Apoptosis in placental maturation of cows in different stages of pregnancy: Immunohistochemical and biochemical evidences

摘要

Apoptosis is important for placental homeostasis maintenance, and a misbalance in this process may compromise the success of pregnancy. The aim of this study is to evaluate apoptosis in bovine placental samples at different stages of pregnancy. Placentome samples from 15 healthy cows, at gestational ages of 4 (n=5), 6 (n=5) and 9 (n=5) months were collected and routinely processed for histological and immunohistochemical analysis, and for DNA isolation. Histopathology sections were stained with HE. Others were submitted to immunohistochemistry, using pro-apoptotic caspase-3 and Bax protein, and anti-apoptotic Bcl-2 specific antibodies. Isolated DNAs were processed for electrophoresis in agarose gel, for detection of internucleosomal fragmentation. Histomorphometry results demonstrated that apoptotic cells gradually increase with the advance of the gestation. Also, the DNA ladder pattern was observed in all groups. In addition, caspase-3, Bax and Bcl-2 were all expressed in the three different gestation periods. However, caspase-3 presented a higher expression in all groups, in comparison to Bcl-2 and Bax. These results confirm the importance of the apoptosis in the placental maturation. Also, these results indicated that caspase-3, Bcl-2 and Bax are involved in apoptotic activation mechanisms by mitochondrial intrinsic pathway during placental maturation, contributing for physiological cellularity and cellular turn over balance in bovine placenta. Index terms: Apoptosis, placenta, caspase 3, Bcl-2, bax, cattle.     INTRODUÇÃO Apoptose ou morte celular programada é um tipo de autodestruição celular dependente de energia e síntese protéica (Kerr & Searle 1972). Está relacionada com a homeostasia na manutenção adequada do tamanho dos tecidos, exercendo um papel oposto ao da mitose (Gerschenson & Rotello 1992, Kerr 1999). Desta forma, é um tipo de morte desejável, programada e seletiva, que envolve células isoladas sendo regulada intrínseca e extrinsecamente (Mccon