title: Effects of shear stress on nitric oxide and matrix protein gene expression in human osteoarthritic chondrocytes in vitro.
abstract: Mechanical loading alters articular cartilage metabolism. However, mechanisms underlying intracellular signaling and communication between cells in response to mechanical stresses remain enigmatic. This study tested the hypothesis that shear stress-induced nitric oxide (NO) production participates in the regulation of matrix protein gene expression. The data presented here demonstrate that exposure of human osteoarthritic chondrocytes to a continuously applied shear stress (1.64 Pa) upregulated NO synthase gene expression and increased NO release by 1.8-, 2.4-, and 3.5-fold at 2, 6, and 24 h, respectively. Exposure of chondrocytes to a short duration of shear stress for 2 h resulted in the release of accumulation of NO in the culture medium. Exposure of chondrocytes to shear stress for 2, 6, and 24 h inhibited type II collagen mRNA signal levels by 27%, 18% and 20% after a constant post-shear incubation period of 24 h. Aggrecan mRNA signal levels were inhibited by 30%, 32% and 41% under identical conditions. Addition of an NO antagonist increased type II collagen mRNA signal levels by an average of 1.8-fold (137% of the un-sheared control) and reestablished the aggrecan mRNA signal levels by an average of 1.4-fold after shear stress (92% of the un-sheared control) (ANOVA p < 0.05). These data support the hypothesis that shear stress-induced NO release may influence the development of degenerative joint diseases by inhibiting matrix macromolecule synthesis.
authors.affiliation: Rehabilitation Research and Development Center, Veterans Affairs Palo Alto Health Care System, CA 94304-1200, USA.
authors.forename: Mel S
authors.initials: MS
authors.lastname: Lee
authors.forename: Michael C D
authors.initials: MC
authors.lastname: Trindade
authors.forename: Takashi
authors.initials: T
authors.lastname: Ikenoue
authors.forename: David J
authors.initials: DJ
authors.lastname: Schurman
authors.forename: Stuart B
authors.initials: SB
authors.lastname: Goodman
authors.forename: R Lane
authors.initials: RL
authors.lastname: Smith
mesh_terms: D019902:Chondrocytes / Q000502:physiology*; D016326:Extracellular Matrix Proteins / Q000235:genetics*; D015870:Gene Expression; D006801:Humans; D009569:Nitric Oxide / Q000235:genetics* / Q000378:metabolism; D019001:Nitric Oxide Synthase / Q000235:genetics; D052247:Nitric Oxide Synthase Type II; D010003:Osteoarthritis / Q000235:genetics* / Q000378:metabolism / Q000473:pathology; D013314:Stress, Mechanical
chemical_list: D016326:Extracellular Matrix Proteins; D009569:Nitric Oxide; C496319:NOS2 protein, human; D019001:Nitric Oxide Synthase; D052247:Nitric Oxide Synthase Type II