Department of Biomedical Science, College of Medicine, The Catholic University of Korea, Seoul, Korea.
Cell Transplant. 2011;20(11-12):1855-66. doi: 10.3727/096368910X557236. Epub 2011 Mar 4.
The ability of mesenchymal stem cells (MSCs) to differentiate into neural cells makes them potential replacement therapeutic candidates in neurological diseases. Presently, overexpression of brain-derived neurotrophic factor (BDNF), which is crucial in the regulation of neural progenitor cell differentiation and maturation during development, was sufficient to convert the mesodermal cell fate of human umbilical cord blood-derived MSCs (hUCB-MSCs) into a neuronal fate in culture, in the absence of specialized induction chemicals. BDNF overexpressing hUCB-MSCs (MSCs-BDNF) yielded an increased number of neuron-like cells and, surprisingly, increased the expression of neuronal phenotype markers in a time-dependent manner compared with control hUCB-MSCs. In addition, MSCs-BDNF exhibited a decreased labeling for MSCs-related antigens such as CD44, CD73, and CD90, and decreased potential to differentiate into mesodermal lineages. Phosphorylation of the receptor tyrosine kinase B (TrkB), which is a receptor of BDNF, was increased significantly in MSC-BDNF. BDNF overexpression also increased the phosphorylation of β-catenin and extracellular signal-regulated kinases (ERKs). Inhibition of TrkB availability by treatment with the TrkB-specific inhibitor K252a blocked the BDNF-stimulated phosphorylation of β-catenin and ERKs, indicating the involvement of both the β-catenin and ERKs signals in the BDNF-stimulated and TrkB-mediated neural differentiation of hUCB-MSCs. Reduction of β-catenin availability using small interfering RNA-mediated gene silencing inhibited ERKs phosphorylation. However, β-catenin activation was maintained. In addition, inhibition of β-catenin and ERKs expression levels abrogated the BDNF-stimulated upregulation of neuronal phenotype markers. Furthermore, MSC-BDNF survived and migrated more extensively when grafted into the lateral ventricles of neonatal mouse brain, and differentiated significantly into neurons in the olfactory bulb and periventricular astrocytes. These results indicate that BDNF induces the neural differentiation of hUCB-MSCs in culture via the TrkB-mediated phosphorylation of ERKs and β-catenin and following transplantation into the developing brain.
间充质干细胞（MSCs）分化为神经细胞的能力使它们成为神经疾病潜在的替代治疗候选物。目前，在培养物中，过表达脑源性神经营养因子（BDNF）足以将人脐血源性间充质干细胞（hUCB-MSCs）的中胚层细胞命运转化为神经元命运，而无需专门的诱导化学物质。BDNF 过表达的 hUCB-MSCs（MSCs-BDNF）产生了更多的类神经元细胞，并且令人惊讶的是，与对照 hUCB-MSCs 相比，MSCs-BDNF 以时间依赖性方式增加了神经元表型标志物的表达。此外，MSCs-BDNF 表现出对与 MSCs 相关的抗原（例如 CD44、CD73 和 CD90）的标记减少，并且向中胚层谱系分化的潜力降低。BDNF 的受体酪氨酸激酶 B（TrkB）的磷酸化显著增加，TrkB 是 BDNF 的受体。BDNF 过表达还增加了β-连环蛋白和细胞外信号调节激酶（ERKs）的磷酸化。用 TrkB 特异性抑制剂 K252a 处理阻断 BDNF 刺激的β-连环蛋白和 ERKs 磷酸化，从而阻断 BDNF 刺激和 TrkB 介导的 hUCB-MSCs 神经分化，表明β-连环蛋白和 ERKs 信号均参与 BDNF 刺激和 TrkB 介导的 hUCB-MSCs 神经分化。使用小干扰 RNA 介导的基因沉默减少β-连环蛋白的可用性抑制了 ERKs 磷酸化。然而，β-连环蛋白的激活得以维持。此外，抑制β-连环蛋白和 ERKs 的表达水平消除了 BDNF 刺激的神经元表型标志物的上调。此外，MSCs-BDNF 在移植到新生小鼠大脑侧脑室后存活和迁移更广泛，并在嗅球和室周星形胶质细胞中显著分化为神经元。这些结果表明，BDNF 通过 TrkB 介导的 ERKs 和β-连环蛋白磷酸化诱导 hUCB-MSCs 在培养物中的神经分化，并在移植到发育中的大脑后进一步分化为神经元。
