Aggregation of human mesenchymal stem cells enhances survival and efficacy in stroke treatment

Human mesenchymal stem cells (hMSCs) have been shown to enhance stroke lesion recovery by mediating inflammation and tissue repair through secretion of trophic factors. However, low cell survival and reduced primitive stem cell function of culture-expanded hMSCs are the major challenges limiting hMSC therapeutic efficacy in stroke treatment. In this study, we report the effects of short-term preconditioning of hMSCs via three-dimensional (3D) aggregation on stroke lesion recovery after intra-arterial (IA) transplantation of 3D aggregate-derived hMSCs (Agg-D hMSCs) in a transient middle cerebral artery occlusion (MCAO) stroke model. Compared with two-dimensional (2D) monolayer culture, Agg-D hMSCs exhibited increased resistance to ischemic stress, secretory function and therapeutic outcome. Short-term preconditioning via 3D aggregation reconfigured hMSC energy metabolism and altered redox cycle, which activated the PI3K/AKT pathway and enhanced resistance to in vitro oxidative stress. Analysis of transplanted hMSCs in MCAO rats using ultra-high-field magnetic resonance imaging at 21.1 T showed increased hMSC persistence and stroke lesion reduction by sodium (²³Na) imaging in the Agg-D hMSC group compared with 2D hMSC control. Behavioral analyses further revealed functional improvement in MCAO animal treated with Agg-D hMSCs compared with saline control. Together, the results demonstrated the improved outcome for Agg-D hMSCs in the MCAO model and suggest short-term 3D aggregation as an effective preconditioning strategy for hMSC functional enhancement in stroke treatment.