12月6日，Cell Research在线发表了中科院上海生科院健康所杨黄恬研究组的研究成果，研究人员在诱导多能干细胞向心肌细胞分化研究方面取得新进展。
诱导多能干细胞（induced pluripotent stem cells, iPSCs）分化的心肌细胞对于药物筛选、心肌再生医学及其心脏发育生物学的研究均具有重要意义，并是研究人类心脏疾病提供了独特的体外模型。然而iPSCs的自发心肌细胞分化效率极低且分化的心肌细胞功能也相对的不成熟，各系之间的分化潜能差异大，因此，明确其定向分化的关键环节和调控机制，并建立稳定高效、经济简便地诱导iPSCs分化为所需的功能心肌细胞是研究其应用价值的关键前提之一。
健康科学研究所、中国科学院干细胞生物学重点实验室分子心脏学课题组的博士研究生曹楠等在杨黄恬研究员的指导下，采用中科院动物所、上海生命科学院生化与细胞所、健康所、广州生物医药与健康院建立的11株不同的iPSCs系统筛选了16种心肌细胞分化诱导物，发现只有抗坏血酸(ascorbic acid, AA) 表现出一致和高效的诱导iPSCs向心肌细胞分化作用。通过比较不同浓度和不同分化时段AA的处理，建立了简单经济的高效诱导iPSCs向心肌细胞分化的体系，可将小鼠和人iPSCs向心肌细胞的分化效率分别提高了约7.3倍和30.2倍，并明显缩小了不同iPSCs系间，包括不具有自发心肌细胞分化潜能的iPSCs间心肌细胞的分化差异。进一步的机制研究发现，AA促进心肌细胞分化作用是通过增强胞外胶原的分泌，从而激活MEK-ERK1/2 pathway，进而特异性地促进心肌前体细胞增殖而实现的。
此外，通过结构和功能分析发现，AA诱导产生的心肌细胞表现出更为成熟的电活动和钙活动特征，其肌丝排列更为规律有序，对于重要的心肌细胞功能调控信号的反应性也明显增强，表明AA促进了iPSCs分化的心肌细胞的成熟度。该研究发现进一步揭示了细胞外微环境对于多能干细胞向心肌细胞分化和心肌前体细胞的增殖具有重要的调控作用，所建立的简便经济的高效诱导小鼠和人iPSCs向心肌细胞分化的体系，有助于iPSCs在心脏疾病发生、药物筛选以及心脏再生医学方面的应用研究。（生物谷Bioon.com）
doi:10.1038/cr.2011.195
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Ascorbic acid enhances the cardiac differentiation of induced pluripotent stem cells through promoting the proliferation of cardiac progenitor cells
Nan Cao, Zumei Liu, Zhongyan Chen, Jia Wang, Taotao Chen, Xiaoyang Zhao, Yu Ma, Lianju Qin, Jiuhong Kang, Bin Wei, Liu Wang, Ying Jin and Huang-Tian Yang
Generation of induced pluripotent stem cells (iPSCs) has opened new avenues for the investigation of heart diseases, drug screening and potential autologous cardiac regeneration. However, their application is hampered by inefficient cardiac differentiation, high interline variability, and poor maturation of iPSC-derived cardiomyocytes (iPS-CMs). To identify efficient inducers for cardiac differentiation and maturation of iPSCs and elucidate the mechanisms, we systematically screened sixteen cardiomyocyte inducers on various murine (m) iPSCs and found that only ascorbic acid (AA) consistently and robustly enhanced the cardiac differentiation of eleven lines including eight without spontaneous cardiogenic potential. We then optimized the treatment conditions and demonstrated that differentiation day 2-6, a period for the specification of cardiac progenitor cells (CPCs), was a critical time for AA to take effect. This was further confirmed by the fact that AA increased the expression of cardiovascular but not mesodermal markers. Noteworthily, AA treatment led to approximately 7.3-fold (miPSCs) and 30.2-fold (human iPSCs) augment in the yield of iPS-CMs. Such effect was attributed to a specific increase in the proliferation of CPCs via the MEK-ERK1/2 pathway by promoting collagen synthesis. In addition, AA-induced cardiomyocytes showed better sarcomeric organization and enhanced responses of action potentials and calcium transients to β-adrenergic and muscarinic stimulations. These findings demonstrate that AA is a suitable cardiomyocyte inducer for iPSCs to improve cardiac differentiation and maturation simply, universally, and efficiently. These findings also highlight the importance of stimulating CPC proliferation by manipulating extracellular microenvironment in guiding cardiac differentiation of the pluripotent stem cells.
