PEP donates bioactive TGF-β activating proliferation in dermal progenitors in vitro. (A): Representative western blot of TGF-β1in PEP exosomes. GAPDH was used as a loading control. Pro-collagen I (B) and III (C) synthesis in TGF-β (5 ng/ml), fibroblast-derived exosomes or PEP treated fibroblasts. (D): Schematic illustration of the mechanism of PEP-induced wound healing in vitro. (E): Quantification of SMAD2, RAS, MKK3, RHOA, P38, and Periostin expression in PEP treated keratinocytes. (F): Quantification of SMAD2, RAS, MKK3, ERK1, and TAK1 expression in PEP treated fibroblasts. A 2-tailed unpaired Student's t-test was used for each group compared to the untreated control group. *p < 0.05, **p < 0.01.