The widespread application of stem cells and stem cell derivatives as part of clinically applicable reparative/regenerative strategies will require the safe and efficient generation of vast numbers of cells. Unfortunately, traditional two-dimensional adherent culture systems for the expansion and differentiation of stem cells suffer from limitations that include restricted surface areas, intensive labor costs, and challenging control, monitoring, and automation processes that hinder scale-up attempts.^{1, 2} Stem cell expansion under a mixed and controlled culture environment within stirred-tank suspension bioreactors represents an exciting alternative that allows scalability without negatively impacting quality attributes^{3, 4}; furthermore, bioreactor culture set-ups permit the comprehensive monitoring and control of parameters such as temperature, pH, and dissolved oxygen. While the bioreactor culture of stem cells remains an efficient process, recent research has sought to significantly improve cell expansion by developing novel subculturing techniques and delineating those mechanisms that support the maintenance of stem cell characteristics under hydrodynamic conditions. In the first of our Featured Articles published this month in STEM CELLS Translational Medicine, Chen et al⁵ report on the development of a bead-to-bead cell transfer process for human mesenchymal stem cell (MSC) subculture in stirred-tank bioreactors that permits the expansion of cells while maintaining proliferation, viability, and a normal phenotype. In a Related Article recently published online at STEM CELLS, Nath et al described how the fluid shear stress generated in stirred-tank bioreactors supports the pluripotency of mouse embryonic stem cells (ESCs) through a pathway involving the translocation of β-catenin from adherens junction to the nucleus and the induced expression of pluripotency-associated genes.⁶

The ongoing development of therapies that rely on the large-scale derivation, expansion, and/or differentiation of a range of stem cell types will also require the implementation of quality control mechanisms to ensure both safety and efficacy post-administration/transplantation. While approaches to evaluate safety and functionality currently exist or are undergoing development at the small scale, their widespread use and/or adaptation to larger-scale cultures suffers from problems related to their high complexity, difficult standardization, and elevated cost. The analysis of cell morphology and dynamic behavior represents one of the most relevant alternate approaches, and this strategy has become particularly relevant with the introduction of live-cell imaging coupled with video bioinformatics analysis of time-lapse data, which permits the quantitative and noninvasive quality control monitoring of stem cell cultures.^{7, 8} Examples include a study by Wong et al,⁹ who employed noninvasive imaging to predict the successful development of two-cell human embryos into blastocysts, and a study from Chan et al, who applied live cell imaging to identify those colonies most likely to give rise to bona fide induced pluripotent stem cells (iPSCs) during reprogramming.¹⁰ In the second of our Featured Articles published this month in STEM CELLS Translational Medicine, Lin et al¹¹ present StemCellQC, a label-free video bioinformatics analysis tool for the in vitro evaluation of pluripotent stem cell morphology and dynamics, as an effective quality control methodology that can be adapted to large scale stem cell culture. In a Related Article published this month in STEM CELLS, Li et al¹² demonstrated the application of a patch-clamp technique to establish electrophysiological features as a reliable and sensitive quality control indicator for the therapeutically relevant cells within developing stem cell-derived retinal organoids.

作为临床适用的修复/再生策略的一部分，干细胞和干细胞衍生物的广泛应用将需要安全有效地产生大量细胞。不幸的是，用于干细胞扩增和分化的传统二维贴壁培养系统受到限制，包括受限的表面积、密集的劳动力成本，以及阻碍扩大规模尝试的具有挑战性的控制、监测和自动化过程。^{1, 2}搅拌罐悬浮生物反应器内混合和受控培养环境下的干细胞扩增代表了一种令人兴奋的替代方案，它允许可扩展性而不会对质量属性产生负面影响^{3, 4}; 此外，生物反应器培养装置允许对温度、pH 和溶解氧等参数进行全面监测和控制。虽然干细胞的生物反应器培养仍然是一个有效的过程，但最近的研究试图通过开发新的继代培养技术和描述在流体动力学条件下支持维持干细胞特性的机制来显着改善细胞扩增。在我们本月发表在STEM CELLS Translational Medicine上的第一篇专题文章中，Chen 等人⁵报告了在搅拌罐生物反应器中人间充质干细胞 (MSC) 继代培养的珠对珠细胞转移过程的发展，该过程允许细胞扩增，同时保持增殖、活力和正常表型。在最近在线发表于STEM CELLS的一篇相关文章中，Nath 等人描述了搅拌罐生物反应器中产生的流体剪切应力如何通过涉及 β-连环蛋白从粘附连接处易位的途径支持小鼠胚胎干细胞 (ESC) 的多能性细胞核和多能性相关基因的诱导表达。⁶

依赖于一系列干细胞类型的大规模衍生、扩增和/或分化的疗法的持续发展也将需要实施质量控制机制，以确保给药/移植后的安全性和有效性。虽然评估安全性和功能性的方法目前存在或正在小规模开发，但它们的广泛使用和/或适应更大规模的文化存在与其高复杂性、难以标准化和高成本相关的问题。细胞形态和动态行为的分析代表了最相关的替代方法之一，这种策略与引入活细胞成像以及延时数据的视频生物信息学分析特别相关，^{7, 8}示例包括 Wong 等人⁹的一项研究，他们使用无创成像来预测人类双细胞胚胎成功发育成囊胚，以及 Chan 等人的一项研究，他们使用活细胞成像来识别最有可能的菌落在重编程过程中产生真正的诱导多能干细胞（iPSC）。¹⁰在我们本月发表在STEM CELLS Translational Medicine上的第二篇专题文章中，Lin 等人¹¹目前 StemCellQC，一种用于体外评估多能干细胞形态和动力学的无标记视频生物信息学分析工具，作为一种有效的质量控制方法，可适用于大规模干细胞培养。在本月发表在STEM CELLS上的一篇相关文章中，Li 等人¹²展示了膜片钳技术的应用，以建立电生理特征，作为开发干细胞衍生的视网膜类器官中治疗相关细胞的可靠和敏感的质量控制指标。