TGFα and EGFR in ovine preimplantation embryos and effects on development

The present study aimed to assess location and relative amounts of transforming growth factor alpha (TGFα) and its receptor (EGFR) in ovine oocytes and preimplantation embryos by using immunohistochemical technique that was graded on a relative scale of 0–3, with 0 representing absence of staining, and 3 exhibiting prominent staining, and to evaluate the effects of TGFα/EGF on in vitro development of preimplantation embryos by adding different concentrations of EGF and TGFα to culture medium. The results showed that EGFR was abundant in cell plasma membranes in immature and mature oocytes, cumulus cells of immature cumulus-oocyte complexes (COC), fertilized oocytes and at different stages of embryo development. However, the relative amounts in inner cell mass (ICM) (1+) was less than that in trophectoderm (TE) cells (2+) at the blastocysts stage. The staining pattern for TGFα was a similar to EGFR. However, the staining for TGFα slightly increased in the fertilized oocytes (1–2+) as compared to immature and mature oocytes (1+). TGFα was mainly detected in the cytoplasm close to the membrane in both ICM and trophectoderm (TE) cells. The developmental rate of 8-cell stage embryos cultured with 5 ng/ml TGFα was increased as compared to other treatments (P < 0.05). There was no significant difference in the rate of development of blastocysts cultured with 5 ng/ml TGFα, 20 ng/ml EGF, 20 ng/ml EGF + 5 ng/ml TGFα or the control treatment (P > 0.05). In addition, there was no significant difference in the number of cells in blastocyst stage as compared with different treatments (P > 0.05). However, TGFα alone enhanced cell survival rated (P < 0.01) and reduced apoptosis. We concluded that TGFα can improve development of ovine preimplantation embryos at the 8-cell and blastocyst stages in vitro.