Characterization of Ovine Dermal Papilla Cell Aggregation.

CONTEXT: The dermal papilla (DP) is a condensation of mesenchymal cells at the proximal end of the hair follicle, which determines hair shaft size and regulates matrix cell proliferation and differentiation. DP cells have the ability to regenerate new hair follicles. These cells tend to aggregate both in vitro and in vivo. This tendency is associated with the ability of papilla cells to induce hair growth. However, human papilla cells lose their hair-inducing activity in later passage number. Ovine DP cells are different from human DP cells since they do not lose their aggregative behavior or hair-inducing activity in culture. Nonetheless, our understanding of ovine DP cells is still limited. AIM: The aim of this study was to observe the expression of established DP markers in ovine cells and their association with aggregation. SUBJECTS AND METHODS: Ovine DP cells from three different sheep were compared. Histochemistry, immunoflourescence, and polymerase chain reaction experiments were done to analyze the DP markers. RESULTS: We found that ovine DP aggregates expressed all the 16 markers evaluated, including alkaline phosphatase and versican. Expression of the versican V0 and V3 isoforms, neural cell adhesion molecule, and corin was increased significantly with aggregation, while hey-1 expression was significantly decreased. CONCLUSIONS: Overall, the stable expression of numerous markers suggests that aggregating ovine DP cells have a similar phenotype to papillae in vivo. The stability of their molecular phenotype is consistent with their robust aggregative behavior and retained follicle-inducing activity after prolonged culture. Their phenotypic stability in culture contrasts with DP cells from other species, and suggests that a better understanding of ovine DP cells might provide opportunities to improve the hair-inducing activity and therapeutic potential of human cells.

The Effect of Ovine Secreted Soluble Factors on Human Dermal Papilla Cell Aggregation.

CONTEXT: In androgenetic alopecia, follicular miniaturization and dynamic changes to the hair cycle produce patterned baldness. The most effective treatment for baldness is hair transplantation surgery. The major limitation to hair transplantation is the availability of donor hair from the relatively unaffected occipital scalp. Hair induction with in vitro expansion of donor follicle populations has the potential to overcome this. The major obstacle to this is that in vitro expansion of human dermal papilla cell (DPC) colonies is associated with irreversible loss of aggregative behavior and hair follicle-inductive potential. In contrast, cultured ovine DPCs maintain these properties after extensive proliferation. AIMS: To determine whether aggregating ovine DPC secrete factors that enhance the aggregative behavior or inductive potential of human DPC. SUBJECTS AND METHODS: Fluorescently-labelled ovine DPC were mixed in culture with human DPC at passage number seven-nine, which had lost their aggregative behavior. The effects of different culture substrates and medium compositions on aggregative behavior were determined. Ovine and human papilla cells were co-cultured, separated by a permeable membrane to determine whether the ovine cells secrete soluble factors that affect human papilla cells. RESULTS: In direct co-culture experiments, well-formed aggregates were produced by 90:10 human:ovine and 50:50 human:ovine DPC mixtures. In contrast, unmixed human DPC remained in a monolayer state after 18 days. Both human and ovine DPC had a higher tendency to aggregate in medium containing 20% (v/v) lamb serum (LS) compared to 10% (v/v) fetal calf serum (FCS). In co-culture experiments separated with permeable membrane, the human DPC aggregates were bigger and more rapidly formed with the addition of ovine secreted soluble factors. CONCLUSIONS: Soluble factors secreted by ovine DPC and present in LS increase the aggregative behavior of human DPC. These molecules might improve follicle inductiveness of human DPCs for the purpose of hair replacement therapy.