Yaseen M A, Wrenzycki C, Herrmann D, Carnwath J W, Niemann H
Department of Biotechnology, Institut für Tierzucht und Tierverhalten, Mariensee, 31535 Neustadt, Germany.
Reproduction. 2001 Oct;122(4):601-10.
The aim of this study was to determine the relative abundance of mRNAs for the insulin-like growth factor I (IGF-I) and IGF-II ligands, and for the IGF receptors (IGF-IR and IGF-IIR) in in vitro preimplantation bovine embryos from the oocyte to the hatched blastocyst stage using two different culture systems: TCM-199 supplemented with oestrous cow serum, or synthetic oviduct fluid supplemented with polyvinyl alcohol. Development to the two- to four-cell stage and blastocyst stage was significantly higher (P < or = 0.05) in embryos cultured in TCM supplemented with oestrous cow serum than in those cultured in synthetic oviduct fluid supplemented with polyvinyl alcohol (61 and 25% versus 55 and 17%, respectively). A semi-quantitative RT-PCR assay did not detect IGF-I transcripts at any stage of preimplantation bovine development, including the hatched blastocyst stage. In both culture systems, IGF-IR, IGF-II and IGF-IIR were expressed throughout preimplantation development up to the hatched blastocyst stage in a varying pattern. The expression patterns of IGF-IR, IGF-II and IGF-IIR in embryos generated in the two culture systems were not significantly different, except at the expanded blastocyst stage, at which significantly higher amounts of IGF-IIR were observed in the TCM system than in the synthetic oviduct fluid system. These results indicate that transcripts of IGF-IR and IGF-IIR follow the standard pattern in which maternal stores of mRNA in the oocyte are slowly depleted up to the 16-cell stage and then re-established at the onset of embryonic expression of these genes. The lack of detectable IGF-I transcripts in the bovine embryo indicates a predominantly paracrine mode of action. The bovine embryo is capable of producing IGF-II, IGF-IIR and IGF-IR in large amounts, particularly after hatching, which may be important for the formation of the filamentous conceptus. Results indicate an autocrine mechanism for IGF-II and modulation of IGF family expression by culture conditions.
本研究的目的是使用两种不同的培养系统，确定从卵母细胞到孵化囊胚阶段的体外培养牛植入前胚胎中胰岛素样生长因子I（IGF-I）和IGF-II配体以及IGF受体（IGF-IR和IGF-IIR）的mRNA相对丰度：补充有发情母牛血清的TCM-199，或补充有聚乙烯醇的合成输卵管液。在补充有发情母牛血清的TCM中培养的胚胎发育到二细胞至四细胞阶段和囊胚阶段的比例显著高于（P≤0.05）在补充有聚乙烯醇的合成输卵管液中培养的胚胎（分别为61%和25%对55%和17%）。半定量RT-PCR分析在牛植入前发育的任何阶段，包括孵化囊胚阶段，均未检测到IGF-I转录本。在两种培养系统中，IGF-IR、IGF-II和IGF-IIR在整个植入前发育直至孵化囊胚阶段均有不同模式的表达。在两种培养系统中产生的胚胎中，IGF-IR、IGF-II和IGF-IIR的表达模式没有显著差异，除了在扩张囊胚阶段，此时在TCM系统中观察到的IGF-IIR量显著高于合成输卵管液系统。这些结果表明，IGF-IR和IGF-IIR的转录本遵循标准模式，即卵母细胞中mRNA的母体储存直到16细胞阶段缓慢消耗，然后在这些基因的胚胎表达开始时重新建立。牛胚胎中未检测到IGF-I转录本表明其主要为旁分泌作用模式。牛胚胎能够大量产生IGF-II、IGF-IIR和IGF-IR，尤其是在孵化后，这可能对丝状孕体的形成很重要。结果表明IGF-II存在自分泌机制以及培养条件对IGF家族表达的调节作用。
