Hypothermia-Modulating Matrix Elasticity of Injured Brain Promoted Neural Lineage Specification of Mesenchymal Stem Cells.

Both chemical and physical microenvironments appear to be important for lineage specification of umbilical cord mesenchymal stem cells (UCMSCs). However, physical factors such as the elastic modulus in traumatic brain injury (TBI) are seldom studied. Intracranial hypertension and cerebral edema after TBI may change the brain's physical microenvironment, which inhibits neural lineage specification of transplanted UCMSCs. The purpose of this study is to investigate the potential regulatory effect of mild hypothermia on the elastic modulus of the injured brain. First, we found that more UCMSCs grown on gels mimicking the elastic modulus of the brain (0.5 kPa) differentiated into neural cells, which were verified with the formation of branched cells and the expression of neural markers. Then, UCMSCs were transplanted into TBI rats, and we observed that mild hypothermia resulted in the differentiation of more neurons and astrocytes from transplanted UCMSCs. To demonstrate that more neural specification of UCMSCs was due to the regulation of the elastic modulus, we monitored intracranial pressure and cerebral edema. The results showed that mild hypothermia significantly reduced intracranial pressure and brain water content, indicating modulation of the elastic modulus by mild hypothermia. An examination with atomic force microscopy (AFM) in a cell injury model in vitro further verified hypothermia-regulated elastic modulus. In this study, we found a novel role of mild hypothermia in modulating the elastic modulus of the injured brain, resulting in the promotion of neural lineage specification of UCMSCs, which suggested that the combination of mild hypothermia had more advantages in cell-based therapy after TBI.