Effect and mechanisms of Polygonatum kingianum (polygonati rhizome) on wound healing in diabetic rats

Diabetic dermatopathy is one of the most serious and common complications of diabetes. It has been found that high glucose can lead to abnormal glycometabolism. The skin microenvironment pollution caused by the increase in glucose and the oxidative stress mediated by the deposition of advanced glycation end products can lead to invisible skin injury, and the interaction between them is the key factor that makes the skin wounds of diabetic rats difficult to heal. Therefore, the main task of promoting healing is to reduce blood glucose levels and relieve the deposition of advanced glycation end products. Polygonatum kingianum Collett & Hemsl (PK) of Asparagaceae is planted in Yunnan, China, and is used by the Bai, Hani and Wa nationalities as a traditional medicine for preventing and treating diabetes. To study the effects of PK extract on skin wound healing in diabetic rats and to explore the regulatory mechanism of PK on wound microenvironment pollution, the antioxidative stress signaling pathway and latent injury of wound skin tissue. First, wounds were prepared after diabetic rats were given PK extract by gavage for 4 weeks, and then gavage was continued for 2 weeks to observe and calculate the wound healing rate. A scanning electron microscope was used to observe the pathomorphological changes in the skin tissue at the edge of the wound. Western blotting was used to detect protein expression. Immunohistochemistry was used to detect the expression of CD34, AGEs, bFGF and VEGF. The Nrf2/HO-1 signaling pathway in skin tissue was detected by fluorescence quantitative PCR. Serum biochemical indicators and inflammatory cytokine levels were detected by a kit. After PK treatment, the wound healing rate increased significantly (P < 0.001), the infiltration of inflammatory cells in skin tissue of DM lesion rats decreased, the number of new blood vessels increased, and the epidermis and dermis thickened. The content of glucose, AGEs, RAGE protein and RAGE mRNA in skin decreased significantly (P < 0.05, P < 0.01, P < 0.001), while the expression of Nrf2 mRNA, HO-1 mRNA, CD34, bFGF and VEGF increased significantly (P < 0.05, P < 0.01, P < 0.001). The levels of SOD, GSH, MMP-9 and MMP-2 in skin decreased (P < 0.05, P < 0.01, P < 0.001), but the level of TIMP-2 increased (P < 0.001). GSP, GHb and ICAM-1 in plasma decreased (P < 0.05, P < 0.01, P < 0.001), while T-AOC, SOD and FINS increased (P < 0.05, P < 0.01). The levels of MDA, TNF-, IL-6, IL-2 and IFN-γ in plasma and wound skin tissue decreased (P < 0.05, P < 0.01, P < 0.001). PK can reduce the infiltration of inflammatory cells and glucose content in the skin tissue at the edge of the wound, reduce inflammatory factors in skin and plasma, and increase angiogenesis, thus improving the wound healing rate. PK can alleviate the microenvironment pollution caused by AGEs and glucose metabolism disorder in diabetic rats and induce antioxidant activity through the Nrf 2/HO-1 signaling pathway, thus reducing oxidative damage and offsetting endogenous skin damage and hidden damage.