COEXPRESSION OF TRANSFORMING-GROWTH-FACTOR-BETA AND INTERFERON-TAU DURING PERIIMPLANTATION PERIOD IN THE EWE

The transforming growth factor beta (TGF beta) family is known to cont rol cell migration, growth, differentiation, function and regulation o f extracellular matrix, all of which are required for the process of i mplantation. Expression of TGF beta by the conceptus and endometrium w as studied during the period of implantation in the ewe. A total of th irty-four ewes were hysterectomized on day 12, 14, 16, 18 or 20 of pre gnancy (day 0 = day of estrus). Conceptus (200 mg wet weight) and endo metrial (300 mg wet weight) tissues were cultured in vitro in 7 and 10 mi Eagle's minimal essential medium, respectively. The culture media were subjected to a bioassay to determine concentrations of TGF beta. Conceptus culture media (CCM) were also analyzed for contents of ovine interferon-tau (oIFN tau), low molecular weight acidic protein, produ ced by the trophectoderm between days 8 and 21 of pregnancy. Whole ute ri including conceptus(es) and conceptuses (day 16) only were fixed an d subjected to immunohistochemical and in situ hybridization studies. Levels of oIFN tau produced by conceptuses were the highest on day 16 at 4.4 mu g/ml. Concentrations of TGF beta in day 12, 14, 16, 18 and 2 0 CCM were 38 +/- 19, 102 +/- 56, 862 +/- 152, 728 +/- 191 and 336 +/- 106 pg/ml, respectively, and approximately 90% of TGF beta activity i n CCM was due to TGF beta 1 whereas less than 10% was due to TGF beta 3 based on neutralization with TGF beta subtype-specific antibodies. I mmunohistochemical studies revealed that day 16 conceptuses displayed major staining for TGF beta 1, no beta 2 staining and minor staining f or beta 3. In situ hybridization studies also revealed that day 16 tro phectoderm possessed most TGF beta 1 mRNA while day 14 trophectoderm a nd day 20 chorion/amnion displayed weaker staining for TGF beta 1 mRNA . TGF beta in day 12, 14, 16, 18 and day 20 endometrial culture media was 156 +/- 37, 129 +/- 33, 49 +/- 22, 62 +/- 23 and 179 +/- 40 pg/ml, respectively, and approximately 65% and 35% of the activities were du e to TGF beta 1 and beta 2, respectively. These results indicate that TGF beta production by the conceptus coincides with the time when oIFN tau production starts to decline. These observations support the post ulate that TGF beta may play an important role in implantation in the ovine species.