Photocrosslinking of Gelatin Macromers to Synthesize Porous Hydrogels That Promote Valvular Interstitial Cell Function

The development of novel three-dimensional cell culture platforms for the culture of aortic valvular interstitial cells (VICs) has been fraught with many challenges. Although the most tunable, purely synthetic systems have not been successful at promoting cell survivability or function. On the other hand, entirely natural materials lack mechanical integrity. Here we explore a novel hybrid system consisting of gelatin macromers synthetically modified with methacrylate functionalities allowing for photoencapsulation of cells. Scanning electron microscopy observations show a microporous structure induced during polymerization within the hydrogel. This porous structure was tunable with polymerization rate and did not appear to have interconnected pores. Treatment with collagenase caused bulk erosion indicating enzymatic degradation controls the matrix remodeling. VICs, an important cell line for heart valve tissue engineering, were photoencapsulated and examined for cell-directed migration and differentiation. VICs were able to achieve their native morphology within 2 weeks of culture. The addition of the pro-fibrotic growth factor, transforming growth factor-beta1, accelerated this process and also was capable of inducing enhanced alpha-smooth muscle actin and collagen-1 expression, indicating a differentiation from quiescent fibroblasts to active myofibroblasts as demonstrated by quantitative real-time polymerase chain reaction and immunohistochemistry. Although these studies were limited to VICs, this novel hydrogel system may also be useful for studying other fibroblastic cell types.