FRI0528 HIGH INTENSIVE THERAPEUTIC LOWERING OF SYSTEMIC CHOLESTEROL DOES NOT AMELIORATE OA DEVELOPMENT IN KNEE JOINTS OF HUMANIZED DYSLIPIDEMIC MICE

Background High systemic cholesterol levels have been associated with osteoarthritis (OA) development and lowering cholesterol using statins has been suggested as a potential treatment for OA1. Recently, novel therapeutic high-intensive cholesterol-lowering treatment has been shown to regress Western-type diet (WTD)-induced atherosclerosis in dyslipidemic APOE*3Leiden.CETP mice, a translational model with a human-like lipoprotein metabolism2. Objectives Here, we investigated the potency of these therapeutic cholesterol-lowering strategies to attenuate OA development in dyslipidemic APOE*3Leiden.CETP mice. Methods Female mice (n=13-16 per group) were fed a cholesterol-supplemented WTD for 38 weeks. After 13 weeks, mice were matched into a baseline group (sacrificed at t=13w) and 5 groups that received WTD alone or with treatment for 25 weeks: atorvastatin alone (A), in combination with PCSK9 inhibitor alirocumab (AA) or ANGPTL3 inhibitor evinacumab (AE) or triple treatment (AAE). Plasma lipids were monitored to assess metabolic dysfunction. Knee joints were analysed for cartilage degradation, synovial inflammation and osteophyte formation. Aggrecanase activity and S100A8 expression were determined using immunohistochemistry. Results Systemic administration of cholesterol-lowering interventions resulted in a significant reduction of body weight (A: -16%; AA: -8%; AE: -12%; AAE: -18% at end point) without changes in food intake. WTD-feeding manifested itself in dyslipidemia, with high cholesterol levels that were significantly reduced after administration of therapeutic cholesterol-lowering interventions (A: -46%; AA: -74%; AE: -74%; -AAE: 86% at end point). Using detailed OARSI scoring, dyslipidemic mice showed a mild but significant increase in cartilage degeneration at end point (7.8 ± 1.9) compared to baseline controls (3.8 ± 1.8, 2.1-fold increase, p=0.001), and a strong 52-fold increase in NITEGE staining, representing proteolytic activity by aggrecanases3. However, therapeutic cholesterol lowering did not ameliorate further progression of cartilage destruction. This was supported by comparable NITEGE staining in all treatment groups at end point. Dyslipidemic APOE*3Leiden.CETP mice developed minor synovial inflammation which was not affected by cholesterol-lowering interventions. Alarmin S100A8, a marker for macrophage activation, showed minor expression in the synovial lining of all treatment groups, supporting the absence of joint inflammation in this model4. Finally, we determined whether high plasma cholesterol levels promoted osteophyte formation. The total number of osteophytes and osteophyte maturation stage was comparable between all groups despite reduction of systemic cholesterol levels. Conclusion Therapeutic cholesterol-lowering interventions did not slow the progression of cartilage degradation and osteophyte formation in dyslipidemic APOE*3Leiden.CETP mice with minor joint inflammation. These findings suggest that therapeutic cholesterol-lowering interventions in the absence of local inflammation within the knee joint cannot prevent progression of OA. References [1] Gierman, LM, Ann Rheum Dis, 2014; 73, 921-927. [2] Dewey, F.E., New Engl J Med2017; 377, 211-221. [3] van Meurs JB, Arthritis Rheum42, 1999; 42, 1128-1139. [4] van Lent PL, Arthritis & Rheumatism2012; 64, 1466-1476. Disclosure of Interests None declared