MK increases the paracrine effects of MSCs. A and B: Real-time PCR analysis of pro-angiogenesis factors (VEGF, TGF-β, FGF2 and FGF7) and stem cell factor (SDF-1, IGF-1, GM-CSF and SCF) mRNAs. The relative expression of VEGF (5.85-fold), TGF-β (2.78-fold), IGF-1 (3.7-fold) and SDF-1 (2.01-fold) mRNA in MSCs-MK were higher than in control cells (***p< 0.01). C: ELISA of IGF-1, SDF-1a, VEGF and TGF-β1 protein levels in the culture supernatants of MSCs, MSCs-GFP and MSCs-MK. MSCs-MK secreted more SDF-1a (9.23 ng/ml), VEGF (8.34 ng/ml) and TGF-β1 (17.88 ng/ml) than MSCs (6.35, 4.75 and 9.18 ng/ml) and MSCs-GFP (6.92, 4.55 and 9.88 ng/ml); this was not the case for IGF-1 (MSCs-MK, 1.89 vs. MSCs, 1.51 and MSCs-GFP 1.40 ng/ml). FGF, fibroblast growth factor; GM-CSF, Granulocyte-macrophage colony-stimulating factor; IGF-1, Insulin-like growth factor 1; MSCs-GFP, Mesenchymal stem cells-green fluorescent protein; MSCs-MK, Mesenchymal stem cells-midkine; SCF, Stem cell factor; SDF-1, Stromal cell-derived factor 1; TGF-β, Transforming growth factor beta; VEGF, Vascular endothelial growth factor.