The Effects Of Chronic Intermittent Hypoxia During Pregnancy On Gene Expression Profile And Transforming Growth Factor-β Pathway In Carotid Arteries Of Rabbit Offspring

Objective To investigate the effects of chronic intermittent hypoxia (CIH) during mid-late gestation on gene expression and transforming growth factor-β(TGF-β) pathway in carotid arteries of rabbit offspring, and the effects of CIH during pregnancy on the development of atherosclerosis (AS) in adult rabbit offspring and underlying molecular mechanisms.Methods Thirty-six pregnant New Zealand White rabbits (term = 30+/-1 days) were randomly assigned to normoxic control (NC, 21% O2, n = 18), or chronic intermittent hypoxia (CIH, 12% O2, n = 18) during day 10-29 of pregnancy. At end of pregnancy (29 days gestation), NC and CIH fetuses were removed via a hysterotomy from 5 pregnant rabbits in each group. Carotid arteries were obtained from two male fetuses from each litter, from which total RNA were extracted for determination of gene expression profile. Real-time PCR was then performed to verify the microarray results. The remaining pregnant rabbits were allowed to have spontaneous deliveries, from which two male offspring in each litter were selected randomly and breast-fed for six weeks, then switched to standard lab rabbit chow until 12-wk-old, and again randomly separated into high-fat diet and normal diet respectively. Thus 4 groups were generated: maternal normoxic control (MNC, n = 5), chronic intermittent maternal hypoxia plus normal diet (CIMH & ND, n = 5), maternal normoxic control plus high fat diet (MNC & HFD, n = 5 ), chronic intermittent maternal hypoxia plus high fat diet (CIMH & HFD, n = 5). The expressions of TGF-βand its downstream genes in carotid arteries were detected with PCR and Western blot for mRNA and protein levels respectively from fetuses and 2, 6, 12 and 24-wk-old MNC (n = 5) and CIMH (n = 5) rabbit offspring, as well as the morphological changes of carotid arteries of the 24-wk-old MNC (n = 5) and CIMH (n = 5) rabbit offspring.Results CIH during mid-late gestation resulted in fetal hypoxemia, intrauterine growth restriction, disproportion of fetal organ size, and altered gene expression in fetal carotid arteries, including decreased expression of genes involving cell signaling, communication and development. CIH significantly (p﹤0.05 or p﹤0.01) increased TGF-βand its downstream gene mRNA and protein concentrations in fetal carotid arteries, which could also be observed at 2-wk-old rabbit offspring (p﹤0.05), but diminished by 6-wk-old, and decreased at 12 and 24-wk-old rabbit offspring (p﹤0.05). CIH led to characteristic histological changes of the early stage AS at 24 -wk-old rabbit offspring, which could be synergistic with hyperlipemia to induce atherosclerotic plaque formation.Conclusions CIH during mid-late gestation could change gene expression in fetal carotid arteries, including down-regulated genes involving in cell signaling, communication and development. CIH during pregnancy could be one of the independent risk factors for inducing characteristic histological changes of the early stage AS at 24-wk-old rabbit offspring, which could be synergistic with hyperlipemia. One of the possible molecular mechanisms involved in the development of AS is that CIH during mid-late gestation regulates the expression of TGF-βand its downstream genes of rabbit offspring artery.