Abstract
Recurrent C. difficile infection (CDI) is a major health threat with significant mortality and financial costs. Fecal Microbiota Transplantation (FMT) is an effective therapy, however the mechanisms by which it acts, particularly on the host, are poorly understood. Here we enrolled a prospective cohort of human patients with recurrent CDI (n=16) undergoing FMT therapy. Colonic biopsies were collected and bulk RNA sequencing was performed to compare changes in host gene expression pre- and two months post-FMT. Transcriptional profiles were significantly altered after FMT therapy, with many differentially expressed genes (~15% of annotated genes detected). Enrichment analysis determined that these changes were reflective of increased protein production post-FMT, with enrichment of pathways such as Ribosome Biogenesis, Protein Processing, and signaling pathways (Myc, mTORc1, E2F) associated with cell proliferation and protein biosynthesis. Histology of H&E-stained biopsies identified a significant increase in colonic crypt length post-FMT, suggesting that this treatment promotes cell proliferation. Crypt length was significantly correlated with enriched Myc and mTOR signaling pathways as well as genes associated with polyamine biosynthesis, providing a potential mechanism through which this may occur. Finally, signaling pathways upstream of Myc and mTOR, notably IL-33 Signaling and EGFR ligands, were significantly upregulated, suggesting that FMT may utilize these signals to promote cell proliferation and restoration of the intestine.