Transforming growth factor-β1 (TGF-β1)-stimulated fibroblast to myofibroblast differentiation is mediated by hyaluronan (HA)-facilitated epidermal growth factor receptor (EGFR) and CD44 co-localization in lipid rafts

Fibroblast to myofibroblast differentiation drives effective wound healing and is largely regulated by the cytokine transforming growth factor-β1 (TGF-β1). Myofibroblasts express α-smooth muscle actin and are present in granulation tissue, where they are responsible for wound contraction. Our previous studies show that fibroblast differentiation in response to TGF-β1 is dependent on and mediated by the linear polysaccharide hyaluronan (HA). Both the HA receptor, CD44, and the epidermal growth factor receptor (EGFR) are involved in this differentiation response. The aim of this study was to understand the mechanisms linking HA-, CD44-, and EGFR-regulated TGF-β1-dependent differentiation. CD44 and EGFR co-localization within membrane-bound lipid rafts was necessary for differentiation, and this triggered downstream mitogen-activated protein kinase (MAPK/ERK) and Ca(2+)/calmodulin kinase II (CaMKII) activation. We also found that ERK phosphorylation was upstream of CaMKII phosphorylation, that ERK activation was necessary for CaMKII signaling, and that both kinases were essential for differentiation. In addition, HA synthase-2 (HAS2) siRNA attenuated both ERK and CaMKII signaling and sequestration of CD44 into lipid rafts, preventing differentiation. In summary, the data suggest that HAS2-dependent production of HA facilitates TGF-β1-dependent fibroblast differentiation through promoting CD44 interaction with EGFR held within membrane-bound lipid rafts. This induces MAPK/ERK, followed by CaMKII activation, leading to differentiation. This pathway is synergistic with the classical TGF-β1-dependent SMAD-signaling pathway and may provide a novel opportunity for intervention in wound healing.

In vivo engineered extracellular matrix scaffolds with instructive niches for oriented tissue regeneration

Implanted scaffolds with inductive niches can facilitate the recruitment and differentiation of host cells, thereby enhancing endogenous tissue regeneration. Extracellular matrix (ECM) scaffolds derived from cultured cells or natural tissues exhibit superior biocompatibility and trigger favourable immune responses. However, the lack of hierarchical porous structure fails to provide cells with guidance cues for directional migration and spatial organization, and consequently limit the morpho-functional integration for oriented tissues. Here, we engineer ECM scaffolds with parallel microchannels (ECM-C) by subcutaneous implantation of sacrificial templates, followed by template removal and decellularization. The advantages of such ECM-C scaffolds are evidenced by close regulation of in vitro cell activities, and enhanced cell infiltration and vascularization upon in vivo implantation. We demonstrate the versatility and flexibility of these scaffolds by regenerating vascularized and innervated neo-muscle, vascularized neo-nerve and pulsatile neo-artery with functional integration. This strategy has potential to yield inducible biomaterials with applications across tissue engineering and regenerative medicine.

Supramolecular Nanofibers Containing Arginine-Glycine-Aspartate (RGD) Peptides Boost Therapeutic Efficacy of Extracellular Vesicles in Kidney Repair

Extracellular vesicles (EVs) derived from mesenchymal stem cells (MSC-EVs) have been recognized as a promising cell-free therapy for acute kidney injury (AKI), which avoids safety concerns associated with direct cell engraftment. However, low stability and retention of MSC-EVs have limited their therapeutic efficacy. RGD (Arg-Gly-Asp) peptide binds strongly to integrins, which have been identified on the surface of MSC-EV membranes; yet RGD has not been applied to EV scaffolds to enhance and prolong bioavailability. Here, we developed RGD hydrogels, which we hypothesized could augment MSC-EV efficacy in the treatment of AKI models. In vivo tracking of the labeled EVs revealed that RGD hydrogels increased retention and stability of EVs. Integrin gene knockdown experiments confirmed that EV-hydrogel interaction was mediated by RGD-integrin binding. Upon intrarenal injection into mouse AKI models, EV-RGD hydrogels provided superior rescuing effects to renal function, attenuated histopathological damage, decreased tubular injury, and promoted cell proliferation in early phases of AKI. RGD hydrogels also augmented antifibrotic effects of MSC-EVs in chronic stages. Further analysis revealed that the presence of microRNA let-7a-5p in MSC-EVs served as the mechanism contributing to the reduced cell apoptosis and elevated cell autophagy in AKI. In conclusion, RGD hydrogels facilitated MSC-derived let-7a-5p-containing EVs, improving reparative potential against AKI. This study developed an RGD scaffold to increase the EV integrin-mediated loading and in turn improved therapeutic efficacy in renal repair; therefore this strategy shed light on MSC-EV application as a cell-free treatment for potentiated efficiency.

Myofibroblasts: Function, Formation, and Scope of Molecular Therapies for Skin Fibrosis

Myofibroblasts are contractile, α-smooth muscle actin-positive cells with multiple roles in pathophysiological processes. Myofibroblasts mediate wound contractions, but their persistent presence in tissues is central to driving fibrosis, making them attractive cell targets for the development of therapeutic treatments. However, due to shared cellular markers with several other phenotypes, the specific targeting of myofibroblasts has long presented a scientific and clinical challenge. In recent years, myofibroblasts have drawn much attention among scientific research communities from multiple disciplines and specialisations. As further research uncovers the characterisations of myofibroblast formation, function, and regulation, the realisation of novel interventional routes for myofibroblasts within pathologies has emerged. The research community is approaching the means to finally target these cells, to prevent fibrosis, accelerate scarless wound healing, and attenuate associated disease-processes in clinical settings. This comprehensive review article describes the myofibroblast cell phenotype, their origins, and their diverse physiological and pathological functionality. Special attention has been given to mechanisms and molecular pathways governing myofibroblast differentiation, and updates in molecular interventions.

Biomimetic Design of Mitochondria-Targeted Hybrid Nanozymes as Superoxide Scavengers

Development of enzyme mimics for the scavenging of excessive mitochondrial superoxide (O₂ ^•- ) can serve as an effective strategy in the treatment of many diseases. Here, protein reconstruction technology and nanotechnology is taken advantage of to biomimetically create an artificial hybrid nanozyme. These nanozymes consist of ferritin-heavy-chain-based protein as the enzyme scaffold and a metal nanoparticle core as the enzyme active center. This artificial cascade nanozyme possesses superoxide dismutase- and catalase-like activities and also targets mitochondria by overcoming multiple biological barriers. Using cardiac ischemia-reperfusion animal models, the protective advantages of the hybrid nanozymes are demonstrated in vivo during mitochondrial oxidative injury and in the recovery of heart functionality following infarction via systemic delivery and localized release from adhesive hydrogels (i.e., cardiac patch), respectively. This study illustrates a de novo design strategy in the development of enzyme mimics and provides a promising therapeutic option for alleviating oxidative damage in regenerative medicine.

MSC-derived sEVs enhance patency and inhibit calcification of synthetic vascular grafts by immunomodulation in a rat model of hyperlipidemia

Vascular grafts often exhibit low patency rates in clinical settings due to the pathological environment within the patients requiring the surgery. Mesenchymal stem cell (MSC)-derived small extracellular vesicles (sEVs) have attracted increasing attention. These sEVs contain many potent signaling molecules that play important roles in tissue regeneration, such as microRNA and cytokines. In this study, a sEVs-functionalized vascular graft was developed, and in vivo performance was systematically evaluated in a rat model of hyperlipidemia. Electrospun poly (ε-caprolactone) (PCL) vascular grafts were first modified with heparin, to enhance the anti-thrombogenicity. MSC-derived sEVs were loaded onto the heparinized PCL grafts to obtain functional vascular grafts. As-prepared vascular grafts were implanted to replace a segment of rat abdominal artery (1 cm) for up to 3 months. Results showed that the incorporation of MSC-derived sEVs effectively inhibited thrombosis and calcification, thus enhancing the patency of vascular grafts. Furthermore, regeneration of the endothelium and vascular smooth muscle was markedly enhanced, as attributed to the bioactive molecules within the sEVs, including vascular endothelial growth factor (VEGF), miRNA126, and miRNA145. More importantly, MSC-derived sEVs demonstrated a robust immunomodulatory effect, that is, they induced the transition of macrophages from a pro-inflammatory and atherogenic (M1) phenotype to an anti-inflammatory and anti-osteogenic (M2c) phenotype. This phenotypic switch was confirmed in both in vitro and in vivo analyses. Taken together, these results suggest that fabrication of vascular grafts with immunomodulatory function can provide an effective approach to improve vascular performance and functionality, with translational implication in cardiovascular regenerative medicine.

An Injectable Dual-Function Hydrogel Protects Against Myocardial Ischemia/Reperfusion Injury by Modulating ROS/NO Disequilibrium

Acute myocardial infarction (MI) is the leading cause of death worldwide. Exogenous delivery of nitric oxide (NO) to the infarcted myocardium has proven to be an effective strategy for treating MI due to the multiple physiological functions of NO. However, reperfusion of blood flow to the ischemic tissues is accompanied by the overproduction of toxic reactive oxygen species (ROS), which can further exacerbate tissue damage and compromise the therapeutic efficacy. Here, an injectable hydrogel is synthesized from the chitosan modified by boronate-protected diazeniumdiolate (CS-B-NO) that can release NO in response to ROS stimulation and thereby modulate ROS/NO disequilibrium after ischemia/reperfusion (I/R) injury. Furthermore, administration of CS-B-NO efficiently attenuated cardiac damage and adverse cardiac remodeling, promoted repair of the heart, and ameliorated cardiac function, unlike a hydrogel that only released NO, in a mouse model of myocardial I/R injury. Mechanistically, regulation of the ROS/NO balance activated the antioxidant defense system and protected against oxidative stress induced by I/R injury via adaptive regulation of the Nrf2-Keap1 pathway. Inflammation is then reduced by inhibition of the activation of NF-κB signaling. Collectively, these results show that this dual-function hydrogel may be a promising candidate for the protection of tissues and organs after I/R injury.

Nitric-Oxide-Releasing Biomaterial Regulation of the Stem Cell Microenvironment in Regenerative Medicine

Stem cell therapy has proven to be an attractive solution for the treatment of degenerative diseases or injury. However, poor cell engraftment and survival within injured tissues limits the successful use of stem cell therapy within the clinical setting. Nitric oxide (NO) is an important signaling molecule involved in various physiological processes. Emerging evidence supports NO's diverse roles in modulating stem cell behavior, including survival, migration, differentiation, and paracrine secretion of proregenerative factors. Thus, there has been a shift in research focus to concentrate efforts on the delivery of therapeutic concentration ranges of NO to the target tissue sites. Combinatory therapies utilizing biomaterials that control NO generation and support stem cell delivery can be holistic and synergistic approaches to significantly improve tissue regeneration. Here, the focus is on recent developments of various therapeutic platforms, engineered to both transport NO and to enhance stem-cell-mediated regeneration of damaged tissues. New and emerging revelations of how the stem cell microenvironment can be regulated by NO-releasing biomaterials are also highlighted.

The effect of hypoxia-mimicking responses on improving the regeneration of artificial vascular grafts

Cellular transition to hypoxia following tissue injury, has been shown to improve angiogenesis and regeneration in multiple tissues. To take advantage of this, many hypoxia-mimicking scaffolds have been prepared, yet the oxygen access state of implanted artificial small-diameter vascular grafts (SDVGs) has not been investigated. Therefore, the oxygen access state of electrospun PCL grafts implanted into rat abdominal arteries was assessed. The regions proximal to the lumen and abluminal surfaces of the graft walls were normoxic and only the interior of the graft walls was hypoxic. In light of this differential oxygen access state of the implanted grafts and the critical role of vascular regeneration on SDVG implantation success, we investigated whether modification of SDVGs with HIF-1α stabilizer dimethyloxalylglycine (DMOG) could achieve hypoxia-mimicking responses resulting in improving vascular regeneration throughout the entirety of the graft wall. Therefore, DMOG-loaded PCL grafts were fabricated by electrospinning, to support the sustained release of DMOG over two weeks. In vitro experiments indicated that DMOG-loaded PCL mats had significant biological advantages, including: promotion of human umbilical vein endothelial cells (HUVECs) proliferation, migration and production of pro-angiogenic factors; and the stimulation of M2 macrophage polarization, which in-turn promoted macrophage regulation of HUVECs migration and smooth muscle cells (SMCs) contractile phenotype. These beneficial effects were downstream of HIF-1α stabilization in HUVECs and macrophages in normoxic conditions. Our results indicated that DMOG-loaded PCL grafts improved endothelialization, contractile SMCs regeneration, vascularization and modulated the inflammatory reaction of grafts in abdominal artery replacement models, thus promoting vascular regeneration.

Hypoxia-tropic nanozymes as oxygen generators for tumor-favoring theranostics

Oxygen deficiency is the main obstacle of hypoxia-related theranostics, thus this is a considerable amount of research focusing on the development of methods to supply oxygen by taking advantage of hypoxia-responsive properties of nanoparticles. However, strategies to properly penetrate hypoxic regions by the nanoparticles remains an unmet challenge. In this work, a biomimetic nanozyme capable of possessing catalase-like activity and the efficient direct penetration of hypoxic areas in tumor tissues was developed to supply oxygen based on catalytic tumor microenvironment-responsive reaction, providing substantial tumor hypoxia relief with nearly 3-fold reduction compared to untreated tumor tissues. To demonstrate the advantages of the nanozymes in overcoming hypoxia, a theranostic nanosystem model composed of the core/shell nanozymes and aggregation-induced emission (AIE) molecules was designed. The nanosystem was able to present multi-modal imaging of tumors and modulated the tumor microenvironment for improved photodynamic therapy (PDT) by cascade reactions of therapeutic effector molecules, thereby providing significantly enhanced therapeutic benefits in inhibiting tumor growth and lung metastasis of orthotopic breast cancer. This conceptual study showed the multifaceted features of biomimetic nanozymes as tumor therapeutics and demonstrated the encouraging potential for modulating hypoxia as an application for tumor theranostics.

Prediction and Design of Nanozymes using Explainable Machine Learning

An abundant number of nanomaterials have been discovered to possess enzyme-like catalytic activity, termed nanozymes. It is identified that a variety of internal and external factors influence the catalytic activity of nanozymes. However, there is a lack of essential methodologies to uncover the hidden mechanisms between nanozyme features and enzyme-like activity. Here, a data-driven approach is demonstrated that utilizes machine-learning algorithms to understand particle-property relationships, allowing for classification and quantitative predictions of enzyme-like activity exhibited by nanozymes. High consistency between predicted outputs and the observations is confirmed by accuracy (90.6%) and R² (up to 0.80). Furthermore, sensitive analysis of the models reveals the central roles of transition metals in determining nanozyme activity. As an example, the models are successfully applied to predict or design desirable nanozymes by uncovering the hidden relationship between different periods of transition metals and their enzyme-like performance. This study offers a promising strategy to develop nanozymes with desirable catalytic activity and demonstrates the potential of machine learning within the field of material science.

Machine-learning-assisted single-vessel analysis of nanoparticle permeability in tumour vasculatures

The central dogma that nanoparticle delivery to tumours requires enhanced leakiness of vasculatures is a topic of debate. To address this, we propose a single-vessel quantitative analysis method by taking advantage of protein-based nanoprobes and image-segmentation-based machine learning (nano-ISML). Using nano-ISML, >67,000 individual blood vessels from 32 tumour models were quantified, revealing highly heterogenous vascular permeability of protein-based nanoparticles. There was a >13-fold difference in the percentage of high-permeability vessels in different tumours and >100-fold penetration ability in vessels with the highest permeability compared with vessels with the lowest permeability. Our data suggest passive extravasation and transendothelial transport were the dominant mechanisms for high- and low-permeability tumour vessels, respectively. To exemplify the nano-ISML-assisted rational design of nanomedicines, genetically tailored protein nanoparticles with improved transendothelial transport in low-permeability tumours were developed. Our study delineates the heterogeneity of tumour vascular permeability and defines a direction for the rational design of next-generation anticancer nanomedicines.

Cobalt-mediated multi-functional dressings promote bacteria-infected wound healing

Wound dressings with multiple functions are required to meet the complexity of the wound healing process. The multifunctionality often leads to an increase in the complexity and difficulty in dressing preparation. To surmount this problem, we used a facile preparation and fabrication process to fabricate a multi-functional dressing by integrating four widely accessible materials: plain gauze, sodium alginate (SA), Ca²⁺ and Co²⁺. Firstly, mixed Ca²⁺/Co²⁺ ion solutions with different concentration were applied to gauzes. After drying, SA solution was added to ionized gauze and Co²⁺-Ca²⁺/Gauze/SA (Ion-GSA) composite dressings were formed easily. In vitro results showed that all Ion-GSA dressings exhibited strong mechanical properties, uniform dispersion and sustained release of Ca²⁺ and Co²⁺, and the ability to retain moisture and absorb wound exudate. Besides the above advantages, dressings prepared with 0.25 g/L Co²⁺ and 4 g/L Ca²⁺ (Co²⁺0.25-Ca²⁺4 GSA composite dressings) exhibited the best overall effect for inducing a hypoxia-like response, and favorable cytocompatibility, hemostatic property and antibacterial activity. In vivo wound healing assays revealed that Co²⁺0.25-Ca²⁺4 GSA composite dressings inhibited bacterial growth, increased local Hypoxia-inducible factor-1α (HIF-1α), vascular endothelial growth factor (VEGF), transforming growth factor-β1 (TGF-β1) protein expression, and accelerated full-thickness skin wound healing in mouse bacterial-infected wound model. The quick healing wounds had improved angiogenesis, macrophages regulation, re-epithelialization and dense collagen deposition. Collectively, our results indicated that Co²⁺0.25-Ca²⁺4 GSA composite dressings promote wound healing. STATEMENT OF SIGNIFICANCE: Wound dressings with integrated functionalities are required to meet complex clinical requirements. However, there is often a trade-off between reducing preparation complexity and increasing the multifunctionality of the dressing's properties. In this study, we prepared multifunctional composite dressings by a facile preparation process using widely accessible materials. The composite dressings possessed the mechanical strength of gauze, had the effective wound exudate absorption, moisture maintenance and hemostatic property capacity of calcium alginate hydrogels, and had the hypoxia-like induction and the antimicrobial effects of Co²⁺. These functions all together promote bacteria-infected wound healing. Thus, we believed that the composite dressings can be widely applied in skin wound repair duo to their facile preparation method and good therapeutic effect.

Machine-Learning-Assisted Nanozyme Design: Lessons from Materials and Engineered Enzymes

Nanozymes are nanomaterials that exhibit enzyme-like biomimicry. In combination with intrinsic characteristics of nanomaterials, nanozymes have broad applicability in materials science, chemical engineering, bioengineering, biochemistry, and disease theranostics. Recently, the heterogeneity of published results has highlighted the complexity and diversity of nanozymes in terms of consistency of catalytic capacity. Machine learning (ML) shows promising potential for discovering new materials, yet it remains challenging for the design of new nanozymes based on ML approaches. Alternatively, ML is employed to promote optimization of intelligent design and application of catalytic materials and engineered enzymes. Incorporation of the successful ML algorithms used in the intelligent design of catalytic materials and engineered enzymes can concomitantly facilitate the guided development of next-generation nanozymes with desirable properties. Here, recent progress in ML, its utilization in the design of catalytic materials and enzymes, and how emergent ML applications serve as promising strategies to circumvent challenges associated with time-expensive and laborious testing in nanozyme research and development are summarized. The potential applications of successful examples of ML-aided catalytic materials and engineered enzymes in nanozyme design are also highlighted, with special focus on the unified aims in enhancing design and recapitulation of substrate selectivity and catalytic activity.

Mechanically reinforced biotubes for arterial replacement and arteriovenous grafting inspired by architectural engineering

There is a lack in clinically-suitable vascular grafts. Biotubes, prepared using in vivo tissue engineering, show potential for vascular regeneration. However, their mechanical strength is typically poor. Inspired by architectural design of steel fiber reinforcement of concrete for tunnel construction, poly(ε-caprolactone) (PCL) fiber skeletons (PSs) were fabricated by melt-spinning and heat treatment. The PSs were subcutaneously embedded to induce the assembly of host cells and extracellular matrix to obtain PS-reinforced biotubes (PBs). Heat-treated medium-fiber-angle PB (hMPB) demonstrated superior performance when evaluated by in vitro mechanical testing and following implantation in rat abdominal artery replacement models. hMPBs were further evaluated in canine peripheral arterial replacement and sheep arteriovenous graft models. Overall, hMPB demonstrated appropriate mechanics, puncture resistance, rapid hemostasis, vascular regeneration, and long-term patency, without incidence of luminal expansion or intimal hyperplasia. These optimized hMPB properties show promise as an alternatives to autologous vessels in clinical applications.

M2 Macrophage-Derived sEV Regulate Pro-Inflammatory CCR2+ Macrophage Subpopulations to Favor Post-AMI Cardiac Repair

Tissue-resident cardiac macrophage subsets mediate cardiac tissue inflammation and repair after acute myocardial infarction (AMI). CC chemokine receptor 2 (CCR2)-expressing macrophages have phenotypical similarities to M1-polarized macrophages, are pro-inflammatory, and recruit CCR2+ circulating monocytes to infarcted myocardium. Small extracellular vesicles (sEV) from CCR2̶ macrophages, which phenotypically resemble M2-polarized macrophages, promote anti-inflammatory activity and cardiac repair. Here, the authors harvested M2 macrophage-derived sEV (M2EV ) from M2-polarized bone-marrow-derived macrophages for intramyocardial injection and recapitulation of sEV-mediated anti-inflammatory activity in ischemic-reperfusion (I/R) injured hearts. Rats and pigs received sham surgery; I/R without treatment; or I/R with autologous M2EV treatment. M2EV rescued cardiac function and attenuated injury markers, infarct size, and scar size. M2EV inhibited CCR2+ macrophage numbers, reduced monocyte-derived CCR2+ macrophage recruitment to infarct sites, induced M1-to-M2 macrophage switching and promoted neovascularization. Analysis of M2EV microRNA content revealed abundant miR-181b-5p, which regulated macrophage glucose uptake, glycolysis, and mitigated mitochondrial reactive oxygen species generation. Functional blockade of miR-181b-5p is detrimental to beneficial M2EV actions and resulted in failure to inhibit CCR2+ macrophage numbers and infarct size. Taken together, this investigation showed that M2EV rescued myocardial function, improved myocardial repair, and regulated CCR2+ macrophages via miR-181b-5p-dependent mechanisms, indicating an option for cell-free therapy for AMI.

Advances in Bioactivity of MicroRNAs of Plant-Derived Exosome-Like Nanoparticles and Milk-Derived Extracellular Vesicles

MicroRNA (miRNA) is a class of small noncoding RNA involved in physiological and pathological processes via the regulation of gene expression. Naked miRNAs are unstable and liable to degradation by RNases. Exosome-like nanoparticles (ELNs) secreted by plants and extracellular vesicles (EVs) found in milk are abundant in miRNAs, which can be carried by ELNs and EVs to target cells to exert their bioactivities. In this review, we describe the current understanding of miRNAs in plant ELNs and milk EVs, summarize their important roles in regulation of inflammation, intestinal barrier, tumors, and infantile immunological functions, and also discuss the adverse effect of EV miRNAs on human health. Additionally, we prospect recent challenges centered around ELN and EV miRNAs for interventional applications and provide insights of grain-derived ELNs and miRNAs interventional use in human health. Overall, plant ELNs and milk EVs can transfer miRNAs to mitigate the pathological status of recipient cells by mediating the expression of target genes but may also exert some side effects. More studies are required to elucidate the in-depth understanding of potential interventional effects of ELN and EV miRNAs on human health.

Regulation of the inflammatory response by vascular grafts modified with Aspirin-Triggered Resolvin D1 promotes blood vessel regeneration

The unabated inflammatory response is often the cause for inhibited vascular regeneration of transplanted small-diameter vascular grafts (diameter <6 mm) in vascular replacement therapies. We proposed that stimulating inflammatory resolution could be an effective approach for treatment of chronic vascular graft inflammation after transplantation. Aspirin-Triggered Resolvin D1 (AT-RvD1) plays critical roles in driving cellular processes toward the resolution of inflammation and suppressing downstream inflammatory signaling pathways. With the aim to facilitate vascular regeneration, we developed a polycaprolactone (PCL) vascular graft loaded with AT-RvD1. The results showed that AT-RvD1 promoted macrophage polarization into M2 macrophages in vitro. Macrophages pretreated with AT-RvD1 conditioned medium promoted endothelial cell tube formation. Furthermore, in vivo implantation was performed by replacing rat abdominal aorta. We observed fast endothelialization and enhanced smooth muscle regeneration in rats that received the AT-RvD1-containing graft implants. The presence of AT-RvD1 induced infiltration of a large number of M2 macrophages and integrin α4-positive (CD49d⁺) neutrophils into the graft wall after implantation. Vascular graft RNA-Seq analysis revealed that AT-RvD1 inhibited leukocyte and neutrophil migration and activation. Results also indicated that macrophage polarization to the M2 phenotype was promoted on day 7 post-implantation. These results demonstrated the ability of locally delivered AT-RvD1 to increase pro-regenerative immune subpopulations and promote vascular tissue regeneration. STATEMENT OF SIGNIFICANCE: Chronic inflammation is a key deciding factor in the failure of vascular regeneration of transplanted small-diameter vascular grafts (diameter <6 mm). Aspirin-triggered Resolvin D1 (AT-RvD1) is a critical driving force in cellular resolution inflammation and suppresses inflammatory signaling. Herein, we developed an electrospun polycaprolactone (PCL) vascular graft loaded with AT-RvD1. In vivo implantation was performed by replacing rat abdominal aorta and AT-RvD1-loaded grafts showed rapid endothelialization, enhanced capillary formation, and excellent smooth muscle regeneration by regulating inflammatory reaction and promoting its rapid resolution. Thus, our study provided new perspectives for long-term vascular graft survival and integration with the host tissue. We believe that AT-RvD1 can be widely applied in tissue engineering owing to its anti-inflammatory and therapeutic effects.

Particle-based artificial three-dimensional stem cell spheroids for revascularization of ischemic diseases

Development of new approaches to biomimetically reconstruct vasculature networks remains challenging in regenerative medicine. We introduce a particle-based artificial stem cell spheroid (ASSP) technology that recapitulates paracrine functions of three-dimensional (3D) SSPs for vasculature regeneration. Specifically, we used a facile method to induce the aggregation of stem cells into 3D spheroids, which benefited from hypoxia microenvironment-driven and enhanced secretion of proangiogenic bioactive factors. Furthermore, we artificially reconstructed 3D spheroids (i.e., ASSP) by integration of SSP-secreted factors into micro-/nanoparticles with cell membrane-derived surface coatings. The easily controllable sizes of the ASSP particles provided superior revascularization effects on the ischemic tissues in hindlimb ischemia models through local administration of ASSP microparticles and in myocardial infarction models via the systemic delivery of ASSP nanoparticles. The strategy offers a promising therapeutic option for ischemic tissue regeneration and addresses issues faced by the bottlenecked development in the delivery of stem cell therapies.

Biomimetic Design of Artificial Hybrid Nanocells for Boosted Vascular Regeneration in Ischemic Tissues

Restoration of sufficient blood supply for the treatment of ischemia remains a significant scientific and clinical challenge. Here, a cell-like nanoparticle delivery technology is introduced that is capable of recapitulating multiple cell functions for the spatiotemporal triggering of vascular regeneration. Specifically, a copper-containing protein is successfully prepared using a recombinant protein scaffold based on a de novo design strategy, which facilitates the timely release of nitric oxide and improved accumulation of particles within ischemic tissues. Through closely mimicking physiological cues, the authors demonstrate the benefits of bioactive factors secreted from hypoxic stem cells on promoting angiogenesis. Following this cell-mimicking manner, artificial hybrid nanosized cells (Hynocell) are constructed by integrating the hypoxic stem cell secretome into nanoparticles with surface coatings of cell membranes fused with copper-containing protein. The Hynocell, hybridized with different cell-derived components, provides synergistic effects on targeting ischemic tissues and promoting vascular regeneration in acute hindlimb ischemia and acute myocardial infarction models. This study offers new insights into the utilization of nanotechnology to potentiate the development of cell-free therapeutics.

Hepatocyte Growth Factor Mediates Enhanced Wound Healing Responses and Resistance to Transforming Growth Factor-β₁-Driven Myofibroblast Differentiation in Oral Mucosal Fibroblasts

Oral mucosal wounds are characterized by rapid healing with minimal scarring, partly attributable to the "enhanced" wound healing properties of oral mucosal fibroblasts (OMFs). Hepatocyte growth factor (HGF) is a pleiotropic growth factor, with potential key roles in accelerating healing and preventing fibrosis. HGF can exist as full-length or truncated (HGF-NK), NK1 and NK2 isoforms. As OMFs display elevated HGF expression compared to dermal fibroblasts (DFs), this study investigated the extent to which HGF mediates the preferential cellular functions of OMFs, and the influence of pro-fibrotic, transforming growth factor-β₁ (TGF-β₁) on these responses. Knockdown of HGF expression in OMFs by short-interfering RNA (siHGF) significantly inhibited OMF proliferative and migratory responses. Supplementation with exogenous TGF-β₁ also significantly inhibited proliferation and migration, concomitant with significantly down-regulated HGF expression. In addition, knockdown abrogated OMF resistance to TGF-β₁-driven myofibroblast differentiation, as evidenced by increased α-smooth muscle actin (α-SMA) expression, F-actin reorganisation, and stress fibre formation. Responses were unaffected in siHGF-transfected DFs. OMFs expressed significantly higher full-length HGF and NK1 levels compared to patient-matched DFs, whilst NK2 expression was similar in both OMFs and DFs. Furthermore, NK2 was preferentially expressed over NK1 in DFs. TGF-β₁ supplementation significantly down-regulated full-length HGF and NK1 expression by OMFs, while NK2 was less affected. This study demonstrates the importance of HGF in mediating "enhanced" OMF cellular function. We also propose that full-length HGF and HGF-NK1 convey desirable wound healing properties, whilst fibroblasts preferentially expressing more HGF-NK2 readily undergo TGF-β₁-driven differentiation into myofibroblasts.