Hair Follicle Terminal Differentiation Is Orchestrated by Distinct Early and Late Matrix Progenitors

Abstract

SUMMARY During development and regeneration, matrix progenitors undergo terminal differentiation to form the concentric layers of the hair follicle. These differentiation events are thought to require signals from the mesenchymal dermal papilla (DP); however, it remains unclear how DP-progenitor cell interactions govern specific cell fate decisions. Here, we show that the hair follicle differentiated layers are specified asynchronously, with early matrix progenitors initiating differentiation prior to surrounding the DP. Furthermore, these early matrix cells can undergo terminal differentiation in the absence of Shh, BMP signaling, and DP maturation. Whereas early matrix progenitors form the hair follicle companion layer, later matrix populations progressively form the inner root sheath and hair shaft. Together, our findings characterize some of the earliest terminal differentiation events in the hair follicle, and reveal that the matrix progenitor pool can be divided into early and late phases based on distinct temporal, molecular and functional characteristics.

Microcomedones in non‐lesional acne prone skin New orientations on comedogenesis and its prevention

“…Table 1 shows that amongst the keratins we identified K75 and K79 were well represented. 3,10,11 Importantly, Fig. This indicates that CSSS indeed extracts key structural elements of the nascent comedone epithelium.…”

“…10 • Ongoing exposure to comedogens (or comedone reversers). 10 • Ongoing exposure to comedogens (or comedone reversers).…”

“…3,6 Monitoring of microcomedones in NLSAP is therefore a key objective tool for checking the potential of any skin-care product aimed at maintaining healthier skin in acne patients, and thereby at reducing the use of drug therapy. 10,11 One paradigm of comedogenesis are the typical skin lesions induced by 2,3,7,8-tetrachlorodibenzo-p-dioxin (TCDD) called 'MADISH' (for 'metabolising acquired dioxin-induced skin hamartoma). 5 Recent advances in the biology of pilosebaceous progenitors have provided new concepts for understanding comedogenesis.…”

Loss of Gata6 causes dilation of the hair follicle canal and sebaceous duct

“…We further noted that nuclear Gata6 was not detected in the epidermis or lower anagen follicle. This included early anagen, when matrix progenitors initially give rise to K79 + cells that form the companion layer, as well as later stages, when matrix cells surround the mesenchymal dermal papilla (Figure B). We confirmed these results using a second independent antibody against Gata6 and similarly did not detect nuclear Gata6 in matrix cells or their differentiated progeny (Figure ).…”

“…B, Lack of Gata6 (green) in early‐ (left) or mid‐anagen (right) control follicles. On left, K79 (red) identifies early companion layer (arrow) . C, Nuclear Gata6 (green, arrow) in upper domain of human hair follicle.…”