MCPIP-1 knockdown enhances endothelial colony-forming cell angiogenesis via the TFRC/AKT/mTOR signaling pathway in the ischemic penumbra of MCAO mice.

Cerebral ischemia is a serious disease characterized by brain tissue ischemia and hypoxic necrosis caused by the blockage of blood vessels within the central nervous system. Although stem cell therapy is a promising approach for treating ischemic stroke, the inflammatory, oxidative, and hypoxic environment generated by cerebral ischemia greatly reduces the survival and therapeutic effects of transplanted stem cells. Endothelial colony-forming cells (ECFCs) are a class of precursor cells with strong proliferative potential that can migrate and differentiate directly into mature vascular endothelial cells. Consequently, ECFCs can exert significant therapeutic and reparative effects in diseases associated with vascular injury. Monocyte chemoattractant protein-induced protein 1 (MCPIP-1) exerts multiple biological effects; however, no studies have yet reported its role in the angiogenic function of ECFCs. In this study, we performed Proteome Profiler™ Human Angiogenesis Antibody arrays and tandem mass tag protein profiling to investigate the effect of MCPIP-1 on ECFCs. We demonstrated that MCPIP-1 knockdown enhanced the proliferation, migration, and in vivo and in vitro angiogenic capacity of ECFCs by upregulating the transferrin receptor-activated AKT/m-TOR signaling pathway to promote cellular trophic factor secretion. Furthermore, we found that the lateral ventricular transplantation of ECFCs with lentiviral MCPIP-1 knockdown into mice with middle cerebral artery occlusion increased serum vacular endothelial growth factor(VEGF), angiopoietin-1, and HIF-1a levels, enhanced neovascularization and neurogenesis in the ischemic penumbra, reduced the size of cerebral infarcts, and promoted neurological recovery. Together, these findings suggest new avenues for enhancing the therapeutic efficacy of ECFCs.

Mesenchymal stem cells protect against TBI-induced pyroptosis in vivo and in vitro through TSG-6.

BACKGROUND: Pyroptosis, especially microglial pyroptosis, may play an important role in central nervous system pathologies, including traumatic brain injury (TBI). Transplantation of mesenchymal stem cells (MSCs), such as human umbilical cord MSCs (hUMSCs), has been a focus of brain injury treatment. Recently, MSCs have been found to play a role in many diseases by regulating the pyroptosis pathway. However, the effect of MSC transplantation on pyroptosis following TBI remains unknown. Tumor necrosis factor α stimulated gene 6/protein (TSG-6), a potent anti-inflammatory factor expressed in many cell types including MSCs, plays an anti-inflammatory role in many diseases; however, the effect of TSG-6 secreted by MSCs on pyroptosis remains unclear. METHODS: Mice were subjected to controlled cortical impact injury in vivo. To assess the time course of pyroptosis after TBI, brains of TBI mice were collected at different time points. To study the effect of TSG-6 secreted by hUMSCs in regulating pyroptosis, normal hUMSCs, sh-TSG-6 hUMSCs, or different concentrations of rmTSG-6 were injected intracerebroventricularly into mice 4 h after TBI. Neurological deficits, double immunofluorescence staining, presence of inflammatory factors, cell apoptosis, and pyroptosis were assessed. In vitro, we investigated the anti-pyroptosis effects of hUMSCs and TSG-6 in a lipopolysaccharide/ATP-induced BV2 microglial pyroptosis model. RESULTS: In TBI mice, the co-localization of Iba-1 (marking microglia/macrophages) with NLRP3/Caspase-1 p20/GSDMD was distinctly observed at 48 h. In vivo, hUMSC transplantation or treatment with rmTSG-6 in TBI mice significantly improved neurological deficits, reduced inflammatory cytokine expression, and inhibited both NLRP3/Caspase-1 p20/GSDMD expression and microglial pyroptosis in the cerebral cortices of TBI mice. However, the therapeutic effect of hUMSCs on TBI mice was reduced by the inhibition of TSG-6 expression in hUMSCs. In vitro, lipopolysaccharide/ATP-induced BV2 microglial pyroptosis was inhibited by co-culture with hUMSCs or with rmTSG-6. However, the inhibitory effect of hUMSCs on BV2 microglial pyroptosis was significantly reduced by TSG-6-shRNA transfection. CONCLUSION: In TBI mice, microglial pyroptosis was observed. Both in vivo and in vitro, hUMSCs inhibited pyroptosis, particularly microglial pyroptosis, by regulating the NLRP3/Caspase-1/GSDMD signaling pathway via TSG-6. Video Abstract.

Indole-3-propionic acid alleviates ischemic brain injury in a mouse middle cerebral artery occlusion model.

Increasing evidence highlights the importance of gut microbiota and its metabolites as an environmental factor affecting ischemic stroke. However, the role of microbial indole metabolites in ischemic stroke remains largely unknown. Here, we evaluated the effects and the underlying mechanism of indole-3-propionic acid (IPA) in a mouse model of acute middle cerebral artery occlusion (MCAO) and the mechanisms underlying these effects. We collected blood samples and evaluated serum indole derivatives levels using ultra-performance liquid chromatography with tandem mass spectrometry (UPLC-MS) in 8-10-week-old male C57 mice undergoing MCAO or sham. Intragastric IPA administration (400 µg/20 g/d) was performed in mice with MCAO, and its effects and mechanisms were assessed. We found that the serum IPA levels were significantly lower in mice with MCAO than in sham-treated subjects. 16S rRNA gene sequencing revealed that IPA treatment ameliorated the MCAO-induced alterations of the gut microbiome structure, specifically reshaping the microbial community composition in mice with MCAO to resemble that in the mice from the control group, with an increase in the abundance of probiotics and a decrease in the abundance of harmful bacteria. IPA repaired the integrity of the intestinal barrier and regulated the activities of regulatory T cells (Tregs) and Th17 cells in the gut-associated lymphoid tissue. Intragastric IPA administration effectively alleviated neuroinflammation, neurological impairment and brain infarction. Of note, Tregs in the IPA treatment group inhibited A1 reactive astrogliosis in vitro. The beneficial effects of IPA are thus mediated by the gut microbiota, which could enable the development of prebiotics for microbiome-based treatments for ischemic stroke.

Human umbilical cord mesenchymal stem cell-derived exosomal miR-146a-5p reduces microglial-mediated neuroinflammation via suppression of the IRAK1/TRAF6 signaling pathway after ischemic stroke.

To investigate the therapeutic mechanism of action of transplanted stem cells and develop exosome-based nanotherapeutics for ischemic stroke, we assessed the effect of exosomes (Exos) produced by human umbilical cord mesenchymal stem cells (hUMSCs) on microglia-mediated neuroinflammation after ischemic stroke. Our results found that injected hUMSC-Exos were able to access the site of ischemic damage and could be internalized by cells both in vivo and in vitro. In vitro, treatment with hUMSC-Exos attenuated microglia-mediated inflammation after oxygen-glucose deprivation (OGD). In vivo results demonstrated that treatment with hUMSC-Exos significantly reduced infarct volume, attenuated behavioral deficits, and ameliorated microglia activation, as measured three days post-transient brain ischemia. Furthermore, miR-146a-5p knockdown (miR-146a-5p k/d Exos) partially reversed the neuroprotective effect of hUMSC-Exos. Our mechanistic study demonstrated that miR-146a-5p in hUMSC-Exos reduces microglial-mediated neuroinflammatory response through IRAK1/TRAF6 pathway. We conclude that miR-146a-5p derived from hUMSC-Exos can attenuate microglia-mediated neuroinflammation and consequent neural deficits following ischemic stroke. These results elucidate a potential therapeutic mechanism of action of mesenchymal stem cells and provide evidence that hUMSC-Exos represent a potential cell-free therapeutic option for ischemic stroke.

Meta-Analysis of the Safety and Efficacy of Stem Cell Therapies for Ischemic Stroke in Preclinical and Clinical Studies.

Recent studies have indicated that stem cell transplantation may be effective in the treatment of ischemic stroke. Therefore, we performed a meta-analysis to evaluate the safety and efficacy of stem cell therapy for ischemic stroke in preclinical and clinical studies. In accordance with Preferred Reporting Items for Systematic Reviews and Meta-Analyses (PRISMA) guidelines, we searched the PubMed, Cochrane Library, Embase, Web of science, and Ovid databases from inception through May 2018. A total of 11 preclinical studies-18 independent interventions were ultimately included. Similarly, 11 clinical studies were finally included. Two authors independently screened trials. Lesion volume and modified neurological severity scores (mNSSs) were regarded as outcome measures for preclinical studies. The composite weighted mean [95% confidence interval (CI)] effect sizes for lesion volume, percentage of lesion volume, and mNSSs were -46.59 (-62.04 to -31.15; P < 0.001), -13.18 (-25.62 to -0.73; P = 0.04), and -1.85 (-2.17 to -1.53; P < 0.001), respectively. Our analysis revealed that all three outcomes were significantly more favorable in the stem cell group than in the control group. Barthel index (BI) values, modified Rankin scale (mRS) scores, National Institutes of Health Stroke Scale (NIHSS) scores, and Fugl-Meyer assessment (FMA) scores were regarded as outcome measures for human studies. Our results were as follows: NIHSS [mean differences, MDs = -2.57, 95% CI (-3.45 to -1.68), I2 = 51%, P < 0.001]; BI [MD = 7.93, 95% CI (3.11 to 12.75), I2 = 59%, P = 0.001]; mRS [MD = -0.53, 95% CI (-0.73 to -0.28), I2 = 0%, P < 0.001]; FMA [MD = 5.50, 95% CI (2.05 to 8.95), I2 = 15%, P = 0.002]. These results suggest that stem cell transplantation was associated with significantly better outcomes than control treatment. Adverse reactions such as mild headache and fever resolved shortly after treatment. Stem cell transplantation can significantly improve neurological deficits and quality of life in patients with ischemic stroke, without severe adverse reactions. Our results also suggest that such treatment is most effective when provided earlier and through the intravenous route.