Proteomic profiling of bone marrow mesenchymal stem cells upon transforming growth factor β1 stimulation

Bone marrow mesenchymal stem cells (MSCs) can differentiate into different types of cells and have tremendous potential for cell therapy and tissue engineering. Transforming growth factor β1 (TGF-β) plays an important role in cell differentiation and vascular remodeling. We showed that TGF-β induced cell morphology change and an increase in actin fibers in MSCs. To determine the global effects of TGF-β on MSCs, we employed a proteomic strategy to analyze the effect of TGF-β on the human MSC proteome. By using two-dimensional gel electrophoresis and electrospray ionization coupled to quadrupole/time-of-flight tandem mass spectrometers, we have generated a proteome reference map of MSCs, and we identified ∼30 proteins with an increase or decrease in expression or phosphorylation in response to TGF-β. The proteins regulated by TGF-β included cytoskeletal proteins, matrix synthesis proteins, membrane proteins, metabolic enzymes, etc. TGF-β increased the expression of smooth muscle α-actin and decreased the expression of gelsolin. Overexpression of gelsolin inhibited TGF-β-induced assembly of smooth muscle α-actin; on the other hand, knocking down gelsolin expression enhanced the assembly of α-actin and actin filaments without significantly affecting α-actin expression. These results suggest that TGF-β coordinates the increase of α-actin and the decrease of gelsolin to promote MSC differentiation. This study demonstrates that proteomic tools are valuable in studying stem cell differentiation and elucidating the underlying molecular mechanisms.