Endocytosis-mediated healing: recombinant human collagen type III chain-induced wound healing for scar-free recovery

Scar formation can be effectively prevented when the proportion of collagen type I (Col I)/type III (Col III) is reduced. Unlike Col III, recombinant human collagen type III chain (RHC III chain) does not possess a triple helical structure. This study aimed to elucidate the capacity of fibroblasts to uptake RHC III chain, reduce the Col I/Col III ratio and determine its effects on wound healing and scar. RHC III chain demonstrates qualified cell compatibility. In cell experiments, immunofluorescence and western blot (WB) analyses revealed an increase in the polyhistidine tag level, indicating that RHC III chain in internalized by these cells. Transmission electron microscopy showed increased intracellular phagocytic activity, indicating that RHC III chain enters fibroblasts by endocytosis. The immunofluorescence and WB showed that Col III synthesis enhanced, and Col I/Col III ratio reduced. However, the polyhistidine tag disappeared with time, indicating that RHC III chain degraded within cells and then synthesized into Col III. The content of newly synthesized Col III increases, but real-time fluorescence quantitative showed a decrease in Col III related gene content suggests the formation of negative feedback. However, due to the sufficient raw materials, the amount of Col III synthesis is still increasing, leading to the reduction of the ratio of type I collagen/type III collagen, which beneficial to wound healing and reduce scar hyperplasia. In animal experiments, the SD rat full-thickness skin defect model of wound suggests that RHC III chain also takes effect through endocytosis and ultimately promotes wound healing. The rabbit ear scar model suggests that RHC III chain inhibits scar proliferation by reducing the ratio of Col I/Col III. In summary, RHC III chain was endocytosed by fibroblasts to promote native Col III synthesis, as well as promote wound healing and reduce scar hyperplasia.