TRPML1 ion channel promote HepaRG cells differentiation under simulated microgravity conditions

Abstract

Abstract Stem cell differentiation must be regulated by intricate and complex interactions between cells and their surrounding environment, ensuring normal organ and tissue morphology such as the liver 1. Though it is well acknowledged that microgravity provides necessary mechanical force signals for cells fate 2, how microgravity affects growth, differentiation, and communication is still largely unknown due to the lack of real experimental scenarios and reproducibility tools. Here, we used Rotating Flat Chamber (RFC) to simulate ground-based microgravity effects to study how microgravity affects the differentiation of HepaRG (hepatic progenitor cells) cells. Unexpectedly, we found that simulated microgravity could promote HepaRG cells differentiation which was exhibited as increased expression of Alpha-fetoprotein (AFP), albumin (ALB), and Recombinant Cytokeratin 18 (CK18). Through screening a series of mechanical receptors, we identified that ion channel TRPML1 was critical for the differentiation promotion effect of microgravity. Once TRPML1 was activated by microgravity, the concentration of lysosomal calcium ions was increased to activate the Wnt/β-catenin signaling pathway, which finally led to the enhanced cell differentiation of HepaRG cells. In addition, the cytoskeleton was remodeled under microgravity conditions and then influenced the expression of PI (3,5) P2, which is the best-known activator of TRPML1. In summary, our findings have established a mechanism by which microgravity promotes the differentiation of HepaRG cells through the TRPML1 signaling pathway, which may provide a potential target for the regulation of hepatic stem/progenitor cells differentiation and embryonic liver development under microgravity conditions.