Seasonal variation of prostatic steroid hormone synthesis capacity in wild ground squirrels (Spermophilus dauricus)

Our previous studies showed that the prostates of the wild ground squirrels were capable of locally synthesizing testosterone (T), dihydrotestosterone (DHT) and estrogen. In this study, we investigated expression levels of luteinizing hormone receptor (LHR), steroidogenic factor 1 (SF-1), steroidogenic acute regulatory protein (StAR), cytochrome P450 cholesterol side-chain cleavage enzyme (P450scc), 3β-hydroxysteroid dehydrogenase (3βHSD) and 17α-hydroxylase cytochrome P450 (P450c17) in the prostates of the wild ground squirrels during the breeding and non-breeding seasons. LHR, SF-1, StAR, P450scc, 3βHSD and P450c17 were identified in the stromal cells or epithelial cells. The mRNA expression levels of LHR, SF-1, StAR, P450scc, P450c17, 3βHSD and Sterol Regulatory Element-Binding Protein 2 (Srebp2) in the prostate were remarkedly higher during the breeding period than those in the non-breeding period. In contrast, the mRNA expression levels of Melatonin Receptor 1a (Mtnr1a) and Melatonin Receptor 1b (Mtnr1b) were elevated during the non-breeding period. Consistently, the circulating LH and T as well as the prostatic T and DHT concentrations were remarkably higher in the breeding season than those of the non-breeding season, which were positively correlated with the seasonal changes of prostatic weight. Additionally, the transcriptomic study in the prostates identified that differentially expressed genes might be related to signal transduction and signaling receptor activity using GO analysis. The KEGG pathway enriched by differentially expressed genes detected to be involved in steroid biosynthesis, estrogen signaling pathway or steroidogenesis. Taken together, these findings suggested that the prostates of the wild ground squirrels potentially owned ability to synthesize steroid hormones de novo, and the steroid hormones might affect the prostatic functions of the wild ground squirrels via an autocrine or paracrine manner.