Connective Tissue Sheath of Hair Follicle Is a Major Source of Dermal Type I Procollagen in Human Scalp

In the 2012 study, researchers found that the connective tissue sheath (CTS) of hair follicles (HFs) is a significant source of type I procollagen in the human scalp. The study demonstrated that type I procollagen expression was higher in CTS than in the interfollicular dermis (IFD) and that CTS cells were the primary producers of this collagen type, rather than fibroblasts in other dermal layers. Western blot analysis supported these findings, showing increased levels of type I procollagen and decreased levels of matrix metalloproteinase (MMP)-1 in CTS compared to other dermal regions. The expression of type I procollagen in CTS also varied with the hair cycle and was upregulated following topical application of all-trans-retinoic acid (tRA). These results indicate that the CTS of HFs is crucial for dermal matrix maintenance and that the regulation of dermal collagen in human skin is complex, with a significant contribution from the CTS of HFs. The exact number of human scalp samples used in the study was not mentioned in the summary provided.