Effect of age and ovariectomy on fibroblastic colony-forming unit numbers in rat bone marrow

It is now thought that osteoblasts (OB) stem from mesenchymal precursor cells (fibroblastic colony forming units or CFU-f) in the bone marrow. As the availability of these cells may have a profound effect on bone formation, the effect of age and ovariectomy (OVX) on CFU-f numbers was studied. It was found that with increasing age the numbers of CFU-f in the marrow were drastically reduced. OVX had no effect on CFU-f levels in 4 week and 4 month old rats but raised CFU-f levels in 1 year old rats back to levels seen in younger rats. SHam operation alone had an effect on CFU-f levels in older rats and the OVX effects were indistinguishable from the sham effect until 20 d post operation when the sham levels returned to baseline. The results show that CFU-f levels follow a similar trend to the rates of bone formation seen in aged and OVX rats.