The mechanical strength of mammalian cells during mitotic cell division

Recently we have shown that exposure of animal cells to intense hydrodynamic forces can result in preferential destruction of S and G2 cells (Al-Rubeai et al 1995b). To further understand the interactions between cell cycle events and the physical environmental factors in large scale bioreaction processes, thereby providing terms for adequate process optimisation, we have evaluated the possible role of mitotic dependent features in shear sensitivity. Synchronised and unsynchronised cultures were exposed to intense hydrodynamic forces exerted in capillary now and the reduction in interphase and mitotic cells was monitored by flow cytometry and fluorescence microscopy. Destruction of mitotic cells was significantly higher than interphase cells. Cells from the exponential phase of CHO 320 batch cultures, where the percentage of mitotic cells was 5.2%, was almost entirely destroyed by the laminar flow. At this relatively low stress level, passing of synchronised cells 25 times through the capillary tube resulted in 46% reduction in cell number, respectively. In such conditions, the proportion of G2/mitotic cells (measured by flow cytometry) was reduced from 37.9% to 18.1%, while the mitotic cells (measured by fluorescent microscopy) was reduced from 8.9% to 1%.