Seasonal vascular  plasticity in the mediobasal hypothalamus of the adult ewe

AbstractSheep, 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 do main 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 ...
Source: Histochemistry and Cell Biology - Category: Biomedical Science Source Type: research