Molecular signals that trigger hair growth have been discovered by scientists from Yale University, according to an article published in Cell. The authors say their study may eventually lead to effective treatments for baldness. They found that in laboratory mice, molecular signals from stem cells inside the skin’s fatty layer were needed to bring about hair growth.

Valerie Horsley, senior author, said:

“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.”

Stem cells still exist in the follicle roots of men with male pattern baldness, the researchers explain. However, they have lost the ability to trigger hair to re-grow. Even though scientist have known that these stem cells within the follicle need signals from somewhere within the skin to start growing hair, they were not sure exactly where the signals came from.

Horsley and team noticed that a layer of fat in the scalp shrinks when hair dies – this layer comprises most of the skin’s thickness. When hair starts to grow, adipogenesis occurs – the layer of fat expands.

For hair regeneration to occur in mice, adipose precursor cells were needed, the scientists found. Adipose precursor cells are types of stem cells involved in creating new fat cells. These cells were also found to produce PDGF (platelet derived growth factors), types of molecules needed to trigger hair growth.

The scientists are now attempting to identify what other signals the adipose precursor stem cells produce that might be important in regulating hair growth. They would like to know whether what has occurred in mice so far, also applies to human hair growth.

The authors concluded:

“These data highlight adipogenic cells as skin niche cells that positively regulate skin stem cell activity, and suggest that adipocyte lineage cells may alter epithelial stem cell function clinically.”

male pattern baldness
Picture of an example of male pattern baldness (Wikipedia Commons)

Alopecia refers to baldness, hair loss or thinning hair in any region of the body that is generally hairy. Lay people tend to use the word baldness, and generally refer to the loss of hair on the scalp. However, alopecia can be used for hair loss in any part of the body.

There are several types of alopecia, some are listed below:

  • Alopecia areata – baldness occurs in patches in any part of the body. It commonly involves patchy hair loss on the scalp, which can progress to complete baldness, and then loss of hair in other parts of the body.
  • Alopecia totalis – all the hair on the scalp is lost. It can occur rapidly, or be the progression of alopecia areata. Experts say it is the result of an autoimmune disorder.
  • Alopecia universalis – the individuals whole body loses all its hair. Generally occurs rapidly, and includes even the eyebrows and eyelashes. It is considered the most severe form of alopecia. Experts say it is caused by an autoimmune disorder.
  • Alopecia barbae – facial hair is lost. It can affect both males and females. However, only males are usually bothered by it.
  • Alopecia mucinosa (follicular mucinosis) – this is an inflammatory condition. The hair follicle as well as the sebaceous glands are affected. It can result in scarring as well as non-scarring hair loss. It generally affects the scalp, neck and face, but any part of the body could be affected. It is probably an autoimmune disease too. If treated early enough, the condition can be reversed.
  • Androgenetic alopecia (male pattern hair loss) – also referred to as male pattern baldness. The hair gradually thins, usually over a period of many years. When lay people talk about baldness, they usually refer to this type. Experts say it is most likely hereditary.
  • Adrogenetic alopecia (female pattern hair loss) – also referred to as female pattern baldness. If it does occur, it will most likely do so during the menopause. The hair on the scalp thins while facial hair becomes coarser. Unlike male pattern baldness, the female with this type of baldness will experience overall thinning of the hair on the scalp, rather than an initial receding frontal hairline. It hardly every progresses to total or near baldness.
  • Traction alopecia – hair falls out because of excessive pulling or tension on the hair shafts. It could be caused by some hairstyles, such as very tight ponytails, braids or pigtails. In some cases, if the alopecia is prolonged, the lost hair might not be restored.
  • Anagen affluvium – hair is lost after radiotherapy or chemotherapy for cancer treatment. Fortunately, in most cases the hair grows back some months later. It can also be caused by some other medications, as well as compulsive hair pulling.

Written by Christian Nordqvist