[Show abstract][Hide abstract]ABSTRACT: Chondrocyte death in articular cartilage wound edges and the subsequent lack of matrix-producing cells in the interface area are considered to be a major cause of impaired cartilage wound healing and poor integrative cartilage repair. This study was undertaken to investigate whether enzymatic matrix digestion can be used to stimulate integrative cartilage repair via a mechanism of local increase in the amount of vital chondrocytes in cartilage wound edges.
Full-thickness bovine articular cartilage samples were cultured in vitro for 14 days in standard medium. Samples were either left untreated or treated for 48 hours with 0.3% hyaluronidase or 30 units/ml highly purified collagenase VII. Nuclear and cytoplasmic changes were analyzed to determine cell viability, and the number of vital chondrocytes in wound edges was determined. Subsequently, we investigated whether increased chondrocyte density in the lesion edges resulted in better wound healing. Finally, full-thickness human tibial plateau cartilage explants were tested with similar enzyme treatment protocols to determine the clinical value of our results.
In bovine explants a rapid onset of chondrocyte death was observed in wound edges in all treatment groups. This led to low chondrocyte density in a band of 0-150 microm from the lesion edges in untreated and hyaluronidase-treated explants. Treatment with 30 units/ml collagenase resulted in a significant increase in chondrocyte density in this area. The integration experiments demonstrated improved integration of the lesion edges after treatment with collagenase. In human articular cartilage an increase in chondrocyte density at the lesion edges could also be achieved, but only when proteoglycans were depleted from the wound edges prior to collagenase treatment.
Treatment with highly purified collagenase improves integrative cartilage repair, possibly by increasing the cell density at cartilage wound edges.
Full-text Article · May 2002 · Arthritis & Rheumatology
[Show abstract][Hide abstract]ABSTRACT: The prevalence of osteoarthritis (OAs) increases with age and coincides with the accumulation of advanced glycation endproducts (AGEs) in articular cartilage, suggesting that accumulation of glycation products may be involved in the development of OA. This study was designed to examine the effects of accumulation of AGEs on the turnover of the extracellular matrix of human articular cartilage.
Chondrocyte mediated cartilage degradation (GAG release, colorimetric) was measured in human articular cartilage of donors aged 19-82 years (N=30, 4-day culture). In addition, to mimic the age-related increase in AGE levels in vitro, cartilage was cultured in the absence or presence of glucose, ribose or threose. Cartilage degradation and proteoglycan synthesis ((35)SO(2)(-4) incorporation) were measured and related to the degree of cartilage AGE levels (fluorescence at 360/460 nm).
Chondrocyte-mediated degradation of articular cartilage (i.e. GAG release) decreased with increasing age of the cartilage donor (r=-0.43, P< 0.02). In vitro incubation of cartilage with glucose, ribose or threose resulted in a range of AGE levels that was highly correlated to the chondrocyte-mediated cartilage degradation (r=-0.77, P< 0.001, N=26). In addition, in these in vitro glycated cartilage samples, a decrease in proteoglycan synthesis was observed at increasing AGE levels (r=-0.54, P< 0.005, N=25).
This study shows that an increase in AGE levels negatively affects the proteoglycan synthesis and degradation of articular cartilage. In combination, these two effects reduce the turnover of the cartilage and thereby the maintenance and repair capacity of the tissue. By this mechanism, the age-related increase in cartilage AGE levels may contribute to the development of OA.
Full-text Article · Nov 2001 · Osteoarthritis and Cartilage
[Show abstract][Hide abstract]ABSTRACT: The integrity of the collagen network is essential for articular cartilage to fulfill its function in load support and distribution. Damage to the collagen network is one of the first characteristics of osteoarthritis. Since extensive collagen damage is considered irreversible, it is crucial that chondrocytes maintain a functional collagen network. We investigated the effects of advanced glycation end products (AGEs) on the turnover of collagen by articular cartilage chondrocytes. Increased AGE levels (by culturing in the presence of ribose) resulted in decreased collagen synthesis (P < 0.05) and decreased MMP-mediated collagen degradation (P < 0.02). The latter could be attributed to increased resistance of the collagen network to MMPs (P < 0.05) as well as the decreased production of MMPs by chondrocytes (P < 0.02). Turnover of a protein is determined by its synthesis and degradation rates and therefore these data indicate that collagen turnover is decreased at enhanced AGE levels. Since AGE levels in human cartilage increase ∼50 fold between age 20 and 80, cartilage collagen turnover likely decreases with increasing age. Impaired collagen turnover adversely affects the capacity of chondrocytes to remodel and/or repair its extracellular matrix. Consequently, age-related accumulation of AGE (via decreased collagen turnover) may contribute to the development of cartilage damage in osteoarthritis.
Full-text Article · Jun 2001 · Experimental Cell Research