Study on the effects of 1,25(OH)2D3 on cutaneous wound healing and the underlying mechanisms in mice

Abstract

Objective To study the role of 1,25(OH)2D3 in cutaneous wound healing and the underlying mechanisms in mice. Methods Forty 5-week-old male C57BL/6 mice were randomly divided into 5 groups, i.e., wound, wound + vitamin D receptor (VDR) inhibitor, wound+vitamin D receptor (VDR) agonist, wound +vitamin D (VD) powder and normal controls. The wound healing rates were calculated according the photographs of wound size taken at different time points. At the 9th day of wound, ELISA was used to measure serum levels of 1,25(OH)2D3. In addition, wound edge tissue was taken for HE staining and immunohistochemical staining of VDR and CD31. Finally, expression levels of both mRNA and proteins for VDR, Notch1, TNF-α, IL-17A, IL-17F and IL-22 were assessed using real-time quantitative PCR and Western Blot, respectively. Results At the 9th day of wound, the levels of serum 1,25(OH)2D3 and cutaneous VDR and CD31 expression were decreased, while expression levels of TNF-α, IL-17A, IL-17F and IL-22 were increased in the wounded skin compared to the normal controls (P0.05). Compared with the untreated wounded skin, treatments with either VDR agonist or VD powder significantly increased wound healing rate, serum 1,25(OH)2D3 levels and expression levels of cutaneous VDR, CD31 and Notch1, while decreasing cutaneous TNF-α, IL-17A, IL-17F and IL-22 expression (P<0.05). VDR inhibitor increased expression levels of cutaneous TNF-α and IL-22 protein (P<0.01 vs. untreated wound), without significant changes in wound healing rate, serum 1,25(OH)2D3 levels, mRNA for cutaneous VDR, CD31, Notch1, TNF-α, IL-17A, IL-17F and IL-22, and protein levels of Notch1, IL-17A and IL-17F. Moreover, the results of HE staining showed that treatments with either VDR agonist or VD powder significantly decreased inflammatory infiltration in the wounded tissue, while increasing angiogenesis along with dense connective tissue in the dermis and almost complete re-epithelialization in the epidermis. Conclusion In a mouse model of full thickness skin excision wound, 1,25(OH)2D3 promotes wound healing, possibly by inhibition of the expression of TNF-α, IL-17A, IL-17F, and IL-22, and increases in the expression of Notch1 receptor and VDR, and angiogenesis.

Keywords

• calcitriol
• vitamin d receptor
• notch1 receptor
• skin wound healing
• cytokines