Inhibiting calcineurin activity under physiologic tonicity elevates anabolic but suppresses catabolic chondrocyte markers

Anna Windt, E Haak, Nicole Kops, Jan Verhaar, HH Weinans, Holger Jahr

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24 Citations (Scopus)

Abstract

Objective The physiologic interstitial tonicity of healthy articular cartilage (350480 mOsm) is lowered to 280350 mOsm in osteoarthritis (OA). This results in loss of tissue prestress, altered compressive behavior, and, thus, inferior tissue properties. This study was undertaken to determine whether physiologic tonicity in combination with the inhibition of calcineurin (Cn) activity by FK-506 has synergistic effects on human articular chondrocytes and explants in vitro. Methods OA chondrocytes and explants and non-OA chondrocytes were cultured in cytokine-free medium of 280 mOsm or 380 mOsm with or without Cn inhibition by FK-506. Chondrogenic, hypertrophic, and catabolic marker expression was evaluated at the messenger RNA (mRNA), protein, and activity levels. Results Compared to OA chondrocytes cultured at 280 mOsm, those cultured at 380 mOsm had increased expression of mRNA for chondrogenic markers (e.g., similar to 13 fold for COL2; P < 0.001), and decreased COL1 expression (similar to 0.5 fold, P < 0.01). Inhibiting Cn activity under physiologic tonicity further enhanced the expression of anabolic markers at the mRNA level (similar to 50 fold for COL2; P < 0.001, similar to 2 fold for AGC1; P < 0.001, and similar to 3.5 fold for SOX9; P < 0.001) and at the protein level (similar to 6 fold for type II collagen; P < 0.001). Cn inhibition suppressed relevant collagenases as well as hypertropic and mineralization markers at the mRNA and activity levels. Expression of aggrecanase 1 and aggrecanase 2 was not influenced by tonicity or FK-506 alone, but the combination suppressed both, by similar to 50% (P < 0.05) and similar to 40% (P < 0.001), respectively. Generally, similar anabolic and antihypertrophic effects were observed in ex vivo cartilage explant cultures and non-OA chondrocytes. Conclusion Our findings indicate that Cn at physiologic tonicity exerts a superior effect compared to physiologic tonicity or FK-506 alone, increasing anabolic markers while suppressing hypertrophic and catabolic markers. Our data may aid in the development of improved cell-based chondral repair and OA treatment strategies.
Original languageUndefined/Unknown
Pages (from-to)1929-1939
Number of pages11
JournalArthritis & Rheumatism
Volume64
Issue number6
DOIs
Publication statusPublished - 2012

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