Calcium signaling is gated by a mechanical threshold in three-dimensional environments

Cells interpret their mechanical environment using diverse signaling pathways that affect complex phenotypes. These pathways often interact with ubiquitous 2^nd-messengers such as calcium. Understanding mechanically-induced calcium signaling is especially important in fibroblasts, cells that exist in three-dimensional fibrous matrices, sense their mechanical environment, and remodel tissue morphology. Here, we examined calcium signaling in fibroblasts using a minimal-profile, three-dimensional (MP3D) mechanical assay system, and compared responses to those elicited by conventional, two-dimensional magnetic tensile cytometry and substratum stretching. Using the MP3D system, we observed robust mechanically-induced calcium responses that could not be recreated using either two-dimensional technique. Furthermore, we used the MP3D system to identify a critical displacement threshold governing an all-or-nothing mechanically-induced calcium response. We believe these findings significantly increase our understanding of the critical role of calcium signaling in cells in three-dimensional environments with broad implications in development and disease.