Dual delivery of IL-10 and AT-RvD1 from PEG hydrogels polarize immune cells towards pro-regenerative phenotypes

Optimization of Interleukin-10 incorporation for dendritic cells embedded in Poly(ethylene glycol) hydrogels

Translational research in biomaterials and immunoengineering is leading to the development of novel advanced therapeutics to treat diseases such as cancer, autoimmunity, and viral infections. Dendritic cells (DCs) are at the center of these therapeutics given that they bridge innate and adaptive immunity. The biomaterial system developed herein uses a hydrogel carrier to deliver immunomodulatory DCs for amelioration of autoimmunity. This biomaterial vehicle is comprised of a poly (ethylene glycol)-4 arm maleimide (PEG-4MAL) hydrogels, conjugated with the immunosuppressive cytokine, interleukin-10, IL-10, and cross-linked with a collagenase-degradable peptide sequence for the injectable delivery of immunosuppressive DCs to an anatomical disease-relevant site of the cervical lymph nodes, for intended application to treat multiple sclerosis. The amount of IL-10 incorporated in the hydrogel was optimized to be 500 ng in vitro, based on immunological endpoints. At this concentration, DCs exhibited the best viability, most immunosuppressive phenotype, and protection against proinflammatory insult as compared with hydrogel-incorporated DCs with lower IL-10 loading amounts. Additionally, the effect of the degradability of the PEG-4MAL hydrogel on the release rate of incorporated IL-10 was assessed by varying the ratio of degradable peptides: VPM (degradable) and DTT (nondegradable) and measuring the IL-10 release rates. This IL-10-conjugated hydrogel delivery system for immunosuppressive DCs is set to be assessed for in vivo functionality as the immunosuppressive cytokine provides a tolerogenic environment that keeps DCs in their immature phenotype, which consequently enhances cell viability and optimizes the system's immunomodulatory functionality.

Hydrogel-based immunoregulation of macrophages for tissue repair and regeneration

The rational design of hydrogel materials to modulate the immune microenvironment has emerged as a pivotal approach in expediting tissue repair and regeneration. Within the immune microenvironment, an array of immune cells exists, with macrophages gaining prominence in the field of tissue repair and regeneration due to their roles in cytokine regulation to promote regeneration, maintain tissue homeostasis, and facilitate repair. Macrophages can be categorized into two types: classically activated M1 (pro-inflammatory) and alternatively activated M2 (anti-inflammatory and pro-repair). By regulating the physical and chemical properties of hydrogels, the phenotypic transformation and cell behavior of macrophages can be effectively controlled, thereby promoting tissue regeneration and repair. A full understanding of the interaction between hydrogels and macrophages can provide new ideas and methods for future tissue engineering and clinical treatment. Therefore, this paper reviews the effects of hydrogel components, hardness, pore size, and surface morphology on cell behaviors such as macrophage proliferation, migration, and phenotypic polarization, and explores the application of hydrogels based on macrophage immune regulation in skin, bone, cartilage, and nerve tissue repair. Finally, the challenges and future prospects of macrophage-based immunomodulatory hydrogels are discussed.

Immune regulation enhances osteogenesis and angiogenesis using an injectable thiolated hyaluronic acid hydrogel with lithium-doped nano-hydroxyapatite (Li-nHA) delivery for osteonecrosis

Osteonecrosis is a devastating orthopedic disease in clinic that generally occurs in the femoral head associating with corticosteroid use up to 49 % in patients. In particular, glucocorticoids induced osteonecrosis of the femoral head is closely related to the local immune response that characterized by abnormal macrophage activation and inflammatory cell infiltration at the necrotic site, forming a pro-inflammatory microenvironment dominated by M1 macrophages, and thus leads to failure of bone repair and regeneration. Here, we report a bone regeneration strategy that constructs an immune regulatory biomaterial platform using an injectable thiolated hyaluronic acid hydrogel with lithium-doped nano-hydroxyapatite (Li-nHA@Gel) delivery for osteonecrosis treatment. Li-nHA@Gel achieved a sustain and longterm release of Li ions, which might enhance M2 macrophage polarization through the activation of the JAK1/STAT6/STAT3 signaling pathway, and the following induced pro-repair immune microenvironment mediated the enhancement of the osteogenic and angiogenic differentiation. Moreover, both in vitro and in vivo studies indicated that Li-nHA@Gel enhanced M2 macrophage polarization, osteogenesis, and angiogenesis, and thus promoted the bone and blood vessel formation. Taken together, this novel bone immunomodulatory biomaterial platform that promotes bone regeneration by enhancing M2 macrophage polarization, osteogenesis, and angiogenesis could be a promising strategy for osteonecrosis treatment.

Multifunctional and theranostic hydrogels for wound healing acceleration: An emphasis on diabetic-related chronic wounds

Hydrogels represent intricate three-dimensional polymeric structures, renowned for their compatibility with living systems and their ability to naturally degrade. These networks stand as promising and viable foundations for a range of biomedical uses. The practical feasibility of employing hydrogels in clinical trials has been well-demonstrated. Among the prevalent biomedical uses of hydrogels, a significant application arises in the context of wound healing. This intricate progression involves distinct phases of inflammation, proliferation, and remodeling, often triggered by trauma, skin injuries, and various diseases. Metabolic conditions like diabetes have the potential to give rise to persistent wounds, leading to delayed healing processes. This current review consolidates a collection of experiments focused on the utilization of hydrogels to expedite the recovery of wounds. Hydrogels have the capacity to improve the inflammatory conditions at the wound site, and they achieve this by diminishing levels of reactive oxygen species (ROS), thereby exhibiting antioxidant effects. Hydrogels have the potential to enhance the growth of fibroblasts and keratinocytes at the wound site. They also possess the capability to inhibit both Gram-positive and Gram-negative bacteria, effectively managing wounds infected by drug-resistant bacteria. Hydrogels can trigger angiogenesis and neovascularization processes, while also promoting the M2 polarization of macrophages, which in turn mitigates inflammation at the wound site. Intelligent and versatile hydrogels, encompassing features such as pH sensitivity, reactivity to reactive oxygen species (ROS), and responsiveness to light and temperature, have proven advantageous in expediting wound healing. Furthermore, hydrogels synthesized using environmentally friendly methods, characterized by high levels of biocompatibility and biodegradability, hold the potential for enhancing the wound healing process. Hydrogels can facilitate the controlled discharge of bioactive substances. More recently, there has been progress in the creation of conductive hydrogels, which, when subjected to electrical stimulation, contribute to the enhancement of wound healing. Diabetes mellitus, a metabolic disorder, leads to a slowdown in the wound healing process, often resulting in the formation of persistent wounds. Hydrogels have the capability to expedite the healing of diabetic wounds, facilitating the transition from the inflammatory phase to the proliferative stage. The current review sheds light on the biological functionalities of hydrogels, encompassing their role in modulating diverse mechanisms and cell types, including inflammation, oxidative stress, macrophages, and bacteriology. Additionally, this review emphasizes the significance of smart hydrogels with responsiveness to external stimuli, as well as conductive hydrogels for promoting wound healing. Lastly, the discussion delves into the advancement of environmentally friendly hydrogels with high biocompatibility, aimed at accelerating the wound healing process.

Sustained Release of Dexamethasone from 3D-Printed Scaffolds Modulates Macrophage Activation and Enhances Osteogenic Differentiation

Enhancing osteogenesis via modulating immune cells is emerging as a new approach to address the current challenges in repairing bone defects and fractures. However, much remains unknown about the crosstalk between immune cells and osteolineage cells during bone formation. Moreover, biomaterial scaffold-based approaches to effectively modulate this crosstalk to favor bone healing are also lacking. This study is the first to investigate the interactions between macrophages and mesenchymal stem cells (MSCs) in co-cultures with the sustained release of an anti-inflammatory and pro-osteogenesis drug (dexamethasone) from three-dimensional (3D)-printed scaffolds. We successfully achieved the sustained release of dexamethasone from polycaprolactone (PCL) by adding the excipient-sucrose acetate isobutyrate (SAIB). Dexamethasone was released over 35 days in the 17-163 nM range. The osteogenic differentiation of MSCs was enhanced by M1 macrophages at early time points. The late-stage mineralization was dominated by dexamethasone, with little contribution from the macrophages. Besides confirming BMP-2 whose secretion was promoted by both dexamethasone and M1 macrophages as a soluble mediator for enhanced osteogenesis, IL-6 was found to be a possible new soluble factor that mediated osteogenesis in macrophage-MSC co-cultures. The phenotype switching from M1 to M2 was drastically enhanced by the scaffold-released dexamethasone but only marginally by the co-cultured MSCs. Our results offer new insight into macrophage-MSC crosstalk and demonstrate the potential of using drug-release scaffolds to both modulate inflammation and enhance bone regeneration.

The Use of Specialized Pro-Resolving Mediators in Biomaterial-Based Immunomodulation

The implantation of a biomaterial will lead to the immediate onset of an acute inflammatory response, which is of key importance in shaping the quality of the repair process. However, the return to homeostasis is critical to prevent a chronic inflammatory response that may impair the healing process. The resolution of the inflammatory response is now recognized as an active and highly regulated process, being described as specialized immunoresolvents that have a fundamental role in the termination of the acute inflammatory response. These mediators collectively coined as specialized pro-resolving mediators (SPMs) are a family of endogenous molecules that include lipoxins (Lx), resolvins (Rv), protectins (PD), maresins (Mar), Cysteinyl-SPMs (Cys-SPMs) and n-3 docosapentaenoic acid-derived SPMs (n-3 DPA-derived SPMs). SPMs have important anti-inflammatory and pro-resolutive actions such as decreasing the recruitment of polymorphonuclear leukocytes (PMNs), inducing the recruitment of anti-inflammatory macrophages, and increasing macrophage clearance of apoptotic cells through a process known as efferocytosis. Over the last years, the trend in biomaterials research has shifted towards the engineering of materials that are able to modulate the inflammatory response and thus stimulate appropriate immune responses, the so-called immunomodulatory biomaterials. These materials should be able to modulate the host immune response with the aim of creating a pro-regenerative microenvironment. In this review, we explore the potential of using of SPMs in the development of new immunomodulatory biomaterials and we propose insights for future research in this field.

Silica nanocarrier-mediated intracellular delivery of rapamycin promotes autophagy-mediated M2 macrophage polarization to regulate bone regeneration

Targeting macrophages to regulate the immune microenvironment is a new strategy for bone regeneration with nano-drugs. Nano-drugs have achieved surprising anti-inflammatory and bone-regenerative effects, however, their underlying mechanisms in macrophages remain to be clarified. Macrophage polarization, immunomodulation, and osteogenesis are governed by autophagy. Rapamycin, an autophagy inducer, has shown promising results in bone regeneration, but high dose-mediated cytotoxicity and low bioavailability hinder its clinical application. This study aimed to develop rapamycin-loaded virus-like hollow silica nanoparticles (R@HSNs) which are easily phagocytosed by macrophages and translocated to lysosomes. R@HSNs induced macrophage autophagy, promoted M2 polarization, and alleviated the degree of M1 polarization as indicated by the downregulation of inflammatory factors IL-6, IL-1β, TNF-α, and iNOS, and upregulation of anti-inflammatory factors CD163, CD206, IL-1ra, IL-10, and TGF-β. These effects were nullified by cytochalasin B-induced inhibition of R@HSNs uptake in macrophages. The conditioned medium (CM) collected from R@HSNs-treated macrophages promoted osteogenic differentiation of mouse bone marrow mesenchymal stromal cells (mBMSCs). In a mouse calvaria defect model, free rapamycin treatment was inhibited, but R@HSNs robustly promoted bone defect healing. In conclusion, silica nanocarrier-mediated intracellular rapamycin delivery to macrophages effectively triggers autophagy-mediated M2 macrophage polarization, further enhancing bone regeneration by triggering osteogenic differentiation of mBMSCs.

Immunomodulatory Biomaterials and Emerging Analytical Techniques for Probing the Immune Micro-Environment

After implantation of a biomaterial, both the host immune system and properties of the material determine the local immune response. Through triggering or modulating the local immune response, materials can be designed towards a desired direction of promoting tissue repair or regeneration. High-throughput sequencing technologies such as single-cell RNA sequencing (scRNA-seq) emerging as a powerful tool for dissecting the immune micro-environment around biomaterials, have not been fully utilized in the field of soft tissue regeneration. In this review, we first discussed the procedures of foreign body reaction in brief. Then, we summarized the influences that physical and chemical modulation of biomaterials have on cell behaviors in the micro-environment. Finally, we discussed the application of scRNA-seq in probing the scaffold immune micro-environment and provided some reference to designing immunomodulatory biomaterials. The foreign body response consists of a series of biological reactions. Immunomodulatory materials regulate immune cell activation and polarization, mediate divergent local immune micro-environments and possess different tissue engineering functions. The manipulation of physical and chemical properties of scaffolds can modulate local immune responses, resulting in different outcomes of fibrosis or tissue regeneration. With the advancement of technology, emerging techniques such as scRNA-seq provide an unprecedented understanding of immune cell heterogeneity and plasticity in a scaffold-induced immune micro-environment at high resolution. The in-depth understanding of the interaction between scaffolds and the host immune system helps to provide clues for the design of biomaterials to optimize regeneration and promote a pro-regenerative local immune micro-environment.

Phosphatidylserine liposome multilayers mediate the M1-to-M2 macrophage polarization to enhance bone tissue regeneration

An appropriate immune microenvironment, governed by macrophages, is essential for rapid tissue regeneration after biomaterial implantation. The macrophage phenotypes, M1 (inflammatory) and M2 (anti-inflammatory/healing), exert opposing effects on the repair of various tissues. In this study, a new strategy to promote tissue repair and tissue-to-biomaterial integration by M1-to-M2 macrophage transition using artificial apoptotic cell mimetics (phosphatidylserine liposomes; PSLs) was developed using bone as a model tissue. Titanium was also selected as a model substrate material because it is widely used for dental and orthopedic implants. Titanium implants were functionalized with multilayers via layer-by-layer assembly of cationic protamine and negatively charged PSLs that were chemically stabilized to prevent disruption of lipid bilayers. Samples carrying PSL multilayers could drive M1-type macrophages into M2-biased phenotypes, resulting in a dramatic change in macrophage secretion for tissue regeneration. In a rat femur implantation model, the PSL-multilayer-coated implant displayed augmented de novo bone formation and bone-to-implant integration, associated with an increased M1-to-M2-like phenotypic transition. This triggered the proper generation and activation of bone-forming osteoblasts and bone-resorbing osteoclasts relative to their uncoated counterparts. This study demonstrates the benefit of local M1-to-M2 macrophage polarization induced by PSL-multilayers constructed on implants for potent bone regeneration and bone-to-implant integration. The results of this study may help in the design of new immunomodulatory biomaterials. STATEMENT OF SIGNIFICANCE: Effective strategies for tissue regeneration are essential in the clinical practice. The macrophage phenotypes, M1 (inflammatory) and M2 (anti-inflammatory/healing), exert opposing effects on the repair of various tissues. Artificially produced phosphatidylserine-containing liposomes (PSLs) can induce M2 macrophage polarization by mimicking the inverted plasma membranes of apoptotic cells. This study demonstrates the advantages of local M1-to-M2 macrophage polarization induced by PSL-multilayers constructed on implants for effective bone regeneration and osseointegration (bone-to-implant integration). Mechanistically, M2 macrophages promote osteogenesis but inhibit osteoclastogenesis, and M1 macrophages vice versa. We believe that our study makes a significant contribution to the design of new immunomodulatory biomaterials for regenerative medicine because it is the first to validate the benefit of PSLs for tissue regeneration.

H2O2-activated in situ polymerization of aniline derivative in hydrogel for real-time monitoring and inhibition of wound bacterial infection

Wound is highly susceptible to bacterial infection, which can cause chronic wound and serial complications. However, timely treatment is hampered by the lack of real-time monitoring of wound status and effective therapeutic systems. Herein, in situ biosynthesis of functional conjugated polymer in artificial hydrogel was developed via the utilization of biological microenvironment to realize monitoring in real time of wound infection and inhibition of bacteria for the first time. Specially, an easily polymerizable aniline dimer derivative (N-(3-sulfopropyl) p-aminodiphenylamine, SPA) was artfully in situ polymerized into polySPA (PSPA) in calcium alginate hydrogel, which was initiated via the catalysis of hydrogen peroxide (H₂O₂) overexpressed in infected wound to produce hydroxyl radical (•OH) by preloaded horseradish peroxidase (HRP). Benefitting from outstanding near infrared (NIR) absorption of PSPA, such polymerization can be ingeniously used for real-time monitoring of H₂O₂ via naked-eye and photoacoustic signal, as well as NIR light-mediated photothermal inhibition of bacteria. Furthermore, combining the persistent chemodynamic activity of •OH, the in vivo experimental data proved that the wound healing rate was 99.03% on the 11th day after treatment. Therefore, the present work opens the way to manipulate in situ biosynthesis of functional conjugated polymer in artificial hydrogels for overcoming the issues on wound theranostics.

Engineering immunomodulatory hydrogels and cell-laden systems towards bone regeneration

The well-known synergetic interplay between the skeletal and immune systems has changed the design of advanced bone tissue engineering strategies. The immune system is essential during the bone lifetime, with macrophages playing multiple roles in bone healing and biomaterial integration. If in the past, the most valuable aspect of implants was to avoid immune responses of the host, nowadays, it is well-established how important are the crosstalks between immune cells and bone-engineered niches for an efficient regenerative process to occur. For that, it is essential to recapitulate the multiphenotypic cellular environment of bone tissue when designing new approaches. Indeed, the lack of osteoimmunomodulatory knowledge may be the explanation for the poor translation of biomaterials into clinical practice. Thus, smarter hydrogels incorporating immunomodulatory bioactive factors, stem cells, and immune cells are being proposed to develop a new generation of bone tissue engineering strategies. This review highlights the power of immune cells to upgrade the development of innovative engineered strategies, mainly focusing on orthopaedic and dental applications.

Emerging Bioactive Agent Delivery-Based Regenerative Therapies for Lower Genitourinary Tissues

Injury to lower genitourinary (GU) tissues, which may result in either infertility and/or organ dysfunctions, threatens the overall health of humans. Bioactive agent-based regenerative therapy is a promising therapeutic method. However, strategies for spatiotemporal delivery of bioactive agents with optimal stability, activity, and tunable delivery for effective sustained disease management are still in need and present challenges. In this review, we present the advancements of the pivotal components in delivery systems, including biomedical innovations, system fabrication methods, and loading strategies, which may improve the performance of delivery systems for better regenerative effects. We also review the most recent developments in the application of these technologies, and the potential for delivery-based regenerative therapies to treat lower GU injuries. Recent progress suggests that the use of advanced strategies have not only made it possible to develop better and more diverse functionalities, but also more precise, and smarter bioactive agent delivery systems for regenerative therapy. Their application in lower GU injury treatment has achieved certain effects in both patients with lower genitourinary injuries and/or in model animals. The continuous evolution of biomaterials and therapeutic agents, advances in three-dimensional printing, as well as emerging techniques all show a promising future for the treatment of lower GU-related disorders and dysfunctions.

Resolution of Inflammation after Skeletal Muscle Ischemia-Reperfusion Injury: A Focus on the Lipid Mediators Lipoxins, Resolvins, Protectins and Maresins

Skeletal muscle ischemia reperfusion is very frequent in humans and results not only in muscle destruction but also in multi-organ failure and death via systemic effects related to inflammation and oxidative stress. In addition to overabundance of pro-inflammatory stimuli, excessive and uncontrolled inflammation can also result from defects in resolution signaling. Importantly, the resolution of inflammation is an active process also based on specific lipid mediators including lipoxins, resolvins and maresins that orchestrate the potential return to tissue homeostasis. Thus, lipid mediators have received growing attention since they dampen deleterious effects related to ischemia–reperfusion. For instance, the treatment of skeletal muscles with resolvins prior to ischemia decreases polymorphonuclear leukocyte (PMN) infiltration. Additionally, remote alterations in lungs or kidneys are reduced when enhancing lipid mediators’ functions. Accordingly, lipoxins prevented oxidative-stress-mediated tissue injuries, macrophage polarization was modified and in mice lacking DRV2 receptors, ischemia/reperfusion resulted in excessive leukocyte accumulation. In this review, we first aimed to describe the inflammatory response during ischemia and reperfusion in skeletal muscle and then discuss recent discoveries in resolution pathways. We focused on the role of specialized pro-resolving mediators (SPMs) derived from polyunsaturated fatty acids (PUFAs) and their potential therapeutic applications.

Immunomodulatory Microgels Support Proregenerative Macrophage Activation and Attenuate Fibroblast Collagen Synthesis

Scars composed of fibrous connective tissues are natural consequences of injury upon incisional wound healing in soft tissues.  Hydrogels that feature a sustained presentation of immunomodulatory cytokines are known to modulate wound healing. However, existing immunomodulatory hydrogels lack interconnected micropores to promote cell ingrowth. Other limitations include invasive delivery procedures and harsh synthesis conditions that are incompatible with drug molecules. Here, hybrid nanocomposite microgels containing interleukin-10 (IL-10) are reported to modulate tissue macrophage phenotype during wound healing. The intercalation of laponite nanoparticles in the polymer network yields microgels with tissue-mimetic elasticity (Young's modulus in the range of 2-6 kPa) and allows the sustained release of IL-10 to promote the differentiation of macrophages toward proregenerative phenotypes. The porous interstitial spaces between microgels promote fibroblast proliferation and fast trafficking (an average speed of ≈14.4 µm h^-1 ). The incorporation of hyaluronic acid further enhances macrophage infiltration. The coculture of macrophages and fibroblasts treated with transforming growth factor-beta 1 resulted in a twofold reduction in collagen-I production for microgels releasing IL-10 compared to the IL-10 free group. The new microgels show potential toward regenerative healing by harnessing the antifibrotic behavior of host macrophages.

Immunomodulation of Telmisartan-Loaded PCL/PVP Scaffolds on Macrophages Promotes Endogenous Bone Regeneration

Biomaterial-immune system interactions play an important role in postimplantation osseointegration to retain the functionality of healthy and intact bones. Therefore, appropriate osteoimmunomodulation of implants has been considered and validated as an efficient strategy to alleviate inflammation and enhance new bone formation. Here, we fabricated a nanostructured PCL/PVP (polycaprolactone/polyvinylpyrrolidone) electrospinning scaffold for cell adhesion, tissue ingrowth, and bone defect padding. In addition, telmisartan, an angiotensin 2 receptor blocker with distinct immune bioactivity, was doped into PCL-/PVP-electrospun scaffolds at different proportions [1% (TPP-1), 5% (TPP-5), and 10% (TPP-10)] to investigate its immunomodulatory effects and osteoinductivity/conductivity. Telmisartan-loaded scaffolds displayed in vitro anti-inflammatory bioactivity on lipopolysaccharide-induced M1 macrophages by polarizing them to an M2-like phenotype and exhibited pro-osteogenic properties on bone marrow-derived mesenchymal stem cells (BMSCs). Histological analysis and micro-CT results of a rat skull defect model also showed that the telmisartan-loaded scaffolds induced a higher M2/M1 ratio, less inflammatory infiltration, and better bone regenerative patterns. Furthermore, activation of the BMP2 (bone morphogenetic protein-2)-Smad signaling pathway was found to be dominant in telmisartan-loaded scaffold-mediated macrophage-BMSC interactions. These findings indicate that telmisartan incorporation with PCL/PVP nanofibrous scaffolds is a potential therapeutic strategy for promoting bone healing by modulating M1 macrophages to a more M2 phenotype at early stages of postimplantation.

Bone marrow mesenchymal stem cells enhance angiogenesis and promote fat retention in fat grafting via polarized macrophages

Background

Fat grafting is one of the most common soft tissue filling methods in plastic surgery. Bone marrow mesenchymal stem cell (BM-MSC) transplantation is an effective method for improving graft retention. However, the role of BM-MSCs in fat transplantation is not completely clear.

Methods

Human fat particles, together with BM-MSCs or PBS as a control, were subcutaneously transplanted into the backs of nude mice. Samples were taken on days 14, 30 and 90 post-grafting to calculate the fat graft retention rate, and tissue staining was evaluated. Furthermore, macrophages were treated with BM-MSC conditioned medium (BM-MSC-CM) to identify the beneficial component secreted by these stem cells.

Results

In this study, we found that BM-MSCs improved retention by enhancing angiogenesis in fat grafting. Further analysis revealed that BM-MSCs could significantly inhibit the expression of the proinflammatory M1 macrophage markers interleukin (IL)-1β, tumor necrosis factor-α (TNF-α) and IL-6 in the early stages of fat grafting and promote the expression of the anti-inflammatory M2 macrophage markers Arg1, IL-10 and VEGF. Furthermore, our results showed that IL-10 secreted by BM-MSCs induced M2 macrophage polarization in vitro.

Conclusions

BM-MSC transplantation can improve the fat retention rate and promote angiogenesis, which may be related to M2 macrophages. These results help elucidate the role of BM-MSCs in fat grafting.

Nucleus-selective codelivery of proteins and drugs for synergistic antitumor therapy

Subcellular organelle targeted transport is of great significance for accurately delivering drugs to active sites for better pharmacological effects, but there are still a lot of challenges due to transport problems. In addition, the killing effect of one kind of drug on cells is limited. Therefore, it is necessary to develop a multifunctional nanoplatform that can co-deliver synergistic therapeutic agents. Here, we prepare a simple amphiphilic nanocarrier (LC) with rapid endosomal escape ability for nucleus-selective delivery of hydrophilic active protein deoxyribonuclease I (DNase I) and hydrophobic anticancer drug doxorubicin (DOX). LC has been applied to effectively encapsulate DNase I just by simply mixing their aqueous solutions together. In addition, DOX modified with adamantane groups via a redox-responsive linker is incorporated into the architecture of DNase I nanoformulations through host–guest interaction. This multi-component nanoplatform can quickly escape from the endolysosomes into the cytoplasm and make DNase I and DOX highly accumulate in the nucleus and consequently induce strong synergistic anticancer efficacy both in vitro and in vivo. This work illustrates a new platform for codelivery of proteins and drugs that target subcellular compartments for functions.

An efficient nucleus-targeted co-delivery nanoplatform with high endosomal escape ability to transport proteins and drugs into nucleus was prepared for synergistically enhanced cancer therapy.

Macrophage phenotypes in tissue repair and the foreign body response: Implications for biomaterial-based regenerative medicine strategies

Macrophages are a highly heterogeneous and plastic population of cells that are crucial for tissue repair and regeneration. This has made macrophages a particularly attractive target for biomaterial-directed regenerative medicine strategies. However, macrophages also contribute to adverse inflammatory and fibrotic responses to implanted biomaterials, typically related to the foreign body response (FBR). The traditional model in the field asserts that the M2 macrophage phenotype is pro-regenerative and associated with positive wound healing outcomes, whereas the M1 phenotype is pro-inflammatory and associated with pathogenesis. However, recent studies indicate that both M1 and M2 macrophages play different, but equally vital, roles in promoting tissue repair. Furthermore, recent technological developments such as single-cell RNA sequencing have allowed for unprecedented insights into the heterogeneity within the myeloid compartment, related to activation state, niche, and ontogenetic origin. A better understanding of the phenotypic and functional characteristics of macrophages critical to tissue repair and FBR processes will allow for rational design of biomaterials to promote biomaterial-tissue integration and regeneration. In this review, we discuss the role of temporal and ontogenetic macrophage heterogeneity on tissue repair processes and the FBR and the potential implications for biomaterial-directed regenerative medicine applications. STATEMENT OF SIGNIFICANCE: This review outlines the contributions of different macrophage phenotypes to different phases of wound healing and angiogenesis. Pathological outcomes, such as chronic inflammation, fibrosis, and the foreign body response, related to disruption of the macrophage inflammation-resolution process are also discussed. We summarize recent insights into the vast heterogeneity of myeloid cells related to their niche, especially the biomaterial microenvironment, and ontogenetic origin. Additionally, we present a discussion on novel tools that allow for resolution of cellular heterogeneity at the single-cell level and how these can be used to build a better understanding of macrophage heterogeneity in the biomaterial immune microenvironment to better inform immunomodulatory biomaterial design.

Toward a Better Regeneration through Implant-Mediated Immunomodulation: Harnessing the Immune Responses

Tissue repair/regeneration, after implantation or injury, involves comprehensive physiological processes wherein immune responses play a crucial role to enable tissue restoration, amidst the immune cells early-stage response to tissue damages. These cells break down extracellular matrix, clear debris, and secret cytokines to orchestrate regeneration. However, the immune response can also lead to abnormal tissue healing or scar formation if not well directed. This review first introduces the general immune response post injury, with focus on the major immune cells including neutrophils, macrophages, and T cells. Next, a variety of implant-mediated immunomodulation strategies to regulate immune response through physical, chemical, and biological cues are discussed. At last, various scaffold-facilitated regenerations of different tissue types, such as, bone, cartilage, blood vessel, and nerve system, by harnessing the immunomodulation are presented. Therefore, the most recent data in biomaterials and immunomodulation is presented here in a bid to shape expert perspectives, inspire researchers to go in new directions, and drive development of future strategies focusing on targeted, sequential, and dynamic immunomodulation elicited by implants.

The Role of Innate and Adaptive Immune Cells in Skeletal Muscle Regeneration

Skeletal muscle regeneration is highly dependent on the inflammatory response. A wide variety of innate and adaptive immune cells orchestrate the complex process of muscle repair. This review provides information about the various types of immune cells and biomolecules that have been shown to mediate muscle regeneration following injury and degenerative diseases. Recently developed cell and drug-based immunomodulatory strategies are highlighted. An improved understanding of the immune response to injured and diseased skeletal muscle will be essential for the development of therapeutic strategies.

Injectable and Degradable PEG Hydrogel with Antibacterial Performance for Promoting Wound Healing

Injectable and degradable PEG hydrogel was prepared via Michael-type addition between cross-linking monomer 4-arm-PEG-MAL and two cross-linkers of hydrolysis degradable PEG-diester-dithiol and non-degradable PEG-dithiol, and it had a porous structure with the uniform pore size. The biocompatibility assays in vitro indicated that PEG hydrogel had excellent biocompatibility and can be degraded naturally without leading to any negative impact on cells. The results of antibacterial experiments showed that PEG hydrogel can inhibit the growth of bacteria. Furthermore, the Cell Counting Kit-8 (CCK-8) assay, LIVE/DEAD cell staining, and scratch healing experiments proved that PEG hydrogel can promote cell proliferation and migration, which had been further confirmed in in vivo experiments on the rat wound models. All experimental results demonstrated that PEG hydrogel is an injectable antibacterial dressing, which can promote the process of wound healing and has great potential in the field of wound healing.

Cysteinyl-specialized proresolving mediators link resolution of infectious inflammation and tissue regeneration via TRAF3 activation

The recently elucidated proresolving conjugates in tissue regeneration (CTR) maresin-CTR (MCTR), protectin-CTR (PCTR), and resolvin-CTR (RCTR), termed cysteinyl-specialized proresolving mediators (cys-SPMs) each promotes regeneration, controls infection, and accelerates resolution of inflammation. Here, we sought evidence for cys-SPM activation of primordial pathways in planaria (Dugesia japonica) regeneration that might link resolution of inflammation and regeneration. On surgical resection, planaria regeneration was enhanced with MCTR3, PCTR3, or RCTR3 (10 nM), each used for RNA sequencing. The three cys-SPMs shared up-regulation of 175 known transcripts with fold-change > 1.25 and combined false discovery rate (FDR) < 0.002, and 199 canonical pathways (FDR < 0.25), including NF-κB pathways and an ortholog of human TRAF3 (TNFR-associated factor 3). Three separate pathway analyses converged on TRAF3 up-regulation by cys-SPMs. With human macrophages, three cys-SPMs each dose-dependently increased TRAF3 expression in a cAMP-PKA-dependent manner. TRAF3 overexpression in macrophages enhanced Interleukin-10 (IL-10) and phagocytosis of Escherichia coli IL-10 also increased phagocytosis in a dose-dependent manner. Silencing of mouse TRAF3 in vivo significantly reduced IL-10 and macrophage phagocytosis. TRAF3 silencing in vivo also relieved cys-SPMs' actions in limiting polymorphonuclear neutrophil in E. coli exudates. These results identify cys-SPM-regulated pathways in planaria regeneration, uncovering a role for TRAF3/IL-10 in regulating mammalian phagocyte functions in resolution. Cys-SPM activation of TRAF3 signaling is a molecular component of both regeneration and resolution of infectious inflammation.