Transcriptomic Modifications in Developmental Cardiopulmonary Adaptations to Chronic Hypoxia Using a Murine Model of Simulated High Altitude Exposure

Mechanisms driving adaptive developmental responses to chronic high altitude (HA) exposure are incompletely known. We developed a novel rat model mimicking the human condition of cardiopulmonary adaptation to HA starting at conception and spanning the in utero and post-natal timeframe. We assessed lung growth and cardiopulmonary structure and function, and performed transcriptome analyses to identify mechanisms facilitating developmental adaptations to chronic hypoxia. To generate the model, breeding pairs of Sprague-Dawley rats were exposed to hypobaric hypoxia (equivalent to 9,000 feet elevation). Mating, pregnancy and delivery occurred in hypoxic conditions. Six weeks postpartum, structural and functional data were collected in the offspring. RNAseq was performed on right ventricle (RV) and lung tissue. Age-matched breeding pairs and offspring under room air (RA) conditions served as controls. Hypoxic rats exhibited significantly lower body weights and higher hematocrit levels, alveolar volumes, pulmonary diffusion capacities, RV mass, RV systolic pressure as well as increased pulmonary artery remodeling. RNAseq analyses revealed multiple differentially expressed genes in lungs and RVs from hypoxic rats. While there was considerable similarity between hypoxic lungs and RVs compared to RA controls, several upstream regulators unique to lung or RV were identified. We noted a pattern of immune down-regulation and regulation patterns of immune and hormonal mediators similar to the genome from patients with pulmonary arterial hypertension. In summary, we developed a novel murine model of chronic hypoxia exposure that demonstrates functional and structural phenotypes similar to human adaptation. We identified transcriptomic alterations that suggest potential mechanisms for adaptation to chronic HA.

Keywords: RNAseq; hypoxia; lung growth; pulmonary hypertension; transcriptome.