Thymic Peptides Differentially Modulate Human Hair Follicle Growth

The study explored the effects of thymic peptides (TPs) on human hair follicle (HF) growth, discovering that thymosin ß4 (TB4) and prothymosin alpha (PTMA) are transcribed in the HF epithelium and that their proteins are present in the HF. In vitro experiments demonstrated that thymulin (TYL) at 10 pg/ml increased hair shaft growth rate and prolonged the anagen phase, while TB4 at higher concentrations (100 and 1,000 ng/ml) slightly decreased hair shaft elongation and prematurely induced the catagen phase. Thymosin alpha 1 at 1,000 ng/ml had a slight growth-inhibiting effect but did not significantly alter HF cycling. The pilot study involved HFs from three different patients, showing interindividual variations in response to TP stimulation. These findings suggest the potential therapeutic use of TPs, especially TYL, in regulating human hair growth, although the exact mechanisms remain unknown. The study's strength is limited by not specifying the number of hair follicles tested.