Exploratory small RNA sequencing of human placental miRNAs identifies candidates associated with congenital transmission of Trypanosoma cruzi

Background Congenital transmission remains a major source of new Chagas disease cases, yet the underlying molecular mechanisms remain poorly understood. This exploratory study aimed to identify human placental microRNAs (miRNAs) associated with congenital transmission of Trypanosoma cruzi . Methods Placental samples from T. cruzi -infected mothers were classified according to congenital transmission status. Small RNA sequencing was performed on 31 placental samples, including 13 from transmitting mothers and 18 from non-transmitting mothers. Differential miRNA expression was assessed using DESeq2 with Benjamini-Hochberg false discovery rate correction. Candidate miRNAs were selected based on magnitude and significance of differential expression, or concordance with prior evidence from placental T. cruzi infection models. Selected candidates were subsequently analyzed by RT-qPCR in 15 placental samples, including 5 from transmitting mothers and 10 from non-transmitting mothers. Results Small RNA sequencing analysis identified hsa-miR-155-5p as the only significantly upregulated miRNA in placentas from transmitting mothers compared with placentas from non-transmitting mothers (log ₂ fold change = 1.26; adjusted p-value = 0.024); however, RT-qPCR assessment failed to confirm it at a significant level (log ₂ fold change = 0.57, 1.48-fold difference; p-value = 0.426). Other miRNAs, hsa-miR-193a-5p and hsa-miR-187-3p, showed higher relative expression in transmitting mothers, with estimated log₂ fold changes of 2.31 and 1.53, respectively (p = 0.032 and p = 0.043). hsa-miR-526b-3p showed a modest decrease in relative expression in transmitting mothers (log₂ fold change = -0.46; p = 0.043). Conclusion Placental miRNA expression profiling of naturally infected mothers identified miRNA candidates potentially relevant to congenital transmission of T. cruzi . Given the capacity of miRNAs to regulate broad gene expression networks that influence placental biology, these results underscore the need for transcriptomic and functional studies to elucidate their regulatory relevance during T. infection and evaluate their potential as biomarkers for congenital transmission risk.