Biomimetic cartilage-lubricating polymers regenerate cartilage in rats with early osteoarthritis

Gelatin microcarriers as an effective adipose-derived stem cells delivery strategy in osteoarthritis treatment

Despite their clinical success, stem cells (SCs) in the treatment of osteoarthritis (OA) are limited by lower retention efficiency and restricted paracrine function. The development of effective SCs culture and delivery systems to maintain or promote SCs paracrine function is urgently needed. In this study, we focused on gelatin microcarriers with different sizes as SCs culture scaffold for OA therapy. The effect of culturing adipose-derived stem cells (ADSCs) on different size microcarriers (180 μm and 320 μm) to promote paracrine function was evaluated. The secretome of ADSCs cultured on microcarriers more effectively regulated macrophages and chondrocytes in a direction favorable to OA healing compared to culture plates. In particular, microcarriers with ADSCs effectively reduced the coefficient of friction at the cartilage interface. Injection low-dose ADSCs without and with different size microcarriers into the knee joints in rats' OA model was achieved. Even better OA therapeutic effects were achieved by using smaller size (higher curvature) microcarriers to deliver ADSCs at low doses. Microcarrier-based cell delivery strategies offer potential solution method for OA therapy.

Zwitterionic Poly-Carboxybetaine Polymers Restore Lubrication of Inflamed Articular Cartilage

Osteoarthritis is a degenerative joint disease that is associated with decreased synovial fluid viscosity and increased cartilage friction. Though viscosupplements are available for decades, their clinical efficacy is limited and there is ample need for more effective joint lubricants. This study first evaluates the tribological and biochemical properties of bovine articular cartilage explants after stimulation with the inflammatory cytokine interleukin-1β. This model is then used to investigate the tribological potential of carboxybetaine (CBAA)-based zwitterionic polymers of linear and bottlebrush architecture. Due to their affinity for cartilage tissue, these polymers form a highly hydrated surface layer that decreases friction under high load in the boundary lubrication regime. For linear pCBAA, these benefits are retained over several weeks and the relaxation time of cartilage explants under compression is furthermore decreased, thereby potentially boosting the weeping lubrication mechanism. Bottlebrush bb-pCBAA shows smaller benefits under boundary lubrication but is more viscous than linear pCBAA, therefore providing better lubrication under low load in the fluid-film regime and enabling a longer residence time to bind to the cartilage surface. Showing how CBAA-based polymers restore the lost lubrication mechanisms during inflammation can inspire the next steps toward more effective joint lubricants in the future.

A Core-Brush Nanoplatform with Enhanced Lubrication and Anti-Inflammatory Properties for Osteoarthritis Treatment

Osteoarthritis (OA) is recognized as a highly friction-related joint disease primarily associated with increased joint friction and inflammation due to pro-inflammatory M1-type macrophage infiltration in the articular cavity. Therefore, strategies to simultaneously increase lubrication and relieve inflammation to remodel the damaged articular microenvironment are of great significance for enhancing its treatment. Herein, a multifunctional core-brush nanoplatform composed of a ROS-scavenging polydopamine-coated SiO2 core and lubrication-enhancing zwitterionic poly(2-methacryloyloxyethyl phosphorylcholine) (PMPC) brush and loaded with the anti-inflammatory drug curcumin by a reactive oxygen species (ROS)-liable conjugation (named as SiO2@PP-Cur) is rationally designed. Benefiting from the grafted zwitterionic PMPC brush, a tenacious hydration layer with enhanced lubricity for reducing joint abrasions is developed. More importantly, based on the mono-iodoacetic acid-induced arthritis (MIA) rat model, intra-articular injection of SiO2@PP-Cur nanoplatform can effectively alleviate articular inflammation via promoting macrophage polarization from the pro-inflammatory M1 to anti-inflammatory M2 state by activating the nuclear factor erythroid 2-related factor 2 (Nrf2) signaling pathway and attenuating the degradation of cartilage matrix, resulting in the remodeling of the damaged microenvironment into a pro-regenerative microenvironment. As a result, SiO2@PP-Cur can considerably inhibit OA progression. Therefore, the work may provide a novel strategy for the development of an advanced core-brush nanoplatform for enhanced OA therapy.

Advances in Injectable Polymeric Biomaterials and Their Contemporary Medical Practices

Injectable biomaterials have been engineered to operate within the human body, offering versatile solutions for minimally invasive therapies and meeting several stringent requirements such as biocompatibility, biodegradability, low viscosity for ease of injection, mechanical strength, rapid gelation postinjection, controlled release of therapeutic agents, hydrophobicity/hydrophilicity balance, stability under physiological conditions, and the ability to be sterilized. Their adaptability and performance in diverse clinical settings make them invaluable for modern medical treatments. This article reviews recent advancements in the design, synthesis, and characterization of injectable polymeric biomaterials, providing insights into their emerging applications. We discuss a broad spectrum of these materials, including natural, synthetic, hybrid, and composite types, that are being applied in targeted drug delivery, cell and protein transport, regenerative medicine, tissue adhesives, injectable implants, bioimaging, diagnostics, and 3D bioprinting. Ultimately, the review highlights the critical role of injectable polymeric biomaterials in shaping the future of medical treatments and improving patient outcomes across a wide range of therapeutic and diagnostic applications.

Dose-effect relationship of copolymer on enhancing aqueous lubrication of a hybrid osteoarthritis drug delivery nanocarrier

Developing stimulus-responsive properties of drug delivery nanocarriers combined with enhanced joint lubrication is an effective synergistic strategy for treating osteoarthritis. Poly(N-isopropylacrylamide) (PNIPAm) is a typical thermo-responsive polymer, which can achieve drug delivery by transition from swollen state to collapsed state. However, undesired transition temperature, limited drug loading capacity, and weakened mechanical properties in joint present obstacles to use as drug delivery nanocarriers. In this work, we demonstrate dose-effect relationship between the PNIPAm-based copolymer and nanoscale metal-organic frameworks on enhancing both aqueous lubrication and drug delivery performance of a hybrid osteoarthritis (OA) nanocarrier. A series of NIPAm and poly(ethylene glycol)methacrylate (PEGMa) copolymer microgels with different feeding content are optimized to grow on the surface of MIL-101(Cr) nanoparticles via one-pot soap-free emulsion copolymerization method. By changing the feeding mass ratio of NIPAm and PEGMa, MIL-101(Cr)@P(NIPAm-g-PEGMax) (x = 0, 1, 2, 3, and 4, named MPNPx) hybrids can ameliorate the lower critical solution temperature to match with OA and enhance the aqueous lubrication performance. Among the as-synthesized hybrids, MPNP3 hybrids manifested the notable enhanced thermo-responsive tribological performance due to the synergistic effect of "hydration lubrication" and "ball-bearing" function of the optimized copolymer microgel layer on the surface of metal-organic frameworks (MOFs). Anti-inflammatory drug loading is enabled by the high surface area and porosity of the MOFs, and the MPNP3 drug delivery nanocarriers achieve thermo-responsive release in vitro. Our work establishes the dose-effect relationship between thermo-responsive NIPAm and hydrophilic PEGMa of the copolymer grown on the surface of MOFs, providing valuable insights for improving the versatility of stimuli-responsive for biomedical application.

Inspired by lubricin: a tailored cartilage-armor with durable lubricity and autophagy-activated antioxidation for targeted therapy of osteoarthritis

Osteoarthritis (OA), which disables articular cartilage, affects millions of people. The self-healing capacity is inhibited by internal oxidative stress and external lubrication deficiency and enzymatic degradation. To overcome these challenges, a tailored cartilage-armor is designed to ameliorate the inflamed cartilage, which is implemented by a novel collagen type II (Col II)-binding peptide conjugated zwitterionic polymer (PSB-b-PColBP, PSP). By mimicking natural lubricin, PSP specifically targets the cartilage surface and forms an in situ hydration armor. This engineered cartilage-armor can prevent enzymatic cartilage degradation (nearly 100% resistance to catabolic enzymes) and provide durable lubrication properties (COF < 0.013 for 500 cycles). An autophagy-activation process, absent in previous biomimetic lubricants, enhances the enzymatic activity of the tailored cartilage-armor, offering effective anti-oxidant properties to suppress oxidative stress. By inhibiting the PI3K-Akt/NF-κB signaling pathway, chondrocytes protected by the tailored armor can secrete a cartilage matrix even in inflammatory microenvironments. In OA rat models, osteophyte formation and the inflammatory response have been inhibited by the cartilage-armor, demonstrating a therapeutic effect comparable to most drug-loaded systems. This study underscores the potential of tailoring cartilage-armor with the cartilage targeting and autophagy-activating properties in integrating offensive-defensive mechanisms for cartilage remodeling. This represents an alternative strategy for clinical OA therapy.

Enzyme-responsive microgel with controlled drug release, lubrication and adhesion capability for osteoarthritis attenuation

The treatment of osteoarthritis (OA) remains challenging due to the narrow therapeutic window and rapid clearance of therapeutic agents, even with intra-articular administration, resulting in a low treatment index. Recent advancements in local drug delivery systems have yet to overcome the issues of uncontrolled burst release and short retention time, leading to suboptimal OA treatment outcome. Herein, we developed a methacrylate-crosslinking hyaluronic acid (HA) microgel (abbreviated as CXB-HA-CBP) that covalently conjugates the anti-inflammatory drug celecoxib (CXB) via a metalloproteinase-2 (MMP-2)-responsive peptide linker (GGPLGLAGGC) and a collagen II binding peptide (WYRGRLC). The GGPLGLAGGC linker is specifically cleaved by the overexpressed MMP-2 enzyme within the OA joint, enabling the sustained and on-demand release of CXB entity. The synergistic action of CXB and HA effectively inhibited macrophage activation and reduced the production of pro-inflammatory cytokines, protecting chondrocytes from damage. Furthermore, the collagen II peptide introduced on the microgel surface enabled a cartilage-binding function to form an artificial lubrication microgel layer on the cartilage surface to reduce cartilage wear. The CXB-HA-CBP microgel showed an extended retention time of up to 18 days in the affected joint, leading to an effective OA treatment in rats. This sophistically designed microgel, characterized by the prolonged retention time, sustained drug delivery, and enhanced lubrication, presents a promising biomedicine for OA treatment. STATEMENT OF SIGNIFICANCE: A new methacrylate-crosslinking hyaluronic acid (HA) microgel, covalently conjugated with the celecoxib (CXB)-GGPLGLAGGC and the collagen II binding peptide (CBP, peptide sequence: WYRGRLC), was developed. The overexpressed MMP-2 in OA joint cleaved the GGPLGLAGGC linker to trigger the CXB moiety release. Besides, the CBP on the surface of microgels enabled a cartilage-attaching ability, resulting in a prolonged retention time and an improved lubrication property in joint. This advanced drug-loading microgel remarkably reduced macrophage activation and pro-inflammation cytokine production, while protecting the chondrocytes via a dual action of CXB and HA. This study demonstrated that the enzyme-responsive drug-loading microgel could serve as an platform to efficiently attenuate osteoarthritis.

Zwitterionic Granular Hydrogel for Cartilage Tissue Engineering

Zwitterionic hydrogels have high potential for cartilage tissue engineering due to their ultra-hydrophilicity, nonimmunogenicity, and superior antifouling properties. However, their application in this field has been limited so far, due to the lack of injectable zwitterionic hydrogels that allow for encapsulation of cells in a biocompatible manner. Herein, a novel strategy is developed to engineer cartilage employing zwitterionic granular hydrogels that are injectable, self-healing, in situ crosslinkable and allow for direct encapsulation of cells with biocompatibility. The granular hydrogel is produced by mechanical fragmentation of bulk photocrosslinked hydrogels made of zwitterionic carboxybetaine acrylamide (CBAA), or a mixture of CBAA and zwitterionic sulfobetaine methacrylate (SBMA). The produced microgels are enzymatically crosslinkable using horseradish peroxidase, to quickly stabilize the construct, resulting in a microporous hydrogel. Encapsulated human primary chondrocytes are highly viable and able to proliferate, migrate, and produce cartilaginous extracellular matrix (ECM) in the zwitterionic granular hydrogel. It is also shown that by increasing hydrogel porosity and incorporation of SBMA, cell proliferation and ECM secretion are further improved. This strategy is a simple and scalable method, which has high potential for expanding the versatility and application of zwitterionic hydrogels for diverse tissue engineering applications.

Functional hyaluronic acid microneedles for skin photoaging based on collagen induction and oxidative stress regulation strategies

Photoaging holds remarkable importance for skin health and senescence. Ultraviolet (UV) irradiation results in the disruption of the extracellular matrix (ECM) microenvironment, the degradation of collagen, and the generation of oxidative stress. Traditional hyaluronic acid (HA) exhibits a diminished capacity to stimulate collagen regeneration, and hampered by its poor permeability as a macromolecule, ultimately resulting in constrained therapeutic outcomes for the treatment of photoaging. In this study, HA/PX was prepared by functional modification of HA with sulfonate-rich or phosphatidylcholine-rich polymers, which could complement the loss of ECM and ameliorate the senescence of human fibroblasts (HDFs) and hairless mouse models subjected to UVB-induced photoaging. The results indicate that HA/PX exhibits superior abilities in delaying cellular aging, promoting collagen regeneration, and resisting reactive oxygen species (ROS) compared to HA. Furthermore, HA/PX shows good biocompatibility both in vivo and in vitro, without causing allergic reactions or other adverse effects. We also demonstrated that the transdermal delivery of HA/PX via microneedle arrays (MNs) can significantly mitigate wrinkles and skin damage in photoaged nude mice, and achieve the treatment of skin photoaging by enhancing epidermal thickness, promoting collagen deposition, and reducing oxidative stress. Therefore, our research offers a novel possibility for future anti-aging therapeutic strategies.

Extracellular Matrix-Surrogate Advanced Functional Composite Biomaterials for Tissue Repair and Regeneration

Native tissues, comprising multiple cell types and extracellular matrix components, are inherently composites. Mimicking the intricate structure, functionality, and dynamic properties of native composite tissues represents a significant frontier in biomaterials science and tissue engineering research. Biomimetic composite biomaterials combine the benefits of different components, such as polymers, ceramics, metals, and biomolecules, to create tissue-template materials that closely simulate the structure and functionality of native tissues. While the design of composite biomaterials and their in vitro testing are frequently reviewed, there is a considerable gap in whole animal studies that provides insight into the progress toward clinical translation. Herein, we provide an insightful critical review of advanced composite biomaterials applicable in several tissues. The incorporation of bioactive cues and signaling molecules into composite biomaterials to mimic the native microenvironment is discussed. Strategies for the spatiotemporal release of growth factors, cytokines, and extracellular matrix proteins are elucidated, highlighting their role in guiding cellular behavior, promoting tissue regeneration, and modulating immune responses. Advanced composite biomaterials design challenges, such as achieving optimal mechanical properties, improving long-term stability, and integrating multifunctionality into composite biomaterials and future directions, are discussed. We believe that this manuscript provides the reader with a timely perspective on composite biomaterials.

Lubricin-Inspired Nanozymes Reconstruct Cartilage Lubrication System with an "In-Out" Strategy

Lubricin, secreted primarily by chondrocytes, plays a critical role in maintaining the function of the cartilage lubrication system. However, both external factors such as friction and internal factors like oxidative stress can disrupt this system, leading to osteoarthritis. Inspired by lubricin, a lubricating nanozyme, that is, Poly-2-acrylamide-2-methylpropanesulfonic acid sodium salt-grafted aminofullerene, is developed to restore the cartilage lubrication system using an "In-Out" strategy. The "Out" aspect involves reducing friction through a combination of hydration lubrication and ball-bearing lubrication. Simultaneously, the "In" aspect aims to mitigate oxidative stress by reducing free radical, increasing autophagy, and improving the mitochondrial respiratory chain. This results in reduced chondrocyte senescence and increased lubricin production, enhancing the natural lubrication ability of cartilage. Transcriptome sequencing and Western blot results demonstrate that it enhances the functionality of mitochondrial respiratory chain complexes I, III, and V, thereby improving mitochondrial function in chondrocytes. In vitro and in vivo experiments show that the lubricating nanozymes reduce cartilage wear, improve chondrocyte senescence, and mitigate oxidative stress damage, thereby mitigating the progression of osteoarthritis. These findings provide novel insights into treating diseases associated with oxidative stress and frictional damage, such as osteoarthritis, and set the stage for future research and development of therapeutic interventions.

Lubricant Strategies in Osteoarthritis Treatment: Transitioning from Natural Lubricants to Drug Delivery Particles with Lubricant Properties

Osteoarthritis (OA) is a debilitating joint disease characterized by cartilage degradation, leading to pain and functional impairment. A key contributor to OA progression is the decline in cartilage lubrication. In physiological conditions, synovial fluid (SF) macromolecules like hyaluronic acid (HA), phospholipids, and lubricin play a crucial role in the boundary lubrication of articular cartilage. In early OA, cartilage damage triggers inflammation, altering SF composition and compromising the lubrication layer. This increases friction between mating interfaces, worsening cartilage degradation and local inflammation. Therefore, early-stage restoration of lubrication (by injecting in the joint different classes of compounds and formulations) could alleviate, and potentially reverse, OA progression. In the light of this, a broad variety of lubricants have been investigated for their ability to reduce friction in OA joints and promote cartilage repair in clinical and preclinical studies. This review examines recent advancements in lubricant-based therapy for OA, focusing on natural, bioinspired, and alternative products. Starting from the currently applied therapy, mainly based on natural lubricants as HA, we will present their modified versions, either in hydrogel form or with specific biomimetic moieties with the aim of reducing their clearance from the joint and of enhancing their lubricating properties. Finally, the most advanced and recent formulation, represented by alternative strategies, will be proposed. Particular emphasis will be placed on those ones involving new types of hydrogels, microparticles, nanoparticles, and liposomes, which are currently under investigation in preclinical studies. The potential application of particles and liposomes could foster the transition from natural lubricants to Drug Delivery Systems (DDSs) with lubricant features; transition which could provide more complete OA treatments, by simultaneously providing lubrication replacement and sustained release of different payloads and active agents directly at the joint level. Within each category, we will examine relevant preclinical studies, highlighting challenges and future prospects.

Cell volume regulation modulates macrophage-related inflammatory responses via JAK/STAT signaling pathways

Cell volume as a characteristic of changes in response to external environmental cues has been shown to control the fate of stem cells. However, its influence on macrophage behavior and macrophage-mediated inflammatory responses have rarely been explored. Herein, through mediating the volume of macrophages by adding polyethylene glycol (PEG), we demonstrated the feasibility of fine-tuning cell volume to regulate macrophage polarization towards anti-inflammatory phenotypes, thereby enabling to reverse macrophage-mediated inflammation response. Specifically, lower the volume of primary macrophages can induce both resting macrophages (M0) and stimulated pro-inflammatory macrophages (M1) to up-regulate the expression of anti-inflammatory factors and down-regulate pro-inflammatory factors. Further mechanistic investigation revealed that macrophage polarization resulting from changing cell volume might be mediated by JAK/STAT signaling pathway evidenced by the transcription sequencing analysis. We further propose to apply this strategy for the treatment of arthritis via direct introduction of PEG into the joint cavity to modulate synovial macrophage-related inflammation. Our preliminary results verified the credibility and effectiveness of this treatment evidenced by the significant inhibition of cartilage destruction and synovitis at early stage. In general, our results suggest that cell volume can be a biophysical regulatory factor to control macrophage polarization and potentially medicate inflammatory response, thereby providing a potential facile and effective therapy for modulating macrophage mediated inflammatory responses. STATEMENT OF SIGNIFICANCE: Cell volume has recently been recognized as a significantly important biophysical signal in regulating cellular functionalities and even steering cell fate. Herein, through mediating the volume of macrophages by adding polyethylene glycol (PEG), we demonstrated the feasibility of fine-tuning cell volume to induce M1 pro-inflammatory macrophages to polarize towards anti-inflammatory M2 phenotype, and this immunomodulatory effect may be mediated by the JAK/STAT signaling pathway. We also proposed the feasible applications of this PEG-induced volume regulation approach towards the treatment of osteoarthritis (OA), wherein our preliminary results implied an effective alleviation of early synovitis. Our study on macrophage polarization mediated by cell volume may open up new pathways for immune regulation through microenvironmental biophysical clues.

Grafting of cationic molecules to hyaluronic acid improves adsorption and cartilage lubrication

Synovial fluid lubricates articular joints by forming a hydrated layer between the cartilage surfaces. In degenerative joint diseases like osteoarthritis (OA), the synovial fluid is compromised, which leads to less effective innate lubrication and exacerbated cartilage degeneration. Studies over the years have led to the development of partially or fully synthetic biolubricants to reduce the coefficient of friction with cartilage in knee joints. Cartilage-adhering, hydrated lubricants are particularly important to provide cartilage lubrication and chondroprotection under high normal load and slow speed. Here, we report the development of a hyaluronic acid (HA)-based lubricant functionalized with cationic branched poly-L-lysine (BPL) molecules that bind to cartilage via electrostatic interactions. We surmised that the electrostatic interactions between the BPL-modified HA molecules (HA-BPL) and the cartilage facilitate localization of the HA molecules to the cartilage surface. The number of BPL molecules on the HA backbone was varied to determine the optimal grafting density for cartilage binding and HA localization. Collectively, our results show that our HA-BPL molecules adhered readily to cartilage and were effective as a lubricant in cartilage-on-cartilage shear measurements where the modified HA molecules significantly reduce the coefficient of friction compared to phosphate-buffered saline or HA alone. This proof-of-concept study shows how the incorporation of cartilage adhering moieties, such as cationic molecules, can be used to enhance cartilage binding and lubrication properties of HA.

Self-Reinforced MOF-Based Nanogel Alleviates Osteoarthritis by Long-Acting Drug Release

Intra-articular injection of drugs is an effective strategy for osteoarthritis (OA) treatment. However, the complex microenvironment and limited joint space result in rapid clearance of drugs. Herein, a nanogel-based strategy is proposed for prolonged drug delivery and microenvironment remodeling. Nanogel is constructed through the functionalization of hyaluronic acid (HA) by amide reaction on the surface of Kartogenin (KGN)-loaded zeolitic imidazolate framework-8 (denoted as KZIF@HA). Leveraging the inherent hydrophilicity of HA, KZIF@HA spontaneously forms nanogels, ensuring extended drug release in the OA microenvironment. KZIF@HA exhibits sustained drug release over one month, with low leakage risk from the joint cavity compared to KZIF, enhanced cartilage penetration, and reparative effects on chondrocytes. Notably, KGN released from KZIF@HA serves to promote extracellular matrix (ECM) secretion for hyaline cartilage regeneration. Zn2+ release reverses OA progression by promoting M2 macrophage polarization to establish an anti-inflammatory microenvironment. Ultimately, KZIF@HA facilitates cartilage regeneration and OA alleviation within three months. Transcriptome sequencing validates that KZIF@HA stimulates the polarization of M2 macrophages and secretes IL-10 to inhibit the JNK and ERK pathways, promoting chondrocytes recovery and enhancing ECM remodeling. This pioneering nanogel system offers new therapeutic opportunities for sustained drug release, presenting a significant stride in OA treatment strategies.

Mesenchymal stem cells derived from human adipose tissue exhibit significantly higher chondrogenic differentiation potential compared to those from rats

BACKGROUND

Osteoarthritis is a prevalent joint disease affecting both humans and animals. It is characterized by articular cartilage degeneration and joint surface eburnation. Currently, no effective pharmacological treatment is available to restore the original function and structure of defective cartilage.

OBJECTIVE

This study explores the potential of stem cell-based therapy in treating joint diseases involving cartilage degeneration, offering a promising avenue for future research and treatment. The primary aim was to compare the characteristics and, more importantly, the chondrogenic differentiation potential of human and rat adipose-derived mesenchymal stem cells (AD-MSCs).

METHODS

Rat adipose tissue was collected from Sprague Dawley rats, while human adipose tissue was obtained in the form of lipoaspirate. The mesenchymal stem cells (MSCs) were then harvested using collagenase enzyme and subcultured. We meticulously evaluated and compared the cell morphology, percentage of cell viability, population doubling time, metabolic proliferation, and chondrogenic differentiation potential of MSCs harvested from both sources. Chondrogenic differentiation was induced at passage 3 using the 3D pellet culture method and assessed through histological and molecular analysis.

RESULTS

The findings revealed that human and rat AD-MSCs were phenotypically identical, and an insignificant difference was found in cell morphology, percentage of cell viability, metabolic proliferation, and population doubling time. However, the chondrogenic differentiation potential of human AD-MSCs was evaluated as significantly higher than that of rat AD-MSCs.

CONCLUSION

The current study suggests that research regarding chondrogenic differentiation of rat AD-MSCs can be effectively translated to humans. This discovery is a significant contribution to the field of regenerative medicine and has the potential to advance our understanding of stem cell-based therapy for joint diseases.

Composite Hydrogel Containing Collagen-Modified Polylactic Acid-Hydroxylactic Acid Copolymer Microspheres Loaded with Tetramethylpyrazine Promotes Articular Cartilage Repair

Articular cartilage defects pose a significant challenge due to the limited self-healing ability of cartilage. However, traditional techniques face limitations including autologous chondrocyte expansion issues. This study aims to investigate the effects of the polylactic acid-glycolic acid (PLGA) and collagen-surface modified polylactic acid-glycolic acid (CPLGA) microspheres loaded with tetramethylpyrazine (TMP) on two cell types and the regeneration potential of articular cartilage. CPLGA microspheres are prepared by Steglich reaction and characterized. They evaluated the effect of TMP-loaded microspheres on HUVECs (Human Umbilical Vein Endothelial Cells) and examined the compatibility of blank microspheres with BMSCs (Bone marrow mesenchymal stromal cells) and their potential to promote cartilage differentiation. Subcutaneous implant immune tests and cartilage defect treatment are conducted to assess biocompatibility and cartilage repair potential. The results highlight the efficacy of CPLGA microspheres in promoting tissue regeneration, attributed to improved hydrophilicity and collagen-induced mitigation of degradation. Under hypoxic conditions, both CPLGA and PLGA TMP-loaded microspheres exhibit inhibitory effects on HUVEC proliferation, migration, and angiogenesis. Notably, CPLGA microspheres show enhanced compatibility with BMSCs, facilitating chondrogenic differentiation. Moreover, the CPLGA microsphere-composite hydrogel exhibits potential for cartilage repair by modulating angiogenesis and promoting BMSC differentiation.

Natural product of angelica essential oil developed as a stable Pickering emulsion for joint interface lubrication

Development of high-performance joint injection lubricants has become the focus in the field of osteoarthritis treatment. Herein, natural product of angelica essential oil combined with the graphene oxide were prepared to the stable Pickering emulsion as a biological lubricant. The tribological properties of the Pickering emulsion under different friction conditions were studied. The lubricating mechanism was revealed and the biological activities were evaluated. Results showed that the prepared Pickering emulsion displayed superior lubrication property at the Ti6Al4V biological material interface. The maximum friction reduction and anti-wear abilities of the Pickering emulsion were improved by 36% and 50% compared to water, respectively. This was primarily due to the action of the double-layer lubrication films composed of the graphene oxide and angelica essential oil molecules. It was worth noting that the friction reduction effect of the Pickering emulsion at the natural cartilage interface was higher about 19% than that of HA used in clinic for OA commonly. In addition, the Pickering emulsion also displayed antioxidant activity and cell biocompatibility, showing a good clinical application prospect in the future.

Biomimetic NO Scavenging Hyaluronic Acid Nanoparticles Enable Targeted Delivery of MTX and Integrated Management of Rheumatoid Arthritis

Rheumatoid arthritis (RA) is a complicated chronic disorder of the immune system, featured with severe inflammatory joints, synovium hyperplasia, articular cartilage, and bone damage. In the RA microenvironment, RA-involved cells, overproduced nitric oxide (NO), and pro-inflammatory cytokines are highly interplayed and mutually reinforced, which form a vicious circle and play crucial roles in the formation and progression of RA. To comprehensively break the vicious circle and obtain the maximum benefits, we have developed neutrophil membrane-camouflaged NO scavenging nanoparticles based on an NO-responsive hyaluronic acid derivative for delivery of MTX. These multifunctional nanoparticles (NNO-NPs/MTX), by inheriting the membrane functions of the source cells, possess prolonged circulation and specific localization at the inflamed sites when administrated in the body. Remarkably, NNO-NPs/MTX can neutralize the pro-inflammatory cytokines via the outer membrane receptors, scavenge NO, and be responsively disassociated to release MTX for RA-involved cell regulation and HA for lubrication in the RA sites. In a collagen-induced arthritis mouse model, NNO-NPs/MTX exhibits a significant anti-inflammation effect and effectively alleviates the characteristic RA symptoms such as synovial hyperplasia and cartilage destruction, realizing the synergistic and boosted therapeutic outcome against intractable RA. Thus, NNO-NPs/MTX provides a promising and potent platform to integrately treat RA.

Carbene-mediated gelatin and hyaluronic acid hydrogel paints with ultra adhesive ability for arthroscopic cartilage repair

In articular cartilage defect, particularly in arthroscopy, regenerative hydrogels are urgently needed. It should be able to firmly adhere to the cartilage tissue and maintain sufficient mechanical strength to withstand approximately 10 kPa of arthroscopic hydraulic flushing. In this study, we report a carbene-mediated ultra adhesive hybrid hydrogel paints for arthroscopic cartilage repair, which combined the photo initiation of double crosslinking system with the addition of diatomite, as a further reinforcing agent and biological inorganic substances. The double network consisting of ultraviolet initiated polymerization of hyaluronic acid methacrylate (HAMA) and carbene insertion chemistry of diazirine-grafted gelatin (GelDA) formed an ultra-strong adhesive hydrogel paint (H2G5DE). Diatomite helped the H2G5DE hydrogel paint firmly adhere to the cartilage defect, withstanding nearly 100 kPa of hydraulic pressure, almost 10 times that in clinical arthroscopy. Furthermore, the H2G5DE hydrogel supported cell growth, proliferation, and migration, thus successfully repairing cartilage defects. Overall, this study demonstrates a proof-of-concept of ultra-adhesive polysaccharide hydrogel paints, which can firmly adhere to the articular cartilage defects, can resist continuous hydraulic pressure, can promote effective cartilage regeneration, and is very suitable for minimally invasive arthroscopy.

Advances in viscosupplementation and tribosupplementation for early-stage osteoarthritis therapy

Joint kinematic instability, arising from congenital or acquired musculoskeletal pathoanatomy or from imbalances in anabolism and catabolism induced by pathophysiological factors, leads to deterioration of the composition, structure and function of cartilage and, ultimately, progression to osteoarthritis (OA). Alongside articular cartilage degeneration, synovial fluid lubricity decreases in OA owing to a reduction in the concentration and molecular weight of hyaluronic acid and surface-active mucinous glycoproteins that form a lubricating film over the articulating joint surfaces. Minimizing friction between articulating joint surfaces by lubrication is fundamental for decreasing hyaline cartilage wear and for maintaining the function of synovial joints. Augmentation with highly viscous supplements (that is, viscosupplementation) offers one approach to re-establishing the rheological and tribological properties of synovial fluid in OA. However, this approach has varied clinical outcomes owing to limited intra-articular residence time and ineffective mechanisms of chondroprotection. This Review discusses normal hyaline cartilage function and lubrication and examines the advantages and disadvantages of various strategies for restoring normal joint lubrication. These strategies include contemporary viscosupplements that contain antioxidants, anti-inflammatory drugs or platelet-rich plasma and new synthetic synovial fluid additives and cartilage matrix enhancers. Advanced biomimetic tribosupplements offer promise for mitigating cartilage wear, restoring joint function and, ultimately, improving patient care.

Hyaluronic-Acid-Nanomedicine Hydrogel for Enhanced Treatment of Rheumatoid Arthritis by Mediating Macrophage-Synovial Fibroblast Cross-Talk

The occurrence of rheumatoid arthritis (RA) is highly correlated with progressive and irreversible damage of articular cartilage and continuous inflammatory response. Here, inspired by the unique structure of synovial lipid-hyaluronic acid (HA) complex, we developed supramolecular HA-nanomedicine hydrogels for RA treatment by mediating macrophage-synovial fibroblast cross-talk through locally sustained release of celastrol (CEL). Molecular dynamics simulation confirmed that HA conjugated with hydrophobic segments could interspersed into the CEL-loaded [poly(ε-caprolactone-co-1,4,8-trioxa[4.6]spiro-9-undecanone)-poly(ethylene glycol)-poly(ε-caprolaone-co-1,4,8-trioxa[4.6]spiro-9-undecanone] (PECT) nanoparticles to form the supramolecular nanomedicine hydrogel HA-poly(ε-caprolactone-co-1,4,8-trioxa[4.6]spiro-9-un-decanone)/PECT@CEL (HP@CEL), enabling fast hydrogel formation after injection and providing a 3-dimensional environment similar with synovial region. More importantly, the controlled release of CEL from HP@CEL inhibited the macrophage polarization toward the proinflammatory M1 phenotype and further suppressed the proliferation of synovial fibroblasts by regulating the Toll-like receptor pathway. In collagen-induced arthritis model in mice, HP@CEL hydrogel treatment substantial attenuated clinical symptoms and bone erosion and improved the extracellular matrix deposition and bone regeneration in ankle joint. Altogether, such a bioinspired injectable polymer-nanomedicine hydrogel represents an effective and promising strategy for suppressing RA progression through augmenting the cross-talk of macrophages and synovial fibroblast for regulation of chronic inflammation.

A Mechanically Resilient Soft Hydrogel Improves Drug Delivery for Treating Post-Traumatic Osteoarthritis in Physically Active Joints

Intra-articular delivery of disease-modifying osteoarthritis drugs (DMOADs) is likely to be most effective in early post-traumatic osteoarthritis (PTOA) when symptoms are minimal and patients are physically active. DMOAD delivery systems therefore must withstand repeated mechanical loading without affecting the drug release kinetics. Although soft materials are preferred for DMOAD delivery, mechanical loading can compromise their structural integrity and disrupt drug release. Here, we report a mechanically resilient soft hydrogel that rapidly self-heals under conditions resembling human running while maintaining sustained release of the cathepsin-K inhibitor L-006235 used as a proof-of-concept DMOAD. Notably, this hydrogel outperformed a previously reported hydrogel designed for intra-articular drug delivery, used as a control in our study, which neither recovered nor maintained drug release under mechanical loading. Upon injection into mouse knee joints, the hydrogel showed consistent release kinetics of the encapsulated agent in both treadmill-running and non-running mice. In a mouse model of aggressive PTOA exacerbated by treadmill running, L-006235 hydrogel markedly reduced cartilage degeneration. To our knowledge, this is the first hydrogel proven to withstand human running conditions and enable sustained DMOAD delivery in physically active joints, and the first study demonstrating reduced disease progression in a severe PTOA model under rigorous physical activity, highlighting the hydrogel's potential for PTOA treatment in active patients.

Bio-nanoparticles loaded with synovial-derived exosomes ameliorate osteoarthritis progression by modifying the oxidative microenvironment

BACKGROUND AND AIMS

Osteoarthritis (OA) is a prevalent degenerative joint disorder, marked by the progressive degeneration of joint cartilage, synovial inflammation, and subchondral bone hyperplasia. The synovial tissue plays a pivotal role in cartilage regulation. Exosomes (EXOs), small membrane-bound vesicles released by cells into the extracellular space, are crucial in mediating intercellular communication and facilitating the exchange of information between tissues. Our study aimed to devise a hydrogel microsphere infused with SOD3-enriched exosomes (S-EXOs) to protect cartilage and introduce a novel, effective approach for OA treatment.

MATERIALS AND METHODS

We analyzed single-cell sequencing data from 4247 cells obtained from the GEO database. Techniques such as PCR, Western Blot, immunofluorescence (IF), and assays to measure oxidative stress levels were employed to validate the cartilage-protective properties of the identified key protein, SOD3. In vivo, OA mice received intra-articular injections of S-EXOs bearing hydrogel microspheres, and the effectiveness was assessed using safranine O (S.O) staining and IF.

RESULTS

Single-cell sequencing data analysis suggested that the synovium influences cartilage via the exocrine release of SOD3. Our findings revealed that purified S-EXOs enhanced antioxidant capacity of chondrocytes, and maintained extracellular matrix metabolism stability. The S-EXO group showed a significant reduction in mitoROS and ROS levels by 164.2% (P < 0.0001) and 142.7% (P < 0.0001), respectively, compared to the IL-1β group. Furthermore, the S-EXO group exhibited increased COL II and ACAN levels, with increments of 2.1-fold (P < 0.0001) and 3.1-fold (P < 0.0001), respectively, over the IL-1β group. Additionally, the S-EXO group showed a decrease in MMP13 and ADAMTS5 protein expression by 42.3% (P < 0.0001) and 44.4% (P < 0.0001), respectively. It was found that S-EXO-containing hydrogel microspheres could effectively deliver SOD3 to cartilage and significantly mitigate OA progression. The OARSI score in the S-EXO microsphere group markedly decreased (P < 0.0001) compared to the OA group.

CONCLUSION

The study demonstrated that the S-EXOs secreted by synovial fibroblasts exert a protective effect on chondrocytes, and microspheres laden with S-EXOs offer a promising therapeutic alternative for OA treatment.

Role of Natural Binding Proteins in Therapy and Diagnostics

This review systematically investigates the critical role of natural binding proteins (NBPs), encompassing DNA-, RNA-, carbohydrate-, fatty acid-, and chitin-binding proteins, in the realms of oncology and diagnostics. In an era where cancer continues to pose significant challenges to healthcare systems worldwide, the innovative exploration of NBPs offers a promising frontier for advancing both the diagnostic accuracy and therapeutic efficacy of cancer management strategies. This manuscript provides an in-depth examination of the unique mechanisms by which NBPs interact with specific molecular targets, highlighting their potential to revolutionize cancer diagnostics and therapy. Furthermore, it discusses the burgeoning research on aptamers, demonstrating their utility as 'nucleic acid antibodies' for targeted therapy and precision diagnostics. Despite the promising applications of NBPs and aptamers in enhancing early cancer detection and developing personalized treatment protocols, this review identifies a critical knowledge gap: the need for comprehensive studies to understand the diverse functionalities and therapeutic potentials of NBPs across different cancer types and diagnostic scenarios. By bridging this gap, this manuscript underscores the importance of NBPs and aptamers in paving the way for next-generation diagnostics and targeted cancer treatments.

Novel biomimetic macromolecules system for highly efficient lubrication, ROS scavenging and osteoarthritis treatment

The early stages of osteoarthritis (OA) in the joints are typically characterized by two key factors: the dysfunction of articular cartilage lubrication and inflammation resulting from the excessive production of reactive oxygen species (ROS). Synthetic injectable macromolecular materials present great potential for preventing the progression of early OA. In this study, to mimic the excellent lubricity of brush-like aggregates found in natural synovial fluid, we develop a novel macromolecular biolubricant (CS-PS-DA) by integrating adhesion and hydration groups onto backbone of natural biomacromolecules. CS-PS-DA exhibits a strong affinity for cartilage surfaces, enabling the formation of a stable lubrication layer at the sliding interface of degraded cartilages to restore joint lubrication performance. In vitro results from ROS scavenging and anti-inflammatory experiments indicate the great advantage of CS-PS-DA to decrease the levels of proinflammatory cytokines by inhibiting ROS overproduction. Finally, in vivo rats OA model demonstrates that intra-cavitary injection of CS-PS-DA could effectively resist cartilage wear and mitigated inflammation in the joints. This novel biolubricant provides a new and timely strategy for the treatment of OA.

Fundamental, mechanism and development of hydration lubrication: From bio-inspiration to artificial manufacturing

Friction and lubrication are ubiquitous in all kinds of movements and play a vital role in the smooth operation of production machinery. Water is indispensable both in the lubrication systems of natural organisms and in hydration lubrication systems. There exists a high degree of similarity between these systems, which has driven the development of hydration lubrication from biomimetic to artificial manufacturing. In particular, significant advancements have been made in the understanding of the mechanisms of hydration lubrication over the past 30 years. This enhanced understanding has further stimulated the exploration of biomimetic inspiration from natural hydration lubrication systems, to develop novel artificial hydration lubrication systems that are cost-effective, easily transportable, and possess excellent capability. This review summarizes the recent experimental and theoretical advances in the understanding of hydration-lubrication processes. The entire paper is divided into three parts. Firstly, surface interactions relevant to hydration lubrication are discussed, encompassing topics such as hydrogen bonding, hydration layer, electric double layer force, hydration force, and Stribeck curve. The second part begins with an introduction to articular cartilage in biomaterial lubrication, discussing its compositional structure and lubrication mechanisms. Subsequently, three major categories of bio-inspired artificial manufacturing lubricating material systems are presented, including hydrogels, polymer brushes (e.g., neutral, positive, negative and zwitterionic brushes), hydration lubricant additives (e.g., nano-particles, polymers, ionic liquids), and their related lubrication mechanism is also described. Finally, the challenges and perspectives for hydration lubrication research and materials development are presented.

Harnessing Nanomedicine for Cartilage Repair: Design Considerations and Recent Advances in Biomaterials

Cartilage injuries are escalating worldwide, particularly in aging society. Given its limited self-healing ability, the repair and regeneration of damaged articular cartilage remain formidable challenges. To address this issue, nanomaterials are leveraged to achieve desirable repair outcomes by enhancing mechanical properties, optimizing drug loading and bioavailability, enabling site-specific and targeted delivery, and orchestrating cell activities at the nanoscale. This review presents a comprehensive survey of recent research in nanomedicine for cartilage repair, with a primary focus on biomaterial design considerations and recent advances. The review commences with an introductory overview of the intricate cartilage microenvironment and further delves into key biomaterial design parameters crucial for treating cartilage damage, including microstructure, surface charge, and active targeting. The focal point of this review lies in recent advances in nano drug delivery systems and nanotechnology-enabled 3D matrices for cartilage repair. We discuss the compositions and properties of these nanomaterials and elucidate how these materials impact the regeneration of damaged cartilage. This review underscores the pivotal role of nanotechnology in improving the efficacy of biomaterials utilized for the treatment of cartilage damage.

A Dual Functional Bioinspired Lubricant for Osteoarthritis Treatment and Potential Prevention

Osteoarthritis (OA), primarily characterized by the deterioration of articular cartilage, is a highly prevalent joint-disabling disease. The pathological onset and progression of OA are closely related to cartilage lubrication dysfunction and synovial inflammation. Synergistic options targeted at restorative lubrication and anti-inflammation are expected to be the most attractive candidates to treat OA and perhaps help prevent it. Herein, a bioinspired lubricant (HA/PA@Lipo) was fabricated by combining anionic hyaluronan-graft-poly(2-acrylamide-2-methylpropanesulfonic acid sodium salt) (HA/PA) with cationic liposomes (Lipo) via electrostatic interaction. HA/PA@Lipo mimicked the lubrication complex located on the outer cartilage surface and was endowed cartilage with excellent cartilage-lubricating performances. After the antioxidant gallic acid (GA) was loaded for dual functionality, HA/PA@Lipo-GA was prepared with added anti-inflammatory properties. HA/PA@Lipo-GA showed favorable biocompatibility with C28/I2 cells, inhibited the production of reactive oxygen, and regulated the expression levels of anabolic genes and proteins. The therapeutic effects of HA/PA@Lipo-GA were evaluated using a sodium iodoacetate-induced OA rat model, and the preventive effects of HA/PA@Lipo-GA were estimated in vivo. The results suggested the robust potential of HA/PA@Lipo-GA with dual functions as a candidate option for OA treatment and prevention.

Utilizing bioprinting to engineer spatially organized tissues from the bottom-up

In response to the growing demand for organ substitutes, tissue engineering has evolved significantly. However, it is still challenging to create functional tissues and organs. Tissue engineering from the 'bottom-up' is promising on solving this problem due to its ability to construct tissues with physiological complexity. The workflow of this strategy involves two key steps: the creation of building blocks, and the subsequent assembly. There are many techniques developed for the two pivotal steps. Notably, bioprinting is versatile among these techniques and has been widely used in research. With its high level of automation, bioprinting has great capacity in engineering tissues with precision and holds promise to construct multi-material tissues. In this review, we summarize the techniques applied in fabrication and assembly of building blocks. We elaborate mechanisms and applications of bioprinting, particularly in the 'bottom-up' strategy. We state our perspectives on future trends of bottom-up tissue engineering, hoping to provide useful reference for researchers in this field.

Revolutionizing osteoarthritis treatment: How mesenchymal stem cells hold the key

Osteoarthritis (OA) is a multifaceted disease characterized by imbalances in extracellular matrix metabolism, chondrocyte and synoviocyte senescence, as well as inflammatory responses mediated by macrophages. Although there have been notable advancements in pharmacological and surgical interventions, achieving complete remission of OA remains a formidable challenge, oftentimes accompanied by significant side effects. Mesenchymal stem cells (MSCs) have emerged as a promising avenue for OA treatment, given their ability to differentiate into chondrocytes and facilitate cartilage repair, thereby mitigating the impact of an inflammatory microenvironment induced by macrophages. This comprehensive review aims to provide a concise overview of the diverse roles played by MSCs in the treatment of OA, while elucidating the underlying mechanisms behind these contributions. Specifically, the roles include: (a) Promotion of chondrocyte and synoviocyte regeneration; (b) Inhibition of extracellular matrix degradation; (c) Attenuating the macrophage-induced inflammatory microenvironment; (d) Alleviation of pain. Understanding the multifaceted roles played by MSCs in OA treatment is paramount for developing novel therapeutic strategies. By harnessing the regenerative potential and immunomodulatory properties of MSCs, it may be possible to devise more effective and safer approaches for managing OA. Further research and clinical studies are warranted to optimize the utilization of MSCs and realize their full potential in the field of OA therapeutics.

Osteoinductive Dental Pulp Stem Cell-Derived Extracellular Vesicle-Loaded Multifunctional Hydrogel for Bone Regeneration

Stem cell-derived extracellular vesicles (EVs) show great potential for promoting bone tissue regeneration. However, normal EVs (Nor-EVs) have a limited ability to direct tissue-specific regeneration. Therefore, it is necessary to optimize the osteogenic capacity of EV-based systems for repairing extensive bone defects. Herein, we show that hydrogels loaded with osteoinductive dental pulp stem cell-derived EVs (Ost-EVs) enhanced bone tissue remodeling, resulting in a 2.23 ± 0.25-fold increase in the expression of bone morphogenetic protein 2 (BMP2) compared to the hydrogel control group. Moreover, Ost-EVs led to a higher expression of alkaline phosphatase (ALP) (1.88 ± 0.16 of Ost-EVs relative to Nor-EVs) and the formation of orange-red calcium nodules (1.38 ± 0.10 of Ost-EVs relative to Nor-EVs) in vitro. RNA sequencing revealed that Ost-EVs showed significantly high miR-1246 expression. An ideal hydrogel implant should also adhere to surrounding moist tissues. In this study, we were drawn to mussel-inspired adhesive modification, where the hydrogel carrier was crafted from hyaluronic acid (HA) and polyethylene glycol derivatives, showcasing impressive tissue adhesion, self-healing capabilities, and the ability to promote bone growth. The modified HA (mHA) hydrogel was also responsive to environmental stimuli, making it an effective carrier for delivering EVs. In an ectopic osteogenesis animal model, the Ost-EV/hydrogel system effectively alleviated inflammation, accelerated revascularization, and promoted tissue mineralization. We further used a rat femoral condyle defect model to evaluate the in situ osteogenic ability of the Ost-EVs/hydrogel system. Collectively, our results suggest that Ost-EVs combined with biomaterial-based hydrogels hold promising potential for treating bone defects.

Protein-based bioactive coatings: from nanoarchitectonics to applications

Protein-based bioactive coatings have emerged as a versatile and promising strategy for enhancing the performance and biocompatibility of diverse biomedical materials and devices. Through surface modification, these coatings confer novel biofunctional attributes, rendering the material highly bioactive. Their widespread adoption across various domains in recent years underscores their importance. This review systematically elucidates the behavior of protein-based bioactive coatings in organisms and expounds on their underlying mechanisms. Furthermore, it highlights notable advancements in artificial synthesis methodologies and their functional applications in vitro. A focal point is the delineation of assembly strategies employed in crafting protein-based bioactive coatings, which provides a guide for their expansion and sustained implementation. Finally, the current trends, challenges, and future directions of protein-based bioactive coatings are discussed.

Articular cartilage repair biomaterials: strategies and applications

Articular cartilage injury is a frequent worldwide disease, while effective treatment is urgently needed. Due to lack of blood vessels and nerves, the ability of cartilage to self-repair is limited. Despite the availability of various clinical treatments, unfavorable prognoses and complications remain prevalent. However, the advent of tissue engineering and regenerative medicine has generated considerable interests in using biomaterials for articular cartilage repair. Nevertheless, there remains a notable scarcity of comprehensive reviews that provide an in-depth exploration of the various strategies and applications. Herein, we present an overview of the primary biomaterials and bioactive substances from the tissue engineering perspective to repair articular cartilage. The strategies include regeneration, substitution, and immunization. We comprehensively delineate the influence of mechanically supportive scaffolds on cellular behavior, shedding light on emerging scaffold technologies, including stimuli-responsive smart scaffolds, 3D-printed scaffolds, and cartilage bionic scaffolds. Biologically active substances, including bioactive factors, stem cells, extracellular vesicles (EVs), and cartilage organoids, are elucidated for their roles in regulating the activity of chondrocytes. Furthermore, the composite bioactive scaffolds produced industrially to put into clinical use, are also explicitly presented. This review offers innovative solutions for treating articular cartilage ailments and emphasizes the potential of biomaterials for articular cartilage repair in clinical translation.

Functional nano drug delivery system with dual lubrication and immune escape for treating osteoarthritis

Local drug delivery via inter-articular injection offers a promising scenario to treat the most common joint disease, osteoarthritis (OA), which is closely associated with the increased friction or cartilage degeneration and the inflammatory syndrome of synovium. Therefore, it is quite necessary to improve the retention of drug delivery system within synovial joint, simultaneously restore the lubrication of degraded cartilage and meanwhile alleviate the inflammation. In this study, we propose a hydrophilic coating modified nano-liposome drug carrier (PMPC-Lipo) to achieve these functions. A modified chain transfer agent was utilized to polymerize 2-methacryloyloxyethyl phosphorylcholine (MPC), the obtained polymer, combined with lecithin and cholesterol, formed a liposome (PMPC-Lipo) where poly (MPC) acted as hydrophilic coating. PMPC-Lipo was found to restore the lubrication of mechanically damage cartilage (mimicking OA conditions) to the level like healthy cartilage due to the hydration lubrication. Additionally, due to the presence of poly (MPC), we also found PMPC-Lipo avoid the recognition of macrophage and thus escape from the phagocytosis to prolong its retention in synovial joint. Furthermore, after encapsulating gallic acid (GA) into PMPC-Lipo, the obtained GA-PMPC-Lipo can effectively scavenge reactive oxygen species and restore the imbalance of matrix secretion in inflammatory chondrocytes. Collectively, the proposed GA-PMPC-Lipo may provide a new idea for osteoarthritis treatment by providing both long-term effective drug action and excellent lubrication properties.

Meniscus-Inspired Self-Lubricating and Friction-Responsive Hydrogels for Protecting Articular Cartilage and Improving Exercise

Meniscus injuries are associated with the degeneration of cartilage and development of osteoarthritis (OA). It is challenging to protect articular cartilage and improve exercise when a meniscus injury occurs. Herein, inspired by the components and functions of the meniscus, we developed a self-lubricating and friction-responsive hydrogel that contains nanoliposomes loaded with diclofenac sodium (DS) and Kartogenin (KGN) for anti-inflammation and cartilage regeneration. When the hydrogel was injected into the meniscus injury site, the drug-loaded nanoliposomes were released from the hydrogel in a friction-responsive manner and reassembled to form hydration layers that lubricate joints during movement. Meanwhile, DS and KNG were constantly released from the nanoliposomes to mitigate inflammation and promote cartilage regeneration. Additionally, this hydrogel exhibited favorable injectability, mechanical properties, fatigue resistance, and prolonged degradation. In vivo experiments demonstrated that injection of the hydrogel effectively improved exercise performance and protected the articular cartilage of rats, suggesting it as a potential therapeutic approach for meniscal injuries.

Emerging roles of RNA binding proteins in intervertebral disc degeneration and osteoarthritis

The etiology of intervertebral disc degeneration (IDD) and osteoarthritis (OA) is complex and multifactorial. Both predisposing genes and environmental factors are involved in the pathogenesis of IDD and OA. Moreover, epigenetic modifications affect the development of IDD and OA. Dysregulated phenotypes of nucleus pulposus (NP) cells and OA chondrocytes, including apoptosis, extracellular matrix disruption, inflammation, and angiogenesis, are involved at all developmental stages of IDD and OA. RNA binding proteins (RBPs) have recently been recognized as essential post-transcriptional regulators of gene expression. RBPs are implicated in many cellular processes, such as proliferation, differentiation, and apoptosis. Recently, several RBPs have been reported to be associated with the pathogenesis of IDD and OA. This review briefly summarizes the current knowledge on the RNA-regulatory networks controlled by RBPs and their potential roles in the pathogenesis of IDD and OA. These initial findings support the idea that specific modulation of RBPs represents a promising approach for managing IDD and OA.

A polymer network architecture provides superior cushioning and lubrication of soft tissue compared to a linear architecture

We report the relationships between linear vs. network polymer architecture and biomechanical outcomes including lubrication and cushioning when the polymers are applied to the surface of articulating knee cartilage. Aqueous formulations of the bioinspired polymer poly(2-methacryloyloxylethyl phosphorylcholine) (pMPC) exhibit tuneable rheological properties, with network pMPC exhibiting increased elasticity and viscosity compared to linear pMPC. Application of a polymer network, compared to a linear one, to articulating tissue surfaces reduces friction, lessens tissue strain, minimizes wear, and protects tissue - thereby improving overall tissue performance. Administration of the network pMPC to the middle carpal joint of skeletally mature horses elicits a safe response similar to saline as monitored over a 70 day period.

Mimicking Antioxidases and Hyaluronan Synthase: A Zwitterionic Nanozyme for Photothermal Therapy of Osteoarthritis

Restoring joint homeostasis is crucial for relieving osteoarthritis (OA). Current strategies are limited to unilateral efforts in joint lubrication, inhibition of inflammation, free radicals scavenging, and cartilage regeneration. Herein, by modifying molybdenum disulfide (MoS2 ) with Mg2+ -doped polydopamine and coating with polysulfobetaines, a dual-bionic photothermal nanozyme (MPMP) is constructed to mimic antioxidases/hyaluronan synthase for OA therapy. Photothermally enhanced lubrication lowers the coefficient of friction (0.028) in the early stage of OA treatment. The antioxidases-mimicking properties of MPMP nanozyme contribute to eliminating reactive oxygen and nitrogen species (ROS/RNS) (over 90% of scavenging ratio for H2 O2 /·OH/O· 2 - /DPPH/ABTS+ ) and supplying O2 . With NIR irradiation, the MPMP nanozyme triggers thermogenesis (upregulating HSP70 expression) and Mg2+ release, which promotes the chondrogenesis in inflammatory conditions by deactivating NF-κB/IL-17 signaling pathways and enhancing MAPK signaling pathway. Benefiting from HSP70 and Mg2+ , MPMP-NIR shows HAS-mimicking activity to increase the intracellular (twofold) and extracellular (3.12-fold) HA production. Therefore, MPMP-NIR demonstrates superior spatiotemporally therapeutic effect on OA in mice model, in terms of osteophytes (83.41% of reduction), OARSI scores (88.57% of reduction), and ACAN expression (2.70-fold of increment). Hence, insights into dual-bionic nanozymes can be a promising strategy for OA therapy or other inflammation-related diseases.

Biomimetic approach for an articular cartilage patch: Combination of decellularized cartilage matrix and silk-elastin-like-protein (SELP) hydrogel

Articular cartilage degradation due to injury, disease and aging is a common clinical issue as current regenerative therapies are unable to fully replicate the complex microenvironment of the native tissue which, being avascular, is featured by very low ability to self-regenerate. The extracellular matrix (ECM), constituting almost 90% of the entire tissue, plays a critical role in its function and resistance to compressive forces. In this context, the current tissue engineering strategies are only partially effective in restoring the biology and function of the native tissue. A main issue in tissue regeneration is treatment failure due to scarce integration of the engineered construct, often following a gradual detachment of the graft. In this scenario, we aimed to create an adhesive patch able to adequately support cartilage regeneration as a promising tool for the treatment of cartilage injuries and diseases. For this, we produced an engineered construct composed of decellularized ECM (dECM) obtained from horse joint cartilage, to support tissue regeneration, coupled with a Silk-Elastin-Like Proteins (SELP) hydrogel, which acts as a biological glue, to guarantee an adequate adherence to the host tissue. Following the production of the two biomaterials we characterized them by assessing: 1) dECM morphological, chemical, and ultrastructural features along with its capability to support chondrocyte proliferation, specific marker expression and ECM synthesis; 2) SELP microarchitecture, cytocompatibility and mechanical properties. Our results demonstrated that both materials hold unique properties suitable to be exploited to produce a tailored microenvironment to support cell growth and differentiation providing a proof of concept concerning the in vitro biological and mechanical efficacy of the construct. The SELP hydrogel displayed a very interesting physical behavior due to its high degree of resistance to mechanical stress, which is generally associated with physiological mechanical load during locomotion. Intriguingly, the shear-thinning behavior of the hydrogel may also make it suitable to be applied and spread over non-homogeneous surfaces, therefore, we hypothesize that the hybrid biomaterial proposed may be a real asset in the treatment of cartilage defects and injuries.

Biomimetic Hyaluronic Acid-Based Brush Polymers Modulate Chondrocyte Homeostasis via ROS/Ca2+/TRPV4

Bionic mimics using natural cartilage matrix molecules can modulate the corresponding metabolic activity by improving the microenvironment of chondrocytes. A bionic brush polymer, HA/PX, has been found to reverse the loss of cartilage extracellular matrix (ECM) and has promising applications in the clinical treatment of osteoarthritis (OA). However, the unknown bioremediation mechanism of HA/PX severely hinders its clinical translation. In OA, the massive loss of the ECM may be attributed to a decrease in transient receptor potential vanilloid 4 (TRPV4) activity, which affects reactive oxygen species (ROS) clearance and [Ca2+]i signaling, initiating downstream catabolic pathways. In this study, we investigated the bioremediation mechanism of HA/PX in a model of interleukin 1β (IL-1β)-induced inflammation. Through TRPV4, HA/PX reduced ROS accumulation in chondrocytes and enhanced [Ca2+]i signaling, reflecting a short-term protection capacity for chondrocytes. In addition, HA/PX balanced the metabolic homeostasis of chondrocytes via TRPV4, including promoting the secretion of type II collagen (Col-II) and aggrecan, the major components of the ECM, and reducing the expression of matrix metal-degrading enzyme (MMP-13), exerting long-term protective effects on chondrocytes. Molecular dynamics (MD) simulations showed that HA/PX could act as a TRPV4 activator. Our results suggest that HA/PX can regulate chondrocyte homeostasis via ROS/Ca2+/TRPV4, thereby improving cartilage regeneration. Because the ECM is a prevalent feature of various cell types, HA/PX holds promising potential for improving regeneration and disease modification for not only cartilage-related healthcare but many other tissues and diseases.

HYBID in osteoarthritis: Potential target for disease progression

HYBID is a new hyaluronan-degrading enzyme and exists in various cells of the human body. Recently, HYBID was found to over-express in the osteoarthritic chondrocytes and fibroblast-like synoviocytes. According to these researches, high level of HYBID is significantly correlated with cartilage degeneration in joints and hyaluronic acid degradation in synovial fluid. In addition, HYBID can affect inflammatory cytokine secretion, cartilage and synovium fibrosis, synovial hyperplasia via multiple signaling pathways, thereby exacerbating osteoarthritis. Based on the existing research of HYBID in osteoarthritis, HYBID can break the metabolic balance of HA in joints through the degradation ability independent of HYALs/CD44 system and furthermore affect cartilage structure and mechanotransduction of chondrocytes. In particular, in addition to HYBID itself being able to trigger some signaling pathways, we believe that low-molecular-weight hyaluronan produced by excess degradation can also stimulate some disease-promoting signaling pathways by replacing high-molecular-weight hyaluronan in joints. The specific role of HYBID in osteoarthritis is gradually revealed, and the discovery of HYBID raises the new way to treat osteoarthritis. In this review, the expression and basic functions of HYBID in joints were summarized, and reveal potential role of HYBID as a key target in treatment for osteoarthritis.

Advances in mechanically robust and biomimetic polysaccharide-based constructs for cartilage tissue engineering

The purpose of cartilage tissue engineering is to provide artificial constructs with biological functions and mechanical features that resemble native tissue to improve tissue regeneration. Biochemical characteristics of the cartilage extracellular matrix (ECM) microenvironment provide a platform for researchers to develop biomimetic materials for optimal tissue repair. Due to the structural similarity of polysaccharides into physicochemical characteristics of cartilage ECM, these natural polymers capture special attention for developing biomimetic materials. The mechanical properties of constructs play a crucial influence in load-bearing cartilage tissues. Moreover, the addition of appropriate bioactive molecules to these constructs can promote chondrogenesis. Here, we discuss polysaccharide-based constructs that can be used to create substitutes for cartilage regeneration. We intend to focus on newly developed bioinspired materials, fine-tuning the mechanical properties of constructs, the design of carriers loaded by chondroinductive agents, and development of appropriate bioinks as a bioprinting approach for cartilage regeneration.

Visualizable and Lubricating Hydrogel Microspheres Via NanoPOSS for Cartilage Regeneration

The monitoring of tissue regeneration is particularly important. However, most materials do not allow direct observation of the regeneration process in the cartilage layer. Here, using sulfhydryl polyhedral oligomeric silsesquioxane (POSS-SH) as a nano-construction platform, poly(ethylene glycol) (PEG), Kartogenin (KGN), hydrogenated soya phosphatidylcholine (HSPC), and fluorescein are linked through the "click chemistry" method to construct nanomaterial with fluorescence visualization for cartilage repair: POSS linked with PEG, KGN, HSPC, and fluorescein (PPKHF). PPKHF nanoparticles are encapsulated with hyaluronic acid methacryloyl to prepare PPKHF-loaded microfluidic hyaluronic acid methacrylate spheres (MHS@PPKHF) for in situ injection into the joint cavity using microfluidic technology. MHS@PPKHF forms a buffer lubricant layer in the joint space to reduce friction between articular cartilages, while releasing encapsulated positively charged PPKHF to the deep cartilage through electromagnetic force, facilitating visualization of the location of the drug via fluorescence. Moreover, PPKHF facilitates differentiation of bone marrow mesenchymal stem cells into chondrocytes, which are located in the subchondral bone. In animal experiment, the material accelerates cartilage regeneration while allowing monitoring of cartilage layer repair progression via fluorescence signals. Thus, these POSS-based micro-nano hydrogel microspheres can be used for cartilage regeneration and monitoring and potentially for clinical osteoarthritis therapy.

New trends for osteoarthritis: Biomaterials, models and modeling

The burden of osteoarthritis (OA), one of the major causes of functional disabilities in humans and animals, continues to increase worldwide while no disease-modifying OA drugs (DMOADs) that either slow down or reverse disease progression have been made available. Here, we provide a brief overview of recent advances in: designing new OA drug delivery approaches, focusing on lubrication-based biomaterials and drug delivery systems, such as hydrogels, liposomes, dendrimers, micro- and nanoparticles; using either large (horse) or small (zebrafish) relevant animal models to evaluate new therapeutic strategies; and OA in vitro modeling, focusing on 3D (organoid) models of cartilage regarding the Replace, Reduce and Refine (3R) principle of animal experimentation.

Recent Progress in Hydrogel-Based Synthetic Cartilage: Focus on Lubrication and Load-Bearing Capacities

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.

Intra-articular treatment of temporomandibular joint osteoarthritis by injecting actively-loaded meloxicam liposomes with dual-functions of anti-inflammation and lubrication

Temporomandibular joint (TMJ) osteoarthritis is a common osteochondral degenerative disease which can severely affect patient's mouth opening and mastication. Meloxicam (MLX), one of the most widely used non-steroidal anti-inflammatory drugs, is the main clinical therapy for the treatment of TMJ osteoarthritis. However, the clinical effect is greatly compromised because of its poor water solubility and high lipophilicity. In the present study, we developed an actively-loaded liposomal formulation, namely MLX-Ca(AC)₂Lipo, using meglumine to enhance aqueous solubility and divalent metal (Ca²⁺) solution to improve encapsulation efficiency. By the formation of the nano-bowl shaped MLX-Ca precipitates inside the liposomes, MLX-Ca(AC)₂Lipo successfully achieved an optimal encapsulation efficiency as high as 98.4% compared with previous passive loading method (60.6%). Additionally, MLX-Ca(AC)₂Lipo maintained stable, and the slow drug release not only prolonged the duration of drug efficacy but also improved bioavailability. It was shown in the in vitro and in vivo tests that MLX-Ca(AC)₂Lipo downregulated the synthesis of the inflammatory factors (such as prostaglandin-E2) and as a consequence reduced chondrocytes apoptosis and extracellular matrix degeneration. Furthermore, the intra-articular injection of MLX-Ca(AC)₂Lipo enhanced bioinspired lubrication of TMJ, protecting the cartilage from progressive wear. In summary, MLX-Ca(AC)₂Lipo with dual-functions of anti-inflammation and lubrication is a promising nanomedicine for the treatment of TMJ osteoarthritis by intra-articular injection.

Lubricants for osteoarthritis treatment: From natural to bioinspired and alternative strategies

Osteoarthritis is the most common degenerative and highly prevalent joint disease, characterized by progressive loss and destruction of articular cartilage. The damaged cartilage surface has an increased friction, which causes patients to suffer from serious pain. Restoring the lubrication ability of the joint is central to the treatment of osteoarthritis, a key topic in medical research. A variety of lubricants have been designed to reduce friction in joints and promote cartilage tissue repair to alleviate the symptoms of osteoarthritis. Herein, we review the recent progress of lubricants from the three perspectives of natural, bioinspired, and alternative strategies for osteoarthritis treatment, as well as the structural characterization and lubrication properties of such lubricants. Specifically, natural lubricants include glycosaminoglycans, lubricin and lipids in joints, bioinspired lubricants include scaffolds mimicking hyaluronic acid or lubricin, and alternative lubricants include modified lubricants based on hyaluronic acid, lipids, nanoparticles, and peptides. We also discuss the current challenges and long-term perspectives for further research in this area.

Biomimetic chitosan-derived bifunctional lubricant with superior antibacterial and hydration lubrication performances

The lubrication deficiency in joints is a major cause of osteoarthritis. One of the most commonly used treatment means is to inject artificial lubricants, but there is a potential risk of infection during the injection process. Therefore, developing artificial lubricants with dual functions of friction-reduction and antibacterial is urgent. In this work, a novel polysaccharide-derived lubricant with simultaneous anti-bacteria and water-lubrication properties, called CS-MPC-N, is developed by grafting 2‑methacryloyloxylethyl phosphorylcholine (MPC) and nisin peptide onto backbone of chitosan (CS). Compared to the control CS, CS-MPC-N exhibits good lubrication and friction-reduction properties because of its excellent water solubility. Especially, CS-MPC-N shows low friction coefficient (0.03 ∼ 0.05) at the sliding interfaces of artificial joints materials or even natural articular cartilages. Moreover, CS-MPC-N can effectively inhibit the proliferation of Staphylococcus aureu, exhibiting excellent antibacterial effect. This kind of novel polysaccharide-derived lubricant is expected to be used in treating infectious arthritis.

Osteoarthritis year in review 2022: biology

The field of osteoarthritis (OA) biology is rapidly evolving and brilliant progress has been made this year as well. Landmark studies of OA biology published in 2021 and early 2022 were selected through PubMed search by personal opinion. These papers were classified by their molecular mechanisms, and it was largely divided into the intracellular signaling mechanisms and the inter-compartment interaction in chondrocyte homeostasis and OA progression. The intracellular signaling mechanisms involving OA progression included (1) Piezo1/transient receptor potential channels of the vanilloid subtype (TRPV) 4-mediated calcium signaling, (2) mechanical load-F-box and WD repeat domain containing 7 (FBXW7) in chondrocyte senescence, (3) mechanical loading-primary cilia-hedgehog signaling, (4) low grade inflammation by toll-like receptor (TLR)-CD14-lipopolysaccharide-binding protein (LBP) complex and inhibitor of NF-κB kinase (IKK) β-nuclear factor kappa B (NF-κB) signaling, (5) selenium pathway and reactive oxygen species (ROS) production, (6) G protein-coupled receptor (GPCR) and cyclic adenosine monophosphate (cAMP) signaling, (7) peroxisome proliferator-activated receptor α (PPARα)-acyl-CoA thioesterase 12 (ACOT12)-mediated de novo lipogenesis and (8) hypoxia-disruptor of telomeric silencing 1-like (DOT1L)-H3-lysine 79 (H3K79) methylation pathway. The studies on inter-compartment or intercellular interaction in OA progression included the following subjects; (1) the anabolic role of lubricin, glycoprotein from superficial zone cells, (2) osteoclast-chondrocyte interaction via exosomal miRNA and sphingosine 1-phosphate (S1P), (3) senescent fibroblast-like synoviocyte and chondrocyte interaction, (4) synovial macrophage and chondrocyte interaction through Flightless I, (5) αV integrin-mediated transforming growth factor beta (TGFβ) activation by mechanical loading, and (6) osteocytic TGFβ in subchondral bone thickening. Despite the disastrous Covid-19 pandemic, many outstanding studies have expanded the boundary of OA biology. They provide both critical insight into the pathophysiology as well as clues for the treatment of OA.