Human uterus-derived growth substances for rat bone cells and fibroblasts

The effects of extracts from normal human uteri on tritiated thymidine incorporation and cell number were studied in primary cultures of isolated fetal rat calvarial osteoblasts and fetal rat skin fibroblasts. In this study crude uterine extracts were shown to stimulate tritiated thymidine incorporation into cellular deoxyribonucleic acid in osteoblast-like and fibroblast-like cell cultures above controls levels. This effect, which began after 6 hours, was maximal after 24 hours of incubation. In addition, the number of osteoblast-like and fibroblast-like cells increased above control levels after 1, 3, and 5 days of incubation. The above effects were dose-dependent, and maximal stimulation of uterine extracts was comparable with the stimulation achieved by 10% fetal bovine serum. The degree of stimulation by uterine extracts, expressed as percent above controls, was not dependent on the concentration of fetal bovine serum in cell culture medium. The above results are consistent with the view that uterine extracts contain mitogen(s) for bone cells and fibroblasts. These mitogens could play an important role in bone physiology and uterine pathophysiology.