No abstract

Articular cartilage provides ultralow friction to maintain the physiological function of the knee joint, which arises from the hierarchical complex composed of hyaluronic acid, phospholipids, and lubricin, covering the cartilage surface as boundary lubrication layers. Cartilage-lubricating polymers (HA/PA and HA/PM) mimicking this complex have been demonstrated to restore the lubrication of cartilage via hydration lubrication, thus contributing to the treatment of early osteoarthritis (OA) in vivo. Here, biomimetic cartilage-lubricating hydrogels (HPX/PVA) were constructed by blending HA/PA and HA/PM (HPX) with polyvinyl alcohol (PVA) to improve the boundary lubrication and wear properties, so that the obtained hydrogels may offer a solution to the main drawbacks of PVA hydrogels used as cartilage implants. The HPX/PVA hydrogels exhibited good physicochemical and mechanical properties through hydrogen-bonding interactions, and showed lower friction and wear under the boundary lubrication and fluid film lubrication mechanisms, which remained when the hydrogels were rehydrated. Our strategy may provide new insights into exploring cartilage-inspired lubricating hydrogels.

Hydrogels are extensively investigated as biomimetic extracellular matrix (ECM) scaffolds in tissue engineering. The physiological properties of ECM affect cellular behaviors, which is an inspiration for cell‐based therapies. Photocurable hyaluronic acid (HA) hydrogel (AHAMA‐PBA) modified with 3‐aminophenylboronic acid, sodium periodate, and methacrylic anhydride simultaneously is constructed in this study. Chondrocytes are then cultured on the surface of the hydrogels to evaluate the effect of the physicochemical properties of the hydrogels on modulating cellular behaviors. Cell viability assays demonstrate that the hydrogel is non‐toxic to chondrocytes. The existence of phenylboronic acid (PBA) moieties enhances the interaction of chondrocytes and hydrogel, promoting cell adhesion and aggregation through filopodia. RT‐PCR indicates that the gene expression levels of type II collagen, Aggrecan, and Sox9 are significantly up‐regulated in chondrocytes cultured on hydrogels. Moreover, the mechanical properties of the hydrogels have a significant effect on the cell phenotype, with soft gels (≈2 kPa) promoting chondrocytes to exhibit a hyaline phenotype. Overall, PBA‐functionalized HA hydrogel with low stiffness exhibits the best effect on promoting the chondrocyte phenotype, which is a promising biomaterial for cartilage regeneration.

Osteochondral defects threaten the quality of life of patients to a great extent. To simulate gradient changes in osteochondral tissue, a gradient-mixing injection device consisting of a controller and injection pumps is design. Bioactive glass (BG) and gellan gum (GG) are used to prepare thermosensitive injectable gradient hydrogels (B 0.5 G, B 1 G) with an upper critical solution temperature (UCST) range of 37.7-40.2 °C using this device for the first time. The mechanical properties of gradient hydrogels are significantly better than those of pure GG hydrogels. The gradients in the composition, structure, and morphology of gradient hydrogels are confirmed via physicochemical characterization. Cytocompatibility tests show that hydrogels, especially B 0.5 G gradient hydrogels, promote the proliferation of bone marrow mesenchymal stem cells (BMSCs). Most importantly, qRT-PCR shows that the different components in B 0.5 G gradient hydrogels simultaneously induce the osteogenic and chondrogenic differentiation of BMSCs. Experimental injection in porcine osteochondral defects indicates that the B 0.5 G gradient hydrogel seamlessly fills irregular osteochondral defects in a less invasive manner by controlling the temperature to avoid cellular and tissue damage arising from crosslinkers or other conditions. These results show that thermosensitive injectable B 0.5 G gradient hydrogels have the potential for less invasive integrated osteochondral repair.

Cartilage repair is currently an inevitable and significant issue due to the prevalence of cartilage defects or osteoarthritis. However, it remains a big challenge worldwide because of the avascular and aneural nature of cartilage. In this paper, a novel biomimetic pericellular microniche (BPM), inspired by chondron composed of chondrocyte and its surrounding pericellular matrix (PCM), is proposed to offer a promising solution to achieve cartilage repair. BPM, with a diameter ≈64 µm, not only mimicked the structure of the chondron but also mimicked the key components of the PCM by artificially synthesizing brush‐like molecules (HA/PA and HA/PM). Chondrocyte‐laden BPM is constructed successfully through microfluidic and showed excellent injectability. The encapsulated chondrocyte showed high viability in BPM. F‐Actin and H&E reflected that chondrocytes would grow out of BPM and adhere to the BPM surface through the interaction between CD44 and hyaluronic acid. RT‐qPCR and immunofluorescence staining indicated that the gene expression of type II collagen and aggrecan are upregulated significantly in the BPM. Therefore, the construction of BPM provides a promising strategy for cartilage tissue engineering.This article is protected by copyright. All rights reserved