Journal of Stem Cell Research & Therapy

THE STRUCTURE OF THE HAIR FOLLICLE AND ITS CYCLE

Abo Shama^{* 1}Department of Dermatology, Columbia University, New York, NY, USA
^*Correspondence: Abo Shama, Department of Dermatology, Columbia University, New York, NY, USA, Email:

Received: 05-Jun-2021 Published: 28-Jun-2021, DOI: 10.35248/2157-7633.21.11.e494

Introduction

The hair follicle is comprised of an outer root sheath (ORS) that is a part of the epidermis, an inner root sheath (IRS), and a hair shaft. Hair follicles have three distinct phases in the development and breakdown of hairs. The anagen phase is a time of activity and hair growth, while catagen is a time of apoptosis and hair destruction. The third phase is telogen, a period of rest. Undifferentiated stem cells consistently develop into hair fibers, ensuring normal hair growth and regeneration. Over time and with hormone malfunction and genetic mutations, these normally functioning follicles begin to produce thinner, shorter hairs, ultimately ending in alopecia. Alopecia is the blanket term for hair loss. This term can refer to the autoimmune disease alopecia areata, in which small, round sections of the scalp become bald, as well as the more common hormone-driven condition, androgenic alopecia. This androgendependent baldness is also referred to as male pattern baldness. Women are also affected, although not as frequently or as dramatically as men. There has been significantly more research conducted on male pattern baldness, but an increased incidence in female hair loss has triggered an increase in its study. In alopecia areata, small areas are typically affected and may even regrow over time. The less common but more dramatic alopecia totalis and alopecia universalis result in total loss of scalp hair or hair loss over the entire body, respectively. According to the National Institutes of Health, there are no known cures for these autoimmune diseases or approved drugs for their treatment. Some sufferers will try corticosteroids or topical preparations, but due to the fact that additional hair loss can happen at any time, many of these efforts, even if successful, are temporary and largely in vain. Although many people with these autoimmune diseases do seek surgical treatments for correction of hair loss, the typical patients considering hair restoration intervention therapies are men and women fighting androgenic alopeciaUntil recently, the most common approach to correcting androgenic alopecia was the surgical technique involving the harvesting of scalp tissue containing hair producing follicles. Follicular Unit Extraction (FUE) has become the gold standard for surgical repair. This method employs extracting one to four hair follicles at a time using 1mm or less harvesting tools, allowing for a more natural result. FUE replaces older strip methods. Newer surgical techniques are repairing much of these older missteps, yet the process is still arduous There are two main types of stem cells that can be used for a variety of medical interventions: embryonic stem cells (ESC) and adult mesenchymal stem cells (MSC). There is great promise in using ESC, as they are capable of differentiating into any type of cell in the body. This could lead to cures for diseases and other highly beneficial outcomes. Regardless of their medical potential, there are myriad ethical and regulatory hurdles surrounding the use of embryonic stem cells, making the option of using MSC attractive. Below the hair follicle is a pocket of specialized mesenchymal cells, called the dermal papilla (DP). These DP are essential to follicle formation. When DP are dissected and combined with hair follicle fragments containing bulge cells, they can reconstitute a viable hair follicle. The hair follicle bulge is an excellent source of pluripotent adult stem cells.Bulge stem cells have demonstrated the ability to be multipotent, a capability that can lead to the regeneration of sebaceous glands, epidermis, and hair follicles. Because of the copious quantity of hair follicles in human skin, each containing stem cells, the skin provides a massive and easily accessible storehouse of MSC and DP in the body. In addition to the follicular bulge, MSC can be harvested from a variety of other sources, primarily bone marrow and adipose tissue. Harvesting adult stem cells from bone marrow typically requires drilling into the bone, making it a more dramatic and potentially painful procedure. Adipose tissue removal can be achieved using a typical liposuction technique. The White Adipose Tissue (WAT) resides slightly above the subcutaneous adipose layer and appears to be inextricably connected to hair follicle cycling and health. The mature fat cells are a rich source of epidermal growth factors that play a key role in slowing the follicle from entering the catagen stage, therefore lengthening the anagen stage. These fat cells also provide copious long chain free fatty acids that are known to influence many metabolic reactions, potentially that of the skin and hair