Murine Recombinant GM-CSF-Driven Rat Bone Marrow Cell Differentiation and Factors Suppressing Cell Proliferation

Abstract

Rat or mouse bone marrow cells (BMC) cultured for one week with a crude mouse L929 cellsupernatant or with purified colony stimulating factor type 1 (CSF-1) differentiate into an essentially pure population of macrophages (MΦ). Surprisingly, 90 to 95% of the cells obtained by culturing rat BMC for seven days with recombinant murine granulocyte-macrophage CSF (rmGM-CSF), regardless of concentrations, were classified as (M). The majority of the remaining cells were granulocytes. This effect is in contrast to that on mouse BMC cultures, where the percentage of granulocytes increased with higher concentrations of rmGM-CSF. The proliferative capacity of rat BMC was demonstrated by colony formation in soft-agar,enumerating total cell number in liquid cultures or measuring 3H-thymidine uptake. A crude L929 cell supernatant and rmGM-CSF induced cell proliferation in a dose-dependent manner. Maximal DNA-synthesis was observed on the fifth day of incubation when BMC were cultured at a density of ≥ 1 × 10 5 cells/well. In cultures initiated with lower cell density, prolonged DNA synthesis was observed. Thereafter, the rate of proliferation declined rapidly. Simultaneous incubation of BMC with GM-CSF and indomethacin led to increased levels of DNA synthesis, suggesting that prostaglandins may suppress cell proliferation. Furthermore, the CSF-induced BMC proliferation was dose dependently inhibited by dexamethasone and 1,25-dihydroxy-vitamin D 3 as well as by interferon-γ and tumor necrosis factor-α. The suppressive effect of both cytokines could be abrogated by the addition of the respective anticytokine antibodies.