Targeted Gene Arrays across the Severely-Discordant growth Monochorionic Twin Placenta: Implications for Angiogenesis and Metabolic Programming

Ziel: To explore angiogenesis and metabolic gene expression pathways in severe discordant monochorionic (MC) IUGR that may be subject to epigenetic regulation.

Methodik: We studied 10 severely growth-discordant twins (birth weight difference ≥ 25%) without twin-twin-transfusion syndrome (TTTS). Growth discordant twin placentas were phenotyped by histology, demonstrating distal villous hypoplasia or immaturity on the IUGR side. Two random and unbiased snap frozen placental samples were collected at time of delivery from each twin. Placental mRNA expression of 88 angiogenesis related genes were measured by PCR array. Enzyme-linked immuno-sorbent assay (ELISA) and immuno-histochemistry for leptin (Ob20) were used to confirm PCR results. EpiTYPTER for DNA methylation is used to determine methylation ratios for the known CpG-rich sites within the proximal leptin promoter region.

Ergebnis: The PCR array analysis showed significant mRNA up-regulation in the IUGR side for several genes, such as leptin (24.6 fold, p=0.045), Flt1 (fms-like tyrosine kinase 1, 2.4 fold, p=0.004) and Eng (endoglin, 1.86 fold up-regulated, p=0.049). None of the other 84 angiogenesis related genes showed significant differences using the ΔΔCt comparison method. ELISA confirmed significantly increased leptin protein expression in nine of ten twin pairs in the IUGR twins as compared to their co-twins (49.22 vs. 11.03 pg/mL, p=0.0487). Pholsphorylated leptin receptor expression is currently assessed by Western blot and epigenetic regulation of leptin by targeted PCR for bisulphate-converted DNA.

Schlussfolgerung: The IUGR MC twin placenta up-regulates Flt1 and Eng mRNA that may be associated with the villous pathology. The substantial up-regulation of leptin mRNA may be epigenetically conferred and relevant to the post-natal risk of metabolic syndrome in IUGR offspring. MC discordant IUGR twins offer unique insights into the epigenetic basis of perinatal programming.