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Control of Hair Growth and Follicle Size by a Growth Factor Protein

Drs. Yano, Brown, and Detmar, all associated with medical institutions in Massachusetts, completed a study indicating that a certain protein may make hair follicles and therefore hair shafts larger. They compared two groups of mice, one of which they labeled wild-type and the other transgenic. The transgenic mice were bred to produce extra VEGF.

VEGF or Vascular Endothelial Growth Factor is a protein naturally produced in the body. The scientists found that the mice bred to produce extra VEGF grew fur faster and thicker than the wild-type mice. The network of capillaries supplying nutrients to the follicles of the VEGF group were also 30 to 40 % larger than those of the wild-type. 

The scientists concluded that by regulating the amount of VEGF in the skin they could influence the size of the hair follicles and the density of the hair. The results of this study were published in The Journal of Clinical Investigation (February 2001, Number 4).

Comment: Because this is the most significant research I have read in years, I have written an extended commentary. The quotations are all from the scientists' article in The Journal of Clinical Investigation.

The mantra that hair loss has nothing to do with impaired circulation to the scalp continues to be recited by most of the hair gurus. In general it's true. The large arteries in the neck and temples deliver sufficient blood flow to the scalp. The hair follicles should be well-nourished with nutrient-laden blood. Of course some scam artists with their high-voltage systems to get more blood to the scalp preach that this extra blood flow will have a beneficial effect on the follicles making them sprout terminal hair.

The research done by Yano, Brown, and Detmar also indicates that circulation in the scalp will have a beneficial effect on intact follicles. The circulation they're talking about though is of a microscopic kind, and their analysis goes right to the heart of hair biology.

These scientists are working with mice because in these creatures the hair cycles are fast and the results can be graphed rapidly. The conclusions from the study, though, can be applied, with some qualifications, to humans where a full hair cycle can take up to ten years.

If you're not familiar with the stages of the hair cycle, please click Male Pattern Baldness and read that before attempting this.

"Hair follicles undergo pronounced cyclic expansion and regression leading to rapidly changing demands for vascular support." When the follicles go from the resting stage to the growing stage there is an increased need of nutrients. The network of capillaries surrounding the follicles (see the drawing) is the delivery system. In the resting stage these capillaries are minute. In order to supply the increased demand of nutrients, especially the amino acids, to the follicles in the growing stage these capillaries must expand. By expand I mean that they must either form new vessels or increase the size of the existing ones.

The study indicates that it is mostly the enlargement of the existing capillaries--up to a fourfold enlargement--that takes place. This enlargement is called angiogenesis although angiogenesis also applies to the proliferation of new capillaries.

The question is, what causes this angiogenesis which usually takes place a short time before the follicles go into the growing stage. This is the interesting part of the story. 

The mechanism controlling the angiogenesis in the hair follicles is a protein called VEGF (Vascular Endothelial Growth Factor). This protein causes a "...pronounced vascular remodeling..." during the early part of the growth stage of the hair cycle. In fact "...cyclic hair growth is dependant on...angiogenesis to meet the increased needs of hair follicles during the anagen phase of rapid cell division."

After the long growing stage (anagen) of the hair cycle, the follicles go into a short degenerative stage (catagen) and then into a lengthy resting stage (telogen). All this is also correlated with VEGF, in this case a decrease in the production of the protein. This decrease causes the network of capillaries surrounding the follicles to shrink again.

The study as outlined in the Journal is "...the first direct evidence that promotion of angiogenesis can promote hair growth and additionally lead to hair thickness." Or put another way by the authors, "These findings demonstrate that normal follicle growth and cycling are dependant on VEGF induced angiogenesis."

The reason I think this research into VEGF and angiogenesis is important is that it gives more than a clue to the dynamics of the hair cycle. It is only during the hair cycle, especially in the transition from telogen to early anagen, when the follicles enlarge, miniaturize, or stay the same. All this seems to be mediated by VEGF and angiogenesis.

I'm sure, though, that other scientists with new findings will muddy up the waters again when they introduce new complexities. Men like Erich von Stroheim, Yul Brenner, and Telly Savalas, happy with the way they looked, never had to be concerned about VEGF, angiogenesis, and new complexities. But for the rest of us, every bit of scientific progress in hair research counts.   

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