I thought I would add a new photo to my record of change see below:
What is now clear to me is that there are three key dimensions relating to hair these are:
a) Where hair grows
b) Whether it is pigmented or not
c) Whether it is strong or weak.
The first two of these are dominated by epigenetic factors. My experience is that by increasing HDAC inhibition it is possible to grow hair in places where it would not otherwise grow.
Whether hair is pigmented or not is strongly affected by the levels of acetyl-CoA in the cells which form the hair follicle.
Whether the hair is strong or weak is dominated by mitochondrial efficiency. Men with pattern baldness (such as myself) find that their mitochondria in their hair follicles are affected by the Androgen Receptor causing some form of damage (probably oxidative) to the mitochondria in response to the stimulus of androgens.
Hence if you change these factors it becomes possible to get changes in the phenotype. What I have found is that by increasing levels of acetyl-CoA when a hair follicle starts in the anagen phase it produces a pigmented hair whereas with a lower level of acetyl-CoA it would produce an unpigmented hair.
If you take a hair follicle that was previously miniaturised as a consequence of mitochondrial damage and stimulate it to produce a hair (through any of the three approaches, acetyl-CoA, HDACi or mitochondrial improvements) first it is likely to produce a vellus hair. This is a really weak unpigmented hair. It results in the form of fuzz that @desertshores referred to. If you then improve the mitochondria this can turn into a terminal hair which is then a really fine pigmented hair. It is then possible, but hard, for this hair to become stronger. It is, however, likely to remain quite fine. However, when the hair follicle recycles at a later stage it may become stronger.
What is interesting is that is is rare that unpigmented hair will become pigmented (unless it is vellus hair turning terminal), but a recycling white follicle can produce pigmented hair.
I use a USB macro camera to monitor hair follicles and in this photo you can see different types of hair (vellus, terminal (fine), and full strength hairs) that have grown on my bald patch in recent times.
Because the camera is very close to the hairs the depth of focus is very small.
Obviously Rapamycin is one of the tools for improving mitochondrial efficiency.
I like hair as a tool for monitoring cellular development as it is relatively easy to see. Using the macro camera it is possible to monitor things like pore size, but when it comes to internal organs we are more reliant on biomarkers and the like.
This also carries forward to body hair.
