63INTERFERON-TAU EXPRESSION FROM PRIMARY TROPHECTODERM OUTGROWTHS OF BOVINE BLASTOCYSTS: COMPARISON BETWEEN IVP, NT, AND PARTHENOGENIC EMBRYOS

Interferon-tau (IFN-tau) is expressed soon after bovine blastocyst formation and might be useful as a marker of appropriate biological function in embryos produced by nuclear transfer. To assess this possibility we have compared IFN-tau levels in the conditioned medium of primary trophectoderm cultures derived from IVP, nuclear transfer (NT), or parthenogenic bovine embryos. Embryos were produced from in vitro-matured cumulus-oocyte complexes processed from local slaughterhouse ovaries or obtained from Bomed, Inc. (Madison, WI, USA). In vitro fertilization, NT, and parthenogensis were as previously described (Talbot et al., 2000 Tissue and Cell, 32, 9–27) except that embryo culture was in G1/G2 medium in 5% oxygen (Lane et al., 2003 Theriogenology, 60, 407–419). Each 8–11-day embryo was cultured individually in a 4-well plate well (Nunc) with STO feeder cells using DMEM medium containing 10% fetal bovine serum as previously described (Talbot et al., 2000 Biol. Reprod. 62, 235–247). Any contaminating epiblast or endoderm was physically dissected and discarded so as to produce pure trophectoderm outgrowths. The success/failure ratio for colony formation was similar for IVP and NT embryos (IVP=155/29; NT=104/25), but was significantly different (P<0.05) for parthenogenic embryos (54/43). Trophectoderm colonies reached diameters of 1 to 1.5cm in 3–4wk, and, at this time, 72-h-conditioned cell culture medium was harvested, frozen, and measured for IFN-tau anti-viral activity as previously described (Talbot et al., 2000 Biol. Reprod. 62, 235–247). From 313 observations, IFN-tau production was analyzed as a two-factor mixed linear model. Differences in IFN-tau production by type of embryo were statistically significant (F=42.61; P<0.0001; df=2). Mean comparisons were done with Sidak adjusted P-values so that the experiment-wise error was 0.05. IFN-tau production means for IVP-, NT-, and parthenogenic-derived trophectoderm were 4311IUmL−1 (n=155), 626IUmL−1 (n=104), and 1595IUmL−1 (n=54), respectively. The results show that mean IFN-tau production from trophectoderm cultures derived from NT embryos is significantly reduced in comparison to IVP- and parthenogenote-derived cultures. Parthenogenote-derived cultures also produced significantly less IFN-tau than IVP embryos on average. IFN-tau production from trophectoderm outgrowths may be a useful measure of NT reprogramming success.

Growth hormone and parathyroid hormone stimulate IGFBP-3 in rat osteoblasts

Osteoblast-like cells prepared from calvaria of newborn rats produce insulin-like growth factor (IGF) I and several insulin-like growth factor binding proteins (IGFBPs) in vitro. Among the IGFBPs found in conditioned cell culture medium, IGFBP-3 is the most abundant. Intact IGFBP-3, as assessed by 125I-labeled IGF-II ligand blot analysis, is more abundant in culture media of cells exposed to growth hormone (GH) or to parathyroid hormone (PTH), both at 5 x 10(-9) mol/l, for 24 h. At the same time, concentrations of IGF-I are increased in media of cells exposed to PTH but not to GH, compared with hormone-free control cultures. IGFBP-3 mRNA is increased in osteoblasts exposed to PTH or to GH but not in response to 5 x 10(-9) mol/l IGF-I. PTH exerts a rapid (within 2 h) stimulatory effect on IGF-I and IGFBP-3 production, both at the message and peptide levels, whereas GH increases only IGFBP-3, both at the message and peptide levels (after 24 h). We conclude that IGF-I does not mediate increased IGFBP-3 production by rat osteoblasts in response to GH and PTH.