Human umbilical cord derived mesenchymal stem cells overexpressing HO‐1 attenuate neural injury and enhance functional recovery by inhibiting inflammation in stroke mice

Abstract Aims The current evidence demonstrates that mesenchymal stem cells (MSCs) hold therapeutic potential for ischemic stroke. However, it remains unclear how changes in the secretion of MSC cytokines following the overexpression of heme oxygenase‐1 (HO‐1) impact excessive inflammatory activation in a mouse ischemic stroke model. This study investigated this aspect and provided further insights. Methods The middle cerebral artery occlusion (MCAO) mouse model was established, and subsequent injections of MSC, MSC HO‐1 , or PBS solutions of equal volume were administered via the mice's tail vein. Histopathological analysis was conducted on Days 3 and 28 post‐MCAO to observe morphological changes in brain slices. mRNA expression levels of various factors, including IL‐1β, IL‐6, IL‐17, TNF‐α, IL‐1Ra, IL‐4, IL‐10, TGF‐β, were quantified. The effects of MSC HO‐1 treatment on neurons, microglia, and astrocytes were observed using immunofluorescence after transplantation. The polarization direction of macrophages/microglia was also detected using flow cytometry. Results The results showed that the expression of anti‐inflammatory factors in the MSC HO‐1 group increased while that of pro‐inflammatory factors decreased. Small animal fluorescence studies and immunofluorescence assays showed that the homing function of MSCs HO‐1 was unaffected, leading to a substantial accumulation of MSCs HO‐1 in the cerebral ischemic region within 24 h. Neurons were less damaged, activation and proliferation of microglia were reduced, and polarization of microglia to the M2 type increased after MSC HO‐1 transplantation. Furthermore, after transplantation of MSCs HO‐1 , the mortality of mice decreased, and motor function improved significantly. Conclusion The findings indicate that MSCs overexpressing HO‐1 exhibited significant therapeutic effects against hyper‐inflammatory injury after stroke in mice, ultimately promoting recovery after ischemic stroke.