Aspirin inhibits the proliferation of synovium-derived mesenchymal stem cells by arresting the cell cycle in the G0/G1 phase.

Mesenchymal stem cells (MSCs) provide promising applications for clinical treatments. However, patients often take medications that affect the viability of transplanted MSCs. The aim of this study was to assess the effects and underlying mechanism of action of aspirin on the proliferation of MSCs. We showed that aspirin inhibited the growth of MSCs in a concentration- and time-dependent manner. Analysis of cell-cycle distributions showed significantly increased cell populations in the G0/G1 phase and decreased cell populations in the S phase and G2/M phase with increasing concentrations of aspirin. We further analyzed the expression of cyclins and found that the level of cyclin D1 was significantly reduced after aspirin treatment, while there was no obvious effect on the levels of cyclin A2 and cyclin E1. Because we showed that the expression of miRNA145 was significantly increased after aspirin treatment, we further transfected MSCs with an miRNA145 mimic or miRNA145 inhibitor. Transfection with the miRNA145 mimic resulted in decreased expression of cyclin D1, while transfection with miRNA145 inhibitor resulted in increased expression of cyclin D1. Transfection with miRNA145 inhibitor abolished the downregulation of cyclin D induced by aspirin. The results suggested that aspirin inhibited the proliferation of MSCs and caused cell-cycle arrest in the G0/G1 phase through downregulation of cyclin D1, which could be related to the increased expression of miRNA145.