Smad7-based biologic targeting epidermis and stroma promotes healing of diabetic wounds in mice and pigs

Impaired healing of diabetic wounds causes significant morbidity and mortality. This study aimed to identify novel mechanisms of diabetic wound healing defects and test a therapeutic intervention using diabetic mouse and pig models. We found Smad7 transgene expression in mouse epidermis promoting wound healing in diabetic db/db mice, with reductions in obesity and blood glucose. To isolate effects of Smad7 on wounds, we created a Smad7-based biologic (Tat-PYC-Smad7) that penetrates wound cells. Topical application of Tat-PYC-Smad7 to diabetic pig and mouse wounds accelerated healing compared to controls. RNAseq analysis of mouse wound samples showed reduced TGFβ/NFκB signaling, leading to faster re-epithelialization and better extracellular matrix remodeling. Tat-PYC-Smad7 also attenuated neutrophil degranulation and NETosis by blocking histone 3 citrullination and inhibiting myeloperoxidase activities. Our study reveals that Tat-PYC-Smad7 promotes diabetic wound healing by targeting keratinocytes and neutrophils, providing insight into cellular mechanisms of diabetic wound healing defects targetable by Smad7-based therapy. To understand the molecular basis of Tat-PYC-Smad7 effects, we performed RNA-seq on db/db mouse wound samples excised at identical locations treated with vehicle or Tat-PYC-Smad7 on days 9 and 11.