Matrix Metalloproteinase-9 Is Involved in the Regulation of Hair Canal Formation.

Abstract

Hair follicle (HF) morphogenesis is governed by a series of signals exchanged between the epidermal keratinocytes committed to HF-specific differentiation and the mesenchymal cells forming the follicular papilla (Schmidt-Ullrich and Paus, 2005). These interactions lead to the construction of the hair bulb, in which keratinocytes rapidly proliferate and differentiate into several cell populations forming the hair shaft and the inner root sheath. During the final steps of development, the HF elongates up to its maximal length and the hair shaft emerges through the epidermis through the hair canal that is formed at the distal portion of the HF epithelium (Schmidt-Ullrich and Paus, 2005). ...To elucidate a role for MMP-9 in the control of HF development and hair canal formation, its expression was studied by immunohistochemistry in cryosections of embryonic and postnatal skin of C57BL/6 mice (Sharov et al., 2003), and was correlated to the micro-anatomy of the developing hair canal depicted by high-resolution light microscopy, as described previously (Magerl et al., 2001). MMP-9 expression was not observed in the epidermis and developing HF placodes.