Delaying osteoarthritis progression through chondrocyte-targeted delivery of WIKI4 using chondrocyte-derived exosomes

Background & Aim Osteoarthritis (OA) is a troublesome disorder that results in the progressive breakdown of the cartilage extracellular matrix. Due to the poor regenerative ability of chondrocytes, OA treatment is difficult. Meanwhile, a recent study showed that tankyrase is a target locus for treating OA, and a selective tankyrase inhibitor, WIKI4, has shown the ability to delay the progression of cartilage degeneration. However, tankyrase inhibitors have serious side effects outside the cartilage, like bone loss. To reduce the side effects, we targeted WIKI4 delivery into cartilage, by loading WIKI4 into exosomes derived from chondrocytes (cExos). Methods, Results & Conclusion The cExos were isolated using sucrose density gradient centrifugation, and they were identified through transmission electron microscopy (TEM), dynamic light scattering (DLS), and western blotting (WB). WIKI4 was loaded, through electroporation, into cExos (WIKI4-cExos), which were tracked through DiI staining. The transfection efficiency into synovial fibroblasts (SFs), chondrocytes, and bone marrow stem cells (BMSCs) were observed, and the OA-related gene expression was measured using WB, qPCR, and ELISA. The effect of WIKI4-cExos on calcification was evaluated based on osteogenic induction and a destabilization of the medial meniscus (DMM) model was used to evaluate the protective effect of WIKI4-cExos. WIKI4-cExos injection commenced the day after surgery and every 7 days subsequently; normal controls underwent sham operation, while DMM models who received normal saline at the same volume as that of the WIKI4-Exos injected models served as the negative controls. cExos without WIKI4 (Con-cExos) also served as controls. The knee joints were obtained 8 weeks post-DMM surgery. Safranine O staining was used for evaluating specimen slices. DiI tracing showed that cExos preferred to transfer into chondrocyte than SFs or BMSCs. WIKI4-cExos significantly increased SOX9, COL-II, and ACAN expression when RUNX2, β-catenin, COL-I, MMP13, and ADAMTS5 expression decreased. During osteogenic induction, WIKI4-cExos significantly decreased chondrocyte calcification without any notable effects on BMSCs. Safranine O staining showed that WIKI4-cExos significantly delayed OA progression, while Con-cExos were not significantly different from normal saline. Cartilage targeting and tankyrase-inhibiting WIKI4-cExos protect cartilage and delay OA progression. This targeting ability also reduced the side effects observed previously outside chondrocytes.