title: Positive and negative cues for modulating neurite dynamics and receptor expression.
abstract: Many current peripheral nerve repair strategies focus on delivering positive, growth promoting cues (e.g. extracellular matrix, ECM) while eliminating negative, growth inhibiting cues (e.g. chondroitin sulfate proteoglycans, CSPGs) at the injury site. We hypothesized that recapitulating the positive and negative cues of the peripheral nerve injury microenvironment would improve regeneration. First, we tested the effects of a characteristic CSPG, chondroitin sulfate A (CSA) on neurite dynamics of dissociated chick embryo dorsal root ganglion (DRG) neurons using time lapse video microscopy. DRG growth was recorded on different adhesive substrates, including a novel, porcine-derived spinal cord matrix (SCM). The SCM significantly increased frequency of neurite extension coordinated by a significant reduction in the neurites' time spent stalled. The SCM also mitigated inhibitory effects of CSA, producing longer neurites than the controls without CSA treatment. Next we aimed to elucidate receptors involved in mediating this behavior by testing the ability of CSA to upregulate cell-substrate binding receptors using flow cytometry. Our results showed a significant increase in syndecan-3 receptor expression in neurons treated with CSA. Furthermore, syndecans would most likely bind to the sulfated glycosaminoglycans measured in the SCM. Finally, we evaluated neurite growth on biomaterial scaffolds featuring CSA and SCM cues. Our results showed significantly increased neurite outgrowth on electrospun hyaluronic acid fibers with SCM and low levels of CSA. Higher incorporation of CSA maintained its inhibitory properties. Future work will evaluate coupling CSPGs with growth-permissive ECM to assess the combined effect on neurite outgrowth.
authors.affiliation: Department of Biomedical Engineering, Wayne State University, 5050 Anthony Wayne Drive, Detroit, MI 48202, United States of America.
authors.forename: Melissa R
authors.initials: MR
authors.lastname: Wrobel
authors.forename: Harini G
authors.initials: HG
authors.lastname: Sundararaghavan
mesh_terms: D000818:Animals; D001672:Biocompatible Materials / Q000737:chemistry; D060833:Cellular Microenvironment / Q000502:physiology; D002642:Chick Embryo; D011508:Chondroitin Sulfate Proteoglycans / Q000502:physiology; D002809:Chondroitin Sulfates / Q000502:physiology; D005109:Extracellular Matrix / Q000502:physiology; D005727:Ganglia, Spinal / Q000166:cytology; D008422:Materials Testing; D057139:Nanofibers / Q000737:chemistry; D009416:Nerve Regeneration / Q000502:physiology*; D016501:Neurites / Q000502:physiology* / Q000648:ultrastructure; D059348:Peripheral Nerve Injuries / Q000503:physiopathology / Q000628:therapy; D013116:Spinal Cord / Q000502:physiology; D013552:Swine; D053670:Syndecan-3 / Q000502:physiology; D059008:Time-Lapse Imaging; D023822:Tissue Engineering / Q000379:methods; D054457:Tissue Scaffolds / Q000737:chemistry
chemical_list: D001672:Biocompatible Materials; D011508:Chondroitin Sulfate Proteoglycans; D053670:Syndecan-3; D002809:Chondroitin Sulfates