Fetal and Maternal Tissue Harvesting

At necropsy, fetal and maternal tissues were surgically removed. All necropsies were performed by a board-certified pathologist and two technicians. Hysterotomy was performed on the pregnant macaques under inhalation anesthesia, and the fetus, placenta, fetal membranes, umbilical cord, and amniotic fluid were collected for detailed tissue dissection post-fetal euthanasia with an overdose of sodium pentobarbital (≥120 mg/kg). Shortly after, the mother was euthanized with an overdose of sodium pentobarbital (≥120 mg/kg). Each tissue was grossly evaluated in situ, and then excised, with further dissection with separate forceps and razor blades for each tissue to minimize risks for cross-contamination. Tissues were collected snap-frozen in Dulbecco’s minimum essential medium (DMEM) and RNAlater and homogenized to a liquid state^{20 (link)} with glass beads (Fisher Scientific) or a 5 mm steel ball (Qiagen). If tissue remained after snap freezing and RNAlater archival, tissues were preserved in 10% neutral-buffered formalin and routinely paraffin-embedded and processed with hematoxylin and eosin (H&E) or as noted below.