A Novel Proteoglycan Synthesized and Secreted by Chondrocytes of the Superficial Zone of Articular Cartilage

Schumacher, Barbara L.; Block, Joel A.; Schmid, Thomas; Aydelotte, Margaret B.; Kuettner, Klaus E.

doi:10.1006/abbi.1994.1219

Cited by 329 publications

(318 citation statements)

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“…SF is composed of HA ranging from 2,000 kd to 10,000 kd (30,44), PRG4 proteins ranging from ϳ14 kd to ϳ345 kd (4,45), and SAPL of different types with DPPC being a major form (33). HA has been shown to lubricate at a cartilage-cartilage interface on a joint scale equally well at 1,030 kd and 1,930 kd (14), and certain other properties of HA do not depend on molecular weight either (in the range of 500-6,000 kd) (46).…”

Section: Discussionmentioning

confidence: 99%

“…Culture medium was changed every 3 days and collected for processing. To purify PRG4, the conditioned culture medium was saved, pooled, and fractionated by anion-exchange chromatography essentially as described previously (4). Briefly, the sample was applied onto DEAE-Sepharose, previously equilibrated with 0.15M NaCl, 0.005M EDTA, and 0.05M sodium acetate, pH 6.0.…”

Section: Methodsmentioning

confidence: 99%

“…This mode of lubrication has been proposed to be important for the protection and maintenance of articular surfaces since the apposing cartilage layers within the joint make contact over ϳ10% of the total area, where much of the friction may occur (2). Synovial fluid (SF) contains the molecules hyaluronan (HA) (3), proteoglycan 4 (PRG4) (the name assigned by the Human Genome Organization Gene Nomenclature Committee for proteins also known as lubricin, superficial zone protein, and megakaryocyte-stimulating factor) (4,5), and surface-active phospholipids (SAPL) (6), each of which interacts with and adsorbs to the articular surface. Such molecules are all ideally positioned to contribute to boundary lubrication.…”

mentioning

confidence: 99%

“…The lubricating ability of HA has been assessed at cartilage-cartilage (14)(15)(16)(17)(18), cartilage-steel (19), and cartilage-glass interfaces (18,20), as well as at a latex-glass interface under boundary lubrication conditions (12,21), with variable conclusions, possibly due to the different test surfaces and configurations and the various resulting operative modes of lubrication. Conversely, PRG4 proteins (22), which are synthesized and secreted by cells lining the synovial cavity (4,5), have consistently demonstrated boundary-lubricating ability at both cartilage-glass (23) and latex-glass interfaces (12,21,24,25). Studies examining the lubricating ability of SAPL at a cartilage-cartilage interface (in combination with HA) (19) and at a cartilage-steel interface (19,26), as well as at a latex-glass interface under boundary lubrication conditions (13), suggest that SAPL may also possess boundary-lubricating ability.…”

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confidence: 99%

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Boundary lubrication of articular cartilage: Role of synovial fluid constituents

Schmidt

Gastelum

Nguyen

et al. 2007

Arthritis & Rheumatism

459

510

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Objective. To determine whether the synovial fluid (SF) constituents hyaluronan (HA), proteoglycan 4 (PRG4), and surface-active phospholipids (SAPL) contribute to boundary lubrication, either independently or additively, at an articular cartilage-cartilage interface.Methods. Cartilage boundary lubrication tests were performed with fresh bovine osteochondral samples. Tests were performed using graded concentrations of SF, HA, and PRG4 alone, a physiologic concentration of SAPL, and various combinations of HA, PRG4, and SAPL at physiologic concentrations. Static ( static, Neq ) and kinetic (< kinetic, Neq >) friction coefficients were calculated.Results. Normal SF functioned as an effective boundary lubricant both at a concentration of 100% (< kinetic, Neq > ‫؍‬ 0.025) and at a 3-fold dilution (< kinetic, Neq > ‫؍‬ 0.029). Both HA and PRG4 contributed independently to a low in a dose-dependent manner. Values of < kinetic, Neq > decreased from ϳ0.24 in phosphate buffered saline to 0.12 in 3,300 g/ml HA and 0.11 in 450 g/ml PRG4. HA and PRG4 in combination lowered further at the high concentrations, attaining a < kinetic, Neq > value of 0.066. SAPL at 200 g/ml did not significantly lower , either independently or in combination with HA and PRG4. Conclusion. The results described here indicate that SF constituents contribute, individually and in combination, both at physiologic and pathophysiologic concentrations, to the boundary lubrication of apposing articular cartilage surfaces. These results provide insight into the nature of the boundary lubrication of articular cartilage by SF and its constituents. They therefore provide insight regarding both the homeostatic maintenance of healthy joints and pathogenic processes in arthritic disease.

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Section: Discussionmentioning

confidence: 99%

Section: Methodsmentioning

confidence: 99%

mentioning

confidence: 99%

mentioning

confidence: 99%

See 2 more Smart Citations

Boundary lubrication of articular cartilage: Role of synovial fluid constituents

Schmidt

Gastelum

Nguyen

et al. 2007

Arthritis & Rheumatism

459

510

View full text Add to dashboard Cite

show abstract

“…It is synthesized by synovial cells [1,24] and plays an important role in joint lubrication [15,31]. Subsequent reports indicate another protein, superficial zone protein synthesized by superficial zone chondrocytes [26], is homologous to megakaryocyte stimulating factor [7] and lubricin [14] and that these proteins are products of the megakaryocyte stimulating factor gene [14]. Proteoglycan 4 is another name collectively given to these homologous glycoproteins encoded by 12 exons of the gene, also known as Prg4 [6].…”

Section: Introductionmentioning

confidence: 99%