CD317-Positive Immune Stromal Cells in Human "Mesenchymal Stem Cell" Populations

Heterogeneity of bone marrow mesenchymal stromal cells (MSCs, frequently referred to as "mesenchymal stem cells") clouds biological understanding and hampers their clinical development. In MSC cultures most commonly used in research and therapy, we have identified an MSC subtype characterized by CD317 expression (CD317^pos (29.77 ± 3.00% of the total MSC population), comprising CD317^dim (28.10 ± 4.60%) and CD317^bright (1.67 ± 0.58%) MSCs) and a constitutive interferon signature linked to human disease. We demonstrate that CD317^pos MSCs induced cutaneous tissue damage when applied a skin explant model of inflammation, whereas CD317^neg MSCs had no effect. Only CD317^neg MSCs were able to suppress proliferative cycles of activated human T cells in vitro, whilst CD317^pos MSCs increased polarization towards pro-inflammatory Th1 cells and CD317^neg cell lines did not. Using an in vivo peritonitis model, we found that CD317^neg and CD317^pos MSCs suppressed leukocyte recruitment but only CD317^neg MSCs suppressed macrophage numbers. Using MSC-loaded scaffolds implanted subcutaneously in immunocompromised mice we were able to observe tissue generation and blood vessel formation with CD317^neg MSC lines, but not CD317^pos MSC lines. Our evidence is consistent with the identification of an immune stromal cell, which is likely to contribute to specific physiological and pathological functions and influence clinical outcome of therapeutic MSCs.

Caspase 3 may participate in the anti-tumor immunity of dendritic cells

BACKGROUND

Caspase 3 is not only involved in apoptosis, but also participates in the nonapoptotic functions. Previously, we found that caspase 3 gene knockout mice displayed decreased number of dendritic cells (DCs). However, whether caspase 3 participate in the function of DCs is unclear. Thus, the present study aims to investigate the role of caspase 3 in the maturation and antitumor function of DCs.

METHODS

Caspase 3 gene was overexpressed in DC2.4 cell line through Lentivirus system. The impact of caspase 3 gene overexpression on the biological behavior of DC2.4 cells was determined by CCK-8, colony formation and apoptosis analysis. The impact of caspase 3 gene overexpression on the antigen uptake, maturation, migration, T cell activation of DC2.4 cells was analyzed with phagocytosis, transwell and mixed lymphocyte reaction assay. Tumor growth and tumor infiltrated T cells were also investigated through tumor bearing model.

RESULTS

Caspase 3 gene overexpression could slightly increase the apoptosis of DC2.4 cells. Antigen uptake capability and maturation of DC2.4 cells were significantly promoted through caspases 3 gene overexpression. However, CXCR4 expression on DC2.4 cells and migration of DC2.4 cells were not influenced. Caspase 3 gene overexpression also enhanced the T cell activation and cytotoxicity of activated T cells. Finally, overexpression of caspase 3 gene significantly increased the tumor suppression of DC2.4 cells, accompanied by increased infiltration of CD4⁺ and CD8⁺ Cells in tumor tissue.

CONCLUSION

Caspase 3 gene overexpression could promote maturation and enhance antitumor capability of DC2.4 cells.