Induction of macrophagic and granulocytic differentiation of murine bone marrow progenitor cells by 1,25-dihydroxyvitamin D3

Summary 1,25-Dihydroxyvitamin D₃ (1,25(OH)₂D₃) was recently shown to promote maturation of 5-fluorouracil (5FU)-treated bone marrow cells by up-regulating macrophage-colony stimulating factor (M-CSF) receptors in the presence of interleukin la (IL-1). In order to reveal how 1,25(OH)₂D₃ interacts with colony-stimulating factors and regulates the differentiation of bone marrow progenitor cell populations, in the present study, natural bone marrow cells were isolated from untreated mice and used in a-minimum essential medium supplemented with 20% heat-inactivated horse serum without added appropriate cytokines. Under the conditions, cells spontaneously differentiated gradually with days of culture, as assessed by expression of macrophage differentiation antigens such as Mac-1 (CD11b) and F4/80. Both M-CSF and granulocyte macrophage-colony stimulating factor (GM-CSF) induced only Mac-1 antigen expression. Simultaneous treatment with M-CSF and 1,25(OH)₂D₃ enhanced the M-CSF's effect on expression of both antigens, although (1,25(OH)₂D₃) per se has no effect on the expression for up to 11 days. In addition, successive treatment with 1,25(OH)₂D₃ and M-CSF or GM-CSF dramatically enhanced expression of both antigens or Mac-1 antigen, respectively. Similarly, both simultaneous and successive treatment with 1,25(OH)₂D₃ and M-CSF significantly enhanced phagocytic activity and H₂O₂ production, whereas successive treatment with (1,25(OH)₂D₃) and GM-CSF significantly enhanced only phagocytic activity. Enzymehistochemical study demonstrated that cells treated simultaneously or successively with 1,25(OH)₂D₃ and M-CSF were strongly positive for nonspecific esterase (NSE), a macrophage-specific marker, and that simultaneous or successive treatment with 1,25(OH)₂D₃ and GM-CSF yielded cells strongly positive for NSE or for chloroacetate esterase (ChAE), a granulocyte-specific marker, respectively. These findings suggest that 1,25(OH)₂D₃ primes bone marrow progenitor cell populations not only to M-CSF but also to GM-CSF and thereby accelerates the CSFs-dependent differentiation of the cells to the macrophage or granulocyte.