Development and homeostasis of the sebaceous gland

The important role of epidermal appendages especially the sebaceous gland has only recently been recognized. In particular, it has been convincingly shown that normal development and maintenance of the sebaceous gland are required for skin homeostasis since atrophic sebaceous glands and disturbances in sebaceous lipid composition result in major defects of the physiological barrier and maintenance of the skin. Consequently, it is important to unravel the signaling network controlling proper sebaceous lineage differentiation in mammalian skin and to understand the underlying mechanisms leading to severe skin diseases, including abnormal proliferation and differentiation of the gland, defects of the lipid metabolism and barrier, as well as sebaceous tumor formation. Over the last years, results from transgenic and knock out mouse models manipulating distinct signaling pathways in the skin as well as the detailed analysis of human sebaceous gland-derived cell lines provided new insights into crucial mediators balancing proliferation and differentiation of the sebaceous gland. Here, we discuss our current knowledge of in vivo mechanisms of sebaceous gland development, maintenance and disorders and highlight recent contributions to the field of sebaceous gland biology.     

Lectin histochemical study on the infraorbital gland of the Japanese serow (Capricornis crispus)

Histology and lectin histochemistry were performed in the infraorbital gland of the Japanese serow. The gland is composed of glandular tissues and a pouch filled with the secretion. The tissues consist of an inner layer of sebaceous glands and an outer layer of apocrine glands. The male sebaceous layer is made up of the ordinary type, whereas the female's layer consists of the ordinary and modified types. In the apocrine gland stained with Arachis hypogaea (PNA), nine different patterns of glandular tubules were distinguished on the basis of staining of the cytoplasm, the Golgi area of secretory cells and secretion. Secretory modes of apocrine secretion and exocytosis were included in these stainings. Myoepithelial cells stained constantly with Glycine max (SBA) except when only the Golgi area of secretory cells was positive. The modified sebaceous gland was stained with PNA, SBA, Ricinus communis I (RCA), Triticum vulgaris (WGA), Canavalia ensiformis (Con A) and Ulex europaeus I (UEA), while the ordinary type was positive in PNA, RCA, SBA, WGA and Con A. The secretion in the pouch was stained with PNA, RCA, SBA, Dolichos biflorus (DBA), WGA and Con A. These findings suggest that the modified sebaceous gland contains large amounts of glycoconjugates and the apocrine gland shows a cyclic secretory process of apocrine secretion and exocytosis.     

Hydrolytic enzymes in the sebaceous glands of the domestic cat

Synopsis The distribution and activities of some hydrolytic enzymes in various portions of the sebaceous glands of the domestic cat have been studied. The results point to the outstanding importance of non-specific esterases and lipases for sebum production, which generally appears to be abundant in thickly-haired mammals. The activities of the lysosomal enzymes demonstrated were connected with autolytic processes during sebaceous gland cell differentiation. There was a strong arylsulphatase reaction in the sebum of the sebaceous gland excretory ducts.     

Histomorphology of preorbital gland in territorial and non-territorial male blackbuck Antelope cervicapra, a critically endangered species

The preorbital gland is a specialized dermal gland of antelopes which plays an important role in territorial marking behavior and pheromonal communication. To our knowledge, there is little information available on the role of preorbital gland marks in Indian antelopes (blackbucks). Males are seen averting the gland during behavioural display and territorial marking but the functional aspect of this gland has not been examined. Hence, the aim of this study was to describe the histomorphology of the preorbital gland in territorial and non-territorial male blackbucks to determine its morphology and secretory function. The results showed that the preorbital gland is composed of modified sebaceous and apocrine glands. The apocrine gland is lined by simple cuboidal epithelial cells; the serous parts of the secretory products are often seen in the apical portions of the cells. The myoepithelial cells contain actin filaments lying on the basal membranes of the apocrine gland. There are some considerable histological changes in the presence of the sebaceous and apocrine glands in territorial males in comparison to non-territorial males. The following histological changes associated with occurrence of the sebaceous and apocrine glands have been observed in territorial and non-territorial male blackbucks: (1) increase of size of sebaceous and apocrine glands and (2) increase in density of sebaceous and apocrine glands in territorial males compared to non-territorial males. It is suggested that the higher development (i.e., size) and density of sebaceous and apocrine glands in territorial males could depend on hormone production (i.e., testosterone). Based on the histological observation and the role of sebaceous and apocrine glands in the preorbital gland supported by literature, it is possible to conclude that both territorial and non-territorial blackbuck males may produce pheromonal substances through preorbital gland (secretion) for olfactory communication.     

Fine structure of the gular gland of the free-tailed bat Tadarida brasiliensis

The gular gland of the bat Tadarida brasiliensis is a specialized sebaceous gland located in the skin of the suprasternal region of adult males. It consists of an aggregation of simple branched tubulo-acinar gland units, the number of which varies seasonally. Each acinus is composed of densely packed sebaceous cells at various stages of differentiation. Acinar basal cells and cells of the epithelium of the ducts can differentiate into sebaceous cells. Two main changes appear in the cytoplasm concurrent with the sebaceous transformation: the differentiation of cytoplasmic organelles and the deposition of lipid material. The appearance of a different type of mitochondrion and the development of large numbers of ribosomes and polyribosomes can be recognized in the cytoplasm at an early stage of differentiation. Concomitant with the deposition of significant numbers of lipid droplets, the cells develop abundant agranular endoplasmic reticulum occurring mainly as scattered tubular cisternae. These at times form whorls surrounding lipid droplets. At later stages, the cisternae of the agranular endoplasmic reticulum often occur in crystalline arrays between secretory oil droplets. The roles of the different cytoplasmic organelles, especially in relation to the production of sebum, are discussed.     

Testosterone-dependent primer pheromone production in the sebaceous gland of male goat

To test the hypothesis that the primer pheromone responsible for inducing the "male effect" is produced in the sebaceous gland androgen dependently, we examined the correlation between morphological changes of sebaceous glands and the pheromone activity in skin samples taken from castrated goats that had been treated with testosterone. Five castrated goats were implanted s.c. with testosterone capsules to maintain physiological levels of plasma testosterone for four weeks. Skin samples were obtained from the head region on Day 0 (the day of testosterone implant), Day 7, Day 14, Day 28 (the day of testosterone removal), Day 36, Day 42, and Day 56. Matched blood samples were also collected for measurement of testosterone concentration. The pheromone activity of the ether-extracts of the upper dermal layer containing sebaceous glands was assessed by its stimulatory effect on the hypothalamic GnRH pulse generator, which was monitored for changes of specific multiple unit activity (MUA) in ovariectomized estradiol-primed goats as described previously. The sebaceous gland enlarged during the testosterone treatment but reduced in size after testosterone removal. The pheromone activity first appeared in 2 out of 5 goats on Day 7 and in all the 5 goats by Day 28. Fourteen days after testosterone removal (Day 42), the pheromone activity was no longer detectable in any of the 5 goats. In short, the sebaceous gland size and the pheromone activity shifted almost in parallel. The present results provide strong support for the view that the primer pheromone is produced testosterone dependently in the sebaceous gland of the male goat.     

Absence of 5 alpha-dihydrotestosterone action in the sebaceous-like uropygial gland of the male Japanese quail

The uropygial gland of the quail, a sebaceous-like gland, has been proven to be androgen-dependent. Waxes secreted by this gland consist of fatty acids esterified by alkane-2,3-diols [12]. In castrated quails, the relative concentration of dodecane diol was enhanced after testosterone treatment; but 5 alpha-DHT could not evoke any increase in the relative concentration of dodecane diol. It is not possible from our present results to know if this lack of gland response to DHT administration is related to a high level of DHT metabolism in the gland cells or to a decreased affinity of the androgen receptor for DHT. However, because of the high similarity existing between uropygial gland of birds and mammalian sebaceous glands, these results give rise to the question of the true role of DHT in mammalian sebaceous glands.     

Evolutionary origins of the mammary gland

Because the mammary gland has no known homologue among the extant reptiles, attempts to reconstruct its evolution must focus on evidence from living mammals. Of the numerous structures that have been hypothesized to have given rise to the mammary gland, only three remain as plausible progenitors: sebaceous glands, eccrine glands and apocrine glands. Ancestral mammary glands are usually assumed to have produced a copious watery secretion like that of human eccrine sweat glands. However, in terms of anatomy, physiology, development and topographical distribution, mammary glands are more similar to apocrine and sebaceous glands than to typical eccrine glands. Nevertheless, each of the three populations of cutaneous glands exhibit specializations unlikely to be primitive for the mammary gland. The mammary gland either predated full differentiation of mammalian cutaneous glands or, more probably, evolved as a neomorphic mosaic that combined the properties of apocrine and sebaceous glands. Consequently, ancestral, prototypic lacteal glands may have had the capacity to synthesize and secrete small amounts of organic substances, as do sebaceous and apocrine glands of living mammals.     

Jugulo-sternal-gland tumors in male tree shrews (Tupaia belangeri).

Adenocarcinomas of the jugulo-sternal glands were observed in seven adult male tree shrews (Tupaia belangeri) at biopsy or necrospy. Five of these tumors were classified as carcinomas of the sebaceous gland compartment; one was diagnosed as a papilliform adenoma of apocrine (monoptychic) sweat glands; and one was of a mixed sebaceous gland/apocrine sweat gland structure. Four sebaceous gland carcinomas had histologic evidence of vascular invasion; one had metastasized to the regional lymph nodes and lungs and had also invaded the thoracic muscles.     

毛囊分子调控机制

毛囊是产生毛被的组织,具有周期性,经历生长期、衰退期和休止期三个时期,毛囊与皮脂腺组成毛囊皮脂腺单位。本文从分子层面分别对调控毛囊周期性变化、毛囊皮脂腺发育以及毛囊中影响毛被光泽度及毡结度的因子等给予了详细阐述,这些均为提高山羊绒产量和质量提供了重要思路。     

The preputial gland of the Japanese serow Capricornis crispus: ultrastructure and lectin histochemistry

Preputial glands of the Japanese serow were found to consist of the modified sebaceous gland and apocrine gland in both sexes. In the modified sebaceous gland, cells transformed gradually toward the lumen from plentiful cytoplasm to a sponge-like network. Lipid droplets were observed in mitochondria of differentiating cells. By lectin histochemistry, differentiating cells were stained with Arachis hypogaea (PNA), Triticum vulgaris (WGA) and Canavalia ensiformis (Con A) lectins, while secretory cells of the apocrine gland revealed various stainings with PNA, Glycine max, Dolichos biflorus, WGA and Con A lectins. These findings suggest that glycoconjugates may have an active function in the preputial gland.     

Ultrastructural changes in the uropygial gland of the male Japanese quail,Coturnix coturnix,after testosterone treatment

Summary The ultrastructure of the uropygial gland of the male quail was compared to that of the sebaceous gland of the male rat after castration and testosterone treatment of both species. In intact animals, the differentiating cells of these glands displayed almost the same pattern as regards their smooth endoplasmic reticulum, an organelle involved in lipogenesis in both cases. Castration reduced the volume of this organelle, while testosterone administration restored cell morphology to a normal or supranormal level. Finally, this study showed that at ultrastructural level, there is a close functional analogy between the uropygial gland of quail and the sebaceous glands of rats as regards their androgen dependency. Consequently, the uropygial gland might be an attractive model for study of action of androgens on sebaceous-like glands.     

A novel serine protease overexpressed in the hair follicles of nude mice.

We have studied changes in gene expression between normal and nude mouse skin. Using the method of representational difference analysis, a cDNA encoding a novel serine protease designated BSSP was cloned. Our results show that in skin this gene is predominantly expressed in the sebaceous gland of the hair follicle and in the distal part of the outer root sheath. Thus, BSSP is the first serine protease known to be expressed in the sebaceous gland. In nude mouse skin, this gene is overexpressed.     

Comparative responsiveness of supracaudal and other sebaceous glands in male and female guinea pigs to hormones

Different types of sebaceous glands in guinea pigs were chosen to study their comparative responsiveness to steroid hormones. Glands selected were (1) Sebaceous glands associated with rudimentary hair in the supracaudal gland; (2) Free sebaceous glands of the nipple; (3) Sebaceous glands associated with the hair. The results showed distinct differences in sensitivity among these different sebaceous glands and according to the sex of the experimental animal. The most responsive of the glands in males was the supracaudal gland; in the female the most responsive glands were the sebaceous glands of the nipple. Sebaceous glands associated with normal hair were relatively insensitive to changes in hormonal level. In all cases testosterone propionate was more potent in stimulating any of the sebaceous glands than progesterone. After gonadectomy, various sebaceous glands showed unequal states of depletion due to the different rates of differentiation and disintegration of their cells into sebum.     

Endogenous retinoids in the hair follicle and sebaceous gland

Vitamin A and its derivatives (retinoids) are critically important in the development and maintenance of multiple epithelial tissues, including skin, hair, and sebaceous glands, as shown by the detrimental effects of either vitamin A deficiency or toxicity. Thus, precise levels of retinoic acid (RA, active metabolite) are needed. These precise levels of RA are achieved by regulating several steps in the conversion of dietary vitamin A (retinol) to RA and RA catabolism. This review discusses the localization of RA synthesis to specific sites within the hair follicle and sebaceous gland, including their stem cells, during both homeostasis and disease states. It also discusses what is known about the specific roles of RA within the hair follicle and sebaceous gland. This article is part of a Special Issue entitled: Retinoid and Lipid Metabolism.     

Fine needle aspiration cytology of a sebaceous lymphadenoma: a case report

BACKGROUND: Sebaceous lymphadenoma is a rare, benign neoplasm, histologically characterized by proliferating islands of epithelium with sebaceous glandular differentiation in a dense, lymphocytic background. The parotid gland is the most common site, and the patient usually presents with a well-circumscribed, enlarging and painless mass. Primary sebaceous lesions of the salivary glands are very rare entities and must be differentiated from more common, potentially malignant tumors. CASE: A 75-year-old male presented with a 6-month history of a mass in the tail of the parotid gland. The mass was not fixed or tender to palpation, was well delineated and measured 4 cm in greatest dimension. Fine needle aspiration (FNA) revealed a mixed population of large and small lymphocytes, including plasma cells and occasional tingible body macrophages. Scattered among the lymphocytes were 3-dimensional, cohesive aggregates of epithelial cells, many demonstrating the characteristic cytoplasmic vacuolization of sebocytes, surrounded by layers of basaloid cells. No mitoses or cellular pleomorphism was identified. These findings suggested a sebaceous lymphadenoma, confirmed on biopsy. CONCLUSION: Although sebaceous lymphadenoma is encountered infrequently, FNA findings can result in its accurate diagnosis.     

Further observations on spontaneous neoplasms in the Mongolian gerbil, Meriones unguiculatus.

One hundred sixty Mongolian gerbils, Meriones unguiculatus, were examined for the presence of naturally occurring lesions. The first recognized cases of cecal adenocarcinoma, testicular teratoma, and sebaceous gland pad carcinoma were found. Neoplasms previously reported from the gerbil and also seen in the present study included ovarian theca lutein and granulosa lutein cell tumors, sebaceous gland pad adenoma, cutaneous squamous cell carcinoma, malignant melanoma, and renal and splenic hemangiomas. Calcinosis cutis was also observed in two male gerbils.     

Thematic review series: Skin Lipids. Sebaceous gland lipids: friend or foe?

Sebaceous glands are intriguing glands that are found throughout the human body except on the palms of the hands and soles of the feet. The true function of these glands has yet to be determined, but there are several theories, including antioxidant effects, antibacterial effects, and transport of pheromones. Sebaceous glands produce lipids that are involved in the pathogenesis of one of the most prevalent diseases of adolescence, acne. Although the majority of lipids produced by the sebaceous gland are also produced in other areas of the body, there are two that are characteristic of the sebaceous gland, wax esters and squalene. This review seeks to present an update on the physiology of the sebaceous glands, with particular emphasis on the production of sebaceous lipids.     

CHALONE CONTROL OF MITOTIC ACTIVITY IN SEBACEOUS GLANDS

Extracts of skin with sebaceous glands contain a substance which inhibits mitotic activity in sebaceous glands both in vivo and in vitro. This substance is neither the epidermal chalone nor the melanocyte chalone, both of which are also present in skin extracts. However, it resembles these other chalones in that it is water soluble, is precipitated by ethanol, is activated by the two stress hormones adrenalin and hydrocortisone, and is not species specific. It is present within the sebaceous glands, and it is evidently a sebaceous gland chalone.     

Imaging sebaceous gland using optical coherence tomography with deep learning assisted automatic identification

Imaging sebaceous glands and evaluating morphometric parameters are important for diagnosis and treatment of serum problems. In this article, we investigate the feasibility of high-resolution optical coherence tomography (OCT) in combination with deep learning assisted automatic identification for these purposes. Specifically, with a spatial resolution of 2.3 μm × 6.2 μm (axial × lateral, in air), OCT is capable of clearly differentiating sebaceous gland from other skin structures and resolving the sebocyte layer. In order to achieve efficient and timely imaging analysis, a deep learning approach built upon ResNet18 is developed to automatically classify OCT images (with/without sebaceous gland), with a classification accuracy of 97.9%. Based on the result of automatic identification, we further demonstrate the possibility to measure gland size, sebocyte layer thickness and gland density.