Dynamics of Aggregate Culture of Mammalian Cells

Abstract

Many mammalian cells grow as aggregates when deprived of surface for attachment. Ease of cell retention and higher cell concentration are among the potential benefits of aggregate culture. We investigated the dynamics of aggregate formation by measuring the kinetics of growth and the particle size distributions. The formation of aggregates was dependent on the chemical environment. At low Ca^{+ +} concentrations the aggregates formed were smaller in size and were less compacted than those formed at higher Ca^{+ +}, as observed by scanning electron microscopy and confocal microscopy. In the initial stages of culture, the increase in aggregate size was mostly due to cell growth. In later stages of culture, the aggregate size appears to have an upper limit and its distribution becomes relatively invariant with time. For cells which do not form aggregates readily, microspheres with controlled — charge density were used to induce aggregate formation. Optical sectioning with confocal microscopy revealed that non-viable cells were predominantly localized in the interior, especially in large sized aggregates. These results indicate that growth kinetics may differ in aggregates of different size. The implication of such uneven property distribution on production processes will be discussed.