Calcineurin modulates the catabolic and anabolic activity of chondrocytes and participates in the progression of experimental osteoarthritis.
OBJECTIVE
To determine whether intracellular calcineurin (Cn), a calcium-activated phosphatase, regulates the anabolic and catabolic activities of chondrocytes, and is a potential target in the treatment of osteoarthritis (OA).


METHODS
CnA expression was examined in cartilage tissue samples and cultured chondrocytes from OA patients, using immunohistochemistry and Western blot analysis, respectively. Concentrations of matrix metalloproteinases (MMPs) and tissue inhibitor of metalloproteinases 1 (TIMP-1) in the culture supernatants were determined using enzyme-linked immunosorbent assay. Levels of nitric oxide (NO) and type II collagen (CII) were measured using the Griess reaction and Western blot analysis, respectively. In addition, the pathologic role of Cn was examined in an in vivo model in which experimental OA was induced in mice by injecting type VII collagenase into the knee joints.


RESULTS
CnA was highly expressed in the chondrocytes of lesional OA cartilage. Cyclosporin A (CSA), a Cn inhibitor, inhibited spontaneous and interleukin-1beta-stimulated production of NO, MMP-1, and MMP-3 in chondrocytes. However, CSA increased the levels of production of CII, TIMP-1, and transforming growth factor beta. Similar changes in MMP-1, NO, and CII expression levels in chondrocytes were observed after the targeted inhibition of Cn by overexpression of calcineurin binding protein 1, a natural Cn antagonist. Moreover, in the mouse model, animals treated with CSA showed a significant decrease in both the extent and the severity of cartilage damage, which were assessed macroscopically and microscopically, compared with vehicle-treated animals.


CONCLUSIONS
These results suggest that CnA is critically involved in the catabolic and anabolic activities of chondrocytes as well as in the progression of experimental OA. Targeted inhibition of CnA may be an effective treatment strategy for OA.
Yoo
Seung-Ah
SA
Catholic University of Korea, Seoul, South Korea.
Park
Bo-Hyoung
BH
Yoon
Hyung-Ju
HJ
Lee
Joo-Yup
JY
Song
Joo-Hyoun
JH
Kim
Hyun Ah
HA
Cho
Chul-Soo
CS
Kim
Wan-Uk
WU
D000818:Animals; D019703:Calcineurin / Q000627:therapeutic use*; D002478:Cells, Cultured; D019902:Chondrocytes / Q000187:drug effects / Q000502:physiology*; D003094:Collagen / Q000378:metabolism; D004195:Disease Models, Animal; D018450:Disease Progression; D004797:Enzyme-Linked Immunosorbent Assay; D006801:Humans; D045726:Metalloproteases / Q000378:metabolism; D051379:Mice; D009569:Nitric Oxide / Q000378:metabolism; D010003:Osteoarthritis / Q000188:drug therapy* / Q000503:physiopathology*; D020133:Reverse Transcriptase Polymerase Chain Reaction
D009569:Nitric Oxide; D003094:Collagen; D019703:Calcineurin; D045726:Metalloproteases