Changes in gene expression in rat placenta at gestational day 16.5 in response to hyperglycemia

Gestational diabetes mellitus (GDM) is a serious pregnancy complication. Hyperglycemia induces abnormal placental development and function. However, the mechanism is unclear. Previous research showed streptozocin (STZ) injection sustained hyperglycemia throughout pregnancy in rodents. Our current results showed that the placenta from hyperglycemic STZ-treated rats was about 20% heavier than that of controls. The relative thickness of each layer of the placenta was also significantly different on gestational day (GD) 16.5. Gene expression was analyzed by RNA sequencing to explore reasons for the abnormal placenta. In total, 2100 differential expressed genes (DEGs), including 1327 up-regulated and 773 down-regulated genes, were identified. Gene ontogeny (GO) analysis revealed DEGs involved in developmental process, growth, metabolic process, cell junction, molecular transducer activity and signaling. By KEGG analysis, DEGs were mainly related to the endocrine system, development, signal transduction and cell growth and death. The KEGG results were partly consistent with GO results, with DEGs mainly focused on biochemical signal pathways such as cell growth and death (e.g., Abl1, Bbc3 and Camk2d), and signal transduction (e.g., Abl1, Ceacam1 and Arnt). These genes may play a dominant role in abnormal cell proliferation and signaling disorders. These results suggest that DEGs play a role in diabetic-induced placental abnormalities. One or more of these DEGs may be involved in the etiology of placental weight increase caused by hyperglycemia.