Abstract: BACKGROUND: Tissue engineering scaffolds constructed by collagen and silk fibroin are widely used in tissue engineering fields such as skin, nerves, blood vessels, bone, and cartilage. Platelet-rich plasma is a platelet concentrate obtained by centrifuging blood twice. It contains a variety of growth factors required for tissue repair and can promote tissue regeneration and wound healing. 
OBJECTIVE: To observe the effect of silk fibroin collagen scaffold combined with platelet-rich plasma on skin wound healing. 
METHODS: Silk fibroin collagen scaffolds and SD rat platelet-rich plasma were prepared separately. Totally 48 8-week-old SD rats were selected, and 2 full-thickness skin defect wounds with a diameter of 2 cm were made on the back of each rat. They were randomly divided into four groups (n=12). In the blank group, normal saline was injected into the defect site. Silk fibroin-collagen composite scaffolds were implanted in the defects of the simple scaffold group. The platelet-rich plasma group was injected with allogeneic platelet-rich plasma at the wound margin. In the combined group, silk fibroin-collagen composite scaffolds were implanted in the defect site and allogeneic platelet-rich plasma was injected into the wound margin. Wound healing rate, wound inflammatory factor level, wound histological morphology and related protein expression were detected after model establishment.
RESULTS AND CONCLUSION: (1) The wound healing rate of the combined group on days 7 and 14 after modeling was higher than that of the blank group, the simple scaffold group, and the platelet-rich plasma group (P < 0.05). (2) The levels of tumor necrosis factor α and interleukin-6 in the combined group on days 7 and 14 days after modeling were lower than those in the blank group, the simple scaffold group, and the platelet-rich plasma group (P < 0.05). (3) On day 14 after modeling, hematoxylin-eosin staining and Masson staining showed that only a few new capillaries and disordered collagen fiber tissue were seen at the defect site of the blank group. A large number of new capillaries and glandular tissue were observed in the other three groups. Collagen fibers were arranged more regularly, among which the combined group had the most new blood vessels, the glandular tissue layers were clearer, and the collagen fibers were arranged more regularly. Immunohistochemical staining displayed that the density of CD31+ cells in blank group, simple scaffold group and platelet-rich plasma group was lower than that in combined group (P < 0.05). (4) Western blot assay results showed that, compared with the blank group, the simple scaffold group, and the platelet-rich plasma group, the protein expression levels of type I collagen, type III collagen, and matrix metalloproteinase inhibitor 1 in the wound were increased in the combined group (P < 0.05), and the protein expression levels of matrix metalloproteinase 3 and matrix metalloproteinase 9 decreased (P < 0.05). (5) It is concluded that fibroin collagen scaffold combined with platelet-rich plasma can promote wound healing by inhibiting inflammatory response, increasing microvascular density and regulating the metabolic balance of extracellular matrix.

Key words: silk fibroin collagen composite scaffold, platelet-rich plasma, full-thickness skin defect, skin injury, wound surface, wound healing