Research Progress on Injectable Microspheres as New Strategies for the Treatment of Osteoarthritis Through Promotion of Cartilage Repair

Microsphere-Composite Hydrogel for Recruiting Stem Cells and Promoting Osteogenic Differentiation

By recruiting stem cells into scaffolds and differentiating them into osteoblasts, stem cells can be mobilized to directly repair bone defects, which avoids a series of disadvantages of exogenous stem cell implantation. In this study, a microsphere-composite hydrogel for the recruitment and osteogenic differentiation of stem cells was constructed. Methacrylic anhydride modified gelatin (GelMA) and heparin (HepMA), as well as nanohydroxyapatite (nHAP), were used to prepare microspheres followed by adsorbing platelet-derived growth factor BB (PDGF-BB) whose loading efficiency was 53.7 ± 2.2%. Then the microspheres were compounded to the GelMA hydrogel encapsulated with simvastatin (SIM) to obtain microsphere-composite hydrogel GHnH-P@GS. GHnH-P@GS hydrogel could slowly release SIM and PDGF-BB, and the extents of release within 7 days were 44.1 ± 2.0% and 32.8 ± 1.1%. The synergistic effect of small molecule drugs and growth factors not only induced the recruitment of rabbit bone marrow-derived mesenchymal stem cells, but also promoted the osteogenic differentiation of stem cells, which was confirmed by experiments of cell migration, alkaline phosphatase, and alizarin red staining. Collectively, the microsphere-composite hydrogel GHnH-P@GS has a certain reference significance for the design of scaffolds for alveolar bone repair and regeneration.

Precise Lubrication and Protection of Cartilage Damage by Targeting Hydrogel Microsphere

Osteoarthritis (OA) is a degenerative bone and joint disease characterized by decreased cartilage lubrication, leading to continuous wear and ultimately irreversible damage. This situation is particularly challenging for early-stage OA, as current bio-lubricants lack precise targeting for small inflammatory lesions. In this work, an antibody-mediated targeting hydrogel microspheres (HMS) is developed to precisely lubricate the local injury site of cartilage and prevent the progression of early OA. Anti-Collagen type I (Anti-Col1) is an antibody that targets cartilage injury sites in early OA stages. It is anchored on a HMS matrix made of Gelatin methacrylate (GelMA) and poly (sulfobetaine methacrylate) (PSBMA) to create targeted HMS (T-G/S HMS). The T-G/S HMS's high hydrophilicity, along with the dynamic interaction between its surficial Anti-Col1 and the Col1 on cartilage injury site, ensures its precise and effective lubrication of early OA lesions. Consequently, injecting T-G/S HMS into rats with early OA significantly slows disease progression and reduces symptoms. In conclusion, the developed injectable targeted lubricating HMS and the precisely targeted lubrication strategy represent a promising, convenient technique for treating OA, particularly for slowing the early-stage OA progression.

Recent advancements in microspheres mediated targeted delivery for therapeutic interventions in osteoarthritis

Osteoarthritis (OA), affecting around 240 million people globally is a major threat. Currently, available drugs only treat the symptoms of OA; they cannot reverse the disease's progression. The delivery of drugs to afflicted joints is challenging because of poor vasculature of articular cartilage results in their less bioavailability and quick elimination from the joints. Recently approved drugs such as KGN and IL-1 receptor antagonists also encounter challenges because of inadequate formulations. Therefore, microspheres could be a potential player for the intervention of OA owing to its excellent physicochemical properties. This review primarily focuses on microspheres of distinct biomaterials acting as cargo for drugs and biologicals via different delivery routes in the effective management of OA. Microspheres can improve the efficacy of therapeutics by targeting strategies at specific body locations. This review also highlights clinical trials conducted in the last few decades.