Surface-active phospholipid as the lubricating component of lubricin

Schwarz, Irene; Hills, B. A.

doi:10.1093/rheumatology/37.1.21

Cited by 151 publications

(117 citation statements)

References 31 publications

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“…In the present study, SAPL in the form of DPPC at a physiologic concentration of 200 g/ml did not significantly lower Ͻ kinetic, Neq Ͼ alone ( Figure 5B), with Ͻ kinetic, Neq Ͼ for DPPC remaining ϳ5-fold greater than that for SF, or in combination with HA and PRG4 ( Figure 6B). Additionally, because the PRG4 preparation tested in the present study was free of SAPL in appreciable quantities (Ͻ0.5 g/ml), SAPL were not indirectly contributing to the boundary-lubricating ability of PRG4, as has been postulated as a complicating consideration (49).…”

Section: Discussionmentioning

confidence: 78%

Boundary lubrication of articular cartilage: Role of synovial fluid constituents

Schmidt

Gastelum

Nguyen

et al. 2007

Arthritis & Rheumatism

480

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: 78%

Boundary lubrication of articular cartilage: Role of synovial fluid constituents

Schmidt

Gastelum

Nguyen

et al. 2007

Arthritis & Rheumatism

480

510

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“…Given its antiadhesive capacity (Swann et al, 1985;Schwarz and Hills, 1998), lubricin could have a key role in the very first steps in cavity formation that likely require detachment of neighboring tissue layers and creation of an intervening liquid-filled space. This initial critical step would then be followed by enlargement and further filling of the cavities and by muscle movement, known to be critical for joint functional establishment (Lelkes, 1958;Mitrovic, 1982;Mikic et al, 2000); lubricin would at that point act also as a critical lubricant.…”

Section: Disc and Joint Cavitiesmentioning

confidence: 99%

Temporomandibular joint formation and condyle growth require Indian hedgehog signaling

Shibukawa¹,

Young²,

Wu³

et al. 2006

Developmental Dynamics

131

174

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The temporomandibular joint (TMJ) is essential for jaw function, but the mechanisms regulating its development remain poorly understood. Because Indian hedgehog (Ihh) regulates trunk and limb skeletogenesis, we studied its possible roles in TMJ development. In wild-type mouse embryos, Ihh expression was already strong in condylar cartilage by embryonic day (E) 15.5, and expression of Ihh receptors and effector genes (Gli1, Gli2, Gli3, and PTHrP) indicated that Ihh range of action normally reached apical condylar tissue layers, including polymorphic chondroprogenitor layer and articular disc primordia. In Ihh ؊/؊ embryos, TMJ development was severely compromised. Condylar cartilage growth, polymorphic cell proliferation, and PTHrP expression were all inhibited, and growth plate organization and chondrocyte gene expression patterns were abnormal. These severe defects were partially corrected in double Ihh ؊/؊ /Gli3؊/؊ mutants, signifying that Ihh action is normally modulated and delimited by Gli3 and Gli3 R in particular. Both single and double mutants, however, failed to form an articular disc primordium, normally appreciable as an independent condensation between condylar apex and neighboring developing temporal bone in wild-type. This failure persisted at later stages, leading to complete absence of a normal functional disc and lubricin-expressing joint cavities. In summary, Ihh is very important for TMJ development, where it appears to regulate growth and elongation events, condylar cartilage phenotype, and chondroprogenitor cell function. Absence of articular disc and joint cavities in single and double mutants points to irreplaceable Ihh roles in formation of those critical TMJ components. Developmental Dynamics 236:426 -434, 2007.

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“…7,15 Such chains could also mediate noncovalent binding of PRG4 to cartilage matrix molecules, including collagens 16 and fibronectins 17,18 at or near the articular surface. Another possibility is that PRG4-surface binding is lipid mediated, as PRG4 has been shown to contain up to 11% lipid, 19 and this interaction may involve hydrophobic 20 or hydrophilic attraction. 21 Finally, PRG4 attachment to the articular surface may be maintained by disulfide bond formation, via the unmatched cysteine residue near the C-terminus.…”

Section: Introductionmentioning

confidence: 99%

PRG4 exchange between the articular cartilage surface and synovial fluid

Nugent-Derfus

Chan

Schumacher

et al. 2007

Journal Orthopaedic Research

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ABSTRACT:The boundary lubrication function of articular cartilage is mediated in part by proteoglycan 4 (PRG4) molecules, found both in synovial fluid (SF) and bound to the articular cartilage surface. Currently the mechanism by which PRG4 binds to the articular surface is not well understood. The objectives of this study were to determine (1) the effect of bathing fluid contents on PRG4 concentration at the articular surface ([PRG4] cart ), and (2) whether native PRG4 can be removed from the surface and subsequently repleted with PRG4 from synovial fluid. In one experiment, cylindrical cartilage disks were stored in solutions of various PRG4 concentrations, either in phosphate-buffered saline (PBS) or SF as the carrier fluid. In a separate experiment, cartilage disks were stored in solutions expected to remove native PRG4 from the articular surface and allow subsequent repletion with PRG4 from SF. [PRG4] cart was independent of PRG4 concentration of the bathing fluid, and was similar for both carrier fluids. PRG4 was removed from cartilage by treatment with hyaluronidase, reduction/alkylation, and sodium dodecyl sulphate, and was repleted fully by subsequent bathing in SF. These results suggest that the articular surface is normally saturated with tightly bound PRG4, but this PRG4 can exchange with the PRG4 in SF under certain conditions. This finding suggests that all tissues surrounding the joint cavity that secrete PRG4 into the SF may help to maintain lubrication function at the articular surface. ß

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Surface-active phospholipid as the lubricating component of lubricin

Cited by 151 publications

References 31 publications

Boundary lubrication of articular cartilage: Role of synovial fluid constituents

Boundary lubrication of articular cartilage: Role of synovial fluid constituents

Temporomandibular joint formation and condyle growth require Indian hedgehog signaling

PRG4 exchange between the articular cartilage surface and synovial fluid

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