Assessment and distribution of apoptosis in immature cumulus oocyte complexes in sows

TELLO, MF.; LORENZO, MS.; MARURI, A.; CASIRÓ, S.; CETICA, PD.; GAMBAROTTA, MC.; LOMBARDO, DM.

Buenos Aires

Jornada; III Jornadas Internacionales del Instituto de Investigación y Tecnología en Reproducción Animal – INITRA; 2012

Instituto de Investigación y Tecnología en Reproducción Animal - INITRA. Facultad de Ciencias Veterinarias. UBA

The oocyte quality assessment and its connection with the presence of apoptosis has become greatly relevant over the past few years. The selection of high quality oocytes is key to succeeding in the production of in vitro embryos. However, the issue raises a number of controversies. This study aimed at assessing the presence and distribution of apoptosis in Cumulus - Oocyte Complexes (COCs) in sows and their relation to morphology. COCs were classified into six categories (A1, A2, B1, B2, C, D) under a stereoscopic microscope based on their morphology. For the evaluation of early apoptosis in each category the staining of Annexin-V was performed. The percentage of positive oocytes and the percentage of positive cumulus cells inside these ranges [0-25%);[25-50%);[50-75%);[75-100%] was obtained. For the evaluation of late apoptosis the technique was the TUNEL assay. It was observed that the percentage of COCs in each category is variable. Both early and late apoptosis were found in cumulus cells but only early apoptosis was found in oocytes. While there was an increase in apoptosis related to the declining quality evaluated morphologically, the increase is not consistent with the categories into which COCs were classified. Both oocytes and cumulus dead cells were found, irrespective of the COCs morphological characteristics or the category to which they belong. Based on the findings of apoptosis assessment, there arise the possibility of modifying certain selection/classification parameters in order to accelerate the finding of appropriate COCs for in vitro maturation (IVM) and in vitro fertilization (IVF). However, the morphological evaluation of COCs under a stereoscopic microscope by itself does not allow for a selection of COCs with no damage and no apoptosis. For Annexin-V, Chi square Test, test of Independence and Regression analysis were performed. TUNEL assay was analysis using no parametric ANOVA and Regression analysis. Differences were considered significant when P<0.01.