Cell proliferation and by association the increase in the number of cells is an extensively studied process involved in embryonic development, regeneration and also disease states such as cancer. However, the processes that regulate cell growth and the accumulation of biomass are less defined. 

The interactions between cell proliferation and cell growth pathways are complex but these processes operate independently under certain conditions. Cells can grow without dividing in the case of muscle cell hypertrophy whilst cells can proliferate without growing when an embryo undergoes cleavage.

Abnormal accumulation of cell mass has been implicated in several diseases including cardiac hypertrophy and tuberous sclerosis. Aberrant regulation of cell growth has also been linked to cell ageing and senescence. These recent observations highlight that a greater understanding of the pathways regulating cell growth may yield new treatment options and strategies for diseases. 

Cell confluence and cell counting measurements through traditional image analysis are common approaches in cell proliferation assays. The accuracy of the former in influenced by changes in cell area in response to compounds whilst the latter risks altered cell behaviour through phototoxicity if fluorescent labels are introduced to augment cell segmentation. Notwithstanding these potential limitations, traditional imaging techniques do not reliably report changes in cell growth, and specifically biomass, at an individual cell level.

Livecyte leverages Ptychography, a quantitative phase imaging (QPI) technique, to produce high contrast images without the need for fluorescent labels. The enhanced contrast enables automatic segmentation and tracking of individual cells, as well as a quantitative measure of cellular dry mass. Livecyte therefore can fully characterise the single-cell phenotypic behaviour of whole populations.

In this study we sought to examine cell proliferation and cell growth, independently, in response to labelling with the live cell fluorescence label, SiR-DNA, through Livecyte's label-free QPI mode and Analyse Software.