Effect of inhibition of matrix metalloproteinases on cartilage loss in vitro and in a guinea pig model of osteoarthritis.

Objective: To study the effects of a matrix metalloproteinase (MMP) inhibitor (S-34219) on osteoarthritis (OA) cartilage cultures and in the meniscectomized guinea pig model of OA.

Methods: The inhibitory activity of S-34219 on MMPs and aggrecanase was studied by fluorimetry and immunoassay, respectively. The effects of S-34219 on proteoglycan and collagen degradation were studied in cultures of rabbit and human cartilage.

Assays of proteoglycan and collagen degradation in cultures of rabbit cartilage explants.

Cultures of cartilage explants have long been used to study the effects of modulators of extracellular matrix degradation. We present a simple and rapid assay system, based on culture of rabbit cartilage explants, which permits study of the effects of protease inhibitors on proteoglycan degradation (caused by either aggrecanases or matrix metalloproteinases [MMPs]), and on collagen degradation. The assay is based on the ability of interleukin-1 to stimulate both aggrecanase activity and synthesis of inactive MMPs, which are then activated by p-aminophenylmercuric acetate for the study of MMP-mediated proteoglycan degradation or by plasmin for the study of collagen degradation.

Culture of chondrocytes in alginate beads.

A classic method for the encapsulation and culture of chondrocytes in alginate beads is described. Chondrocytes are released from cartilage matrix by collagenase/dispase digestion and mixed with a solution of 1.25% alginic acid until a homogenous suspension is obtained.

Effects of transforming growth factor-beta on aggrecanase production and proteoglycan degradation by human chondrocytes in vitro.

Objective: Aggrecan is degraded by Aggrecanases (ADAMTS-4 and -5) and MMPs, which cleave its core protein at different sites. Transforming growth factor (TGF)beta is known to stimulate matrix formation in cartilage, and ADAMTS-4 production in synoviocytes. The aim of this in-vitro study was to examine the effects of TGFbeta on aggrecanase production in human cartilage.

Effects of agonists of peroxisome proliferator-activated receptor gamma on proteoglycan degradation and matrix metalloproteinase production in rat cartilage in vitro.

Objective: To examine the effects of agonists of peroxisome proliferator-activated receptor (PPAR) gamma on proteoglycan degradation induced by interleukin (IL)-1beta or tumor necrosis factor (TNF)alpha in cartilage in vitro.

Design: Proteoglycan degradation was measured as release of radioactivity from rat cartilage explants previously labeled with (35)SO2-4. Western blots were used to examine tissue levels of aggrecan neoepitopes NITEGE and VDIPEN, generated by aggrecanases and matrix metalloproteinases (MMP), respectively.

YKL-40 (cartilage gp-39) induces proliferative events in cultured chondrocytes and synoviocytes and increases glycosaminoglycan synthesis in chondrocytes.

YKL-40 (cartilage gp-39), is a mammalian glycoprotein related in sequence to chitinases. Its function is unknown, but it is thought to be involved in tissue remodeling. Immunocytochemical staining of YKL-40 in guinea pig chondrocytes (GPC), rabbit chondrocytes (RC), and rabbit synoviocytes (RS) was higher in dividing cells than in confluent cells, suggesting a participation of YKL-40 in cell cycle events.

Effects of ceramide on aggrecanase activity in rabbit articular cartilage.

Ceramide participates in signal transduction of IL-1 and TNF, two cytokines likely involved in cartilage degradation in osteoarthritis. We previously showed that ceramide stimulates proteoglycan degradation, mRNA expression of matrix metalloproteinase (MMP)-1, -3, and -13, and pro-MMP-3 production in rabbit cartilage. Since aggrecan, the main cartilage proteoglycan, can be cleaved by metalloproteinases both of MMP and aggrecanase type, the aim of this study was to determine if ceramide stimulates aggrecanase action and, if that is the case, in which measure aggrecanase mediates the degradative effect of ceramide.

Effects of ceramide on apoptosis, proteoglycan degradation, and matrix metalloproteinase expression in rabbit articular cartilage.

Cartilage loss in osteoarthritis is characterized by matrix degradation and chondrocyte death. The lipid messenger ceramide is implicated in signal transduction of the catabolic cytokines tumor necrosis factor (TNF) and interleukin-1 (IL-1), as well as in apoptosis. The aim of this study was to examine the in vitro effects of ceramide on proteoglycan degradation, matrix-metalloproteinase (MMP) expression and activity, and chondrocyte apoptosis in rabbit articular cartilage.

Amino derivatives of phenyl alkyl thiophene as inhibitors of bone resorption. Structure-activity relationship.

Metabolism of arachidonic acid through the 5-lipoxygenase (LO) pathway generates compounds that stimulate osteoclastic bone resorption; since LO metabolites might play a role in bone loss due to excessive resorption it was tried to develop a series of antiresorptive agents starting from an already known LO inhibitor. Of the 35 compounds synthesized, 11 strongly inhibited (10 mumol/l) retinoic acid-induced bone resorption in cultured mouse calvariae; they were also tested for their effect on LO activity using rat peritoneal neutrophils, but no correlation could be drawn between inhibition of LO and bone resorption. Other pathways, still to be identified, must therefore be targeted by these compounds even though LO inhibition might contribute to their effects on bone.

Effects of parathyroid hormone and agonists of the adenylyl cyclase and protein kinase C pathways on bone cell proliferation.

The anabolic effect of parathyroid hormone (PTH) on bone is partly due to a stimulation of osteoblast proliferation. The PTH signal is transduced by the pathways of adenylyl cyclase (AC)/protein kinase (PK) A and phospholipase C/PKC/Ca++. There is still uncertainty about the relative contribution of the two pathways to the proliferative effects of the hormone.

Bone morphometric changes in adjuvant-induced polyarthritic osteopenia in rats: evidence for an early bone formation defect.

Adjuvant polyarthritis (AP) in rats is known to result in extensive bone loss. This study investigates the mechanisms responsible for the early trabecular osteopenia evaluated at a single point in time--2 weeks after adjuvant injection--in the hindpaw of female Lewis rats using biochemical and histomorphometric methods. At this early point in time, the inflammation was generalized (inflammatory score, 20; albumin/globulin, -80% versus control).