Substratum compliance modulates corneal fibroblast to myofibroblast transformation

Purpose. The transformation of fibroblasts to myofibroblasts is critical to corneal wound healing, stromal haze formation, and scarring. It has recently been demonstrated that the provision of biomimetic substratum topographic cues inhibits the progression toward the myofibroblast phenotype under the influence of transforming growth factor β1 (TGF-β1). The objective of this study was to determine the effect of another fundamental biophysical cue, substrate compliance, on TGF-β1-induced myofibroblast transformation of primary corneal cells isolated from human and rabbit corneas. Methods. Human and rabbit corneal fibroblasts were cultured on surfaces of varying substrate compliance (4-71 kPa) and tissue culture plastic (TCP) (>1 gigapascal [GPa]). Cells were cultured in media containing TGF-β1 at concentrations of 0, 1, or 10 ng/mL for 72 hours. RNA and protein were collected from cells cultured on polyacrylamide gels and TCP and were analyzed for the expression of α-smooth muscle actin (α-SMA), a key marker of myofibroblast transformation, using quantitative PCR, immunocytochemistry, and Western blot. Results. Cells grown on more compliant substrates demonstrated significantly reduced amounts of α-SMA mRNA compared with TCP. Immunocytochemistry and Western blot analysis determining the presence of α-SMA corroborated this finding, thus confirming a reduced transformation to the myofibroblast phenotype on more compliant substrates compared with cells on TCP in the presence of TGF-β1. Conclusions. These data indicate that substrate compliance modulates TGF-β1-induced expression of α-SMA and thus influences myofibroblast transformation in the corneal stroma. This provides further evidence that biomimetic biophysical cues inhibit myofibroblast transformation and participate in stabilizing the native cellular phenotype.