71 WHAT IS THE UTERINE RESPONSE IN A CLONED BOVINE PREGNANCY?

Abstract

Bovine has a synepitheliochorial placenta and characteristically there is no invasion of the trophoblast, but there is migration of the binucleate trophoblast giant cells into the maternal endometrium. The feto-maternal interface occurs in placentome where a tridimensional organization permits interactions between maternal epithelium and trophoblast, and in the intercaruncular area it is possible to observe a few mini-placentomes and the uterine glands opening. The objective of the present investigation was to study the morphological aspects of the uterus in bovine that had a cloned cattle gestations to understand the differences with natural gestation. The uterus and fetal membranes from natural and cloned cattle gestations were collected, fixed in 10% formaldehyde, processed, and stained for light microscopy and immunohistochemistry. The morphological differences observed in the surrogate uterus were: extensive areas without placentome, hemorrhagic uterine areas, caruncular fusion giving a reduced number of caruncules, increase in size and weight (megacaruncules), and a significant number of mini-caruncules giving miniplacentomes (diameter < 1 cm). In particular the mini-placentome showed functional trophoblastic cells with PAS+ granules in the binucleate trophoblast giant cells and an intense subepithelial capillary organization in maternal and fetal sides. The normal and clone placentomal cell populations were analyzed throughout pregnancy. The population of tetraploid and diploid trophoblastic cells was stained; detached cell cycle and DNA content was measured in FL2 using a FACscalibur flow cytometric system. We determined the percentage of cells in apoptosis (sub-G1), quiescent cells (G0/G1), synthesis (S), and proliferative cells (G2/M) with the aid of ModFit software. In addition, a cell cycle differential analysis was performed, and the tetraploid population presented statistical differences in cell cycle phases and populations relative to the apoptosis rate for the first (7.5 ± 3.1%), second (15.2 ± 5.0%) and third (17.3 ± 4.3%) trimesters. The number of apoptotic cells increased significantly during pregnancy stages. The results showed that first trimester presented the majority of its cells in the G0-G1 phase, starting the cell cycle. On the other hand, the second and third trimesters presented the majority of their cells in the G2-M phase, ending the cell cycle. The relationship between cell cycle phases/rate of apoptosis in mononucleate cells, days of normal and cloned pregnancy, the number of binucleate cells, and their metabolic activity as well as their developmental kinetics could be important data in several studies that involve placental development in natural pregnancy or that derived from laboratory-manipulated embryos.

This work was supported by FAPESP and CNPq.