RESUMO
Bone is a metabolically active organ subjected to continuous remodeling process that involves resorption by osteoclast and subsequent formation by osteoblasts. Osteoclast involvement in this physiological event is regulated by macrophage colony-stimulating factor (M-CSF) and receptor activator of nuclear factor κB ligand (RANKL). Fusion of mono-nuclear pre-osteoclasts is a critical event for osteoclast differentiation and for bone resorption. Here we show that PBMCs can be successfully fused with polyethylenglicol (PEG) in order to generated viable osteoclast-like cells that exhibit tartrate-resistant acid phosphatase (TRAP) and bone resorptive activities. PEG-fused PBMCs expressed additional markers compatible with osteoclastogenic differentiation such as carbonic anhydrase II (CAII), calcitonin receptor (CR), cathepsin K (Cat K), vacuolar ATPase (V-ATPase) subunit C1 (V-ATPase), integrin ß3, RANK and cell surface aminopeptidase N/CD13. Actin redistribution in PEG-fused cells was found to be affected by cell cycle synchronization at G0/G1 or G2/M phases. PEG-induced fusion also led to expression of tyrosine kinases c-Src and Syk in their phosphorylated state. Scanning electron microscopy images showed morphological features typical of osteoclast-like cells. The results here shown allow concluding that PEG-induced fusion of PBMCs provides a suitable model system for understanding the mechanisms involved in osteoclastogenesis and for assaying new therapeutic strategies.
Assuntos
Diferenciação Celular , Fusão Celular , Leucócitos Mononucleares/metabolismo , Osteoclastos/citologia , Biomarcadores/análise , Biomarcadores/sangue , Reabsorção Óssea , Células Cultivadas , Humanos , Leucócitos Mononucleares/citologia , Modelos Biológicos , Polietilenoglicóis , Fosfatase Ácida Resistente a Tartarato/metabolismoRESUMO
The bone remodeling process occurs through bone formation by osteoblasts and bone resorption by osteoclasts, a process involving the contribution of endocrine and nervous systems. The mechanisms associated to differentiation and proliferation of osteoclasts and osteoblasts are considered a potential therapeutic target for treating some erosive bone diseases. The aim of the present study is to explore the feasibility of generating active osteoclast-like cells from peripheral blood mononuclear cells (PBMCs) following polyethylene glycol (PEG)-induced fusion. PEG-fused PBMCs showed TRAP+-multinucleated cells and bone resorption activity, and were also positive for osteoclast markers such as carbonic anhydrase II, calcitonin receptor, vacuolar ATPase, and cathepsin K, when examined by reverse transcription-polymerase chain reaction, immunochemistry and Western blotting. TRAP expression and bone resorptive activity were higher in whole PEG-fused PBMCs than in separated T lymphocytes, B lymphocytes or monocytes. Both TRAP expression and bone resorptive activity were also higher in osteogenesis imperfecta patients compared to PEG-fused PBMCs from healthy individuals. PEG-induced fusion was more efficient in inducing TRAP and bone resorptive activities than macrophage colony-stimulating factor or dexamethasone treatment. Bone resorptive activity of PEG-fused PMBCs was inhibited by bisphosphonates. Evidence is provided that the use of PEG-based cell fusion is a straightforward and amenable method for studying human osteoclast differentiation and testing new therapeutic strategies.