Browsing by Author "Barton, Kristen"

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    Characterization of proteoglycan 4 and hyaluronan composition and function of ovine synovial fluid following knee surgery
    (2012-08-16) Barton, Kristen; Frank, Cyril; Schmidt, Tannin
    Osteoarthritis is a degenerative joint disease involving the breakdown of articular cartilage, which is common after injury or with aging. Cartilage lubrication is a vital mechanism for the protection and maintenance of joints. Proteoglycan 4 (PRG4), a glycoprotein present in synovial fluid (SF), contributes to the boundary lubrication of cartilage and maintenance of the joint. PRG4 also acts synergistically with hyaluronan (HA), another molecule present in SF, as cartilage boundary lubricants. The objective of this thesis was to determine 1) PRG4 and HA concentration, 2) HA molecular weight (MW) distribution, 3) cartilage lubricating ability, and 4) the isoelectric point (pI) of PRG4 in SF from surgical sham (SHAM), anterior cruciate ligament (ACL)/medial collateral ligament (MCL) transection, and lateral meniscectomy (MEN) in a post-knee injury ovine model at 20 weeks. SHAM (n=5), ACL/MCL transection (n=6), and MEN (n=5) ovine SF (oSF) was collected at euthanization 20 weeks after surgery, with the left joint serving as the non-operative control (CTRL). PRG4 and HA concentration in oSF was measured by a sandwich enzyme-linked immunosorbent assay (ELISA) and HA MW distribution by agarose gel electrophoresis. A cartilage-cartilage friction test under boundary lubrication conditions was used to assess the cartilage lubricating ability of oSF. The pI of PRG4 was determined by twodimensional (2D) gel electrophoresis. PRG4 and HA concentration in SHAM, ACL/MCL, and MEN oSF was similar in comparison to the contralateral CTRL oSF. The HA MW distribution in the SHAM, ACL/MCL, and MEN oSF for all ranges were similar with respect to the contralateral CTRL oSF. The kinetic coefficient of friction in phosphate buffered saline was significantly higher than all groups, both operated, CTRL oSF, and bovine SF in all cases, which was lower and similar. The pI of PRG4 is ~4.0-4.4 and the pI of PRG4 may have shifted to a higher pI in MEN oSF, in compared to contralateral CTRL oSF. These results suggest that lubricant composition and function was normal 20 weeks post-knee surgery in this model and 2D electrophoresis may provide insight into the structure of PRG4 glycosylations.
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    Use of a Glucocorticoid to Mitigate Post-Traumatic Osteoarthritis Development in the Ovine Knee
    (2017) Barton, Kristen; Hart, David; Shrive, Nigel; Fritzler, Marvin; Hildebrand, Kevin
    After knee ligament injury, specifically anterior cruciate ligament (ACL) injury, the articular surface frequently becomes damaged and can lead to post-traumatic osteoarthritis (PTOA). PTOA is a common joint disease and involves the breakdown of the cartilage that covers the ends of the articular joint-bone interface. PTOA development can be attributed to many factors, two of which may be altered kinematics and joint inflammation. Presently, no treatment options are effective in slowing PTOA progression. Therefore, it is crucial to better understand both joint biomechanics and inflammation. Further, studying interventions that have the potential to mitigate inflammation is necessary to find strategies that may prevent the damage from setting in. Therefore, the rationale for this thesis was to 1) determine if partial ACL (p-ACL) transection (Tx) model leads to PTOA (Project A), 2) determine if p-ACL Tx leads to kinematic alterations (Project B), and 3) determine if p-ACL Tx induced joint inflammation can be modified by glucocorticoid (GC) treatment (Project C). We hypothesized that early inflammation following p-ACL Tx in an ovine model would initiate degeneration of the knee joint and that methylprednisolone acetate (MPA; Depo-Medrol®) treatment would mitigate injury-related PTOA development. Furthermore, MPA would provide a mechanism of long-term prevention to joint damage by suppressing acute inflammation. The results showed that p-ACL Tx led to significantly more combined gross damage at 40 weeks post p-ACL Tx than the control group. There was considerable inter-subject variability following p-ACL knee injury within animals. There were consistent changes in medial-lateral, posterior-anterior, and inferior-superior translations at 40 weeks from intact to after p-ACL Tx. In normal explants, MPA treatment suppressed IL-1β induced mRNA levels for matrix metalloproteinases (MMPs) in articular cartilage, synovium, and infrapatellar fat pad (IPFP) and was found to be tissue-, location-, and gene-specific. Although the gross damage was not significant at 20 weeks post p-ACL Tx compared to the control group, there were trends indicating that the damage was progressive over time and that MPA mitigated gross damage at 20 weeks post p-ACL Tx. The in vivo 20 week studies provided efficacy to determine if we could detect changes early. However, perhaps a greater differential in PTOA damage is necessary to see an impact of GC treatment in a long- term model, comparable to that observed in the 40 weeks post p-ACL Tx group. Last, there were no significant bone changes at either the early 20 weeks post p-ACL Tx or the advanced 40 weeks post p-ACL Tx, compared to non-operative control tibias in any of the subchondral bone layers, thus suggesting the degree of joint instability (full ACL Tx vs. p-ACL Tx) appears to influence the response in bone microarchitecture.