Hair follicle stem cells in the pathogenesis of the scarring process in cutaneous lupus erythematosus

Lupus erythematosus (LE) is an autoimmune disease that can affect one or more internal organs (systemic LE [SLE]) as well as the skin (CLE). Common cutaneous subtypes of CLE are chronic CLE (CCLE) and subacute CLE (SCLE). CCLE is the only type of CLE which heals with scarring and this may affect any site in the body. The fact that inflammation in CCLE generally involves the bulge area of the follicles (where the stem cells reside) raises the possibility that damage to the stem cells may be one process leading to permanent loss of follicles. One of the most useful distinctive markers of the stem cells is cytokeratin 15 (CK15) and this has been used in some studies to demonstrate the involvement of the bulge region in the scarring process in primary cicatricial alopecia and DLE. The bulge region appears to be involved in the scarring process in CLE and other types of cicatricial alopecia as part of broader involvement of the hair follicles; it is secondarily affected by the surrounding inflammatory cell infiltrate. Expression of the stem cell marker CK15 diminished and was then absent indicating either damage to stem cells or differentiation to help in the repair process.