The dermal papilla: an instructive niche for epithelial stem ...

[waynakyo]

[h=1][FONT=Verdana, Arial, Tahoma, Calibri, Geneva, sans-serif]The dermal papilla: an instructive niche for epithelial stem and progenitor cells in development and regeneration of the hair follicle.[/FONT][/h][FONT=Verdana, Arial, Tahoma, Calibri, Geneva, sans-serif]Morgan BA.[/FONT]
[h=3][FONT=Verdana, Arial, Tahoma, Calibri, Geneva, sans-serif]Author information[/FONT][/h]

[h=3][FONT=Verdana, Arial, Tahoma, Calibri, Geneva, sans-serif]Abstract[/FONT][/h][FONT=Verdana, Arial, Tahoma, Calibri, Geneva, sans-serif]The dermal papilla (DP) of the hair follicle is both a chemical and physical niche for epithelial progenitor cells that regenerate the cycling portion of the hair follicle and generate the hair shaft. Here, we review experiments that revealed the importance of the DP in regulating the characteristics of the hair shaft and frequency of hair follicle regeneration. More recent work showed that the size of this niche is dynamic and actively regulated and reduction in DP cell number per follicleis sufficient to cause hair thinning and loss. The formation of the DP during follicle neogenesis provides a context to contemplate the mechanisms that maintain DP size and the potential to exploit these processes for hair preservation or restoration.[/FONT]

 

[IDW2BB]

http://www.ncbi.nlm.nih.gov/pmc/articles/PMC4148374/#!po=59.3750

Previous studies have established that chronic exposure to solar radiation leads to skin damage (1,2). Ultraviolet (UV) radiation, which can be categorized into UVA, UVB and UVC according to wavelength, has the potential to cause DNA damage, leading to sunburn and skin cancer (3). UVC radiation has the shortest wavelength and thus emits the highest energy levels (4), but the majority of UVC from sunlight is absorbed by the atmosphere, in particular the ozone layer, so is not a threat to health. UVA and UVB, however, reach the skin by penetrating the atmosphere (5), and in hair follicles, androgenetic alopecia is a result of UV-induced photo-aggravated dermatitis (6). Additionally, UV represses growth and cycling of hair follicles and follicular melanogenesis in vitro (7).

 

[hellouser]

This would make you believe that all men in Africa would be bald by their 20s.

 

[IDW2BB]

This would make you believe that all men in Africa would be bald by their 20s.

At least the white dudes with a genetic predisposition.

 

[benjt]

It would also mean that the Scandinavians have less Androgenetic Alopecia/male pattern baldness than the rest of Europe, but they don't.

Edit: Oh, wait. In the distribution of hair loss all over Europe, the mediterraneans are indeed the ones with the most instances of far-progressed Androgenetic Alopecia/male pattern baldness. However, I think that UV light is only a minor contributing factor, because the difference is not very big - and as stated, the northern Scandinavians should be pretty much free from Androgenetic Alopecia/male pattern baldness if UV light was the determining factor and not just a minor accelerator.

Edit2: I can't really find any statements or data in the body of the study which would support the claim that "in hair follicles, androgenetic alopecia is a result of UV-induced photo-aggravated dermatitis" which is based on another paper they cite. Their own study, however, does not support this at all. It only illuminates the connection between UV radiation and increased apoptosis.

Edit3: Indeed, the abstract of the paper they cite doesn't even claim that it is the case. It only argues to propose that this could be the case. Don't have the full paper, so cant confirm - but from the abstract it doesnt seem as though the paper actually claims that to be the truth.