The role of recombinant human M-CSF, IL-3, GM-CSF and calcitriol in clonal development of osteoclast precursors in primate bone marrow.

Evidence suggests that among the myeloid colony-stimulating factors (CSFs), macrophage-CSF (M-CSF) is important in normal development of osteoclasts. To understand the role of M-CSF and other myeloid CSFs on clonal growth of osteoclast progenitors, isolated monkey bone marrow cells expressing the CD34 antigen were grown in soft agar or methylcellulose cultures in the presence of recombinant human M-CSF, granulocyte-macrophage CSF (GM-CSF), interleukin-3 (IL-3), calcitriol and various combinations of these factors. Day-10 to day-20 colonies were stained for tartrate-resistant acid phosphatase (TRAP) in order to identify putative osteoclast progenitors.

Modulation of tartrate-resistant acid phosphatase expression by calcitriol in CSF-induced macrophage colonies.

The osteoclast is thought to be a hemopoietically derived cell, but questions exist about which hemopoietic growth factors are responsible for proliferation of osteoclast precursors. Experiments were thus performed to see if recombinant human colony-stimulating factors (CSFs) influenced the expression of tartrate-resistant acid phosphatase (TRAP), an osteoclast marker enzyme, by monkey bone marrow colonies in vitro. In addition, the effect of 1,25-dihydroxyvitamin D3 (calcitriol) on CSF-induced colony growth and TRAP expression was also determined.