Fig. 1

Impaired colon mucosal barrier in Fpr2^−/− mice. A Shortened colon crypts in Fpr2^−/− mice at different ages. H&E staining. Scale bar = 100 μm. Right: Quantitation of crypt length of colons at different mouse ages. n = 4–8 mice/group. ****P < 0.0001. B Reduced Muc2 production in colon crypts of Fpr2^−/− mice. Green: Muc2, Blue: Nuclei. Scale bar = 50 μm. Right: Quantitation of Muc2⁺ fluorescence intensity/crypt, n = 18–20 crypts from 6 mice/group, ****P < 0.0001. C Reduced level of Muc2 in the feces of Fpr2^−/− mice. The Muc2 concentration in the feces was expressed as ng/1 mg protein in feces. n = 8 mice/group, **P < 0.01. D Reduced number of goblet cells in the colon of Fpr2^−/− mice. An alcian blue stain. Scale bar = 50 μm. Right panel Quantitation of PAS⁺ goblet cells per crypt, n = 23–25 crypts from 4 mice/group. ****P < 0.0001. E Reduced number of Ki67⁺ cells in the colon of Fpr2^−/− mice. Red: Ki67⁺ cells, Blue: Nuclei. Scale bar = 50 μm. Right: Quantitation of Ki67⁺ cells per crypt, n = 20–25 crypts from 4 mice/group. ****P < 0.0001. F Increased production of IL-1β in the colon mucosa of Fpr2^−/− mice. Red: IL-1β, Blue: Neuclei. Scale bar = 50 μm. Right: Quantitative IL-1β + fluorescence intensity, n = 19–24 crypts from 4 mice/group. ****P < 0.0001. G Increased production of IL-1β in the colon mucosa of Fpr2^−/− mice measured by ELISA. n = 10–11 mice/group, ****P < 0.0001. H-J WT (Fpr2^+/+) and Fpr2^−/− mice were co-housed for 4 weeks after weaning, followed by separation for an additional 6 weeks. Fecal pellets were collected to analyze microbiota by 16S rRNA sequencing. H Heat map showing 18 bacterial strains at the phylum levels in the feces. I Quantitation of microbiota in the feces of WT and Fpr2^−/− mice, showing significantly reduced Firmicutes and Deferribacteres but increased Proteobacteria in Fpr2^−/− mouse microbiota. *P < 0.05, ***P < 0.001. J The principal coordinate analysis (PCA) indicating that the abundance of bacteria in the gut of Fpr2^−/− mice is different from WT mice.