Identification of Distinct Metabolic Pools of Aggrecan and Their Relationship to Type VI Collagen in the Chondrons of Mature Bovine Articular Cartilage Explants

Friction and wear of four common orthopaedic biomaterials, alumina (Al2O3), cobalt-chromium (CoCr), stainless steel (SS), and crosslinked ultra-high-molecular-weight polyethylene (UHMWPE), sliding against bovine articular cartilage explants were investigated by reciprocating sliding, nanoscale friction and roughness measurements, protein wear assays, and histology. Under the experimental conditions of the present study, CoCr yielded the largest increase in cartilage friction coefficient, largest amount of protein loss, and greatest change in nanoscale friction after sliding against cartilage. UHMWPE showed the lowest cartilage friction coefficient, least amount of protein loss, and insignificant changes in nanoscale friction after sliding. Although the results are specific to the testing protocol and surface roughness of the examined biomaterials, they indicate that CoCr tends to accelerate wear of cartilage, whereas the UHMWPE shows the best performance against cartilage. This study also shows that the surface characteristics of all biomaterials must be further improved to achieve the low friction coefficient of the cartilage/cartilage interface.

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Latrunculin and Cytochalasin Decrease Chondrocyte Matrix Retention

Journal of Histochemistry & Cytochemistry ◽

10.1177/002215540205001004 ◽

2002 ◽

Vol 50 (10) ◽

pp. 1313-1323 ◽

Cited By ~ 24

Author(s):

Ghada A. Nofal ◽

Cheryl B. Knudson

Keyword(s):

Articular Cartilage ◽

Actin Cytoskeleton ◽

Cartilage Explants ◽

Cartilage Tissue ◽

Pericellular Matrix ◽

Matrix Assembly ◽

Tissue Slices ◽

Cd44 Expression ◽

Bovine Articular Cartilage ◽

Cytoskeletal Disruption

The proteoglycan-rich extracellular matrix (ECM) directly associated with the cells of articular cartilage is anchored to the chondrocyte plasma membrane via interaction with the hyaluronan receptor CD44. The cytoplasmic tail of CD44 interacts with the cortical cytoskeleton. The objective of this study was to determine the role of the actin cytoskeleton in CD44-mediated matrix assembly by chondrocytes and cartilage matrix retention and homeostasis. Adult bovine articular cartilage tissue slices and isolated chondrocytes were treated with latrunculin or cytochalasin. Tissues were processed for histology and chondrocytes were examined for CD44 expression and pericellular matrix assembly. Treatments that disrupt the actin cytoskeleton reduced chondrocyte pericellular matrix assembly and the retention of proteoglycan within cartilage explants. There was enhanced detection of a neoepitope resulting from proteolysis of aggrecan. Cytoskeletal disruption did not reduce CD44 expression, as monitored by flow cytometry, but detergent extraction of CD44 was enhanced and hyaluronan binding was decreased. Thus, disruption of the cytoskeleton reduces the anchorage of CD44 in the chondrocyte membrane and the capacity of CD44 to bind its ligand. The results suggest that cytoskeletal disruption within cartilage uncouples chondrocytes from the matrix, resulting in altered metabolism and deleterious changes in matrix structure.

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