Placental endocannabinoid metabolism and gene expression gestational age-related alterations across preterm and term birth.

RESEARCH QUESTION: How does the placental endocannabinoid system (ECS) vary across gestation and in spontaneous preterm birth? DESIGN: Placental tissue was collected from 102 pregnancies from extremely preterm to very preterm (<32 weeks), moderate to late preterm (32-37 weeks) and term (≥37 weeks) deliveries. Ten ECS-related genes were measured by reverse transcription quantitative real-time PCR, and 20 endocannabinoid-related metabolites by targeted ultra-high performance liquid chromatography-mass spectrometry. Data analyses included univariate and multivariate statistics, linear regression and integrative hierarchical clustering of combined gene-metabolite datasets. RESULTS: Compared with term placentas, the expression of DAGLB and NAPEPLD was lower in both preterm groups (DAGLB, P < 0.001 for both; NAPEPLD, P = 0.035 for extremely to very preterm, P = 0.045 for moderate to late preterm). ABHD6 expression was lower in extremely to very preterm compared with term placentas (P = 0.010). CNR1 was higher in moderate to late preterm than term placentas (P = 0.009). PTGS2 expression was higher in extremely to very preterm than moderate to late preterm placentas (P = 0.046). Multivariate analyses of metabolites distinguished term from preterm groups, driven mainly by elevated values of monoacylglycerols in preterm placentas. Gestational age was inversely associated with monoacylglycerols (β approximately -0.131 to -0.16; R² approximately 0.49-0.65; P < 0.001 for all). N-Acylethanolamines (NAE) displayed weaker (NAE 14:0: β = -0.034, R2 = 0.18, P < 0.001; NAE 18:1: β = -0.058, R2 = 0.26, P < 0.001) or non-significant associations. Integrative clustering revealed three clusters of preterm placentas differing in gestational age, neonatal birthweight and maternal pregnancy weight gain. CONCLUSIONS: Placental ECS profiles vary significantly with gestational age. The differences observed in preterm placentas primarily reflect gestational maturation rather than distinct clinical phenotypes.