Differential expression of GDF9, TGFB1, TGFB2 and TGFB3 in porcine oocytes isolated from follicles of different size before and after culture in vitro.

The TGFB superfamily genes are involved in several important cell functions, including proliferation and differentiation, and the role of the expression of these genes in growth and development of theca and granulosa cells is well recognised. However, the dependence between the stage of oocyte maturation or follicular size and the expression of these genes in pigs is still not entirely known. This study was aimed at investigating the expression pattern of GDF9, TGFB1, TGFB2 and TGFB3 in porcine oocytes before and after in vitro maturation (IVM) as well as in oocytes collected from follicles of different sizes. RQ-PCR was performed to analyse the expression of GDF9, TGFB1, TGFB2 and TGFB3 in oocytes before and after IVM (oocytes cultured for 44 h in TCM-199), isolated from large (> 5 mm), medium (3-5 mm) and small (< 3 mm) follicles collected from ovaries of 28 puberal crossbred Landrace gilts after slaughter. We found an increased expression of both TGFB1 and TGFB2 in oocytes before IVM collected from large as compared to medium and small follicles (P < 0.05, P < 0.001, P < 0.01, P < 0.05, respectively). In these groups of oocytes we did not observe differences in GDF9 and TGFB3 mRNA levels. However, after IVM, GDF9 protein distribution in oocytes was significantly higher in large and medium follicles as compared to small ones (P < 0.01, P < 0.001, respectively). Moreover, an increased TGFB1, TGFB2 and TGFB3 proteins pattern was observed in oocytes of large compared to small follicles. The highest GDF9 and TGFB1 mRNA levels were found in oocytes after IVM compared to those before IVM. Based on our study we can suppose that the distribution pattern of TGFB superfamily genes is associated with the stage of maturation of porcine oocytes and the follicle size. Furthermore, GDF9 and TGFB1 may serve as molecular markers of the develop-mental potential of porcine oocytes. The confocal microscopic observation revealed that TGFB1 and TGFB3 were translocated between the zona and the cytoplasm of oocytes, depending on the stage of maturation and follicle size.