Advancements in hydrogel design for articular cartilage regeneration: A comprehensive review

Multifunctional piezoelectric hydrogels under ultrasound stimulation boost chondrogenesis by recruiting autologous stem cells and activating the Ca2+/CaM/CaN signaling pathway

Articular cartilage, owing to the lack of undifferentiated stem cells after injury, faces significant challenges in reconstruction and repair, making it a major clinical challenge. Therefore, there is an urgent need to design a multifunctional hydrogels capable of recruiting autologous stem cells to achieve in situ cartilage regeneration. Here, our study investigated the potential of a piezoelectric hydrogel (Hyd6) for enhancing cartilage regeneration through ultrasound (US) stimulation. Hyd6 has multiple properties including injectability, self-healing capabilities, and piezoelectric characteristics. These properties synergistically promote stem cell chondrogenesis. The fabrication and characterization of Hyd6 revealed its excellent biocompatibility, biodegradability, and electromechanical conversion capabilities. In vitro and in vivo experiments revealed that Hyd6, when combined with US stimulation, significantly promotes the recruitment of autologous stem cells and enhances chondrogenesis by generating electrical signals that promote the influx of Ca2+, activating downstream CaM/CaN signaling pathways and accelerating cartilage formation. An in vivo study in a rabbit model of chondral defects revealed that Hyd6 combined with US treatment significantly improved cartilage regeneration, as evidenced by better integration of the regenerated tissue with the surrounding cartilage, greater collagen type II expression, and improved mechanical properties. The results highlight the potential of Hyd6 as a novel therapeutic approach for treating cartilage injuries, offering a self-powered, noninvasive, and effective strategy for tissue engineering and regenerative medicine.

Current Status and Perspectives of Research on Polymer Hydrogels in the Treatment and Protection of Osteoarthritis

Arthritis is a degenerative disease characterized by chronic cartilage degeneration. It affects hundreds of millions of people worldwide and often has serious consequences such as joint pain and swelling, limited mobility, and joint deformity. However, conventional treatments still struggle to achieve satisfactory results. Finding more effective treatments for arthritis remains an important clinical challenge. As hydrogels have a unique 3D spatial mesh structure, significant material interaction ability, adjustable mechanical properties, and good biodegradability, they can provide a suitable cellular or tissue microenvironment, and their potential in scaffolding effect, lubrication, anti-inflammatory effect, or drug or cellular delivery is expected to be a potent therapeutic approach for the treatment of osteoarthritis. In this review, three aspects of hydrogel products for osteoarthritis treatment are comprehensively summarized and discussed, namely, material selection and gel design, exploration of cross-linking mechanisms, and mechanisms of hydrogel therapy for osteoarthritis, and focus on the advantages and limitations of their clinical applications, which point out the direction of the development strategy of innovative products in this field, applied research, and clinical transformation.

Molecular Mechanisms and Therapeutic Role of Intra-Articular Hyaluronic Acid in Osteoarthritis: A Precision Medicine Perspective

Background: Osteoarthritis (OA) is a degenerative joint disease characterized by progressive cartilage breakdown, synovial inflammation, and pain, which leads to significant disability. IAHA is widely used because of its viscoelastic properties, which restore synovial fluid homeostasis and reduce symptoms. However, emerging evidence suggests that IAHA exerts additional biological effects including chondroprotection, inflammatory modulation, oxidative stress reduction, and pain modulation, which may influence disease progression. Objective: This narrative review examines the biological mechanisms underlying IAHA's role in OA management. The review explored IAHA's effects on synovial fluid viscoelasticity, inflammatory cytokine modulation, cartilage preservation, oxidative stress regulation, and pain pathways, emphasizing the influence of molecular weight variations on therapeutic efficacy. Additionally, this review evaluates IAHA's integration into multimodal treatment strategies, its potential disease-modifying effects, and future directions for personalized treatment approaches. Methods: A comprehensive literature review was conducted using PubMed, Cochrane Library, EMBASE, Scopus, and Web of Science for studies published between January 2000 and March 2024. The search focused on IAHA's molecular, cellular, and biochemical effects in OA and clinical findings assessing its impact on joint function, pain relief, and disease progression. Results: IAHA improves synovial fluid lubrication, reduces proinflammatory cytokines (IL-1β, TNF-α), inhibits matrix metalloproteinases (MMPs), scavenges reactive oxygen species (ROS), and modulates nociceptive pathways. High-molecular-weight IAHA demonstrates superior efficacy in advanced OA, while low-molecular-weight formulations may be better suited for early-stage disease. Although IAHA's symptom relief is comparable to corticosteroids and NSAIDs, its favorable safety profile and emerging disease-modifying potential support its long-term use in OA management. Conclusions: IAHA represents a multifaceted therapeutic approach bridging symptomatic relief and regenerative strategies. While long-term efficacy, optimal administration protocols, and patient-specific responses remain subjects of ongoing research, refining treatment selection criteria, dosing regimens, and combination strategies may enhance clinical outcomes. Future studies should explore biomarker-driven approaches, standardize treatment protocols, and assess IAHA's synergy with regenerative medicine to optimize its role in OA management.