The ability of fingernails to grow back, unlike other body parts seems to be the result of the presence of a resident stem cells population.
Researchers at the University of Southern California (USC), led by Krzysztof Kobielak has identified a new stem population in nails that can either self-renew or differentiate into other distinct cell types.
Identifying these cells was no small chore, and Kobielak used an ingenious new technique for attaching fluorescent dyes and other tags to mouse nail cells. while many cells in the nail divided and spread throughout the nail, another small population stayed at the base of the nail and divided slowly or not at all.
Kobielak and his team showed that these slow-dividing cells normally contribute to the growth of her nails and nearby skin. However, if the nail undergoes some kind of injury or physical insult, a signaling protein called bone morphogen protein or BMP signals to the nail bed stem cells to switch to exclusively repairing the nail. Thus this nail bed stem cell population has the flexibility to perform dual roles in the finger tips.
The members of the Kobielak laboratory are also interested in other types of signals and what they might do to these nail bed stem cells. For example, could they induce them to differentiate into additional cell types besides skin and nail? Could they aid in amputation repair and the repair of severe skin injuries?
Kobielak said: “That was very surprising discovery [sic], since the dual characteristics of these nail stem cells to regenerate both the nail and the skin under certain physiological conditions is quite unique and different from other skin stem cells, such as those of the hair follicle or sweat gland.”