We earlier published that exchange of plasma membrane and cytoplasm between fibroblasts and malignant cells in co-culture, correlates with changes in cell morphology and cytokine release (David et al. 2012, 2013, 2014). Our as yet unpublished work with FACS cell sorted cells, has correlated malignant cell uptake of cytoplasm from fibroblasts, with increased migration and reduced proliferation of malignant cells. Experiments with cells isolated by FACS are inherently limited by cell pooling effects, with particular bearing on the current work, through dilution of exchanged fibroblast marker by tumour cell division. We here describe the results of preliminary work seeking to overcome this difficulty, by use of single cell tracking in time-lapse microscopy.
In brief, human dermal fibroblasts pre-labelled with the fluorescent lipophilic marker DiD, were co-cultured with SAOS-2 osteosarcoma cells pre-labelled with the fluorescent lipophilic marker DiO. Phase contrast and fluorescent images for both fluorescent markers were collected at 15 minute intervals for 48 hours. Contiguous visual fields were digitally stitched together for cell tracking analysis using Nordan cell tracking controller software developed by RN. Data for individual cells tracked included: migration velocity, time of division, time of apoptosis if appropriate, cell surface profile area, shape, DiO fluorescence, and DiD fluorescence.
Preliminary analysis confirms increased migration velocity in SAOS-2 following the uptake of DiD marker from fibroblasts, consistent with earlier work with pooled cell populations isolated by FACS. Also consistent with earlier studies, was increased cell surface profile area and reduced cell circularity in SAOS-2 with fibroblast labelling. Increased SAOS-2 division was seen following uptake of fibroblast marker, opposite to earlier results with pooled cell populations isolated by FACS, and underscoring the value of the single cell analysis approached used.