Hair and feather follicle pattern formation in natural and artificial skin

Development of embryonic hair and feather follicles are phenomenona which require extensive signalling interactions between cells. To understand these interactions better the study of the generation of placode patterns in embryonic skin was approached from three different perspectives. The biological approach involved the study of in situ hybridized skin samples from mouse and chicken. The mathematical approach involved simulations of a reaction-diffusion model. Finally, an engineering approach was taken involving attempts to create artificial skin in vitro with artificial placode patterns using fetal cells derived from embryonic skin. The reaction-diffusion based modelling included investigations of the effects of imposing boundary conditions such as a mammary gland in the field, as in the case of mouse embryos, and observing its effect on the simulated patterns. In vitro patterning of placodes was performed using ultrasound and dielectrophoresis as the micromanipulation technique. The ultrasound set-up formed arrays of equidistant dots of embryonic dermal fibroblasts mimicking patterns of feather buds and hair follicles in embryonic skin. Dielectrophoresis allowed a much wider range of artificial patterns to be formed, with control over cell aggregate size, shape and height. Artificially patterned dermis could be reconstituted with the epidermis, and placode formation observed thereafter.