Biology is all about communication. Molecular signals travel within and between cells, passing on information that keeps your body from from developing diseases, chemical imbalances, fatal maladies . . . and baldness.
It turns out that male pattern baldness occurs when the stem cells responsible for triggering hair regeneration simply stop receiving certain signals from within your scalp that tell hair to grow. Now, a team of scientists think they may have found the source of these missing signals — a discovery that may herald new treatments for baldness.
Reach up and touch your scalp. If you give it a little pinch, you'll notice that between the outer layer of your skin and your skull, your scalp has got a little thickness to it. Well the bulk of that thickness is fat.
A team of researchers at Yale University led by Dr. Valerie Horsley noticed that when hair dies off, the fat cells in that layer shrink away, causing the thickness of your scalp to decrease. When hair growth begins, however, the layer expands in a process known as adipogenesis, wherein stem cell precursors to fat cells (sometimes called preadipocytes, adipose precursor cells, or lineage cells) differentiate into full-blown fat cells.
The connection between hair health and the production of fat cells suggested to the researchers that the process of adipogenesis may point to the so-called "niche" of the stem cells found in hair follicles. (A tissue niche refers to the microenvironment in which stem cells are found and their activity regulated.)
You can think of a tissue niche as an arena in which signals directing stem cell activity are propagated; to examine what role fat cells and their precursors might play in the process of hair regeneration, Horsely and her colleagues examined mice with known defects in their adipogenesis cycles. The researchers describe their findings, which are published in the latest issue of Cell:
Functional analysis of adipocyte lineage cells in mice with defects in adipogenesis and in transplantation experiments revealed that immature adipocyte cells are necessary and sufficient to drive follicular stem cell activation [and] we implicate PDGF signals produced by immature intradermal adipocyte lineage cells in controlling hair regeneration. These data define active roles for intradermal adipocytes in the regulation of the skin tissue microenvironment.
In other words, the researchers found that the stem cell precursors to the fat cells found in the layer of fat beneath your skin were required for hair regeneration. Moreover, they found that these cells were producing a growth factor known called PDGF, which they also identify as necessary for hair growth.
So, on the topic of baldness treatment: will Horsley and her colleagues be able to make it so?
"If we can get these fat cells in the skin to talk to the dormant stem cells at the base of hair follicles, we might be able to get hair to grow again," she said.