“Experts say they have discovered what they believe is the cause of male pattern baldness,” according to BBC News. The condition is reportedly the result of a “manufacturing defect”, which causes new hairs to be microscopic compared to normal hair.
The US research behind this news investigated the stem cells that make new hair. The researchers examined scalp samples from men undergoing hair transplants. When the researchers compared hair follicles in bald and hair-covered areas of the scalp, they found that bald areas of the scalp had a normal number of stem cells but lacked the “progenitor cells” they normally mature into. These progenitor cells are responsible for producing new hair.
The fact that stem cells are present in bald areas means it may be theoretically possible to “reactivate” them in the future. However, whether this is possible is likely to be the subject of much further research. While the current research furthers our understanding of what may contribute to the development of male-pattern baldness, there is still a way to go before it leads to new treatments or prevention methods.
The study was carried out by researchers from the University of Pennsylvania and Boston University in the US and the National Cheng Kung University, Taiwan. Funding was provided by the US National Cancer Institute, US National Institute of Health, Pennsylvania Department of Health, Edwin and Fannie Gray Hall Center for Human Appearance at the University of Pennsylvania Medical Center, American Skin Association, Dermatology Foundation and L’Oréal. The study was published in the peer-reviewed Journal of Clinical Investigation.
BBC News clearly reflected the findings of this research.
This laboratory research examined samples from sections of bald and non-bald scalp in men with male-pattern baldness. Researchers compared the presence of hair follicle stem cells and progenitor cells in these two types of scalp. Both cell types are involved in the formation and growth of hairs. The researchers explained that a portion of the hair follicle known as “the bulge” contains stem cells that divide during the onset of each new hair growth cycle. These stem cells can mature into the progenitor cells, which go on to produce the new hair shaft.
Previous human studies examining the bulge have found that the stem cells make two important compounds: the protein KRT15 and the cell surface marker CD200. The cells immediately below the bulge, in the outer root sheath of the hair follicle, make another marker called CD34. The cells in the outer root sheath are considered to be a population of progenitor cells derived from the bulge. By examining the concentration of these substances, the researchers believed they could assess populations of stem and progenitor cells in the scalp.
The study used human scalp specimens obtained anonymously during hair transplantation in men with male-pattern baldness. As part of the transplantation procedure, several hair-covered specimens are taken from the back part of the skull (the occiput) to produce grafts of different sizes. During the procedures, several of these specimens are usually considered unsuitable for use and so are discarded. In this study, these samples were salvaged and used as specimens of non-bald scalp. Specimens of bald scalp came from the small, cylindrical sections removed from the bald frontal scalp to give room for the new hair-covered scalp inserts.
In the laboratory, levels of KRT15, CD200 and CD34 were analysed to look for any potential differences in the stem and progenitor cell levels in bald and non-bald scalp sections from men with male-pattern baldness.
Levels of KRT15 were similar in bald and non-bald scalp samples, meaning the stem cell population was maintained in bald scalp. However, there was less evidence of active progenitor cells in the bald scalp, according to levels of CD200 and CD34. In normal scalp, cells expressing these markers were positioned close to the bulge area of the follicle, but were larger and more proliferative than their parent stem cells. These progenitor cells are responsible for new hair growth.
These findings were supported by studies of mouse skin, where the researchers observed that cells expressing CD200 are able to regenerate hair follicles.
The researchers say their findings suggest that a lack of stem cells does not contribute to male-pattern baldness, but rather there is a problem with the conversion of stem cells to progenitor cells. This loss of progenitor cells may play a role in the development of baldness, they add.
This laboratory study examined stem cells in bald and non-bald areas of scalp. It found that depletion in levels of progenitor cells, which normally go on to produce the hair follicle, may lead to the loss of hair.
The fact that follicle stem cells, which perform the initial stages of hair production, are preserved in bald areas gives hope to the possibility of finding ways to “reactivate” them in the future, restoring hair growth. Whether this is possible is likely to be the subject of much further research.
The current research adds to our knowledge of what may contribute to the development of male-pattern baldness, although it has not shed much light on measures for preventing or treating the condition. Also, the findings cannot be assumed to explain the causes of other forms of hair loss, which may involve different cellular processes.