Influence of Increased Extracellular Calcium Concentration and Donor Age on Density-Dependent Growth Inhibition of Human Fibroblasts

Elevated calcium chloride concentration ([CaCl₂]) has been shown to increase saturation density for an established mouse fibroblast line and for human fetal lung fibroblasts (WI-38). In order to examine the effect of increased [CaCl₂] on human fibroblasts from donors of varying age, fibroblasts were grown in medium (basal level of 1.8 mM CaCl₂) supplemented with fetal bovine serum (FBS) until confluent. Compared to controls in basal medium, newborn foreskin fibroblasts exposed to additional CaCl₂ had a 110-450% increased cell yield that was independent of [CaCl₂] within the range of an additional 1.5-5.0 mM. The effect was maintained over an eightfold range of FBS concentration. Initial growth rate was unaffected, but a prolongation of exponential phase occurred for cultures exposed to increased [CaCl₂]. Confluent cultures refed medium with increased [CaCl₂] were stimulated 5- to 10-fold more than cultures refed basal medium. An additional 2 mM CaCl₂ resulted in a 210% increase for young adult-derived fibroblasts versus a 29% increase for old adult-derived fibroblasts (P < 0.001). These data indicate that increased [CaCl₂] decreases density-dependent growth inhibition of postnatal human dermal fibroblasts in Vitro and that this effect is donor age dependent.