Laboratory of Rheumatology, GIGA-I3, GIGA Research Centre, University and CHU of Liège, Liège, Belgium.
Stem Cells Dev. 2012 Jul 20;21(11):1948-55. doi: 10.1089/scd.2011.0321. Epub 2011 Dec 23.
Leptin plays a central role in maintaining energy balance, with multiple other systemic effects. Despite leptin importance in peripheral regulation of mesenchymal stem cells (MSC) differentiation, little is known about its expression mechanism. Leptin is often described as adipokine, while it is expressed by other cell types. We have recently shown an in vitro leptin expression, enhanced by glucocorticoids in synovial fibroblasts (SVF). Here, we investigated leptin expression in MSC from bone marrow (BM-MSC) and umbilical cord matrix (UMSC). Results showed that BM-MSC, but not UMSC, expressed leptin that was strongly enhanced by glucocorticoids. Transforming growth factor β1 (TGF-β1) markedly inhibited the endogenous- and glucocorticoid-induced leptin expression in BM-MSC. Since TGF-β1 was shown to signal via ALK-5-Smad2/3 and/or ALK-1-Smad1/5 pathways, we analyzed the expression of proteins from both pathways. In BM-MSC, TGF-β1 increased phosphorylated Smad2 (p-Smad2) expression, while ALK-5 inhibitor (SB431542) induced leptin expression and significantly restored TGF-β1-induced leptin inhibition. In addition, both prednisolone and SB431542 increased p-Smad1/5 expression. These results suggested the ALK-5-Smad2 pathway as an inhibitor of leptin expression, while ALK-1-Smad1/5 as an activator. Indeed, Smad1 expression silencing induced leptin expression inhibition. Furthermore, prednisolone enhanced the expression of TGF-βRII while decreasing p-Smad2 in BM-MSC and SVF but not in UMSC. In vitro differentiation revealed differential osteogenic potential in SVF, BM-MSC, and UMSC that was correlated to their leptin expression potential. Our results suggest that ALK-1/ALK-5 balance regulates leptin expression in MSC. It also underlines UMSC as leptin nonproducer MSC for cell therapy protocols where leptin expression is not suitable.
瘦素在维持能量平衡方面起着核心作用，同时还具有多种其他全身效应。尽管瘦素在间充质干细胞（MSC）分化的外周调节中很重要，但对其表达机制知之甚少。瘦素通常被描述为脂肪因子，但它也由其他细胞类型表达。我们最近已经证明，滑膜成纤维细胞（SVF）中的糖皮质激素可增强体外的瘦素表达。在这里，我们研究了骨髓（BM-MSC）和脐带基质（UMSC）中的 MSC 中的瘦素表达。结果表明，BM-MSC 表达瘦素，而 UMSC 不表达，糖皮质激素可强烈增强其表达。转化生长因子β1（TGF-β1）显著抑制 BM-MSC 中内源性和糖皮质激素诱导的瘦素表达。由于 TGF-β1 通过 ALK-5-Smad2/3 和/或 ALK-1-Smad1/5 途径发出信号，我们分析了两条途径的蛋白表达。在 BM-MSC 中，TGF-β1 增加了磷酸化 Smad2（p-Smad2）的表达，而 ALK-5 抑制剂（SB431542）诱导了瘦素的表达，并显著恢复了 TGF-β1 诱导的瘦素抑制。此外，泼尼松龙和 SB431542 均增加了 p-Smad1/5 的表达。这些结果表明，ALK-5-Smad2 途径是瘦素表达的抑制剂，而 ALK-1-Smad1/5 途径是其激活剂。实际上，Smad1 表达沉默可抑制瘦素表达。此外，泼尼松龙增强了 BM-MSC 和 SVF 中 TGF-βRII 的表达，同时降低了 p-Smad2 的表达，但在 UMSC 中则没有。体外分化显示 SVF、BM-MSC 和 UMSC 具有不同的成骨潜能，这与其瘦素表达潜能相关。我们的结果表明，ALK-1/ALK-5 平衡调节 MSC 中的瘦素表达。它还强调了 UMSC 作为不适合细胞治疗方案的不产生瘦素的 MSC。
