Background: We assessed the hypothesis that diabetic pathological environments would impair the function of diabetes mellitus (DM)-mesenchymal stem cells (MSCs). Methods: The Otsuka Long-Evans Tokushima Fatty (OLETF) rat, an outbred strain of Long-Evans Tokushima Otsuka (LETO) rat, develops obesity and type 2 DM. MSCs were isolated and cultured from bone marrow of OLETF (DM-MSC) and LETO (non-DM-MSC) rats. MSCs were stimulated with tumor necrosis factor (TNF)-慣 (10 ng/mL), H₂O₂ (0.2 mM), and glucose (25 mM). After 30 min, 2h, and 24h of stimulation, protein expression levels of plasminogen activator inhibitor (PAI)-1, signal transducers and activators of transcription (STAT)-3, Akt, Toll-like receptor (TLR)-2, and hepatocyte growth factor (HGF) were determined by Western blot. To evaluate the therapeutic potential of MSCs, myocardial IRI was induced by ligation of LAD for 30 min followed by release in Sprague-Dawley rats. Prior to release of LAD, MSCs (1x10⁶ cells / 0.1 mL of PBS) were injected onto infarct myocardium. After 1 week and 2 weeks, cardiac fibrosis and histologic changes were analyzed by Masson���s trichrome staining and immunohistochemistry. Results: PAI-1 and TLR2 were highly expressed in DM-MSCs in compared with non-DM-MSCs. Cellular responses to TNF-慣, H2O2, and glucose were different between the two types of MSCs.Phosphorylation of Akt and STAT-3 were induced by TNF-慣, H₂O₂, and glucose in non-DM-MSCs, while no changes were detected in DM-MSCs. The cardiac fibrosis was reduced in non-DM-MSC injected rats, while it was not changed in DM-MSC injected rats. In non-DM-MSC injected rats, the expression of von Willebrand factor (vWF) in peri-infarct myocardium was increased, while vascular cell adhesion molecule (VCAM)-1 expression was reduced. On the other hand, the expressions of vWF and VCAM-1 of DM-MSCs injected myocardium were similar to those of IRI control myocardium. Conclusion: Diabetic environments would impair of BM-MSCs in regard to stem cell function in vivo and in vitro.