Advancing stem cell research with microtechnologies: opportunities and challenges.

Stem cells provide unique opportunities for understanding basic biology, for developing tissue models for drug testing, and for clinical applications in regenerative medicine. Despite the promise, the field faces significant challenges in identifying stem cell populations, controlling their fate, and characterizing their phenotype. These challenges arise because stem cells are ultimately functionally defined, and thus can often be identified only retrospectively. New technologies are needed that can provide surrogate markers of stem cell identity, can maintain stem cell state in vitro, and can better direct differentiation. In this review, we discuss the opportunities that microtechnologies, in particular, can provide to the unique qualities of stem cell biology. Microtechnology, by allowing organization and manipulation of cells and molecules at biologically relevant length scales, enables control of the cellular environment and assessment of cell functions and phenotypes with cellular resolution. This provides opportunities to, for instance, create more realistic stem cell niches, perform multi-parameter profiling of single cells, and direct the extracellular signals that control cell fate. All these features take place in an environment whose small size naturally conserves reagent and allows for multiplexing of experiments. By appropriately applying micro-scale engineering principles to stem cell research, we believe that significant breakthroughs can be made in stem cell research.