Review: Toward an integrated evolutionary understanding of the mammalian placenta
PLACENTA
Authors: Wildman, D. E.
Abstract
The placenta is fundamentally important for the success of pregnancy. Disruptions outside the normal range for placental function can result in pregnancy failure and other complications. The anatomy of the placenta varies greatly across mammals, as do key parameters in pregnancy such as neonatal body mass, length of gestation and number of offspring per pregnancy. An accurate understanding of the evolution of the mammalian placenta will require at minimum the integration of anatomical, developmental, physiological, genetic, and epigenetic data. Currently available data suggest that the placenta is a dynamic organ that has evolved rapidly in a lineage specific manner. Examination of the placenta from the perspective of human evolution shows that many anatomical features of the human placenta are relatively conserved. Despite the anatomical conservation of the human placenta there are many recently evolved placenta-specific genes (e.g. CGB, LGALS13, GH2) that are important in the development and function of the human placenta. Other mammalian genomes have also evolved specific suites of placenta-expressed genes. For example, rodents have undergone expansions of the cathepsin and prolactin families, and artiodactyls have expanded their suite of pregnancy-associated glycoproteins. In addition to lineage specific birth and death of gene family members, the pattern of imprinted loci varies greatly among species. Taken together, these studies suggest that a strategy reliant upon the sampling of placentally expressed and imprinted genes from a phylogenetically diverse range of species is appropriate for unraveling the conserved and derived aspects of placental biology. (C) 2011 Published by IFPA and Elsevier Ltd.
Placental protein 13 (PP13) stimulates rat uterine vessels after slow subcutaneous administration
INTERNATIONAL JOURNAL OF WOMENS HEALTH
Authors: Drobnjak, Tijana; Jonsdottir, Anna Margret; Helgadottir, Helga; Runolfsdottir, Margret Soffia; Marei, Hamutal; Sammar, Marei; Osol, George; Mandala, Maurizio; Huppertz, Berthold; Gizurarson, Sveinbjorn
Abstract
Introduction: Reduced concentrations of placental protein 13 (PP13) during the first trimester of human pregnancy are associated with elevated risk for the subsequent development of preeclampsia, which is one of the deadliest obstetrical complications of pregnancy. Previous studies by our group have shown that PP13 lowers blood pressure in pregnant rats, increases the size and weight of pups and placentas, and induces vasodilation of resistance arteries through endothelial signaling pathways involving endothelial nitric oxid synthase and prostaglandin. Methods: In the present study, the effect of PP13 was investigated in nonpregnant female Sprague Dawley rats (n=27). Osmotic pumps were surgically implanted subcutaneously that released a constant dose of PP13 or saline over 7 days. Most animals were sacrificed 6 days after the end of PP13 release (on day 13), while some were sacrificed immediately at the end of day 7 (the last PP13 release day), to compare the short- and long-term impact of PP13 on vessels' growth and size. Results: The uterine vessels were significantly expanded in the group exposed to recombinant PP13 (rPP13) compared to the control (saline) group. Both veins and arteries were significantly expanded by rPP13 with a more pronounced effect after 13 days compared to the corresponding vessels after 7 days. Furthermore, the long-term effect of treatment by rPP13 was more pronounced in the veins compared to the corresponding arteries. The effect of a PP13 variant with a histidine-tag (His-PP13) remained the same between 7 and 13 days. Conclusion: In conclusion, PP13 might play a key role in the expansive remodeling of the uterine vessels, reflecting what would happen if the rat was pregnant, preparing the uterine vasculature for the increase in uteroplacental blood flow, which is necessary for normal pregnancy. We suggest that PP13 could act by NO signaling pathways, a hypothesis that requires future study.