Human diploid fibroblast growth on polystyrene microcarriers in aggregates

Polystyrene microcarriers were prepared in four size ranges (53–63 m, 90–125 m, 150–180 m and 300–355 m) and examined for ability to support attachment and growth of human diploid fibroblasts. Cells attached rapidly to the microcarriers and there was a direct relationship between cell attachment and microcarrier aggregation. Phasecontrast and scanning electron microscopic studies revealed that while aggregation was extensive, most of the aggregate consisted of void volume. Cell growth studies demonstrated that human diploid fibroblasts proliferated well in microcarrier aggregates, reaching densities of 2.5–3×10⁶ cells per 2 ml dish after 6 days from an inoculum of 0.5×10⁶ cells per dish. When cells were added to the microcarriers at higher density (up to 5×10⁶ cells per 2-ml culture), there was little net growth but the cells remained viable over a 7-day period. In contrast, cells died when plated under the same conditions in monolayer culture. When the microcarriers were used in suspension culture, rapid cell attachment and rapid microcarrier aggregation also occurred. In 100-ml suspension culture, a cell density of 0.7×10⁶ cells per ml was reached after 7 days from an inoculum of 0.1×10⁶ cells. Based on these data, we conclude that microcarrier aggregation is not detrimental to fibroblast growth. These data also indicate that small microcarriers (53–63 m) (previously thought to be too small to support the growth of diploid fibroblasts) can support fibroblast growth and this occurs primarily because microcarriers in this size range efficiently form aggregates with the cells.