Extracts of cortical bone from adult rats stimulate DNA synthesis in osteoprogenitor cells from fetal rats.

DNA-synthesis-stimulating activity is stored in cortical bone of normal adult rats. Devitalized cortical bone of adult rats extracted with 0.6 N HCl-4M guanidine HCl solution stimulates DNA synthesis in calvarial osteoprogenitor cells from fetal rats. This activity is heat stable and resides in reduction-labile protein with molecular weights of 13,700-25,000 daltons (Sephacryl S-200 gel column chromatography without reduction). The active fraction purified by gel filtration contains several proteins with molecular weights of 14,400-30,000 daltons (SDS-polyacrylamide gel electrophoresis with reduction).