Effect of bisphosphonate on the in vitro proliferation dynamics of CFU-GM
De Caro, L.; Ghizzi, A.
Bollettino della Societa Italiana di Biologia Sperimentale 69(7-8): 439-446
1993
ISSN/ISBN: 0037-8771 PMID: 8155301 Document Number: 417028
Bisphosphonates, potent inhibitors of osteoclast-mediated bone resorption, affect different ways of the intracellular metabolism of the osteclasts. Likewise other cell lines are affected by bisphosphonate action, among these the macrophagic cells. So we assayed the dichloromethylene diphosphonate (clodronate, C1-2MBP) 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 Cl-2MBP 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). In spite of the difficulty of the transferring the in vitro clodronate effects into vivo, it may be retained that therapeutic doses of clodronate affect granulopoiesis. This inhibiting effect on the granulopoiesis might become important in the following conditions: 1) during long term therapy with bisphosphonates; 2) in subjects already neutropenic; 3) in subjects at risk of neutropenia owing to antineoplastic cytostatic therapy. The present studies were performed with unfractionated bone marrow cells. Other investigations, here not showed, were also performed with bone marrow cells fractionated in Phicoll Isopaque gradient. Such investigations demonstrated a relative independence from clodronate of the in vitro growth of the isolated GM-progenitors. This means that the above indicated myelosuppressive clodronate effect may be ascribed to an impairment of the cells of the bone marrow microambient that are plated with the bone marrow GM-progenitors.