Hyaluronan Concentration In Synovial Fluid Research Articles

First in vivo detection and characterization of hyaluronan-coated extracellular vesicles in human synovial fluid.

Extracellular vesicles (EVs) function in intercellular signaling by transporting different membrane and cytosolic molecules, including hyaluronan (HA) and its synthesis machinery. As both EVs and HA are abundant in synovial fluid, we hypothesized that HA synthesized in synovial membrane would be carried on the surface of EVs. Synovial fluid (n = 15) and membrane samples (n = 5) were obtained from knee surgery patients. HA concentrations were analyzed in synovial fluid and HA and its synthesis machinery were examined with histochemical stainings in synovial membrane. To assess the size distribution of EVs in synovial fluid and to visualize HA on EVs, nanoparticle tracking analysis (NTA), confocal laser scanning microscopy (CLSM) and transmission electron microscopy (TEM) were utilized. The average HA concentration in synovial fluid was 2.0 ± 0.21 mg/ml without significant differences between the patients with trauma/diagnostic arthroscopy and primary or post-traumatic osteoarthritis. Positive stainings of HA synthases (HAS1-3), HA and its receptor CD44 in synovial cells indicated active HA secretion in synovial membrane. According to NTA, EVs were abundant in synovial fluid and their main populations were ≤300 nm in diameter after differential centrifugation. There were no significant differences in the EV counts between the patients with primary or post-traumatic osteoarthritis. TEM verified that HA-positive particles detected by CLSM were lipid membrane vesicles surrounded by a HA coat. Our results provide the first in vivo evidence that human synovial fluid contains HA-positive EVs, one source of which presumably is the long HAS-positive protrusions of synovial fibroblasts. © 2016 Orthopaedic Research Society. Published by Wiley Periodicals, Inc. J Orthop Res 34:1960-1968, 2016.

The biophysical mechanisms of altered hyaluronan concentration in synovial fluid after anterior cruciate ligament transection

The residence time of hyaluronan (HA) in knee joint synovial fluid (SF) was investigated using a rabbit anterior cruciate ligament transection (ACLT) model. The aims of this study were to assess, at 7 and 28 days after surgery, the 1) HA concentration and molecular mass (M(r) ) distribution in the SF, 2) endogenous replenishment of HA after saline washout, 3) HA residence times in the SF, and 4) synovium and subsynovium cellularity of the knee joints of rabbits subjected to ACLT, compared to sham-operated and nonoperated control joints. Adult NZW rabbits underwent ACLT or sham surgery on one hind limb, while each contralateral limb was the nonoperated control. On day 7 or 28 after surgery, the joints were aspirated for SF, lavaged with saline, and injected with saline or polydisperse HA, and samples were obtained for analysis at set time points up to 8 hours after injection. Joint fluid samples were analyzed for the concentration and M(r) distribution of HA to calculate the HA residence time constant. Analysis of HA concentrations and M(r) distributions showed 1) loss of high-M(r) HA in the SF on day 7 and a shift toward a lower-M(r) distribution on day 28, 2) endogenous replenishment of high-M(r) HA after washout, and 3) M(r) -dependent loss of HA from the knee joints after ACLT, particularly on day 7 postsurgery. The HA residence time decreased with decreasing HA M(r) (residence time ∼27 hours with an M(r) load of 7,000-2,500 kd, to ∼7 hours with an M(r) load of 250-50 kd). HA residence time also decreased (by ∼70%) in the knee joints on day 7 after ACLT. The subsynovium of the joints subjected to ACLT displayed increased cellularity and neovascularization on days 7 and 28 postsurgery. The residence time of HA in the SF is transiently decreased after ACLT, suggesting that a biophysical transport mechanism is responsible for the altered composition of the SF after joint injury or during inflammation.

Clinical and biochemical characteristics after intra-articular injection for the treatment of osteoarthritis of the knee: prospective randomized study of sodium hyaluronate and corticosteroid

BackgroundIntra-articular injections of sodium hyaluronate (Na-HA) and corticosteroid (CS) are often used for the treatment of osteoarthritis (OA), and the clinical usefulness of such treatment has been reported. Some studies have discussed the effectiveness of intra-articular drug injection therapy in terms of the clinical results, but no cohort studies have performed evaluations of effectiveness based on changes in joint biomarkers. This prospective randomized study compared the efficacy of Na-HA and CS injections based on clinical scores and levels of biochemical markers for osteoarthritis. MethodsA total of 51 patients with knee osteoarthritis received intra-articular injections of either Na-HA or CS and were followed for 6 months after treatment. Pain and inflammatory scores were evaluated at the baseline, at 5 weeks, and at 6 months. We also measured joint fluid levels of hyaluronan (HA), chondroitin 6-sulfate, chondroitin 4-sulfate, matrix metalloproteinase (MMP)-9, and tissue inhibitor of MMP (TIMP)-1 at the baseline and at 5 weeks. ResultsIn both groups, injection therapy significantly improved pain/inflammation scores and visual analog scale scores with time (P < 0.01). HA levels were significantly increased after injection only in the Na-HA group (P < 0.05); and the MMP-9 level decreased significantly after injection only in the Na-HA group (P < 0.01). Other marker levels did not differ significantly between groups. ConclusionsThe results of this prospective randomized study suggest that the clinical effects of Na-HA and CS as local therapies for OA are comparable and that both drugs are useful. Considering the results of the measurement of biomarkers, compared with CS injection therapy Na-HA injection therapy may have protective effects on the articular cartilage by increasing the HA concentration in synovial fluid, as well as inhibitory effects on the catabolism of articular cartilage by reducing the MMP-9 concentration.

Concentration Dependence of Interstitial Flow Buffering by Hyaluronan in Synovial Joints

Hyaluronan concentration in synovial fluid spans a 20-fold range, from as low as 0.2 mg ml−1 in synovitis to as high as 4 mg ml−1 in healthy joints. The aim was to determine the effect of this on fluid drainage from the joint cavity. The study extends the finding of P. J. Coleman, D. Scott, R. M. Mason, and J. R. Levick (1999, J. Physiol. 514, 265–282) that dissolved hyaluronan at 3.6–4.0 mg ml−1 (the concentration in young human and rabbit joints) causes the opposition to interstitial fluid drainage to increase with pressure. Hyaluronan was infused into rabbit knees at 0, 0.2, 2.0, and 4.0 mg ml−1 over a range of intraarticular pressures. Hyaluronan at 2 mg ml−1 (as in healthy elderly joints and some osteoarthritis) greatly reduced drainage rates and generated a flattening (convex) pressure-flow relation, as observed previously with 4 mg ml−1. Drainage rates were greater at 2 mg ml−1 than at 4 mg ml−1 hyaluronan (P < 0.0001, ANOVA, n = 7). The opposition to outflow (pressure required to drive unit outflow) increased with pressure, but less markedly than with 4 mg ml−1 hyaluronan. Hyaluronan at 0.2 mg ml−1 reduced outflow by ∼50% relative to Ringer solution (P < 0.0001, ANOVA, n = 7) but the pressure-flow relation no longer flattened out with increasing pressure, because there was no significant increase in opposition to outflow with pressure. At 0 mg ml−1 hyaluronan, outflow opposition decreased with pressure. Viscometry showed a marked transition in the hyaluronan state at ≥1.35 mg ml−1, indicating that this is the critical concentration for molecular domain overlap and intermolecular coupling. The results broadly supported the concentration-polarization hypothesis, which predicts significant osmotic buffering of drainage at ≥1 mg ml−1 hyaluronan; at 0.2 mg ml−1 other factors may predominate. It is inferred that hyaluronan at physiological concentrations can conserve synovial fluid when pressures are raised (e.g., flexion): whereas dilution of hyaluronan, as in severe effusions, can effectively abolish buffering and thus facilitate fluid drainage.