Low-Molecular-Weight Fish Collagen Peptide Enhances Hair Regrowth via Activation of Proliferative Signaling and Suppression of Inhibitory Pathways

Collagen peptides have been widely studied for their beneficial effects on skin health; however, their potential role in hair growth remains insufficiently explored. This study aimed to investigate the effects of orally administered low-molecular-weight fish collagen peptide (SH-GT) on hair regrowth and its underlying mechanisms in a hair-removed C57BL/6J mouse model. Mice were administered SH-GT (100, 300, or 600 mg/kg body weight) or a positive control (Pansidil, 400 mg/kg) daily for 28 days. SH-GT significantly enhanced hair regrowth, as evidenced by the increased hair growth area. Histological analysis revealed increased dermal thickness and visible hair follicle structures in SH-GT-treated groups. At the molecular level, SH-GT upregulated proliferation-related proteins, including PCNA and Cyclin D1, and activated Wnt/β-catenin signaling. In addition, SH-GT enhanced PI3K/Akt/mTOR signaling, suggesting improved cellular growth and survival. Conversely, SH-GT suppressed hair growth inhibitory pathways by reducing BMP4 expression and decreasing Smad phosphorylation. Furthermore, SH-GT increased the mRNA expression of growth factors such as IGF-1, HGF, VEGF, EGF, and FGF7. In conclusion, SH-GT promotes hair regrowth by simultaneously activating proliferation-related signaling pathways and suppressing inhibitory mechanisms, thereby improving the dorsal skin microenvironment associated with hair regrowth. These findings suggest that SH-GT may serve as a promising functional ingredient for improving hair growth.