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-beta 1). Here, we show that both softening of the implant surfaces and inhibition of the activation of TGF-beta 1 reduce the fibrotic encapsulation of subcutaneous silicone implants in mice. Conventionally stiff silicones (elastic modulus, similar to 2 MPa) coated with a soft silicone layer (elastic modulus, similar to 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 alpha(v) and beta(1) integrins, and activated TGF-beta 1 signalling. In vitro, the recruitment of alpha(v) integrin to focal adhesions and the activation of beta(1) integrin and of TGF-beta were higher in myofibroblasts grown on latency-associated peptide (LAP)-coated stiff silicones than on soft silicones. Antagonizing alpha(v) integrin binding to LAP through the small-molecule inhibitor CWHM-12 suppressed active TGF-beta signalling, myofibroblast activation and the fibrotic encapsulation of stiff subcutaneous implants in mice.