Glial scar-modulation as therapeutic tool in spinal cord injury in animal models

Astroglial Cells: Emerging Therapeutic Targets in the Management of Traumatic Brain Injury

Traumatic Brain Injury (TBI) represents a significant health concern, necessitating advanced therapeutic interventions. This detailed review explores the critical roles of astrocytes, key cellular constituents of the central nervous system (CNS), in both the pathophysiology and possible rehabilitation of TBI. Following injury, astrocytes exhibit reactive transformations, differentiating into pro-inflammatory (A1) and neuroprotective (A2) phenotypes. This paper elucidates the interactions of astrocytes with neurons, their role in neuroinflammation, and the potential for their therapeutic exploitation. Emphasized strategies encompass the utilization of endocannabinoid and calcium signaling pathways, hormone-based treatments like 17β-estradiol, biological therapies employing anti-HBGB1 monoclonal antibodies, gene therapy targeting Connexin 43, and the innovative technique of astrocyte transplantation as a means to repair damaged neural tissues.

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.

Treatment of Chronic Spinal Cord Injury in Dogs Using Amniotic Membrane-Derived Stem Cells: Preliminary Results

Introduction

Intervertebral disc diseases (IVDD) represent the majority of neurological attendance and responsible for the most cases of paralysis in dogs. Treatments currently used do not show satisfactory results in patients with more severe and chronic neurological manifestations.

Methods

To promote nerve and muscular recovery, as well as improve quality of life, we aimed to create a double-blind test method, associating spinal decompression surgery and allogeneic transplantation of amniotic membrane-derived stem cells (AMSCs) in dogs with chronic IVDD. Cells were characterized as fetal mesenchymal cells and safe for application. Eight animals completed the experiment: stem cell applications were made in four animals that had previously undergone an unsuccessful surgical procedure (“SC group”, n = 4); two animals were submitted to surgery, followed by applications of stem cells (“Surgery + SC”, n = 2); two other animals were submitted to surgery, followed by the application of saline solution (“Surgery + placebo”, n = 2). During the surgical procedure, a topical application was performed on the lesion and after fifteen and forty-five days another two applications were made via epidural. Animals were monitored biweekly and reassessed three months after surgery, by functional tests and magnetic resonance exams.

Results

Some animals presented significant neurological improvement, such as the recovery of nociception and ability to remain on station. Despite the need further studies, until the present moment, cell therapy has been feasible and has no harmful effects on animals.

Conclusion

The protocol of preclinical trial showed the association with decompressive surgery and cell transplantation in dogs with thoracolumbar IVDD proved feasible, and it was possible to observe neurological improvement after treatment. No tissue improvement through MRI was found. The double-blind test guaranteed reliability of the evaluations and results obtained that, even with a small sample size, generated satisfactory results for the animals and owners.

A New Precision Minimally Invasive Method of Glial Scar Simulation in the Rat Spinal Cord Using Cryoapplication

According to the World Health Organization, every year worldwide up to 500,000 people suffer a spinal cord injury (SCI). Various animal biomodels are essential for searching for novel protocols and therapeutic approaches for SCI treatment. We have developed an original model of post-traumatic spinal cord glial scarring in rats through cryoapplication. With this method the low-temperature liquid nitrogen is used for the cryodestruction of the spinal cord tissue. Forty-five Sprague Dawley (SD) non-linear male rats of the Specific-pathogen-free (SPF) category were included in this experimental study. A Th13 unilateral hemilaminectomy was performed with dental burr using an operating microscope. A specifically designed cryogenic probe was applied to the spinal cord for one minute through the created bone defect. The animals were euthanized at different time points ranging from 1 to 60 days after cold-induced injury. Their Th12-L1 vertebrae with the injured spinal cord region were removed "en bloc" for histological examination. Our data demonstrate that cryoapplication producing a topical cooling around-20°C, caused a highly standardized transmural lesion of the spinal cord in the dorsoventral direction. The lesion had an "hour-glass" shape on histological sections. During the entire study period (days 1-60 of the post-trauma period), the necrotic processes and the development of the glial scar (lesion evolution) were contained in the surgically approached vertebral space (Th13). Unlike other known experimental methods of SCI simulation (compression, contusion, etc.), the proposed technique is characterized by minimal invasiveness, high precision, and reproducibility. Also, histological findings, lesion size, and postoperative clinical course varied only slightly between different animals. An original design of the cryoprobe used in the study played a primary role in the achieving of these results. The spinal cord lesion's detailed functional morphology is described at different time points (1-60 days) after the produced cryoinjury. Also, changes in the number of macrophages at distinct time points, neoangiogenesis and the formation of the glial scar's fibrous component, including morphodynamic characteristics of its evolution, are analyzed. The proposed method of cryoapplication for inducing reproducible glial scars could facilitate a better understanding of the self-recovery processes in the damaged spinal cord. It would be evidently helpful for finding innovative approaches to the SCI treatment.

Stem Cell Therapy for Neurogenic Bladder Dysfunction in Rodent Models: A Systematic Review

PURPOSE

Neurogenic bladder dysfunction (NGB) has an impact on the quality of life, which made it an important research subject in preclinical studies. The present review investigates the effect of stem cell (SC) therapy on bladder functional recovery after the onset of spinal cord injury (SCI), multiple sclerosis (MS), Parkinson disease (PD), and stroke in rodent models.

METHODS

All experiments evaluated the regenerative potential of SC on the management of NGB in rodent models up to June 2019, were included. From 1,189 relevant publications, 20 studies met our inclusion criteria of which 15 were conducted on SCI, 2 on PD, 2 on stroke, and 1 on MS in the rodent models. We conducted a meta-analysis on SCI experiments and for other neurological diseases, detailed urodynamic findings were reported.

RESULTS

The common SC sources used for therapeutical purposes were neural progenitor cells, bone marrow mesenchymal SCs, human amniotic fluid SCs, and human umbilical cord blood SCs. There was a significant improvement of micturition pressure in both contusion and transaction SCI models 4 and 8 weeks post-SC transplantation. Residual urine volume, micturition volume, and bladder capacity were improved 28 days after SC transplantation only in the transaction model of SCI. Nonvoiding contraction recovered only in 56 days post-cell transplantation in the contusion model.

CONCLUSION

Partial bladder recovery has been evident after SC therapy in SCI models. Due to limitations in the number of studies in other neurological diseases, additional studies are necessary to confirm the detailed mechanism for bladder recovery.

Enolase inhibition alters metabolic hormones and inflammatory factors to promote neuroprotection in spinal cord injury

Enolase inhibition is a potential therapeutic strategy currently being investigated for treatment of spinal cord injury (SCI) as it reduces pro-inflammatory cytokines and chemokines, alters metabolic factors, and reduces gliosis in acute SCI. Herein, the role of enolase in SCI has been examined to better understand the effects of this enzyme on inflammation, metabolic hormones, glial cell activation, and neuroprotection under these shorter injury conditions. Immunohistochemical analyses of inflammatory markers vimentin, Cox-2, and caspase-1 indicated that enolase inhibition attenuated the elevated levels of inflammation seen following SCI. Iba1, GFAP, NFP, and CSPG staining indicated that enolase inhibition with prolonged administration of ENOblock reduced microglia/astrocyte activation and lead to enhanced neuroprotection in SCI. An analysis of metabolic hormones revealed that ENOblock treatment significantly upregulated plasma concentrations of peptide YY, glucagon-like peptide 1, glucose-dependent insulinotropic peptide, glucagon, and insulin hormones as compared to vehicle-treated controls (Mann-Whitney, p ≤ 0.05). ENOblock did not have a significant effect on plasma concentrations of pancreatic polypeptide. Interestingly, ENOblock treatment inhibited chondroitin sulfate proteoglycan (CSPG), which is produced by activated glia and serves to block regrowth of axons across the lesion site following injury. An increased level of NeuN and MBP with reduced caspase-1 was detected in SCI tissues after ENOblock treatment, suggesting preservation of myelin and induction of neuroprotection. ENOblock also induced improved motor function in SCI rats, indicating a role for enolase in modulating inflammatory and metabolic factors in SCI with important implications for clinical consideration.

Rosmarinic acid exerts a neuroprotective effect on spinal cord injury by suppressing oxidative stress and inflammation via modulating the Nrf2/HO-1 and TLR4/NF-κB pathways

Spinal cord injury (SCI) is a severe central nervous system injury for which few efficacious drugs are available. Rosmarinic acid (RA), a water-soluble polyphenolic phytochemical, has antioxidant, anti-inflammatory, and anti-apoptotic properties. However, the effect of RA on SCI is unclear. We investigated the therapeutic effect and underlying mechanism of RA on SCI. Using a rat model of SCI, we showed that RA improved locomotor recovery after SCI and significantly mitigated neurological deficit, increased neuronal preservation, and reduced apoptosis. Also, RA inhibited activation of microglia and the release of TNF-α, IL-6, and IL-1β and MDA. Moreover, proteomics analyses identified the Nrf2 and NF-κB pathways as targets of RA. Pretreatment with RA increased levels of Nrf2 and HO-1 and reduced those of TLR4 and MyD88 as well as phosphorylation of IκB and subsequent nuclear translocation of NF-κB-p65. Using H2O2- and LPS-induced PC12 cells, we found that RA ameliorated the H2O2-induced decrease in viability and increase in apoptosis and oxidative injury by activating the Nrf2/HO-1 pathway. Also, LPS-induced cytotoxicity and increased apoptosis and inflammatory injury in PC-12 cells were mitigated by RA by inhibiting the TLR4/NF-κB pathway. The Nrf2 inhibitor ML385 weakened the effect of RA on oxidant stress, inflammation and apoptosis in SCI rats, and significantly increased the nuclear translocation of NF-κB. Therefore, the neuroprotective effect on SCI of RA may be due to its antioxidant and anti-inflammatory properties, which are mediated by modulation of the Nrf2/HO-1 and TLR4/NF-κB pathways. Moreover, RA activated Nrf2/HO-1, which amplified its inhibition of the NF-κB pathway.

Human adipose tissue- and umbilical cord-derived stem cells: which is a better alternative to treat spinal cord injury?

Multiple types of stem cells have been proposed for the treatment of spinal cord injury, but their comparative information remains elusive. In this study, a rat model of T10 contusion spinal cord injury was established by the impactor method. Human umbilical cord-derived mesenchymal stem cells (UCMSCs) or human adipose tissue-derived mesenchymal stem cells (ADMSCs) (2.5 μL/injection site, 1 × 10⁵ cells/μL) was injected on rostral and caudal of the injury segment on the ninth day after injury. Rats injected with mesenchymal stem cell culture medium were used as controls. Our results show that although transplanted UCMSCs and ADMSCs failed to differentiate into neurons or glial cells in vivo, both significantly improved motor and sensory function. After spinal cord injury, UCMSCs and ADMSCs similarly promoted spinal neuron survival and axonal regeneration, decreased glial scar and lesion cavity formation, and reduced numbers of active macrophages. Bio-Plex analysis of spinal samples showed a specific increase of interleukin-10 and decrease of tumor necrosis factor α in the ADMSC group, as well as a downregulation of macrophage inflammatory protein 3α in both UCMSC and ADMSC groups at 3 days after cell transplantation. Upregulation of interleukin-10 and interleukin-13 was observed in both UCMSC and ADMSC groups at 7 days after cell transplantation. Isobaric tagging for relative and absolute quantitation proteomics analyses showed that UCMSCs and ADMSCs induced changes of multiple genes related to axonal regeneration, neurotrophy, and cell apoptosis in common and specific manners. In conclusion, UCMSC and ADMSC transplants yielded quite similar contributions to motor and sensory recovery after spinal cord injury via anti-inflammation and improved axonal growth. However, there were some differences in cytokine and gene expression induced by these two types of transplanted cells. Animal experiments were approved by the Laboratory Animal Ethics Committee at Jinan University (approval No. 20180228026) on February 28, 2018, and the application of human stem cells was approved by the Medical Ethics Committee of Medical College of Jinan University of China (approval No. 2016041303) on April 13, 2016.

Therapeutic Effects of Intravenous Injection of Fresh and Frozen Thawed HO-1-Overexpressed Ad-MSCs in Dogs with Acute Spinal Cord Injury

Owing to the antioxidant and anti-inflammatory functions of hemeoxygenase-1 (HO-1), HO-1-expressing canine adipose-derived mesenchymal stem cells (Ad-MSCs) could be efficacious in treating spinal cord injury (SCI). Further, frozen thawed HO-1 Ad-MSCs could be instantly available as an emergency treatment for SCI. We compared the effects of intravenous treatment with freshly cultured HO-1 Ad-MSCs (HO-1 MSCs), only green fluorescent protein-expressing Ad-MSCs (GFP MSCs), and frozen thawed HO-1 Ad-MSCs (FT-HO-1 MSCs) in dogs with acute SCI. For four weeks, dogs were evaluated for improvement in hind limb locomotion using a canine Basso Beattie Bresnahan (cBBB) score. Upon completion of the study, injured spinal cord segments were harvested and used for western blot and histopathological analyses. All cell types had migrated to the injured spinal cord segment. The group that received HO-1 MSCs showed significant improvement in the cBBB score within four weeks. This group also showed significantly higher expression of NF-M and reduced astrogliosis. There was reduced expression of proinflammatory cytokines (IL6, TNF-α, and IL-1β) and increased expression of anti-inflammatory markers (IL-10, HO-1) in the HO-1 MSC group. Histopathological assessment revealed decreased fibrosis at the epicenter of the lesion and increased myelination in the HO-1 MSC group. Together, these data suggest that HO-1 MSCs could improve hind limb function by increasing the anti-inflammatory reaction, leading to neural sparing. Further, we found similar results between GFP MSCs and FT-HO-1 MSCs, which suggest that FT-HO-1 MSCs could be used as an emergency treatment for SCI.

Improved Healing after the Co-Transplantation of HO-1 and BDNF Overexpressed Mesenchymal Stem Cells in the Subacute Spinal Cord Injury of Dogs

Abundant expression of proinflammatory cytokines after a spinal cord injury (SCI) creates an inhibitory microenvironment for neuroregeneration. The mesenchymal stem cells help to mitigate the inflammation and improve neural growth and survival. For this purpose, we potentiated the function of adipose-derived mesenchymal stem cells (Ad-MSCs) by transfecting them with brain-derived neurotrophic factor (BDNF) and heme oxygenase-1 (HO-1), through a lentivirus, to produce BDNF overexpressed Ad-MSCs (BDNF-MSCs), and HO-1 overexpressed Ad-MSCs (HO-1-MSCs). Sixteen SCI beagle dogs were randomly assigned into four treatment groups. We injected both HO-1 and BDNF-overexpressed MSCs as a combination group, to selectively control inflammation and induce neuroregeneration in SCI dogs, and compared this with BDNF-MSCs, HO-1-MSCs, and GFP-MSCs injected dogs. The groups were compared in terms of improvement in canine Basso, Beattie, and Bresnahan (cBBB) score during 8 weeks of experimentation. After 8 weeks, spinal cords were harvested and subjected to western blot analysis, immunofluorescent staining, and hematoxylin and eosin (H&E) staining. The combination group showed a significant improvement in hindlimb functions, with a higher BBB score, and a robust increase in neuroregeneration, depicted by a higher expression of Tuj-1, NF-M, and GAP-43 due to a decreased expression of the inflammatory markers interleukin-6 (IL-6) and tumor necrosis factor-α (TNF-α), and an increased expression of interleukin-10 (IL-10) (P ≤ 0.05). H&E staining showed more reduced intraparenchymal fibrosis in the combination group than in other groups (P ≤ 0.05). It was thus suggested that the cotransplantation of HO-1 and BDNF-MSCs is more effective in promoting the healing of SCI. HO-1-MSCs reduce inflammation, which favors BDNF-induced neuroregeneration in SCI of dogs.

Transplantation of human immature dental pulp stem cell in dogs with chronic spinal cord injury

Purpose:

To investigate the therapeutic potential of human immature dental pulp stem cells in the treatment of chronic spinal cord injury in dogs.

Methods:

Three dogs of different breeds with chronic SCI were presented as animal clinical cases. Human immature dental pulp stem cells were injected at three points into the spinal cord, and the animals were evaluated by limb function and magnetic resonance imaging (MRI) pre and post-operative.

Results:

There was significant improvement from the limb function evaluated by Olby Scale, though it was not supported by the imaging data provided by MRI and clinical sign and evaluation.

Conclusion:

Human dental pulp stem cell therapy presents promising clinical results in dogs with chronic spinal cord injuries, if used in association with physical therapy.