Akkermansia muciniphila is permissive to arthritis in the K/BxN mouse model of arthritis

Abstract

Studies have identified abnormalities in the microbiota of patients with arthritis. To evaluate the pathogenicity of human microbiota, we performed fecal microbial transplantation from children with spondyloarthritis and controls to germ-free KRN/B6xNOD mice. Ankle swelling was equivalent in those that received patient vs. control microbiota. Principal coordinates analysis revealed incomplete uptake of the human microbiota with over-representation of two genera (Bacteroides and Akkermansia) among the transplanted mice. The microbiota predicted the extent of ankle swelling (R2 = 0.185, p = 0.018). The abundances of Bacteroides (r = -0.510, p = 0.010) inversely and Akkermansia (r = 0.367, p = 0.078) directly correlated with ankle swelling. Addition of Akkermansia muciniphila to Altered Schaedler's Flora (ASF) resulted in small but statistically significant increased ankle swelling as compared to mice that received ASF alone (4.0 mm, 3.9-4.1 vs. 3.9 mm, IQR 3.6-4.0, p = 0.041), as did addition of A. muciniphila cultures to transplanted human microbiota as compared to mice that received transplanted human microbiota alone (4.5 mm, IQR 4.3-5.5 vs. 4.1 mm, IQR 3.9-4.3, p = 0.019). This study supports previous findings of an association between A. muciniphila and arthritis.

Figure 1

Boxplots of ankle thickness (A) and antibody titers against glucose-6 phosphate isomerase (GPI; B) in mice transplanted with fecal material from enthesitis-related arthritis (ERA) patients (n = 12) or healthy controls (n = 12), compared to germ-free (GF) mice (n = 23) as well as those moved from the GF to the specific-pathogen free (SPF) facility (n = 11.)

Figure 2

Principal coordinates of transplanted (n = 24), GF (n = 23), and SPF (n = 11) mice, as well as human donors (n = 24.) 2A shows all four groups (human donors = red, GF mice = green, transplanted mice = blue, SPF mice = orange.) 2B only shows the humans (red) and recipient mice (blue), with each mouse-human dyad connected by a line.

Figure 3

Taxonomy of human donors (n = 24; A) and recipient mice (n = 24; B). Genera with frequency > 4% are shown. Akkermansia is shown in dark blue.

Figure 4

Ankle thickness as a function of the fecal abundance of the Bacteroides (A) and Akkermansia (B) genera. N = 24 for both figures. Microbiota from ERA patients and controls is colored blue and red, respectively.

Figure 5

Boxplot of ankle thickness in mice transplanted with A. muciniphila alone (AKK; n = 4), A. muciniphila + Altered Schaedler’s flora (AKK / ASF; n = 16), ASF alone (n = 17), B. fragilis + ASF (BF + ASF; n = 7); or germ-free (GF; n = 23) mice..

Figure 6

Boxplot of ankle thickness in mice receiving feces from a healthy human donor (HD) with (n = 9) or without (n = 9) supplementation with A. muciniphila.

Figure 7

Mucin thickness of transplanted mice. Cecal sections were stained with the Alcian Blue pH 2.5 + Periodic acid–Schiff (PAS) stain, and the area of mucus and epithelium were determined by manual tracing using Image Pro Plus v7.0. 7A and 7B depict representative sections of mice receiving ASF with (7A) or without (7B) supplemental A. muciniphila. Mucin stain appears as a blue layer (arrows) overlying the epithelium. A Boxplot summarizing the results is shown in 7C (n = 10 for A. muciniphila + ASF, n = 9 for ASF alone.)