Study On Growth Mechanism Of Alpaca Hair Through Transforming Growth Factor-β Receptor Ⅰ Induced By Let-7B

Alpaca coat has good quality because of the thin and long hair with short hair growth cycle, while the hair on ear shin is short and coarse with long hair growth cycle. Studies have shown that TGF-β/Smads signaling pathway has some regulatory role in the development of skin and hair growth process. In order to study the effect of TGFβR I on alpaca hair follicles and hair growth cycle, and to explore the relationship and regulation between TGFβR I and let-7b by the microRNA level, young male alpaca skins were used as object in the study. Firstly, the expression level of TGFβR I in alpaca ear and dorsal skin was detected by RT-PCR technique; the location of TGFβR I protein was detected by ICC-P technique. Secondly, the expression difference of let-7b in alpaca ear and the dorsal skin was verified. Finally, with the dual luciferase reporter vector of TGFPR I the targeted relationship was detected; then using let-7b eukaryotic expression vector transfected alpaca skin fibroblasts and detecting expression of the gene and protein level of TGFβR I in transfected cells by RT-RCR and Western blot so as to explore the regulation type of let-7b on TGFβR I. Experimental results are as follows:(1) To detect endogenous TGFβR I gene in alpaca skin, RT-PCR showed that the relative expression of gene TGFβR I in alpaca ear skin was significantly higher than the dorsal skin (P<0.01); IHC-P showed TGFβR I protein in hair follicle root sheath and hair matrix was significantly positive reaction and was weak reaction in dermal papilla, data analysis showed that the mean optical density values in ear skin was significantly higher than the back (P<0.05)(2) The expression level of let-7b in alpaca ear and dorsal skin was detected by RT-PCR, and the result showed iet-7b in dorsal skin was significantly higher than the ear (P<0.01), which was similar with the previous studies.(3) Using dual-luciferase reporter vector to detect whether let-7b and TGFβR I had a significant relationship, the experimental group showed decreased expression of luciferase, indicating that let-7b and TGFβR I had obvious targeting relationship, i.e. TGFβR I is one of the target genes of let-7b.(4) The results showed that TGFβR I protein expressed in alpaca skin fibroblasts by ICC mothed in alpaca skin fibroblasts.(5) In order to increase the expression level of let-7b in cells, let-7b eukaryotic expression vector was used to transfecte alpaca skin fibroblasts. The results of RT-PCR in the experimental group and the control group of target gene TGFβR I showed no significant difference; TGFβR I protein expression detected by Western blot and the results show that the expression of TGFβR I protein in the experimental group was significantly decreased (P<0.05).In summary:(1) TGFβR I had regulatory effect on alpaca hair growth and the high expression of TGFβR I in alpaca skin may inhibit the elongation of the coat hair. (2) TGFβR I was one of target genes of let-7b. (3) TGFβR I protein in alpaca fibroblasts was down-regulated by let-7b through transcription repression.