Combination of Chondroitinase ABC, Glial Cell Line–Derived Neurotrophic Factor and Nogo A Antibody Delayed-Release Microspheres Promotes the Functional Recovery of Spinal Cord Injury

Chondroitinase as a therapeutic enzyme: Prospects and challenges

The chondroitinases (Chase) are bacterial lyases that specifically digest chondroitin sulfate and/or dermatan sulfate glycosaminoglycans via a β-elimination reaction and generate unsaturated disaccharides. In recent decades, these enzymes have attracted the attention of many researchers due to their potential applications in various aspects of medicine from the treatment of spinal cord injury to use as an analytical tool. In spite of this diverse spectrum, the application of Chase is faced with several limitations and challenges such as thermal instability and lack of a suitable delivery system. In the current review, we address potential therapeutic applications of Chase with emphasis on the challenges ahead. Then, we summarize the latest achievements to overcome the problems by considering the studies carried out in the field of enzyme engineering, drug delivery, and combination-based therapy.

Combined RhoA morpholino and ChABC treatment protects identified lamprey neurons from retrograde apoptosis after spinal cord injury

Previously, we reported that RhoA knockdown by morpholino antisense oligonucleotides (MOs), and enzymatic digestion of chondroitin sulfate proteoglycans (CSPGs) at the site of injury with chondroitinase ABC (ChABC), each can reduce retrograde neuronal apoptosis after spinal cord transection in the lamprey. To elucidate the mechanisms in neuronal survival and axon regeneration, we have investigated whether these two effects are additive in vivo. We used lampreys as a spinal cord injury model. MOs were used to knockdown RhoA and Chondroitinase ABC (ChABC) was used to digest CSPGs in vivo. Retrograde labeling, fluorochrome-labeled inhibitor of caspase activity (FLICA), immunohistochemistry, and western blots were performed to assess axonal regeneration, neuronal apoptotic signaling and Akt activation. Four treatment combinations were evaluated at 2-, 4-, and 10-weeks post-transection: (1) Control MO plus enzyme buffer (Ctrl); (2) control MO plus ChABC; (3) RhoA MO plus enzyme buffer (RhoA MO); and (4) RhoA MO plus ChABC (RhoA MO + ChABC). Consistent with our previous findings, at 4-weeks post-transection, there was less caspase activation in the ChABC and RhoA MO groups than in the Ctrl group. Moreover, the RhoA MO plus ChABC group had the best protective effect on identified reticulospinal (RS) neurons among the four treatment combinations. At 2 weeks post-transection, when axons have retracted maximally in the rostral stump and are beginning to regenerate back toward the lesion, the axon tips in the three treatment groups each were closer to the transection than those in the Ctr MO plus enzyme buffer group. Long-term axon regeneration also was evaluated for the large, individually identified RS neurons at 10 weeks post-transection by retrograde labeling. The percent regenerated axons in the RhoA MO plus ChABC group was greater than that in any of the other groups. Akt phosphorylation levels at threonine 308 was quantified in the identified RS neurons by western blots and immunofluorescence. The RhoA MO plus ChABC treatment enhanced pAkt-308 phosphorylation more than any of the other treatment groups. Although some of the effects of CSPGs are mediated through RhoA activation, some growth-inhibiting mechanisms of RhoA and CSPGs are independent of each other, so combinatorial therapies may be warranted.

Axonal growth inhibitors and their receptors in spinal cord injury: from biology to clinical translation

Axonal growth inhibitors are released during traumatic injuries to the adult mammalian central nervous system, including after spinal cord injury. These molecules accumulate at the injury site and form a highly inhibitory environment for axonal regeneration. Among these inhibitory molecules, myelin-associated inhibitors, including neurite outgrowth inhibitor A, oligodendrocyte myelin glycoprotein, myelin-associated glycoprotein, chondroitin sulfate proteoglycans and repulsive guidance molecule A are of particular importance. Due to their inhibitory nature, they represent exciting molecular targets to study axonal inhibition and regeneration after central injuries. These molecules are mainly produced by neurons, oligodendrocytes, and astrocytes within the scar and in its immediate vicinity. They exert their effects by binding to specific receptors, localized in the membranes of neurons. Receptors for these inhibitory cues include Nogo receptor 1, leucine-rich repeat, and Ig domain containing 1 and p75 neurotrophin receptor/tumor necrosis factor receptor superfamily member 19 (that form a receptor complex that binds all myelin-associated inhibitors), and also paired immunoglobulin-like receptor B. Chondroitin sulfate proteoglycans and repulsive guidance molecule A bind to Nogo receptor 1, Nogo receptor 3, receptor protein tyrosine phosphatase σ and leucocyte common antigen related phosphatase, and neogenin, respectively. Once activated, these receptors initiate downstream signaling pathways, the most common amongst them being the RhoA/ROCK signaling pathway. These signaling cascades result in actin depolymerization, neurite outgrowth inhibition, and failure to regenerate after spinal cord injury. Currently, there are no approved pharmacological treatments to overcome spinal cord injuries other than physical rehabilitation and management of the array of symptoms brought on by spinal cord injuries. However, several novel therapies aiming to modulate these inhibitory proteins and/or their receptors are under investigation in ongoing clinical trials. Investigation has also been demonstrating that combinatorial therapies of growth inhibitors with other therapies, such as growth factors or stem-cell therapies, produce stronger results and their potential application in the clinics opens new venues in spinal cord injury treatment.

A systematic review and meta-analysis of chondroitinase ABC promotes functional recovery in rat models of spinal cord injury

BACKGROUND

To comprehensively assess the neurologic recovery potential of chondroitinase ABC (ChABC) in rats after spinal cord injury (SCI).

METHODS

The PubMed, Embase, ScienceDirect, Web of Science, and China National Knowledge Infrastructure databases were searched for animal experiments that evaluated the use of ChABC in the treatment of SCI up to November 2022. Studies reporting neurological function using the Basso, Beattie, and Bresnahan (BBB) scale, as well as assessments of cavity area, lesion area, and glial fibrillary acidic protein (GFAP) levels, were included in the analysis.

RESULTS

A total of 46 studies were ultimately selected for inclusion. The results of the study showed that rats with SCI that received ChABC therapy exhibited a significant improvement in locomotor function after 7 days compared with controls (32 studies, weighted mean difference (WMD) = 0.58, [0.33, 0.83], p < 0.00001). Furthermore, the benefits of ChABC therapy were maintained for up to 28 days according to BBB scale. The lesion area was reduced by ChABC (5 studies, WMD = -20.94, [-28.42, -13.46], p < 0.00001). Meanwhile, GFAP levels were reduced in the ChABC treatment group (8 studies, WMD = -29.15, [-41.57, -16.72], p < 0.00001). Cavity area is not statistically significant. The subgroup analysis recommended that a single injection of 10 μL (8 studies, WMD = 2.82, [1.99, 3.65], p < 0.00001) or 20 U/mL (4 studies, WMD = 2.21, [0.73, 3.70], p = 0.003) had a better effect on improving the function. The funnel plot of the BBB scale was found to be essentially symmetrical, indicating a low risk of publication bias.

CONCLUSIONS

This systematic review and meta-analysis has indicated that ChABC could improve functional recovery in rats after SCI.

Sustained delivery of chABC improves functional recovery after a spine injury

INTRODUCTION

Chondroitinase ABC (chABC) is an enzyme could improve regeneration and thereby improving functional recovery of spinal cord injury (SCI) in rodent models. Degradation of the active enzyme and diffusion away from the lesion are the causes of using hydrogels as a scaffold to deliver the chABC into the lesion site. In this meta-analysis, we investigated the effects of chABC embedded in a scaffold or hydrogel on the functional recovery after SCI.

METHOD

Databases were searched based on keywords related to chABC and spinal cord injury (SCI). Primary and secondary screening was performed to narrow down study objectives and inclusion criteria, and finally the data were included in the meta-analysis. The standard mean difference of the score of the functional recovery that measured by Basso, Beattie, Bresnahan (BBB) test after SCI was used to analyze the results of the reported studies. Subgroup analysis was performed based on SCI model, severity of SCI, transplantation type, and the follow-up time. Quality control of articles was also specified.

RESULTS

The results showed that embedding chABC within the scaffold increased significantly the efficiency of functional recovery after SCI in animal models (SMD = 1.95; 95% CI 0.71-3.2; p = 0.002) in 9 studies. SCI model, severity of SCI, injury location, transplantation type, and the follow-up time did not affect the overall results and in all cases scaffold effect could not be ignored. However, due to the small number of studies, this result is not conclusive and more studies are needed.

CONCLUSION

The results could pave the way for the use of chABC embedded in the scaffold for the treatment of SCI and show that this method of administration is superior to chABC injection alone.

Growth Factor Gene-Modified Cells in Spinal Cord Injury Recovery; a Systematic Review

BACKGROUND

Numerous pre-clinical studies have been performed in recent years on the effects of growth factor gene-modified cells' administration in spinal cord injury (SCI). However, findings of these studies are contradictory.

OBJECTIVE

The present study aims to conduct a systematic review and meta-analysis on animal studies evaluating the effects of growth factor gene-modified cells' administration on locomotion recovery following SCI.

METHODS

A search of the Medline, Embase, Scopus and Web of Science databases was conducted, including all animal studies until the end of 2020. Two researchers screened search results, summarized relevant studies and assessed risk of bias, independently.

RESULTS

Thirty-three studies were included in the final analysis. Transplantation of growth factor gene-modified cells in the injured spinal cord resulted in a significant improvement in animals' locomotion compared with non-treated animals [standardized mean difference (SMD)=1.86; 95% CI: 1.39-2.33; p<0.0001)] and non-genetically modified cells treated animals (SMD=1.30; 0.80-1.79; p<0.0001). Transplantation efficacy of these cells failed to achieve significance in moderate lesions (p=0.091), when using modified neural stem/progenitor cells (p=0.164), when using synthetic neurotrophins (p=0.086) and when the number of transplanted cells was less than 1.0 × 10⁵ cells per animal (p = 0.119).

CONCLUSION

The result showed that transplantation of growth factor gene-modified cells significantly improved locomotion in SCI animal models. However, there is a major concern regarding the safety of genetically modified cells' transplantation, in terms of overexpressing growth factors. Further studies are needed before any effort to perform a translational and clinical study.

Combining timed GDNF and ChABC gene therapy to promote long-distance regeneration following ventral root avulsion and repair

Ventral root avulsion leads to severe motoneuron degeneration and prolonged distal nerve denervation. After a critical period, a state of chronic denervation develops as repair Schwann cells lose their pro-regenerative properties and inhibitory factors such as CSPGs accumulate in the denervated nerve. In rats with ventral root avulsion injuries, we combined timed GDNF gene therapy delivered to the proximal nerve roots with the digestion of inhibitory CSPGs in the distal denervated nerve using sustained lentiviral-mediated chondroitinase ABC (ChABC) enzyme expression. Following reimplantation of lumbar ventral roots, timed GDNF-gene therapy enhanced motoneuron survival up to 45 weeks and improved axonal outgrowth, electrophysiological recovery, and muscle reinnervation. Despite a timed GDNF expression period, a subset of animals displayed axonal coils. Lentiviral delivery of ChABC enabled digestion of inhibitory CSPGs for up to 45 weeks in the chronically denervated nerve. ChABC gene therapy alone did not enhance motoneuron survival, but led to improved muscle reinnervation and modest electrophysiological recovery during later stages of the regeneration process. Combining GDNF treatment with digestion of inhibitory CSPGs did not have a significant synergistic effect. This study suggests a delicate balance exists between treatment duration and concentration in order to achieve therapeutic effects.

Recent advances in the therapeutic uses of chondroitinase ABC

Many studies, using pre-clinical models of SCI, have demonstrated the efficacy of chondroitinase ABC as a treatment for spinal cord injury and this has been confirmed in laboratories worldwide and in several animal models. The aim of this review is report the current state of research in the field and to compare the relative efficacies of these new interventions to improve outcomes in both acute and chronic models of SCI. We also report new methods of chondroitinase delivery and the outcomes of two clinical trials using the enzyme to treat spinal cord injury in dogs and disc herniation in human patients. Recent studies have assessed the outcomes of combining chondroitinase with other strategies known to promote recovery following spinal cord injury and new approaches. Evidence is emerging that one of the most powerful combinations is that of chondroitinase with cell transplants. The particular benefits of each of the different cell types used for these transplant experiments are discussed. Combining chondroitinase with rehabilitation also improves outcomes. Gene therapy is an efficient method of enzyme delivery to the injured spinal cord and circumvents the issue of the enzyme's thermo-instability. Other methods of delivery, such as via nanoparticles or synthetic scaffolds, have shown promise; however, the outcomes from these experiments suggest that these methods of delivery require further optimization to achieve similar levels of efficacy to that obtained by a gene therapy approach. Pre-clinical models have also shown chondroitinase is efficacious in the treatment of other conditions, such as peripheral nerve injury, stroke, coronary reperfusion, Parkinson's disease and certain types of cancer. The wide range of conditions where the benefits of chondroitinase treatment have been demonstrated reflects the complex roles that chondroitin sulphate proteoglycans (its substrate) play in health and disease and warrants the enzyme's further development as a therapy.

Novel multi-drug delivery hydrogel using scar-homing liposomes improves spinal cord injury repair

Proper selection and effective delivery of combination drugs targeting multiple pathophysiological pathways key to spinal cord injury (SCI) hold promise to address the thus far scarce clinical therapeutics for improving recovery after SCI. In this study, we aim to develop a clinically feasible way for targeted delivery of multiple drugs with different physiochemical properties to the SCI site, detail the underlying mechanism of neural recovery, and detect any synergistic effect related to combination therapy.

Methods: Liposomes (LIP) modified with a scar-targeted tetrapeptide (cysteine-alanine-glutamine-lysine, CAQK) were first constructed to simultaneously encapsulate docetaxel (DTX) and brain-derived neurotrophic factor (BDNF) and then were further added into a thermosensitive heparin-modified poloxamer hydrogel (HP) with affinity-bound acidic fibroblast growth factor (aFGF-HP) for local administration into the SCI site (CAQK-LIP-GFs/DTX@HP) in a rat model. In vivo fluorescence imaging was used to examine the specificity of CAQK-LIP-GFs/DTX binding to the injured site. Multiple comprehensive evaluations including biotin dextran amine anterograde tracing and magnetic resonance imaging were used to detect any synergistic effects and the underlying mechanisms of CAQK-LIP-GFs/DTX@HP both in vivo (rat SCI model) and in vitro (primary neuron).

Results: The multiple drugs were effectively delivered to the injured site. The combined application of GFs and DTX supported neuro-regeneration by improving neuronal survival and plasticity, rendering a more permissive extracellular matrix environment with improved regeneration potential. In addition, our combination therapy promoted axonal regeneration via moderation of microtubule function and mitochondrial transport along the regenerating axon.

Conclusion: This novel multifunctional therapeutic strategy with a scar-homing delivery system may offer promising translational prospects for the clinical treatment of SCI.

History of Glial Cell Line-Derived Neurotrophic Factor (GDNF) and Its Use for Spinal Cord Injury Repair

Following an initial mechanical insult, traumatic spinal cord injury (SCI) induces a secondary wave of injury, resulting in a toxic lesion environment inhibitory to axonal regeneration. This review focuses on the glial cell line-derived neurotrophic factor (GDNF) and its application, in combination with other factors and cell transplantations, for repairing the injured spinal cord. As studies of recent decades strongly suggest that combinational treatment approaches hold the greatest therapeutic potential for the central nervous system (CNS) trauma, future directions of combinational therapies will also be discussed.

Chondroitinase ABC for neurological recovery after acute brain injury: systematic review and meta-analyses of preclinical studies

OBJECTIVES

Damage to critical brain regions causes deficits in important neurological functions. Chondroitinase ABC (ChABC) has been shown to promote neuroplasticity and may ameliorate neurological deficits caused by disease or trauma. This systematic review identifies and evaluates preclinical studies of ChABC as a treatment for acute brain injury.

METHODS

Four databases were searched for studies relating to ChABC and brain or brain injuries. Controlled studies in mammals with acute brain injuries treated with ChABC were included in meta-analyses of neurobehavioural outcomes. Means and standard deviations from the fifth day of treatment were extracted, and normalised mean differences were calculated.

RESULTS

Of 775 identified records, 16 studies administered ChABC after acute brain injury, of which 9 reported neurobehavioural outcomes. The estimated treatment effect on neurological recovery over the duration of included studies was 49.4% (CI: 30.3-68.4% with Hartung-Knapp-Sidik-Jonkman adjustment, p = 0.0002). The mechanisms of action may involve decreasing astroglial scar formation, promoting neuronal sprouting, and selective synaptic strengthening of sprouting neurites and activated neural pathways.

CONCLUSIONS

The summary of published evidence suggests that ChABC treatment is effective in improving neurological outcomes in preclinical models of acute brain injury. However, more studies are needed for better assessment of the specific translational potential of ChABC.

ABBREVIATIONS

AVM - Arteriovenous Malformation; ChABC - Chondroitinase ABC; CI - Confidence Interval; CSPG - Chondroitin Sulphate Proteoglycans; HKSJ - Hartung-Knapp-Sidik-Jonkman; MCA - Middle Cerebral Artery; NMD - Normalised Mean Difference; NSPC - Neural Stem/Progenitor Cells; PI - Prediction Interval; SD - Standard Deviation; SMD - Standardised Mean Difference; TBI - Traumatic Brain Injury.

Impact of treatment duration and lesion size on effectiveness of chondroitinase treatment post-SCI

The effects of 2weeks of intralesional chondroitinase abc (ch'abc) treatment on anatomical plasticity and behavioral recovery are examined in adult cats and compared to results achieved with 4weeks of treatment following tightly controlled lateral hemisection injuries. Analyses also were completed using 35 cats with a range of hemisection magnitudes to assess relationships between treatment duration, lesion size and functional recovery. Results indicate that both 2 and 4weeks of treatment significantly increased the number of rubrospinal tract (RuST) neurons with axons below the lesion, but neither affected the number of corticospinal tract neurons. Similarly, both treatment periods also accelerated recovery of select motor tasks, which carries considerable importance with respect to human health care and rehabilitation. Four weeks of treatment promoted recovery beyond that seen with 2weeks in its significant impact on accuracy of movement critical for placement of the ipsilateral hindlimb onto small support surfaces during the most challenging locomotor tasks. Analyses, which extended to a larger group of cats with a range of lesion magnitudes, indicate that 4weeks of ch'abc treatment promoted earlier recovery as well as significantly greater targeting accuracy even in cats with larger lesions. Together, these results support the potential for ch'abc to promote anatomical and behavioral recovery and suggest that intraspinal treatment with ch'abc continues to enhance motor recovery and performance beyond the subacute injury period and diminishes the impact of lesion size.