Transcriptomic analysis defines gestation-specific programs of fetal liver maturation in premature sheep

Background: Fetal liver maturation is essential for postnatal metabolic, synthetic, detoxification, and immune function. Disruption of this process by preterm birth contributes to hypoglycemia, impaired detoxification, and immune immaturity. However, the transcriptional programs governing hepatic maturation during mid-to-late gestation remain incompletely defined. We addressed this gap using a translationally relevant ovine model. Methods: Bulk RNA sequencing was performed on ovine fetal livers collected at gestational days 100, 124, and 144 (term = 150). Differential expression analysis, gene set variation analysis (GSVA), and weighted gene co-expression network analysis (WGCNA) were integrated to characterize temporal pathway dynamics, transcriptional modules, and regulatory architecture. Results: Global transcriptomic profiles segregated clearly by gestational age. Advancing gestation was associated with a coordinated transition from proliferative and hematopoietic programs toward metabolic, biosynthetic, detoxification, and immune competence pathways. Late gestation showed increased activity of gluconeogenesis, fatty acid β-oxidation, bile acid metabolism, xenobiotic detoxification, the urea cycle, and complement/coagulation pathways, together with suppression of cell-cycle programs. WGCNA identified two major maturation-associated modules and highlighted conserved candidate regulators, including STAT3, HNF4G, CEBPB, KLF6, NR3C1, and RORA, linking metabolic reprogramming with stress-adaptive signaling. Conclusions: These findings define a systems-level transcriptomic reference of fetal liver maturation across gestation and provide a framework for investigating how perinatal conditions or therapeutic interventions may alter hepatic developmental trajectories, questions that are difficult to address directly in human fetuses due to limited access to fetal liver tissue.