Fetal spina bifida associates with dysregulation in nutrient‐sensitive placental gene networks: Findings from a matched case–control study

Abstract

To improve outcomes in fetuses with spina bifida (SB), better understanding is needed of the molecular drivers of SB and its comorbidities. Pregnant people carrying a fetus with isolated SB (cases; n=12) or a fetus with no congenital anomalies (controls; n=21) were recruited at Mount Sinai Hospital, Toronto. Clinical data and placental samples were collected. Placental transcriptome was sequenced (Clariom DTM microarray) and a nutrient‐focused gene expression analysis pipeline was applied to determine whether fetal SB associates with placental dysfunction. Of the 391 differentially expressed genes (DEGs) in cases, 11% (n=42) had at least one nutrient cofactor, including B vitamins (n=7 genes), iron/heme (n=6), and zinc (n=11). Cases had dysregulation in genes not previously known to associate with SB, and in placental genes that have known links to SB but have not been previously identified in the placenta. Cases also had downregulated nutrient transport and upregulated branching angiogenesis and immune/inflammatory processes. Five nutrient‐dependent transcription regulators, collectively predicted to target 46% of DEGs in cases, were identified and were most commonly dependent on B vitamins (n=3) and zinc (n=2). Placental gene expression changes were most acute in cases with poor growth. Placentae from fetuses with SB have dysregulation in several gene networks, including those that are sensitive to multiple micronutrients beyond the well‐known folic acid. An improved understanding of placental phenotype in fetuses with SB may help identify novel mechanisms associated with comorbidities in fetuses with SB, and reveal new targets to improve fetal outcomes in this population.

Altered placental immune cell composition and gene expression with isolated fetal spina bifida

“…However, it is likely that the SB cases in our cohort were not folateresponsive NTDs, given that folate deficiency is rare in the region the study took place 36 and that all mothers in the cohort were taking prenatal vitamins. 21 The lack of differences in folate transporter immunolabeling that we report is consistent with transcript-level data for expression of FRα, PCFT, and RFC that we have previously reported for this cohort. 21 It is possible that the suboptimal growth observed in ∼50% of the cases in this cohort was, in part, driven by dysfunction in other nutrient-related placental processes, such as lipid metabolism and amino acid transport, 21 and this is an area requiring further study.…”

“…Further, we previously reported that cases in this cohort had upregulated expression of five genes known to be expressed by HBCs, including genes involved in inflammatory response regulation, which is consistent with an overall enhancement of HBC function in cases. 21 Given that HBCs regulate placental angiogenesis, and changes in HBC number or polarization may alter angiogenesis, 33 an altered HBC phenotype may contribute to placental villous maldevelopment observed in these cases. 17 Future studies should consider a deeper phenotyping of the role of regulatory (M2) HBC subtypes (M2a, M2b, M2c, and M2d 38 ) in placental physiology in both healthy fetuses, and those with isolated SB, to better delineate how HBC composition may relate to placental villous maldevelopment in fetuses with isolated NTDs.…”

“…Baseline characteristics for PT-controls (n = 12), controls (n = 10), and cases (n = 12) have been previously described and the groups were highly similar. 21 This is likely a folate replete population, given that all mothers in the case and control groups reported taking prenatal vitamins and that in Canada, fortification of white flour, pasta and corn meal with folic acid is mandatory. 21…”

“…21 This is likely a folate replete population, given that all mothers in the case and control groups reported taking prenatal vitamins and that in Canada, fortification of white flour, pasta and corn meal with folic acid is mandatory. 21…”

“…This study population has been previously described. 21 Pregnant people carrying a fetus were recruited at approximately 25 weeks' gestation at Mount Sinai Hospital, Toronto. Controls were singleton pregnancies without fetal anomalies.…”