The human type II collagen (Col II), specifically expressed in chondrocytes, is a crucial component of the adult hyaline cartilage. We examine the potential of artificial induction of Col II in human peripheral blood mononuclear cells (PBMNCs) as a novel Col II provider. Human PBMNCs were purified and were treated with high doses of macrophage-colony stimulating factor (M-CSF), granulocyte macrophage-colony stimulating factor (GM-CSF), or granulocyte-colony stimulating factor (G-CSF) and examined the Col II expression at indicated days. Quantitative Col II expression was validated by real-time reverse transcriptase-polymerase chain reaction (RT-PCR), immunocytochemistry, and flow cytometry. We demonstrate that monocytes in PBMNCs can be artificially induced to express both Col II proteins and M2 macrophage markers by the high concentration of colony-stimulating factors, especially M-CSF and GM-CSF. The Col II proteins were detected on the cell membrane and in the cytoplasm by flow cytometry and immunocytostaining. Combination with IL-4 provided a synergistic effect with M-CSF/GM-CSF to trigger Col II expression in M2 macrophages. These CD206 and Col II double-expressing cells, named modified macrophages, share M2 macrophages' anti-inflammatory potency. We demonstrated that the modified macrophages could significantly attenuate the inflammatory progress of Complete Freund's adjuvant (CFA)-induced arthritis and collagen-induced arthritis in rodents. Here, we provide the first evidence that a modified macrophage population could ectopically express Col II and control the progress of arthritis in animals.
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