1,25-Dihydroxyvitamin D3 differentiates normal neutrophilic promyelocytes to monocytes/macrophages in vitro

Abstract

Although it is well established that the addition of 1,25- dihydroxyvitamin D3 (D3) to the culture of normal human granulocyte/macrophage progenitors induces monocyte/macrophage (Mo/Mφ) colonies, the target cells of D3 in the Mo/Mφ differentiation have not been identified. We examined whether neutrophilic promyelocytes are the target cells. As a source of the promyelocyte fraction, we used colonies after 5 days of culture (5-day colonies) of colony-forming unit-granulocyte. The culture contained granulocyte colony-stimulating factor (G-CSF) as the growth factor and generated only neutrophilic colonies. The promyelocytic nature of the 5-day colonies was confirmed morphologically, cytochemically, and ultrastructurally. After morphological evaluation on part of the individual colonies, they were transferred into new semisolid cultures with or without D3 (10-7 mol/L) in the presence of G-CSF, then incubated for the subsequent 7 days. With D3, the colonies were loose, and all the constituent cells were morphologically small macrophages, which were positive for α- naphthyl butyrate (αNB) esterase, strongly positive for CD14 antigan, and plastic-adherent. While without D3, the colonies were rather compact, and all the constituent cells were morphologically mature neutrophils, which were positive for naphthol ASD-chloroacetate esterase and weakly positive for CD14 antigen. Secondary culture of the 8- or 10-day colonies with D3 induced a lower number of αNB-positive cells, in proportion to the percentage of promyelocytes at the time of transfer in each colony. Four days of secondary culture with D3 was sufficient to induce αNB-positive cells. G-CSF was not an essential factor to induce αNB-positive cells. These findings indicate that D3 differentiates normal human neutrophilic promyelocytes into the Mo/Mφ lineage in vitro.