Sushma C Maddipatla, Sachith Munasinghe, Anne Dodd, Christopher Tastad, Rachel Moss, Hong Yin, Shanta Murthy, Abhishek Dash, Vasantha L Kolachala, David J Cutler, Judy Cho, Subra Kugathasan, Jason D Matthews
During inflamed CD rectum with fistula, CD4+ macrophages alter cellular networks in the lamina propria while forming large cell aggregates, likely mediating complex interactions with T cells and possibly microbial antigens that are involved in the more severe pathological conditions associated with fistula tract formation and progression.
BACKGROUND: Perianal fistulizing Crohn's disease is a severe morbidity with rectal involvement and a higher prevalence in African Americans (AA) compared to Europeans Americans (EA). In this study, we sought to define distinguishing cellular and molecular features between inflamed rectal Crohn's disease (CD) with and without perianal fistula across populations that give new insight into disease severity or progression.
METHODS: Rectal mucosal biopsies were obtained for single cell sequencing from 50 individuals (262k cells); 18 CD rectum with fistula, 25 with CD rectum without fistula and any other perianal complications, and 7 from individuals with no past/present mucosal disease (controls). Spatial transcriptomics were conducted and analyzed by Sopa and Squidpy, while immunofluorescence was processed with QuPath. Patient derived rectal organoids were used to test inflammatory signaling.
RESULTS: A major distinction between inflamed CD rectum with and without fistula was the decreased phagocytic signature, antigen processing profile, and unique morphological structures of pro-inflammatory CD4+CD68+ macrophages. In fistulizing CD, these macrophages formed large aggregates in the lamina propria near epithelial crypts and appeared to disrupt cellular networks by engaging in signaling with other cell subtypes. At the population level, the most significant differences in cellular pathways were detected between AA and EA with inflamed CD rectum and fistula, and between with and without fistulizing disease amongst AA.
CONCLUSION: During inflamed CD rectum with fistula, CD4+ macrophages alter cellular networks in the lamina propria while forming large cell aggregates, likely mediating complex interactions with T cells and possibly microbial antigens that are involved in the more severe pathological conditions associated with fistula tract formation and progression.