Unraveling the interplay between mesenchymal stem cells, gut microbiota, and systemic sclerosis: therapeutic implications

Abstract

Systemic sclerosis (SSc) is an autoimmune disease with progressive fibrotic disorders in multiple organs. Mesenchymal stem cells (MSCs) have shown great potential in treating SSc, but the exact regulatory mechanism is not fully understood. In this study, we used human umbilical cord-derived MSCs (hUC-MSCs) to treat SSc mice induced by bleomycin. The gut microbiota composition and predicted functions were analyzed using 2bRAD sequencing of fecal samples from control, SSc, and MSCs-treated mice. Treatment with MSCs improved the bleomycin-induced SSc mice, characterized by significantly reduced collagen deposition and dermal thickness. The gut microbiota of SSc mice exhibited lower species evenness and was clearly separated from the control mice based on beta diversity. MSC treatment led to a significant reduction of conditionally pathogenic bacteria enriched in SSc, including Akkermansia muciniphila and Parasutterella excrementihominis. Conversely, the relative abundance of butyrate-producing bacteria, such as Roseburia, Butyricicoccus porcorum, and Gemmiger formicilis, was notably increased in MSCs-treated SSc mice. Additionally, the functional analysis revealed that MSCs intervention effectively enhanced sulfur metabolism, tryptophan metabolism, citrate cycle, RNA polymerase, and beta-lactam resistance. In summary, the findings in the present study have suggested the close association between gut microbiota and metabolic dysbiosis in mice with SSc. The administration of MSCs has been shown to regulate the disrupted metabolic pathways in SSc mice, thus restoring the normal function of the gut microbiota. This study provides valuable insights into the specific gut microbiota and metabolic pathways involved in the efficacy of MSC treatment, thereby proposing a novel therapeutic strategy for SSc.

Importance: Human umbilical cord-derived mesenchymal stem cells (HUC‑MSCs) demonstrate efficacy in alleviating skin thickening and collagen deposition in systemic sclerosis (SSc) mice, which also regulate the gut microbiota composition and function. Specifically, MSC intervention leads to a notable increase in butyrate-producing bacteria, a decrease in Akkermansia muciniphila and Parasutterella excrementihominis, and a reversal of the dysregulated microbial function in SSc mice. These findings underscore the potential significance of gut microbiota in the therapeutic effects of MSCs in SSc.

Keywords: 2bRAD sequence; gut microbiota; mesenchymal stem cells; metabolism; systemic sclerosis.

Fig 1

Phenotype identification of MSCs. (A) Negative surface markers (CD34, CD45, and HLA-DR) identification of MSCs. (B) Positive surface markers (CD44, CD73, and CD90) identification of MSCs.

Fig 2

hUC-MSCs alleviated bleomycin-induced skin sclerosis in mice. (A) Representative images of H&E staining of the skin from mice of CON, SSc, and MSC groups (100×). The dermis is marked by the black bidirectional arrow. The subcutaneous fat layer is marked by the red bidirectional arrow. Scale bar = 100 µm. (B) Measuring the thickness of the dermis in the black skin of mice. Values were determined in at least 30 random points from each section. CON n = 5; SSc n = 4; MSC n = 4; data are shown as mean ± standard error of mean (SEM). *, P < 0.05; **, P < 0.01. (C) Representative images of Masson-Trichrome staining of the skin from mice of CON, SSc, and MSC groups (100×). The collagen fibers are dyed blue. Scale bar = 100 µm.

Fig 3

Composition of gut microbiota in the CON, SSc, and MSC groups. (A–C) Species number, gut microbiota composition, and the top 10 species at the phylum level. (D–F) Species number, gut microbiota composition, and the top 10 species at the genus level. (G–I) Species number, gut microbiota composition, and the top 10 species at the species levels.

Fig 4

The diversity of the gut microbiota among CON, SSc, and MSC mice. (A) The species accumulation curve of species numbers among the three groups. (B and C) Chao1 and Simpson indexes of gut microbiota α diversity between groups. (D–F) PCoA analysis of gut microbiota β diversity between groups at the phylum, genus, and species levels.

Fig 5

Specific species of gut microbiota between groups. (A) Annotated branch diagram of gut microbiota-specific species between CON and SSc mice. (B) Taxa with differential abundance between CON and SSc mice analyzed with LefSe. (C) Annotated branch diagram of gut microbiota-specific species between SSc and MSC mice. (D) Taxa with differential abundance between SSc and MSC mice analyzed with LefSe. Only species with an LDA of >2 are shown.

Fig 6

Function of gut microbiota predicted by PICRUSt2 in the CON, SSc, and MSC groups. (A) PCoA of gut microbiota function analysis. (B) PCoA of gut microbiota function analysis. (C) PCoA of gut microbiota function analysis. (D) Gut microbiota function enriched analysis.