Transcriptomic Analysis of Equine Placenta Reveals Key Regulators and Pathways Involved in Ascending Placentitis

Placentitis was induced in six mares at approximately 290d of gestation (placentitis group), and six mares with gestationally age-matched (290 d) pregnancies did not receive any treatment (control group). For induction of placentitis in the former group, Streptococcus equi subsp. zooepidemicus was introduced intracervically. Overall design: Placental samples were collected from the caudal pole of the placenta from mares with experimentally induced placentitis (290 d GA, n =6) and normal pregnant mares (290 d GA, n=6). Total RNA was isolated from all samples using RNeasy Mini Kit (#74104; Qiagen), and DNA digestion was performed on-column using RNase-free DNase I (#79254: Qiagen), followed by cleanup procedures. All procedures were performed according to the manufacturer's instructions. After extraction, RNA purity was checked using the NanoPhotometer® spectrophotometer (IMPLEN, CA, USA). RNA integrity and quantitation were assessed using the RNA Nano 6000 Assay Kit of the Bioanalyzer 2100 system (Agilent Technologies, CA, USA). All samples had a 260/280 ratio >2.0 and RNA integrity number (RIN) > 8.0.