Necrotizing enterocolitis (NEC) is an acute gut inflammatory disorder that mainly affects preterm neonates. A large proportion of NEC survivors develop neuronal deficits later in life, however the effect of early stages of NEC on the developing brain is unknown. Using preterm pigs as a NEC-sensitive animal model, we profiled the hippocampal gene expression in response to severe NEC lesions. The NEC-induced differentially expressed genes (DEGs) in the hippocampus segregated the piglets suffering from small intestinal NEC (Si-NEC) from those showing NEC lesions only in the colon (Co-NEC). Only when NEC lesions were observed in the small intestine, did piglets show reduced physical activity together with up-regulation of hippocampal genes related to inflammation and hypoxia, which was further verified by qPCR. Cluster analyses revealed key hippocampal NEC–related DEGs for Si-NEC (23 genes, including S100A8, PDK4, EDN1, IER3, Opalin, TXNIP) and Co-NEC (3 genes: GSTM3, TF, and S100A1). Both NEC phenotypes showed only two down-regulated DEGs (TMEM 167, HBB) and were devoid of any histological signs of microglia activation. Cerebrospinal fluid (CSF) from NEC-positive pigs contained elevated levels of several inflammatory proteins and in vitro exposure of immature hippocampal neurons to NEC-related CSF promoted neuritogenesis. Further in vitro experiments with neurite outgrowth indicated that VEGF, CINC-3, S100A9 and S100A8/S100A9 may play a role in NEC effects on hippocampal development. In conclusion, NEC lesions, especially when involving the small intestine, alter hippocampal gene expression with potential neuroinflammation and effects on neural circuit formation. Our results demonstrated that gut lesions affect the immature brain at early stages of disease progression. Thus, supportive care is important for preterm infants experienced with NEC to lessen possible later neurological dysfunctions.
Overall design: Examination of hippocampal transcriptome in NEC (n=5 and 6 for colon-NEC and small intestine-NEC, respectively) and healthy preterm neonates (n=5).
Less...