The expression of stratum corneum chymotryptic enzyme in human anagen hair follicles: further evidence for its involvement in desquamation-like processes.

At sites with a continuous formation of cornified epithelia, there is need for continuous cell shedding in order to maintain normal anatomy. Stratum corneum chymotryptic enzyme (SCCE) has been suggested to mediate this process by degrading intercellular cohesive structures in interfollicular epidermis. In the hair follicle, there are several different kinds of cornification processes. With the exception of the formation of the hair shaft, these processes lead to a continuous formation of structures that have to be shed continuously in order to avoid distorting the anatomy of the follicle. In this work, we have investigated the possible involvement of SCCE in the turnover of cornified cells in anagen hair follicles. Using immunohistochemistry, we demonstrated the expression of SCCE in all parts of the follicle where cells are keratinized and eventually shed, i.e. in the uppermost follicle (distal to the opening of the sebaceous duct), in the sebaceous duct and in all parts of the inner root sheath (IRS). SCCE expression was also seen in those cells of the outer root sheath that are believed to move along with the IRS from the bulb and eventually become keratinized and sloughed in the part of the follicle situated between the terminal edge of the IRS and the opening of the sebaceous duct. We could not detect any SCCE in cells forming the hair shaft. Thus, there was a strong correlation between SCCE expression and the continuous formation and shedding of cornified epithelia in anagen hair follicles. This correlation was stronger for SCCE than for a number of common markers of terminal differentiation in keratinocytes. Our results give further support to a part for SCCE in desquamation-like processes. Whether SCCE is involved in diseases affecting hair growth remains to be elucidated.