Ian R. Wheeldon, Alex Bick, Amir Foudeh, Nezam Kachouie, and Ali Khademhosseini
In early cardiac valvulogenesis, cells in the atrioventricular (AV) cushion invade the extracellular matrix (ECM) and begin remodeling the surrounding tissues into valve leaflets. Hyaluronic acid (HA) has been implicated as a major component of the cell-ECM signaling that initiates the transformation of progenitor cells into endothelium and mesenchyme and the cellular invasion that follows the transformation. Here microarrays of nano-liter sized HA hydrogels containing ECM components identified from the proteomic analysis of the developing AV cushion are screened for the promotion of the epithelial-to-mesenchymal transformation of endothelial progenitor cells (EPC). EPCs cultured on arrays of 1 wt% photocrosslinking methacrylated HA hydrogels containing different combinations of fibronection, laminin, vitronectin and collagens I, II and IV are screened for endothelial (CD31 and VE-Cadherin) and mesenchymal (SNAIL and SM22) markers by immunostaining. In vitro replication of EMT will indentify the ECM context of the HA signaling required to initiate valve leaflet development.