New York Medical College/Westchester Medical Center Stem Cell Laboratory, Department of Physiology, New York Medical College, Valhalla, New York, USA.
Stem Cells Dev. 2013 Feb 15;22(4):654-67. doi: 10.1089/scd.2012.0181. Epub 2012 Nov 7.
Bone marrow (BM) has long been considered a potential stem cell source for cardiac repair due to its abundance and accessibility. Although previous investigations have generated cardiomyocytes from BM, yields have been low, and far less than produced from ES or induced pluripotent stem cells (iPSCs). Since differentiation of pluripotent cells is difficult to control, we investigated whether BM cardiac competency could be enhanced without making cells pluripotent. From screens of various molecules that have been shown to assist iPSC production or maintain the ES cell phenotype, we identified the G9a histone methyltransferase inhibitor BIX01294 as a potential reprogramming agent for converting BM cells to a cardiac-competent phenotype. BM cells exposed to BIX01294 displayed significantly elevated expression of brachyury, Mesp1, and islet1, which are genes associated with embryonic cardiac progenitors. In contrast, BIX01294 treatment minimally affected ectodermal, endodermal, and pluripotency gene expression by BM cells. Expression of cardiac-associated genes Nkx2.5, GATA4, Hand1, Hand2, Tbx5, myocardin, and titin was enhanced 114, 76, 276, 46, 635, 123, and 5-fold in response to the cardiogenic stimulator Wnt11 when BM cells were pretreated with BIX01294. Immunofluorescent analysis demonstrated that BIX01294 exposure allowed for the subsequent display of various muscle proteins within the cells. The effect of BIX01294 on the BM cell phenotype and differentiation potential corresponded to an overall decrease in methylation of histone H3 at lysine9, which is the primary target of G9a histone methyltransferase. In summary, these data suggest that BIX01294 inhibition of chromatin methylation reprograms BM cells to a cardiac-competent progenitor phenotype.
骨髓（BM）一直被认为是心脏修复的潜在干细胞来源，因为它丰富且易于获取。尽管以前的研究已经从 BM 中产生了心肌细胞，但产量很低，远低于胚胎干细胞（ES）或诱导多能干细胞（iPSC）。由于多能细胞的分化难以控制，我们研究了是否可以在不使细胞多能化的情况下增强 BM 心脏的能力。从已证明有助于 iPSC 产生或维持 ES 细胞表型的各种分子的筛选中，我们确定 G9a 组蛋白甲基转移酶抑制剂 BIX01294 是将 BM 细胞转化为具有心脏能力的表型的潜在重编程剂。暴露于 BIX01294 的 BM 细胞显示出 brachyury、Mesp1 和 islet1 的表达显著升高，这些基因与胚胎心脏祖细胞有关。相比之下，BIX01294 处理对 BM 细胞的外胚层、内胚层和多能性基因表达的影响最小。当用 BIX01294 预处理 BM 细胞时，心脏相关基因 Nkx2.5、GATA4、Hand1、Hand2、Tbx5、myocardin 和 titin 的表达分别增强了 114、76、276、46、635、123 和 5 倍。用 Wnt11 作为心脏刺激剂处理时。免疫荧光分析表明，BIX01294 暴露允许随后在细胞内显示各种肌肉蛋白。BIX01294 对 BM 细胞表型和分化潜能的影响与组蛋白 H3 赖氨酸 9 上的组蛋白甲基化的总体减少相对应，这是 G9a 组蛋白甲基转移酶的主要靶标。总之，这些数据表明，BIX01294 抑制染色质甲基化将 BM 细胞重编程为具有心脏能力的祖细胞表型。
