Objective To investigate the synergistic regulation of the polarization of mesenchymal stem cells by integrin and N-cadherin-mediated mechanical adhesion and the underlying mechanobiological mechanisms.

Methods Bilayer polyethylene glyeol (PEG) hydrogels were formulated and modified with RGD and HAVDI peptides, respectively, to achieve mechanical adhesion to integrin and N-cadherin and to replicate the integrin-mediated mechanical interaction between cells and the extracellular matrix and the N-cadherin-mediated cell-cell mechanical interaction. The polar proteins, phosphatidylinositol 3-kinase (PI3K) and phosphorylated myosin light chain (pMLC), were characterized through immunofluorescence staining in individual cells with or without contact with HAVDI peptides under integrin-mediated adhesion, N-cadherin-mediated adhesion, and different intracellular forces. Their expression levels and polar distribution were analyzed using Image J.

Results Integrin-mediated adhesion induced significantly higher polar strengths of PI3K and pMLC in the contact group than in those in the no contact group, resulting in the concentration of the polar angle of PI3K to β-catenin in the range of 135° to 180° and the concentration of the polar angle of pMLC to β-catenin in the range of 0° to 45° in the contact group. Inhibition of integrin function led to inhibition of the polarity distribution of PI3K in the contact group, but did not change the polarity distribution of pMLC protein. The effect of N-cadherin on the polarity distributions of PI3K and pMLC was similar to that of integrin. However, inhibition of the mechanical adhesion of N-cadherin led to inhibition of the polarity intensity and polarity angle distribution of PI3K and pMLC proteins in the contact group. Furthermore, inhibition of the mechanical adhesion of N-cadherin caused weakened polarity intensity of integrin β1, reducing the proportion of cells with polarity angles between integrin β1 and β-catenin concentrating in the range of 135° to 180°. Additionally, intracellular forces influenced the polar distribution of PI3K and pMLC proteins. Reducing intracellular forces weakened the polarity intensity of PI3K and pMLC proteins and their polarity distribution, while increasing intracellular forces enhanced the polarity intensity of PI3K and pMLC proteins and their polarity distribution.

Conclusion Integrin and N-cadherin co-regulate the polarity distribution of cell proteins and N-cadherin can play an important role in the polarity regulation of stem cells through local inhibition of integrin.