This protocol describes a model of experimental necrotizing enterocolitis (NEC) using rats or mice. NEC is a gastrointestinal disease unique to premature infants. Nearly 10% of babies born <1.5 kg develop this disease, and the mortality rate approaches 50%. The pathogenesis remains incompletely understood, but involves feeding, ischemia, inflammation, and infection. Animal models are vital to advancing the collective understanding of NEC. Many laboratories study NEC using the murine model. Other models, including pigs and rabbits, have limitations, including cost, long gestation periods, and smaller litters. Many studies use known risk factors (enteral feeding, infection, inflammation, and ischemia) in NEC research.
One challenge in NEC research is enteral feeds. Pups, normally breastfed by their mother, must be fed by hand. Some methods include syringe or fine-tip applicator feeds. This requires animals to latch and swallow feeds without respiratory compromise. Risks include aspiration, regurgitation, and spilling of feeds. The complications often cause unintended mortality and inconsistent results. Gavage feedings avoid these complications. Feedings are gavaged using a silastic catheter, allowing for safe, efficient feedings. This reduces feeding-related complications and mortality. This method improves reproducibility, as the complete volume is appropriately administered.
The protocol utilizes three interventions associated with clinical NEC: diet, hypoxia, and inflammation. The diet is a high-calorie formula, which is associated with NEC. Pups receive enteral lipopolysaccharide (LPS). LPS, a Toll-Like Receptor 4 (TLR4) agonist, is associated with NEC in animals and humans. Following feeds, animals are subjected to hypoxia. Premature neonates are susceptible to hypoxemia, which, along with decreased intestinal perfusion following feedings, puts the infant at risk for post-prandial ischemia.