Mesenchymal stem cells (MSCs) are capable of differentiating into both cardiac and endothelial lineages and thus an attractive cell source for myocardial regeneration. However, little is known about the mechanisms underlying the proliferation of MSCs. The study is to identify the factors and signaling pathways involved in proliferating of bone marrow-derived MSCs (BMMSCs). Stem cell antigen (Sca-1)+ BMMSCs were purified by magnetic-activated cell sorting system from bone marrow of ICR mice. The effect of cytokines, growth factors, and signal pathways involved in the proliferation of Sca-1+ BMMSCs was analyzed by BrdU incorporation assay and Western blotting. Among cytokines and growth factors examined in this study, basic fibroblast growth factor (bFGF) and FGF4 stimulated significantly the proliferation of Sca-1+ BMMSCs (control, 1±0.05 vs. bFGF, 4.34±0.22 vs. FGF4, 3.62±0.26, P < 0.05, respectively). The proliferation of Sca-1+ BMMSCs activated by FGFs was partly or almost blocked by JAK/STAT3 pathway inhibitors (piceatannol, AG490), a phosphatidylinositol 3-kinase inhibitor (LY294002), a mitogen-activated protein kinase inhibitor (MAPK, PD98059), a MAPK/ERK inhibitor (U0126) treatment as determined by BrdU proliferation assay. In Western blot analysis, no changes were observed in total ERK and Akt, the phosphorylated ERK (p-ERK) and p-Akt levels increased early at 15 minutes in bFGF- or FGF4-treated Sca-1+ BMMSCs, and p-ERK and p-Akt upregulation induced by FGFs was prevented by pretreatment with ERK inhibitor, U0126 and Akt inhibitor, LY294002. There was no change in p-JAK2 or total JAk2 levels in Sca-1+ BMMSCs induced by FGFs. Moreover, the activation of transcription factor, c-jun in FGF4- and bFGF-treated Sca-1+ BMMSCs was observed after 12 or 24 h, respectively. However, other proliferation markers, c-fos and c-myc levels were not affected in bFGF- or FGF4-treated Sca-1+ BMMSCs. Taken together, these results demonstrated that FGFs promote the proliferation of Sca-1+ BMMSCs through the activation of ERK/Akt signaling pathways and transcription factor, c-jun.
|
