Intrauterine Wachstumsretardierung (IUGR) mit ARED-Flow in der Dopplersonographie der Arteria umbilicalis : molekulargenetische Analyse der Gene IGF-I und IGF-IR

Abstract

The objective of the present study was to evaluate a possible role of mutations of the genes IGF-I (Insulin-like Growth Factor-I) and IGF-IR (Insulin-like Growth Factor-I Receptor) in the pathogenesis of intrauterine growth retardation/ restriction (IUGR) with ARED (Absent or Reversed EndDiastolic)-flow in the Doppler ultrasonography of the A.umbilicalis. IUGR is caused by abnormal development of the placenta. The proliferation and differentiation of the villous trophoblast are predominantly controlled by growth factor IGF-I and its receptor IGF-IR. The functional IGF-I-system is also involved in the placental angiogenesis. Reduced activity of this system seems to be associated with an impaired proliferation of cytotrophoblastic cells and an inadequate placental angiogenesis, resulting in a postplacental hypoxia. The morphological changes of the placenta, as described above, are characteristic for pregnancies with IUGR and ARED-flow. In pregnancies with IUGR and PED (Preserved EndDiastolic)-flow in the presence of a bilateral abnormal uterine artery Doppler waveform (Notch), the placental histology shows a netlike arrangement of capillaries, forming multiply branched terminal villi (uteroplacental hypoxia). In the present study have been analyzed the genes encoding for IGF-I and IGF-IR in an IUGR/ARED-flow-group (19 mothers and their 19 fetuses) and an IUGR/PED-flow-group (14 mothers and their 14 fetuses). DNA was extracted from blood samples (mothers and alive fetuses) and paraffinblock samples (not-alive fetuses). Both genes were screened for genomic variants by single-strand conformation analysis (SSCP), restriction assays (RFLP) and direct sequencing. In the IGF-I-gene no variants could be identified in the study population. As for the IGF-IR-gene, five variants could be identified, three of them so far unknown: one in the 5´- and two in the 3´-untranslated region of the gene, as well as two polymorphisms that had already been described before in the literature: a silent mutation in exon 16 and a deletion in the 3´-untranslated region of the gene. The new polymorphisms were localized in the non-coding region of the IGF-IR-gene. Furthermore, all genomic variants were detected in similar frequencies in the patient-group and the control-group. Thus we conclude that the identified gene-polymorphisms do not play a relevant role in the aetiology of IUGR with ARED-flow