Send to

Choose Destination
See comment in PubMed Commons below
Scand J Rheumatol. 2012 Mar;41(2):132-40. doi: 10.3109/03009742.2011.605391. Epub 2012 Jan 3.

Functional folate receptor beta-expressing macrophages in osteoarthritis synovium and their M1/M2 expression profiles.

Author information

Graduate School of Medical and Dental Sciences, Kagoshima University, Kagoshima, Japan.



The distribution of folate receptor (FR)-β+ macrophages and their M1/M2 expression profiles were examined in osteoarthritis (OA) synovial tissues, and compared to those in rheumatoid arthritis (RA) synovial tissues and CD163+ macrophages in both OA and RA synovial tissues.


The phenotypes and fluorescein isothiocyanate (FITC)-folate uptake of FR-β+ synovial macrophages were analysed by flow cytometry. The distribution of FR-β+ macrophages in OA and RA synovial tissues was examined by immunofluorescent microscopy. Tumour necrosis factor (TNF)-α, inducible nitric oxide synthase (iNOS), interleukin (IL)-10, and transforming growth factor (TGF)-β expression in FR-β+ macrophages was detected by double-immunostaining in both OA and RA synovial tissues.


FR-β+ macrophages were predominantly present in the synovial lining layer in OA patients. The proportion of CD163-FR-β+ cells in synovial mononuclear cells (MNCs) was increased in OA compared to RA synovial tissues. FR-β(high) macrophages from OA synovial tissues represented the majority of folic acid-binding cells. Although FR-β+ or CD163+ macrophages in the synovial tissues of OA and RA patients expressed a mixed pattern of M1 and M2 macrophage markers, there were more M2 markers expressing synovial macrophages in OA than in RA patients.


The distribution and M1/M2 expression profiles of FR-β+ synovial macrophages were different between OA and RA synovial tissues. Thus, the findings underscore that the M1/M2 paradigm using surface markers FR-β and CD163 is an oversimplification of macrophage subsets. Functional FR-β present on OA synovial macrophages provides a potential tool for the diagnosis and treatment of OA.

[Indexed for MEDLINE]
PubMed Commons home

PubMed Commons

How to join PubMed Commons

    Supplemental Content

    Full text links

    Icon for Taylor & Francis
    Loading ...
    Support Center