Necrotizing enterocolitis (NEC) remains one of the highest causes of mortality and of acute and long-term morbidity in premature infants. Multiple factors are involved in the pathophysiology of NEC including the immaturity of the immune system and the complex changing composition of the intestinal microbiome. This is compounded by the fact that the premature infant should ideally still be a developing fetus and has an immature intestinal tract. Because these complexities are beyond the scope of studies in single-cell cultures, animal models are absolutely essential to understand the mechanisms involved in the pathophysiology of NEC and the effects of inflammation on the immature intestinal tract. To this end, investigators have utilized many different species (e.g., rats, mice, rabbits, quails, piglets, and non-human primates) and conditions to develop models of NEC. Each animal has distinct advantages and drawbacks related to its preterm viability, body size, genetic variability, and cost. The choice of animal model is strongly influenced by the scientific question being addressed. While no model perfectly mimics human NEC, each has greatly improved our understanding of disease. Examples of recent discoveries in NEC pathogenesis and prevention underscore the importance of continued animal research in NEC.
Necrotizing enterocolitis (NEC) is a deadly disease that occurs in 5-10% of neonates. Although NEC has been extensively studied, no single therapeutic target has been identified. Rho kinase (ROCK) is a serine/threonine kinase that affects multiple cellular processes, including tight junction (TJ) function, cellular permeability, and apoptosis. We hypothesized that ROCK inhibition would decrease cellular permeability, stabilize TJ proteins (occludin), and decrease the severity of NEC. To test this hypothesis, human colon epithelial cells (Caco-2) and human endothelial cells were studied. Cells were treated with lipopolysaccharide to simulate an in vitro model of NEC. The effect of ROCK inhibition was measured by transepithelial membrane resistance (TEER) and cellular permeability to FITC-dextran. The effects of ROCK inhibition in vivo were analyzed in the rat pup model of NEC. NEC was induced by feeding formula supplemented with Cronobacter sakazakii with or without gavaged ROCK inhibitor. Rat intestines were scored based on histological degree of injury. RNA and protein assays for occludin protein were performed for all models of NEC. Treatment with ROCK inhibitor significantly decreased cellular permeability in Caco-2 cells and increased TEER. Intestinal injury scoring revealed decreased scores in ROCK inhibitor-treated pups compared with NEC only. Both cell and rat pup models demonstrated an upregulation of occludin expression in the ROCK inhibitor-treated groups. Therefore, we conclude that ROCK inhibition protects against experimental NEC by strengthening barrier function via upregulation of occludin. These data suggest that ROCK may be a potential therapeutic target for patients with NEC. NEW & NOTEWORTHY These studies are the first to demonstrate an upregulation of occludin tight junction protein in response to Rho kinase (ROCK) inhibition. Furthermore, we have demonstrated that ROCK inhibition in experimental models of necrotizing enterocolitis (NEC) is protective against NEC in both in vitro and in vivo models of disease.
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