Is altered NMDA signalling responsible for disrupting the chondrocyte-intrinsic circadian clock and inducing the chondrocyte phenotype shift central to the development of osteoarthritis? — ASN Events
  1. Schedule
  2. Welcome Reception & ANZBMS Plenary Posters
  3. Is altered NMDA signalling responsible for disrupting the chondrocyte-intrinsic circadian clock and inducing the chondrocyte phenotype shift central to the development of osteoarthritis?

Is altered NMDA signalling responsible for disrupting the chondrocyte-intrinsic circadian clock and inducing the chondrocyte phenotype shift central to the development of osteoarthritis? (#111)

Raewyn Poulsen 1 , Mark Zhu 1 , Jacob T Munro 1
  1. University of Auckland, Grafton, AUCKLAND, New Zealand

The cartilage destruction in osteoarthritis results when chondrocytes undergo a phenotype shift and begin producing excessive amounts of cartilage-degrading enzymes1. Why this phenotype shift occurs is unknown. Most cells contain a circadian clock. Molecularly identical to the more well-known hypothalamic clock, cell-intrinsic clocks regulate cell phenotype. Recently we discovered that the chondrocyte clock is altered in osteoarthritis2. Inducing this change in normal chondrocytes causes osteoarthritis-like phenotype changes in vitro2,3 and cartilage loss in rodent models4. NMDA is a critical regulator of the hypothalamic clock5. Chondrocytes express NMDA receptors6. HYPOTHESIS: Altered NMDA signalling causes clock disruption and the chondrocyte phenotype shift in osteoarthritis.

Human chondrocytes isolated from macroscopically-normal cartilage were treated with Il1b or H2O2, (known inducers of the osteoarthritis-associated phenotype change), with/without a broad-spectrum NMDA receptor inhibitor (memantine). Chondrocytes isolated from osteoarthritic cartilage were also treated with memantine. Expression of clock genes and osteoarthritis-relevant phenotype markers were measured every 4h for 24h.

Il1b and H2O2 induced changes in the chondrocyte clock comparable to those observed in osteoarthritis. Memantine prevented Il1b and H2O2-induced changes in the clock and in MMP13, SOX9, IHH and ColX expression. In chondrocytes isolated from osteoarthritic cartilage, memantine restored normal expression of clock genes and reduced expression of MMP13, ColX and IHH. Surprisingly, in chondrocytes isolated from macroscopically-normal cartilage, memantine induced osteoarthritis-associated changes in the clock and cell phenotype.  Chondrocytes from osteoarthritic cartilage or chondrocytes treated with Il1b or H2O2 expressed the GRIN2B NMDA receptor. However untreated chondrocytes from macroscopically-normal cartilage did not. A GRIN2B-specific antagonist reduced MMP13, ColX and IHH expression and partially restored clock gene expression in osteoarthritic chondrocytes without disrupting clock gene or phenotype marker expression in chondrocytes from macroscopically-normal cartilage. 

Altered NMDA receptor expression may disrupt the chondrocyte clock, driving the cell phenotype shift central to osteoarthritis development.

  1. Goldring MB. Articular cartilage degradation in osteoarthritis. HSS J 2012;8. doi:10.1007/s11420-011-9250-z
  2. Snelling SJ, Forster A, Mukherjee S, Price AJ, Poulsen RC. The chondrocyte-intrinsic circadian clock is disrupted in human osteoarthritis. Chronobiol Int 2016;33:574-9.
  3. Yang W, Kang XM, Liu JL, et al. Clock Gene Bmal1 Modulates Human Cartilage Gene Expression by Crosstalk With Sirt1. Endocrinology 2016;157:3096-107.
  4. Dudek M, Gossan N, Yang N, et al. The chondrocyte clock gene Bmal1 controls cartilage homeostasis and integrity. Journal of Clinical Investigation 2016;126:365-76.
  5. Mintz EM, Marvel CL, Gillespie CF, Price KM, Albers HE. Activation of NMDA receptors in the suprachiasmatic nucleus produces light-like phase shifts of the circadian clock in vivo. The Journal of neuroscience : the official journal of the Society for Neuroscience 1999;19:5124-30.
  6. Ramage L, Martel MA, Hardingham GE, Salter DM. NMDA receptor expression and activity in osteoarthritic human articular chondrocytes. Osteoarthritis and Cartilage 2008;16:1576-84.