To investigate the effect and mechanism of type ⅩⅦ collagen (COL17) on hair growth in mice with androgenetic alopecia (AGA).

Forty-eight C57BL/6J mice were used to establish AGA model (the back hair of the mice was removed and dihydrotestosterone solution was applied) and divided into 6 groups of 8 mice each by random number table. Negative control group, injection of saline in the depilated area (single point injection of 0.05 ml, 5 points in total); positive control group, topical application of 5% minoxidil tincture in the depilated area, 1 ml/d; COL17 low, medium and high concentration groups, injection of 0.5, 1.0 and 2.0 mg/ml COL17 in the depilated area respectively (single point injection of 0.05 ml, 5 points in total); type Ⅲ and ⅩⅦ collagen (COL3+ COL17) combined high concentration group, injection of 2.0 mg/ml COL3 and COL17 in the depilated area (single point injection of 0.05 ml, 5 points in total). The total treatment time was 21 days, during which the hair growth of mice in each group was observed and recorded. After 21 days, the skin and subcutaneous tissue in the depilated area of the mice were taken to make pathological sections for HE staining, and the number and morphological changes of hair follicles were observed; fresh skin tissue in the depilated area of the mice was taken for total RNA sequencing analysis, and the differentially co-expressed genes were annotated by gene ontology (GO) functional annotation, Kyoto encyclopedia of genes and genomes (KEGG) pathway analysis and gene set enrichment analysis (GSEA).

After 21 days of treatment, compared with the negative control group, the depilation area on the back of the mice in the positive control group, COL17 high concentration group, and COL3+ COL17 combined high concentration group was significantly reduced, and HE staining showed that the number of hair follicles was also significantly increased. Pearson correlation analysis, principal component analysis and cluster heat map between groups showed that COL17 high concentration group had high gene correlation with the positive control group (R²=0.95, P=0.024), and the gene expression was relatively close, with 3 882 differentially expressed genes (1 705 up-regulated and 2 177 down-regulated) in the two groups, while COL3+ COL17 combined high concentration group had the highest gene correlation with the positive control group (R²=0.96, P=0.001), and the gene expression was the closest, with 1 289 differentially expressed genes (385 up-regulated and 904 down-regulated). KEGG analysis showed that compared with the negative control group, the positive control group, COL17 high concentration group and COL3+ COL17 combined high concentration group of mice all upregulated Wnt signaling pathway, cell adhesion molecules and hedgehog signaling pathway related to hair growth. GO enrichment analysis suggested that COL17 high concentration group and COL3+ COL17 combined high concentration group had upregulated genes related to skin development and hair cycle. GSEA enrichment analysis found that COL17 high concentration group had upregulated genes related to fibroblast proliferation and interleukin-1 secretion, while COL3+ COL17 combined high concentration group had upregulated genes related to fibroblast migration, clearance of apoptotic cells and accelerated metabolism of reactive oxygen species.

Local injection of 2.0 mg/ml COL17 has a certain promoting effect on hair growth in AGA model mice, and the effect is more significant after combined injection of 2.0 mg/ml COL3. Activation of Wnt signaling pathway is one of the main mechanisms of COL17 promoting hair growth.

Hair; Androgenetic alopecia; Type ⅩⅦ collagen; Type Ⅲ collagen; Hair regeneration