Mediating the invasion of smooth muscle cells into a cell-responsive hydrogel under the existence of immune cells.

Cell migration plays an important role in many physiological and biological processes, which is influenced by both physicochemical properties of surrounding matrix and signal gradient generated by neighboring/remote cells. Here we aim to develop a co-culture system of immune cells and smooth muscle cells (SMCs) based on the combination of Transwell and cell-responsive hydrogels. This model can be used to study the cell invasion into hydrogels in dynamic physiological conditions, with better mimicking of the in vivo microenvironment. Methacrylic anhydride-modified hyaluronic acid (MA-HA) macromolecules were crosslinked by matrix metalloproteinases (MMPs) sensitive peptides (MMP SP) to fabricate a cell-degradable hydrogel mimicking dynamic extracellular matrix (ECM). The migration of SMCs into the MMP-sensitive hydrogel was investigated under the existence of U937 cells, a type of macrophage-like cells. The invasion distance of SMCs in the MMP-sensitive hydrogels was much longer than that in the MMP-insensitive ones both in vitro and in vivo. The impact of hydrogel degradability and inductive signal gradient generated by U937 cells on cell invasion was compared, revealing that the degradability plays a major role in regulating cell invasion into the 3D hydrogels. Further mechanism investigation revealed that the expressions of cell migration-related genes and proteins were significantly up-regulated in the MMP-sensitive hydrogels compared to those in the MMP-insensitive hydrogels.