Abstract Background Mesenchymal stromal cells (MSCs) are heterogeneous populations. Heterogeneity exists within the same tissue and between different tissues. Some studies have found enormous heterogeneity in immunomodulatory function among MSCs derived from different tissues. Moreover, the underlying mechanism of heterogeneity in immunomodulatory abilities is still unclear. Methods Foreskin mesenchymal stromal cells (FSMSCs) and human umbilical cord mesenchymal stromal cells (HuMSCs) were isolated and cultured until the third passage. According to the International Association for Cell Therapy standard, we confirmed the cell type. Then, FSMSCs and HuMSCs were cocultured with human peripheral blood mononuclear cells (PBMCs) stimulated by lipopolysaccharide (LPS) in vitro. Furthermore, the supernatant was sampled for an enzyme-linked immunosorbent assay to investigate the secretion of IL-1β, IL-6, IL-10, TNF-α, and TGF-β1. Finally, we performed single-cell RNA sequencing (scRNA-seq) of FSMSCs and HuMSCs. Results We successfully identified FSMSCs and HuMSCs as MSCs. When cocultured with LPS pretreated PBMCs, FSMSCs and HuMSCs could effectively reduced the secretion of IL-1β and TNF-α. However, FSMSCs stimulated the PBMCs to secrete more IL-10, TGF-β1, and IL-6. Furthermore, 4 cell subsets were identified from integrated scRNA-seq data, including proliferative MSCs (MKI67 +, CD146 low+, NG2 +, PDGFRB − ), pericytes (CD146 high+, PDGFRB +, MKI67 − , CD31 − , CD45 − , CD34 − ), immune MSCs (CXCL12 high+, PTGIS high+, PDGFRB +, CD146 − , MKI67 − ) and progenitor proliferative MSCs (CXCL12 low+, PTGIS low+, PDGFRB +, CD146 − , MKI67 − ). Among them, we found that immune MSCs with strengthened transcriptional activity were similar to pericytes with regard to the degree of differentiated. Various of immune-related genes, gene sets, and regulons were also enriched in immune MSCs. Moreover, immune MSCs were determined to be close to other cell subsets in cell–cell communication analysis. Finally, we found that the proportion of immune MSCs in foreskin tissue was highest when comparing the subset compositions of MSCs derived from different tissues. Conclusions FSMSCs show better immunomodulatory capacity than HuMSCs in vitro. Moreover, immune MSCs may play a vital role in the heterogeneity of immunoregulatory properties. This study provides new insights suggesting that immune MSCs can be isolated to exert stable immunoregulatory functions without being limited by the heterogeneity of MSCs derived from different tissues.

Background: Mesenchymal stromal cells (MSCs) and fibroblasts show similar morphology, surface marker expression, and proliferation, differentiation, and immunomodulatory capacities. These similarities not only blur their cell identities but also limit their application. Methods: We performed single-cell transcriptome sequencing of the human umbilical cord and foreskin MSCs (HuMSCs and FSMSCs) and extracted the single-cell transcriptome data of the bone marrow and adipose MSCs (BMSCs and ADMSCs) from the Gene Expression Omnibus (GEO) database. Then, we performed quality control, batch effect correction, integration, and clustering analysis of the integrated single-cell transcriptome data from the HuMSCs, FMSCs, BMSCs, and ADMSCs. The cell subsets were annotated based on the surface marker phenotypes for the MSCs (CD105 + , CD90 +, CD73 +, CD45 −, CD34 −, CD19 −, HLA-DRA −, and CD11b −), fibroblasts (VIM +, PECAM1 −, CD34 −, CD45 −, EPCAM −, and MYH11 −), and pericytes (CD146 +, PDGFRB +, PECAM1 −, CD34 −, and CD45 −). The expression levels of common fibroblast markers (ACTA2, FAP, PDGFRA, PDGFRB, S100A4, FN1, COL1A1, POSTN, DCN, COL1A2, FBLN2, COL1A2, DES, and CDH11) were also analyzed in all cell subsets. Finally, the gene expression profiles, differentiation status, and the enrichment status of various gene sets and regulons were compared between the cell subsets. Results: We demonstrated 15 distinct cell subsets in the integrated single-cell transcriptome sequencing data. Surface marker annotation demonstrated the MSC phenotype in 12 of the 15 cell subsets. C10 and C14 subsets demonstrated both the MSC and pericyte phenotypes. All 15 cell subsets demonstrated the fibroblast phenotype. C8, C12, and C13 subsets exclusively demonstrated the fibroblast phenotype. We identified 3,275 differentially expressed genes, 305 enriched gene sets, and 34 enriched regulons between the 15 cell subsets. The cell subsets that exclusively demonstrated the fibroblast phenotype represented less primitive and more differentiated cell types. Conclusion: Cell subsets with the MSC phenotype also demonstrated the fibroblast phenotype, but cell subsets with the fibroblast phenotype did not necessarily demonstrate the MSC phenotype, suggesting that MSCs represented a subclass of fibroblasts. We also demonstrated that the MSCs and fibroblasts represented highly heterogeneous populations with distinct cell subsets, which could be identified based on the differentially enriched gene sets and regulons that specify proliferating, differentiating, metabolic, and/or immunomodulatory functions.

Acute lung injury (ALI) is the most common complication of sepsis. Intravenous injection of HUMSCs can regulate the level of circulating endothelial cytokines and alleviate lung injury in juvenile septic rats. In this study, we performed proteomic and phosphorylated proteomic analysis of lung tissue of juvenile septic rats after Human Umbilical Cord Mesenchymal Stem Cells (HUMSCs) intervention for the first time, and screened the potential proteins and pathways of HUMSCs for therapeutic effect. The 4D proteome quantitative technique was used to quantitatively analyze the lung tissues of septic rats 24 hours (3 biological samples) and 24 hours after HUMSCs intervention (3 biological samples). A total of 213 proteins were identified as differentially expressed proteins, and 971 phosphorylation sites changed significantly. Based on the public database, we analyzed the functional enrichment of these proteins and phosphorylated proteins. In addition, Tenascin-C may be the key differential protein and ECM receptor interaction pathway may be the main signal pathway by using various algorithms to analyze the protein-protein interaction network. Phosphorylation analysis showed that tight junction pathway was closely related to immune inflammatory reaction, and EGFR interacted most, which may be the key differential phosphorylated protein. Finally, 123 conserved motifs of serine phosphorylation site (pS) and 17 conserved motifs of threonine (pT) phosphorylation sites were identified by motif analysis of phosphorylation sites. Results from proteomics and phosphorylated proteomics, the potential new therapeutic targets of HUMSCs in alleviating lung injury in juvenile septic rats were revealed.

Background: Mesenchymal stromal cells (MSCs) could be applied for the treatment of immune-related diseases. However, some studies have found there is enormous heterogeneity in immunomodulatory function of MSCs isolated from different tissue. At present, the underlying mechanism of heterogeneity in immunoregulatory function is still unclear. Methods: In this study, the foreskin mesenchymal stromal cells (FSMSCs) and human umbilical cord mesenchymal stromal cells (HuMSCs) were isolated and cultured to the 3rd passage. Cell types were confirmed according to the standard of International Association for Cell Therapy. Then, FSMSCs and HuMSCs were co-cultured with human peripheral blood mononuclear cells (PBMC) stimulated by lipopolysaccharides (LPS) in viro respectively. And the supernatant was sampled for enzyme-linked immunosorbent assay to investigate the secretion of IL-1β, IL-6, IL-10, TNF-α and TGF-β. Finally, single cell transcriptome sequencing was performed in order to elucidate the mechanism for the difference of immunomodulatory function. Results: FSMSCs and HuMSCs are successfully identified as MSCs. When co-cultured with LPS pre-treated PBMC, FSMSCs and HuMSCs could effectively reduce the secretion of IL-1β and TNF-α. But FSMSCs were able to stimulate the PBMC to secrete more IL-10, TGF-β and IL-6. Furthermore, 4 MSCs subsets in integrated data were identified, including Proliferative MSCs , Pericyte, Immune MSCs and Progenitor Proliferative MSCs. Among them, the proportions of Immune MSCs in FSMSCs and HUMSCs were 56% and 10% respectively. Varieties of immune-related genes, gene sets and regulons were enriched in Immune MSCs. And Immune MSCs with powful transcriptional activity were found to be near to Pericyte at the degree of differentiation and closed to other cell subsets. Finally, the foreskin tissue might be an ideal source of isolating Immune MSCs when comparing the subset composition of MSCs derived from adipose tissue and bone marrow from public database. Conclusions: Immune MSCs may play a key role in the heterogeneity of immunoregulatory function. It is a new insight that Immune MSCs could be isolated and better applied for the treatment of immune-related diseases without being limited by the heterogeneity of immunomodulatory function derived from different tissues.