Expression and cellular distribution of INHA and INHB before and after in vitro cultivation of porcine oocytes isolated from follicles of different size.

Cumulus-oocyte-complexes (COCs) were collected from small (<3 mm), medium (3-5 mm), and large (>5 mm) porcine follicles, and the INHA and INHB expression and cellular localization were studied. Developmentally competent (BCB+) COCs were cultured for 44 h. Samples of mRNA were isolated before and after in vitro maturation (IVM) from oocytes collected from follicles of different size for RQ-PCR assay. The INHA and INHB protein distribution within the oocytes was observed by confocal microscopy. INHA mRNA expression was increased in oocytes from large compared to medium and small follicles before IVM (P < 0.001), and to oocytes of small follicles after IVM (P < 0.001). The INHB expression was not different before IVM, but the IHNB mRNA level was gradually higher in oocytes from large follicles after IVM (P < 0.01). INHA was not differently expressed before IVM; however, in large follicle oocytes the protein was distributed in the peripheral area of the cytoplasm; in oocytes from small follicles it was in the entire cytoplasm. After IVM, INHA was strongly expressed in oocytes from small follicles and distributed particularly in the zona pellucida (ZP). Similarly and both before and after IVM, INHB protein was highly expressed in small follicle oocytes and within the cytoplasm. In summary, INHs can be recognized as a marker of porcine oocyte quality.