Differences in gene expression dependent on sampling site in placental tissue of fetuses with intrauterine growth restriction

Relative gene expression in samples taken from different areas of IUGR and AGA placentas. Only in placental intermediate samples, there is a significant difference between IUGR (n=22) and AGA (n=19) infants in IGFBP-1 (p=0.01, Mann–Whitney test), prolactin (p=0.04, Mann–Whitney test), CRH (p=0.01, unpaired t-test) and leptin (p=0.04, Mann–Whitney test) mRNA expression Except for leptin (p=0.03, unpaired t-test), no significant difference was found for IGFBP-1 (p=0.56, Mann–Whitney test), prolactin (p=0.62, Mann–Whitney test) and CRH (p=0.10, Mann–Whitney test) mRNA expression, when placental peripheral samples were analyzed. Considering the proximal placental portion, there is no difference in the relative mRNA expression of IGFBP-1 (p=0.09, unpaired t-test), prolactin (p=24, unpaired t-test), CRH (p=0.90, unpaired t-test) and leptin (p=0.50, Mann–Whitney test) between IUGR and AGA placentas. Comparing the relative expression between different sampling sites, there is a non-significant trend towards higher gene expression levels at the placental periphery compared to the intermediate portion of IUGR placentas (IGFBP-1: p=0.92, Mann–Whitney test; prolactin: p=0.99, Mann–Whitney test; CRH: p=0.21, Mann–Whitney test; leptin: p=0.13, unpaired t-test).In the proximal placental part, gene expression is significantly different for IGFBP-1 (highest expression, compared to the intermediate (p=0.001, Mann–Whitney test) and peripheral area (p=0.005, Mann–Whitney test)) and for leptin (lowest expression, compared to the intermediate (p=0.03, unpaired t-test) and peripheral area (p=0.03, unpaired t-test)). In AGA placentas; mRNA expression of IGFBP-1 (p=0.47, Mann–Whitney test), prolactin (p=0.41, Mann–Whitney test), CRH (p=0.80, unpaired t-test), and leptin (p=0.75, Mann–Whitney test) is increased in samples taken from the peripheral area compared to the intermediate portion of the placenta without reaching statistical significance. Gene expression of IGFBP-1 is highest in the proximal placental area (versus intermediate area: p<0.0001, Mann–Whitney test). Leptin mRNA is significantly lower in the proximal compared to the intermediate (p=0.003, Mann–Whitney test) and peripheral (p=0.01, Mann–Whitney test) placental site, like in IUGR placentas. Gene expression is related to the housekeeping gene hypoxanthine guanine phosphoribosyl transferase (HPRT). The lines show the mean±SEM. *significant.

Absolute expression of housekeeping genes and genes of interest in samples taken from different areas of IUGR and AGA placentas. In addition to IGFBP-1, prolactin, CRH and leptin, the two housekeeping genes HPRT and β2-MG are regulated in their expression dependent on sampling site. The lines show the mean±SEM. *significant.

Comparison between IUGR and SGA placentas: Absolute expression of housekeeping genes and of Prolactin and of CRH in samples of different placental areas. When comparing the pure expression data between IUGR (n=22) and a subgroup of SGA (n=10) placentas, there are significant differences in gene expression dependent on sampling site, even within a single placenta. The lines show the mean±SEM. *significant.