The Role Of Fibroblast Growth Factor 7 And Fibroblast Growth Factor 2 In Male Androgenetic Alopecia Pathogenesis

Backgrounds and ObjectivesHair growth is a complex and cyclical process, which includes anagen, catagen, and telogen. The mechanism of regulation of the hair cycle is not yet fully understood. Reciprocal interactions among dermal papilla, hair matrix, adjacent epithelial, outer root sheath mediates continuity and transition of each cycle. Dermal papilla exist at the base of hair follicle, surrounded by hair matrix. in vitro and in vivo, dermal papilla can promote proliferation and differentiation of keratinocytes. The proliferation of outer root sheath cell and adjacent hair matrix cells are affected by the signals from the dermal papilla cells, and dermal papilla monitor hair follicle cycle. Sonic hedgehog(Shh) pathway, insulin-like growth factor(IGF), wnt/β-catenin pathway, bone morphogenetic protein(BMP), fibroblast growth factor(FGF), transforming growth factor-β(TGF-β), hepatocyte growth factor(HGF) involved in the signals.Androgenetic alopecia(AGA) is common in men. Dihydrotestosterone(DHT), type II 5α-reductase, androgen receptor(AR), paracrine pathway may involved in the pathogenesis of androgenetic alopecia, but now DHT is considered major causative factor of AGA. Type II 5α-reductase converts testosterone into DHT, and it has a profound effect on the pathogenesis of AGA. Type II 5α-reductase inhibitor is the firstline therapy of male androgenetic alopecia, which can reduce the concentrations of DHT in serum and scalp. Currently the molecular mechanism of AGA modulated by DHT has not fully elucidated.According to the previous studies, the secretion of TGF-β in dermal papilla cells from alopecia area was androgen-dependent, which suppress the proliferation of epithelial cells. Androgen can stimulate dermal papilla cells from beard secreting IGF-1, which contribute to the progress of epithelial cells. To further study the paracrine pathway of DHT-dependence, We explore whether FGF2 and FGF7 involved in the pathogenesis of male AGA.Experimental methods and results1. Dermal papilla cells extracted from human scalp, cultured dermal papilla cells, detected the expression of AR during subculture.Result: in vitro, Dermal papilla cells in third passage has higher expression of AR than sixth passage.2. Constructed AR adenoviral vector and then transfected vector to dermal papilla cells. The expression of AR was surveyed by RT-PCR, immunofluorescence, western blot. Whether the adenoviral vector promote or inhibit the proliferation of human dermal papilla cells, it reveals by CCK-8.Result: the proliferation rate of dermal papilla cells had no significant difference among the control group, empty vector group and AR overexpression group.3. AR overexpression dermal papilla cells were used in following steps. According to the experiment whether contain DHT or 0.01% ethanol, the groups of bald frontal dermal papilla cells include: 0M(0mol/L)-DHT group, 0.01% ethanol group, 10 n M(10nmol/L)-DHT group. The groups of occipital dermal papilla cells include: 0MDHT group, 0.01% ethanol group, 10 n M-DHT group. The expression of FGF2 and FGF7 detected by RT-PCR、Western blot、ELISA.Result: in the bald frontal dermal papilla cells, 0.01% ethanol group had higher FGF7 expression than 10 n M-DHT group[(1.58±0.15) vs(0.83±0.18) P=0.018]. 0M-DHT group had higher FGF2 expression than 10 n M-DHT group[(0.90±0.19) vs(0.41±0.11) P=0.22]. In occipital dermal papilla cells, no statistically significant difference between each group. The protein levels of FGF2 and FGF7 detected by western blot : in the bald frontal dermal papilla cells, the protein levels of FGF7 in 0M-DHT group was higher than 10 n M-DHT group[(0.393±0.060) vs(0.282±0.019) P=0.038]. The protein levels of FGF2 in 10 n M-DHT group was higher than 0.01% ethanol group[(0.294±0.019) vs(0.201±0.058) P=0.021]. In occipital dermal papilla cells, the protein levels of FGF7 in 10 n M-DHT group was higher than 0n M-DHT group[(0.207±0.025) vs(0.108±0.038) P=0.038], while the protein levels of FGF2 has no statistically signi ficance in each group. ELISA detect the expression of FGF2 and FGF7: in the bald frontal dermal papilla cells, compared with 0n M-DHT group, when cultured with 10 n M-DHT, the secretion of FGF7 was increased from 216.446pg/m L to 249.942pg/m L, while the secretion of FGF2 decreased from 123.125pg/m L to 51.667 pg/m L. Compared with 0.01% ethanol group, when added 10 n M-DHT to medium, the secretion of FGF2 increased from 12.381 pg / m L to 51.667 pg / m L.Conclusion1. When cultured in vitro, The expression of AR in dermal papilla cells was unstable during subculture.2. AR recombinant adenovirus vector had no significant effect on the proliferation of dermal papilla cells.3. DHT treatment revealed a decrease of FGF7 protein in dermal papilla cells, while promoted secretion of FGF7 and FGF2.We have initially confirmed that FGF7 and FGF2 are involved in the pathogenesis of AGA, We provides some experimental basis and foundation for intensive study.