Development of finasteride polymer microspheres for systemic application in androgenic alopecia

The use of finasteride for alleviating hair loss has been investigated, and it has been applied as an oral dose medication. However, due to the inconvenience of daily drug administration over long period of time, novel controllable finasteride delivery has been actively investigated. As a novel method of finasteride delivery, the development of finasteride‑loaded microspheres for subcutaneous administration is becoming increasingly pharmaceutically important. Therefore, the present study aimed to use finasteride‑loaded microspheres in a controlled manner in an attempt to overcome the limitations of the oral administration of finasteride and to cause fewer adverse effects. Finasteride‑loaded microspheres containing poly(lactic‑co‑glycolic acid) and finasteride at a ratio of 4:1 were prepared, and a testosterone‑induced androgenic alopecia mouse model was used. Following observation for 10 weeks, the percentage hair growth was 86.7% (total hair growth 60%, partial hair growth 26.7%) in the orally‑applied finasteride‑treated group as a positive control, and 93.3% (total hair growth 60%, partial hair growth 33.3%) in the finasteride‑loaded microspheres‑treated group. Serum dihydrotestosterone levels began to decrease at week 6 in the orally‑applied finasteride‑ and finasteride‑loaded microsphere‑treated groups. In addition, the finasteride‑loaded microspheres‑treated group exhibited similar follicular number, follicular length, anagen/telogen ratio and hair bulb diameter values to those of the orally‑applied finasteride‑treated group. Furthermore, the finasteride‑loaded microspheres increased the activities of phosphoinositide 3‑kinase/protein kinase B and Wnt/β‑catenin in relation to hair follicle cell growth signaling in mouse skin, and suppressed the apoptosis of hair follicle cells by reducing the expression of transforming growth factor‑β2 and caspase‑3, which are indicators of apoptosis. In conclusion, the administration of a single injection of finasteride‑loaded microspheres was effective in treating testosterone‑induced alopecia. Furthermore, it led to equivalent hair growth effects when compared with orally‑applied finasteride, thus revealing the possibility of effective treatment via different routes of administration.