Effect of geometric challenges on cell migration.

Cellular infiltration and colonization of three-dimensional (3D) porous scaffolds is influenced by many factors. One of the major factors is the internal architecture presented to the cells. In this work, we have developed and validated a microfluidic device that presents a multitude of geometric challenges to cells, mimicking the architectural aspects and characteristics of 3D porous scaffolds in a two-dimensional arrangement. This device has been utilized to investigate the influence of varying channel widths, degrees of channel tortuosity, the presence of contractions or expansions, and channel junctions on the migration of NIH 3T3 mouse fibroblasts and human bone marrow-derived mesenchymal stromal cell (hMSCs). These two cell types were observed to have vastly different migration characteristics; 3T3 fibroblasts migrate as a collective cell front, whereas hMSCs migrate as single cells. This resulted in 3T3 fibroblasts displaying significant differences in migration depending on the type of geometrical constraint, whereas hMSCs were only influenced by channel width when it approached that of the length scale of a single cell. The differences in migration characteristics were shown to be related to the expression of the intercellular junction protein N-cadherin. We observed that 3T3 fibroblasts express higher levels of N-cadherin than hMSCs and that N-cadherin inhibition modified the migration characteristics of the 3T3 fibroblasts, so that they were then similar to that of hMSCs. The results of this study both confirm the utility of the device and highlight that differences in migration characteristics of different cell types can be deterministic of how they may respond to geometric constraints within porous tissue engineering constructs.