Bacteroides fragilis strain ZY-312 promotes intestinal barrier integrity via upregulating the STAT3 signaling pathway in a radiation-induced intestinal injury mouse model

1.1. FIGURE 1 | <em>B. fragilis </em>alleviated total body radiation-induced intestinal injury in mice. (A) (B) The model of radiation-induced intestinal injury in mice. (C)The weight loss. (D)The statistical analysis of SI and colon length. (E) The histopathology morphology of SI. (F) The statistical analysis of histopathology-associated index (HAI) between groups. (G) Periodic acid-Schiff stain (PAS) staining of SI. Control group (N=6), TBI group (N=12), TBI+ZY-312 group (N=12). N, the number of mice. The data are presented as mean ± SEM, and *p &lt; 0.05, **p &lt; 0.01, **p &lt; 0.001, **p &lt; 0.0001. 1.2. FIGURE 2 | <em>B. fragilis</em> alleviated abdominal radiation-induced intestinal injury in mice through <em>B. fragilis</em>-derived PSA. (A) The weight loss. (B) The statistical analysis of small intestinal(SI) length. (C) The statistical analysis of colon length. (D) The histopathology of small intestinal at different magnifications. (E) The HAI between groups. (F) The length of SI crypts between groups. Control group (N=6), TAI group (N=9), TAI+ZY-312 group (N=10), TAI+PSA group (N=8). The data are presented as mean ± SEM, and *p &lt; 0.05, **p &lt; 0.01, **p &lt; 0.001, **p &lt; 0.0001. 1.3. FIGURE 3 | <em>B. fragilis</em> promoted intestinal epithelial cell proliferation, stem cell regeneration, goblet cell secretion, and tight junction repair. (A)The immunohistochemical staining of Ki-67 in SI between groups. (B)The immunofluorescence staining of Ki-67 and Lgr5. (C) The immunofluorescence and Alcian blue-periodic acid-Schiff staining(AB-PAS) of SI goblet cells. (D) The immunofluorescence staining of Claudin-1 and ZO-1. 1.4. FIGURE 4 | <em>B. fragilis</em> did not significantly alter intestinal microbiota to relieve radiation-induced intestinal injury in mice. (A) (B)The phylum level of microbiota composition and comparison of microbiota in mice between samples and groups. (C) (D) The genus level of microbiota composition and comparison of microbiota in mice between samples and groups. (E) The abundance and diversity of microbiota ( Shannon index) in mice. (F) The principal coordinate analysis of microbiota. (G) The bug base analysis of microbiota. (H) The LEfSe analysis of differential bacteria in SI meeting a significant LDA threshold value of &gt;3.5 between groups with different levels. (I) The cladogram based on LEfSe shows differential bacteria of the gut microbiota between groups with different levels. Nd30, Control group; xd30 and TAI, TAI group; xzd30 and TAIZ, TAI+ZY-312 group. 1.5. FIGURE 5 | <em>B. fragilis</em> up-regulated the STAT3 signaling pathway in intestinal epithelial cells. (A)The western blot analysis of pJAK2, pNF-KB, p38, pmTOR, mTOR, pSTAT3, STAT3, MUC2, Claudin-1, Lgr5, and PCNA in SI tissue between groups. GAPDH was regarded as an internal reference. (B)The immunohistochemical staining of pSTAT3 in SI between groups. (C) The western blot analysis of pSTAT3, STAT3 in SI IECs. (D) The western blot analysis of pSTAT3, STAT3 in Non-SI epithelial cells. 1.6. FIGURE 6 | <em>B. fragilis</em> relieved radiation-induced intestinal injury through the STAT3 signaling pathway in intestinal epithelial cells. (A)The weight loss. (B)The statistical analysis of SI and colon length. (C) The histopathology morphology of SI. (D) The HAI of SI between groups. (E) The length of SI crypts between groups.Control group/<em>Stat3</em>△IEC (N=3), TAI/<em>Stat3</em>△IECgroup (N=3), TAI+ZY-312/<em>Stat3</em>△IEC group (N=4), TAI+ZY-312/WT group (N=5). The data are presented as mean ± SEM, and *p &lt; 0.05, **p &lt; 0.01, **p &lt; 0.001, **p &lt; 0.0001. 1.7. FIGURE 7 | <em>B. fragilis</em> promoted intestinal epithelial cell proliferation, stem cell regeneration, goblet cell secretion, and tight junction repair through the STAT3 signaling pathway. (A) The histological staining of pSTAT3, Ki-67, MUC2, PAS, and ZO-1 in SI IECs. (B) The western blot analysis of pSTAT3, STAT3, MUC2, Claudin-1, Lgr5, and PCNA in SI IECs between groups. GAPDH was regarded as an internal reference. 1.8. <strong>FIGURE S1 | WT mice received relieved radiation-induced intestinal injury. (A)The weight loss. (B)The statistical analysis of SI and colon length. (C) The statistical analysis of HAI. (D) The PAS staining of SI.</strong> <strong>Control group/WT (N=3), TAI/WT group (N=5). The data are presented as mean ± SEM, and *p &lt; 0.05, **p &lt; 0.01, **p &lt; 0.001, **p &lt; 0.0001.</strong>