Characterization of Photo-Crosslinked Methacrylated Type I Collagen as a Platform to Investigate Lymphatic Endothelial Cell Response

Abstract

Despite chronic fibrosis and associated excess extracellular matrix (ECM) deposition and crosslinking occurring in many pathological conditions, few in vitro studies examine how fibrosis-induced ECM stiffening impacts lymphatic endothelial cells (LEC) behavior and subsequent new lymphatic vessel growth and function. This study examined the stiffening profile of PhotoCol®—commercially available methacrylated type I collagen—photo-crosslinked with photoinitiators Lithium phenyl-2,4,6-trimethylbenzoylphosphinate (LAP), Irgacure 2959 (IRG), and Ruthenium/Sodium Persulfate (Ru/SPS) prior to evaluating PhotoCol® permeability and LEC response to PhotoCol® at low and high stiffness levels representing normal and fibrotic ECM stiffness. Ru/SPS produced the highest maximum stiffness for photo-crosslinked PhotoCol® hydrogels. While Ru/SPS stiffness values did not differ significantly with increased light exposure, permeability decreased significantly with increasing light exposure for 40 kDa dextran. Finally, LECs on softer PhotoCol® appeared smaller with less prominent VE-Cadherin (cell-cell junction) and F-actin expression compared to cells on stiffer PhotoCol®. Overall, PhotoCol® with Ru/SPS photoinitiator provides the fibrillar microstructure and dynamic stiffness range that enables systematic study of LEC stiffness responses relevant to the stiffened ECM observed in pathologies with significant fibrotic activity. Therefore, this study demonstrates the utility of PhotoCol® with Ru/SPS for disease modeling applications, particularly modeling lymphatic vascular growth and function during fibrosis.