Elevated expression of four apolipoprotein genes during the 32-35 week gestation window in the human developing lung

BackgroundCo-expression of four apolipoproteins with a sex difference was observed in the mouse developing lung with an increase during the day of the surge of surfactant synthesis and a causal relationship was proposed.AimsTo determine whether these apolipoproteins and lipoprotein lipase (LPL) are expressed in the human fetal lung. To compare the distribution patterns of apoC-II and LPL proteins at different developmental ages.Study designReal-time PCR with RNA samples and immunohistochemistry with tissues from lungs of fetuses deceased between 19 and 40 weeks' pregnancy.ResultsElevated apolipoprotein A-I (apoA-I), apoA-II, apoC-II, and apoH expression was observed only during a short gestation time window from 32 to 35 weeks' gestation. LPL was expressed at relatively constant levels over gestation time. The gene encoding for the essential co-factor of LPL, apoC-II, was expressed at similar levels than LPL gene only during the 32-35 week gestation window. ApoC-II and LPL protein distribution vary according to gestation time, with obvious co-localization in capillaries at 32 weeks' gestation, but not in samples collected at 22-24 weeks' gestation.ConclusionsApoA-I, apoA-II, apoC-II, and apoH genes are expressed with a human-specific narrow peak of elevated expression in late gestation. Specific and developmental time-dependent distribution profiles were observed for apoC-II and LPL proteins. The 32-35 weeks' gestation window, where high levels of expression of apolipoproteins and co-localization of apoC-II and LPL protein were observed, correlates with the reported decrease in the incidence and severity of respiratory distress syndrome (RDS) consequently to the surge of surfactant synthesis.