Probing the Instability of a Cluster of Slip Bonds Upon Cyclic Loads With a Coupled Finite Element Analysis and Monte Carlo Method

Cells are subjected to cyclic loads under physiological conditions, which regulate cellular structures and functions. Recently, it was demonstrated that cells on substrates reoriented nearly perpendicular to the stretch direction in response to uni-axial cyclic stretches. Though various theories were proposed to explain this observation, the underlying mechanism, especially at the molecular level, is still elusive. To provide insights into this intriguing observation, we employ a coupled finite element analysis (FEA) and Monte Carlo method to investigate the stability of a cluster of slip bonds upon cyclic loads. Our simulation results indicate that the cluster can become unstable upon cyclic loads and there exist two characteristic failure modes: gradual sliding with a relatively long lifetime versus catastrophic failure with a relatively short lifetime. We also find that the lifetime of the bond cluster, in many cases, decreases with increasing stretch amplitude and also decreases with increasing cyclic frequency, which appears to saturate at high cyclic frequencies. These results are consistent with the experimental reports. This work suggests the possible role of slip bonds in cellular reorientation upon cyclic stretch.