Canine olfactory ensheathing cells from the olfactory mucosa can be engineered to produce active chondroitinase ABC

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.

Gut microbiota and traumatic central nervous system injuries: Insights into pathophysiology and therapeutic approaches

Traumatic brain injury and spinal cord injury are two distinct but fundamentally similar types of acute insults to the central nervous system (CNS) that often culminate in death or cognitive and motor impairment. Over the past decade, researchers have tapped into research to discover the potential role being played by gut bacteria in CNS. After an acute CNS injury, the altered composition of the gut microbiota disturbs the balance of the bidirectional gut-brain axis, aggravating secondary CNS injury, motor dysfunctions, and cognitive deficits, which worsens the patient's prognosis. Some of the well-known therapeutic interventions which can also be used as adjuvant therapy for alleviating CNS injuries include, the use of pro and prebiotics, fecal microbiota transplantation, and microbial engineering. In this review, we aim to discuss the importance of gut microbes in our nervous system, anatomy, and signaling pathways involved in regulating the gut-brain axis, the alteration of the gut microbiome in CNS injuries, and the therapeutic strategies to target gut microbiomes in traumatic CNS injuries.

Transplantation of encapsulated autologous olfactory ensheathing cell populations expressing chondroitinase for spinal cord injury: A safety and feasibility study in companion dogs

Spinal cord injury (SCI) can cause irreversible paralysis, with no regenerative treatment clinically available. Dogs with natural SCI present an established model and can facilitate translation of experimental findings in rodents to people. We conducted a prospective, single arm clinical safety study in companion dogs with chronic SCI to characterize the feasibility of intraspinal transplantation of hydrogel-encapsulated autologous mucosal olfactory ensheathing cell (mOEC) populations expressing chondroitinase ABC (chABC). mOECs and chABC are both promising therapies for SCI, and mOECs expressing chABC drive greater voluntary motor recovery than mOECs alone after SCI in rats. Canine mOECs encapsulated in collagen hydrogel can be matched in stiffness to canine SCI. Four dogs with complete and chronic loss of function caudal to a thoraco-lumbar lesion were recruited. After baseline measures, olfactory mucosal biopsy was performed and autologous mOECs cultured and transduced to express chABC, then hydrogel-encapsulated and percutaneously injected into the spinal cord. Dogs were monitored for 6 months with repeat clinical examinations, spinal MRI, kinematic gait and von Frey assessment. No adverse effects or significant changes on neurological examination were detected. MRI revealed large and variable lesions, with no spinal cord compression or ischemia visible after hydrogel transplantation. Owners reported increased pelvic-limb reflexes with one dog able to take 2-3 unsupported steps, but gait-scoring and kinematic analysis showed no significant improvements. This novel combination approach to regeneration after SCI is therefore feasible and safe in paraplegic dogs in a clinical setting. A randomised-controlled trial in this translational model is proposed to test efficacy.

Delivery of chondroitinase by canine mucosal olfactory ensheathing cells alongside rehabilitation enhances recovery after spinal cord injury

Spinal cord injury (SCI) can cause chronic paralysis and incontinence and remains a major worldwide healthcare burden, with no regenerative treatment clinically available. Intraspinal transplantation of olfactory ensheathing cells (OECs) and injection of chondroitinase ABC (chABC) are both promising therapies but limited and unpredictable responses are seen, particularly in canine clinical trials. Sustained delivery of chABC presents a challenge due to its thermal instability; we hypothesised that transplantation of canine olfactory mucosal OECs genetically modified ex vivo by lentiviral transduction to express chABC (cOEC-chABC) would provide novel delivery of chABC and synergistic therapy. Rats were randomly divided into cOEC-chABC, cOEC, or vehicle transplanted groups and received transplant immediately after dorsal column crush corticospinal tract (CST) injury. Rehabilitation for forepaw reaching and blinded behavioural testing was conducted for 8 weeks. We show that cOEC-chABC transplanted animals recover greater forepaw reaching accuracy on Whishaw testing and more normal gait than cOEC transplanted or vehicle control rats. Increased CST axon sprouting cranial to the injury and serotonergic fibres caudal to the injury suggest a mechanism for recovery. We therefore demonstrate that cOECs can deliver sufficient chABC to drive modest functional improvement, and that this genetically engineered cellular and molecular approach is a feasible combination therapy for SCI.

Stiffness-matched biomaterial implants for cell delivery: clinical, intraoperative ultrasound elastography provides a 'target' stiffness for hydrogel synthesis in spinal cord injury

Safe hydrogel delivery requires stiffness-matching with host tissues to avoid iatrogenic damage and reduce inflammatory reactions. Hydrogel-encapsulated cell delivery is a promising combinatorial approach to spinal cord injury therapy, but a lack of in vivo clinical spinal cord injury stiffness measurements is a barrier to their use in clinics. We demonstrate that ultrasound elastography – a non-invasive, clinically established tool – can be used to measure spinal cord stiffness intraoperatively in canines with spontaneous spinal cord injury. In line with recent experimental reports, our data show that injured spinal cord has lower stiffness than uninjured cord. We show that the stiffness of hydrogels encapsulating a clinically relevant transplant population (olfactory ensheathing cells) can also be measured by ultrasound elastography, enabling synthesis of hydrogels with comparable stiffness to canine spinal cord injury. We therefore demonstrate proof-of-principle of a novel approach to stiffness-matching hydrogel-olfactory ensheathing cell implants to ‘real-life’ spinal cord injury values; an approach applicable to multiple biomaterial implants for regenerative therapies.

Protein Degradome of Spinal Cord Injury: Biomarkers and Potential Therapeutic Targets

Degradomics is a proteomics sub-discipline whose goal is to identify and characterize protease-substrate repertoires. With the aim of deciphering and characterizing key signature breakdown products, degradomics emerged to define encryptic biomarker neoproteins specific to certain disease processes. Remarkable improvements in structural and analytical experimental methodologies as evident in research investigating cellular behavior in neuroscience and cancer have allowed the identification of specific degradomes, increasing our knowledge about proteases and their regulators and substrates along with their implications in health and disease. A physiologic balance between protein synthesis and degradation is sought with the activation of proteolytic enzymes such as calpains, caspases, cathepsins, and matrix metalloproteinases. Proteolysis is essential for development, growth, and regeneration; however, inappropriate and uncontrolled activation of the proteolytic system renders the diseased tissue susceptible to further neurotoxic processes. In this article, we aim to review the protease-substrate repertoires as well as emerging therapeutic interventions in spinal cord injury at the degradomic level. Several protease substrates and their breakdown products, essential for the neuronal structural integrity and functional capacity, have been characterized in neurotrauma including cytoskeletal proteins, neuronal extracellular matrix glycoproteins, cell junction proteins, and ion channels. Therefore, targeting exaggerated protease activity provides a potentially effective therapeutic approach in the management of protease-mediated neurotoxicity in reducing the extent of damage secondary to spinal cord injury.

Safe nanoengineering and incorporation of transplant populations in a neurosurgical grade biomaterial, DuraGen PlusTM, for protected cell therapy applications

High transplant cell loss is a major barrier to translation of stem cell therapy for pathologies of the brain and spinal cord. Encapsulated delivery of stem cells in biomaterials for cell therapy is gaining popularity but experimental research has overwhelmingly used laboratory grade materials unsuitable for human clinical use - representing a further barrier to clinical translation. A potential solution is to use neurosurgical grade materials routinely used in clinical protocols which have an established human safety profile. Here, we tested the ability of Duragen Plus™ - a clinical biomaterial used widely in neurosurgical duraplasty procedures, to support the growth and differentiation of neural stem cells- a major transplant population being tested in clinical trials for neurological pathology. Genetic engineering of stem cells yields augmented therapeutic cells, so we further tested the ability of the Duragen Plus™ matrix to support stem cells engineered using magnetofection technology and minicircle DNA vectors- a promising cell engineering approach we previously reported (Journal of Controlled Release, 2016 a &b). The safety of the nano-engineering approach was analysed for the first time using sophisticated data-independent analysis by mass spectrometry-based proteomics. We prove that the Duragen Plus™ matrix is a promising biomaterial for delivery of stem cell transplant populations, with no adverse effects on key regenerative parameters. This advanced cellular construct based on a combinatorial nano-engineering and biomaterial encapsulation approach, could therefore offer key advantages for clinical translation.

Inhibition of ADAMTS-4 Expression in Olfactory Ensheathing Cells Enhances Recovery after Transplantation within Spinal Cord Injury

Spinal cord injury (SCI) induces permanent loss of sensitive and motor functions below the injury level. To date, a wide variety of cells has been used as biotherapies to cure SCI in different animal paradigms. Specifically, olfactory ensheathing cells (OECs) is one of the most promising. Indeed, OECs have been shown to enhance recovery in many animal studies. Moreover, OECs transplantation has been applied to a paraplegic patient and have shown beneficial effects. However, it has been reported that the significant level of recovery varies among different patients. Therefore, it is of primary importance to enhance the regenerative efficiency of OECs for better translations. Recently, it has been shown that inhibiting ADAMTS4 expression in glial cells in vitro increases their synthesis of neurotrophic factors. We hypothesized that the expression of neurotrophic factors secreted by OECs can be increased by the deletion of ADAMTS4. Taking advantage of ADAMTS4^-/- mouse line, we produce ADAMTS4 deficient primary OEC cultures and then we investigated their regenerative potential after SCI. By using quantitative polymerase chain reaction, bioluminescence imaging, measurement of locomotor activity, electrophysiological studies, and immunohistochemistry, our results show that ADAMTS4^-/- olfactory bulb OEC (bOECs) primary cultures upregulate their trophic factor expression in vitro, and that the transplantation of ADAMTS4^-/- bOECs in a severe SCI model increases functional recovery and tissue repair in vivo. Altogether, our study reveals, for the first time, that primary bOEC cultures transplantation can be potentialized by inhibition of the expression of ADAMTS4.

Transplantation of canine olfactory ensheathing cells producing chondroitinase ABC promotes chondroitin sulphate proteoglycan digestion and axonal sprouting following spinal cord injury

Olfactory ensheathing cell (OEC) transplantation is a promising strategy for treating spinal cord injury (SCI), as has been demonstrated in experimental SCI models and naturally occurring SCI in dogs. However, the presence of chondroitin sulphate proteoglycans within the extracellular matrix of the glial scar can inhibit efficient axonal repair and limit the therapeutic potential of OECs. Here we have used lentiviral vectors to genetically modify canine OECs to continuously deliver mammalian chondroitinase ABC at the lesion site in order to degrade the inhibitory chondroitin sulphate proteoglycans in a rodent model of spinal cord injury. We demonstrate that these chondroitinase producing canine OECs survived at 4 weeks following transplantation into the spinal cord lesion and effectively digested chondroitin sulphate proteoglycans at the site of injury. There was evidence of sprouting within the corticospinal tract rostral to the lesion and an increase in the number of corticospinal axons caudal to the lesion, suggestive of axonal regeneration. Our results indicate that delivery of the chondroitinase enzyme can be achieved with the genetically modified OECs to increase axon growth following SCI. The combination of these two promising approaches is a potential strategy for promoting neural regeneration following SCI in veterinary practice and human patients.

A fusion of minicircle DNA and nanoparticle delivery technologies facilitates therapeutic genetic engineering of autologous canine olfactory mucosal cells

Olfactory ensheathing cells (OECs) promote axonal regeneration and improve locomotor function when transplanted into the injured spinal cord. A recent clinical trial demonstrated improved motor function in domestic dogs with spinal injury following autologous OEC transplantation. Their utility in canines offers promise for human translation, as dogs are comparable to humans in terms of clinical management and genetic/environmental variation. Moreover, the autologous, minimally invasive derivation of OECs makes them viable for human spinal injury investigation. Genetic engineering of transplant populations may augment their therapeutic potential, but relies heavily on viral methods which have several drawbacks for clinical translation. We present here the first proof that magnetic particles deployed with applied magnetic fields and advanced DNA minicircle vectors can safely bioengineer OECs to secrete a key neurotrophic factor, with an efficiency approaching that of viral vectors. We suggest that our alternative approach offers high translational potential for the delivery of augmented clinical cell therapies.