Alkaline Phosphatase Positive Populations during Monocyte Cell Differentiation in vitro. Overlapping markers as a link between monocytic cells, dendritic cells, osteoclasts and osteoblasts

DAGMAR E.H. HEINEMANN ; HEIDE SIGGELKOW ; LAURA M. PONCE ; VOLKER VIERECK ; KARL G. WIESE; J. HINRICH PETERS

IMMUNOBIOLOGY.

ELSEVIER GMBH

Año: 2000 vol. 202 p. 68 - 81

0171-2985

Human monocytes (Mo) in culture can be differentiated into macrophages (Mφ), dendritic cells (DC) and osteoclasts. In addition, we have established a Mo-derivedin vitrogranuloma model which here was compared withex-vivoisolated foreign body granuloma cells. In these models overlapping phenotypes developed berween monocyte-derived dendritic cells (MoDC), osteoclasts, Mφ, and osteoblasts. In Mo cultures granulomas were induced by immobilized particulate material. AP activity (osteoblast marker) was found to be co-expressed with cytoplasmic tartrate resistant acid phosphatase (TRAP) as a marker of osteoclasts. While proliferating, the number of AP+cells decreased, being replaced by cells co-expressing the osteoclast markers vitronectin receptor (VNR) and TRAP. Coexpression of the Mo/Mφ marker CD68 with AP or VNR confirmed the monocytic origin of the cells. When Mo were treated with interleukin-4 (IL-4), the number of AP+cells markedly increased and remained stably expressed over 12 days. In explants fromex vivogranulomas obtained from endoprosthetic revisions the major cell type was the AP+cell co-expressing CD68. The bone-specific alkaline phosphatase (BAP) as a marker of osteoblasts was detected by FACS analysis in theex vivogranuloma cells. By RT-PCR the mRNA for osteocalcin, which is a highly specific marker for osteoblasts, was detected. From our results we conclude an ontogenetic relationship berween macrophages, DC and osteoclasts. Furthermore, the data suggest a transdifferentiation berween Mo and osteoblasts.