Comparison Between Two Methodologies of Sample Preservation for RNA Extraction in Naturally Delivered Ovine Placenta

Placental samples for RNA extraction are collected via non-recovery (euthanasia) or invasive (surgery) methods in small ruminants, such as sheep. Alternatively, delivered placentas could be used, but the feasibility of obtaining high-quality RNA from this tissue is unknown in sheep. We aimed to evaluate the possibility of extracting RNA from naturally delivered ovine placenta, comparing two preservation methods. Twenty-seven single-pregnant sheep were monitored 24/7 from gestational day 140 to parturition. Tissue was collected after placental delivery, preserved using snap frozen (SF, n = 27) and RNAlater^® (LTR, n = 27) techniques, and processed for RNA extraction using a commercial kit. RNA concentration (ng/µL), A260/280, and RNA quality number (RQN) were measured. Concentration was higher (p < 0.001) in LTR (70.39 ± 6.3) than in SF (49.77 ± 10.5), A260/280 was higher (p = 0.045) in SF (2.06 ± 0.01) than in LTR (2.03 ± 0.01), and RQN was higher (p < 0.0001) in SF (6.81 ± 0.24) than in LTR (2.84 ± 0.24) samples. Timing of placental delivery did not affect the evaluated indicators. Results indicate that extracting high-quality RNA from delivered placentas preserved via the snap-frozen technique is possible, supporting a method that aligns with the refinement principle of animals used in research.