Intra-articular delivery of VEGF targeting miR-126-3p and miR-140-5p ameliorates synovitis and pain in a rat model of post-traumatic knee osteoarthritis

Background/objective Knee osteoarthritis (KOA) is the most common joint disorder and causes pain and functional limitation. Patients who are refractory to conservative treatment or unsuitable for surgery owing to advanced age or comorbidities have limited options. Vascular endothelial growth factor (VEGF) is implicated in synovitis, angiogenesis and pain in KOA. microRNA (miRNA) based therapies have recently attracted attentions. This study aimed to investigate whether intra-articular delivery of VEGF-targeting miRNA can reduce synovitis and pain. Methods Human synovial sarcoma cell line HS-SY-II was used for screening of VEGF-targeting miRNAs and primary synovial fibroblasts derived from KOA patients was used for confirmation of the efficacy. miRNA mimics were transfected and VEGF production was quantified. In vivo analyses, KOA was induced by anterior cruciate ligament transection and medial meniscectomy (ACLT model). Wistar rats were randomly allocated to 5 groups in 2 cohorts (n = 5 per group per cohort): normal (no ACLT), ACLT + negative control miRNA (NC), ACLT + miR-126-3p, ACLT + miR-140-5p, and ACLT + a combination of miR-126-3p and miR-140-5p (miR-Mix). miRNA mimics were injected intra-articularly. Hindlimb weight-bearing was assessed using incapacitance tester. Synovitis and cartilage degeneration were evaluated histologically. VEGF levels in synovial fluid, synovium and cartilage were quantified by Simple Western analysis. Non-parametric tests and repeated-measures analyses were performed, with p < 0.05 considered statistically significant. Results Combination of miR-126-3p and miR-140-5p suppressed VEGF production in HS-SY-II cells than either miRNA alone and the suppressive activity on VEGF production was confirmed in primary synovial fibroblasts from KOA patients. In ACLT rats, synovial VEGF levels were increased in NC group compared with normal rats and tended to be lower in all miRNA-treated groups. Hindlimb weight-bearing ratios were reduced to about 30% after ACLT and remained low in the NC group, whereas they gradually improved in the miR-126-3p and miR-140-5p monotherapy groups and almost recovered in the miR-Mix group. At final time point, weight-bearing ratio was significantly higher in miR-Mix group than NC group. Histologically, Krenn scores were tend to lower in miR-126-3p and miR-Mix groups than NC group, indicating amelioration of synovitis, whereas OARSI histopathology scores for femoral cartilage did not differ significantly among groups and tended to be higher in miR-treated groups. There was a strong negative correlation between Krenn synovitis score and hindlimb weight-bearing ratio (Spearman's ρ = −0.7, p < 0.001). Conclusion Intra-articular administration of VEGF-suppressive miR-Mix ameliorated synovitis and pain-related behaviour. In highly unstable traumatic model, however, structural protection of articular cartilage was not observed and cartilage degeneration even tended to be worse in miR-treated groups, possibly due to increased weight-bearing following pain relief. The translational potential of this article These findings suggest intra-articular delivery of VEGF-suppresive miRNAs may represent novel analgesic strategies for KOA by reducing synovitis within joint. miRNA-based modulation of VEGF production could potentially be translated into future disease-modifying and analgesic treatments, however further studies using non-traumatic KOA models, safety evaluation and clarifying molecular mechanisms are required.