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

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 vascular plasticity in the mediobasal hypothalamus of the adult ewe

Sheep, like most seasonal mammals, exhibit a cyclic adaptive reproductive physiology that allows ewes to give birth to their progeny during the spring when environmental conditions are favorable to their survival. This process relies on the detection of day length (or photoperiod) and is associated with profound changes in cellular plasticity and gene expression in the hypothalamic-pituitary-gonadal axis, mechanisms that are suggested to participate in the seasonal adaptation of neuroendocrine circuits. Recently, pituitary vascular growth has been proposed as a seasonally regulated process in which the vascular endothelial growth factor A (VEGFA), a well-known angiogenic cytokine, is suspected to play a crucial role. However, whether this mechanism is restricted to the pituitary gland or also occurs in the mediobasal hypothalamus (MBH), a crucial contributor to the control of the reproductive function, remains unexplored. Using newly developed image analysis tools, we showed that the arcuate nucleus (ARH) of the MBH exhibits an enhanced vascular density during the long photoperiod or non-breeding season, associated with higher expression of VEGFA. In the median eminence (ME), a structure connecting the MBH to the pituitary gland, higher VEGFA, kinase insert domain receptor (KDR/VEGFR2) and plasmalemma vesicle-associated protein (PLVAP) gene expressions were detected during the long photoperiod. We also found that VEGFA and its receptor, VEGFR2, are expressed by neurons and tanycytes in both the ARH and ME. Altogether, these data show variations in the MBH vasculature according to seasons potentially through a VEGFA-dependent pathway, paving the way for future studies aiming to decipher the role of these changes in the hypothalamic control of seasonal reproduction.