HUMAN-DIPLOID FIBROBLAST GROWTH ON POLYSTYRENE MICROCARRIERS IN AGGREGATES

Polystyrene microcarriers were prepared in four size ranges (53-63 mu m, 90-125 mu m, 150-180 mu m and 300-355 mu m) and examined for abilit y to support attachment and growth of human diploid fibroblasts. Cells attached rapidly to the microcarriers and there was a direct relation ship between cell attachment and microcarrier aggregation. Phase-contr ast and scanning electron microscopic studies revealed that while aggr egation was extensive, most of the aggregate consisted of void volume. Cell growth studies demonstrated that human diploid fibroblasts proli ferated well in microcarrier aggregates, reaching densities of 2.5-3 x 10(6) cells per 2 mi dish after 6 days from an inoculum of 0.5 x 10(6 ) cells per dish. When cells were added to the microcarriers at higher density (up to 5 x 10(6) cells per 2-ml culture), there was little ne t growth but the cells remained viable over a 7-day period. In contras t, cells died when plated under the same conditions in monolayer cultu re. When the microcarriers were used in suspension culture, rapid cell attachment and rapid microcarrier aggregation also occurred. In 100-m l suspension culture, a cell density of 0.7 x 10(6) cells per mi was r eached after 7 days from an inoculum of 0.1 x 10(6) cells. Based on th ese data, we conclude that microcarrier aggregation is not detrimental to fibroblast growth. These data also indicate that small microcarrie rs (53-63 mu m) (previously thought to be too small to support the gro wth of diploid fibroblasts) can support fibroblast growth and this occ urs primarily because microcarriers in this size range efficiently for m aggregates with the cells.