Articular cartilage (AC), which covers the ends of bones in joints, particularly the knee joints, provides a robust interface to maintain frictionless movement during daily life due to its remarkable lubricating and load-bearing capacities. However, osteoarthritis (OA), characterized by the progressive degradation of AC, compromises the properties of AC and thus leads to frayed and rough interfaces between the bones, which subsequently accelerates the progression of OA. Hydrogels, composed of highly hydrated and interconnected polymer chains, are potential candidates for AC replacement due to their physical and chemical properties being similar to those of AC. In this review, we summarize the recent progress of hydrogel-based synthetic cartilage, or cartilage-like hydrogels, with a particular focus on their lubrication and load-bearing properties. The different formulations, current limitations, and challenges of such hydrogels are also discussed. Moreover, we discuss the future directions of hydrogel-based synthetic cartilage to repair and even regenerate the damaged AC.

Nerve injuries and lesions often lead to the loss of neural control, reducing the patients’ quality of life. Nerve self-repair is difficult due to the low regeneration capacity, insufficient secretion of neurotrophic factors, secondary complications, and adverse microenvironmental conditions such as severe hypoxia-ischemia, inflammation, and oxidative stress. Effective therapies that can accelerate nerve regeneration have been explored. Cytokine therapy can significantly improve neural survival and myelin regeneration during nerve repair. Insulin-like growth factor-1 (IGF-1) and its isoforms (IGF-1Ea and IGF-1Eb/Ec [also known as MGF]) represent a promising therapeutic approach regarding nerve repair, given their well-described proliferative and anti-apoptotic capacities on neurons withstanding the adverse environmental conditions. This review summarizes the research progress regarding the effects of IGF-1 and its isoforms on nerve repair after nerve injury, hypoxic-ischemic insult, inflammation, and oxidative stress. We provide a theoretical basis for the clinical treatment of nerve injuries.