Chapter 3: Screening Approaches for Stem Cells

Cell screening, the process of distinguishing one cell type from another, is particularly essential for stem cells as cell genotype, phenotype and function can change rapidly and unpredictably over time.  Initial stem cell characterization efforts were derived primarily from cell biology techniques that were limited in throughput and content and did not typically maintain cellular integrity.  More recently, high-throughput techniques including gene or protein arrays, flow cytometry and robotic-based assaying and high-content type techniques including imaging flow cytometry have been developed to more efficiently and comprehensively screen stem cells.  However these approaches still rely on sample manipulation to gain information beyond morphology and are incapable of analyzing intact cell aggregates or tissues – structures known to be crucial for the maintenance of stem cell state.  To address these limitations, multiphoton laser scanning microscopy, an imaging modality capable of deep sample penetration at high resolution and sensitivity, has been coupled to imaging flow cytometry systems to assay intrinsic fluorescent properties of intact multicell aggregates.  Future advances in stem cell screening will likely follow this trend – the coupling of advanced imaging techniques to high throughput/high content modalities – to generate a panel of screening approaches capable of providing not only spatial and temporal information but also physical and chemical properties of cells and their microenvironment in a rapid and noninvasive manner.  In this way, stem cell screening might be advanced beyond the identification of cell state to the determination of likely cell function.