Nutritional Research Center, The Children's Hospital of Chongqing Medical University, Chongqing, China.
Dev Growth Differ. 2010 Jun;52(5):419-31. doi: 10.1111/j.1440-169X.2010.01182.x.
Mesenchymal stem cells (MSCs) can differentiate into neurons in an appropriate cellular environment. Retinoid signaling pathway is required in neural development. However, the effect and mechanism through retinoid signaling regulates neuronal differentiation of MSCs are still poorly understood. Here, we report that all-trans-retinoic acid (ATRA) pre-induction improved neuronal differentiation of rat MSCs. We found that, when MSCs were exposed to different concentrations of ATRA (0.01-100 micromol/L) for 24 h and then cultured with modified neuronal induction medium (MNM), 1 micromol/L ATRA pre-induction significantly improved neuronal differentiation efficiency and neural-cell survival. Compared with MNM alone induced neural-like cells, ATRA/MNM induced cells expressed higher levels of Nestin, neuron specific enolase (NSE), microtubule-associated protein-2 (MAP-2), but lower levels of CD68, glial fibrillary acidic protein (GFAP), and glial cell line-derived neurotrophic factor(GDNF), also exhibited higher resting membrane potential and intracellular calcium concentration, supporting that ATRA pre-induction promotes maturation and function of derived neurons but not neuroglia cells from MSCs. Endogenous retinoid X receptors (RXR) RXRalpha and RXRgamma (and to a lesser extent, RXRbeta) were weakly expressed in MSCs. But the expression of RARalpha and RARgamma was readily detectable, whereas RARbeta was undetectable. However, at 24 h after ATRA treatment, the expression of RARbeta, not RARalpha or RARgamma, increased significantly. We further found the subnuclear redistribution of RARbeta in differentiated neurons, suggesting that RARbeta may function as a major mediator of retinoid signaling during neuronal differentiation from MSCs. ATRA treatment upregulated the expression of Vimentin and Stra13, while it downregulated the expression of Brachyury in MSCs. Thus, our results demonstrate that pre-activation of retinoid signaling by ATRA facilitates neuronal differentiation of MSCs.
间质干细胞（MSCs）可以在适当的细胞环境中分化为神经元。视黄酸信号通路在神经发育中是必需的。然而，视黄酸信号调节 MSCs 神经元分化的作用和机制仍知之甚少。在这里，我们报告全反式视黄酸（ATRA）预诱导可提高大鼠 MSCs 的神经元分化。我们发现，当 MSCs 暴露于不同浓度的 ATRA（0.01-100 μmol/L）24 小时，然后用改良的神经元诱导培养基（MNM）培养时，1 μmol/L ATRA 预诱导可显著提高神经元分化效率和神经细胞存活率。与单独的 MNM 诱导的神经样细胞相比，ATRA/MNM 诱导的细胞表达更高水平的巢蛋白、神经元特异性烯醇化酶（NSE）、微管相关蛋白-2（MAP-2），而表达更低水平的 CD68、胶质纤维酸性蛋白（GFAP）和胶质细胞系源性神经营养因子（GDNF），也表现出更高的静息膜电位和细胞内钙浓度，表明 ATRA 预诱导促进 MSCs 来源神经元的成熟和功能，但不促进神经胶质细胞。内源性视黄酸 X 受体（RXR）RXRalpha 和 RXRgamma（以及在较小程度上，RXRbeta）在 MSCs 中弱表达。但是 RARalpha 和 RARgamma 的表达是可检测的，而 RARbeta 是不可检测的。然而，在 ATRA 处理 24 小时后，RARbeta 的表达而非 RARalpha 或 RARgamma 显著增加。我们进一步发现 RARbeta 在分化神经元中的亚核重新分布，表明 RARbeta 可能是 MSCs 向神经元分化过程中视黄酸信号的主要介导物。ATRA 处理上调了 Vimentin 和 Stra13 的表达，同时下调了 MSCs 中 Brachyury 的表达。因此，我们的结果表明，ATRA 预先激活视黄酸信号可促进 MSCs 的神经元分化。
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