Hypergravity enhances RBM4 expression in human bone marrow-derived mesenchymal stem cells and accelerates their differentiation into neurons.

Introduction: The regulation of stem cell differentiation is important in determining the quality of transplanted cells in regenerative medicine. Physical stimuli are involved in regulating stem cell differentiation, and in particular, research on the regulation of differentiation using gravity is an attractive choice. We have shown that microgravity is useful for maintaining undifferentiated mesenchymal stem cells (MSCs). However, the effects of hypergravity on the differentiation of MSCs, especially on neural differentiation related to neural regeneration, have not been elucidated. Methods: We induced neural differentiation of human bone marrow-derived MSCs (hbMSCs) for 10 days under normal gravity (1G) or hypergravity (3G) conditions using a gravity controller, Gravite®. HbMSCs were collected, and cell number and viability were measured 3 and 10 days after induction. RNA was also extracted from the collected hbMSCs, and the expression of neuron-associated genes and regulator markers of neural differentiation was analyzed using real-time polymerase chain reaction (PCR). Additionally, we evaluated the NF-M-positive cell rate 10 days after induction using immunofluorescent staining. Results: Neural gene expression and the NF-M-positive cell rate were increased in hbMSCs under the 3G condition 10 days after induction. mRNA expression of RNA binding motif protein 4 (RBM4) and pyruvate kinase M 1 (PKM1) in the 3G condition was also higher than that in the 1G group. Conclusions: Hypergravity can enhance