Immuno-epigenetic signature derived in saliva associates with the encephalopathy of prematurity and perinatal inflammatory disorders

Abstract

Background: Preterm birth is closely associated with a phenotype that includes brain dysmaturation and neurocognitive impairment, commonly termed Encephalopathy of Prematurity (EoP), of which systemic inflammation is considered a key driver. DNA methylation (DNAm) signatures of inflammation from peripheral blood associate with poor brain imaging outcomes in adult cohorts. However, the robustness of DNAm inflammatory scores in infancy, their relation to comorbidities of preterm birth characterised by inflammation, neonatal neuroimaging metrics of EoP, and saliva cross-tissue applicability are unknown. Methods: Using salivary DNAm from 258 neonates (n = 155 preterm, gestational age at birth 23.28 – 34.84 weeks, n = 103 term, gestational age at birth 37.00 – 42.14 weeks), we investigated the impact of a DNAm surrogate for C-reactive protein (DNAm CRP) on brain structure and other clinically defined inflammatory exposures. We assessed i) if DNAm CRP estimates varied between preterm infants at term equivalent age and term infants, ii) how DNAm CRP related to different types of inflammatory exposure (maternal, fetal and postnatal) and iii) whether elevated DNAm CRP associated with poorer measures of neonatal brain volume and white matter connectivity. Results: Higher DNAm CRP was linked to preterm status (-0.0107 ± 0.0008, compared with -0.0118 ± 0.0006 among term infants; p < 0.001), as well as perinatal inflammatory diseases, including histologic chorioamnionitis, sepsis, bronchopulmonary dysplasia, and necrotising enterocolitis (OR range |2.00 | to |4.71|, p < 0.01). Preterm infants with higher DNAm CRP scores had lower brain volume in deep grey matter, white matter, and hippocampi and amygdalae (β range |0.185| to |0.218|). No such associations were observed for term infants. Association magnitudes were largest for measures of white matter microstructure among preterms, where elevated epigenetic inflammation associated with poorer global measures of white matter integrity (β range |0.206| to |0.371|), independent of other confounding exposures. Conclusions: Epigenetic biomarkers of inflammation provide an index of innate immunity in relation to neonatal health. Such DNAm measures complement biological and clinical metrics when investigating the determinants of neurodevelopmental differences.

Blood-based epigenome-wide analyses of chronic low-grade inflammation across diverse population cohorts

“…However, neither measure associated with all-cause mortality, which is in contrast with our study 10 . A seven-CpG score derived from an earlier EWAS by Ligthart et al has also been associated with a wide range of neurocognitive health outcomes in adults and neonates 7–9,40–42 . These aggregate EWAS scores have shown promise in correlating with cardiometabolic disease risk and risk factors 6,7 .…”

Epigenetic scores of blood-based proteins as biomarkers of general cognitive function and brain health

“…This is important to understand because early life immune dysregulation contributes to some neurodevelopmental disorders. For example, a recent study found that a DNAm-based proxy of CRP correlates with inflammation burden and MRI markers of encephalopathy of prematurity after preterm birth (39). Another limitation of this study is the lack of replication for MRI findings and the consideration of EpiScores from a single time-point.…”

Epigenetic scores indicate differences in the proteome of preterm infants

“…In addition, we included EpiScores for growth and differentiation factor 15 (GDF15) and N-terminal-pro B-type natriuretic peptide (NTproBNP) [37], and CRP. The CRP EpiScore used was Barker et al ’s seven-CpG variation of Ligthart et al ’s CRP EpiScore [27,31], as this is known to correlate with birth GA, perinatal pro-inflammatory exposures, and neonatal brain development [32].…”

“…As well as having specific immunoregulatory roles, in the neonatal setting or relevant animal models, these proteins are associated with several comorbidities and developmental consequences of preterm birth. These include lung development and disease such as BPD [55][56][57][58][59][60][61][62][63][64][65][66][67], in utero and postnatal growth failure [68][69][70][71], HCA [7,72,73], patent ductus arteriosus [74][75][76][77], retinopathy of prematurity [78][79][80][81][82], NEC [83][84][85], hyperglycaemia [86], sepsis [85,[87][88][89][90], brain injury [32,[91][92][93][94], and neurodevelopmental outcomes [95][96][97][98]…”

“…The study has some limitations. The EpiScores used were developed in adult cohorts [26][27][28]37] and have not been validated in neonatal populations with neonatal protein levels, although we have previously established that neonatal DNAmCRP scores correlate with cumulative inflammatory exposures [32]. Further studies that evaluate serial blood protein levels with EpiScores could be informative but would need to rely on small volume samples taken during time of venepuncture for clinical reasons, given the practical and ethical challenges of serial venepuncture for research purposes in neonates.…”