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Analysis of reactive astrocytes and NG2 proteoglycan in ex vivo rat models of spinal cord injury

Patar A, Dockery P, Howard L, McMahon S

J Neurosci Methods, 2019 01 01;311:418-425.
PMID: 30267723 DOI: 10.1016/j.jneumeth.2018.09.027

BACKGROUND: The use of animals to model spinal cord injury (SCI) requires extensive post-operative care and can be expensive, which makes an alternative model extremely attractive. The use ofex vivo slice cultures is an alternative way to study the pathophysiological changes that can mimic in vivo conditions and support the 3Rs (replacement, reduction and refinement) of animal use in SCI research models.
NEW METHOD: In this study the presence of reactive astrocytes and NG2 proteoglycans was investigated in two ex vivo models of SCI; stab injury and transection injury. Stereological analysis to measure immunohistochemical staining was performed on the scar and injury zones to detect astrocytes and the chondroitin sulphate proteoglycan NG2.
RESULTS: The volume fraction (Vv) of reactive astrocytes and NG2 proteoglycans increased significantly between day 3 and day 10 post injury in both ex vivo models. This data shows how ex vivo SCI models are a useful research tool allowing reduction of research cost and time involved in carrying out animal studies, as well as reducing the numbers of animals used.
COMPARISON WITH EXISTING METHOD: This is the first evidence of an ex vivo stab injury model of SCI and also the first comparison of immunohistochemical staining for injury markers within stab injured and transection injured ex vivo slice cultures.
CONCLUSIONS: The use of organotypic slice culture models provide a simple way to study the cellular consequences following SCI and they can also be used as a platform for potential therapeutics regimes for the treatment of SCI.
Fulltext Cell viability in three ex vivo rat models of spinal cord injury

Patar A, Dockery P, Howard L, McMahon SS

J Anat, 2019 02;234(2):244-251.
PMID: 30417349 DOI: 10.1111/joa.12909

Spinal cord injury (SCI) is a devastating disorder that has a poor prognosis of recovery. Animal models of SCI are useful to understand the pathophysiology of SCI and the potential use of therapeutic strategies for human SCI. Ex vivo models of central nervous system (CNS) trauma, particularly mechanical trauma, have become important tools to complement in vivo models of injury in order to reproduce the sequelae of human CNS injury. Ex vivo organotypic slice cultures (OSCs) provide a reliable model platform for the study of cell dynamics and therapeutic intervention following SCI. In addition, these ex vivo models support the 3R concept of animal use in SCI research - replacement, reduction and refinement. Ex vivo models cannot be used to monitor functional recovery, nor do they have the intact blood supply of the in vivo model systems. However, the ex vivo models appear to reproduce many of the post traumatic events including acute and secondary injury mechanisms. Several well-established OSC models have been developed over the past few years for experimental spinal injuries ex vivo in order to understand the biological response to injury. In this study, we investigated cell viability in three ex vivo OSC models of SCI: stab injury, transection injury and contusion injury. Injury was inflicted in postnatal day 4 rat spinal cord slices. Stab injury was performed using a needle on transverse slices of spinal cord. Transection injury was performed on longitudinal slices of spinal cord using a double blade technique. Contusion injury was performed on longitudinal slices of spinal cord using an Infinite Horizon impactor device. At days 3 and 10 post-injury, viability was measured using dual staining for propidium iodide and fluorescein diacetate. In all ex vivo SCI models, the slices showed more live cells than dead cells over 10 days in culture, with higher cell viability in control slices compared with injured slices. Although no change in cell viability was observed between time-points in stab- and contusion-injured OSCs, a reduction in cell viability was observed over time in transection-injured OSCs. Taken together, ex vivo SCI models are a useful and reliable research tool that reduces the cost and time involved in carrying out animal studies. The use of OSC models provides a simple way to study the cellular consequences following SCI, and they can also be used to investigate potential therapeutics regimes for the treatment of SCI.
Fulltext Mesenchymal Stem Cell Therapy in Multiple Sclerosis: A Systematic Review and Meta-Analysis

Islam MA, Alam SS, Kundu S, Ahmed S, Sultana S, Patar A, et al.

J Clin Med, 2023 Sep 30;12(19).
PMID: 37834955 DOI: 10.3390/jcm12196311

The assurance of safety and effectiveness is a significant focal point in all therapeutic approaches. Although mesenchymal stem cells (MSCs) have been identified as a potential novel therapeutic strategy for multiple sclerosis (MS), existing evidence regarding the effectiveness and safety of this strategy remains inconclusive. Thus, the primary aim of this systematic review and meta-analysis (SRMA) was to comprehensively assess the effectiveness and safety of MSC therapy in individuals diagnosed with MS. A comprehensive search was conducted using appropriate keywords in the PubMed, Scopus, Cochrane, ScienceDirect, and Google Scholar databases to determine the eligible studies. The change in the expanded disability status scale (EDSS) score from baseline to follow-up was used to assess MSC efficacy. The effectiveness of the therapy was assessed using a random-effects model, which calculated the combined prevalence and 95% confidence intervals (CIs) for MS patients who experienced improvement, stability, or worsening of their condition. The protocol was registered in PROSPERO (CRD42020209671). The findings indicate that 40.4% (95% CI: 30.6-50.2) of MS patients exhibited improvements following MSC therapy, 32.8% (95% CI: 25.5-40.1) remained stable, and 18.1% (95% CI: 12.0-24.2) experienced a worsening of their condition. Although no major complications were observed, headaches 57.6 [37.9-77.3] and fever 53.1 [20.7-85.4] were commonly reported as minor adverse events. All of the results reported in this meta-analysis are consistent and credible according to the sensitivity analyses. Regardless of different individual studies, our meta-analysis provides a comprehensive overview showing the potential of MSC therapy as a possible effective treatment strategy for patients with MS.
Enhancing Gpx1 palmitoylation to inhibit angiogenesis by targeting PPT1

Ma Y, Yuan X, Wei A, Li X, Patar A, Su S, et al.

Redox Biol, 2024 Oct 05;77:103376.
PMID: 39423458 DOI: 10.1016/j.redox.2024.103376

The significance of protein S-palmitoylation in angiogenesis has been largely overlooked, leaving various aspects unexplored. Recent identification of Gpx1 as a palmitoylated protein has generated interest in exploring its potential involvement in novel pathological mechanisms related to angiogenesis. In this study, we demonstrate that Gpx1 undergoes palmitoylation at cysteine-76 and -113, with PPT1 playing a crucial role in modulating the depalmitoylation of Gpx1. Furthermore, we find that PPT1-regulated depalmitoylation negatively impacts Gpx1 protein stability. Interestingly, inhibiting Gpx1 palmitoylation, either through expression of a non-palmitoylated Gpx1 mutant or by expressing PPT1, significantly enhances neovascular angiogenesis. Conversely, in PPT1-deficient mice, angiogenesis is notably attenuated compared to wild-type mice in an Oxygen-Induced Retinopathy (OIR) model, which mimics pathological angiogenesis. Physiologically, under hypoxic conditions, Gpx1 palmitoylation levels are drastically reduced, suggesting that increasing Gpx1 palmitoylation may have beneficial effects. Indeed, enhancing Gpx1 palmitoylation by inhibiting PPT1 with DC661 effectively suppresses retinal angiogenesis in the OIR disease model. Overall, our findings highlight the pivotal role of protein palmitoylation in angiogenesis and propose a novel mechanism whereby the PPT1-Gpx1 axis modulates angiogenesis, thereby providing a potential therapeutic strategy for targeting PPT1 to combat angiogenesis.