Histological and immunohistochemical characterization of the Mongolian gerbil’s mammary gland during gestation, lactation and involution

Abstract

The morphological description of normal tissues is fundamental for making comparisons and in order to identify injuries and lesions. The aim of this work was to describe the morphological characteristics of the female Mongolian gerbil's (Meriones unguiculatus) normal mammary gland, the average expression of hormone receptors, and the average proliferation rates in the epithelial cells during the periods of lactation, pregnancy and involution. Dams were euthanized on the 14th and 21st gestational days, 7 and 14days after parturition, and 3 and 5days after weaning. The dams' mammary tissues were processed and were submitted to haematoxylin and eosin staining, Periodic Acid Schiff (PAS) staining, and Gomori's Reticulin staining. Additionally, immunohistochemistry was performed for the characterization of myoepithelial cells with α-actin, the proliferation rates with proliferating cell nuclear antigen (PCNA), the estrogen hormonal receptors (ESR1 and ESR2), and progesterone receptor (PR) quantifications. It was observed that the abundant adipose tissues were replaced by glandular epithelia and there was an increase in the epithelial cell's height (from 5.97 to 32.4μm in 14th and 21st gestational days and from 20.64 to 25.4μm in 7th and 14th lactational days, respectively) and the acini diameters (from 24.88 to 69.92μm in 14th and 21st gestational days and from 139.69 to 118.59μm in 7th and 14th lactational days, respectively) with the progression of gestation and lactation. The PAS staining intensity varied throughout the glands and between the stages that were evaluated. The extracellular matrix showed different phenotypes too, with more of a presence of the Type I collagen during the early gestation and involution and with more reticular fibers (Type III collagen) during the late gestation period and lactation. The myoepithelial layers showed alterations in their distribution with thick patterns as verified by the α-actin labeling. The PCNA showed higher rates of the marked cells in 14th and 21st gestational days (40.25 and 60.28%) and in 7th and 14th lactational days (64.08 and 65.08%). The hormone receptor quantifications showed a high variation in the rates: the average PR staining decreased from 14th to 21st gestational days (from 42.3 to 8.54%), from 7th to 14th lactational days (from 59.83 to 23.18%) and from 3rd to 5th days after weaning (from 39.98 to 12.72). There were higher averages of ESR1 staining in gestational days 14 and 21(from 58.06 to 30.02%). ESR2 staining decreased during gestation (25.7 and 12.94% in 14th and 21st gestational days)and involution (from 50.97 to 30.18% in 3rd and 5th days after weaning). The Mongolian gerbils showed similar morphological characteristics when they were compared to mice and rats. However, the higher proliferation rates with a smaller involution period compared to other murine characterized this species as being adequate for mammary pathologies studies.

Telocytes are associated with tissue remodeling and angiogenesis during the postlactational involution of the mammary gland in gerbils

“…In addition, our data indicate that the mammary gland in the gerbil remains highly proliferative in postlactational involution, which corroborates a previous study (Leonel et al, 2017), conversely to what is seen in other laboratory rodents in which there is a decrease in epithelial proliferation during this period (Allan, Beattie, & Flint, 2004). Our data also indicate an intense process of angiogenesis in the gland during involution.…”

“…Among laboratory rodents, the Mongolian gerbil is known for its easy handling and high susceptibility to pathological conditions (Sanches et al, 2014, 2020; Santos & Taboga, 2006), being used in experiments on physiology, development, and pathogenesis in several organs (Biancardi, Dos Santos, de Carvalho, Sanches, & Taboga, 2017; Christante, Taboga, Pinto‐Fochi, & Góes, 2013; Perez et al, 2012; Sanches et al, 2017; Santos et al, 2008), including the mammary gland. It was found that the adult mammary gland in gerbils presents a more proliferative profile during reproductive life compared to other laboratory rodents, such as rats and mice, in addition to a possible greater susceptibility to tumorigenesis (Leonel, Falleiros, Campos & Taboga, 2017), but the dynamics of mammary gland involution in the gerbil and the possible function of telocytes remain poorly understood. Therefore, this study aims to evaluate the presence of telocytes in the mammary gland in gerbils during postlactational involution, as well as a possible role for these cells.…”

Histochemical and Immunohistochemical Examination of Cranial and Caudal Gland Alveolar Secretion of the Same Lactating Mammary Gland Quarter of One Humped She Camel (Camelus dromedarius)

“…To identify the carbohydrates in the secretion of the lactating mammary gland, Ellen et al (2017) and Swapna et al (2020) used PAS stain during different stages of milk production. The results of these studies revealed that the intensity of the PAS reaction differed throughout the milk production process in a direct correlation to the level of carbohydrates and mucins in the secretion.…”

Effect of Propolis on Precocious Puberty in Female Rats

“…Mammary gland tissues were examined using a Nikon eclipse inverted microscope (Nikon Corp., Tokyo, Japan), and the area (µm 2 ) of secretory epithelium and fat cells and the area of stroma were calculated using the NIS-element imaging system from the same manufacturer. The ratio of the area of the secretory epithelium and fat cells to the area of the stroma was then calculated ( 16 ). Ki-67 staining was used to demonstrate tissue stimulation and proliferation in the endometrium, mammary glands, and ovaries.…”