Clickable, photodegradable hydrogels to dynamically modulate valvular interstitial cell phenotype.

Abstract

Biophysical cues are widely recognized to influence cell phenotype. While this evidence was established using static substrates, there is growing interest in creating stimulus-responsive biomaterials that better recapitulate the dynamic extracellular matrix. Here, a clickable, photodegradable hydrogel substrate that allows the user to precisely control substrate elasticity and topography in situ is presented. The hydrogels are synthesized by reacting an 8-arm poly(ethylene glycol) alkyne with an azide-functionalized photodegradable crosslinker. The utility of this platform by exploiting its photoresponsive properties to modulate the phenotype of porcine aortic valvular interstitial cells (VICs) is demonstrated. First, VIC phenotype is monitored, in response to initial substratum modulus and static topographic cues. Higher modulus (E ≈ 15 kPa) substrates induce higher levels of activation (≈70% myofibroblasts) versus soft (E ≈ 3 kPa) substrates (≈20% myofibroblasts). Microtopographies that induce VIC alignment and elongation on low modulus substrates also stimulate activation. Finally, VIC phenotype is monitored in response to sequential in situ manipulations. The results illustrate that VIC activation on stiff surfaces (≈70% myofibroblasts) can be partially reversed by reducing surface modulus (≈30% myofibroblats) and subsequently re-activated by anisotropic topographies (≈60% myofibroblasts). Such dynamic substrates afford unique opportunities to decipher the complex role of matrix cues on the plasticity of VIC activation.