to local tissue reaction to the implanted foreign body. Because the implanted stimulator functions by means of contact with functional cells within the tissue, prevention of tissue reaction to the stimulator would make a significant improvement to the device&#39;s performance and longevity. 
     It is proposed that coating a neural stimulator device with decorin, and/or homologous molecules of functional or structural likeness to decorin, can function to decrease gliosis and other local tissue reaction in neural tissue. The present invention provides a novel system and method of device design and utilization that can prevent and suppress known associated tissue reactions associated with neural modulation of tissue with an implanted device, thereby improving the device&#39;s performance and longevity.

Description:
BACKGROUND OF THE INVENTION 
       [0001]    Stimulators of neural tissue are used to treat a variety of disorders, and they can include any deep brain stimulator, cortical stimulator, spinal cord stimulator, or nerve stimulator. Deep brain stimulators in particular are used to treat a large range of diseases and conditions, including dystonias, tremors, and other movement disorders such as Parkinson&#39;s disease (Weaver et al. 2009). Their use, however, is expanding to a wider variety of pathologies, such as epilepsy, multiple sclerosis, depression, obsessive-compulsive disorder, anxiety, obesity, eating disorders, neuroprosthesis implantation and control, chronic pain, minimally conscious states, cerebral palsy, stroke, amyotrophic lateral sclerosis, tourette syndrome, or spinal cord injury and its sequelae (including paraplegia, tetraplegia, spasticity, autonomic dysreflexia, and autonomic dysfunction of bowel and bladder). Their range of uses continues to be researched and developed. 
         [0002]    One problem with long-term neural stimulation is the need to increase the stimulation parameters to continue to maintain the same clinical effect. Such parameters may include voltage, amperage, frequency, or pulse width. These parameters need to be adjusted over time occurs regardless of diagnosis or target site (Moss et al., 2004; Krack et al., 2003; Sydow et al., 2003; Wishart et al., 2003; Yianni et al.; 2003; Lozano 2001). This is thought to be due primarily to gliosis, reactive astrocytosis, and other local tissue reaction, such as microglial activation, leukocyte invasion, siderophages, tissue vacuolization, and multinucleated giant cell reaction (Moss et al. 2004; Nielsen et al. 2007; Sun et al. 2008). In fact, giant cell reaction was found to be invariably present as early as three months after electrode insertion (Moss, et al. 2004) 
         [0003]    Due to these cellular and molecular changes, impedance and current distribution through the tissue are altered, thus attenuating the effectiveness of the stimulator. Because the implanted stimulator functions by means of contact with functional cells within the tissue, prevention of tissue reaction to the stimulator would make a significant improvement to the device&#39;s performance and longevity. 
       DETAILED DESCRIPTION OF THE INVENTION 
       [0004]    The present invention provides a novel system and method of device design and utilization that can prevent and suppress known associated tissue reactions associated with neural modulation of tissue with an implanted device, and which may also treat pathology related to gliosis, inflammatory neural tissue reaction, reactive astrocytosis, microglial activation, leukocyte invasion, siderophages, tissue vacuolization, multinucleated giant cell reaction, or other related diseases and processes. It is proposed that coating the implanted neural stimulator device with decorin, and/or homologous molecules of functional or structural similarity to any portion of decorin (hereafter referred to as a “decorin-like molecule”) can function to decrease gliosis and other tissue reaction in neural tissue, thereby significantly improving the device&#39;s performance and longevity. 
         [0005]    The molecular structure of decorin has been detailed in the literature (Krusius and Ruoslahti 1986; Vesentini et al., 2003; NCBI online database gene ID 1634). Decorin is a proteoglycan that has an average molecular weight of 87-140 kilodaltons (kD) and belongs to the family of small leucine-rich proteoglycans. Decorin has a core protein component which may be bound to a glycosaminoglycan chain, and it may have many alternative splice variants. Functional equivalents of decorin include decorin native proteins, decorin core protein, decorin alternative splice variants, biglycan, fibromodulin, lumican, and other modifications, to or alternative homologous amino acid sequences of decorin. 
         [0006]    Evidence suggests that the mechanism of decorin in neural tissues is via inhibition of the TGF-beta signaling pathway (Yamaguchi et al., 1990; Johns et al., 1992; Rabchevsky et al., 1998; Logan et al., 1999; Asher et al., 2000; Dobbertin et al., 2003; Logan and Baird, U.S. Pat. No. 5,958,411, 1995). Evidence also suggests that decorin inhibits the EGFR tyrosine kinase (Santra et al., 2002), and there is preliminary evidence to suggest that other signaling pathways are involved as well. Other proposed mechanisms include inhibition of complement activation (Krumdiek et al., U.S. Pat. No. 5,650,389, 1993), but this has not been shown to play a primary role in the central nervous system or in neural tissue reaction to foreign bodies. The detailed mechanisms remain to be fully elucidated. 
         [0007]    Decorin has been shown to have several other cellular effects, including the suppression of neurocan, brevican, phosphacan, and NG2 expression, as well as reduction of astrogliosis and basal lamina formation after local traumatic injury (Davies et al., 2004). Davies, et al., also showed that decorin suppressed astrogliosis and macrophage/microglia accumulation at lesion sites in the central nervous system. It is also known that decorin naturally binds to collagen type I fibrils (Vesentini et al., 2003). 
         [0008]    The novel aspect of the device is an external layer or coating with a decorin-like protein, which may be integrated or manufactured by several means. This includes chemical coupling of the molecule to the device&#39;s surface, such as by either the amino groups or carboxyl groups in the amino acid sequence, or by any molecular component of the proteoglycan chain. This may be done using the chemical reagents well known in the art: for example, amine-reactive crosslinkers, such as dithiobis succinimidyl propionate (DSP), which uses disulfide linkages to attach to a surface and links proteins by their primary amine groups, or other compounds, such as 1-Ethyl-3-(3-dimethylaminopropyl)-carbodiimide (EDC), etc. Alternatively, the decorin-like protein may be bound by polymers that cross-link or otherwise allow for adherence or attachment to the device. Alternatively, the decorin-like protein may be bound by means of its glycosaminoglycan component, its peptide backbone, its R-groups, or other moieties, or it may be modified with certain amino acid sequences that allow for binding to the surface of the device. In addition, the device surface itself may be manufactured with an absorbent or adherent coating that either contains or adheres to the decorin-like protein. This adherent coating may be made of any type of material, such as plastics, polymers, glues, ceramics, metals, silicates, carbon-based compounds, or other similar materials. The surface may also be covered with a second coating to slow the diffusion of the decorin-like molecule into surrounding tissue. 
         [0009]    With reference to the implantable electrical stimulation device used in concert with the decorin-like molecule, it may be of any design that incorporates a conductive surface that contacts the tissue, whether made of metal (e.g., platinum-iridium, cobalt-chrome, or other alloys) or other conductive material (e.g., conductive polymers or ceramics) (Geddes and Roeder, 2003; Gimsa et al., 2005). The device may also have an insulative material to shield from conduction of current at non-targeted tissue sites. Both the conductive surfaces and insulative surfaces may integrate the decorin-like molecular surface. The device may utilize monopolar, bipolar, or multipolar stimulation, and may have any number of electrical leads, and may incorporate electrical feedback systems. The device may be internally or externally powered, and may be temporarily or permanently placed in the tissue. The device may be of any length, width, and curvature. The device may also be used for extraction or sampling of tissue or fluids, and may also be used for delivery of pharmaceutical agents or solutions, for example, through a cannula system. 
         [0010]    Many variations of the device may be constructed which are bound within the scope of the invention. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0011]    The advantages and features of the invention are further described in the following drawings. 
           [0012]      FIG. 1A  is an example of a brain stimulator. This drawing shows only one of many possible examples of neural stimulation devices. 
           [0013]      FIG. 1B  is an expanded view of the surface of the device that illustrates multiple examples of possible embodiments of the invention, wherein the decorin-like molecule is attached or adhered to the surface of the stimulator device. 
       
    
    
     DESCRIPTION OF THE PREFERRED EMBODIMENTS 
       [0014]      FIG. 1A  is one of many possible examples of a neural stimulator device. The following is a reference for the numbered labels. 1) A neural stimulator device; in this case, a type of deep brain stimulator. 2) The conductive connection between the electrodes and a microprocessor system. 3) The substantive core of the device, which may be solid or hollow. 4) The insulative outer surface of the device. 5) The conductive surface electrode, which contacts the targeted tissue for electrical modulation. 
         [0015]      FIG. 1B  is an enlarged view of the surface of the device, wherein four possible examples of embodiments of the invention are illustrated. 6) The decorin-like molecule, coupled directly to the surface of the device. It should be noted that the decorin-like coating is only illustrated on one edge of the device, but that the entire device may be coated with the molecule. 7) The decorin-like molecule, coupled to the surface of the device by means of 8) an intermediary molecular structure. 9) The decorin-like molecule, coupled to the surface of the device by means of 10) an adhesive or adsorbant layer, which may be composed of plastics, polymers, glues, ceramics, metals, silicates, carbon-based compounds, or any other similar materials that can adhere the molecule to the device&#39;s surface. 11) The decorin-like molecule, coupled to the surface of the device with 12) a separate outer coating consisting of any plastics, polymers, glues, ceramics, metals, silicates, carbon-based compounds, or other similar materials, which may slow the diffusion of the decorin-like molecule into surrounding tissue. 
       REFERENCES TO RELATED APPLICATIONS 
       [0000]    
       
         McMurtrey, Richard J. “Decorin and Gliosis and Related System and Method.” U.S. Provisional Patent No. 61/151,334. Filed Feb. 10, 2009. 
         Krumdiek R, Hook M, Volanakis J. University of Alabama at Birmingham Research Foundation. “Methods for the Inhibition of Complement Activation.” U.S. Pat. No. 5,650,389. Filed Mar. 1, 1993. 
         Logan A, Baird A. The Whittier Institute for Diabetes and Endocrinology. “Methods of Inhibiting ECM Accumulation in the CNS by Inhibition of TGF-beta.” U.S. Pat. No. 5,958,411. Filed Mar. 24, 1995 
       
     
       REFERENCED PUBLICATIONS 
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Disclosure: The invention herein involved no federally sponsored research.