Age-Related Changes in the Synthesis of Matrix Macromolecules by Bovine Articular Cartilage

Abstract

Calf and mature cow articular cartilage was labeled in vitro with [35S]SO4 and [3H]glycine and kinetics of incorporation of both isotopes by cartilage fragments was determined by scintillation spectroscopy. The cartilage fragments were then extracted in sequence with 4M GuHCl (Guanidium chloride) and pepsin. The pepsin digest was adjusted to 1.3 M NaCl and pepsin-solubilized collagen salted out. The 4M GuHCl extract, collagen and pepsin-resistent residue were then freeze-dried. The 4M GuHCl extract was further fractionated by DEAE (Diethylaminoethyl) 52 ion exchange chromatography to obtain protein and PG (Proteoglycan) fractions. The protein fraction was also characterised by SDS-PAGE and PG fraction by Sepharose C1-2B chromatography under associative conditions in the presence and absence of an exogenous HA (Hyaluronic acid). The GAG (Glycosaminoglycan) side chains of the PG samples were analysed by Sephadex G-200 column chromatography and their composition determined by paper chromatography after chondroitinase ABC digestion. Linear incorporation of both isotopes was observed from 1 to 18 hours of incubation and roughly equal amounts of [35S]SO4 counts were found on per cell bases in both cartilages although less [3H]glycine was incorporated by cow chondrocytes. It was also found that calf chondrocytes synthesize much greater proportion of the collagen whereas the cow cells synthesize PGs of smaller hydrodynamic sizes, bearing shorter GAG side chains that are enriched in KS (Keratan sulfate) and Ch-6S (Chondroitin-6 sulfate isomer). A failure of cow 35S-PGs monomers to interact with an exogenous HA in the presence of other extracted components was also demonstrated. The relevance of these findings for the mechanism of cartilage damage in aging and osteoarthritis is discussed.

Composition-function relationships during IL-1-induced cartilage degradation and recovery

“…Mature articular cartilage contains a significantly higher collagen fiber and collagen crosslink density 6, 54, lower PG content 54, shorter sGAG chain length 55-58, and fewer cells 59 than immature cartilage. IL-1-induced matrix degradation may be more aggressive in immature than mature cartilage due to the higher cell density, although the sensitivity of human articular cartilage to IL-1 stimulation appears to be independent of age 60.…”

Treatment of subchondral cystic lesions of the medial femoral condyle of mature horses with growth factor enhanced chondrocyte grafts: A retrospective study of 49 cases

“…Allogeneic chondrocytes are considered to be isolated from the immune response due to the implant vehicle, and later by formation of cartilage matrix. Chondrocytes from immature horses (<1 year) were used in this study because they have superior matrix synthesis and cellular division when compared with mature chondrocytes [20–22]. As chondrocytes age, they become more susceptible to oxidative stress, causing irreversible cell damage [23].…”

Two-dimensional strain fields on the cross-section of the bovine humeral head under contact loading

“…Mature and immature joints are compared to explore whether significant differences may arise due to the well-recognized evolution in material properties (Kempson, 1991; Williamson et al, 2003) and composition (Front et al, 1989; Garg and Swann, 1981; Wachtel et al, 1995) with age. The strain measurement method employed in this study, which uses digital image correlation, builds upon our earlier application in the study of cartilage explants under static loading (Wang et al, 2002).…”