Using cell samples from men undergoing hair transplant, the researchers compared follicles from bald scalp and non-bald scalp, and found that bald areas had the same number of stem cells as normal scalp in the same person.
However, they did find that another, more mature cell type called a progenitor cell was markedly depleted in the follicles of bald scalp.
The researchers surmised that balding may arise from a problem with stem-cell activation rather than the numbers of stem cells in follicles. In male pattern balding, hair follicles actually shrink; they don`t disappear. The hairs are essentially microscopic on the bald part of the scalp compared to other spots.
"We asked: `Are stem cells depleted in bald scalp?` We were surprised to find the number of stem cells was the same in the bald part of the scalp compared with other places, but did find a difference in the abundance of a specific type of cell, thought to be a progenitor cell.