Exchange between Cells that Control Hair Growth

Photo: Hair follicles

Hair follicles cannot grow
(bottom) when dermal papilla
lacks the receptor that binds
BMP6; © Rockefeller University

"Scientists don't know how dermal papilla cells are programmed to provide the instructive signals to stem cells, but now we know that BMP signals play a crucial role," says Michael Rendl, who conducted this work while he was a postdoc in Elaine Fuchs's Laboratory of Mammalian Cell Biology and Development. Fuchs conducted the study with Rendl, who found that BMP6, a member of the BMP family of proteins, orchestrates dermal papilla's signature genes to turn on and off, thereby giving these skin cells their unique collection of proteins and features.

The researchers developed a clever strategy to delete several genes in vitro, ones that encode for the receptor onto which several BMPs bind. They then grafted these genetically engineered dermal papilla cells onto the backs of bald mice to see if these mice would grow hair. When dermal papilla cells lacked this receptor, their signature proteins were not expressed and the key signaling that occurs between epithelial stem cells and dermal papilla was impaired. Without this exchange, the hair follicles did not grow or make hair.

Nearly all of the signature proteins that Rendl and Fuchs tested in dermal papilla cells decreased when they deleted the BMP receptor. The exception: BMP6 itself. This increase in BMP6 expression levels suggests that BMP6 is necessary for both locking in dermal papilla's molecular identity as well as maintaining the crosstalk that allows stem cells to receive hair-inducing signals, but it itself is not the signal that stem cells await. This finding also provides clues to the type of signals that follicle stem cells may send to dermal papilla.

Fuchs speculates that "this complex circuitry in BMP signaling may set the foundations for a BMP regulatory clock that drives the hair cycle. If so, we may be one step closer to unlocking nature's secrets to hair growth."

MEDICA.de; Source: Rockefeller University