Morphometric study of the porcine placental vascularization

Abstract

The early development in mammals is characterized by the contribution of nutrients from the maternal tissues through the placenta, which is in apposition with foetal membranes and the endometrium, allowing the physiological interchange between the embryos/foetuses and the mother. The aim of this work was to study the number of placental blood vessels and their vascular area through morphometric analyses and the haemotrophic diffusion distance in porcine placental tissues from early gestations, intermediates gestations, advanced gestations and term gestations. For those purposes, morphometric measurements, blood vessel quantification, high-resolution light microscopy and transmission electron microscopy were performed. The implementation of the high-resolution light microscopy allowed studying the placental vascular and tissue histoarchitecture with higher definition and resolution than using a conventional light microscopy. We highlight the close location of the subepithelial capillaries to the maternal/foetal interface as pregnancy progresses. We found statistically significant evidence to state that the area of blood vessels is dependent on the gestation period. In advanced gestations, the presence of numerous small blood vessels and its near location to foetal/maternal interface agree with the great remodelling reported in our previous studies. In conclusion, in gilts, given the type of non-invasive epithelial placentation, the new blood vessels generation and of haemotrophic diffusion distance reduction, determined in this report, assure the maternal/foetal haemotrophic exchange efficiency during gestation.

Placental vascularization in middle and late gestation in the pig

“…These results can be explained, in part, by the increase in the number of small vessels at late-middle gestation in the maternal side and by the increase in diameter and, consequently, in the vascular area, towards the end of gestation. These results are consistent with previous findings from our laboratory showing that the vascular area depends on the gestational period in pigs ( Cristofolini et al 2018 ). Indeed, Vonnahme et al (2001) have detected a slight decrease at day 44 in the number of vessels per unit area before increasing progressively from day 44 to 112 of gestation.…”

“…Until the end of pregnancy, at day 114 approximately, the size of the placenta stabilizes, and the fetuses grow exponentially ( Merkis et al 2005 , Guimarães et al 2017 , Cristofolini et al 2018 ). Previous work from our laboratory demonstrated that in advanced gestations, the new blood vessels formation and the reduction in the haemotrophic diffusion distance are involved in the maternal/fetal haemotrophic exchange efficiency ( Cristofolini et al 2018 ).…”

Dietary Amino Acid Supplementation and its Relationship with Placental and Fetal Growth in Pigs

“…The number of blood vessels declines whereas the vascular area increases, in early gestation (d 30-40), intermediate gestation (d 60-70) and at term (d 114) while in advanced gestation (d 90) predominate numerous blood vessels of smaller area. These observations are consistent with an exponential growth of the placenta up to (d 60-70) when it reaches a plateau; conversely, maximum fetal growth occurs, at an exponential rate, from (d 60) until the end of gestation (Cristofolini et al, 2018).…”

Vascular characterization and morphogenesis in porcine placenta at day 40 of gestation

“…During early gestation in pigs, significant morphological changes occur at the maternalchorioallantoic interface, as a greater increase in placenta weight occurs between 37 and 42 days of gestation (Wright et al, 2016). In previous morphometric studies, we have demonstrated a significant decrease in the haemotrophic diffusion distance between 25 and 30-40 days of gestation in the placental tissues of pigs (Cristofolini et al, 2018). Seo et al (2020) have determined that the mean blood vessel area increased between day 24 and day 35 of gestation in the placenta of pigs.…”