Purinergic Stimulation of Human Bone Marrow-Derived Mesenchymal Stem Cells Modulate Their Function and Differentiation Potential.

Human bone marrow derived Mesenchymal Stem Cells (hMSCs) are adult multipotent cells. hMSCs differentiate in vitro and in vivo into several tissue lineages originating from the three germinal layers making them attractive candidates for bioengineering and cellular therapy. Thus, it seems of great relevance to search putative messengers and signalling able to modulate their proliferation and differentiation. Nucleotides triphosphates are extracellular messengers binding to specific receptors (P2Rs) that modulate cell functions depending on the cell type. Controversial information is available on P2 expression and activity in hMSCs.

Here we found that hMSCs expressed several P2R subtypes. hMSCs were very resistant to the cytotoxic effects of high concentrations of ATP, as demonstrated by the lack of morphological and mitochondrial changes or release of intracellular markers of cell death. Gene expression profiling revealed that ATP treatment down-regulated cell proliferation and up-regulated cell migration genes in hMSCs. Functional studies confirmed the inhibitory activity of ATP on proliferation and clonogenic ability of hMSCs. Furthermore, ATP potentiated the chemotactic response of hMSCs to the chemokine CXCL12, and increased their spontaneous migration. In vivo, xenotransplant experiments showed that the homing capacity of hMSCs to murine bone marrow was increased by ATP pre-treatment. Moreover, ATP increased pro-inflammatory cytokines production (IL-2, IFN-g, IL-12p70), while decreased secretion of the anti-inflammatory cytokine IL-10. This finding was associated with the reduced ability of ATP-treated hMSC of inhibiting T-cell proliferation. Microarrays data suggested that several genes implicated in hMSC differentiation can be modulated by ATP treatment. To further investigate this issue, hMSCs cells were cultured under adipogenic or osteogenic conditions and were transiently exposed to ATP before starting differentiation or continuously exposed to ATP for the first 3 days of differentiation induction. We demonstrated that adipogenesis-related accumulation of lipids, analyzed by Oil red O staining, was more evident in ATP treated cultures. Furthermore, quantitative real time PCR (qRT-PCR) assay showed that mRNA expression of PPARg, a transcription factor early up-regulated during adipogenesis, was significantly increased in hMSCs differentiated cells treated with ATP. In osteogenic condition, analysis of mineralized area through Alizarin Red staining, indicated that ATP treatment enhanced the extent of mineralization compared to untreated control. The expression of RUNX2, a key transcription factor in osteogenesis, analyzed by qRT-PCR in differentiated cells confirmed data obtained in Alizarin-based assay.

These data demonstrated that purinergic signalling modulates biological functions and differentiation potential of hMSCs.

No relevant conflicts of interest to declare.