Lung collapse and respiratory distress in neonatal cloned cows is caused by surfactant homeostasis disorders

Respiratory distress is one of the major causes of the high mortality rate in neonatal cloned animals. Although some therapeutic methods have been used to improve the survival of cloned neonatal animals, the mechanisms of their neonatal respiratory distress lacked thorough investigation. Pathological analyses including necropsy and histology were implemented to determine the precise disease phenotypes, by which not fully dilated lungs, alveolar collapse and thickened alveolar walls were detected in neonatal cloned cows dying of respiratory distress compared to naturally conceived neonatal cows. In addition, we compared mRNA expression profiles between the two groups and differentially expressed genes (DEGs) have been achieved. Based on DEGs, GO and KEGG pathway enrichment analyses were performed, which showed that processes and pathways associated with surfactant homeostasis were significantly enriched between the two groups (p < 0.05). Gene expression in eight age-matched newborn cows, including four cloned cows that died of respiratory failure within 4 days of birth and were slaughtered immediately after death, and four normal healthy neonatal cows as the control group, which were also slaughtered 4 days after birth.