Quantifying cellular differentiation by physical phenotype using digital holographic microscopy

Although the biochemical changes that occur during cell differentiation are well-known, less known is that there are significant, cell-wide physical changes that also occur. Understanding and quantifying these changes can help to better understand the process of differentiation as well as ways to monitor it. Digital holographic microscopy (DHM) is a marker-free quantitative phase microscopy technique for measuring biological processes such as cellular differentiation, alleviating the need for introduction of foreign markers. We found significant changes in subcellular structure and refractive index of differentiating myeloid precursor cells within one day of differentiation induction, and significant differences depending on the type of lineage commitment. We augmented our results by showing significant changes in the softness of myeloid precursor cell differentiation within one day using optical stretching, a laser trap-based marker-free technique. DHM and optical stretching therefore provide consequential parameterization of cellular differentiation with sensitivity otherwise difficult to achieve. Therefore, we provide a way forward to quantify and understand cell differentiation with minimal perturbation using biophotonics.