Using Label-Free Screening to Investigate Stem-Cells from their Microanatomical Niche

Abstract

An understanding of both embryonic organogenesis and adult tissue regeneration relies on isolating and characterizing stem cells. In general, these cells are difficult to study because they constitute minute populations in organ niches and express multiple cell-surface markers, only some of which are identified. Furthermore, their properties change quickly in vitro and possibly even during isolation procedures. We have recently developed a label-free cell-analysis platform to characterize key cell-surface markers in single, functional organ stem cells directly isolated from their micro-anatomical niche, i.e. muscle (satellite) stem cells from single myofibers. Our platform is based on measuring the transit time of single cells as they transit a microchannel functionalized with a specific antibody. Cells that express the complementary surface antigen have a longer transit time as compared to those that do not. With this method, we have discovered that individual myofibers significantly differ from each other with respect to expression of the markers Sca-1, CXCR4, β1-integrin, and M-cadherin on their associated satellite cells. Furthermore, we have found that this heterogeneity extends to other important markers such as Notch1. Our data are the first to show the phenomenon of microniche-dependent variation in adult stem cells of the same tissue, emphasizing the complexity of the muscle stem-cell population and prompting new studies aimed at understanding the purpose for such heterogeneity. Ultimately, our platform introduces a new method for stem-cell analysis, as FACS and MACS do not allow for niche-specific characterization. Microscopy, while capable of imaging stem cells in their respective niches, is neither precise nor quantitative. Overall, our method can be broadly applied to the quantitative analysis of single stem cells isolated from their microniches in other adult and developing organs, leading to new discoveries on stem-cell properties and regenerative potential.