67. synovial fluid : serum ratio of protein concentration is increased in experimental osteoarthritis and inversely correlated with synovial fluid hyaluronan concentration

Department: Bioengineering
Faculty Advisor(s): Robert L. Sah

Primary Student
Name: Aimee Rose Raleigh
Email: araleigh@ucsd.edu
Phone: 650-454-0605
Grad Year: 2018

INTRODUCTION: In joints, low-friction lubrication is mediated by synovial fluid (SF), which is formed as blood plasma is filtered through the size-selective capillary and synovial lining (SL) ?membranes.? SF protein concentration (cSFprotein) is generally increased in arthritis, especially for high molecular mass (Mr) proteins. Such changes can be quantified by the SF to serum concentration ratio (kSF:SMr), reflecting, in part, the size-selectivity of filtration between the joint space and capillaries. In post-traumatic osteoarthritis (PTOA), the concentration of hyaluronan (HA, cSFHA), a key lubricant, is decreased. Theoretically, cSFHA is inversely proportional to the permeability to HA of the SF:serum interface. Permeability is variably increased in the anterior cruciate ligament transection (ACLT) model of PTOA and may affect both cSFHA and kSF:SMr. We tested the hypotheses that kSF:SMr is elevated in ACLT PTOA and is correlated with decreased cSFHA. METHODS: Rabbits underwent ACLT surgery in the right knee, with the left knee as non-operated control (Non-OP). Rabbits were sacrificed at 1, 4, 7, 14, 28, and 42 days post-ACLT (n=6-7/group) and SF and serum were collected. Protein in SF (cSFprotein) and serum (cSerumprotein) were quantified via BCA assay. Samples were separated by 4-12% PAGE. Protein distribution in gels was quantified by SYPRO Ruby staining and fluorescence imaging. Gel images were processed for protein distribution in Mr bins to quantify major protein bands. The protein concentrations overall and within each Mr bin for SF and serum, collected from the same animal, were used to calculate the concentration ratios kSF:S and kSF:SMr. The concentration of HA in SF (cSFHA) was determined by an enzyme-linked binding assay. Data are mean SE. The effects of ACLT vs. Non-OP and time post-injury were analyzed by 2-way rmANOVA. Relationships between kSF:S and cSFHA were assessed by linear regression. RESULTS: cSFprotein and kSF:S were affected by ACLT (p<0.01) and, interactively, by ACLT and time after surgery (p<0.05), without effects of time (p=0.87). cSFprotein and kSF:S were higher in ACLT vs. Non-OP knees at 4, 7, and 28 days post-injury (+25-75%). Depending on Mr, kSF:SMr was variably affected by ACLT at early (1-7 days) or later (28-42 days) time. Overall HA and overall protein kSF:S were related, with cSFHA decreased with increasing kSF:S (r2=0.40, p<0.001). DISCUSSION: The inverse relationship between kSF:S and cSFHA suggests that increased kSF:S reflects increased permeability, which in turn is at least partially responsible for the decrease in SF HA lubricant concentration during PTOA.

Industry Application Area(s)
Life Sciences/Medical Devices & Instruments

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