Cellular and immune adaptations at the maternal-fetal interface in bats.

Bats experience extreme physiological conditions rarely encountered by other mammals, including prolonged gestation relative to other small species, high metabolic demands, temperature fluctuations during flight, and continual microbial exposure. These traits make them a powerful model for understanding placental adaptation during pregnancy. Here, we define the cellular and molecular architecture of the Jamaican fruit bat (Artibeus jamaicensis) placenta using single-nucleus RNA sequencing and tissue-derived organoid models. This analysis reveals diverse trophoblast, stromal, and immune populations with bat-specific transcriptional programs, including fibroblasts with hybrid adventitial and neuronal signatures and macrophages expressing pregnancy-associated molecules typically restricted to trophoblasts. Comparative analyses with human and mouse placentas uncover both conserved and lineage-specific features. Functional assays demonstrate that bat trophoblast organoids maintain high basal antiviral gene expression but limited inducibility following viral stimulation, revealing a unique strategy of immune vigilance without inflammation at the maternal-fetal barrier that may underpin reproductive success under physiological extremes.