Osteonecrosis of the jaws (ONJ) associated with the use of bisphosphonates is a newly described entity. To elucidate the mechanism leading to ONJ and to test the hypothesis that in patients with ONJ the bisphosphonates may interfere with endothelial cell proliferation, using flow cytometric analysis we evaluated the number of circulating endothelial progenitor cells (EPCs) and circulating endothelial cells (CECs) in eight patients with bisphosphonate treatment and osteonecrosis, eight multiple myeloma (MM) patients with bisphosphonates treatment without ONJ and five normal subjects. MM patients showed an increase of CD34+ cells with respect the control subjects and ONJ subjects. EPCs and CECs were higher in MM patients compared to controls and ONJ patients. ONJ patients showed a decrease of EPCs compared to control subjects while CECs were similar to the controls group. Our results seem to show the possibility that bisphosphonates could have a antiangiogenic effect and a suppressive effect on CECs of patients with ONJ.
2007 John Wiley & Sons, Ltd