Dietary Fiber Polysaccharide Components Supplementation Modulate Uterine Immune Microenvironment to Support Embryo Implantation via SCFAs ‐Driven Tregs Differentiation

Regulatory T cells (Tregs) are essential for establishing maternal immune tolerance during embryo implantation. Dietary fiber, composed of diverse polysaccharides, has been shown to enhance Tregs populations and improve implantation outcomes, yet the specific components responsible remain unclear. In this study, we investigated the effects of polysaccharide components of dietary fiber, inducing polygalacturonic acid (PGA), arabinoxylan, and cellulose on embryo implantation. We found that PGA significantly promoted implantation, associated with an increased number of decidual Tregs. PGA also enhanced gut microbial diversity and elevated short-chain fatty acids (SCFAs) levels, particularly butyrate, which in turn promoted Tregs differentiation. In vitro, we demonstrated that butyrate enhances Tregs differentiation via GPR43-dependent signaling, which upregulates Tregs associated genes and may activate the adaptive immune response through JAK-STAT and PI3K-Akt pathways. These findings provide new insights into the role of dietary fiber in supporting early pregnancy and suggest novel strategies for preventing embryo loss.