Over-Expression of TRPC6 via CRISPR Based Synergistic Activation Mediator in BMSCs Ameliorates Brain Injury in a Rat Model of Cerebral Ischemia/Reperfusion

Transient Receptor Potential Canonical 6 (TRPC6) Channel in the Pathogenesis of Diseases: A Jack of Many Trades

The mammalian Transient Receptor Potential Canonical (TRPC) subfamily comprises seven transmembrane proteins (TRPC1-7) forming cation channels in the plasma membrane of mammalian cells. TRPC channels mediate Ca²⁺ and Na⁺ influx into the cells. Amongst TRPCs, TRPC6 deficiency or increased activity due to gain-of-function mutations has been associated with a multitude of diseases, such as kidney disease, pulmonary disease, and neurological disease. Indeed, the TRPC6 protein is expressed in various organs and is involved in diverse signalling pathways. The last decade saw a surge in the investigative studies concerning the physiological roles of TRPC6 and describing the development of new pharmacological tools modulating TRPC6 activity. The current review summarizes the progress achieved in those investigations.

Advancement in CRISPR/Cas9 Technology to Better Understand and Treat Neurological Disorders

Neurological disorders have complicated pathophysiology that may involve several genetic mutations. Conventional treatment has limitations as they only treat apparent symptoms. Although, personalized medicine is emerging as a promising neuro-intervention, lack of precision is the major pitfall. Clustered regularly interspaced short palindromic repeat (CRISPR)/Cas9 system is evolving as a technological platform that may overcome the therapeutic limitations towards precision medicine. In the future, targeting genes in neurological disorders may be the mainstay of modern therapy. The present review on CRISPR/Cas9 and its application in various neurological disorders may provide a platform for its future clinical relevance towards developing precise and personalized medicine.

Transient receptor potential ion channels and cerebral stroke

METHODS

The databases Pubmed, and the National Library of Medicine were searched for literature. All papers on celebral stroke and transient receptor potential ion channels were considered.

RESULTS

Stroke is the second leading cause of death and disability, with an increasing incidence in developing countries. About 75 per cent of strokes are caused by occlusion of cerebral arteries, and substantial advances have been made in elucidating mechanisms how stroke affects the brain. Transient receptor potential (TRP) ion channels are calcium-permeable channels highly expressed in brain that drives Ca²⁺ entry into multiple cellular compartments. TRPC1/3/4/6, TRPV1/2/4, and TRPM2/4/7 channels have been implicated in stroke pathophysiology.

CONCLUSIONS

Although the precise mechanism of transient receptor potential ion channels in cerebral stroke is still unclear, it has the potential to be a therapeutic target for patients with stroke if developed appropriately. Hence, more research is needed to prove its efficacy in this context.

Increased serum concentrations of Mesencephalic astrocyte-derived neurotrophic factor in patients and rats with ischemic stroke

OBJECTIVES

Although Mesencephalic astrocyte-derived neurotrophic factor (MANF) shows protection in multiple cells, the role of circulating MANF in patients with acute ischemic stroke (AIS) and transient ischemic attack (TIA) remains unclear. Here, we aimed to explore the value of circulating MANF levels in cerebral ischemic events.

MATERIALS AND METHODS

Using a rat cerebral ischemic model, MANF expression in ischemic brains and serum was detected. 50 AIS patients, 56 TIA patients and 48 controls were enrolled, and MANF mRNA, inflammatory cytokines and MANF concentrations in serum and different blood cell types were detected. The National Institutes of Health Stroke Scale (NIHSS) score and Alberta Stroke Program Early CT Score (ASPECTS) were used to evaluate stroke severity. Cerebrovascular recurrence within 90 d was documented during TIA follow-up.

RESULTS

MANF expression increased at 2h, peaking at 24h and decreased to baseline at 7d in rat ischemic brains and serum. Serum MANF concentrations increased at 24h and 7d in AIS patients compared to controls and were correlated with NIHSS score, ASPECTS and inflammatory cytokines. MANF protein was present in blood cells, while MANF mRNA levels did not differ between AIS patients and controls. MANF levels revealed a good value to diagnose TIA with area under the curve (AUC) of 0.949 (95% CI: 0.9093-0.9892). MANF levels were lower in TIA patients with recurrence compared to non-recurrence patients. The AUC for MANF to predict a re-event was 0.80 (95% CI: 0.6746-0.9282).

CONCLUSIONS

Serum MANF levels correlate with neuroprotection, stroke severity, inflammation, and TIA recurrence.

Neuroprotective Effects of Estrogen Through BDNF-Transient Receptor Potential Channels 6 Signaling Pathway in the Hippocampus in a Rat Model of Perimenopausal Depression

Estradiol (E₂) has been proven to be effective in treating perimenopausal depression (PD); however, the downstream signaling pathways have not been fully elucidated. Transient receptor potential channels 6 (TRPC6) plays a vital role in promoting neuronal development and the formation of excitatory synapses. At present, we found that the serum levels of E₂ and brain-derived neurotrophic factor (BDNF) declined significantly in the women with PD compared to perimenopausal women, which was accompanied by a clear reduction in TRPC6 levels. To further reveal the effects of TRPC6 on neuronal survival and excitability, the PD-like rat model was established by the total removal of left ovary and 80% removal of right ovary followed by 21 days of the chronic unpredictable mild stress. Intragastric administration of E₂ (2 mg/kg), intraperitoneal injection of BDNF/TrB signaling pathway inhibitor (K252a, 100 μg/kg) and TRPC6 agonist (OAG, 0.6 mg/kg), and intracerebroventricular infusion of anti-BDNF antibody for blocking BDNF (0.5 μg/24 μl/rat) daily for 21 days were conducted. The levels of BDNF and TRPC6 in rat serum were lower in PD rats compared to the control rats; the depression-like behavior was induced, the neuronal death rate in the hippocampus increased, and the thickness of postsynaptic density (PSD) and the number of asymmetric synapses decreased significantly in the PD group. E₂ treatment greatly upregulated the serum levels of BDNF and TRPC6, the neuronal excitability indicated by an elevation in the PSD thickness and the numbers of asymmetric synapses, and these actions were reversed by K252a; co-administration of TRPC6 agonist and K252a improved neuronal degeneration and increased the neuronal excitability induced in the E₂-treated PD rats. K252a or anti-BDNF antibody inhibited the increased neuronal BDNF and TRPC6 expression in E₂-treated PD rats; co-treatment of TRPC6 agonist and anti-BDNF antibody reduced neuronal death and increased the BDNF and TRPC6 expression in the hippocampal CA1 neurons in the E₂-treated PD rats. These results suggest that the neuroprotective role of E₂ in PD is closely related to enhance the activity of BDNF/TRPC6 pathway and is helpful to provide new prevention and strategies.

Preconditioning with Trehalose Protects the Bone Marrow-Derived Mesenchymal Stem Cells Under Oxidative Stress and Enhances the Stem Cell-Based Therapy for Cerebral Ischemic Stroke

Bone marrow-derived mesenchymal stem cell (BMSC) transplantation has emerged as a potential treatment for ischemic stroke. Preconditioning with pharmacological agents before cell transplantation has been shown to increase the efficiency of cell therapy. In this study, trehalose (Tre), an autophagy inducer, was used as a pharmacological agent to treat BMSCs, and the neuroprotective effect of BMSCs preconditioned with Tre on cerebral ischemia was assessed. BMSCs were treated in vitro with different concentrations of Tre. Immunofluorescence staining of LC3B was performed to detect autophagy, and Western blotting for LC3, Beclin1, p-AMPK, and p-mTOR was performed. Flow cytometry and Western blotting analysis were performed to measure cell apoptosis in the presence of hydrogen peroxide (H₂O₂). Enzyme-linked immunosorbent assay was used to test the secretion levels of neurotrophic factors. An in vivo ischemia/reperfusion model was generated by middle cerebral artery occlusion in male Sprague Dawley rats, and Tre-preconditioned BMSCs were administered intralesionally 24 hours after ischemic injury. Histopathological examination and neurological function studies were conducted. In vitro, Tre promotes autophagy of BMSCs through the activation of the AMPK signal pathway. Tre protected BMSCs from H₂O₂-induced cell viability reduction and apoptosis. Moreover, Tre pretreatment increased the secretion of brain-derived neurotrophic factor, vascular endothelial growth factor, and hepatocyte growth factor. In vivo, preconditioning with Tre could further enhance the survival of BMSCs, reduce infarct size, alleviate cell apoptosis, abate vessel decrease, and ultimately improve functional recovery. Our study indicates that Tre can enhance the survival of BMSCs under oxidative stress and enhance BMSC-based treatment of ischemia/reperfusion injury.

BMSCs Regulate Astrocytes through TSG-6 to Protect the Blood-Brain Barrier after Subarachnoid Hemorrhage

Background

In patients with subarachnoid hemorrhage (SAH), the damage of the blood-brain barrier (BBB) can be life-threatening. Mesenchymal stem cells are widely used in clinical research due to their pleiotropic properties. This study is aimed at exploring the effect of BMSCs regulating astrocytes on the BBB after SAH.

Methods

The SAH model was established by perforating the blood vessels. BMSCs were transfected with TSG-6 inhibitor plasmid and cocultured with astrocytes. Intravenous transplantation of BMSCs was utilized to treat SAH rats. We performed ELISA, neurological scoring, Evans blue staining, NO measurement, immunofluorescence, BBB permeability, Western blot, HE staining, Nissl staining, and immunohistochemistry to evaluate the effect of BMSCs on astrocytes and BBB.

Results

SAH rats showed BBB injury, increased BBB permeability, and brain histological damage. BMSCs will secrete TSG-6 after being activated by TNF-α. Under the influence of TSG-6, the NF-κB and MAPK signaling pathways of astrocytes were inhibited. The expression of iNOS was reduced, while occludin, claudin 3, and ZO-1 expression was increased. The production of harmful substances NO and ONOO^- decreased. The level of inflammatory factors decreased. The apoptosis of astrocytes was weakened. TSG-6 secreted by BMSCs can relieve inflammation caused by SAH injury. The increase in BBB permeability of SAH rats was further reduced and the risk of rebleeding was reduced.

Conclusion

BMSCs can regulate the activation of astrocytes through secreting TSG-6 in vivo and in vitro to protect BBB.

Novel Mechanistic Insights and Potential Therapeutic Impact of TRPC6 in Neurovascular Coupling and Ischemic Stroke

Ischemic stroke is one of the most disabling diseases and a leading cause of death globally. Despite advances in medical care, the global burden of stroke continues to grow, as no effective treatments to limit or reverse ischemic injury to the brain are available. However, recent preclinical findings have revealed the potential role of transient receptor potential cation 6 (TRPC6) channels as endogenous protectors of neuronal tissue. Activating TRPC6 in various cerebral ischemia models has been found to prevent neuronal death, whereas blocking TRPC6 enhances sensitivity to ischemia. Evidence has shown that Ca2+ influx through TRPC6 activates the cAMP (adenosine 3',5'-cyclic monophosphate) response element-binding protein (CREB), an important transcription factor linked to neuronal survival. Additionally, TRPC6 activation may counter excitotoxic damage resulting from glutamate release by attenuating the activity of N-methyl-d-aspartate (NMDA) receptors of neurons by posttranslational means. Unresolved though, are the roles of TRPC6 channels in non-neuronal cells, such as astrocytes and endothelial cells. Moreover, TRPC6 channels may have detrimental effects on the blood-brain barrier, although their exact role in neurovascular coupling requires further investigation. This review discusses evidence-based cell-specific aspects of TRPC6 in the brain to assess the potential targets for ischemic stroke management.

Stroke treatment: Is exosome therapy superior to stem cell therapy?

Stroke is one of the most common causes of disability and death, and currently, ideal clinical treatment is lacking. Stem cell transplantation is a widely-used treatment approach for stroke. When compared with other types of stem cells, bone marrow mesenchymal stem cells (BMSCs) have been widely studied because of their many advantages. The paracrine effect is the primary mechanism for stem cells to play their role, and exosomes play an essential role in the paracrine effect. When compared with cell therapy, cell-free exosome therapy can prevent many risks and difficulties, and therefore, represents a promising and novel approach for treatment. In this study, we reviewed the research progress in the application of BMSCs-derived exosomes (BMSCs-exos) and BMSCs in the treatment of stroke. In addition, the advantages and disadvantages of cell therapy and cell-free exosome therapy were described, and the possible factors that hinder the introduction of these two treatments into the clinic were analyzed. Furthermore, we reviewed the current optimization methods of cell therapy and cell-free exosome therapy. Taken together, we hypothesize that cell-free exosome therapy will have excellent research prospects in the future, and therefore, it is worth further exploring. There are still some issues that need to be further addressed. For example, differences between the in vivo microenvironment and in vitro culture conditions will affect the paracrine effect of stem cells. Most importantly, we believe that more preclinical and clinical design studies are required to compare the efficacy of stem cells and exosomes.

Bone marrow mesenchymal stem cells induce M2 microglia polarization through PDGF-AA/MANF signaling

BACKGROUND

Bone marrow mesenchymal stem cells (BMSCs) are capable of shifting the microglia/macrophages phenotype from M1 to M2, contributing to BMSCs-induced brain repair. However, the regulatory mechanism of BMSCs on microglia/macrophages after ischemic stroke is unclear. Recent evidence suggests that mesencephalic astrocyte–derived neurotrophic factor (MANF) and platelet-derived growth factor-AA (PDGF-AA)/MANF signaling regulate M1/M2 macrophage polarization.

AIM

To investigate whether and how MANF or PDGF-AA/MANF signaling influences BMSCs-mediated M2 polarization.

METHODS

We identified the secretion of MANF by BMSCs and developed transgenic BMSCs using a targeting small interfering RNA for knockdown of MANF expression. Using a rat middle cerebral artery occlusion (MCAO) model transplanted by BMSCs and BMSCs–microglia Transwell coculture system, the effect of BMSCs-induced downregulation of MANF expression on the phenotype of microglia/macrophages was tested by Western blot, quantitative reverse transcription-polymerase chain reaction, and immunofluorescence. Additionally, microglia were transfected with mimics of miR-30a*, which influenced expression of X-box binding protein (XBP) 1, a key transcription factor that synergized with activating transcription factor 6 (ATF6) to govern MANF expression. We examined the levels of miR-30a*, ATF6, XBP1, and MANF after PDGF-AA treatment in the activated microglia.

RESULTS

Inhibition of MANF attenuated BMSCs-induced functional recovery and decreased M2 marker production, but increased M1 marker expression in vivo or in vitro. Furthermore, PDGF-AA treatment decreased miR-30a* expression, had no influence on the levels of ATF6, but enhanced expression of both XBP1 and MANF.

CONCLUSION

BMSCs-mediated MANF paracrine signaling, in particular the PDGF-AA/miR-30a*/XBP1/MANF pathway, synergistically mediates BMSCs-induced M2 polarization.

miR-135b levels in the peripheral blood serve as a marker associated with acute ischemic stroke

The protective role of microRNA (miR)-135b in cerebral neurons has been previously identified. However, to the best of our knowledge, the involvement of miR-135b in acute ischemic stroke has yet to be elucidated. The present study aimed to investigate the expression profile of miR-135b in peripheral blood obtained from patients with acute ischemic stroke. A total of 76 patients with acute ischemic stroke were selected as the case group, which included 33 cases of aorta atheromatous plague, 19 cases of cardioembolism, 16 cases of small arterial occlusion and 8 cases with unknown causes. In addition, 60 healthy subjects were selected as the control group. Reverse transcription-quantitative PCR was used to measure the expression of miR-135b in the peripheral blood of the patients. The National Institutes of Health Stroke Scale (NIHSS) score was used to evaluate the severity of acute ischemic stroke. The relationship between miR-135b levels and acute stroke was subsequently analyzed. The expression of miR-135b in the peripheral blood of the case group was found to be significantly higher compared with that in the control group. By contrast, the expression levels of miR-135b in the case group did not differ significantly between the different etiology types of acute ischemic stroke. In addition, a significant positive correlation was observed between levels of miR-135b expression and NIHSS scores. Further analysis demonstrated that hypertension, hyperglycemia, platelet count, international normalized ratio and miR-135b were risk factors for acute ischemic stroke. Based on bioinformatics analysis, a conserved binding site for miR-135b was identified in the 3'-untranslated region of the transient receptor potential cation channel subfamily C member 6 (TRPC6). Dual luciferase reporter and western blot analysis showed that TRPC6 was a target gene of miR-135b. In conclusion, data from the present study suggest that elevated expression of miR-135b in the peripheral blood of patients with acute ischemic stroke is closely associated with disease severity.

Novel Targets for Stroke Therapy: Special Focus on TRPC Channels and TRPC6

Stroke remains a leading cause of death, disability, and medical care burden worldwide. However, transformation from laboratory findings toward effective pharmacological interventions for clinical stroke has been unsatisfactory. Novel evidence has been gained on the underlying mechanisms and therapeutic potential related to the transient receptor potential (TRP) channels in several disorders. The TRP superfamily consists of a diverse group of Ca²⁺ permeable non-selective cation channels. In particular, the members of TRP subfamilies, TRP canonical (TRPC) channels and TRPC6, have been found in different cell types in the whole body and have high levels of expression in the central nervous system (CNS). Notably, the TRPCs and TRPC6 channel have been implicated in neurite outgrowth and neuronal survival during normal development and in a range of CNS pathological conditions. Recent studies have shown that suppression of TRPC6 channel degradation prevents ischemic neuronal cell death in experimental stroke. Accumulating evidence supports the important functions of TRPC6 in brain ischemia. We have highlighted some crucial advancement that points toward an important involvement of TRPCs and TRPC6 in ischemic stroke. This review will make an overview of the TRP and TRPC channels due to their roles as targets for clinical trials and CNS disorders. Besides, the primary goal is to discuss and update the critical role of TRPC6 channels in stroke and provide a promising target for stroke prevention and therapy.