Effects And Mechanism Of Gefitinib And Lithium On Osteoarthritis Treatment

Part I:The function and mechanism ofintra-articular delivery of gefitinib for osteoarthritis treatmentOsteoarthritis (OA) is the most prevalent joint disease and is a leading cause of physical disability among elderly patients. Currently there are no efficacious drugs that prevent cartilage degeneration and simultaneously stimulate cartilage matrix synthesis in OA joints. As the major pathological feature of OA is the imbalance between the rates of extracellular matrix synthesis and degradation in articular cartilage, signaling pathways that regulate this balance are promising therapeutic targets. In this study, we found that the p-EGFR is up-regulated while autophagy is down-regulated in human osteoarthritis tissues. These phenomena accompanied with the up-regulation of OA marker genes can also be observed in human chondrocyte culture upon stimulation with transforming growth factor-a (TGF-a). The effects of inhibiting EGFR expression were investigated with both small interfering RNA (siRNA) targeting EGFR and a tyrosine kinase inhibitor (TKI), gefitinib, a Food and Drug Administration (FDA)-approved drug for non-small-cell lung cancer. It was shown that inhibition of EGFR signaling significantly increased Col2al and decreased Mmp13gene expression. This involved autophagy related gene5(Atg5), a key gene for the initiation of autophagy. To test the efficacy of intra-articular delivery of gefitinib for OA treatment, gefitinib-loaded chitosan microspheres (CM-gefitinib) were injected into mouse joints once every3days for8weeks after anterior cruciate ligament transection (ACLT) surgery. Histological analyses at8weeks post-surgery revealed much better cartilage homeostasis and less EGFR expression in the CM-gefitinib-treated joints compared to the control group. This is accompanied with significantly increased Col II expression and significantly decreased Mmpl3expression in cartilage tissues, as well as the activation of Beclinl and LC3, which are major markers of autophagy. These findings provide proof of concept that intra-articular delivery of gefitinib can not only block cartilage matrix degradation but also promote collagen II synthesis in osteoarthritic joints through modulation of the EGFR-autophagy axis; thus demonstrating the unique advantage of gefitinib as a small molecule drug for osteoarthritis therapy. Part II:The efficacy and mechanism of Li-MBG scaffolds for osteochondral defect regenerationBecause cartilage and bone tissues have different lineage-specific biological properties, it is challenging to fabricate a single type of scaffold that can biologically fulfill the requirements for regeneration of these two lineages simultaneously within osteochondral defects. To overcome this challenge, we developed a Lithium-containing mesoporous bioactive glass (Li-MBG) scaffold by utilizing a physical/chemical co-template method. The efficacy and mechanism of Li-MBG for regeneration of osteochondral defects were systematically investigated with both in vitro cell culture and in vivo osteoarthritis models. Histological and micro-CT results showed that Li-MBG scaffolds significantly enhanced the regeneration of both subchondral bone and hyaline cartilage-like tissues as compared to pure MBG scaffolds, upon implantation in rabbit osteochondral defects for8and16weeks. Further investigation demonstrated that the released Li+ions from the Li-MBG scaffolds might play a key role in stimulating the regeneration of osteochondral defects. The corresponding mechanistic pathways involve Li+ions enhancing the proliferation and osteogenic differentiation of bone mesenchymal stem cells (BMSCs) through activation of the Wnt/β-catenin signalling pathway; as well as Li+ions protecting chondrocytes and cartilage tissues from the inflammatory osteoarthritis (OA) environment through activation of autophagy. These findings suggest that the incorporation of Li+ions into bioactive MBG scaffolds is a viable strategy for fabricating bi-lineage conducive scaffolds that enhance regeneration of osteochondral defects.