Comparison of two hyaluronan drugs and placebo in patients with knee osteoarthritis. A controlled, randomized, double-blind, parallel-design multicentre study.

OBJECTIVE: To compare the efficacy and safety of intra-articular injections of two different hyaluronan preparations and placebo in patients with knee osteoarthritis. METHODS: In a randomized, patient- and observer-blind, placebo-controlled and multicentre trial with parallel groups, 210 patients, aged 60 yr or above, with knee osteoarthritis were included in a per protocol analysis. The patients were treated with three injections, once weekly, of either native high-molecular-weight hyaluronan (Artzal((R))) or cross-linked hyaluronan (Synvisc((R))) or with placebo and were followed for 52 weeks. The primary efficacy measures were weight-bearing pain during study weeks 0-26 and the duration of clinical benefit measured with Kaplan-Meier survival analysis for weeks 0-52. The secondary outcome measures were resting and maximum pain, Lequesne index, WOMAC (Western Ontario and McMaster University Osteoarthritis Index) and SF-36 (Medical Outcomes Study Short Form Health Survey) scores. RESULTS: The intra-articular injections produced a significant reduction in weight-bearing pain, resting pain, maximum pain and Lequesne and WOMAC scores after 26 weeks. There were no significant differences in outcome between any of the three study groups during the first 26 weeks. In direct comparison against placebo for weeks 0-52, neither hyaluronan treatment (Artzal or Synvisc) showed a significantly longer duration of clinical benefit than placebo. However, when data for the two hyaluronan-treated groups were pooled, treatment with hyaluronan had a significantly longer duration of benefit compared with placebo (P = 0.047). CONCLUSION: Patients with knee osteoarthritis who were treated by injection into the knee of either of two hyaluronan preparations or placebo showed clinical improvement during the first 26 weeks of treatment, though neither hyaluronan preparation gave a longer duration of clinical benefit than placebo. However, when data for the two hyaluronan treatments were pooled, there was a significantly longer duration of clinical benefit for hyaluronan treatment than for placebo.

Fluid shear stress increases the intra-cellular storage pool of tissue-type plasminogen activator in intact human conduit vessels.

We investigated the effect of shear stress on the expression of tissue-type plasminogen activator (t-PA) in intact human conduit vessels. Human umbilical veins were exposed to high or low shear stress (25 vs < 4 dyn/cm2) at identical intraluminal pressure (20 mmHg) for 1.5, 3, and 6 h in a new computerized biomechanical perfusion system. High shear perfusion induced a marked, time-dependent increase in t-PA immunostaining in both the endothelium and the media. t-PA relative to GAPDH gene expression increased by 54 +/- 14% in high- compared to low-sheared vessels (p = 0.002). By contrast, t-PA release into the perfusion medium was similar in vessels perfused under high or low shear stress conditions. The results show that shear stress independently of pressure is a potent fluid mechanical stimulus for up-regulation of the intracellular storage pool of t-PA in the vascular wall of fresh human conduit vessels. The shear effect is associated with an increased t-PA gene expression.

Elevated intraluminal pressure inhibits vascular tissue plasminogen activator secretion and downregulates its gene expression.

We recently discovered that patients with essential hypertension have a markedly impaired capacity for stimulated release of tissue plasminogen activator (tPA) from vascular endothelium. This defect may reduce the chance of timely spontaneous thrombolysis in case of an atherothrombotic event. We now investigated whether increased intraluminal pressure as such may depress vascular tPA release or downregulate its gene expression. Segments of human umbilical veins were studied in a new computerized vascular perfusion model under steady laminar flow conditions for 3 or 6 hours. Paired segments were perfused at high or physiological intraluminal pressure (40 versus 20 mm Hg) under identical shear stress (10 dyne/cm(2)). Quantitative immunohistochemical evaluation of cellular tPA immunoreactivity was performed on paraffin-embedded 5-microm vascular sections. tPA mRNA in endothelial cells was quantified with reverse transcription real-time TaqMan polymerase chain reaction with GAPDH as endogenous control. Secretion of tPA into perfusion medium was evaluated with SDS-PAGE and Western blotting, followed by densitometric quantification. High-pressure perfusion downregulated tPA gene expression with a 38% decrease in tPA mRNA levels (P=0.01) compared with vessels perfused under normal intraluminal pressure. tPA release into the perfusion medium was markedly suppressed by high pressure (P<0.01 ANOVA). The intracellular storage pool of tPA was reduced after 6 but not 3 hours. Thus, elevated intraluminal pressure downregulates tPA gene and protein expression and inhibits its release from the endothelium independently of shear stress. The defective capacity for stimulated tPA release that we demonstrated in patients with essential hypertension might thus be an effect of the elevated intraluminal pressure per se.

A new computerized biomechanical perfusion model for ex vivo study of fluid mechanical forces in intact conduit vessels.

We have developed a new computerized biomechanical ex vivo perfusion system for intact conduit vessels in which a wide range of combinations of intraluminal pressure, fluid flow and shear stress could be set and maintained at target levels in mammalian conduit vessels under controlled metabolic conditions. Mean wall shear stress is calculated using the formula: Accuracy of the wall shear stress calculation was validated by ultrasonographic imaging of the vessel radius. In a series of simulation experiments, the hemodynamic homeostasis functions of the system were challenged by generating a wide range of vascular resistance in artificial vessels and by pharmacologically induced changes in vascular tone in intact human vessels. Despite rapid changes in vessel resistance, shear stress and pressure, or flow and pressure were maintained well at target levels. Shear- and pressure-stimulated production of the vasodilator prostaglandin E2 (PGE2) was used to validate the biological relevance of the model. PGE2 release was significantly more stimulated by high (25 dyn/cm2) compared to low (<4 dyn/cm2) shear (ANOVA, p = 0.012). High compared to low intraluminal pressure depressed the production of PGE2 (ANOVA, p = 0.019). In summary, the computerized perfusion model appears to offer new possibilities of investigating the complex interplay between fluid mechanics and the vascular wall.