The dermis contains a wide variety of fibroblast phenotypes. Of particular interest are the progenitor-rich populations than can be isolated from the dermal papilla.
These progenitors demonstrate a very different gene-expression profile than typical fibroblasts, and are thought to be responsible for a variety of functions including hair follicle induction and maintenance of the dermal-epidermal junction, and thus the basal keratinocyte layer.
Dermal progenitors behave differently in vitro to regular fibroblast populations. They are also ideally suited to progenitor cell assays such as colony formation, which are able to detect the effect of active ingredients on dermal progenitors, and their ability to form spheres.