[Effect of bisphosphonate on the in vitro proliferation dynamics of CFU-GM]

Bisphosphonates, potent inhibitors of osteoclast-mediated bone resorption, affect different ways of the intracellular metabolism of the osteoclasts. Likewise other cell lines are affected by bisphosphonate action, among these the macrophagic cells. So we assayed the dichloromethylene diphosphonate (clodronate, Cl2MBP) effect on the in vitro proliferation of granulocytic-macrophage progenitor cells (GM-progenitors). The bone marrow progenitor cells of four healthy volunteers were plated in double layer agar by Pike and Robinson's technique, with the addition of clodronate concentrations rising from 0.004 till 4.0 mMol. For each experimental point we evaluated: 1) the global growth of the proliferating GM-progenitors (tPP) deduced from the number of the counted cellular aggregates (CA); 2) the mean size (m.s.) of the CA; 3) the total proliferative capacity (TPC), deduced from the aggregate mean size per the number of the CA; 4) the contribution to the proliferative events by each subsets of proliferating GM-progenitors (early proliferating GM-progenitors, forming the CA present at the 7th day of the in vitro culture; later proliferating GM-progenitors, appearing only at the 12th day). The dose-effect curve showed decrease both of the tPP and TPC for increasing concentrations of clodronate up to a complete growth inhibition at the concentration 4.23 mMol of clodronate. Concerning the m.s. of the in culture growth aggregates, in three of the four cases it appears unvaried up to the Cl2MBP concentration 0.4 mMol. The trends of dose-effect curves have been analysed both for colonies (CA-P4) and for clusters (CA-P1, -P2, -P3 of our classification).(ABSTRACT TRUNCATED AT 250 WORDS)