Akkermansia muciniphila: a member of the gut microbiota that modulates intestinal stem cell function

Akkermansia muciniphila, a commensal bacterium that represents 1%-4% of the fecal microbiota in healthy adults, and can use mucin as a sole source of carbon and nitrogen, has attracted interest as soon as it was discovered due to the relationship between its abundance and various benefits, particularly pertaining to metabolic health. Especially noteworthy is the finding that A. muciniphila stimulates the proliferation and differentiation of intestinal stem cells, as part of tissue homeostasis and repair after biological, chemical, or physical injury. In this review, we discuss some of the evidence that supports the ability of A. muciniphila and of specific bacterial proteins to support the intestinal stem cell niche. The additional finding that some of these benefits are exerted during gestation on fetal stem cells, persist into adulthood, and influence crypt regeneration after injury, suggests that A. muciniphila may be part of the gestational environment that shapes the health of offspring. Although most A. muciniphila health benefits were characterized using Muc^T (A. muciniphila ATCC BAA-835), the discovery of large phylogenetic and functional diversity within the Akkermansia genus galvanized efforts to compare different strains for their individual health profiles. Even closely related A. muciniphila strains may not always share the same health benefits, and sometimes the same strain may be beneficial or harmful depending on host-related factors, pointing toward the need to characterize health phenotypes at the strain level and in context of the host, and underscoring the ongoing gaps in defining the optimal formulation and safety profile of individual strains.