Receptors in Trichology: Hot Spots for Hair Regeneration



n 1913, Paul Ehrlich, while introducing the concept of receptors said, “substances are active only in solution and substances do not act unless bound.” It is an almost prophetic statement made nearly half a century before the advent of the receptor era in clinical medicine. Receptors are molecular structures within a cell or on its surface to which substances such as hormones, drugs, and cellular or immunological components selectively bind, causing a change in the cellular activity. They play an important role in health and disease. Almost all receptors have been cloned in recent times and are finding applications in clinical practice – “from benchside to bedside,” as some would call this. Receptors play an important role in trichology. Vitamin D3‑resistant rickets is associated with severe alopecia in childhood. At the molecular level, it is known that vitamin D3 is an important regulator of keratinocyte growth, the action being mediated through vitamin D3 receptor (VDR) in the nucleus. VDR is expressed in the outer root sheath of keratinocytes and in the dermal papilla of the hair follicle. In vitamin D3‑dependent rickets type II, which is an autosomal recessive disorder, it is suggested that VDR is absent or defective and that alopecia is an expression of impaired end‑organ responsiveness. Since in these patients Access this article online Quick Response Code Website:

DOI: 10.4103/0974-7753.125596

International Journal of Trichology / Jul-Sep 2013 / Vol-5 / Issue-3

hairs are present at birth but lost later, it is possible that VDR plays a role in normal hair cycle rather than in primary hair growth. Graying of hair is usually a manifestation of aging and results from reduction in melanocyte function. Melanocytes are present both in the bulge area and the hair matrix of the hair bulb. A few of the melanocytes at the bulge area may possess properties of regeneration, thus behaving like stem cells. At the molecular level, functional melanocytes respond to a‑melanocyte stimulating hor mone (a‑MSH) or adrenocorticotropic hormone (ACTH) through melanocortin receptor (MCR) to stimulate melanin production. This receptor expresses the tyrosinase gene, regulates melanocyte proliferation, and increases dendricity. Interestingly, functionally active VDR is also expressed in melanocytes. In addition, numerous other cell surfaces as well as nuclear receptors have been identified in melanocytes. A better understanding of these receptors will not only explain graying at the molecular level and hopefully arrest its progression, but also present targets for the treatment of the dreaded malignant melanoma. Receptors at the molecular level, like stem cells at the cellular level, are taking the center stage in human therapeutics.

Patrick Yesudian President, The Hair Research Society of India, No. 10, Ritherdon Avenue, Vepery, Chennai ‑ 600 007, India. E‑mail: [email protected] How to cite this article: Yesudian P. Receptors in trichology: Hot spots for hair regeneration. Int J Trichol 2013;5:109.


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Receptors in trichology: hot spots for hair regeneration.

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