Living and Injectable Porous Hydrogel Microsphere with Paracrine Activity for Cartilage Regeneration

UC-MSCs based on biomimetic microniche exert excellent regulatory effects on acute brain inflammation through advantageous properties

Neuroinflammation triggered by activated microglia leads to neuronal damage and, to a certain extent, neurodegeneration. Human umbilical cord mesenchymal stem cells (UC-MSCs) have good immunomodulatory and neuroprotective effects as well as therapeutic potential for neuroinflammation-related diseases. However, the complex microenvironment created by neuroinflammation poses a challenge to transplanted UC-MSCs. The emerging biomimetic microniche (BN)-based culture technology provides new opportunities to optimize the preparation of UC-MSCs; but the fundamental changes in the characteristics of UC-MSCs based on BN remain unclear, and more reliable preclinical data are needed to support their ability to regulate inflammation. Here, we systematically studied the cellular properties and inflammation regulatory capacity of UC-MSCs in conventional static planar culture (SP-UCMSCs) and suspension culture based on BN (BN-UCMSCs). In vitro, compared with SP-UCMSCs, BN-UCMSCs not only maintained the fundamental characteristics of MSCs, but also significantly enhanced cell proliferation, adhesion, and migration capabilities, etc; notably, the paracrine function and anti-inflammatory capacity of BN-UCMSCs were also enhanced. We further established a murine model of acute brain inflammation and demonstrated that the expression level of pro-inflammatory cytokines in hippocampal and cortical tissues of the BN-UCMSCs group was significantly decreased compared with that in the SP-UCMSCs group. Subsequent transcriptomic analysis of hippocampal and cortical tissues revealed that BN-UCMSCs had the advantage of significantly reducing the expression of pro-inflammatory cytokines through the TLR4-Myd88-NF-κB axis, which was further validated at the gene and protein levels. Taken together, these data strongly indicated that BN-UCMSCs exerts excellent regulatory effects on acute brain inflammation through advantageous properties.

hAMSCs regulate EMT in the progression of experimental pulmonary fibrosis through delivering miR-181a-5p targeting TGFBR1

BACKGROUND

Pulmonary fibrosis (PF) is a common and multidimensional devastating interstitial lung disease. The development of novel and more effective interventions for PF is an urgent clinical need. A previous study has found that miR-181a-5p plays an important role in the development of PF, and human amniotic mesenchymal stem cells (hAMSCs) exert potent therapeutic potential on PF. However, whether hAMSCs act on PF by delivering miR-181a-5p and its detailed mechanism still remain unknown. Thus, this study was designed to investigate the underlying possible mechanism of hAMSCs on PF in bleomycin (BLM)-induced mouse PF model, and a co-culture system of hAMSCs and A549 cells epithelial mesenchymal transition (EMT) model, focusing on its effects on collagen deposition, EMT, and epithelial cell cycle regulation.

METHODS

hAMSCs with different miR-181a-5p expression levels were constructed. BLM (4 mg/kg) was used to create a PF model, while TGF-β1 was used to induce A549 cells to construct an EMT model. Furthermore, the effects of different miR-181a-5p expression in hAMSCs on collagen deposition and EMT during lung fibrosis were assessed in vivo and in vitro.

RESULTS

We found that hAMSCs exerted anti-fibrotic effect in BLM-induced mouse PF model. Moreover, hAMSCs also exerted protective effect on TGFβ1-induced A549 cell EMT model. Furthermore, hAMSCs ameliorated PF by promoting epithelial cell proliferation, reducing epithelial cell apoptosis, and attenuating EMT of epithelial cells through paracrine effects. hAMSCs regulated EMT in PF through delivering miR-181a-5p targeting TGFBR1.

CONCLUSIONS

Our findings reveal for the first time that hAMSCs inhibit PF by promoting epithelial cell proliferation, reducing epithelial cell apoptosis, and attenuating EMT. Mechanistically, the therapeutic effect of hMASCs on PF is achieved through delivering miR-181a-5p targeting TGFBR1.

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

This review paper explores the cutting-edge advancements in hydrogel design for articular cartilage regeneration (CR). Articular cartilage (AC) defects are a common occurrence worldwide that can lead to joint breakdown at a later stage of the disease, necessitating immediate intervention to prevent progressive degeneration of cartilage. Decades of research into the biomedical applications of hydrogels have revealed their tremendous potential, particularly in soft tissue engineering, including CR. Hydrogels are highly tunable and can be designed to meet the key criteria needed for a template in CR. This paper aims to identify those criteria, including the hydrogel components, mechanical properties, biodegradability, structural design, and integration capability with the adjacent native tissue and delves into the benefits that CR can obtain through appropriate design. Stratified-structural hydrogels that emulate the native cartilage structure, as well as the impact of environmental stimuli on the regeneration outcome, have also been discussed. By examining recent advances and emerging techniques, this paper offers valuable insights into developing effective hydrogel-based therapies for AC repair.

4D bioprinting of transformable living constructs with sustained local growth factor presentation for advanced tissue engineering applications

Traditional tissue engineering strategies focus on geometrically static tissue scaffolds, lacking the dynamic capability found in native tissues. The emerging field of 4D bioprinting offers a promising method to address this challenge. However, the requirement for consistent exogenous supplementation of growth factors (GFs) during tissue maturation poses a significant obstacle for in vivo application of 4D bioprinted constructs. We herein developed composite bioinks composed of photocrosslinkable, jammed alginate methacrylate (AlgMA) and gelatin methacrylate (GelMA), incorporating GelMA microspheres loaded with GFs to provide sustained local GF presentation over 50 days for 4D tissue bioprinting. The composite bioink exhibited excellent printability, enabling 3D printing with good accuracy (∼120 %) and fidelity (105 % - 114 %). By incorporating a photoabsorbent to enhance light attenuation, a gradient network along the light propagation pathway was generated, facilitating programmable and controllable 4D shape transformation. This process allowed the fabrication of complex living constructs with defined architectures through morphing. A proof-of-concept study on cartilage regeneration demonstrated the effectiveness of sustained GF presentation in driving tissue development, showing significant glycosaminoglycan production (GAG/DNA 10.3), and substantial upregulation of type II collagen (125.8-fold) and aggrecan (16.4-fold) mRNA expression, thereby eliminating the need for exogenous GF supplementation. This study underscores the transformative potential of integrating dynamic tissue scaffolding with sustained GF delivery, thereby addressing key limitations of traditional tissue engineering approaches and offering new avenues for tissue repair applications.

Injectable Polyhydroxyalkanoate-Nano-Clay Microcarriers Loaded with r-BMSCs Enhance the Repair of Cranial Defects in Rats

Purpose

Successful regeneration of cranial defects necessitates the use of porous bone fillers to facilitate cell proliferation and nutrient diffusion. Open porous microspheres, characterized by their high specific surface area and osteo-inductive properties, offer an optimal microenvironment for cell ingrowth and efficient ossification, potentially accelerating bone regeneration.

Materials and Methods

An in vitro investigation was conducted to assess the physicochemical properties, porosity, and biocompatibility of PHA-nano-clay open porous microspheres. Subsequently, PHA-nano-clay microspheres loaded with rat bone marrow mesenchymal stem cells were implanted into 5 mm cranial defects in rats for a duration of 12 weeks and were evaluated through histological and immunohistochemical analyses.

Results

The incorporation of nano-clay into PHA resulted in improved mechanical properties of the porous scaffolds. Furthermore, cell adhesion, viability, and morphology on the scaffolds were maintained. The PHA-3% nano-clay open porous microspheres effectively enhanced the repair of cranial defects compared to the control group, without recurrence or complications.

Conclusion

Porous PHA-nano-clay microspheres, with their high specific surface area, biodegradability, and osteo-inductive properties, can be utilized as a bone-filling material for improved bone defect repair through cell delivery. In particular, PHA-3% nano-clay open porous microspheres exhibit promising therapeutic potential in the repair of cranial defects.

3D Biofabrication of Microporous Hydrogels for Tissue Engineering

Microporous hydrogels have been utilized in an unprecedented manner in the last few decades, combining materials science, biology, and medicine. Their microporous structure makes them suitable for wide applications, especially as cell carriers in tissue engineering and regenerative medicine. Microporous hydrogel scaffolds provide spatial and platform support for cell growth and proliferation, which can promote cell growth, migration, and differentiation, influencing tissue repair and regeneration. This review gives an overview of recent developments in the fabrication techniques and applications of microporous hydrogels. The fabrication of microporous hydrogels can be classified into two distinct categories: fabrication of non-injectable microporous hydrogels including freeze-drying microporous method, two-phase sacrificial strategy, 3D biofabrication technology, etc., and fabrication of injectable microporous hydrogels mainly including microgel assembly. Then, the biomedical applications of microporous hydrogels in cell carriers for tissue engineering, including but not limited to bone regeneration, nerve regeneration, vascular regeneration, and muscle regeneration are emphasized. Additionally, the ongoing and foreseeable applications and current limitations of microporous hydrogels in biomedical engineering are illustrated. Through stimulating innovative ideas, the present review paves new avenues for expanding the application of microporous hydrogels in tissue engineering.

Catechol-rich gelatin microspheres as restorative medical implants intended for inhibiting seroma formation and promoting wound healing

Seroma formation and poor wound healing are common complications of many surgeries that create anatomical dead space (i.e., mastectomy), often causing tissue infection and even necrosis. Although negative pressure drainage and tissue adhesives are investigated to alleviate fluid accumulation post-surgery, however, their therapeutic efficacy remains unsatisfactory in most cases. Herein, the catechol-rich chemically crosslinked gelatin microspheres (ca-CGMSs) have been developed as biodegradable reconstructive implants for preventing seroma formation and concurrently promoting subcutaneous wound healing. Compared with the most representative hydrogel adhesive, i.e. commercial porcine fibrin sealant (PFS), the loosely packed ca-CGMSs with diameters range from 50 to 350 μm, provide numerous cell-adhesive interfaces and interconnected macro-pores for enhanced cell adhesion, proliferation and migration. Subcutaneous embedding trials show the in situ swelling aggregation and wet tissue adhesion of ca-CGMSs as well as their capacity in recruiting autologous cells in rat mastectomy models. The trials in rabbit mastectomy models demonstrate that, compared with PFS gluing, the implanted dried ca-CGMSs not only significantly inhibit seroma formation, but also achieve enhanced wound healing by inducing the formation of vascularized neo-tissue. The ca-CGMSs show a great potential to be the next-generation of restorative materials for both preventing seroma formation and healing subcutaneous wounds.

Synergy of engineered gelatin methacrylate-based porous microspheres and multicellular assembly to promote osteogenesis and angiogenesis in bone tissue reconstruction

One of the key challenges in bone defects treatment is providing adequate and stable blood supply during new tissue regeneration. Mesenchymal stem cells (MSCs) and endothelial cells (ECs) have great potential to promote osteogenesis and angiogenesis during bone defect repair through paracrine effects, but their therapeutic efficacy depends on effective cellular assembly and delivery. In this work, we developed various microspheres with different pore sizes for multi-cellular delivery to enhance the angiogenic and osteogenic capability via combining microfluidic and gradient freeze-drying techniques. The particle and pore size of fabricated porous gelatin methacrylate (GelMA)-based hydrogel microspheres (PGMS) could be controllable through adjusting the freezing time of hydrogel microspheres, the range of particles and pores size are 150-250 μm and 10-100 μm with different freezing time from 0 min to 30 min. The optimized particle size (200.8 ± 14.2 μm) and pore size (11.2 ± 1.9 μm) were explored to promote cell assemble, adhesion, growth, and proliferation in the PGMS. Furthermore, the co-assembly and delivery of bone marrow mesenchymal stem cells (BMSCs) and human umbilical vein endothelial cells (HUVECs) on the PGMS was achieved and an optimal cellular ratio of BMSCs to HUVECs (20:2) was established for co-culturing of them to achieve optimal paracrine effects, further promoting osteogenic differentiation and angiogenesis. Finally, results from both in vitro and in vivo experiments showed that the developed PGMS with co-assembly of BMSCs to HUVECs contributed to accelerate bone regeneration and vascularization process daringly, exhibited great potential in vascularized bone tissue reconstruction.

An Innovative Delivery System of Oxygen-Releasing Nanospheres and Self-Healing Hydrogels Enhances the Therapeutic Effectiveness of Bone Marrow Mesenchymal Stem Cells for Chronic Limb-Threatening Ischemia

Purpose

Bone marrow mesenchymal stem cells (BMSCs) have emerged as promising candidate for postoperative therapeutics in chronic limb-threatening ischemia (CLTI). Nevertheless, their effectiveness is limited by their low survival rate and impaired functionality in the ischemic microenvironment. To overcome these challenges, we have devised an innovative delivery approach to support the utilization of BMSCs in CLTI therapy.

Methods

We synthesized oxygen-releasing nanospheres and self-healing hydrogels. The in vivo functionality of the hydrogel-nanosphere delivery system was evaluated via a multimodality animal live imaging system. A unilateral lower limb ischemia model was established in mice, and a delivery system loaded with BMSCs was administered. The experimental groups included normal mice, ischemic mice, ischemic mice treated with BMSCs in PBS, and ischemic mice treated with BMSCs in the delivery system. Blood perfusion was quantitatively measured via a laser doppler flowmeter (LDF). Immunofluorescence, Masson's trichrome staining, immunohistochemistry and enzyme-linked immunosorbent assay (ELISA) were also used.

Results

For cell viability analysis 80 μg.mL-1 was considered the optimal concentration for cell survival. In vivo, 18 days after injection, the cell membrane fluorescence signal in the delivery system was significantly greater (5.65510±8.2268) p/s/cm²/sr than that in the other groups (p=0.043). Ischemic mice treated with BMSCs in the delivery system presented an improved limb salvage rate (0.926±0.12)% compared with that of ischemic mice treated with BMSCs in PBS (0.841±0.029)% at the 5th week after ischemia establishment (p=0.0033).

Conclusion

Our findings suggest that the survival time of BMSCs is prolonged in this innovative delivery system. The combination of nanospheres and hydrogels effectively restored vascular blood perfusion while exerting minimal toxicity on BMSCs. This novel approach combining oxygen-releasing nanospheres and self-healing hydrogels as a delivery system represents an advancement in enhancing the functionality of BMSCs to treat CLTI.

3D Printing Hierarchical Porous Nanofibrous Scaffold for Bone Regeneration

Current limitations in 3D printing pose significant challenges for the fabrication of hierarchical 3D scaffolds with nanofibrous structures that simulate the natural bone extracellular matrix (ECM) for enhanced bone regeneration. This study presents an innovative approach to 3D printing customized hierarchical porous scaffolds with nanofiber structures using biodegradable nanofibrous microspheres as the bio-ink. In vitro investigations demonstrate that the hierarchical porous architecture substantially enhances cell infiltration and proliferation rates, while the nanofiber topology provides physical cues to guide osteogenic differentiation and ECM deposition. When serving as a cell carrier, the 3D-printed nanofibrous scaffold promotes bone tissue regeneration and integration in vivo. Additionally, the facile and versatile chemical modification facilitates the precise tailoring of the scaffold's functionality. Using nanofibrous microspheres with highly biomimetic and versatile modification properties as the foundational constituent in this universal 3D printing methodology enables comprehensive manipulation of scaffolding biological properties, spanning from macroscopic external morphology to molecular-scale biochemical kinetics, thereby addressing a diverse spectrum of clinical requisites.

Human Amniotic Epithelial Stem Cells Promote Colonic Recovery in Experimental Colitis via Exosomal MiR-23a-TNFR1-NF-κB Signaling

Inflammatory bowel disease (IBD), including ulcerative colitis and Crohn's disease, manifests as chronic intestinal inflammation with debilitating symptoms, posing a significant burden on global healthcare. Moreover, current therapies primarily targeting inflammation can lead to immunosuppression-related complications. Human amniotic epithelial stem cells (hAESCs), which exhibit low immunogenicity and ethical acceptability, have gained attention as potential therapeutics. In this study, it is demonstrated that their encapsulation in a hydrogel and administration via anal injection enhanced the colonic mucosal barrier repair in a murine colitis model induced by dextran sodium sulfate during the recovery phase. The underlying mechanism involved the release of exosomes from hAESCs enriched with microRNA-23a-3p, which post-transcriptionally reduced tumor necrosis factor receptor 1 expression, suppressing the nuclear factor-κB pathway in colonic epithelial cells, thus played a key role in inflammation. The novel approach shows potential for IBD treatment by restoring intestinal epithelial homeostasis without the immunosuppressive therapy-associated risks. Furthermore, the approach provides an alternative strategy to target the key molecular pathways involved in inflammation and promotes intestinal barrier function using hAESCs and their secreted exosomes. Overall, this study provides key insights to effectively treat IBD, addresses the unmet needs of patients, and reduces related healthcare burden.

Gelatin Methacrylic Acid Hydrogel-Based Nerve Growth Factors Enhances Neural Stem Cell Growth and Differentiation to Promote Repair of Spinal Cord Injury

Background

The challenge in treating irreversible nerve tissue damage has resulted in suboptimal outcomes for spinal cord injuries (SCI), underscoring the critical need for innovative treatment strategies to offer hope to patients.

Methods

In this study, gelatin methacrylic acid hydrogel scaffolds loaded with nerve growth factors (GMNF) were prepared and used to verify the performance of SCI. The physicochemical and biological properties of the GMNF were tested. The effect of GMNF on activity of neuronal progenitor cells (NPCs) was investigated in vitro. Histological staining and motor ability was carried out to assess the ability of SCI repair in SCI animal models.

Results

Achieving nerve growth factors sustained release, GMNF had good biocompatibility and could effectively penetrate into the cells with good targeting permeability. GMNF could better enhance the activity of NPCs and promote their directional differentiation into mature neuronal cells in vitro, which could exert a good neural repair function. In vivo, SCI mice treated with GMNF recovered their motor abilities more effectively and showed better wound healing by macroscopic observation of the coronal surface of their SCI area. Meanwhile, the immunohistochemistry demonstrated that the GMNF scaffolds effectively promoted SCI repair by better promoting the colonization and proliferation of neural stem cells (NSCs) in the SCI region and targeted differentiation into mature neurons.

Conclusion

The application of GMNF composite scaffolds shows great potential in SCI treatment, which are anticipated to be a potential therapeutic bioactive material for clinical application in repairing SCI in the future.

Synergistic effect of Hypoxic Conditioning and Cell-Tethering Colloidal Gels enhanced Productivity of MSC Paracrine Factors and Accelerated Vessel Regeneration

Microporous hydrogels have been widely used for delivering therapeutic cells. However, several critical issues, such as the lack of control over the harsh environment they are subjected to under pathological conditions and rapid egression of cells from the hydrogels, have produced limited therapeutic outcomes. To address these critical challenges, cell-tethering and hypoxic conditioning colloidal hydrogels containing mesenchymal stem cells (MSCs) are introduced to increase the productivity of paracrine factors locally and in a long-term manner. Cell-tethering colloidal hydrogels that are composed of tyramine-conjugated gelatin prevent cells from egressing through on-cell oxidative phenolic crosslinks while providing mechanical stimulation and interconnected microporous networks to allow for host-implant interactions. Oxygenating microparticles encapsulated in tyramine-conjugated colloidal microgels continuously generated oxygen for 2 weeks with rapid diffusion, resulting in maintaining a mild hypoxic condition while MSCs consumed oxygen under severe hypoxia. Synergistically, local retention of MSCs within the mild hypoxic-conditioned and mechanically robust colloidal hydrogels significantly increased the secretion of various angiogenic cytokines and chemokines. The oxygenating colloidal hydrogels induced anti-inflammatory responses, reduced cellular apoptosis, and promoted numerous large blood vessels in vivo. Finally, mice injected with the MSC-tethered oxygenating colloidal hydrogels significantly improved blood flow restoration and muscle regeneration in a hindlimb ischemia (HLI) model.

Droplet Microfluidics Powered Hydrogel Microparticles for Stem Cell-Mediated Biomedical Applications

Stem cell-related therapeutic technologies have garnered significant attention of the research community for their multi-faceted applications. To promote the therapeutic effects of stem cells, the strategies for cell microencapsulation in hydrogel microparticles have been widely explored, as the hydrogel microparticles have the potential to facilitate oxygen diffusion and nutrient transport alongside their ability to promote crucial cell-cell and cell-matrix interactions. Despite their significant promise, there is an acute shortage of automated, standardized, and reproducible platforms to further stem cell-related research. Microfluidics offers an intriguing platform to produce stem cell-laden hydrogel microparticles (SCHMs) owing to its ability to manipulate the fluids at the micrometer scale as well as precisely control the structure and composition of microparticles. In this review, the typical biomaterials and crosslinking methods for microfluidic encapsulation of stem cells as well as the progress in droplet-based microfluidics for the fabrication of SCHMs are outlined. Moreover, the important biomedical applications of SCHMs are highlighted, including regenerative medicine, tissue engineering, scale-up production of stem cells, and microenvironmental simulation for fundamental cell studies. Overall, microfluidics holds tremendous potential for enabling the production of diverse hydrogel microparticles and is worthy for various stem cell-related biomedical applications.

Anoikis in cell fate, physiopathology, and therapeutic interventions

The extracellular matrix (ECM) governs a wide spectrum of cellular fate processes, with a particular emphasis on anoikis, an integrin-dependent form of cell death. Currently, anoikis is defined as an intrinsic apoptosis. In contrast to traditional apoptosis and necroptosis, integrin correlates ECM signaling with intracellular signaling cascades, describing the full process of anoikis. However, anoikis is frequently overlooked in physiological and pathological processes as well as traditional in vitro research models. In this review, we summarized the role of anoikis in physiological and pathological processes, spanning embryonic development, organ development, tissue repair, inflammatory responses, cardiovascular diseases, tumor metastasis, and so on. Similarly, in the realm of stem cell research focused on the functional evolution of cells, anoikis offers a potential solution to various challenges, including in vitro cell culture models, stem cell therapy, cell transplantation, and engineering applications, which are largely based on the regulation of cell fate by anoikis. More importantly, the regulatory mechanisms of anoikis based on molecular processes and ECM signaling will provide new strategies for therapeutic interventions (drug therapy and cell-based therapy) in disease. In summary, this review provides a systematic elaboration of anoikis, thus shedding light on its future research.

Biological Functions of Macromolecular Protein Hydrogels in Constructing Osteogenic Microenvironment

Irreversible bone defects resulting from trauma, infection, and degenerative illnesses have emerged as a significant health concern. Structurally and functionally controllable hydrogels made by bone tissue engineering (BTE) have become promising biomaterials. Natural proteins are able to establish connections with autologous proteins through unique biologically active regions. Hydrogels based on proteins can simulate the bone microenvironment and regulate the biological behavior of stem cells in the tissue niche, making them candidates for research related to bone regeneration. This article reviews the biological functions of various natural macromolecular proteins (such as collagen, gelatin, fibrin, and silk fibroin) and highlights their special advantages as hydrogels. Then the latest research trends on cross-linking modified macromolecular protein hydrogels with improved mechanical properties and composite hydrogels loaded with exogenous micromolecular proteins have been discussed. Finally, the applications of protein hydrogels, such as 3D printed hydrogels, microspheres, and injectable hydrogels, were introduced, aiming to provide a reference for the repair of clinical bone defects.

Injectable dual drug-loaded thermosensitive liposome-hydrogel composite scaffold for vascularised and innervated bone regeneration

Adequate blood supply and thorough innervation are essential to the survival of tissue-engineered bones. Though great progress has been created in the application of bone tissue engineering technology to bone defect repair, many challenges remain, such as insufficient vascularisation and deficient innervation in newly regenerated bone. In the present study, we addressed these challenges by manipulating the bone regeneration microenvironment in terms of vascularisation and innervation. We used a novel injectable thermosensitive liposome-hydrogel composite scaffold as a sustained-release carrier for basic fibroblast growth factor (bFGF, which promotes angiogenesis and neurogenic differentiation) and dexamethasone (Dex, which promotes osteogenic differentiation). In vitro biological assessment demonstrated that the composite scaffold had sufficient cell compatibility; it enhanced the capacity for angiogenesis in human umbilical vein endothelial cells, and the capacity for neurogenic/osteogenic differentiation in human bone marrow mesenchymal stem cells. Moreover, the introduction of bFGF/Dex liposome-hydrogel composite scaffold to bone defect sites significantly improved vascularisation and innervated bone regeneration properties in a rabbit cranial defect model. Based on our findings, the regeneration of sufficiently vascularised and innervated bone tissue through a sustained-release scaffold with excellent injectability and body temperature sensitivity represents a promising tactic towards bone defect repair.

Injectable porous microspheres for articular cartilage regeneration through in situ stem cell recruitment and macrophage polarization

In situ mesenchymal stem cells (MSCs) regenerative therapy holds promising potential for treating osteoarthritis. However, MSCs engraftment and intra-articular inflammation limit the therapeutic efficacy of this approach. This study introduces porous microspheres (PMs) composed of aldehyde-modified poly(lactic-co-glycolic acid), that encapsulate platelet derived growth factor-AB and kartogenin. Metformin (Met) is also incorporated onto the microsphere through a Schiff base reaction to create PMs@Met. In vitro, in vivo and ex experiments revealed that PMs@Met can be injected into the joint cavity, effectively recruiting endogenous MSCs in situ. This approach creates a favorable environment for MSCs proliferation. It also controls the intra-articular inflammatory environment by modulating the polarization of synovial macrophages, ultimately promoting cartilage repair. In summary, our study presents an innovative tissue engineering strategy for the treatment of osteoarthritis-induced articular cartilage injuries. STATEMENT OF SIGNIFICANCE: Cell therapy using autologous mesenchymal stem cells (MSCs) has potential to slow the progression of osteoarthritis (OA). Nonetheless, there are some disadvantages to adopting in situ MSCs therapy, including difficulties with MSC engraftment into cartilage-deficient regions, the effect of intra-articular inflammation on MSC therapeutic efficacy, and attaining selective chondrogenic MSC differentiation. We created injectable PLGA microspheres (PMs) that were loaded with PDGF-AB and KGN. Metformin was bonded to the surface of microspheres using a Schiff base reaction. The microspheres can recruit intra-articular MSCs and encourage their development into chondrocytes. The microspheres actively modulate the inflammatory joint environment by altering synovial macrophage polarization, thereby supporting MSCs in effective cartilage treatment. To summarize, microspheres hold great potential in the treatment of OA.

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

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

Endogenous Tissue Engineering for Chondral and Osteochondral Regeneration: Strategies and Mechanisms

Increasing attention has been paid to the development of effective strategies for articular cartilage (AC) and osteochondral (OC) regeneration due to their limited self-reparative capacities and the shortage of timely and appropriate clinical treatments. Traditional cell-dependent tissue engineering faces various challenges such as restricted cell sources, phenotypic alterations, and immune rejection. In contrast, endogenous tissue engineering represents a promising alternative, leveraging acellular biomaterials to guide endogenous cells to the injury site and stimulate their intrinsic regenerative potential. This review provides a comprehensive overview of recent advancements in endogenous tissue engineering strategies for AC and OC regeneration, with a focus on the tissue engineering triad comprising endogenous stem/progenitor cells (ESPCs), scaffolds, and biomolecules. Multiple types of ESPCs present within the AC and OC microenvironment, including bone marrow-derived mesenchymal stem cells (BMSCs), adipose-derived mesenchymal stem cells (AD-MSCs), synovial membrane-derived mesenchymal stem cells (SM-MSCs), and AC-derived stem/progenitor cells (CSPCs), exhibit the ability to migrate toward injury sites and demonstrate pro-regenerative properties. The fabrication and characteristics of scaffolds in various formats including hydrogels, porous sponges, electrospun fibers, particles, films, multilayer scaffolds, bioceramics, and bioglass, highlighting their suitability for AC and OC repair, are systemically summarized. Furthermore, the review emphasizes the pivotal role of biomolecules in facilitating ESPCs migration, adhesion, chondrogenesis, osteogenesis, as well as regulating inflammation, aging, and hypertrophy-critical processes for endogenous AC and OC regeneration. Insights into the applications of endogenous tissue engineering strategies for in vivo AC and OC regeneration are provided along with a discussion on future perspectives to enhance regenerative outcomes.

Emulsion-Templated Gelatin/Amino Acids/Chitosan Macroporous Hydrogels with Adjustable Internal Dimensions for Three-Dimensional Stem Cell Culture

The demand for macroporous hydrogel scaffolds with interconnected porous and open-pore structures is crucial for advancing research and development in cell culture and tissue regeneration. Existing techniques for creating 3D porous materials and controlling their porosity are currently constrained. This study introduces a novel approach for producing highly interconnected aspartic acid-gelatin macroporous hydrogels (MHs) with precisely defined open pore structures using a one-step emulsification polymerization method with surface-modified silica nanoparticles as Pickering stabilizers. Macroporous hydrogels offer adjustable pore size and pore throat size within the ranges of 50 to 130 μm and 15 to 27 μm, respectively, achieved through variations in oil-in-water ratio and solid content. The pore wall thickness of the macroporous hydrogel can be as thin as 3.37 μm and as thick as 6.7 μm. In addition, the storage modulus of the macroporous hydrogels can be as high as 7250 Pa, and it maintains an intact rate of more than 92% after being soaked in PBS for 60 days, which is also good performance for use as a biomedical scaffold material. These hydrogels supported the proliferation of human dental pulp stem cells (hDPSCs) over a 30 day incubation period, stretching the cell morphology and demonstrating excellent biocompatibility and cell adhesion. The combination of these desirable attributes makes them highly promising for applications in stem cell culture and tissue regeneration, underscoring their potential significance in advancing these fields.

Polysaccharide-protein based scaffolds for cartilage repair and regeneration

Cartilage repair and regeneration have become a global issue that millions of patients from all over the world need surgical intervention to repair the articular cartilage annually due to the limited self-healing capability of the cartilage tissues. Cartilage tissue engineering has gained significant attention in cartilage repair and regeneration by integration of the chondrocytes (or stem cells) and the artificial scaffolds. Recently, polysaccharide-protein based scaffolds have demonstrated unique and promising mechanical and biological properties as the artificial extracellular matrix of natural cartilage. In this review, we summarize the modification methods for polysaccharides and proteins. The preparation strategies for the polysaccharide-protein based hydrogel scaffolds are presented. We discuss the mechanical, physical and biological properties of the polysaccharide-protein based scaffolds. Potential clinical translation and challenges on the artificial scaffolds are also discussed.

Extracellular Vesicles Functional “Brick‐Cement” Bio‐Integrated System for Annulus Fibrosus Repair

Due to the deficiency of mechanical supporting after discectomy and weak proliferative capacity of annulus fibrosus (AF) cells, the AF defect repair remains a clinical challenge. Herein, a myofibroblasts derived extracellular vesicles (M‐EVs) functional “brick‐cement” bio‐integrated system (M‐EVs@PGBgel) is developed to repair AF defect. The modified Poly(glycerol‐sebacate) (PGBS), “bio‐brick” layer, exhibited excellent support features on account of its elastomeric mechanical properties. The loaded M‐EVs in the “bio‐cement” layer activated ITGA6/PI3K/AKT pathway, regulated M2 macrophage polarization, thus synergistically promoting AF cell proliferation and migration. The “bio‐cement” layer integrated PGBS and remnant tissue at the defect through the Schiff base reaction and aided M‐EVs’ sustained release. This study demonstrated that M‐EVs@PGBgel significantly improved the disc's biological and mechanical properties in the AF defect microenvironments and promoted AF regeneration in vivo. The M‐EVs@PGBgel shows promise as an effective strategy to simultaneously address the mechanical imbalance and biological disruptions resulting from AF defect.

Harnessing the potential of hydrogels for advanced therapeutic applications: current achievements and future directions

The applications of hydrogels have expanded significantly due to their versatile, highly tunable properties and breakthroughs in biomaterial technologies. In this review, we cover the major achievements and the potential of hydrogels in therapeutic applications, focusing primarily on two areas: emerging cell-based therapies and promising non-cell therapeutic modalities. Within the context of cell therapy, we discuss the capacity of hydrogels to overcome the existing translational challenges faced by mainstream cell therapy paradigms, provide a detailed discussion on the advantages and principal design considerations of hydrogels for boosting the efficacy of cell therapy, as well as list specific examples of their applications in different disease scenarios. We then explore the potential of hydrogels in drug delivery, physical intervention therapies, and other non-cell therapeutic areas (e.g., bioadhesives, artificial tissues, and biosensors), emphasizing their utility beyond mere delivery vehicles. Additionally, we complement our discussion on the latest progress and challenges in the clinical application of hydrogels and outline future research directions, particularly in terms of integration with advanced biomanufacturing technologies. This review aims to present a comprehensive view and critical insights into the design and selection of hydrogels for both cell therapy and non-cell therapies, tailored to meet the therapeutic requirements of diverse diseases and situations.

Unveiling the versatility of gelatin methacryloyl hydrogels: a comprehensive journey into biomedical applications

Gelatin methacryloyl (GelMA) hydrogels have gained significant recognition as versatile biomaterials in the biomedical domain. GelMA hydrogels emulate vital characteristics of the innate extracellular matrix by integrating cell-adhering and matrix metalloproteinase-responsive peptide motifs. These features enable cellular proliferation and spreading within GelMA-based hydrogel scaffolds. Moreover, GelMA displays flexibility in processing, as it experiences crosslinking when exposed to light irradiation, supporting the development of hydrogels with adjustable mechanical characteristics. The drug delivery landscape has been reshaped by GelMA hydrogels, offering a favorable platform for the controlled and sustained release of therapeutic actives. The tunable physicochemical characteristics of GelMA enable precise modulation of the kinetics of drug release, ensuring optimal therapeutic effectiveness. In tissue engineering, GelMA hydrogels perform an essential role in the design of the scaffold, providing a biomimetic environment conducive to cell adhesion, proliferation, and differentiation. Incorporating GelMA in three-dimensional printing further improves its applicability in drug delivery and developing complicated tissue constructs with spatial precision. Wound healing applications showcase GelMA hydrogels as bioactive dressings, fostering a conducive microenvironment for tissue regeneration. The inherent biocompatibility and tunable mechanical characteristics of GelMA provide its efficiency in the closure of wounds and tissue repair. GelMA hydrogels stand at the forefront of biomedical innovation, offering a versatile platform for addressing diverse challenges in drug delivery, tissue engineering, and wound healing. This review provides a comprehensive overview, fostering an in-depth understanding of GelMA hydrogel's potential impact on progressing biomedical sciences.

Innovative Bio-based Hydrogel Microspheres Micro-Cage for Neutrophil Extracellular Traps Scavenging in Diabetic Wound Healing

Neutrophil extracellular traps (NETs) seriously impede diabetic wound healing. The disruption or scavenging of NETs using deoxyribonuclease (DNase) or cationic nanoparticles has been limited by liberating trapped bacteria, short half-life, or potential cytotoxicity. In this study, a positive correlation between the NETs level in diabetic wound exudation and the severity of wound inflammation in diabetic patients is established. Novel NETs scavenging bio-based hydrogel microspheres 'micro-cage', termed mPDA-PEI@GelMA, is engineered by integrating methylacrylyl gelatin (GelMA) hydrogel microspheres with cationic polyethyleneimine (PEI)-functionalized mesoporous polydopamine (mPDA). This unique 'micro-cage' construct is designed to non-contact scavenge of NETs between nanoparticles and the diabetic wound surface, minimizing biological toxicity and ensuring high biosafety. NETs are introduced into 'micro-cage' along with wound exudation, and cationic mPDA-PEI immobilizes them inside the 'micro-cage' through a strong binding affinity to the cfDNA web structure. The findings demonstrate that mPDA-PEI@GelMA effectively mitigates pro-inflammatory responses associated with diabetic wounds by scavenging NETs both in vivo and in vitro. This work introduces a novel nanoparticle non-contact NETs scavenging strategy to enhance diabetic wound healing processes, with potential benefits in clinical applications.

Dynamic monitoring soft tissue healing via visualized Gd-crosslinked double network MRI microspheres

By integrating magnetic resonance-visible components with scaffold materials, hydrogel microspheres (HMs) become visible under magnetic resonance imaging(MRI), allowing for non-invasive, continuous, and dynamic monitoring of the distribution, degradation, and relationship of the HMs with local tissues. However, when these visualization components are physically blended into the HMs, it reduces their relaxation rate and specificity under MRI, weakening the efficacy of real-time dynamic monitoring. To achieve MRI-guided in vivo monitoring of HMs with tissue repair functionality, we utilized airflow control and photo-crosslinking methods to prepare alginate-gelatin-based dual-network hydrogel microspheres (G-AlgMA HMs) using gadolinium ions (Gd (III)), a paramagnetic MRI contrast agent, as the crosslinker. When the network of G-AlgMA HMs degrades, the cleavage of covalent bonds causes the release of Gd (III), continuously altering the arrangement and movement characteristics of surrounding water molecules. This change in local transverse and longitudinal relaxation times results in variations in MRI signal values, thus enabling MRI-guided in vivo monitoring of the HMs. Additionally, in vivo data show that the degradation and release of polypeptide (K2 (SL)6 K2 (KK)) from G-AlgMA HMs promote local vascular regeneration and soft tissue repair. Overall, G-AlgMA HMs enable non-invasive, dynamic in vivo monitoring of biomaterial degradation and tissue regeneration through MRI, which is significant for understanding material degradation mechanisms, evaluating biocompatibility, and optimizing material design.

Boosting cartilage repair with silk fibroin-DNA hydrogel-based cartilage organoid precursor

Osteoarthritis (OA), a common degenerative disease, is characterized by high disability and imposes substantial economic impacts on individuals and society. Current clinical treatments remain inadequate for effectively managing OA. Organoids, miniature 3D tissue structures from directed differentiation of stem or progenitor cells, mimic native organ structures and functions. They are useful for drug testing and serve as active grafts for organ repair. However, organoid construction requires extracellular matrix-like 3D scaffolds for cellular growth. Hydrogel microspheres, with tunable physical and chemical properties, show promise in cartilage tissue engineering by replicating the natural microenvironment. Building on prior work on SF-DNA dual-network hydrogels for cartilage regeneration, we developed a novel RGD-SF-DNA hydrogel microsphere (RSD-MS) via a microfluidic system by integrating photopolymerization with self-assembly techniques and then modified with Pep-RGDfKA. The RSD-MSs exhibited uniform size, porous surface, and optimal swelling and degradation properties. In vitro studies demonstrated that RSD-MSs enhanced bone marrow mesenchymal stem cells (BMSCs) proliferation, adhesion, and chondrogenic differentiation. Transcriptomic analysis showed RSD-MSs induced chondrogenesis mainly through integrin-mediated adhesion pathways and glycosaminoglycan biosynthesis. Moreover, in vivo studies showed that seeding BMSCs onto RSD-MSs to create cartilage organoid precursors (COPs) significantly enhanced cartilage regeneration. In conclusion, RSD-MS was an ideal candidate for the construction and long-term cultivation of cartilage organoids, offering an innovative strategy and material choice for cartilage regeneration and tissue engineering.

Cyaonoside A-loaded composite hydrogel microspheres to treat osteoarthritis by relieving chondrocyte inflammation

Cyaonoside A (CyA), derived from the natural Chinese medicine, Cyathula officinalis Kuan, which was for a long time used to treat knee injuries and relieve joint pain in traditional Chinese medicine, showed an unclear mechanism for protecting cartilage. In addition, CyA was poorly hydrosoluble and incapable of being injected directly into the joint cavity, which limited its clinical application. This study reveals that CyA resisted IL-1β-mediated chondrogenic inflammation and apoptosis. Next, transcriptome sequencing is used to explore the potential mechanisms underlying CyA regulation of MSC chondrogenic differentiation. Based on these findings, CyA-loaded composite hydrogel microspheres (HLC) were developed and they possessed satisfactory loading efficiency, a suitable degradation rate and good biocompatibility. HLC increased chondrogenic anabolic gene (Acan, COL2A, and SOX9) expression, while downregulating the expression of the catabolic marker MMP13 in vitro. In the osteoarthritis mouse model, HLC demonstrated promising therapeutic capabilities by protecting the integrity of articular cartilage. In conclusion, this study provides insights into the regulatory mechanisms of CyA for chondrocytes and proposes a composite hydrogel microsphere-based advanced therapeutic strategy for osteoarthritis.

Applications of Hydrogels in Osteoarthritis Treatment

This review critically evaluates advancements in multifunctional hydrogels, particularly focusing on their applications in osteoarthritis (OA) therapy. As research evolves from traditional natural materials, there is a significant shift towards synthetic and composite hydrogels, known for their superior mechanical properties and enhanced biodegradability. This review spotlights novel applications such as injectable hydrogels, microneedle technology, and responsive hydrogels, which have revolutionized OA treatment through targeted and efficient therapeutic delivery. Moreover, it discusses innovative hydrogel materials, including protein-based and superlubricating hydrogels, for their potential to reduce joint friction and inflammation. The integration of bioactive compounds within hydrogels to augment therapeutic efficacy is also examined. Furthermore, the review anticipates continued technological advancements and a deeper understanding of hydrogel-based OA therapies. It emphasizes the potential of hydrogels to provide tailored, minimally invasive treatments, thus highlighting their critical role in advancing the dynamic field of biomaterial science for OA management.

Positioning regulation of organelle network via Chinese microneedle

The organelle network is a key factor in the repair and regeneration of lesion. However, effectively intervening in the organelle network which has complex interaction mechanisms is challenging. In this study, on the basis of electromagnetic laws, we constructed a biomaterial-based physical/chemical restraint device. This device was designed to jointly constrain electrical and biological factors in a conductive screw-threaded microneedle (ST-needle) system, identifying dual positioning regulation of the organelle network. The unique physical properties of this system could accurately locate the lesion and restrict the current path to the lesion cells through electromagnetic laws, and dynamic Van der Waals forces were activated to release functionalized hydrogel microspheres. Subsequently, the mitochondria-endoplasmic reticulum (ER) complex was synergistically targeted by increasing mitochondrial ATP supply to the ER via electrical stimulation and by blocking calcium current from the ER to the mitochondria using microspheres, and then the life activity of the lesion cells was effectively restored.

Remodelers of the vascular microenvironment: The effect of biopolymeric hydrogels on vascular diseases

Vascular disease is the leading health problem worldwide. Vascular microenvironment encompasses diverse cell types, including those within the vascular wall, blood cells, stromal cells, and immune cells. Initiation of the inflammatory state of the vascular microenvironment and changes in its mechanics can profoundly affect vascular homeostasis. Biomedical materials play a crucial role in modern medicine, hydrogels, characterized by their high-water content, have been increasingly utilized as a three-dimensional interaction network. In recent times, the remarkable progress in utilizing hydrogels and understanding vascular microenvironment have enabled the treatment of vascular diseases. In this review, we give an emphasis on the utilization of hydrogels and their advantages in the various vascular diseases including atherosclerosis, aneurysm, vascular ulcers of the lower limbs and myocardial infarction. Further, we highlight the importance and advantages of hydrogels as artificial microenvironments.

Essential elements for spatiotemporal delivery of growth factors within bio-scaffolds: A comprehensive strategy for enhanced tissue regeneration

The precise delivery of growth factors (GFs) in regenerative medicine is crucial for effective tissue regeneration and wound repair. However, challenges in achieving controlled release, such as limited half-life, potential overdosing risks, and delivery control complexities, currently hinder their clinical implementation. Despite the plethora of studies endeavoring to accomplish effective loading and gradual release of GFs through diverse delivery methods, the nuanced control of spatial and temporal delivery still needs to be elucidated. In response to this pressing clinical imperative, our review predominantly focuses on explaining the prevalent strategies employed for spatiotemporal delivery of GFs over the past five years. This review will systematically summarize critical aspects of spatiotemporal GFs delivery, including judicious bio-scaffold selection, innovative loading techniques, optimization of GFs activity retention, and stimulating responsive release mechanisms. It aims to identify the persisting challenges in spatiotemporal GFs delivery strategies and offer an insightful outlook on their future development. The ultimate objective is to provide an invaluable reference for advancing regenerative medicine and tissue engineering applications.

Capturing cerium ions via hydrogel microspheres promotes vascularization for bone regeneration

The rational design of multifunctional biomaterials with hierarchical porous structure and on-demand biological activity is of great consequence for bone tissue engineering (BTE) in the contemporary world. The advanced combination of trace element cerium ions (Ce3+) with bone repair materials makes the composite material capable of promoting angiogenesis and enhancing osteoblast activity. Herein, a living and phosphorylated injectable porous hydrogel microsphere (P-GelMA-Ce@BMSCs) is constructed by microfluidic technology and coordination reaction with metal ion ligands while loaded with exogenous BMSCs. Exogenous stem cells can adhere to and proliferate on hydrogel microspheres, thus promoting cell-extracellular matrix (ECM) and cell-cell interactions. The active ingredient Ce3+ promotes the proliferation, osteogenic differentiation of rat BMSCs, and angiogenesis of endotheliocytes by promoting mineral deposition, osteogenic gene expression, and VEGF secretion. The enhancement of osteogenesis and improvement of angiogenesis of the P-GelMA-Ce scaffold is mainly associated with the activation of the Wnt/β-catenin pathway. This study could provide novel and meaningful insights for treating bone defects with biofunctional materials on the basis of metal ions.

A double-network porous hydrogel based on high internal phase emulsions as a vehicle for potassium sucrose octasulfate delivery accelerates diabetic wound healing

Diabetic wounds are a difficult medical challenge. Excessive secretion of matrix metalloproteinase-9 (MMP-9) in diabetic wounds further degrades the extracellular matrix and growth factors and causes severe vascular damage, which seriously hinders diabetic wound healing. To solve these issues, a double-network porous hydrogel composed of poly (methyl methacrylate-co-acrylamide) (p(MMA-co-AM)) and polyvinyl alcohol (PVA) was constructed by the high internal phase emulsion (HIPE) technique for the delivery of potassium sucrose octasulfate (PSO), a drug that can inhibit MMPs, increase angiogenesis and improve microcirculation. The hydrogel possessed a typical polyHIPE hierarchical microstructure with interconnected porous morphologies, high porosity, high specific surface area, excellent mechanical properties and suitable swelling properties. Meanwhile, the p(MMA-co-AM)/PVA@PSO hydrogel showed high drug-loading performance and effective PSO release. In addition, both in vitro and in vivo studies showed that the p(MMA-co-AM)/PVA@PSO hydrogel had good biocompatibility and significantly accelerated diabetic wound healing by inhibiting excessive MMP-9 in diabetic wounds, increasing growth factor secretion, improving vascularization, increasing collagen deposition and promoting re-epithelialization. Therefore, this study provided a reliable therapeutic strategy for diabetic wound healing, some theoretical basis and new insights for the rational design and preparation of wound hydrogel dressings with high porosity, high drug-loading performance and excellent mechanical properties.

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

Osteoarthritis (OA) is a degenerative disease caused by a variety of factors with joint pain as the main symptom, including fibrosis, chapping, ulcers, and loss of cartilage. Traditional treatment can only delay the progression of OA, and classical delivery system have many side effects. In recent years, microspheres have shown great application prospects in the field of OA treatment. Microspheres can support cells, reproduce the natural tissue microenvironment in vitro and in vivo, and are an efficient delivery system for the release of drugs or biological agents, which can promote cell proliferation, migration, and differentiation. Thus, they have been widely used in cartilage repair and regeneration. In this review, preparation processes, basic materials, and functional characteristics of various microspheres commonly used in OA treatment are systematically reviewed. Then it is introduced surface modification strategies that can improve the biological properties of microspheres and discussed a series of applications of microsphere functionalized scaffolds in OA treatment. Finally, based on bibliometrics research, the research development, future potential, and possible research hotspots of microspheres in the field of OA therapy is systematically and dynamically evaluated. The comprehensive and systematic review will bring new understanding to the field of microsphere treatment of OA.

Hydrogen Ion Capturing Hydrogel Microspheres for Reversing Inflammaging

Inflammaging is deeply involved in aging-related diseases and can be destructive during aging. The maintenance of pH balance in the extracellular microenvironment can alleviate inflammaging and repair aging-related tissue damage. In this study, the hydrogen ion capturing hydrogel microsphere (GMNP) composed of mineralized transforming growth factor-β (TGF-β) and catalase (CAT) nanoparticles is developed via biomimetic mineralization and microfluidic technology for blocking the NLRP3 cascade axis in inflammaging. This GMNP can neutralize the acidic microenvironment by capturing excess hydrogen ions through the calcium carbonate mineralization layer. Then, the subsequent release of encapsulated TGF-β and CAT can eliminate both endogenous and exogenous stimulus of NLRP3, thus suppressing the excessive activation of inflammaging. In vitro, GMNP can suppress the excessive activation of the TXNIP/NLRP3/IL-1β cascade axis and enhance extracellular matrix (ECM) synthesis in nucleus pulposus cells. In vivo, GMNP becomes a sustainable and stable niche with microspheres as the core to inhibit inflammaging and promote the regeneration of degenerated intervertebral discs. Therefore, this hydrogen ion-capturing hydrogel microsphere effectively reverses inflammaging by interfering with the excessive activation of NLRP3 in the degenerated tissues.

Mitochondrial-Oriented Injectable Hydrogel Microspheres Maintain Homeostasis of Chondrocyte Metabolism to Promote Subcellular Therapy in Osteoarthritis

Subcellular mitochondria serve as sensors for energy metabolism and redox balance, and the dynamic regulation of functional and dysfunctional mitochondria plays a crucial role in determining cells' fate. Selective removal of dysfunctional mitochondria at the subcellular level can provide chondrocytes with energy to prevent degeneration, thereby treating osteoarthritis. Herein, to achieve an ideal subcellular therapy, cartilage affinity peptide (WYRGRL)-decorated liposomes loaded with mitophagy activator (urolithin A) were integrated into hyaluronic acid methacrylate hydrogel microspheres through microfluidic technology, named HM@WY-Lip/UA, that could efficiently target chondrocytes and selectively remove subcellular dysfunctional mitochondria. As a result, this system demonstrated an advantage in mitochondria function restoration, reactive oxygen species scavenging, cell survival rescue, and chondrocyte homeostasis maintenance through increasing mitophagy. In a rat post-traumatic osteoarthritis model, the intra-articular injection of HM@WY-Lip/UA ameliorated cartilage matrix degradation, osteophyte formation, and subchondral bone sclerosis at 8 weeks. Overall, this study indicated that HM@WY-Lip/UA provided a protective effect on cartilage degeneration in an efficacious and clinically relevant manner, and a mitochondrial-oriented strategy has great potential in the subcellular therapy of osteoarthritis.

A click chemistry-mediated all-peptide cell printing hydrogel platform for diabetic wound healing

High glucose-induced vascular endothelial injury is a major pathological factor involved in non-healing diabetic wounds. To interrupt this pathological process, we design an all-peptide printable hydrogel platform based on highly efficient and precise one-step click chemistry of thiolated γ-polyglutamic acid, glycidyl methacrylate-conjugated γ-polyglutamic acid, and thiolated arginine-glycine-aspartate sequences. Vascular endothelial growth factor 165-overexpressed human umbilical vein endothelial cells are printed using this platform, hence fabricating a living material with high cell viability and precise cell spatial distribution control. This cell-laden hydrogel platform accelerates the diabetic wound healing of rats based on the unabated vascular endothelial growth factor 165 release, which promotes angiogenesis and alleviates damages on vascular endothelial mitochondria, thereby reducing tissue hypoxia, downregulating inflammation, and facilitating extracellular matrix remodeling. Together, this study offers a promising strategy for fabricating tissue-friendly, high-efficient, and accurate 3D printed all-peptide hydrogel platform for cell delivery and self-renewable growth factor therapy.

Polymeric biomaterials: Advanced drug delivery systems in osteoarthritis treatment

Polymeric biomaterials have emerged as a highly promising candidate for drug delivery systems (DDS), exhibiting significant potential to enhance the therapeutic landscape of osteoarthritis (OA) therapy. Their remarkable capacity to manifest desirable physicochemical attributes, coupled with their excellent biocompatibility and biodegradability, has greatly expanded their utility in pharmacotherapeutic applications. Nevertheless, an urgent necessity exists for a comprehensive synthesis of the most recent advances in polymeric DDS, providing valuable guidance for their implementation in the context of OA therapy. This review is dedicated to summarizing and examining recent developments in the utilization of polymeric DDS for OA therapy. Initially, we present an overview of the intricate pathophysiology characterizing OA and underscore the prevailing limitations inherent to current treatment modalities. Subsequently, we introduce diverse categories of polymeric DDS, including hydrogels, nanofibers, and microspheres, elucidating their inherent advantages and limitations. Moreover, we discuss and summarize the delivery of bioactive agents through polymeric biomaterials for OA therapy, emphasizing key findings and emerging trends. Finally, we highlight prospective directions for advancing polymeric DDS, offering a promising approach to enhance their translational potential for OA therapy.

Extracellular Matrix-Mimetic Immunomodulatory Hydrogel for Accelerating Wound Healing

Macrophages play a crucial role in the complete processes of tissue repair and regeneration, and the activation of M2 polarization is an effective approach to provide a pro-regenerative immune microenvironment. Natural extracellular matrix (ECM) has the capability to modulate macrophage activities via its molecular, physical, and mechanical properties. Inspired by this, an ECM-mimetic hydrogel strategy to modulate macrophages via its dynamic structural characteristics and bioactive cell adhesion sites is proposed. The LZM-SC/SS hydrogel is in situ formed through the amidation reaction between lysozyme (LZM), 4-arm-PEG-SC, and 4-arm-PEG-SS, where LZM provides DGR tripeptide for cell adhesion, 4-arm-PEG-SS provides succinyl ester for dynamic hydrolysis, and 4-arm-PEG-SC balances the stability and dynamics of the network. In vitro and subcutaneous tests indicate the dynamic structural evolution and cell adhesion capacity promotes macrophage movement and M2 polarization synergistically. Comprehensive bioinformatic analysis further confirms the immunomodulatory ability, and reveals a significant correlation between M2 polarization and cell adhesion. A full-thickness wound model is employed to validate the induced M2 polarization, vessel development, and accelerated healing by LZM-SC/SS. This study represents a pioneering exploration of macrophage modulation by biomaterials' structures and components rather than drug or cytokines and provides new strategies to promote tissue repair and regeneration.

Engineered biomimetic micro/nano-materials for tissue regeneration

The incidence of tissue and organ damage caused by various diseases is increasing worldwide. Tissue engineering is a promising strategy of tackling this problem because of its potential to regenerate or replace damaged tissues and organs. The biochemical and biophysical cues of biomaterials can stimulate and induce biological activities such as cell adhesion, proliferation and differentiation, and ultimately achieve tissue repair and regeneration. Micro/nano materials are a special type of biomaterial that can mimic the microstructure of tissues on a microscopic scale due to its precise construction, further providing scaffolds with specific three-dimensional structures to guide the activities of cells. The study and application of biomimetic micro/nano-materials have greatly promoted the development of tissue engineering. This review aims to provide an overview of the different types of micro/nanomaterials, their preparation methods and their application in tissue regeneration.

Injectable and Degradable POSS-Polyphosphate-Polysaccharide Hybrid Hydrogel Scaffold for Cartilage Regeneration

The limited self-repair capacity of articular cartilage has motivated the development of stem cell therapy based on artificial scaffolds that mimic the extracellular matrix (ECM) of cartilage tissue. In view of the specificity of articular cartilage, desirable tissue adhesiveness and stable mechanical properties under cyclic mechanical loads are critical for cartilage scaffolds. Herein, we developed an injectable and degradable organic-inorganic hybrid hydrogel as a cartilage scaffold based on polyhedral oligomeric silsesquioxane (POSS)-cored polyphosphate and polysaccharide. Specifically, acrylated 8-arm star-shaped POSS-poly(ethyl ethylene phosphate) (POSS-8PEEP-AC) was synthesized and cross-linked with thiolated hyaluronic acid (HA-SH) to form a degradable POSS-PEEP/HA hydrogel. Incorporation of POSS in the hydrogel increased the mechanical properties. The POSS-PEEP/HA hydrogel showed enzymatic biodegradability and favorable biocompatibility, supporting the growth and differentiation of human mesenchymal stem cells (hMSCs). The chondrogenic differentiation of encapsulated hMSCs was promoted by loading transforming growth factor-β₃ (TGF-β₃) in the hydrogel. In addition, the injectable POSS-PEEP/HA hydrogel was capable of adhering to rat cartilage tissue and resisting cyclic compression. Furthermore, in vivo results revealed that the transplanted hMSCs encapsulated in the POSS-PEEP/HA hydrogel scaffold significantly improved cartilage regeneration in rats, while the conjugation of TGF-β₃ achieved a better therapeutic effect. The present work demonstrated the potential of the injectable, biodegradable, and mechanically enhanced POSS-PEEP/HA hybrid hydrogel as a scaffold biomaterial for cartilage regeneration.

Porous Structural Microfluidic Device for Biomedical Diagnosis: A Review

Microfluidics has recently received more and more attention in applications such as biomedical, chemical and medicine. With the development of microelectronics technology as well as material science in recent years, microfluidic devices have made great progress. Porous structures as a discontinuous medium in which the special flow phenomena of fluids lead to their potential and special applications in microfluidics offer a unique way to develop completely new microfluidic chips. In this article, we firstly introduce the fabrication methods for porous structures of different materials. Then, the physical effects of microfluid flow in porous media and their related physical models are discussed. Finally, the state-of-the-art porous microfluidic chips and their applications in biomedicine are summarized, and we present the current problems and future directions in this field.