20. DELETERIOUS EFFECTS OF INTRA-SYNOVIAL BLOOD ON JOINT LUBRICATION BY SYNOVIAL FLUID

Department: Bioengineering
Faculty Advisor(s): Robert Sah

Primary Student
Name: Jennifer Megan Antonacci
Email: jantonac@ucsd.edu
Phone: 858-534-5682
Grad Year: 2010

Abstract
Blood is introduced into the joint space in a number of clinical situations ranging from sports-related injuries of joint tissues to trauma with an intra-articular fracture. The mixture of blood with synovial fluid (SF) may be harmful to synovial joints through a number of mechanisms. We hypothesized that a distinct mechanism by which blood adversely affects synovial joints is by altering the lubrication function of SF. Normally, SF protects articular cartilage against friction and wear through the action of lubricant molecules, including hyaluronan (HA). Blood may affect SF lubrication of cartilage by modulating the fluid lubricant components of SF and by introducing blood cells. The objectives of this study were to analyze the (1) cartilage lubrication properties of SF+blood mixtures versus the fluid component of the mixture and (2) distribution of protein and HA between fluid and blood cell fractions.

The friction coefficient was affected by the presence of blood. The friction coefficients for PBS, 10% SF, and the mixture of 10%SF:90%blood were 0.107, 0.059, and 0.174, respectively, indicating that blood was deleterious to lubrication properties. The friction coefficient of the supernatant of a 10% SF:90% blood mixture, 0.117, was less than that of the mix indicating that the blood cells had a deleterious effect. After the cartilage was exposed to whole blood the friction coefficient was high compared to that of SF on fresh cartilage.

Biochemical analysis of the SF:blood mixtures, supernatants, and pellets revealed a differential localization of chemical constituents. Protein separated between the pellet and supernatant. In contrast, HA was primarily in the supernatant, indicating it was maintained in the fluid phase even when SF was mixed with blood. Consistent with this, the total amount of protein and HA in the supernatant and pellet fractions were similar to that of the corresponding mixtures before centrifugation as well as the proportionate amounts from the pure SF and blood preparations.

These results indicate that blood is deleterious to the lubrication qualities of SF. The effect of blood plasma components was more deleterious than a simple dilution effect of SF, suggesting possible interactions between plasma proteins and lubricant molecules in SF. The effect of whole blood was more deleterious than just the supernatant, suggesting that blood cells interfere with SF lubrication of cartilage. Because of these effects, cleansing and replenishment of the synovial space with normal SF or SF constituents may prevent cartilage deterioration due to a poor lubricant environment.

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