Differential Effects of EGF and TGF-β1 on Fibroblast Activity in Fibrin-Based Tissue Equivalents

Transforming growth factor-β1 (TGF-β1) is commonly used to promote matrix production for engineered tissues in vitro, yet it also enhances fibroblast contractility. For applications where contraction is undesirable, we hypothesized that epidermal growth factor (EGF) would yield equivalent mechanical properties without enhancing contractility. In this study, the response of human dermal fibroblasts to EGF (5 ng/mL) and TGF-β1 (5 ng/mL) was determined within hemispheric fibrin-based gels by assessing matrix compaction and strength, cell number, collagen production, and contractility. After 3 weeks, both cytokines enhanced compaction relative to controls, and EGF roughly doubled matrix strength over controls and TGF-β1-treated samples. TGF-β1 induced α-smooth muscle actin (αSMA) expression whereas EGF did not. TGF-β1 also increased retraction following substrate release while EGF reduced retraction. Treatment with cytochalasin D revealed that, regardless of growth factor, approximately 10% of the total retraction was due to residual matrix stress accumulated during cell-mediated remodeling. EGF increased the cell number by 17%, whereas TGF-β1 decreased the cell number by 63% relative to controls. EGF and TGF-β1 stimulated greater collagen content than controls by 49% and 33%, respectively. These data suggest that EGF may be an attractive alternative to TGF-β1 for engineering fibrin-based connective tissue substitutes with adequate strength and minimal tissue contractility.