methylcellulose and Spinal-Cord-Injuries

Regenerative medicine strategies rely on exogenous cell transplantation and/or endogenous cell stimulation. Biomaterials can help to increase the regenerative potential of cells and biomolecules by controlling transplanted cell fate and provide a local, sustained release of biomolecules. In this review, we describe the use of a hyaluronan/methylcellulose (HAMC)-based hydrogel as a delivery vehicle to the brain, spinal cord, and retina to promote cellular survival and tissue repair. We discuss various controlled release strategies to prolong the delivery of factors for neuroprotection. The versatility of this hydrogel for a diversity of applications highlights its potential to enhance cell- and biomolecule-based treatment strategies.

Topics: Animals; Biocompatible Materials; Brain; Cell Survival; Central Nervous System; Drug Delivery Systems; Humans; Hyaluronic Acid; Hydrogels; Methylcellulose; Retina; Spinal Cord; Spinal Cord Injuries; Stem Cells

A hydrogel that can deliver both proteins and cells enables the local microenvironment of transplanted cells to be manipulated with a single injection. Toward this goal, we designed a hydrogel suitable for the co-delivery of neural stem cells and chondroitinase ABC (ChABC), a potent enzyme that degrades the glial scar that forms after central nervous system (CNS) injury. We leveraged the inverse electron-demand Diels-Alder reaction between norbornene and methylphenyltetrazine to form rapidly gelling (<15 min) crosslinked methylcellulose (MC) hydrogels at physiological temperature and pH, with Young's modulus similar to that of brain tissue (1-3 kPa), and degradable, disulfide-containing crosslinkers. To achieve tunable, affinity-controlled release of a ChABC-Src homology 3 (SH3) fusion protein, we immobilized norbornene-functionalized SH3-binding peptides onto MC-methylphenyltetrazine and observed release of bioactive ChABC-SH3 over 4 days. We confirmed cytocompatibility by evaluating neural progenitor cell survival and proliferation. The combined encapsulation of neural stem cells and chondroitinase ABC from one hydrogel lays the framework for future in vivo studies to treat CNS injuries.

Topics: Chondroitin ABC Lyase; Electrons; Humans; Hydrogels; Methylcellulose; Neural Stem Cells; Spinal Cord Injuries

Traumatic spinal cord injury (SCI) causes neuronal death, demyelination, axonal degeneration, inflammation, glial scar formation, and cystic cavitation resulting in interruption of neural signaling and loss of nerve function. Multifactorial targeted therapy is a promising strategy for SCI.. The anti-inflammatory peptide KAFAKLAARLYRKALARQLGVAA (KAFAK) and brain-derived neurotrophic factor (BDNF)-modified hyaluronan-methylcellulose (HAMC) hydrogel was designed for minimally invasive, localized, and sustained intrathecal protein delivery. The physical and biological characteristics of HAMC-KAFAK/BDNF hydrogel were measured in vitro. SCI model was performed in rats and HAMC-KAFAK/BDNF hydrogel was injected into the injured site of spinal cord. The neuronal regeneration effect was evaluated by inflammatory cytokine levels, behavioral test and histological analysis at 8 weeks post operation.. HAMC-KAFAK/BDNF hydrogel showed minimally swelling property and sustained release of the KAFAK and BDNF. HAMC-KAFAK/BDNF hydrogel significantly improved the proliferation of PC12 cells in vitro without cytotoxicity. Significant recovery in both neurological function and nerve tissue morphology in SCI rats were observed in HAMC-KAFAK/BDNF group. HAMC-KAFAK/BDNF group showed significant reduction in proinflammatory cytokines expression and cystic cavitation, decreased glial scar formation, and improved neuronal survival in the rat SCI model compared to HAMC group and SCI group.. The HAMC-KAFAK/BDNF hydrogel promotes functional recovery of rats with spinal cord injury by regulating inflammatory cytokine levels and improving axonal regeneration.

Topics: Amino Acid Sequence; Animals; Anti-Inflammatory Agents; Brain-Derived Neurotrophic Factor; Cytokines; Female; Hyaluronic Acid; Hydrogels; Methylcellulose; Nerve Regeneration; Peptides; Rats; Rats, Sprague-Dawley; Recovery of Function; Spinal Cord Injuries

Treatment of chronic spinal cord injury (SCI) is challenging due to cell loss, cyst formation, and the glial scar. Previously, we reported on the therapeutic potential of a neural progenitor cell (NPC) and chondroitinase ABC (ChABC) combinatorial therapy for chronic SCI. However, the source of NPCs and delivery system required for ChABC remained barriers to clinical application. Here, we investigated directly reprogrammed human NPCs biased toward an oligodendrogenic fate (oNPCs) in combination with sustained delivery of ChABC using an innovative affinity release strategy in a crosslinked methylcellulose biomaterial for the treatment of chronic SCI in an immunodeficient rat model. This combinatorial therapy increased long-term survival of oNPCs around the lesion epicenter, facilitated greater oligodendrocyte differentiation, remyelination of the spared axons by engrafted oNPCs, enhanced synaptic connectivity with anterior horn cells and neurobehavioral recovery. This combinatorial therapy is a promising strategy to regenerate the chronically injured spinal cord.

Topics: Animals; Anterior Horn Cells; Axons; Cell Differentiation; Cell Lineage; Cell Survival; Chondroitin ABC Lyase; Chondroitin Sulfate Proteoglycans; Chronic Disease; Cicatrix; Cross-Linking Reagents; Female; Humans; Methylcellulose; Motor Activity; Neural Stem Cells; Neuralgia; Neuronal Plasticity; Oligodendroglia; Rats; Recovery of Function; Remyelination; Spinal Cord Injuries; Synapses

Traumatic spinal cord injury (SCI) is a devastating event for which functional recovery remains elusive. Due to the complex nature of SCI pathology, a combination treatment strategy will likely be required for success. We hypothesized that tissue and functional repair would be achieved in a rat model of impact-compression SCI by combining degradation of the glial scar, using chondroitinase ABC (ChABC), with recruitment of endogenous neural precursor cells (NPCs), using stromal cell-derived factor 1α (SDF). To test this hypothesis, we designed a crosslinked methylcellulose hydrogel (XMC) for minimally invasive, localized, and sustained intrathecal drug delivery. ChABC was released from XMC using protein-peptide affinity interactions while SDF was delivered by electrostatic affinity interactions from polymeric nanoparticles embedded in XMC. Rats with SCI were treated acutely with a combination of SDF and ChABC, SDF alone, ChABC alone, or vehicle alone, and compared to injury only. Treatment with ChABC, both alone and in combination with SDF, resulted in faster and more sustained behavioural improvement over time than other groups. The significantly reduced chondroitin sulfate proteoglycan levels and greater distribution of NPCs throughout the spinal cord tissue with ChABC delivery, both alone and in combination with SDF, may explain the improved locomotor function. Treatment with SDF alone had no apparent effect on NPC number or distribution nor synergistic effect with ChABC delivery. Thus, in this model of SCI, tissue and functional repair is attributed to ChABC.

Topics: Animals; Chemokine CXCL12; Chondroitin ABC Lyase; Chondroitin Sulfate Proteoglycans; Enzyme-Linked Immunosorbent Assay; Female; Hydrogel, Polyethylene Glycol Dimethacrylate; Immunohistochemistry; Methylcellulose; Neural Stem Cells; Rats; Rats, Sprague-Dawley; Spinal Cord Injuries

Transplantation of pluripotent stem cells and their differentiated progeny has the potential to preserve or regenerate functional pathways and improve function after central nervous system injury. However, their utility has been hampered by poor survival and the potential to form tumors. Peptide-modified biomaterials influence cell adhesion, survival and differentiation in vitro, but their effectiveness in vivo remains uncertain. We synthesized a peptide-modified, minimally invasive, injectable hydrogel comprised of hyaluronan and methylcellulose to enhance the survival and differentiation of human induced pluripotent stem cell-derived oligodendrocyte progenitor cells. Cells were transplanted subacutely after a moderate clip compression rat spinal cord injury. The hydrogel, modified with the RGD peptide and platelet-derived growth factor (PDGF-A), promoted early survival and integration of grafted cells. However, prolific teratoma formation was evident when cells were transplanted in media at longer survival times, indicating that either this cell line or the way in which it was cultured is unsuitable for human use. Interestingly, teratoma formation was attenuated when cells were transplanted in the hydrogel, where most cells differentiated to a glial phenotype. Thus, this hydrogel promoted cell survival and integration, and attenuated teratoma formation by promoting cell differentiation.

Topics: Animals; Behavior, Animal; Cattle; Cell Differentiation; Cell Lineage; Cell Movement; Cell Survival; Disease Models, Animal; Female; Flow Cytometry; Humans; Hyaluronic Acid; Hydrogel, Polyethylene Glycol Dimethacrylate; Induced Pluripotent Stem Cells; Injections; Methylcellulose; Oligodendroglia; Oligopeptides; Platelet-Derived Growth Factor; Rats, Sprague-Dawley; Spinal Cord Injuries; Teratoma

MMP9-responsive bivalirudin-HPMA copolymers were synthesized for direct, local administration in rat spinal cord contusion injury models. Polymer-conjugated bivalirudin peptides maintained activity while demonstrating enzyme-mediated release upon MMP9 exposure and prolonged release from hyaluronic acid/methylcellulose (HAMC) hydrogels compared to free bivalirudin peptide. Localized administration of bivalirudin copolymers in vivo at the site of rat spinal cord injury decreased cellular proliferation and astrogliosis, suggesting the bivalirudin copolymer and HAMC hydrogel system are a promising therapeutic intervention for reducing immediate inflammatory responses and long term scarring.

Topics: Animals; Hirudins; Hyaluronic Acid; Hydrogel, Polyethylene Glycol Dimethacrylate; Hydrogels; Matrix Metalloproteinase 9; Methylcellulose; Peptide Fragments; Rats; Recombinant Proteins; Spinal Cord Injuries; Thrombin

Traumatic injury to the spinal cord causes cell death, demyelination, axonal degeneration, and cavitation resulting in functional motor and sensory loss. Stem cell therapy is a promising approach for spinal cord injury (SCI); however, this strategy is currently limited by the poor survival and uncontrolled differentiation of transplanted stem cells. In an attempt to achieve greater survival and integration with the host tissue, we examined the survival and efficacy of adult brain-derived neural stem/progenitor cells (NSPCs) injected within a hydrogel blend of hyaluronan and methyl cellulose (HAMC) into a subacute, clinically relevant model of rat SCI. Prior to use, HAMC was covalently modified with recombinant rat platelet-derived growth factor-A (rPDGF-A) to promote oligodendrocytic differentiation. SCI rats transplanted with NSPCs in HAMC-rPDGF-A showed improved behavioral recovery compared to rats transplanted with NSPCs in media. Rats with NSPC/HAMC-rPDGF-A transplants had a significant reduction in cavitation, improved graft survival, increased oligodendrocytic differentiation, and sparing of perilesional host oligodendrocytes and neurons. These data suggest that HAMC-rPDGF-A is a promising vehicle for cell delivery to the injured spinal cord.

Topics: Animals; Cell Count; Cell Differentiation; Cell Survival; Female; Graft Survival; Hyaluronic Acid; Hydrogel, Polyethylene Glycol Dimethacrylate; Inflammation; Methylcellulose; Neural Stem Cells; Oligodendroglia; Platelet-Derived Growth Factor; Rats; Rats, Wistar; Recovery of Function; Spinal Cord Injuries; Stem Cell Transplantation; Wound Healing

No effective clinical treatment currently exists for traumatic spinal cord injury. Cell replacement therapy holds promise for attaining functional repair. Cells may be delivered directly or near the injury site; however, this strategy requires a delivery vehicle to maintain cell viability. We have identified an injectable, biocompatible, and biodegradable hydrogel scaffold composed of hyaluronan (HA) and methylcellulose (MC) that may be an effective scaffold for therapeutic cell delivery. The purpose of the present study was to determine the effects of polymer concentration on HAMC mechanical strength, gelation time, and cell viability. The yield stress of HAMC, a measure of mechanical stiffness, was tunable via manipulation of MC and HA content. Measurement of the elastic and storage moduli as functions of time revealed that HAMC gels in less than 5 min at physiological temperatures. Human umbilical tissue-derived cells encapsulated in HAMC were homogenously and stably distributed over 3 days in culture and extended processes into the scaffold. Cell viability was stable over this period in all but the most concentrated HAMC formulation. Because of its strength-tunability, rapid gelation, and ability to maintain cell viability, HAMC is a promising vehicle for cell delivery and is being tested in ongoing in vivo studies.

Topics: Cell Survival; Cell- and Tissue-Based Therapy; Cells, Cultured; Elastic Modulus; Humans; Hyaluronic Acid; Hydrogels; Methylcellulose; Rheology; Spinal Cord Injuries; Tissue Scaffolds

Anti-NogoA is a promising anti-inhibitory molecule that has been shown to enhance functional recovery after spinal cord injury when delivered in rat and primate models over the span of weeks. To achieve this sustained release, anti-NogoA is typically delivered by osmotic minipumps; however, external minipumps are susceptible to infection. To address this issue, we developed a drug delivery system that consists of anti-NogoA-loaded poly(lactic-co-glycolic acid) nanoparticles dispersed in a hydrogel of hyaluronan and methylcellulose (composite HAMC). To optimize in vitro release, we screened formulations for improved anti-NogoA bioactivity and sustained release based on combinations of co-encapsulated trehalose, hyaluronan, MgCO(3), and CaCO(3). Co-encapsulated MgCO(3) and CaCO(3) slowed the rate of anti-NogoA release and did not influence anti-NogoA bioactivity. Co-encapsulated trehalose significantly improved anti-NogoA bioactivity at early release time points by stabilizing the protein during lyophilization. Co-encapsulated trehalose with hyaluronan improved bioactivity up to 28d and dramatically increased the rate and duration of sustained delivery. The sustained release of bioactive anti-NogoA from composite HAMC is a compelling formulation for in vivo evaluation in a model of spinal cord injury.

Topics: Antibodies, Monoclonal; Calcium Carbonate; Chemistry, Pharmaceutical; Delayed-Action Preparations; Drug Carriers; Drug Compounding; Drug Stability; Enzyme-Linked Immunosorbent Assay; Excipients; Freeze Drying; Hyaluronic Acid; Hydrogels; Kinetics; Lactic Acid; Magnesium; Methylcellulose; Myelin Proteins; Nanoparticles; Nanotechnology; Nogo Proteins; Polyglycolic Acid; Polylactic Acid-Polyglycolic Acid Copolymer; Polymers; Solubility; Spinal Cord Injuries; Technology, Pharmaceutical; Trehalose

The authors investigated the feasibility of using injectable hydrogels, based on poly(N-isopropylacrylamide) (PNIPAAm), lightly cross-linked with polyethylene glycol (PEG) or methylcellulose (MC), to serve as injectable scaffolds for local delivery of neurotrophins and cellular transplants into the injured spinal cord. The primary aims of this work were to assess the biocompatibility of the scaffolds by evaluating graft cell survival and the host tissue immune response. The scaffolds were also evaluated for their ability to promote axonal growth through the action of released brain-derived neurotrophic factor (BDNF).. The in vivo performance of PNIPAAm-g-PEG and PNIPAAm-g-MC was evaluated using a rodent model of spinal cord injury (SCI). The hydrogels were injected as viscous liquids into the injury site and formed space-filling hydrogels. The host immune response and biocompatibility of the scaffolds were evaluated at 2 weeks by histological and fluorescent immunohistochemical analysis. Commercially available matrices were used as a control and examined for comparison.. Experiments showed that the scaffolds did not contribute to an injury-related inflammatory response. PNIPAAm-g-PEG was also shown to be an effective vehicle for delivery of cellular transplants and supported graft survival. Additionally, PNIPAAm-g-PEG and PNIPAAm-g-MC are permissive to axonal growth and can serve as injectable scaffolds for local delivery of BDNF.. Based on the results, the authors suggest that these copolymers are feasible injectable scaffolds for cell grafting into the injured spinal cord and for delivery of therapeutic factors.

Topics: Acrylamides; Acrylic Resins; Animals; Axons; Brain-Derived Neurotrophic Factor; Cell Transplantation; Cicatrix; Disease Models, Animal; Drug Delivery Systems; Female; Graft Survival; Hydrogels; Injections, Intralesional; Methylcellulose; Nerve Regeneration; Neuroglia; Pilot Projects; Polyethylene Glycols; Polymers; Rats; Rats, Sprague-Dawley; Spinal Cord Injuries; Tissue Scaffolds

There is no effective treatment for spinal cord injury and clinical drug delivery techniques are limited by the blood-spinal cord barrier. Our lab has developed an injectable drug delivery system consisting of a biopolymer blend of hyaluronan and methylcellulose (HAMC) that can sustain drug release for up to 24h in the intrathecal space. Fibroblast growth factor 2 (FGF2) has great potential for treatment of spinal cord injury due to its angiogenic and trophic effects, but previous studies showed no penetration into spinal cord tissue when delivered locally. Conjugation to poly(ethylene glycol) (PEG) is known to improve penetration of proteins into tissue by reducing clearance and providing immunogenic shielding. We investigated conjugation of PEG to FGF2 and compared its distribution relative to unmodified FGF2 in injured spinal cord tissue when delivered intrathecally from HAMC. Importantly, PEG conjugation nearly doubled the concentration of FGF2 in the injured spinal cord when delivered locally and, contrary to previous reports, we show that some FGF2 penetrated into the injured spinal cord using a more sensitive detection technique. Our results suggest that PEGylation of FGF2 enhanced tissue penetration by reducing its rate of elimination.

Topics: Animals; Drug Administration Routes; Drug Delivery Systems; Fibroblast Growth Factor 2; Hyaluronic Acid; Injections, Spinal; Methylcellulose; Mice; Polyethylene Glycols; Rats; Rats, Sprague-Dawley; Spinal Cord; Spinal Cord Injuries

Major traumatic spinal cord injury (SCI) results in permanent paralysis below the site of injury. The effectiveness of systemically delivered pharmacological therapies against SCI can be limited by the blood-spinal cord barrier and side effects. Local drug delivery to the injured spinal cord can be achieved using a minimally invasive biopolymer matrix of hyaluronan and methylcellulose injected into the intrathecal space, bypassing the blood-spinal cord barrier and overcoming limitations of existing strategies. Composite hydrogels of drug-loaded poly(lactide-co-glycolide) (PLGA) nanoparticles dispersed in this biopolymer matrix meet the in vitro design criteria for prolonged local release. Using a blank (without drug) composite designed for 28-day sustained release, we presently explore the mechanism of particle-mediated hydrogel stabilization in vitro and aspects of biocompatibility and safety in vivo. The composite hydrogel is well tolerated in the intrathecal space of spinal cord injured rats, showing no increase in inflammation, scarring, or cavity volume relative to controls, and no significant effect on locomotor function up to 28 days. Furthermore, there was no effect on locomotor function in healthy animals which received the composite hydrogel, although a qualitative increase in ED-1 staining was apparent. These data support the further development of composite hydrogels of hyaluronan and methylcellulose containing PLGA nanoparticles for sustained local delivery to the injured spinal cord, an application for which there are no approved alternatives.

Topics: Animals; Behavior, Animal; Biocompatible Materials; Drug Administration Routes; Drug Carriers; Female; Humans; Hyaluronic Acid; Hydrogels; Injections, Spinal; Lactic Acid; Materials Testing; Methylcellulose; Motor Activity; Nanocomposites; Polyglycolic Acid; Polylactic Acid-Polyglycolic Acid Copolymer; Polymers; Rats; Rats, Sprague-Dawley; Spinal Cord Injuries

Following spinal cord injury, profound vascular changes lead to ischemia and hypoxia of spinal cord tissue. Since fibroblast growth factor 2 (FGF2) has angiogenic effects, its delivery to the injured spinal cord may attenuate the tissue damage associated with ischemia. To limit systemic mitogenic effects, FGF2 was delivered to the spinal cord via a gel of hyaluronan and methylcellulose (HAMC) injected into the intrathecal space, and compared to controls receiving HAMC alone and artificial cerebrospinal fluid (aCSF) alone. Dynamic perfusion computed tomography (CT) was employed for the first time in small animals to serially measure blood flow and permeability in the injured and uninjured spinal cord. Spinal cord blood flow (SCBF) and permeability-surface area (PS) measurements were obtained near the injury epicenter, and at two regions rostral to the epicenter in animals that received a 26-g clip compression injury. As predicted, SCBF measurements decreased and PS increased after injury. FGF2 delivered via HAMC after injury restored SCBF towards pre-injury values in all regions, and increased blood flow rates at 7 days post-injury compared to pre-injury measurements. PS was stabilized at regions rostral to the epicenter of injury when FGF2 was delivered with HAMC, with significantly lower values than aCSF controls at 7 days in the region farthest from the epicenter. Laminin staining for blood vessels showed a qualitative increase in vessel density after 7 days when FGF2 was locally delivered. Additionally, permeability stains showed that FGF2 moderately decreased permeability at 7 days post-injury. These data demonstrate that localized delivery of FGF2 improves spinal cord hemodynamics following injury, and that perfusion CT is an important technique to serially measure these parameters in small animal models of spinal cord injury.

Topics: Animals; Blood Gas Analysis; Capillary Permeability; Data Interpretation, Statistical; Excipients; Fibroblast Growth Factors; Gels; Hyaluronic Acid; Image Processing, Computer-Assisted; Immunohistochemistry; Methylcellulose; Rats; Rats, Sprague-Dawley; Regional Blood Flow; Spinal Cord; Spinal Cord Injuries; Tomography, X-Ray Computed

After spinal cord injury (SCI), a complex cascade of events leads to tissue degeneration and a penumbra of cell death. Neuroprotective molecules to limit tissue loss are promising; however, intravenous delivery is limited by the blood-spinal cord barrier and short systemic half-life. Current local delivery strategies are flawed: bolus injection results in drug dispersion throughout the intrathecal (IT) space, and catheters/pumps are invasive and open to infection. Our laboratory previously developed a hydrogel of hyaluronan (HA) and methylcellulose (MC) (HAMC) that, when injected into the IT space, was safe and, remarkably, had some therapeutic benefit on its own. In order to test this new paradigm of local and sustained delivery, relative to conventional delivery strategies, we tested, for the first time, the in vivo efficacy of HAMC as an IT drug delivery system by delivering a known neuroprotective molecule, erythropoietin (EPO). In vitro studies showed that EPO was released from HAMC within 16 h, with 80% bioactivity maintained. When the material alone was injected in vivo, individual fluorescent labels on HA and MC showed that HA dissolved from the gel within 24 h, whereas the hydrophobically associated MC persisted in the IT space for 4-7 days. Using a clip compression injury model of moderate severity, HAMC with EPO was injected in the IT space and, in order to better understand the potential of this delivery system, compared to the therapeutic effect of both common delivery strategies-IT EPO and intraperitoneal EPO-and a control of IT HAMC alone. IT HAMC delivery of EPO resulted in both reduced cavitation after SCI and a greater number of neurons relative to the other delivery strategies. These data suggest that the localized and sustained release of EPO at the tissue site by HAMC delivery enhances neuroprotection. This new system of IT delivery holds great promise for the safe, efficacious, and local delivery of therapeutic molecules directly to the spinal cord.

Topics: Animals; Cell Count; Delayed-Action Preparations; Drug Delivery Systems; Erythropoietin; Hyaluronic Acid; Methylcellulose; Neuroprotective Agents; Rats; Rats, Sprague-Dawley; Spinal Cord Injuries; Wound Healing

We report the development of a series of physical hydrogel blends composed of hyaluronan (HA) and methyl cellulose (MC) designed for independent delivery of one or more drugs, from 1 to 28 days, for ultimate application in spinal cord injury repair strategies. To achieve a diversity of release profiles we exploit the combination of fast diffusion-controlled release of dissolved solutes from the HAMC itself and slow drug release from poly(lactide-co-glycolide) particles dispersed within the gel. Delivery from the composite hydrogels was demonstrated using the neuroprotective molecules NBQX and FGF-2, which were released for 1 and 4 days, respectively; the neuroregenerative molecules dbcAMP and EGF, and proteins alpha-chymotrypsin and IgG, which were released for 28 days. alpha-chymotrypsin and IgG were selected as model proteins for the clinically relevant neurotrophin-3 and anti-NogoA. Particle loaded hydrogels were significantly more stable than HAMC alone and drug release was longer and more linear than from particles alone. The composite hydrogels are minimally swelling and injectable through a 30 gauge/200 microm inner diameter needle at particle loads up to 15 wt.% and particle diameters up to 15 microm.

Topics: Drug Delivery Systems; Humans; Hyaluronic Acid; Hydrogels; Injections; Methylcellulose; Pharmaceutical Preparations; Spinal Cord Injuries

We have previously shown that a novel synthetic hydrogel channel composed of poly(2-hydroxyethyl methacrylate-co-methyl methacrylate) (pHEMA-MMA) is biocompatible and supports axonal regeneration after spinal cord injury. Our goal was to improve the number and type of regenerated axons within the spinal cord through the addition of different matrices and growth factors incorporated within the lumen of the channel. After complete spinal cord transection at T8, pHEMA-MMA channels, having an elastic modulus of 263+/-13 kPa were implanted into adult Sprague Dawley rats. The channels were then filled with one of the following matrices: collagen, fibrin, Matrigel, methylcellulose, or smaller pHEMA-MMA tubes placed within a larger pHEMA-MMA channel (called tubes within channels, TWC). We also supplemented selected matrices (collagen and fibrin) with neurotrophic factors, fibroblast growth factor-1 (FGF-1) and neurotrophin-3 (NT-3). After channel implantation, fibrin glue was applied to the cord-channel interface, and a duraplasty was performed with an expanded polytetrafluoroethylene (ePTFE) membrane. Controls included animals that had either complete spinal cord transection and implantation of unfilled pHEMA-MMA channels or complete spinal cord transection. Regeneration was assessed by retrograde axonal tracing with Fluoro-Gold, and immunohistochemistry with NF-200 (for total axon counts) and calcitonin gene related peptide (CGRP, for sensory axon counts) after 8 weeks survival. Fibrin, Matrigel, methylcellulose, collagen with FGF-1, collagen with NT-3, fibrin with FGF-1, and fibrin with NT-3 increased the total axon density within the channel (ANOVA, p<0.05) compared to unfilled channel controls. Only fibrin with FGF-1 decreased the sensory axon density compared to unfilled channel controls (ANOVA, p<0.05). Fibrin promoted the greatest axonal regeneration from reticular neurons, and methylcellulose promoted the greatest regeneration from vestibular and red nucleus neurons. With Matrigel, there was no axonal regeneration from brainstem motor neurons. The addition of FGF-1 increased the axonal regeneration of vestibular neurons, and the addition of NT-3 decreased the total number of axons regenerating from brainstem neurons. The fibrin and TWC showed a consistent improvement in locomotor function at both 7 and 8 weeks. Thus, the present study shows that the presence and type of matrix contained within synthetic hydrogel guidance channels affects the quantity and

Topics: Animals; Axons; Calcitonin Gene-Related Peptide; Collagen; Delayed-Action Preparations; Drug Combinations; Female; Fibrin; Fibroblast Growth Factor 1; Guided Tissue Regeneration; Hydrogels; Immunohistochemistry; Laminin; Methylcellulose; Methylmethacrylates; Microscopy, Electron; Myelin Sheath; Nerve Fibers; Nerve Regeneration; Neurofilament Proteins; Neurotrophin 3; Polyhydroxyethyl Methacrylate; Proteoglycans; Rats; Rats, Sprague-Dawley; Spinal Cord; Spinal Cord Injuries

Strategies for spinal cord injury repair are limited, in part, by poor drug delivery techniques. A novel drug delivery system (DDS) is being developed in our laboratory that can provide localized release of growth factors from an injectable gel. The gel must be fast-gelling, non-cell adhesive, degradable, and biocompatible as an injectable intrathecal DDS. A gel that meets these design criteria is a blend of hyaluronan and methylcellulose (HAMC). Unlike other injectable gels, HAMC is already at the gelation point prior to injection. It is injectable due to its shear-thinning property, and its gel strength increases with temperature. In vivo rat studies show that HAMC is biocompatible within the intrathecal space for 1 month, and may provide therapeutic benefit, in terms of behavior, as measured by the Basso, Beattie and Bresnahan (BBB) locomotor scale, and inflammation. These data suggest that HAMC is a promising gel for localized delivery of therapeutic agents to the injured spinal cord.

Topics: Animals; Biocompatible Materials; Cell Adhesion; Female; Gels; Hyaluronic Acid; Injections, Spinal; Macrophages; Materials Testing; Methylcellulose; Mice; Microglia; NIH 3T3 Cells; Rats; Rats, Sprague-Dawley; Rheology; Spinal Cord Injuries