Mesenchymal stem cells (MSCs) can differentiate into diverse cell types including adipogenic, osteogenic, chondrogenic,
and myogenic lineages. In the present study, we demonstrated for the first time that sphingosylphosphorylcholine (SPC) induces differentiation of human adipose tissue-derived mesenchymal stem cells (hATSCs) to smooth muscle-like cell types. By using Western blotting or RT-PCR analysis, we demonstrated that treatment of hATSCs with SPC increased the expression levels of several smooth muscle-specific genes, such as α-smooth muscle actin (α-SMA), h1-calponin, and SM22α, and that it was as potent as TGF-β1 and -β3. SPC elicited delayed phosphorylation of Smad2 with a peak on the 2nd day, in contrast to rapid phosphorylation of Smad2 within minutes of TGF-β treatment. Pretreatment of the cells with PTX and U0126, an MEK inhibitor, markedly attenuated the SPC-induced expression of α-SMA and delayed phosphorylation of Smad2, suggesting that the Gi/o-ERK pathway is involved in the increased expression of α-SMA through induction of delayed Smad2 activation. In addition, SPC increased secretion of TGF-β1 through ERK-dependent pathway, and the SPC-induced expression of α-SMA and delayed phosphorylation of Smad2 were blocked by SB-431542, a TGF-β type Ⅰreceptor kinase inhibitor, or anti-TGF-β1 neutralizing antibody, suggesting that SPC-stimulated secretion of TGF-β1 plays a crucial role in SPC-induced SMC differentiation. Both SPC and TGF-β increased the expression levels of serum response factor (SRF) and myocardin, transcription factors involved in smooth muscle differentiation. Short interfering RNAs (si-RNA), which are specific for SRF or myocardin, abolished the α-SMA expression induced by SPC or TGF-β. These results suggest that SPC treatment induces hATSCs difference to smooth muscle-like cell types through the Gi/o-ERK-dependent autocrine secretion of TGF-β, which activated Smad2-SRF/myocardin-dependent pathway.
Source: Korean J Physiol Pharmacol.2006 Oct;10(Suppl II):243
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