Factors that regulate hair matrix cell division within the hair follicles and control hair growth cycle have been poorly understood untill now. One of the main.causes seems to be lack of good in vitro models.

This study was performed to investigate the hair growth promoting potencies of several agents including individual components of keratinocyte growth media.

Several agents such as epidermal growth factor, insulin, bovine pituitary extract which were contained in keratinocyte growth media as well as minoxidil and transforming growth factor-α were added to the isolated anagen hair follicles. Measuring the length of hair follicle, thymidine and leucine uptake were used for hair growth parameter.

Isolated anagen hair follicles in keratinocyte growth media showed a significant increase in length over 48 hours. [Methyl-³H] thymidine and [U-¹⁴Cl leucine uptake were sustained at basal state as well as over 48 hours and [methyl-³H] thymidine uptake increased in the matrix cells under autoradiography. Insulin with a concentration above 0.5µg/ml and transforming growth factor-α with a concentration above 10ng/ml showed a promoting effect on hair growth. However, other agents did not promote hair growth at all.

Our in vitro model resembles the in vivo status of hair growth for a limited period of time and we think that normal human hair organ culture may be a useful model for developing hair growth promoting agents in vitro.