Injured and diseased joint cartilage stands as the leading cause of disability, affecting approxi- mately 33% of the adult population. State-of-the-art treatments of destroyed joint cartilage are seriously limited. Tissue engineering, up to this point, has struggled to regenerate high-quality cartilage, encountering significant challenges such as dedifferentiation, hypertrophy, and degen- eration. BMP4, a potent inducer of chondrogenesis in mesenchymal cells, serves as a cornerstone in our approach. Additionally, we harness the power of hypoxia and its pivotal transcription factor, HIF1, responsible for cellular adaptation to hypoxic conditions, to foster chondrogenesis and curtail hypertrophic terminal differentiation and degeneration in vitro. Hypoxia stabilizes both HIF1 and HIF2, and current hypoxia mimetics, such as Roxadustat, act as HIF stabilizers.
Within the framework of this thesis, we embarked on the exploration of a hypothesis positing that the sustained collaboration of BMP4 and HIF signaling serves as a driving force for robust chondrogenic differentiation in mesenchymal stem cells. This combined action simultaneously serves as a potent countermeasure against chondrocyte hypertrophy and degeneration. To repli- cate a physiologically relevant context, we adopted a micromass culture as our in vitro model, closely mimicking the mechanical microenvironment observed in vivo. Our investigation in- volved assessing the impact of Roxadustat and BMP4 on critical markers including Collagen I, II, X, and Sox 9, shedding light on their roles in stimulating chondrogenesis while effectively curbing hypertrophy in cartilage derived from embryonic limb mesenchymal stem cells.
Our ongoing efforts in this project are geared towards addressing the formidable challenges presented by cartilage injuries, often characterized by irregular shapes. To facilitate ease of filling and minimally invasive procedures, our team has already devised an innovative approach. This entails the creation of biodegradable nanofibrous hollow microspheres through the self-assembly of a star-shaped poly(L-lactic acid), serving as a groundbreaking injectable carrier for chondro- cytes. These microspheres, once injected in an animal model, will enable the sustained release of BMP4 and Roxadustat, building upon the valuable insights gained from the experiments con- ducted in this thesis
