A direct comparison of mouse and human intestinal development using epithelial gene expression patterns

Abstract

PURPOSE: Preterm infants are susceptible to unique pathology due to their immaturity. Mouse models are commonly used to study immature intestinal disease including necrotizing enterocolitis (NEC). Current NEC models are performed at a variety of ages, but data directly comparing intestinal developmental stage equivalency between mice and humans are lacking. METHODS: Small intestines were harvested from C57B1/6 mice at 3–4-day intervals from birth to P28 (n=8 at each age). Preterm human small intestine samples representing 17–23 weeks of completed gestation were obtained from the University of Pittsburgh Health Sciences Tissue Bank, and at term gestation during reanastamoses after resection for NEC (n=4–7 at each age). Quantification of intestinal epithelial cell types and mRNA for marker genes were evaluated on both species. RESULTS: Overall, murine and human developmental trends over time are markedly similar. Murine intestine prior to P10 is most similar to human fetal intestine prior to viability. Murine intestine at P14 is most similar to human intestine at 22–23 weeks completed gestation, and P28 murine intestine is most similar to human term intestine. CONCLUSION: Use of C57BL/6J mice to model the human immature intestine is reasonable, but the age of mouse chosen is a critical factor in model development.

The Paneth Cell: The Curator and Defender of the Immature Small Intestine

“…Paneth cells first appear in the small intestine of humans at 13.5 weeks gestational age (15,16). Paneth cell density in the developing fetal intestine is relatively low, but gradually increases throughout gestation, with significant increases in the third trimester after 29 weeks completed gestation (17,18). Paneth cell levels do not reach quantities similar to adult levels until term gestation or later (17).…”

“…It is therefore important to note that not all mammals develop Paneth cells prenatally, but instead develop them mid-way through intestinal development after villus development, but before intestinal maturity according to a normal developmental pattern. For example, the commonly used C57Bl/6 mouse strain does not develop Paneth cells until 7-10 days after birth (18,19).…”

“…In addition to killing pathogens, AMPs can also influence the immune system through white blood cell chemotaxis (81), activation of dendritic cells (82), and downregulation of immunomodulators such as cortisol (68,71). In infants born prematurely, this switch is temporally similar to when extremely preterm infants are most susceptible to develop NEC (18).…”

“…In adapting this model to mice, our laboratory and others have shown that selective ablation of Paneth cells followed by enteric gavage of Klebsiella pneumoniae in 14-days old mice results in grossly necrotic intestines (89,(117)(118)(119), an increase in serum inflammatory markers (119), and alterations in the microbiome (14) that are consistent with human NEC. The use of 2-weeks old mice in this model is potentially advantageous as well as they possess a gene expression profile of epithelial cell genes that matches the expression profile seen in preterm human infants during the window when they are most susceptible to develop NEC (18,67). Interestingly, disruption of Paneth cell biology via administration of the heavy metal chelator dithizone prior to normal Paneth cell development (5 days old mice) does not result in a NEC-like phenotype (117).…”

“…In an already dysbiotic environment, this combination is exactly the milieu that is modeled in our animal model and predisposes to development of injury. This is further compounded because the Paneth cells present in the immature intestine are not fully mature or functional at a baseline (18). This limited Paneth cell cohort also means that there is a limited capacity for protection via AMPs (40).…”