Spatiotemporal dynamics of the cellular components involved in glial scar formation following spinal cord injury.

Spinal cord injury (SCI) triggers complex inflammatory and pathological processes that ultimately lead to scar formation, thus resulting in the severe and irreversible loss of function. The composition of spinal cord scars in SCI can be divided into cellular components and non-cellular components such as the extracellular matrix (ECM). Studies targeting the ECM, such as chondroitin sulfate proteoglycans (CSPGs), have achieved promising therapeutic results. On the other hand, with the application of new techniques in the field of SCI, an increasing body of research has been targeted to the complex mechanisms that occur in the cellular components during scar formation. Here, we meticulously describe the spatial distribution and dynamic changes of the cellular components involved in the formation of scars following SCI, including microglia, astrocytes, fibroblasts, and macrophages, paying particular attention to the recent application of new technologies. In addition, we outline the therapeutic approaches that target the cellular components of scar formation and explore potential therapeutic measures to improve functional recovery after SCI.

A Localized Materials-Based Strategy to Non-Virally Deliver Chondroitinase ABC mRNA Improves Hindlimb Function in a Rat Spinal Cord Injury Model.

Spinal cord injury often results in devastating consequences for those afflicted, with very few therapeutic options. A central element of spinal cord injuries is astrogliosis, which forms a glial scar that inhibits neuronal regeneration post-injury. Chondroitinase ABC (ChABC) is an enzyme capable of degrading chondroitin sulfate proteoglycan (CSPG), the predominant extracellular matrix component of the glial scar. However, poor protein stability remains a challenge in its therapeutic use. Messenger RNA (mRNA) delivery is an emerging gene therapy technology for in vivo production of difficult-to-produce therapeutic proteins. Here, mineral-coated microparticles as an efficient, non-viral mRNA delivery vehicles to produce exogenous ChABC in situ within a spinal cord lesion are used. ChABC production reduces the deposition of CSPGs in an in vitro model of astrogliosis, and direct injection of these microparticles within a glial scar forces local overexpression of ChABC and improves recovery of motor function seven weeks post-injury.

Advances in chondroitinase delivery for spinal cord repair.

Chondroitin sulfate proteoglycans (CSPGs) present a formidable barrier to regrowing axons following spinal cord injury. CSPGs are secreted in response to injury and their glycosaminoglycan (GAG) side chains present steric hindrance preventing the growth of axons through the lesion site. The enzyme chondroitinase has been proven effective at reducing the CSPG GAG chains, however, there are issues with direct administration of the enzyme specifically due to its limited timeframe of activity. In this perspective article, we discuss the evolution of chondroitinase-based therapy in spinal cord injury as well as up-to-date advances on this critical therapeutic. We describe the success and the limitations around use of the bacterial enzyme namely issues around thermostability. We then discuss current efforts to improve delivery of chondroitinase with a push towards gene therapy, namely through the use of lentiviral and adeno-associated viral vectors, including the temporal modulation of its expression and activity. As a chondroitinase therapy for spinal cord injury inches nearer to the clinic, the drive towards an optimised delivery platform is currently underway.

Covering the proximal nerve stump with chondroitin sulfate proteoglycans prevents traumatic painful neuroma formation by blocking axon regeneration after neurotomy in Sprague Dawley rats.

OBJECTIVE: Neuropathic pain caused by traumatic neuromas is an extremely intractable clinical problem. Disorderly scar tissue accumulation and irregular and immature axon regeneration around the injury site mainly contribute to traumatic painful neuroma formation. Therefore, successfully preventing traumatic painful neuroma formation requires the effective inhibition of irregular axon regeneration and disorderly accumulation of scar tissue. Considering that chondroitin sulfate proteoglycans (CSPGs) can act on the growth cone and effectively inhibit axon regeneration, the authors designed and manufactured a CSPG-gelatin blocker to regulate the CSPGs' spatial distribution artificially and applied it in a rat model after sciatic nerve neurectomy to evaluate its effects in preventing traumatic painful neuroma formation. METHODS: Sixty female Sprague Dawley rats were randomly divided into three groups (positive group: no covering; blank group: covering with gelatin blocker; and CSPG group: covering with the CSPG-gelatin blocker). Pain-related factors were evaluated 2 and 8 weeks postoperatively (n = 30). Neuroma growth, autotomy behavior, and histological features of the neuromas were assessed 8 weeks postoperatively (n = 30). RESULTS: Eight weeks postoperatively, typical bulb-shaped neuromas did not form in the CSPG group, and autotomy behavior was obviously better in the CSPG group (p < 0.01) than in the other two groups. Also, in the CSPG group the regenerated axons showed a lower density and more regular and improved myelination (p < 0.01). Additionally, the distribution and density of collagenous fibers and the expression of α-smooth muscle actin were significantly lower in the CSPG group than in the positive group (p < 0.01). Regarding pain-related factors, c-fos, substance P, interleukin (IL)-17, and IL-1ß levels were significantly lower in the CSPG group than those in the positive and blank groups 2 weeks postoperatively (p < 0.05), while substance P and IL-17 remained lower in the CSPG group 8 weeks postoperatively (p < 0.05). CONCLUSIONS: The authors found that CSPGs loaded in a gelatin blocker can prevent traumatic neuroma formation and effectively relieve pain symptoms after sciatic nerve neurotomy by blocking irregular axon regeneration and disorderly collagenous fiber accumulation in the proximal nerve stump. These results indicate that covering the proximal nerve stump with CSPGs may be a new and promising strategy to prevent traumatic painful neuroma formation in the clinical setting.

Effect of Lubricin Mimetics on the Inhibition of Osteoarthritis in a Rat Anterior Cruciate Ligament Transection Model.

BACKGROUND: Lubricin, a mucinous glycoprotein, plays a chondroprotective role as a constituent of synovial fluid. Structural analogs have been synthesized to mimic the structure and function of native lubricin in an effort to recapitulate this effect with the goal of delaying progression of osteoarthritis (OA). PURPOSE: To investigate the efficacy of intra-articular injections of lubricin mimetics in slowing or preventing the progression of posttraumatic OA by using a rat anterior cruciate ligament transection model. STUDY DESIGN: Controlled laboratory design. METHODS: Four lubricin mimetics were investigated, differing from one another in their binding orientations and steric interactions. Eighty skeletally mature Sprague-Dawley rats underwent bilateral anterior cruciate ligament transections and were randomly allocated to receive intra-articular injections (50 µL/injection) of 1 of the 4 mimetics in the right knee and equal volumes of saline injection in the contralateral knee (control). All rats were euthanized 8 weeks postoperatively and assessed via biomechanical analysis, which evaluated comparative friction coefficients across the 4 groups, and histological evaluation of articular cartilage, osteophytes, and synovitis. The Osteoarthritis Research Society International (OARSI) histopathological assessment system was used to evaluate the degree of articular cartilage degeneration and osteophytes, while synovitis was assessed through a semiquantitative scoring system. Binding efficacy of the 4 mimetics was assessed in vitro and in vivo through the immunohistochemical localization of polyethylene glycol. Articular cartilage degeneration and synovitis scoring data analyses were performed with generalized estimating equation modeling. RESULTS: Injection of the group 3 mimetic (random 24 + 400 + 30) directly correlated with improved OARSI scores for femoral articular cartilage degeneration when compared with saline-injected contralateral control knees (P = .0410). No lubricin mimetic group demonstrated statistically significant differences in OARSI scores for tibial articular cartilage degeneration. Injection of the group 4 mimetic (AB 24 + 400 + 30) led to a statistically significant difference in osteophyte OARSI score (P = .0019). None of the 4 lubricin mimetics injections incited an additive synovial inflammatory response. Immunohistochemical staining substantiated the binding capacity of all 4 mimetics, while in vivo experimentation revealed that the group 1 and 3 mimetics were still retained within the joint 4 weeks after injection. There were no differences in friction coefficients between any pair of groups and no significant trends based on lubricin mimetic structure. CONCLUSION: We demonstrated that the tribosupplementation of a traumatically injured knee with a specific lubricin structural analog may attenuate the natural progression of OA. CLINICAL RELEVANCE: The current lack of efficacious clinical options to counter the onset and subsequent development of OA suggests that further investigation into the synthesis and behavior of lubricin analogs could yield novel translational applications.

Antioxidant, antiinflammatory and neuroprotective actions of chondroitin sulfate and proteoglycans.

The antiinflammatory and antiapoptotic effects of chondroitin sulfate (CS) are being used to treat osteoarthritis. Recent evidence has revealed that those peripheral effects of CS may also have therapeutic interest in diseases of the central nervous system (CNS). We review here such evidence. Perineuronal nets (PNNs) formed by chondroitin sulfate proteoglycans (CSPGs) may have a neuroprotective action against oxidative stress potentially involved in neurodegeneration. On the other hand, in human neuroblastoma SH-SY5Y cells CS has antioxidant and neuroprotective effects by activating the signaling pathway PKC/PI3K/Akt and inducing the antioxidant enzyme hemoxygenase-1. Consistent with this is the observation that protein kinase C (PKC) blockade overcomes inhibition of neurite outgrowth elicited by CSPGs. In addition, CS protects cortical neurons against excytotoxic death by phosphorylation of intracellular signals and the suppression of caspase-3 activation. Of interest is the finding that a disaccharide derived from CSPG degradation (CSGP-DS) protects neurons against toxicity both in vitro and in vivo. Furthermore, CSGP-DS efficiently protects against neuronal loss in experimental autoimmune encephalomyelitis and uveitis, decreases secretion of tumor necrosis factor-alpha (TNF-alpha) and block necrosis factor kappa B (NF-kappaB) translocation. In conclusion, CS may have neuroprotective properties linked to its antioxidant and antiinflammatory effects.

Lumcorin: a leucine-rich repeat 9-derived peptide from human lumican inhibiting melanoma cell migration.

We previously showed that lumican decreases melanoma progression. The aim of the present study was to determine the active sequence of the lumican core protein responsible for the inhibition of melanoma cell migration. Using different recombinant and synthetic peptides derived from lumican, we localized an active site in the leucine-rich repeat 9 domain of the lumican core protein. We propose the name lumcorin (fragment of lumican core protein) for the active peptide derived from this site. Lumcorin was able to inhibit melanoma cell migration in vitro.

A sulfated disaccharide derived from chondroitin sulfate proteoglycan protects against inflammation-associated neurodegeneration.

Chondroitin sulfate proteoglycan (CSPG), a matrix protein that occurs naturally in the central nervous system (CNS), is considered to be a major inhibitor of axonal regeneration and is known to participate in activation of the inflammatory response. The degradation of CSPG by a specific enzyme, chondroitinase ABC, promotes repair. We postulated that a disaccharidic degradation product of this glycoprotein (CSPG-DS), generated following such degradation, participates in the modulation of the inflammatory responses and can, therefore, promote recovery in immune-induced neuropathologies of the CNS, such as experimental autoimmune encephalomyelitis (EAE) and experimental autoimmune uveitis (EAU). In these pathologies, the dramatic increase in T cells infiltrating the CNS is far in excess of the numbers needed for regular maintenance. Here, we show that CSPG-DS markedly alleviated the clinical symptoms of EAE and protected against the neuronal loss in EAU. The last effect was associated with a reduction in the numbers of infiltrating T cells and marked microglia activation. This is further supported by our in vitro results indicating that CSPG-DS attenuated T cell motility and decreased secretion of the cytokines interferon-gamma and tumor necrosis factor-alpha. Mechanistically, these effects are associated with an increase in SOCS-3 levels and a decrease in NF-kappaB. Our results point to a potential therapeutic modality, in which a compound derived from an endogenous CNS-resident molecule, known for its destructive role in CNS recovery, might be helpful in overcoming inflammation-induced neurodegenerative conditions.