Increased nuclear stiffness via FAK-ERK1/2 signaling is necessary for synthetic mechano-growth factor E peptide-induced tenocyte migration

We have previously reported that a synthetic mechano-growth factor (MGF) C-terminal E-domain with 25 amino acids (MGF-C25E) promotes rat tenocyte migration through the FAK-ERK1/2 signaling pathway. However, the role of the nucleus in MGF-C25E-promoted tenocyte migration and the molecular mechanisms involved remain unclear. In this study, we demonstrate that MGF-C25E increases the Young's modulus of tenocytes through the FAK-ERK1/2 signaling pathway. This increase is not accompanied by an obvious change in the expression of Lamin A/C but is accompanied by significant chromatin condensation, indicating that MGF-C25E-induced chromatin condensation may contribute to the increased nuclear stiffness. Moreover, DNA methylation is observed in MGF-C25E-treated tenocytes. Inhibition of DNA methylation suppresses the elevation in chromatin condensation, in nuclear stiffness, and in tenocyte migration induced by MGF-C25E. The inhibition of the focal adhesion kinase (FAK) or extracellular signal regulated kinase 1/2 (ERK1/2) signals represses MGF-C25E-promoted DNA methylation. It also abolishes chromatin condensation, nuclear stiffness, and cell migration. Taken together, our results suggest that MGF-C25E promotes tenocyte migration by increasing nuclear stiffness via the FAK-ERK1/2 signaling pathway. This provides strong evidence for the role of nuclear mechanics in tenocyte migration and new insight into the molecular mechanisms of MGF-promoted tenocyte migration.