Telomere Length and Global DNA Methylation as Predictors of Pregnancy Outcome: Insights into Reproductive Medicine

Spontaneous pregnancy loss is a severe pathological condition influenced by several inherited and acquired factors such as genetics, environment, and stress conditions that can affect embryo implantation and development. Epigenetics, by modifying gene transcription, genomic stability, and telomere length, may also have a key role. In addition, pregnancy maintenance is also regulated by a controlled inflammation. We analysed a cohort of 179 women who underwent to pregnancy interruption within the third gestational month (spontaneous EPL, n=92 and volunteer VPI, n=87). LINE-1 methylation level (%), as surrogate of global DNA methylation, and telomere length (T/S), as biological age assessment, were performed after bisulfite conversion plus pyrosequencing, and realtime qPCR respectively. Cytokines levels (IL-6, IL-10, IL-17A, IL-23) were quantified by Luminex technology and MILLIPLEX-Analyst Software.Telomere length is a valid indicator of biological age and tends to shorten with aging, we therefore compared the T/S values in the two subgroups. EPL had telomere length significantly shorter than the VPI subgroup (EPL 323.4 ± 134.72 vs VPI 425.8 ± 268.24; P=0.0014). Following correlation analysis, we found that T/S values were similar considering slopes comparison (Pslope=0.8958) and Y-axis intercept significantly differed (r2EPL=0.0001587 vs r2VPI =0.0005965; Pintercept=0.0019). Moreover, methylation assessment ascribed to EPL subgroup a significant lower mean value (EPL 82.04 ± 3.63 vs VPI 85.28 ± 3.44; P<0.0001). To test whether telomere length was somehow dependent on global DNA methylation, we correlated T/S with LINE-1 and found that the variation in telomere length based on global DNA methylation in the two subgroups had similar slopes (Pslope=0.6782) and significantly different Y-axis intercept (r2EPL=0.004759 vs r2VPI =0.001896; Pintercept<0.0001). Finally, higher mean cytokines levels were found in the EPS subgroup (P<0.0001). Our results suggest that shorter telomeres, hypomethylation and higher inflammation status, as well as their mutual relationships, may be considered as predisposing factors for miscarriage serving in turn as possible predictive prognostic biomarkers.