Dermal papilla cells (DPCs), an important component of hair follicles, its proliferation and apoptosis directly regulate and maintain the growth of hair follicles. All-trans-retinoic acid (ATRA) plays a critical role in hair growth. In this study, the effects of ATRA on cultured mink hair follicle growth were studied by administration of different concentrations of ATRA for 12 days in vitro. In addition, the proliferation and apoptosis of DPCs were measured after treating with ATRA. The mRNA and protein levels of hair follicle growth associated factor transforming growth factor-β2 (TGF-β2) and the phosphorylation levels of Smad2/3 were determined. Moreover, TGF-β type I and type II receptor inhibitor LY2109761 and specific inhibitor of Smad3 (SIS3) were administered to investigate the underlying molecular mechanism. The results showed that ATRA inhibited hair follicle growth, promoted TGF-β2 expression and activated phosphorylation of Smad2/3. In addition, ATRA inhibited cell proliferation by arresting the cell cycle at G1 phase and induced apoptosis of DPCs by enhancing the ratio of Bax/Bcl-2 and promoted the cleavage of caspase-3. Furthermore, LY2109761 or SIS3 partially reversed the decreased cell viability, increased apoptosis that were induced by ATRA. In conclusion, ATRA could inhibit hair follicle growth via inhibiting proliferation and inducing apoptosis of DPCs partially through the TGF-β2/Smad2/3 pathway.

真皮乳头细胞（DPCs）是毛囊的重要组成部分，其增殖和凋亡直接调节和维持毛囊的生长。全反式视黄酸 (ATRA) 在头发生长中起着关键作用。在这项研究中，通过在体外施用不同浓度的 ATRA 12 天来研究 ATRA 对培养的水貂毛囊生长的影响。此外，在用ATRA处理后测量DPC的增殖和凋亡。测定了毛囊生长相关因子转化生长因子-β2 (TGF-β2) 的 mRNA 和蛋白质水平以及 Smad2/3 的磷酸化水平。此外，还施用了 TGF-β I 型和 II 型受体抑制剂 LY2109761 和 Smad3 特异性抑制剂（SIS3）以研究潜在的分子机制。结果表明，ATRA抑制毛囊生长，促进TGF-β2表达并激活Smad2/3的磷酸化。此外，ATRA通过将细胞周期阻滞在G1期来抑制细胞增殖，并通过提高Bax/Bcl-2的比例来诱导DPCs凋亡，并促进caspase-3的裂解。此外，LY2109761 或 SIS3 部分逆转了降低的细胞活力，ATRA 诱导的细胞凋亡增加。总之，ATRA可以部分通过TGF-β2/Smad2/3通路抑制DPCs的增殖和诱导其凋亡，从而抑制毛囊生长。