Gut microbiota influence anastomotic healing in colorectal cancer surgery through modulation of mucosal proinflammatory cytokines

Colorectal cancer (CRC) is the third most diagnosed cancer, and requires surgical resection and reconnection, or anastomosis, of the remaining bowel to re-establish intestinal continuity. Anastomotic leak (AL) is a major complication that increases mortality and cancer recurrence. Our objective is to assess the causal role of gut microbiota in anastomotic healing.The causal role of gut microbiota was assessed in a murine AL model receiving faecal microbiota transplantation (FMT) from patients with CRC collected before surgery and who later developed or not, AL. Anastomotic healing and gut barrier integrity were assessed after surgery. Bacterial candidates implicated in anastomotic healing were identified using 16S rRNA gene sequencing and were isolated from faecal samples to be tested bothin vitroandin vivo.Mice receiving FMT from patients that developed AL displayed poor anastomotic healing. Profiling of gut microbiota of patients and mice after FMT revealed correlations between healing parameters and the relative abundance ofAlistipes onderdonkiiandParabacteroides goldsteinii. Oral supplementation withA. onderdonkiiresulted in a higher rate of leaks in mice, while gavage withP. goldsteiniiimproved healing by exerting an anti-inflammatory effect. Patients with AL and mice receiving FMT from AL patients presented upregulation of mucosal MIP-1α, MIP-2, MCP-1 and IL-17A/F before surgery. Retrospective analysis revealed that patients with AL present higher circulating neutrophil and monocyte counts before surgery.Gut microbiota plays an important role in surgical colonic healing in patients with CRC. The impact of these findings may extend to a vast array of invasive gastrointestinal procedures.