Incorporation of 3H-thymidine by wild-type (+/+) and SPARC-null (-/-) dermal fibroblasts. Cells were plated and cultured overnight in DMEM containing 10% FBS. Cells were then washed with DMEM without FBS and incubated with 3H-thymidine in DMEM containing 10% FBS. Data were derived from two independent experiments each performed in triplicate. Bars show mean ± SD.