Hair Therapy & Transplantation
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Clinical Significance of Sebaceous Glands: Physiology and Changes in Sebum Production

Ensieh Maleki^{* *}Correspondence: Ensieh Maleki, Department of Histology and Dermatology, Mazandaran University of Medical Sciences, Sari, Iran, Email:

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Description

Sebaceous glands are microscopic exocrine glands in the skin that secrete an oily or waxy matter, called sebum, which lubricates and waterproofs the skin and hair of mammals. These glands are found throughout the body except on the palms of the hands and the soles of the feet. Their distribution is dense on the face and scalp, areas where sebum production is most noticeable. Understanding sebaceous glands is important due to their significant role in maintaining skin health and their involvement in various dermatological conditions.

Anatomy and physiology of sebaceous glands

Sebaceous glands are typically located in the dermis layer of the skin, connected to hair follicles through short ducts. They are holocrine glands, meaning they release their secretion by rupturing, which leads to the release of the entire cell's contents. Each gland consists of multiple lobes filled with sebocytes, which are the cells that produce sebum.

Sebocyte differentiation and function: Sebocytes originate from undifferentiated cells located in the periphery of the sebaceous glands. As these cells mature, they move toward the gland's central duct, accumulating lipids in their cytoplasm. Eventually, the mature sebocytes disintegrate and release their lipid-rich contents into the hair follicle duct, where the sebum is secreted onto the skin's surface.

Sebum composition: Sebum is a complex mixture of lipids, including triglycerides, wax esters, squalene, and free fatty acids. This lipid mixture provides several functions: It acts as a barrier to protect the skin from external contaminants, reduces water loss, and possesses antimicrobial properties that help prevent skin infections [1-3].

Regulation of sebum production

Sebum production is regulated by several factors, including hormonal signals, genetic predisposition, and external environmental factors.

Hormonal influence: Androgens, particularly Dihydrotestosterone (DHT), play a significant role in stimulating sebum production. This is why sebaceous gland activity increases during puberty when androgen levels rise. Other hormones, such as Insulin-like Growth Factor (IGF-1), can also influence sebaceous gland function.

Genetic factors: Genetics significantly influence sebaceous gland activity and sebum production. Individuals with a family history of oily skin or acne are more likely to experience similar issues due to inherited genetic predispositions.

Environmental and lifestyle factors: External factors, such as diet, stress, and environmental conditions, can also impact sebum production. For example, diets high in refined sugars and dairy have been linked to increased sebum production and acne development. Stress can trigger hormonal changes that elevate sebum production, while environmental factors like humidity and temperature can affect the skin's oiliness [4-6].

Clinical significance of sebaceous glands

Sebaceous glands play a important role in various skin conditions, most notably acne, seborrheic dermatitis, and certain rare disorders.

Acne vulgaris: Acne is the most common condition associated with sebaceous glands. It is characterized by the blockage and inflammation of hair follicles due to excessive sebum production, hyperkeratinization (increased shedding of skin cells), and bacterial proliferation, particularly Propionibacterium acnes. This leads to the formation of comedones (blackheads and whiteheads), papules, pustules, and in severe cases, cysts and nodules.

Seborrheic dermatitis: This chronic inflammatory skin condition affects areas rich in sebaceous glands, such as the scalp, face, and upper body. It manifests as red, scaly patches with a greasy appearance. While the exact cause is unknown, it is believed that an overgrowth of Malassezia yeast, which thrives in oily environments, plays a role.

Sebaceous hyperplasia: Sebaceous hyperplasia is a condition where sebaceous glands become enlarged, resulting in yellowish, soft papules on the skin, commonly on the forehead, cheeks, and nose. This condition is generally benign but can be aesthetically concerning for some individuals.

Sebaceous gland disorders: Rarely, sebaceous glands can develop into benign or malignant tumors. Sebaceous adenomas are benign tumors that appear as small, yellowish nodules. Sebaceous carcinoma, although rare, is a malignant tumor that requires prompt medical attention due to its aggressive nature and potential for metastasis [7-10].

References

1. Safavi KH, Muller SA, Suman VJ, Moshell AN, Melton LJ. Incidence of alopecia areata in Olmsted County, Minnesota, 1975 through 1989. Mayo Clin Proc. 1995;70(7):628-633.

   [Crossref] [Google Scholar]

2. Xing L, Dai Z, Jabbari A, Cerise JE, Higgins CA, Gong W, et al. Alopecia areata is driven by cytotoxic T lymphocytes and is reversed by JAK inhibition. Nat Med. 2014;20(9):1043-1049.

   [Crossref] [Google Scholar]

3. Khanna MD. Hair transplantation surgery. Indian J Plast Surg. 2008:41(1):56-63.

   [Crossref] [Google Scholar]

4. Ito T, Ito N, Saatoff M, Hashizume H, Fukamizu H, Nickoloff BJ, et al. Maintenance of hair follicle immune privilege is linked to prevention of NK cell attack. J Invest Dermatol. 2008;128(5): 1196-1206.

   [Crossref] [Google Scholar]

5. King B, Ohyama M, Kwon O, Zlotogorski A, Ko J, Mesinkovska NA, et al. Two phase 3 trials of baricitinib for alopecia areata. N Engl J Med. 2022;5(18):1687-1699.

   [Crossref] [Google Scholar]

6. Oka A, Takagi A, Komiyama E, Yoshihara N, Mano S, Hosomichi K, et al. Alopecia areata susceptibility variant in MHC region impacts expressions of genes contributing to hair keratinization and is involved in hair loss. EBio Medicine. 2020;57:102810.

   [Crossref] [Google Scholar]

7. Sundberg JP, Cordy WR, King LE. Alopecia areata in aging C3H/HeJ mice. J Investig Dermatol. 1994;102:847-856.

   [Crossref] [Google Scholar]

8. Zhao Q, Koyama S, Yoshihara N, Takagi A, Komiyama E, Wada A, et al. The alopecia areata phenotype is induced by the water avoidance stress test in CCHCR1-deficient mice. Biomedicines. 2021;9(7):840.

   [Crossref] [Google Scholar]

9. Koyama S, Yoshihara N, Takagi A, Komiyama E, Oka A, Ikeda S. Clinical findings, response to steroid treatment, and recurrence rate in alopecia areata patients with or without a nonsynonymous variant of coiled-coil alpha-helical rod protein 1. Ann Dermatol. 2023;35(5):367-373.

   [Crossref] [Google Scholar]

10. Salloum A, Bazzi N, Maalouf D, Habre M. Microneedling in vitiligo: A systematic review. Dermatol Ther. 2020;33(6):142-197.

    [Crossref] [Google Scholar]