RETRACTED: Environmental Disruption of Circadian Rhythm Predisposes Mice to Osteoarthritis‐Like Changes in Knee Joint

Abstract

Circadian rhythm dysfunction is linked to many diseases, yet pathophysiological roles in articular cartilage homeostasis and degenerative joint disease including osteoarthritis (OA) remains to be investigated in vivo. Here, we tested whether environmental or genetic disruption of circadian homeostasis predisposes to OA-like pathological changes. Male mice were examined for circadian locomotor activity upon changes in the light:dark (LD) cycle or genetic disruption of circadian rhythms. Wild-type (WT) mice were maintained on a constant 12 hour:12 hour LD cycle (12:12 LD) or exposed to weekly 12 hour phase shifts. Alternatively, male circadian mutant mice (ClockΔ19 or Csnk1etau mutants) were compared with age-matched WT littermates that were maintained on a constant 12:12 LD cycle. Disruption of circadian rhythms promoted osteoarthritic changes by suppressing proteoglycan accumulation, upregulating matrix-degrading enzymes and downregulating anabolic mediators in the mouse knee joint. Mechanistically, these effects involved activation of the PKCδ-ERK-RUNX2/NFκB and β-catenin signaling pathways, stimulation of MMP-13 and ADAMTS-5, as well as suppression of the anabolic mediators SOX9 and TIMP-3 in articular chondrocytes of phase-shifted mice. Genetic disruption of circadian homeostasis does not predispose to OA-like pathological changes in joints. Our results, for the first time, provide compelling in vivo evidence that environmental disruption of circadian rhythms is a risk factor for the development of OA-like pathological changes in the mouse knee joint.

The chondrocyte clock gene Bmal1 controls cartilage homeostasis and integrity

“…Although a clock-independent role of BMAL1 cannot be completely ruled out (22,40), our data strongly support the role of BMAL1 in cartilage maintenance through its function as a central modulator of the circadian rhythm in gene expression. These results, together with the OA-like knee damage seen in mice subjected to environmental disruption of circadian rhythms (15), favor a hypothesis that BMAL1-regulated circadian rhythm is critical for cartilage function. Therefore, the cartilage phenotype observed here is likely due to a combined effect of the circadian dysregulation of multiple pathways.…”

“…Previous work identified autonomous cartilage circadian rhythms in mice that became dysregulated with age and upon chronic inflammation (11)(12)(13)(14). Moreover, environmental disruption of circadian rhythms in mice (mimicking chronic jet lag) predisposes knee cartilage to OA-like damage (15), further supporting the idea of an involvement of circadian rhythm disruption in OA development.…”

“…Cartilage was dissected and fixed in 4% paraformaldehyde, followed by paraffin embedding for IHC or processed for protein extraction and Western blot analysis to detect BMAL1 (47) or p-SMAD signaling as described previously (15). For the isolation of chondrocytes from non-OA knee joints, cartilage was enzymatically digested with 0.2% pronase for 1 hour, followed by 0.025% collagenase P supplemented with 5% FBS as previously described (15,48). siRNA transfection studies in isolated primary human articular chondrocytes using nucleofection were described previously (48).…”

“…Prior to dissection, each specimen was graded for overall degenerative changes on the basis of the modified 5-point scale of Collins (46). Cartilage was dissected and fixed in 4% paraformaldehyde, followed by paraffin embedding for IHC or processed for protein extraction and Western blot analysis to detect BMAL1 (47) or p-SMAD signaling as described previously (15). For the isolation of chondrocytes from non-OA knee joints, cartilage was enzymatically digested with 0.2% pronase for 1 hour, followed by 0.025% collagenase P supplemented with 5% FBS as previously described (15,48).…”

Effects of Dietary Saturated Fatty Acids on the Onset and Progression of Osteoarthritis in Rat Knee Joints

“…In stem cells isolated from leptin-deficient mice, the NF-κB activation was down-regulated by the treatment of EPA [195]. In a recent study, increased activation of the protein kinase Cδ (PKCδ)-ERK-RUNX2/NFκB signaling pathways were found to be present in the articular chondrocytes of environmentally shifted mice [196]. Extension of this study compared the effects of high-fat diet (HFD) versus normal diet (ND) on OA development and concluded that HFD increased the activation of the same signaling pathway [197].…”