Changes in the Metabolic Footprint of Placental Explant-Conditioned Medium Cultured in Different Oxygen Tensions from Placentas of Small for Gestational Age and Normal Pregnancies

The figure shows the PC-CVA scores plot (using all the detected metabolite features) for a model built and cross-validated using the first 20 PC scores to discriminate between the six medium classes of interest. Circles represent 1% oxygen samples, squares represent 6% oxygen samples and triangles represent 20% oxygen samples. Open shapes represent control samples and closed shapes represent SGA samples at each oxygen tension. For clarity the placental biological replicates have been averaged. The major change in metabolic footprint is due to oxygen tension (CV1). CV2 reflects a change in footprint reflecting SGA phenotype across all O₂ tensions. The units of the x- and y-axis are arbitrary due to normalisation of the data. CV = canonical variate; PC-CVA = Principal Components-Canonical Variates Analysis; SGA = small for gestational age; inner circle = 90% CI of the population mean; outer circle = 90% CI of the population itself.

Venn diagram showing the distribution of the significant metabolite features at each oxygen tension. A total of 574 metabolite features showed significant difference between SGA and normal controls at one or more of the oxygen tensions (p < 0.05). At 6% O₂ 427 metabolite features were significantly different with a False Discovery Rate of 0.1. At 1% O₂, 160 metabolite features were significantly different (FDR = 0.4). At 20% O₂, 254 metabolite features were significantly different (FDR = 0.2). Of the 574 metabolite features, 52 metabolite features were significantly different at all oxygen tensions (9% of the 574 metabolites); 32 metabolite features were significant at both 1% and 6% O₂, but not 20% (6% of the 574); 124 were significant at both 6% and 20% O₂, but not 1% (22%); 7 were significant at both 1% and 20% O₂, but not 6% (1%).

(a) and (b) are biplots. Each point in the biplot represents one of the observed metabolite features. Each point’s co-ordinate location (x, y), is defined by the significance of the relative change in metabolite concentration combined with the mean direction of that change (x = control; y = SGA). In these biplots, points lying in zone A show a mean increase in metabolite level for SGA samples and a mean decrease in control samples; zone B show a mean increase in metabolite level for both SGA and control samples; zone C show a decrease in mean metabolite level for both SGA and control samples; zone D show a decrease in mean metabolite level for SGA samples and an increase for control samples. (a) Biplot of change in metabolites, significant at 6% O₂, when explants were cultured at 1% O₂. The triangles (n = 81, 50%) show significant change in metabolite level for SGA samples but no significant change for control samples and the squares (n = 16, 10%) show significant change in metabolite level for control samples but no significant change for SGA samples (P = 0.05). (b) Biplot of change in metabolites, significant at 6% O₂, when explants were cultured at 20% O₂. The triangles (n = 6, 4%) represent significant change in metabolite level for SGA samples but no significant change for control samples and the squares (n = 31, 19%) represent significant change in metabolite level for control samples but no significant change for SGA samples (P = 0.05). A circle indicates a metabolite which significantly changes in both the SGA and control groups. The triangles indicate metabolites that are significantly changed in SGA but not significantly changed in control, and the squares indicate metabolites that are significantly changed in control but not significantly changed in SGA. The crosses indicate no significant change in either the SGA or control samples.