Characterization of Growth Secondary Hair in Min Pig Activated by Follicle Stem Cell Stimulated by Wnt and BMP Signaling Pathway

SIMPLE SUMMARY: The Min pig is a national-level protected pig that is recognized as a rare animal in China, lives in a constantly cold environment in the north of China, and has excellent characteristics compared with other commercial pigs. The Min pig has the specific character of secondary hair growth in winter and seasonal cycling. International research on hair follicles is mainly focused on human and mice hair, including hair follicle regeneration and hair loss treatment. Research on hair follicles in pigs is limited. The structure and morphology of hair follicles from Min pigs are different from those of lean-type pigs, such as Yorkshire and Berkshire pigs, which do not grow secondary hairs in the adult stage. In this study, there were significant gene expression differences with high-throughput sequencing to determine the primary and secondary hairs. Based on skin blocker experimental results, we can infer that the Wnt and BMP signaling could stimulate follicle stem cells in the Min pig. ABSTRACT: In China, the national-level protected pig, the Min pig, is characterized by the development of secondary hairs and hair follicles in winter. Factors that dominate the genotype in the growth of secondary hairs are not clear through the concrete cell signaling pathways. This study compared hair phenotypes based on morphological structure, transcriptomics, and potential targeting molecules in the breeds of Min, Berkshire, and Yorkshire pigs. The results indicated that Min pigs have specific characteristics for the growth of secondary hairs compared with the Berkshire and Yorkshire pigs. The transcriptome analyses and quantitative reverse transcription-polymerase chain reaction results revealed that secondary hair growth was activated by follicle stem cells. The specific inhibitors of Wnt and BMP were studied using respective signals. The density of follicles, activity of follicle stem cells, and relative gene expression results have shown that Wnt and BMP stimulate the activity of follicle stem cells, and the Wnt signaling molecule has a significantly better effect than the BMP signaling molecule on stem cells. Wnt and BMP can promote the growth of local secondary hair and gene expression. Therefore, this study was conducted to verify the development mechanisms of secondary hairs, which have potential applications in laboratory animals and comparative medicine.