Valvular interstitial cells (VICs) are active regulators of valve homeostasis and disease, responsible for secreting and remodeling the valve tissue matrix. As a result of VIC activity, the valve modulus can substantially change during development, injury and repair, and disease progression. While two-dimensional biomaterial substrates have been used to study mechanosensing and its influence on VIC phenotype, less is known about how these cells respond to matrix elasticity in a three-dimensional environment. Here, we synthesized MMP-degradable poly(ethylene glycol) (PEG) hydrogels with elastic moduli ranging from 0.24 kPa to 12 kPa and observed that cell morphology was constrained in stiffer gels. The adhesive peptide CRGDS was incorporated to facilitate cell attachment to the hydrogel. To vary gel stiffness without substantially changing cell morphology, cell-laden hydrogels were cultured in the 0.24 kPa gels for 3 days to allow VIC spreading, and then stiffened in situ via a second, photoinitiated thiol-ene polymerization of 8-arm PEG-norbornene and 8-arm PEG-SH such that the gel modulus increased from 0.24 kPa to 1.2 kPa or 13 kPa. VICs encapsulated within soft gels exhibited αSMA stress fibers (~40%), a hallmark of the myofibroblast phenotype prevalent in valve development and disease. Interestingly, in stiffened gels, VICs became deactivated to a quiescent fibroblast phenotype, suggesting that matrix stiffness directs VIC phenotype independent of morphology, but in a manner that depends on the dimensionality of the culture platform. Collectively, these studies present a versatile method for dynamic stiffening of hydrogels and demonstrate the significant effects of dimensionality on VIC myofibroblast properties.

Dynamic stiffening of poly(ethylene glycol)-based hydrogels to direct valvular interstitial cell phenotype in a 3D environment

249th National Meeting (2015)

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