Baldness: Difference Engine: Shining beacons | The Economist

Difference Engine: Shining beacons

From the page: “….In men, about 5% of the free testosterone floating around their bodies is turned into DHT by an enzyme found largely in the scalp and prostate gland. DHT is a particularly potent androgen, with three times testosterone’s affinity for binding to androgen receptors. Apart from attacking follicles in the scalp, DHT also plays a leading role in the development of benign prostatic hyperplasia (enlarged prostate) and even prostate cancer itself.

That is not to say bald men are statistically more likely to get prostate cancer than non-bald men. But drugs designed originally to treat enlarged prostate glands–by inhibiting the enzyme that converts testosterone into DHT–have turned out to be useful for arresting the loss of, and even regrowing, hair on balding heads.

A synthetic anti-androgen called finasteride (marketed by Merck as “Proscar” and “Propecia”) has been approved in America for treating both enlarged prostates and male-pattern baldness. Another DHT-inhibitor called dutasteride (marketed by GlaxoSmithKline as “Avodart”) has been approved only for treating enlarged prostates. However, being at least three times more potent than finasteride, dutasteride is frequently prescribed “off label” for both baldness and prostate cancer as well.

Apart from the risk of impotence, depression and other side effects, the main problem with taking DHT-inhibitors such as finasteride and dutasteride for baldness is that their therapeutic benefits are reversed once a person stops using them. Any hair gained or maintained is lost within six months to a year. The same goes for over-the-counter baldness preparations such as minoxidil (“Rogaine”, etc), though their effect lasts only a month of two after ceasing use.

All is not lost, however. Scientists have been aware for years that stem cells can be used to grow new hair-producing follicles. People with male-pattern baldness have no shortage of stem cells in their follicle roots. Being dormant, however, the stem cells there cannot stimulate the growth of fresh hair. A race has been on to find the molecular signals that switch the follicles back into action.

As it turns out, mammalian skin–because it is constantly being regenerated–is a particularly handy tool for studying stem cells. During the body’s early development, stem cells in the skin develop along three different pathways, differentiating into hair follicles, into sebaceous glands for secreting fat to lubricate and waterproof the skin, and into the epidermis itself. How the stem cells are guided to their different destinations by molecules called transcription factors holds the key to a cure for baldness.

Last week, Valerie Horsley and her colleagues at Yale University in New Haven, Connecticut, reported that cellular signaling capable of regenerating dormant follicles comes from a transcription factor which regulates precursor cells that form the skins fatty layer beneath the epidermis. When hair dies, the thick fatty layer that contains the sebaceous glands in the scalp shrinks, and has to be thickened up before the follicles can spring back into action. Dr Horsley’s team has identified a type of stem cell–known as the adipose precursor cell–that plays a crucial part in creating new fat cells. These produce molecules called platelet-derived growth factors that are capable of switching on dormant follicles.

Basing its studies on mice incapable of producing fat cells, the Yale group injected adipose precursor cells from healthy mice into the defective ones. A four-fold increase in the number of precursor fat cells was subsequently detected in the skin surrounding the dormant follicles. Places where the precursor cells were injected also started churning out 100 times more growth factor than surrounding cells. Two weeks after the injection, 86% of the dormant follicles were sprouting hair. The question now is whether the work on mice translates into similar effects in humans.

Over the decades, your correspondent has often pondered what he might do if an effective baldness cure–as opposed to a mere temporary treatment–became available. The padding would certainly be welcome. But it would not be just passport pictures and driving licences that would need to be changed. A whole persona would have to be reinvented. That sounds like a huge hassle for anyone whose identity, for better or worse, has long since been established.

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