Biologic Characteristics of Shoulder Articular Cartilage in Comparison to Knee and Ankle Articular Cartilage From Individual Donors

Objective To describe histological and metabolic characteristics of glenohumeral joint (GHJ) articular cartilage and compare to knee and ankle joints. Design Macroscopically healthy human humeral head, glenoid, knee, and ankle articular cartilage were obtained from tissue donors ( N = 16, 9 males, 7 females; age 45-78 years), within 24 hours of death. Gross morphology of each joint was assessed using Collins grading. Cartilage explants were removed from the entire surface of each joint, cultured for 48 hours with or without interleukin-1β and processed for histology with Safranin O, proteoglycan (PG) synthesis/content, and polymerase chain reaction for collagen II, aggrecan, and SOX9. Results were compared between uncultured and cultured controls and across all 3 joints. Results Structural differences were seen on histology between GHJ cartilage and knee and ankle cartilage of the same Collins grade, specifically, depletion of Safranin O staining in the extracellular matrix. Treatment of glenoid and humerus specimens with IL-1β demonstrated a trend toward decreased PG synthesis in each explant but this decrease did not reach significance. There was no significant difference in PG synthesis between humerus, glenoid, knee, and ankle samples at baseline, day-0 control, 48-hour control, and 48 hours after treatment with 0.1 ng or 10 ng of IL-1β. There were no significant increases in collagen II, SOX9, and aggrecan expression in glenoid and humeral head cartilage samples treated with IL-1β compared to baseline controls. Conclusions GHJ articular cartilage did not significantly differ from ankle or knee cartilage with regard to PG synthesis and gene expression. However, it did differ in its histological appearance in normal state. </jats:sec

Protective effect of P188 in the Model of Acute Trauma to Human Ankle Cartilage: The Mechanism of Action

OBJECTIVE: Since P188 poloxamer is effective in promoting cell survival in models of acute trauma the objectives were to understand the mechanism of its action focusing on GSK3 activation, IL-6 and p38 signaling. DESIGN: Sixteen normal human tali were impacted using 4mm diameter indenter with an impulse of 1Ns. 8mm cartilage plugs containing the 4mm impacted core and 4mm adjacent non-impacted ring were removed and cultured with or without P188. Cell lysates were analyzed using Western blots with antibodies against total and phosphorylated ERK, JNK, p38, ATF-2, GSK3, Stat1 and Stat3. Additional tests were performed with the p38 inhibitor (p38i) SB203580. RESULTS: Studied pathways were activated after impaction with the peak of activity at 1hour. P188 completely attenuated phosphorylation of Stat1 and ATF-2 and inhibited p38, Stat3, JNK, ERK, and GSK3. The p38i partially offset phosphorylation of Stat3, GSK3, and ERK suggesting a role of p38 in these three pathways. Additionally, the p38i improved cell survival (p=0.053) and reduced apoptosis (by about 20%, p=0.046, vs almost 40% by P188) thus confirming that P188 acts (at least in part) via p38 pathway. CONCLUSION: Our results report a novel mechanism through which P188 exerts its protective effects on cartilage in the model of acute injury. In addition to its effect on cellular membrane, P188 affects stress-related p38 signaling, apoptosis-related GSK3, and inflammation-related IL-6 signaling. Taken together these findings suggest that P188 alone or in combination with pro-anabolic agents may have a therapeutic potential in preventing progressive cartilage degeneration and the development of post-traumatic osteoarthritis