Engineering at the microscale: A step towards single‐cell analysis of human pluripotent stem cells
See accompanying article by Darek J. Sikorski et al. DOI: 10.1002/biot.201500035
Recent advances in biomedical research have led to an increasing relevance in the use of cells as prime therapeutic vectors in clinical settings, and also as models for drug discovery. In particular, the use of human stem cells, both embryonic and adult, has become of great interest in applications as diverse as pharmacological testing and regenerative medicine [1]. But despite the advances in the field, important hurdles must be overcome before stem cells can be widely used for such applications. One particular problem is that stem cells and their derivatives display heterogeneity as they expand or differentiate in microenvironments or specialized niches, both in vivo and in vitro [2, 3]. This heterogeneity is hard to study using standard analytical methods and to fully realize the potential of these cells for clinical uses a complete understanding of stem cell population dynamics is needed.
Human embryonic stem cells (hESCs) in particular are capable to differentiate into precursors of the three embryonic germ layers, and therefore can be seen as an unlimited source of cells for research and therapeutic applications [4]; however, just like with other stem cell populations, hESCs and their derivatives display heterogeneity, which can affect the fate of their progeny and ultimately result in incompletely differentiated cells carrying the risk of tumorigenesis upon implantation.
In this context, microscale technologies are very fitting to produce platforms capable to control different aspects of the stem cell niche, and also compatible with automated live‐cell analysis [5]. Microfluidic platforms in particular can provide more information from smaller sample volumes, while enabling the incorporation of low‐cost, high‐content analysis capabilities (Fig. 1). In this issue, Sikorski and coworkers [6]describe a microfluidic device that allows multiparameter analysis of hESC heterogeneity at a clonal level. By coupling the advantages and functionality of microscale cell culture with time‐lapse microscopy, the authors demonstrate fluctuations in OCT4 transcript levels and the emergence of an OCT4 negative subpopulation associated with a more reduced growth rate and a less compact cell morphology, which may potentially correlate with a loss of the pluripotency state. These results have been attained by the precise design and engineering of the platform, which enables the tracking of single‐cell proliferation, morphology and transcript levels upon recovery of the cells for downstream analyses. Other functionalities of this system also include dynamic and automated scheduling of medium perfusion and cell loading.
A microfluidic culture device for high‐content analysis of individual human embryonic stem cells. In this issue, Sikorski and coworkers describe a microfluidic platform that allows multiparameter analysis of hESC at a clonal level. The microfluidic unit is coupled with time‐lapse microscopy and automated operation. This design allows the tracking of single‐cell proliferation and morphology, together with off‐line gene expression analysis upon recovery of the cells. This Figure was produced using Servier Medical Art.
By addressing these questions, the authors expose an important bottleneck in stem cell research and deliver a substantial improvement in our ability to evaluate individual human embryonic stem cells. The use of microtechnologies and bioengineering approaches to tackle such issues is very relevant, not only in the context of stem cell biology, but also to a wide range of related applications where analyses of variable subpopulation responses are needed. These will most likely include the control of stem cells for regenerative medicine, and to guide process development for stem cell expansion and controlled differentiation. Other potential applications include the design of protein therapeutics, drug candidate evaluation and toxicity screening for the pharmaceutical industry. In conclusion, the present study highlights the potential of microscale technologies for biological studies, not only to reproduce the intricate architecture of the cellular niche, but also to evaluate cellular properties at a clonal level.
Acknowledgements
Dr. Tiago G. Fernandes acknow‐ledges support from Fundação para a Ciência e a Tecnologia (FCT), Portugal (SFRH/BPD/86316/2012).
The author declares no financial or commercial conflict of interest.
