Phenotypic Modulation of Human Hair Matrix Cells by Environmental Influence In Vitro and In Vivo

The study investigated the phenotypic modulation of human hair matrix cells, or trichocytes, by environmental influences both in vitro and in vivo. Trichocytes were isolated from human scalp hair follicles and cultured with human dermal fibroblasts (HDF) or dermal papilla cells (DPC). The study found that trichocytes could differentiate into stratified epithelia similar to the epidermis when grown with HDF, but this epidermal differentiation was largely prevented when DPC were used instead. Transplantation onto nude mice showed complete epidermal differentiation, with organized tissue and expression of specific keratins and basement membrane components. The presence of HDF was crucial for the development of large spheroidal structures with epidermal markers, while DPC co-culture suppressed epidermal keratinization. The findings demonstrated that trichocytes have inherent differentiation potential influenced significantly by external factors, particularly mesenchymal cell interactions.