Hair Growth – Controlled by Many Factors

The fact that we can even grow hair at all is quite amazing. Hair growth results from having an intact hair follicle that is comprised of many components: the dermal papillae or base of the hair follicle, the bulge where hair stem cells are located and the supporting specialized tissues surrounding each hair follicle base. Even in the presence of these parts, hair growth is regulated by many hormones, growth factors and cytokines – small proteins that can stimulate or inhibit hair growth.

The hair follicle stem cells in the hair sheath bulge give rise to new hair matrix cells. The sustained growth of the matrix cells and subsequent differentiation into hair producing epithelial cells are under the influence of cytokines and growth factors, primarily produced by the dermal papilla – at the very base of the hair follicle. The dermal papilla production of cytokines and growth factors is controlled by the bulge stem cells, hormones and other growth factors. Many of the latter are contained in platelet rich plasma.

Growth factors in PRP that positively affect hair growth include the following:

*Platelet-Derived Growth Factor (PDGF)
*Basic Fibroblast Growth Factor (bFGF)
*Insulin Growth Factor 1 (IGF-1)
*Vascular Endothelial Growth Factor (VEGF)
*Keratinocyte Growth Factor (KGF)

Some of these growth factors promote the production of a specialized protein – stromelysin, a zinc based growth factor – which accelerates dermal papillae cell growth. Zinc supplementation with other supplements may help in this process.

Growth factors and cytokines that have a negative effect on hair growth include:

*Transforming Growth Factor Beta (TGF-b)
*Epidermal Growth Factor (EGF)
*Interleukin 1 Alpha
*Fibroblast Growth Factor (FGF)

PRP can be injected into the scalp to stimulate hair follicle by release growth factors and stimulating stem cells. Activation of platelet rich plasma with thrombin, after injection into the scalp, helps to reduce the negative effects of TGF-b and EGF. Interestingly, human growth hormone (HGH) has no direct influence on hair growth either positive or negative.

Androgens are various hormones produced by the adrenal gland or from testosterone, can have varying effects on different hair growth, depending on the type of hair. Certain hair, such as that on the eyelashes have no effect from these androgens. Hair on the sides and back of the the head are only weakly affected by androgens. There is a strong effect of androgens on hair on top of the head. Of these, dihydrotestosterone (DHT) has the strongest influence on scalp hair. It binds to receptors on the dermal papilla cells. Through a complex interaction, this androgen-receptor complex stimulates production of cytokines which control the growth of hair matrix cells. These same cytokines which have a positive stimulation effect on the hair follicles on the sides and back of the head yet inhibit hair growth over the top of the scalp. The latter results in hair follicle atrophy, hair miniaturization and eventual hair loss.

Vitamins may have an effect on hair growth as well. Retinoic acid (derived from vitamin A) and vitamin B6 (pyridoxine) can have a negative effect on factors involved in hair growth. Biotin (vitamin B7) on the other hand can has a positive effect on hair and nail growth. It is commonly used as a supplement to enhance or improve hair growth.

Medications can have a mild to dramatic effect on hair thinning and hair loss. Chemotherapy agents used for cancer can frequently cause hair loss. ACE inhibitors, beta-blockers, Depakote (valproic acid) and lithium are some examples of commonly used drugs that have a negative effect on hair growth. Conversely drugs such as minoxidil, finasteride and spironolactone may help in promoting hair growth. While minoxidil can be used by anyone, finasteride should be used only in males and spironolactone by women.

From this information, it is obvious that there are many complex interactions between cells, growth factors, cytokines, hormones and other mechanisms that can have positive or negative effects on hair growth. This has given researchers the opportunity to investigate many avenues to promote wanted hair growth. Research continues to develop safe and effective methods for sustaining hair growth and generating new hair growth. Biopsies in individuals with advance hair loss show that scalp hair follicle density is the same in bald regions as it is in hair growth regions. Finding the mechanism to turn these dormant hair follicles “on” is ongoing. At this time, platelet rich plasma appears to be very safe and effective.

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About Dan Kassicieh, D.O.

Dr. Kassicieh is a Board-Certified Neurologist and is the medical director of the Florida Headache and Movement Disorder Center. He has been practicing in Sarasota for over 23 years. Dr. Kassicieh is a Fellow of the American Academy of Neurology and the American College of Neuro-psychiatrists. Both of these honors were awarded to him on the basis of his extensive research experience, medical publications and continued support of patients and their families who are affected with neurological disorders. Dr. Kassicieh is a sought-after public speaker and is frequently a presenter both within the medical community and in the public forum. He has appeared regularly on local television and is considered an expert in a number of areas within his specialty. Dr. Kassicieh’s primary medical interests are in the treatment of headache, neck and back pain. He specializes in non-surgical neuro-orthopedics. The goal in treatment of patients is to restore them to a pain free status without the use of narcotics or surgery. To this end, he has had training in Platelet Rich Plasma therapy. From his successes with this for neuro-orthopedic problems, it was only natural that he use platelet rich plasma to help patients with hair loss. Giving each patient the best quality of life is our goal at Sarasota Neurology.

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