Seasonal expression of 5α-reductases and androgen receptor in the prostate gland of the wild ground squirrel (Spermophilus dauricus)

Epithelial-mesenchymal transition during the growth and involution of the prostate gland in wild ground squirrels (Spermophilus dauricus)

The prostate glands of wild ground squirrels display enlarged volume during the breeding season and shrunk size during the nonbreeding season, which enables the wild ground squirrel to be an ideal animal model for studying the mechanisms of prostate growth and involution. To clarify the possible mechanism underlying seasonal morphological changes of the prostate in wild ground squirrels, epithelial-mesenchymal transitions (EMT) were focused, and the expression of EMT-related genes was investigated in the current study. Histological results showed that the epithelial lumen enlarged in the breeding season, and the stromal cells expanded during the non-breeding season. Transcriptomic analysis showed 132 EMT-related genes expressed differentially in the prostate during breeding versus non-breeding seasons, indicating EMT might occur during the morphological changes of the prostate. To further confirm the EMT process, the immunolocalizations of EMT markers were inspected, which showed the positive staining of E-cadherin, Claudin-1, ZO1, β-catenin, N-cadherin, VIMENTIN, SLUG, and ZEB1 were presented in epithelial and/or stromal cells. The expressions of Cdh1, Cldn, Tjp1, Ctnnb1, and Snai2 increased in the prostate of the breeding season, while the expressions of Cdh2, Vim, and Zeb1 reduced in the prostate of the breeding season. Moreover, the expression levels of the epithelial marker Cdh1 and the mesenchymal markers Cdh2 and Vim were found to be positively or negatively correlated with prostate weight, respectively. In conclusion, the current results suggested that the EMT might be responsible for prostate growth and involution in the wild ground squirrel.

Seasonal changes of the prostate gland in the raccoon (Procyon lotor) inhabiting Hokkaido, Japan

In the prostate gland of the raccoon (Procyon lotor), the morphological appearance of the epithelial cells, such as basal and luminal cells, and the expressions of p63, androgen receptor (AR), and proliferating cell nuclear antigen (PCNA) were examined histologically and immunohistochemically to clarify their seasonal dynamics throughout the year. In this study, the regression with luminal cell defluxion and the regeneration process of the prostatic glandular epithelium was revealed in the seasons with declined spermatogenesis (June to August). The expression of p63 was observed only in the basal cells. AR immunoreactivity in the luminal cells was shown in the developed and regenerating (close to developed) prostates, whereas the basal cells exhibited AR immunoreactivity all year round. PCNA expression was rare in epithelial cells of the developed prostate gland. In the regressed gland, the basal cells demonstrated proliferative ability, whereas PCNA of the luminal cells appeared for the first time in the regenerating phase. This study is the first to clarify the regression with luminal cell defluxion and restoration and the seasonal dynamics of AR expression and proliferative activity in the prostate gland of seasonal breeders.

Estrogen signaling regulates seasonal changes of the prostate in wild ground squirrels (Spermophilus dauricus)

Previous studies found that testosterone was converted to dihydrotestosterone under the catalysis of 5α-reductase in the prostate of the wild ground squirrels. As a result, this study explored further whether testosterone could be converted to estrogen to affect the prostate gland function in wild ground squirrels. Histological observation showed that the area of epithelial cells and the prostatic secretory lumen were enlarged significantly during the breeding period. Transcriptome analysis revealed that the differentially expressed genes in the prostate were concentrated in the estrogen signaling pathway. Immunohistochemical analysis showed that the immunoreactivities of P450arom were detected in the stromal cells during the breeding and non-breeding periods, indicating the possible conversion of androgen into estrogen locally. Moreover, the immunolocalizations of ERα and ERβ were detected mainly in the epithelial or stromal cells. Additionally, qPCR analysis displayed that the mRNA expression level of P450arom in the prostate was significantly higher during the breeding period than that in the non-breeding period. Consistently, the concentration of 17β-estradiol (E₂) was higher in the prostate during the breeding period than the non-breeding period, which is positively correlated with the seasonal changes of prostatic weight. In conclusion, the present results indicated that estrogen produced by P450arom presented in stromal cells might regulate the growth and function of the prostate gland via the locally expressed estrogen receptors in wild ground squirrels. The results of this study were momentous for further uncovering the mechanism of the seasonal regulated by signal pathways in the prostate of wild ground squirrels.

Seasonal expressions of VEGF and its receptors VEGFR1 and VEGFR2 in the prostate of the wild ground squirrels (<em>Spermophilus dauricus</em>)

As a vital male accessory reproductive gonad, the prostate requires vascular endothelial growth factors for promoting its growth and development. In this study, we investigated the localizations and expressions of vascular endothelial growth factor (VEGF) and its receptors including VEGF-receptor1 (VEFGR1) and VEGF-receptor2 (VEGFR2) in the prostate of the wild ground squirrels during the breeding and the non-breeding seasons. The values of total prostate weight and volume in the breeding season were higher than those in the non-breeding season. Histological observations showed that the exocrine lumens of the prostate expanded in the breeding season and contracted in the non-breeding season. The mRNA expression levels of VEGF and VEGFR2 in the prostate were higher in the breeding season than those in the non-breeding season, but the mRNA expression level of VEGFR1 had no significant change between the breeding and non-breeding seasons. Immunohistochemical results revealed that VEGF, VEGFR1 and VEGFR2 were presented in epithelial and stromal cells during the breeding and non-breeding seasons. In addition, the microvessels of the prostate were widely distributed and the number of microvessels increased obviously in the breeding season, while decreased sharply in the non-breeding season. These results suggested that expression levels of VEGF and VEGFR2 might be correlated with seasonal changes in morphology and functions of the prostate, and VEGF might serve as pivotal regulators to affect seasonal changes in the prostate functions of the wild male ground squirrels via an autocrine/paracrine pathway.

The seasonal profile of proliferation and apoptosis in the prostate gland of the wild ground squirrel (Spermophilus dauricus)

The seasonal cycle of growth and regression in the prostate gland of wild ground squirrel provide a unique research model to understand the morphological changes of prostate glands. Our previous studies showed that the local production of dihydrotestosterone could affect the morphology and function of the prostate gland in either an autocrine or paracrine manner. In the present study, we attempted to gain more insight into this process by investigating the expression of key factors implicated in cell proliferation, apoptosis, and the cell cycle, including mechanistic target of rapamycin (mTOR), cyclin-D2, p21, p27 and retinoblastoma 1 (pRB). Morphological and histological observations confirmed that the prostate increased significantly in both size and weight during the breeding season. Positive immunostaining for proliferating cell nuclear antigen (PCNA) was mainly localized to the prostate epithelial cells during the breeding season, which is significantly higher in the prostate gland during the breeding season (2470 ± 81/mm²) than that in the nonbreeding season (324 ± 54/mm²). However, there was no significant difference in the prostate gland when compared between the breeding and nonbreeding seasons, with regards to TUNEL staining. Moreover, cell cycle regulators were mainly localized to the epithelial cells, including mTOR, cyclin-D2, p21, p27 and pRB. the immunostaining of mTOR and cyclin D2 were stronger during the breeding season, whereas the immunostaining of p27 and pRB were stronger during the nonbreeding season. The mRNA expression levels of mTOR, cyclin D2, and PCNA, were higher during the breeding season while those of p27 and p21 were higher during the nonbreeding season. Collectively, this study profiled the distinct expression pattern of key cell cycle regulators throughout the breeding and nonbreeding seasons. Collectively, these factors may play important roles in regulating the seasonal growth and regression of the prostatic epithelium in the wild ground squirrel.

Seasonal expressions of SF-1, StAR and P450scc in the scent glands of the muskrats (Ondatra zibethicus)

The steroidogenesis occurs in specific cells and tissues in the mammals which begins with the transfer and intracellular processing of cholesterol converted to pregnenolone. This study investigated the gene and protein expression levels of steroidogenic factor 1 (SF-1), steroidogenic acute regulatory protein (StAR) and cytochrome P450 cholesterol side-chain cleavage enzyme (P450scc) in the scent glands of the muskrats during the breeding and non-breeding seasons. The immunohistochemical localizations of StAR and P450scc were identified in the glandular cells and epithelial cells while SF-1 was only expressed in glandular cells during the breeding and non-breeding seasons. The gene and protein expression levels of SF-1, StAR and P450scc in the scent glands were remarkedly higher in the breeding season than those of the non-breeding season. The interaction of micro RNAs (miRNAs) and transcriptome results showed that miR-762 and miR-4454 might be the genes encoding (Nr5a1, Star and Cyp11a1) in key biological processes. Taken together, these results suggested that the scent glands of the muskrats potentially owned ability to synthesize steroid hormones de novo, and the steroid hormones might affect the scent glandular functions of the muskrats during the breeding and non-breeding seasons.

Seasonal expressions of prostaglandin E synthases and receptors in the prostate of the wild ground squirrel (Spermophilus dauricus)

The prostate gland is a male accessory reproductive gland, whose vitality and function are under tight regulation of different hormones. Prostaglandins E2 (PGE2) is one of the major products generated by the actions of cyclooxygenases (COX) and prostaglandin E synthase (PTGES) on arachidonic acid, and is involved in a number of physiological and pathological processes. In this study, we investigated the seasonal immunolocalizations and expressions of COX-1, COX-2 and PTGES, as well as PGE2 receptors (PTGERs) subtypes 1-4 (EP1, EP2, EP3, EP4) in the prostate of the wild ground squirrel. Histological examination observed enlarged prostatic lumens in the breeding season and significantly shrunken lumens in the nonbreeding season. COX-1, COX-2, PTGES and PTGERs were mainly localized in epithelial and stromal cells in the breeding and nonbreeding seasons. The mRNA expression levels of Cox-1, Cox-2, Ptges, Ptger2 (encoding EP2) and Ptger4 (encoding EP4) were higher in the prostate of the breeding season than in the nonbreeding season. The relative mRNA levels of Cox-1, Cox-2, Ptges, Ptger2 and Ptger4 were positively correlated with prostatic weights. In addition, both the prostatic and plasma concentrations of PGE2 were significantly higher in the breeding season compared to the nonbreeding season. These results suggested that PGE2 synthesis and signaling might play an important autocrine or paracrine role in the regulation of seasonal changes in the prostatic function of the wild ground squirrel.

Seasonal expressions of prolactin, prolactin receptor and STAT5 in the scented glands of the male muskrats (Ondatra zibethicus)

Prolactin (PRL) production in mammals has been demonstrated in extrapituitary gland, which can activate autocrine/ paracrine signaling pathways to regulate physiological activity. In the current study, we characterized the gene expression profiles of PRL, prolactin receptor (PRLR) and signal transducers and activators of transcription 5 (STAT5) in the scented glandular tissues of the muskrats, to further elucidate the relationship between PRL and the scented glandular functions of the muskrats. The weight and volume of the scented glands in the breeding season were significantly higher than those of the non-breeding season. Immunohistochemical data showed that PRL, PRLR and STAT5/phospho-STAT5 (pSTAT5) were found in the glandular and epithelial cells of the scented glands in both seasons. Furthermore, we found that PRL, PRLR and STAT5 had higher immunoreactivities in the scented glands during the breeding season when compared to those of the non-breeding season. In parallel, the gene expressions of PRL, PRLR and STAT5 were significantly higher in the scented glands during the breeding season than those of the non-breeding season. The concentrations of PRL in scented glandular tissues and sera were measured by enzymelinked immunosorbent assay (ELISA), and their levels were both notably higher in the breeding season than those of the nonbreeding season. These findings suggested that the scented glands of the muskrats were capable of extrapituitary synthesis of PRL, which might attribute PRL a specific function to an endocrine or autocrine/paracrine mediator.