Suppression of the fibrotic encapsulation of silicone implants by inhibiting the mechanical activation of pro-fibrotic TGF-β

The fibrotic encapsulation of implants involves the mechanical activation of myofibroblasts and of pro-fibrotic transforming growth factor beta 1 (TGF-β1). Here, we show that both softening of the implant surfaces and inhibition of the activation of TGF-β1 reduce the fibrotic encapsulation of subcutaneous silicone implants in mice. Conventionally stiff silicones (elastic modulus, ~2 MPa) coated with a soft silicone layer (elastic modulus, ~2 kPa) reduced collagen deposition as well as myofibroblast activation without affecting the numbers of macrophages and their polarization states. Instead, fibroblasts around stiff implants exhibited enhanced intracellular stress, increased the recruitment of αv and β1 integrins, and activated TGF-β1 signalling. In vitro, the recruitment of αv integrin to focal adhesions and the activation of β1 integrin and of TGF-β were higher in myofibroblasts grown on latency-associated peptide (LAP)-coated stiff silicones than on soft silicones. Antagonizing αv integrin binding to LAP through the small-molecule inhibitor CWHM-12 suppressed active TGF-β signalling, myofibroblast activation and the fibrotic encapsulation of stiff subcutaneous implants in mice. The fibrotic encapsulation of subcutaneous silicone implants in mice can be suppressed by softening the implant surface or inhibiting the integrin-mediated activation of transforming growth factor beta 1.