Background: Maternal protein restriction causes sperm alterations in the offspring, most of which are associated with epididymal functions. Because fluid reabsorption/secretion dynamics in the epididymal environment play important roles in the process of sperm maturation and concentration, we investigated the effects of maternal protein restriction on the expression of aquaporins (AQP1 and AQP9), vascular endothelial growth factor (VEGFa), and its receptor VEGFr-2 in different stages of postnatal epididymal development. Methods: Pregnant rats were divided into groups that received normoprotein (17% protein) and low-protein diets (6% protein) during gestation and lactation. After weaning, male rats only received the standard diet and were euthanized at the predetermined ages of 21, 44 and 120 days. Results: Maternal protein restriction decreased AQP1 and AQP9 expression in the initial segment and caput epididymis compared to the increased expression of these proteins observed in the corpus and cauda at all ages. Although protein restriction reduced the microvasculature density (MVD) on postnatal day (PND) 21 and 44, the MVD was unaltered on PND 120. Conclusions: Maternal protein restriction changed the structure or function of the offspring’s epididymis, specifically by affecting fluid dynamics and vasculogenesis in important stages of epididymis development.

The maternal nutritional status is essential to the health and well-being of the fetus. Maternal protein restriction during the perinatal stage causes sperm alterations in the offspring that are associated with epididymal dysfunctions. Vascular endothelial growth factor (VEGF) and its receptor, VEGFr-2, as well as aquaporins (AQPs) are important regulators of angiogenesis and the epididymal microenvironment and are associated with male fertility. We investigated the effects of maternal protein restriction on epididymal angiogenesis and AQP expression in the early stages of postnatal epididymal development. Pregnant rats were divided into two experimental groups that received either a normoprotein (17% protein) or low-protein diet (6% protein) during gestation and lactation. At postnatal day (PND)7 and PND14, male offspring were euthanized, the epididymides were subjected to morphometric and microvascular density analyses and to VEGF-A, VEGF-r2, AQP1 and AQP9 expression analyses. The maternal low-protein diet decreased AQP9 and VEGFr-2 expression, decreased epididymal microvascularity and altered the morphometric features of the epididymal epithelium; no changes in AQP1 expression were observed at the beginning of postnatal epididymal development. Maternal protein restriction alters microvascularization and affects molecules involved in the epidydimal microenvironment, resulting in morphometric alterations related to a delay in the beginning of epididymis postnatal development. 2 of 18caused by embryonic and fetal development [11]. Epidemiological and experimental evidence has shown an association between low birth weight and male subfertility in humans [12]. Boeri et al. (2016) [13] observed a positive correlation between infertile adults born with a low birth weight. These adult males had alterations associated mainly with epididymal functions, such as reduced sperm motility, including asthenozoospermia (reduction or absence of sperm motility) and higher rates of teratozoospermia (alterations in sperm morphology that may lead to infertility). Of the fetal programming models for maternal nutrition, that of protein restriction in a diet offered to pregnant rats is one of the most frequently used, leading to increased risks of certain diseases or disorders later in life as cardiovascular and metabolic diseases [14,15].The protein restriction diet in pregnant rats has already been shown to be able to alter maternal metabolism, increasing maternal serum corticosterone, estradiol and testosterone concentrations. In addition, other studies observed alterations in seminiferous tubule organization and in epididymal functions, similar to those found in men with low birth weight. These alterations include reductions in sperm motility, sperm concentration and viability, in addition to morphological changes [16,17].In male embryos, the proximal region of the mesonephric tubules originates the mesonephric ducts or Wolffian ducts (WD) that eventually become the epididymis. During embryonic and postnatal development, these duct...