Exploring the role of gut microbiota modulation in the long-term therapeutic benefits of early MSC transplantation in MRL/lpr mice.

BACKGROUND: Systemic lupus erythematosus (SLE), influenced by gut microbiota dysbiosis, is characterized by autoimmune and inflammatory responses. Human umbilical cord-derived mesenchymal stem cell (hUC-MSC) transplantation is an effective and safe treatment for refractory or severe SLE; however, the long-term efficacy and mechanisms of early hUC-MSC therapeutic benefits in SLE need further investigation. METHODS: Here, lupus-prone MRL/MpJ-Fas(lpr) (MRL/lpr) mice were divided into three groups: the control (Ctrl) group received saline injections, while the MSC and MSC-fecal microbiota transplantation (FMT) groups received early hUC-MSC transplants at weeks 6, 8, and 10. The MSC-FMT group also underwent FMT from the Ctrl group between weeks 9 and 13. RESULTS: Our results showed that early MSC treatment extended therapeutic effects up to 12 weeks, reducing autoantibodies, proinflammatory cytokines, B cells, and improving lupus nephritis. It also modulated the gut microbiota, increasing the abundance of beneficial bacteria, such as Lactobacillus johnsonii and Romboutsia ilealis, which led to higher levels of plasma tryptophan and butyrate metabolites. These metabolites activate the aryl hydrocarbon receptor (AHR), upregulate the Cyp1a1 and Cyp1b1 gene, enhance the zonula occludens 1 (ZO-1) protein, promote intestinal repair, and mitigate SLE progression. Notably, FMT from lupus mice significantly reversed hUC-MSC benefits, suggesting that the modulation of the gut microbiota plays a crucial role in the therapeutic response observed in MRL/lpr mice. CONCLUSIONS: This research innovatively explores the early therapeutic window for MSCs in SLE, highlighting the partial mechanisms through which hUC-MSCs modulate the gut microbiota-tryptophan-AHR axis, thereby ameliorating SLE symptoms.