PT637 peptide disrupts Spata13-TGFβRI, inhibiting infection-driven capsular contracture in rats

Capsular contracture is a common and debilitating complication following breast implant surgery, characterized by excessive collagen deposition and the transformation of fibroblasts into myofibroblasts. Current treatments are often inadequate, highlighting a critical need for targeted therapies. While bacterial biofilm formation and aberrant TGF-β signaling are known contributors to this fibrotic process, the precise molecular links between infection and the activation of fibrosis remain poorly understood. Identifying specific mediators within the TGF-β/Smad signaling pathway that are upregulated by infection could unlock novel therapeutic avenues for preventing or reversing this condition.

Researchers investigated the molecular mechanisms linking infection to fibrosis using both in vitro fibroblast models and in vivo rat capsular contracture assays. The study employed a multi-faceted approach, combining transcriptomics, protein interaction analysis, and targeted mutagenesis to pinpoint key mediators. Functional assays were utilized to quantify collagen synthesis (via hydroxyproline content), assess fibroblast proliferation (CCK-8 assay), and measure myofibroblast differentiation markers (α-SMA). A specific competitive peptide, PT637, was rationally designed to disrupt the identified Spata13-TGFβRI protein-protein interaction. The in vivo model involved Staphylococcus epidermidis biofilm formation in conjunction with silicone implants to induce contracture.

The study revealed that Staphylococcus epidermidis biofilm, in synergy with silicone implants, significantly upregulated Spata13 expression, which subsequently activated TGF-β/Smad signaling and promoted fibroblast activation. Mechanistically, Spata13 was found to bind directly to TGF-β receptor I (TGFβRI) via its Ser637 residue. Functional experiments demonstrated that Spata13 knockdown effectively suppressed α-SMA expression and collagen deposition in vitro. Furthermore, the known TGFβRI inhibitor LY2157299 was shown to attenuate fibrosis in the in vivo rat model. Most strikingly, the designed competitive peptide PT637 successfully disrupted the Spata13-TGFβRI interaction, leading to a significant reduction in both fibrosis markers and capsular thickness in biofilm-challenged rats. This establishes Spata13 as a novel, critical regulator of infection-associated fibrosis. > PT637 specifically disrupted the Spata13-TGFβRI interaction, leading to a marked reduction in fibrosis markers and capsular thickness in vivo, demonstrating a targeted therapeutic effect.