3月25日，国际著名学术期刊《The Journal of Clinical Investigation》在线发表了交通大学医学院基础研究院分子发育生物学研究室金颖课题组与同济大学医学院徐国彤课题组合作完成的题为“WNT signaling determines tumorigenicity and function of ESC-derived retinal progenitors”的最新研究成果。论文首次报道了canonical Wnt信号通路通过调控Tcf7,影响Sox2和Nestin的表达水平，最终决定胚胎干细胞来源的视网膜前体细胞眼内移植后的疗效和肿瘤形成。
视网膜变性疾病，是一类以光感受器和视网膜色素上皮细胞变性和功能丧失导致视功能损害为共同表现，以视网膜细胞的凋亡为重要病理特征的致盲性眼病。据统计，目前世界上约有超过2千万人患有各种视网膜变性类疾病，是成年人的主要致盲原因。但目前,这类疾病尚没有有效的治疗手段。虽然已有的报道证实了来自小鼠新生儿的视网膜前体细胞(retinal progenitor cells, RPCs)移植治疗视网膜变性类疾病的安全性和有效性,但是来源亏缺限制了其应用。胚胎干细胞(embryonic stem cells, ESCs)是胚胎着床前囊胚期的内细胞团在体外特定培养条件下建立的细胞系,能够分化成为各种类型的细胞,这使得它们具有巨大的研究价值,并可为临床提供充足的细胞来源。但是,ESCs的发育全能性和持续的自我更新能力,也使得细胞移植的安全性特别引起人们的关注。如何将ESC在体外诱导分化为既能有效地修复损伤，又不具有成瘤危险的状态是成功地应用干细胞治疗疾病所面临的关键问题。
博士研究生崔璐、管圆利用视网膜变性小鼠模型移植实验，结合全转录本芯片的检测,发现 canonical Wnt 通路在胚胎干细胞来源的视网膜前体细胞（ESC-RPCs）中的异常激活及在调控治疗效果和肿瘤形成中的关键作用。他们的研究证明，在细胞移植前，应用Wnt抑制剂处理ESC-RPC能显著地提高移植细胞对动物视力的保护作用和减少移植细胞引起的肿瘤形成。在针对 canonical Wnt 通路对 ESC-RPCs 的分化和致瘤性的调控作用及其机制的深入研究中, 他们发现canonical Wnt 通路的下游Tcf7,直接调控Sox2和Nestin的表达水平从而参与调控神经分化和肿瘤形成的过程。当在ESC-RPCs中,沉默Tcf7 或Sox2 或Nestin都能够有效地降低肿瘤的发生率,同时提高供体细胞的整合及宿主视功能的恢复。该研究首次证明Wnt-Tcf7-Sox2-Nestin信号通路在调控ESC-RPC移植后的整合和肿瘤形成中的重要作用，也为临床上移植 ESC 来源的细胞治疗视网膜变性类疾病和其它神经退行性疾病奠定了重要的基石。该研究被JCI选为封面论文，并有评论文章在同期发表。
该课题获得国家科技部、国家自然科学基金委及中国科学院先导项目的经费资助。（生物谷Bioon.com)
doi:10.1172/JCI65048
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WNT signaling determines tumorigenicity and function of ESC-derived retinal progenitors
Lu Cui1,2,3, Yuan Guan1,2, Zepeng Qu1,3, Jingfa Zhang2, Bing Liao1,3, Bo Ma4, Jiang Qian4, Dangsheng Li5, Weiye Li6, Guo-Tong Xu2 and Ying Jin1,3
The unique properties of embryonic stem cells (ESCs), unlimited self-renewal and pluripotency, make them an attractive cell source for the treatment of various degenerative diseases. However, the same properties also present a major hurdle for their clinical application. Tumor formation has been reported in the transplantation of ESC derivatives despite predifferentiation or presorting (1–6), raising a safety concern for the therapeutic use of ESC-derived cell products in humans. On the other hand, transplantation of photoreceptor precursors in neonatal mice repaired retinal defect efficiently without development of any tumors (7, 8), which emphasizes the critical role of the developmental stage of donor cells in determining the cell fate following transplantation. Thus, steering ESCs to an appropriate state could be an important step for safe and effective cell therapies.
To date, ESCs from the mouse, monkey, and human have been successfully differentiated into retinal cells in vitro (9–13). Sasai’s group developed an efficient induction of retinal precursors by culturing mouse ESCs under a serum-free suspension condition (SFEB culture) and obtained high percentages of differentiated cells expressing key eye-field transcription factors (12–14). However, mechanisms governing efficient generation of various types of retinal cells and the optical cups from ESCs in vitro as well as their application potential in vivo, in regards to the functional integration and safety, are not clearly elucidated.
In an attempt to find major extracellular signaling and intrinsic factors controlling tumorigenicity and therapeutic effects of ocular transplanted ESC-derived retinal progenitor cells (ESC-RPCs), we identified the canonical WNT signaling-activated TCF7-SOX2-NESTIN cascade as a critical determinant for the consequence of ESC-RPC transplantation: whether tumors would form as well as whether successful integration into the host retina and prevention of the visual defect would be achieved. Canonical WNT signaling is known to play a key role in cell fate determination for various cell lineages, and its inappropriate activation is frequently associated with cancers (15–17). It has also been shown to promote proliferation of isolated retinal stem cells (18) and retina regeneration in adult mammals (19). However, the correlation between WNT signaling in ESC-derived donor cells and their therapeutic effect as well as tumorigenicity after transplantation in a disease model remains unexamined. In addition, factor(s) that mediate the function of WNT signaling in the control of cell fate commitment remain elusive. In this study, we link the activity of WNT signaling to the tumorigenic potential of ESC-RPCs and provide the experimental evidence for transcriptional factor TCF7 to regulate expression of SOX2 and NESTIN, two important genes actively engaged in the neural development and tumor formation. The tumorigenic and therapeutic effect of transplanted ESC-RPCs is determined in a well-studied sodium iodate–induced (SI-induced) mouse retinal degeneration model (20, 21). We also show that the expression of TCF7, SOX2, and NESTIN is closely associated in mouse neonatal retinae. These findings open new avenues to define and manipulate ESC-derived donor cells prior to transplantation for safe and effective cell therapies.
