Renewal of Hair Follicles from Adult Multipotent Stem Cells

Renewal of Hair Follicles from Adult Multipotent Stem Cells

Stem cells able to reconstitute the skin, as well as hair follicles, were identified for the first time in an adult mammal by a French team of researchers. "Starting from a small group of about 500 stem cell stocks, we grew a piece of skin with hair follicles and sebaceous glands for the first time," said Dr Yann Barrandon, a cell specialist at the National Institute for Science and Medical Research and Paris's elite Ecole Normale Supérieure.

Stem cells are premature cells that develop into various organs. The most spectacular are found in embryos at their very earliest days of development. Embryo stem cells can grow into almost any part of the body, a finding that raises hopes they can eventually be "programmed" into growing replacement limbs or organs in a laboratory. This work, "provides the first direct proof of the existence of these cells and their capacities to reproduce skin", said Yann Barrandon the leader of the research team. These results, so far only obtained using mice, open significant prospects in dermatology to replace the skin in badly burned persons or to combat skin cancer, and also represent a new hope for bald people.

Humans have approximately five hair follicles per square centimeter of skin, against 50 for the mouse. These stem cell stocks, located close to the root of the hair, are able to give rise to all the lines of cells necessary to reconstitute the skin epidermis, sebaceous glands, and the hair follicles. These invaluable cells are mainly located in the hair follicle structure. The follicles represent "reseviors" of cell stocks of the skin. In humans as in rats, each one of these follicules would contain some 1500 stem cells. The cell stocks can migrate in different directions, to the bottom (towards the root of the hair) or the top of the follicle. According to the path followed, the cells specialize in the manufacture of hair follicles, secaceous glands or the keratinocyte cells of the skin.

Researchers hope to be able to find the molecules that guide these cells to become one of the three different structures (hair, sebaceous gland or skin). There are several potential applications for this research including potential new therapies for pattern baldness, by supporting the growth of the hair, or to solve an excess of hair growth (hypertrichosis) by the selective destruction of hair follicle stem cells. "Half of humanity wants to have more hair on the head and the other less hair on the legs", summarizes Dr Ariane Rochat, joint author of this 5 year long research project.

The research may also be useful for developing skin grafts containing hair and sebaceous glands for badly burned persons, explains Ariane Rochat. This research "could also contribute to the understanidng of cutaneous cancers and the recent increase in numbers affected, as 700000 cases were counted this year in the United States alone", said Yann Barrandon. The Parisian team had already isolated from the stem cell stocks of human skin, published in Cell medical journal in 1994, but were unable to show the potential of the cells to reconstitute skin. Thus the next stage is, "to make the same thing with human stem cells".