NEC-inducing stresses increase expression of junctional adhesion molecule like protein (JamL) which impairs postnatal intestinal microvascular development 3253

Description Necrotizing enterocolitis (NEC) is a life-threatening disease affecting preterm infants for which no therapy currently exists. We have shown that gut microvascular maldevelopment may predispose to NEC. Embryonically-derived macrophages (eMΦ) are abundant in the neonatal small intestine (SI), where they interact with endothelial cells (EnC) to support postnatal vascular expansion. However, how NEC-inducing stresses affect SI eMΦ is unknown. We found in neonatal pups subjected to a NEC model compared to dam fed littermates (2-day-old) using scRNAseq, that junctional adhesion molecule-like protein (JamL) is one of the most upregulated genes in SI MΦ. PCR and western blot confirmed higher JamL mRNA and protein in the NEC pups. In humans, NEC tissue samples had more JAML+ cells compared to controls. Based on the scRNAsq data, JamL expression was upregulated across most neonatal SI MΦ populations, including a pro-angiogenic, perivascular CD206+MHCII- eMΦ population. Recombinant JamL treatment decreased EnC proliferation in both dam fed and NEC pups while in NEC pups, JamL siRNA improved EnC proliferation. In the NEC model, JamL siRNA enhanced survival (χ2 =4.2, p < 0.05) and reduced disease severity (p < 0.05). The JamL receptor, coxsackievirus and adenovirus receptor (Cxadr) is required for embryonic heart and vessel development. Our findings suggest that NEC-induced JamL may alter eMΦ pro-angiogenic function by interacting with Cxadr, disrupting postnatal microvascular development.