A single blunt impact on cartilage promotes fibronectin fragmentation and upregulates cartilage degrading stromelysin-1/matrix metalloproteinase-3 in a bovine ex vivo model.

Post-traumatic osteoarthritis (PTOA) is characterized by progressive cartilage degeneration in injured joints. Since fibronectin-fragments (Fn-fs) degrade cartilage mainly through up-regulating matrix metalloproteinases (MMPs) and pro-inflammatory cytokines, we hypothesized that Fn-fs play a key role in PTOA by promoting chondrolysis in and around injured cartilage. To test this hypothesis, we profiled the catabolic events focusing on fibronectin fragmentation and proteinase expression in bovine osteochondral explants following a single blunt impact on cartilage with a drop tower device which created partial-thickness tissue damage.

Mechanical impact induces cartilage degradation via mitogen activated protein kinases.

Objective: To determine the activation of Mitogen activated protein (MAP) kinases in and around cartilage subjected to mechanical damage and to determine the effects of their inhibitors on impaction-induced chondrocyte death and cartilage degeneration.

Design: The phosphorylation of MAP kinases was examined with confocal microscopy and immunoblotting. The effects of MAP kinase inhibitors on impaction-induced chondrocyte death and proteoglycan (PG) loss were determined with fluorescent microscopy and 1, 9-Dimethyl-Methylene Blue (DMMB) assay.

Biomechanical modulation of collagen fragment-induced anabolic and catabolic activities in chondrocyte/agarose constructs.

Introduction: The present study examined the effect of collagen fragments on anabolic and catabolic activities by chondrocyte/agarose constructs subjected to dynamic compression.

Methods: Constructs were cultured under free-swelling conditions or subjected to continuous and intermittent compression regimes, in the presence of the N-terminal (NT) and C-terminal (CT) telopeptides derived from collagen type II and/or 1400 W (inhibits inducible nitric oxide synthase (iNOS)). The anabolic and catabolic activities were compared to the amino-terminal fibronectin fragment (NH2-FN-f) and assessed as follows: nitric oxide (NO) release and sulphated glycosaminoglycan (sGAG) content were quantified using biochemical assays.

Fibronectin fragments mediate matrix metalloproteinase upregulation and cartilage damage through proline rich tyrosine kinase 2, c-src, NF-kappaB and protein kinase Cdelta.

Objective: Since fibronectin fragments (Fn-fs) enhance cartilage damage through integrins, the objective was to investigate the role of integrin linked kinases, focal adhesion kinase (FAK) and a soluble form of FAK, proline rich tyrosine kinase 2 (Pyk2) and cellular src kinase (c-src) and the transcription factor, nuclear factor kappaB (NF-kappaB) in cartilage damage.

Methods: Bovine chondrocytes were cultured with various concentrations of three different Fn-fs, an amino-terminal 29 kDa, a gelatin binding 50 kDa and a central 140-kDa Fn-fs, each with progressively weaker cartilage damaging activity, or with native fibronectin (Fn), and lysates probed for activation of the selected kinases. Confocal microscopy was used to visualize intracellular location of activated kinases and NF-kappaB.

Telopeptides of type II collagen upregulate proteinases and damage cartilage but are less effective than highly active fibronectin fragments.

Objective And Design: We hypothesize that N-telopeptide (NT) and C-telopeptides (CT) of type II collagen can enhance proteinases and cause cartilage damage and have compared damaging activities to an extensively characterized potent fibronectin fragment (Fn-f).

Materials: NT and CT peptides were synthesized.

Methods: Interaction of labeled peptides with chondrocytes was studied by fluorescence microscopy.