Regulation of extracellular matrix assembly and structure by hybrid M1/M2 macrophages

The mesenchymal stromal cell secretome promotes tissue regeneration and increases macrophage infiltration in acute and methicillin-resistant Staphylococcus aureus-infected skin wounds in vivo

BACKGROUND AIMS

The prevalence of chronic wounds continues to be a burden in human medicine. Methicillin-resistant Staphylococcus aureus (MRSA) is commonly isolated from infected wounds. MRSA infections primarily delay healing by impairing local immune cell functions. This study aimed to investigate the potential of mesenchymal stromal cell (MSC)-secreted bioactive factors, defined as the secretome, to improve innate immune responses in vivo. MSCs were isolated from the bone marrow of horses, which serve as valuable translational models for wound healing. The MSC secretome, collected as conditioned medium (CM), was evaluated in vivo using mouse models of acute and MRSA-infected skin wounds.

METHODS

Punch biopsies were used to create two full-thickness skin wounds on the back of each mouse. Acute wounds were treated daily with control medium or bone marrow-derived MSC (BM-MSC) CM. The antibiotic mupirocin was administered as a positive control for the MRSA-infected wound experiments. Wounds were photographed daily, and wound images were measured to determine the rate of closure. Trichrome staining was carried out to examine wound tissue histologically, and immunofluorescence antibody binding was used to assess immune cell infiltration. Wounds in the MRSA-infected model were swabbed for quantification of bacterial load.

RESULTS

Acute wounds treated with BM-MSC CM showed accelerated wound closure compared with controls, as illustrated by enhanced granulation tissue formation and resolution, increased vasculature and regeneration of hair follicles. This treatment also led to increased neutrophil and macrophage infiltration. Chronic MRSA-infected wounds treated with BM-MSC CM showed reduced bacterial load accompanied by better resolution of granulation tissue formation and increased infiltration of pro-healing M2 macrophages compared with control-treated infected wounds.

CONCLUSIONS

Collectively, our findings indicate that BM-MSC CM exerts pro-healing, immunomodulatory and anti-bacterial effects on wound healing in vivo, validating further exploration of the MSC secretome as a novel treatment option to improve healing of both acute and chronic wounds, especially those infected with antibiotic-resistant bacteria.

Bacteriophage-cocktail hydrogel dressing to prevent multiple bacterial infections and heal diabetic ulcers in mice

Bacteriophage (phage) has been reported to reduce the bacterial infection in delayed-healing wounds and, as a result, aiding in the healing of said wounds. In this study we investigated whether the presence of phage itself could help repair delayed-healing wounds in diabetic mice. Three strains of phage that target Salmonella enterica, Escherichia coli, and Pseudomonas aeruginosa were used. To prevent the phage liquid from running off the wound, the mixture of phage (phage-cocktail) was encapsulated in a porous hydrogel dressing made with three-dimensional printing. The phage-cocktail dressing was tested for its phage preservation and release efficacy, bacterial reduction, cytotoxicity with 3T3 fibroblast, and performance in repairing a sterile full-thickness skin wound in diabetic mice. The phage-cocktail dressing released 1.7%-5.7% of the phages embedded in 24 h, and reduced between 37%-79% of the surface bacteria compared with the blank dressing (p <.05). The phage-cocktail dressing exhibited no sign of cytotoxicity after 3 days (p <.05). In vivo studies showed that 14 days after incision, the full-thickness wound treated with a phage-cocktail dressing had a higher wound healing ratio compared with the blank dressing and control (p <.01). Histological analysis showed that the structure of the skin layers in the group treated with phage-cocktail dressing was restored in an orderly fashion. Compared with the blank dressing and control, the repaired tissue in the phage-cocktail dressing group had new capillary vessels and no sign of inflammation in its dermis, and its epidermis had a higher degree of re-epithelialization (p <.05). The slow-released phage has demonstrated positive effects in repairing diabetic skin wounds.

Inflammation environment-adaptive matrix confinement for three-dimensional modulation of macrophages

The balance of macrophages in immune reactions is crucial for tissue repair. Despite some studies on responsive surfaces for immunomodulation regulation of macrophage phenotypes via external stimuli, 2D and manual interventions are limited. Herein, to address these limitations, we developed an inflammation environment-responsive macrophage-laden hydrogel-filled scaffold for investigating the impact of matrix confinement on macrophage phenotypes adaptively. We fabricated gelatin scaffolds with a controllable pore size and found that macrophages within smaller pores tended to have an anti-inflammation phenotype. We prepared poly(vinyl alcohol) (PVA)-based hydrogels crosslinked with phenylboronic acid (PBA)-based linkers. The hydrogels possessed shear-thinning, cell-loading, and ROS-sensitive-degradation abilities. Subsequently, a macrophage-laden hydrogel-filled scaffold was fabricated by filling the hydrogels into the porous scaffold under vacuum. With the degradation of the hydrogels under the overexpression of ROS in an inflammation environment, the macrophages were transferred from a state with strong matrix confinement to that with a weaker one. Meanwhile, with the change in matrix confinement, the macrophages upregulated the expressions of Arg-1 and IL-10 and downregulated the expressions of IL-1β, TNF-α, and IL-6, indicating polarization toward the anti-inflammatory phenotype. The inflammation environment-adaptive modulation of macrophage phenotypes in 3D provides a smart and biomimetic strategy for immunomodulation and regenerative medicine.

Electrospun Fiber Surface Roughness Modulates Human Monocyte-Derived Macrophage Phenotype

Injuries to fibrous connective tissues have very little capacity for self-renewal and exhibit poor healing after injury. Phenotypic shifts in macrophages play a vital role in mediating the healing response, creating an opportunity to design immunomodulatory biomaterials which control macrophage polarization and promote regeneration. In this study, electrospun poly(-caprolactone) fibers with increasing surface roughness (SR) were produced by increasing relative humidity and inducing vapor-induced phase separation during the electrospinning process. The impact of surface roughness on macrophage phenotype was assessed using human monocyte-derived macrophages in vitro and in vivo using B6.Cg-Tg(Csf1r-EGFP)1Hume/J (MacGreen) mice. In vitro experiments showed that macrophages cultured on mesh with increasing SR exhibited decreased release of both pro- and anti-inflammatory cytokines potentially driven by increased protein adsorption and biophysical impacts on the cells. Further, increasing SR led to an increase in the expression of the pro-regenerative cell surface marker CD206 relative to the pro-inflammatory marker CD80. Mesh with increasing SR were implanted subcutaneously in MacGreen mice, again showing an increase in the ratio of cells expressing CD206 to those expressing CD80 visualized by immunofluorescence. SR on implanted biomaterials is sufficient to drive macrophage polarization, demonstrating a simple feature to include in biomaterial design to control innate immunity.

Multifunctional composite soluble microneedle patch based on "one stone, three birds" strategy for promoting the healing of infectious wounds

The colonisation of microorganisms such as bacteria forms a biofilm barrier on the wound's surface, preventing or delaying the penetration of antibacterial drugs. At the same time, continuous bacterial infection can cause oxidative stress and an inflammatory response and hinder angiogenesis, resulting in difficult wound healing. Based on the "one stone, three birds" strategy, a multi-functional nanoparticle composite soluble microneedle was designed and developed to solve this dilemma better. Ginsenoside-liposomes(R-Lipo) were prepared by ginsenoside Rg3, which had the effect of promoting repair, instead of cholesterol, and loaded with berberine (Ber), the antibacterial component of Coptis, together with polydopamine (PDA), which had anti-inflammatory and antioxidant properties, into microneedles based on hyaluronic acid (PDA/R-Lipo@BerMN). PDA/R-Lipo@BerMN tip can penetrate and destroy the integrity of the biofilm, dissolve under the action of hyaluronidase in the skin, and gradually release the drug to achieve rapid antibacterial, anti-inflammatory, antioxidant, and proliferation. As expected, the PDA/R-Lipo@BerMN patch effectively cleared ROS during wound closure, further promoted M2 macrophage polarisation, eradicated bacterial infection, and regulated the immune microenvironment, promoting inflammation suppression, collagen deposition, angiogenesis, and tissue regeneration.

Interleukin-4-Loaded Gelatin Methacryloyl Hydrogel Promotes Subcutaneous Chondrogenesis of Engineered Auricular Cartilage in a Rabbit Model

Tissue engineering technology offers a promising solution for ear reconstruction; however, it faces the challenge of foreign body reaction and neocartilage malformation. This study investigates the impact of interleukin-4 (IL-4), an anti-inflammatory factor, on cartilage regeneration of hydrogel encapsulating autologous auricular chondrocytes in a rabbit subcutaneous environment. Initially, we assessed the influence of IL-4 on chondrocyte proliferation and determined the appropriate concentration using the CCK-8 test in vitro. Subsequently, we loaded IL-4 into gelatin methacryloyl (GelMA) hydrogel containing chondrocytes and measured its release profile through ELISA. The constructs were then implanted autologously into rabbits' subcutis, and after 3, 7, 14, and 28 days, cartilage matrix formation was evaluated by histological examinations, and gene expression levels were detected by qRT-PCR. Results demonstrated that IL-4 promotes chondrocyte proliferation in vitro, and maximum release from constructs occurred during the first week. In the rabbit subcutaneous implantation model, IL-4-loaded constructs (20 ng/mL) maintained a superior chondrocytic phenotype compared to controls with increased expression of anti-inflammatory factors. These findings highlight IL-4 as a potential strategy for promoting chondrogenesis in a subcutaneous environment and improving ear reconstruction.

The sEVs miR-487a/Notch2/GATA3 axis promotes osteosarcoma lung metastasis by inducing macrophage polarization toward the M2-subtype

Small extracellular vesicles (sEVs) are important mediators of intercellular communication between tumor cells and their surrounding environment. Furthermore, the mechanisms by which miRNAs carried in tumor sEVs regulate macrophage polarization remain largely unknown. To concentrate sEVs, we used the traditional ultracentrifugation method. Western blot, NanoSight, and transmission electron microscopy were used to identify sEVs. To determine the function of sEVs-miR-487a, we conducted in vivo and in vitro investigations. The intercellular communication mechanism between osteosarcoma cells and M2 macrophages, mediated by sEVs carrying miR-487a, was validated using luciferase reporter assays, transwell assays, and Western blot analysis. In vitro, sEVs enriched in miR-487a and delivered miR-487a to macrophages, promoting macrophage polarization toward an M2-like type, which promotes proliferation, migration, invasion, and epithelial-mesenchymal transition (EMT) of osteosarcoma cells. In vivo, sEVs enriched in miR-487a facilitate lung metastasis of osteosarcoma. Moreover, plasma miR-487a in sEVs was shown to be a potential biomarker applicable for osteosarcoma diagnosis. In summary, miR-487a derived from osteosarcoma cells can be transferred to macrophages via sEVs, then promote macrophage polarization towards an M2-like type by targeting Notch2 and activating the GATA3 pathway. In a feedback loop, the activation of macrophages accelerates epithelial-mesenchymal transition (EMT), which in turn promotes the migration, invasion, and lung metastasis of osteosarcoma cells. This reciprocal interaction between activated macrophages and osteosarcoma cells contributes to the progression of the disease. Our data demonstrate a new mechanism that osteosarcoma tumor cells derived exosomal-miR-487a which is involved in osteosarcoma development by regulating macrophage polarization in tumor microenvironment (TME).

Tertiary lymphoid structures in diseases: immune mechanisms and therapeutic advances

Tertiary lymphoid structures (TLSs) are defined as lymphoid aggregates formed in non-hematopoietic organs under pathological conditions. Similar to secondary lymphoid organs (SLOs), the formation of TLSs relies on the interaction between lymphoid tissue inducer (LTi) cells and lymphoid tissue organizer (LTo) cells, involving multiple cytokines. Heterogeneity is a distinguishing feature of TLSs, which may lead to differences in their functions. Growing evidence suggests that TLSs are associated with various diseases, such as cancers, autoimmune diseases, transplant rejection, chronic inflammation, infection, and even ageing. However, the detailed mechanisms behind these clinical associations are not yet fully understood. The mechanisms by which TLS maturation and localization affect immune function are also unclear. Therefore, it is necessary to enhance the understanding of TLS development and function at the cellular and molecular level, which may allow us to utilize them to improve the immune microenvironment. In this review, we delve into the composition, formation mechanism, associations with diseases, and potential therapeutic applications of TLSs. Furthermore, we discuss the therapeutic implications of TLSs, such as their role as markers of therapeutic response and prognosis. Finally, we summarize various methods for detecting and targeting TLSs. Overall, we provide a comprehensive understanding of TLSs and aim to develop more effective therapeutic strategies.

Magnesium implants with alternating magnetic field-enhanced hydrogen release and proton depletion for anti-infection treatment and tissue repair

Implant-related osteomyelitis is a formidable hurdle in the clinical setting and is characterized by inflammation, infection, and consequential bone destruction. Therefore, effective reactive oxygen species (ROS) scavenging, bacterial killing, and subsequent bone tissue repair are urgently needed for the treatment of difficult-to-heal osteomyelitis. Herein, we utilized the eddy-thermal effect of magnesium (Mg) implants under an alternating magnetic field (AMF) for the controlled release of H2 gas and ions (OH- and Mg2+) for the treatment of osteomyelitis. H2 released by Mg rods under AMFs effectively scavenged cytotoxic ROS, exhibiting anti-inflammatory effects and consequently disrupting the environment of bacterial infections. In addition, the OH- hindered the energy metabolism of bacteria by effectively neutralizing protons within the microenvironment. Moreover, H2 impaired the permeability of bacterial membranes and expedited the damage induced by OH-. This synergistic AMF-induced H2 and proton depletion treatment approach not only killed both gram-negative and gram-positive bacteria but also effectively treated bacterial infections (abscesses and osteomyelitis). Moreover, Mg2+ released from the Mg rods enhanced and accelerated the process of bone osteogenesis. Overall, our work cleverly exploited the eddy-thermal effect and chemical activity of Mg implants under AMFs, aiming to eliminate the inflammatory environment and combat bacterial infections by the simultaneous release of H2, OH-, and Mg2+, thereby facilitating tissue regeneration. This therapeutic strategy achieved multiple benefits in one, thus presenting a promising avenue for clinical application.

Stimuli-Mediated Macrophage Switching, Unraveling the Dynamics at the Nanoplatforms-Macrophage Interface

Macrophages play an essential role in immunotherapy and tissue regeneration owing to their remarkable plasticity and diverse functions. Recent bioengineering developments have focused on using external physical stimuli such as electric and magnetic fields, temperature, and compressive stress, among others, on micro/nanostructures to induce macrophage polarization, thereby increasing their therapeutic potential. However, it is difficult to find a concise review of the interaction between physical stimuli, advanced micro/nanostructures, and macrophage polarization. This review examines the present research on physical stimuli-induced macrophage polarization on micro/nanoplatforms, emphasizing the synergistic role of fabricated structure and stimulation for advanced immunotherapy and tissue regeneration. A concise overview of the research advancements investigating the impact of physical stimuli, including electric fields, magnetic fields, compressive forces, fluid shear stress, photothermal stimuli, and multiple stimulations on the polarization of macrophages within complex engineered structures, is provided. The prospective implications of these strategies in regenerative medicine and immunotherapeutic approaches are highlighted. This review will aid in creating stimuli-responsive platforms for immunomodulation and tissue regeneration.

Relaxin combined with transarterial chemoembolization achieved synergistic effects and inhibited liver cancer metastasis in a rabbit VX2 model

OBJECTIVE

To explore the effect and mechanism of relaxin (RLX) in the growth and metastasis of livercancer after combination treatment with transarterial chemoembolization (TACE).

MATERIALS AND METHODS

HCCLM3 and Huh-7 cells were adopted to evaluate the effect of tumor proliferation, migration, and invasion after RLX administration in vitro. The rabbit VX2 model was used to evaluate the biosafety, doxorubicin penetration, local tumor response, tumor metastasis, and survival benefit of RLX combined with TACE treatment.

RESULTS

RLX did not affect the proliferation, migration, or invasion of HCCLM3 and Huh-7 cells, and the expression of E-cadherin and HIF-1α also remained unchanged while the MMP-9 protein was upregulated in vitro. In the rabbit VX2 model, compared to the normal saline group (NS), RLX group (RLX) and TACE mono-therapy group (TACE), the group that received TACE combined with RLX (TACE + RLX) showed an improved local tumor response and survival benefit. Furthermore, TACE combined with RLX was found to reduce tumor metastasis. This combination therapy reduced the fibrotic extracellular matrix in the tumor microenvironment, allowing for better penetration of doxorubicin, improved infiltration of CD8+ T cells and affected the secretion of cytokines. Additionally, RLX combined with TACE was able to decrease the expression of HIF-1α and PD-L1. The biosafety of TACE combined with RLX was also confirmed.

CONCLUSION

RLX synergized with TACE by mitigating the fibrotic extracellular matrix and tumor hypoxic microenvironment, improving the therapeutic effect and inhibiting metastasis during the treatment of liver cancer.

Modulating the immune system towards a functional chronic wound healing: A biomaterials and Nanomedicine perspective

Chronic non-healing wounds persist as a substantial burden for healthcare systems, influenced by factors such as aging, diabetes, and obesity. In contrast to the traditionally pro-regenerative emphasis of therapies, the recognition of the immune system integral role in wound healing has significantly grown, instigating an approach shift towards immunological processes. Thus, this review explores the wound healing process, highlighting the engagement of the immune system, and delving into the behaviors of innate and adaptive immune cells in chronic wound scenarios. Moreover, the article investigates biomaterial-based strategies for the modulation of the immune system, elucidating how the adjustment of their physicochemical properties or their synergistic combination with other agents such as drugs, proteins or mesenchymal stromal cells can effectively modulate the behaviors of different immune cells. Finally this review explores various strategies based on synthetic and biological nanostructures, including extracellular vesicles, to finely tune the immune system as natural immunomodulators or therapeutic nanocarriers with promising biophysical properties.

Structure-Mechanics Principles and Mechanobiology of Fibrocartilage Pericellular Matrix: A Pivotal Role of Type V Collagen

The pericellular matrix (PCM) is the immediate microniche surrounding resident cells in various tissue types, regulating matrix turnover, cell-matrix cross-talk and disease initiation. This study elucidated the structure-mechanical properties and mechanobiological functions of the PCM in fibrocartilage, a family of connective tissues that sustain complex tensile and compressive loads in vivo. Studying the murine meniscus as the model tissue, we showed that fibrocartilage PCM contains thinner, random collagen fibrillar networks that entrap proteoglycans, a structure distinct from the densely packed, highly aligned collagen fibers in the bulk extracellular matrix (ECM). In comparison to the ECM, the PCM has a lower modulus and greater isotropy, but similar relative viscoelastic properties. In Col5a1 +/- menisci, the reduction of collagen V, a minor collagen localized in the PCM, resulted in aberrant fibril thickening with increased heterogeneity. Consequently, the PCM exhibited a reduced modulus, loss of isotropy and faster viscoelastic relaxation. This disrupted PCM contributes to perturbed mechanotransduction of resident meniscal cells, as illustrated by reduced intracellular calcium signaling, as well as upregulated biosynthesis of lysyl oxidase and tenascin C. When cultured in vitro, Col5a1 +/- meniscal cells synthesized a weakened nascent PCM, which had inferior properties towards protecting resident cells against applied tensile stretch. These findings underscore the PCM as a distinctive microstructure that governs fibrocartilage mechanobiology, and highlight the pivotal role of collagen V in PCM function. Targeting the PCM or its molecular constituents holds promise for enhancing not only meniscus regeneration and osteoarthritis intervention, but also addressing diseases across various fibrocartilaginous tissues.

Aging and homeostasis of the hypodermis in the age-related deterioration of skin function

Adipose tissues in the hypodermis, the crucial stem cell reservoir in the skin and the endocrine organ for the maintenance of skin homeostasis undergo significant changes during skin aging. Dermal white adipose tissue (dWAT) has recently been recognized as an important organ for both non-metabolic and metabolic health in skin regeneration and rejuvenation. Defective differentiation, adipogenesis, improper adipocytokine production, and immunological dissonance dysfunction in dWAT lead to age-associated clinical changes. Here, we review age-related alterations in dWAT across levels, emphasizing the mechanisms underlying the regulation of aging. We also discuss the pathogenic changes involved in age-related fat dysfunction and the unfavorable consequences of accelerated skin aging, such as chronic inflammaging, immunosenescence, delayed wound healing, and fibrosis. Research has shown that adipose aging is an early initiation event and a potential target for extending longevity. We believe that adipose tissues play an essential role in aging and form a potential therapeutic target for the treatment of age-related skin diseases. Further research is needed to improve our understanding of this phenomenon.

Delivery technologies for therapeutic targeting of fibronectin in autoimmunity and fibrosis applications

Fibronectin (FN) is a critical component of the extracellular matrix (ECM) contributing to various physiological processes, including tissue repair and immune response regulation. FN regulates various cellular functions such as adhesion, proliferation, migration, differentiation, and cytokine release. Alterations in FN expression, deposition, and molecular structure can profoundly impact its interaction with other ECM proteins, growth factors, cells, and associated signaling pathways, thus influencing the progress of diseases such as fibrosis and autoimmune disorders. Therefore, developing therapeutics that directly target FN or its interaction with cells and other ECM components can be an intriguing approach to address autoimmune and fibrosis pathogenesis.

Biophysical and biochemical aspects of immune cell-tumor microenvironment interactions

The tumor microenvironment (TME), composed of and influenced by a heterogeneous set of cancer cells and an extracellular matrix, plays a crucial role in cancer progression. The biophysical aspects of the TME (namely, its architecture and mechanics) regulate interactions and spatial distributions of cancer cells and immune cells. In this review, we discuss the factors of the TME-notably, the extracellular matrix, as well as tumor and stromal cells-that contribute to a pro-tumor, immunosuppressive response. We then discuss the ways in which cells of the innate and adaptive immune systems respond to tumors from both biochemical and biophysical perspectives, with increased focus on CD8+ and CD4+ T cells. Building upon this information, we turn to immune-based antitumor interventions-specifically, recent biophysical breakthroughs aimed at improving CAR-T cell therapy.

Laminin-derived peptide, IKVAV, modulates macrophage phenotype through integrin mediation

Macrophages are highly plastic immune cells known to exist on a spectrum of phenotypes including pro-inflammatory (M1) or pro-healing (M2). Macrophages interact with extracellular matrix (ECM) ligands, such as fragments of collagen and laminin. Interaction of macrophages with ECM ligands is mediated through integrin receptors. However, the role of ECM ligands in directing macrophage function through integrins is not yet fully understood. Particularly, α2β1 has been implicated in modulating macrophage function, but complexity in mechanisms employed for integrin-ligation especially with laminin-derived peptides makes it challenging to understand macrophage-ECM interactions. We hypothesize that targeting α2β1 through laminin-derived peptide, IKVAV, will modulate macrophage phenotype. In this work we: i) investigated macrophage response to IKVAV in 2D and in a 3D platform, and ii) identified α2β1's role as it pertains to macrophage modulation via IKVAV. Soluble IKVAV treatment significantly reduced M1 markers and increased M2 markers via immunocytochemistry and gene expression. While the 3D ECM-mimicking PEG-IKVAV hydrogels did not have significant effects in modulating macrophage phenotype, we found that macrophage modulation via IKVAV is dependent on the concentration of peptide used and duration of exposure. To investigate integrin-ligand interactions for macrophages, α2β1 signaling was modulated by antagonists and agonists. We observed that blocking α2β1 reduces M1 activation. To understand integrin-ligand interactions and leveraging the therapeutic ability of macrophages in designing immunomodulatory solutions, it is critical to elucidate IKVAV's role in mediating macrophage phenotype.

Harnessing IL-10 induced anti-inflammatory response in maturing macrophages in presence of electrospun dexamethasone-loaded PLLA scaffold

The ultimate goal of tissue engineering is to repair and regenerate damaged tissue or organ. Achieving this goal requires blood vessel networks to supply oxygen and nutrients to new forming tissues. Macrophages are part of the immune system whose behavior plays a significant role in angiogenesis and blood vessel formation. On the other hand, macrophages are versatile cells that change their behavior in response to environmental stimuli. Given that implantation of a biomaterial is followed by inflammation; therefore, we reasoned that this inflammatory condition in tissue spaces modulates the final phenotype of macrophages. Also, we hypothesized that anti-inflammatory glucocorticoid dexamethasone improves modulating macrophages behavior. To check these concepts, we investigated the macrophages that had matured in an inflammatory media. Furthermore, we examined macrophages' behavior after maturation on a dexamethasone-containing scaffold and analyzed how the behavioral change of maturing macrophages stimulates other macrophages in the same environment. In this study, the expression of pro-inflammatory markers TNFa and NFκB1 along with pro-healing markers IL-10 and CD163 were investigated to study the behavior of macrophages. Our results showed that macrophages that were matured in the inflammatory media in vitro increase expression of IL-10, which in turn decreased the expression of pro-inflammatory markers TNFa and NFκB in maturing macrophages. Also, macrophages that were matured on dexamethasone-containing scaffolds decreased the expression of IL-10, TNFa, and NFκB and increase the expression of CD163 compared to the control group. Moreover, the modulation of anti-inflammatory response in maturing macrophages on dexamethasone-containing scaffold resulted in increased expression of TNFa and CD163 by other macrophages in the same media. The results obtained in this study, proposing strategies to improve healing through controlling the behavior of maturing macrophages and present a promising perspective for inflammation control using tissue engineering scaffolds.

In vivo micro-computed tomography evaluation of radiopaque, polymeric device degradation in normal and inflammatory environments

Polymeric biomedical implants are an important clinical tool, but degradation remains difficult to determine post-implantation. Computed tomography (CT) could be a powerful tool for device monitoring, but polymers require incorporation of radiopaque contrast agents to be distinguishable from tissue. In addition, immune response to radiopaque devices must be characterized as it modulates device function. Radiopaque devices and films were produced by incorporating 0-20 wt% TaOx nanoparticles into polymers: polycaprolactone (PCL) and poly(lactide-co-glycolide) (PLGA). In vitro inflammatory responses of mouse bone marrow-derived macrophages to polymer matrix incorporating TaOx nanoparticles was determined by monitoring cytokine secretion. Nanoparticle addition stimulated a slight inflammatory reaction, increasing TNFα secretion, mediated by changes in polymer matrix properties. Subsequently, devices (PLGA 50:50 + 20 wt% TaOx) were implanted subcutaneously in a mouse model of chronic inflammation, that featured a sustained increase in inflammatory response local to the implant site over 12 weeks. No changes to device degradation rates or foreign body response were noted between a normal and chronically stimulated inflammatory environment. Serial CT device monitoring post-implantation provided a detailed timeline of device collapse, with no rapid, spontaneous release of nanoparticles that occluded matrix visualization. Importantly, repeat CT sessions did not ablate the immune system or alter degradation kinetics. Thus, polymer devices incorporating radiopaque nanoparticles can be used for in situ monitoring and be readily combined with other medical imaging techniques, for a dynamic view biomaterial and tissue interactions. STATEMENT OF SIGNIFICANCE: A growing number of implantable devices are in use in the clinic, exposing patients to inherent risks of implant movement, collapse, and infection. The ability to monitor implanted devices would enable faster diagnosis of failure and open the door for personalized rehabilitation therapies - both of which could vastly improve patient outcomes. Unfortunately, polymeric materials which make up most biomedical devices are not radiologically distinguishable from tissue post-implantation. The introduction of radiopaque nanoparticles into polymers allows for serial monitoring via computed tomography, without affecting device degradation. Here we demonstrate for the first time that nanoparticles do not undergo burst release from devices post-implantation and that inflammatory responses - a key determinant of device function in vivo - are also unaffected by nanoparticle addition.

Macrophage-coated tumor cluster aggravates hepatoma invasion and immunotherapy resistance via generating local immune deprivation

Immune checkpoint inhibitors (ICIs) represent a promising treatment for hepatocellular carcinoma (HCC) due to their capacity for abundant lymphocyte infiltration. However, some patients with HCC respond poorly to ICI therapy due to the presence of various immunosuppressive factors in the tumor microenvironment. Our research reveals that a macrophage-coated tumor cluster (MCTC) signifies a unique spatial structural organization in HCC correlating with diminished recurrence-free survival and overall survival in a total of 572 HCC cases from 3 internal cohorts and 2 independent external validation cohorts. Mechanistically, tumor-derived macrophage-associated lectin Mac-2 binding protein (M2BP) induces MCTC formation and traps immunocompetent cells at the edge of MCTCs to induce intratumoral cytotoxic T cell exclusion and local immune deprivation. Blocking M2BP with a Mac-2 antagonist might provide an effective approach to prevent MCTC formation, enhance T cell infiltration, and thereby improve the efficacy of ICI therapy in HCC.

Advanced Immunomodulatory Biomaterials for Therapeutic Applications

The multifaceted biological defense system modulating complex immune responses against pathogens and foreign materials plays a critical role in tissue homeostasis and disease progression. Recently developed biomaterials that can specifically regulate immune responses, nanoparticles, graphene, and functional hydrogels have contributed to the advancement of tissue engineering as well as disease treatment. The interaction between innate and adaptive immunity, collectively determining immune responses, can be regulated by mechanobiological recognition and adaptation of immune cells to the extracellular microenvironment. Therefore, applying immunomodulation to tissue regeneration and cancer therapy involves manipulating the properties of biomaterials by tailoring their composition in the context of the immune system. This review provides a comprehensive overview of how the physicochemical attributes of biomaterials determine immune responses, focusing on the physical properties that influence innate and adaptive immunity. This review also underscores the critical aspect of biomaterial-based immune engineering for the development of novel therapeutics and emphasizes the importance of understanding the biomaterials-mediated immunological mechanisms and their role in modulating the immune system.

Decellularized kidney extracellular matrix-based hydrogels for renal tissue engineering

Kidney regeneration is hindered by the limited pool of intrinsic reparative cells. Advanced therapies targeting renal regeneration have the potential to alleviate the clinical and financial burdens associated with kidney disease. Delivery systems for cells, extracellular vesicles, or growth factors aimed at enhancing regeneration can benefit from vehicles enabling targeted delivery and controlled release. Hydrogels, optimized to carry biological cargo while promoting regeneration, have emerged as promising candidates for this purpose. This study aims to develop a hydrogel from decellularized kidney extracellular matrix (DKECM) and explore its biocompatibility as a biomaterial for renal regeneration. The resulting hydrogel crosslinks with temperature and exhibits a high concentration of extracellular matrix. The decellularization process efficiently removes detergent residues, yielding a pathogen-free biomaterial that is non-hemolytic and devoid of α-gal epitope. Upon interaction with macrophages, the hydrogel induces differentiation into both pro-inflammatory and anti-inflammatory phenotypes, suggesting an adequate balance to promote biomaterial functionality in vivo. Renal progenitor cells encapsulated in the DKECM hydrogel demonstrate higher viability and proliferation than in commercial collagen-I hydrogels, while also expressing tubular cells and podocyte markers in long-term culture. Overall, the injectable biomaterial derived from porcine DKECM is anticipated to elicit minimal host reaction while fostering progenitor cell bioactivity, offering a potential avenue for enhancing renal regeneration in clinical settings. STATEMENT OF SIGNIFICANCE: The quest to improve treatments for kidney disease is crucial, given the challenges faced by patients on dialysis or waiting for transplants. Exciting new therapies combining biomaterials with cells can revolutionize kidney repair. In this study, researchers created a hydrogel from pig kidney. This gel could be used to deliver cells and other substances that help in kidney regeneration. Despite coming from pigs, it's safe for use in humans, with no harmful substances and reduced risk of immune reactions. Importantly, it promotes a balanced healing response in the body. This research not only advances our knowledge of kidney repair but also offers hope for more effective treatments for kidney diseases.

Cryogel microcarriers for sustained local delivery of growth factors to the brain

Neurotrophic growth factors such as glial cell line-derived neurotrophic factor (GDNF) and brain-derived neurotrophic factor (BDNF) have been considered as potential therapeutic candidates for neurodegenerative disorders due to their important role in modulating the growth and survival of neurons. However, clinical translation remains elusive, as their large size hinders translocation across the blood-brain barrier (BBB), and their short half-life in vivo necessitates repeated administrations. Local delivery to the brain offers a potential route to the target site but requires a suitable drug-delivery system capable of releasing these proteins in a controlled and sustained manner. Herein, we develop a cryogel microcarrier delivery system which takes advantage of the heparin-binding properties of GDNF and BDNF, to reversibly bind/release these growth factors via electrostatic interactions. Droplet microfluidics and subzero temperature polymerization was used to create monodisperse cryogels with varying degrees of negative charge and an average diameter of 20 μm. By tailoring the inclusion of 3-sulfopropyl acrylate (SPA) as a negatively charged moiety, the release duration of these two growth factors could be adjusted to range from weeks to half a year. 80% SPA cryogels and 20% SPA cryogels were selected to load GDNF and BDNF respectively, for the subsequent biological studies. Cell culture studies demonstrated that these cryogel microcarriers were cytocompatible with neuronal and microglial cell lines, as well as primary neural cultures. Furthermore, in vivo studies confirmed their biocompatibility after administration into the brain, as well as their ability to deliver, retain and release GDNF and BDNF in the striatum. Overall, this study highlights the potential of using cryogel microcarriers for long-term delivery of neurotrophic growth factors to the brain for neurodegenerative disorder therapeutics.

Regenerative inflammation: When immune cells help to re-build tissues

Inflammation is an essential immune response critical for responding to infection, injury and maintenance of tissue homeostasis. Upon injury, regenerative inflammation promotes tissue repair by a timed and coordinated infiltration of diverse cell types and the secretion of growth factors, cytokines and lipids mediators. Remarkably, throughout evolution as well as mammalian development, this type of physiological inflammation is highly associated with immunosuppression. For instance, regenerative inflammation is the consequence of an in situ macrophage polarization resulting in a transition from pro-inflammatory to anti-inflammatory/pro-regenerative response. Immune cells are the first responders upon injury, infiltrating the damaged tissue and initiating a pro-inflammatory response depleting cell debris and necrotic cells. After phagocytosis, macrophages undergo multiple coordinated metabolic and transcriptional changes allowing the transition and dictating the initiation of the regenerative phase. Differences between a highly efficient, complete ad integrum tissue repair, such as, acute skeletal muscle injury, and insufficient regenerative inflammation, as the one developing in Duchenne Muscular Dystrophy (DMD), highlight the importance of a coordinated response orchestrated by immune cells. During regenerative inflammation, these cells interact with others and alter the niche, affecting the character of inflammation itself and, therefore, the progression of tissue repair. Comparing acute muscle injury and chronic inflammation in DMD, we review how the same cells and molecules in different numbers, concentration and timing contribute to very different outcomes. Thus, it is important to understand and identify the distinct functions and secreted molecules of macrophages, and potentially other immune cells, during tissue repair, and the contributors to the macrophage switch leveraging this knowledge in treating diseases.

Mineralized collagen scaffolds for regenerative engineering applications

Collagen is a primary constituent of the tissue extracellular matrix. As a result, collagen has been a common component of tissue engineering biomaterials, including those to promote bone regeneration or to investigate cell-material interactions in the context of bone homeostasis or disease. This review summarizes key considerations regarding current state-of-the-art design and use of collagen biomaterials for these applications. We also describe strategic opportunities for collagen biomaterials to address a new era of challenges, including immunomodulation and appropriate consideration of sex and other patient characteristics in biomaterial design.

Modeling mechanical activation of macrophages during pulmonary fibrogenesis for targeted anti-fibrosis therapy

Pulmonary fibrosis is an often fatal lung disease. Immune cells such as macrophages were shown to accumulate in the fibrotic lung, but their contribution to the fibrosis development is unclear. To recapitulate the involvement of macrophages in the development of pulmonary fibrosis, we developed a fibrotic microtissue model with cocultured human macrophages and fibroblasts. We show that profibrotic macrophages seeded on topographically controlled stromal tissues became mechanically activated. The resulting co-alignment of macrophages, collagen fibers, and fibroblasts promoted widespread fibrogenesis in micro-engineered lung tissues. Anti-fibrosis treatment using pirfenidone disrupts the polarization and mechanical activation of profibrotic macrophages, leading to fibrosis inhibition. Pirfenidone inhibits the mechanical activation of macrophages by suppressing integrin αMβ2 and Rho-associated kinase 2. These results demonstrate a potential pulmonary fibrogenesis mechanism at the tissue level contributed by macrophages. The cocultured microtissue model is a powerful tool to study the immune-stromal cell interactions and the anti-fibrosis drug mechanism.

Beyond Encapsulation: Exploring Macrophage-Fibroblast Cross Talk in Implant-Induced Fibrosis

The foreign body response (FBR) and organ fibrosis are complex biological processes involving the interaction between macrophages and fibroblasts. Understanding the molecular mechanisms underlying macrophage-fibroblast cross talk is crucial for developing strategies to mitigate implant encapsulation, a major cause of implant failure. This article reviews the current knowledge on the role of macrophages and fibroblasts in the FBR and organ fibrosis, highlighting the similarities between these processes. The FBR is characterized by the formation of a fibrotic tissue capsule around the implant, leading to functional impairment. Various factors, including material properties such as surface chemistry, stiffness, and topography, influence the degree of encapsulation. Cross talk between macrophages and fibroblasts plays a critical role in both the FBR and organ fibrosis. However, the precise molecular mechanisms remain poorly understood. Macrophages secrete a wide range of cytokines that modulate fibroblast behavior such as abundant collagen deposition and myofibroblast differentiation. However, the heterogeneity of macrophages and fibroblasts and their dynamic behavior in different tissue environments add complexity to this cross talk. Experimental evidence from in vitro studies demonstrates the impact of material properties on macrophage cytokine secretion and fibroblast physiology. However, the correlation between in vitro response and in vivo encapsulation outcomes is not robust. Adverse outcome pathways (AOPs) offer a potential framework to understand and predict process complexity. AOPs describe causal relationships between measurable events leading to adverse outcomes, providing mechanistic insights for in vitro testing and predictive modeling. However, the development of an AOP for the FBR does require a comprehensive understanding of the molecular initiating events and key event relationships to identify which events are essential. In this article, we describe the current knowledge on macrophage-fibroblast cross talk in the FBR and discuss how targeted research can help build an AOP for implant-related fibrosis.

Bone-Targeted Nanoparticle Drug Delivery System-Mediated Macrophage Modulation for Enhanced Fracture Healing

Despite decades of progress, developing minimally invasive bone-specific drug delivery systems (DDS) to improve fracture healing remains a significant clinical challenge. To address this critical therapeutic need, nanoparticle (NP) DDS comprised of poly(styrene-alt-maleic anhydride)-b-poly(styrene) (PSMA-b-PS) functionalized with a peptide that targets tartrate-resistant acid phosphatase (TRAP) and achieves preferential fracture accumulation has been developed. The delivery of AR28, a glycogen synthase kinase-3 beta (GSK3β) inhibitor, via the TRAP binding peptide-NP (TBP-NP) expedites fracture healing. Interestingly, however, NPs are predominantly taken up by fracture-associated macrophages rather than cells typically associated with fracture healing. Therefore, the underlying mechanism of healing via TBP-NP is comprehensively investigated herein. TBP-NPAR28 promotes M2 macrophage polarization and enhances osteogenesis in preosteoblast-macrophage co-cultures in vitro. Longitudinal analysis of TBP-NPAR28 -mediated fracture healing reveals distinct spatial distributions of M2 macrophages, an increased M2/M1 ratio, and upregulation of anti-inflammatory and downregulated pro-inflammatory genes compared to controls. This work demonstrates the underlying therapeutic mechanism of bone-targeted NP DDS, which leverages macrophages as druggable targets and modulates M2 macrophage polarization to enhance fracture healing, highlighting the therapeutic benefit of this approach for fractures and bone-associated diseases.

Infrapatellar fat pad adipose tissue-derived macrophages display a predominant CD11c+CD206+ phenotype and express genotypes attributable to key features of OA pathogenesis

Objectives

In knee osteoarthritis (OA), macrophages are the most predominant immune cells that infiltrate synovial tissues and infrapatellar fat pads (IPFPs). Both M1 and M2 macrophages have been described, but their role in OA has not been fully investigated. Therefore, we investigated macrophage subpopulations in IPFPs and synovial tissues of knee OA patients and their correlation with disease severity, examined their transcriptomics, and tested for factors that influenced their polarization.

Methods

Synovial tissues and IPFPs were obtained from knee OA patients undergoing total knee arthroplasty. Macrophages isolated from these joint tissues were characterized via flow cytometry. Transcriptomic profiling of each macrophage subpopulations was performed using NanoString technology. Peripheral blood monocyte-derived macrophages (MDMs) were treated with synovial fluid and synovial tissue- and IPFP-conditioned media. Synovial fluid-treated MDMs were treated with platelet-rich plasma (PRP) and its effects on macrophage polarization were observed.

Results

Our findings show that CD11c+CD206+ macrophages were predominant in IPFPs and synovial tissues compared to other macrophage subpopulations (CD11c+CD206-, CD11c-CD206+, and CD11c-CD206- macrophages) of knee OA patients. The abundance of macrophages in IPFPs reflected those in synovial tissues but did not correlate with disease severity as determined from Mankin scoring of cartilage destruction. Our transcriptomics data demonstrated highly expressed genes that were related to OA pathogenesis in CD11c+CD206+ macrophages than CD11c+CD206-, CD11c-CD206+, and CD11c-CD206- macrophages. In addition, MDMs treated with synovial fluid, synovial tissue-conditioned media, or IPFP-conditioned media resulted in different polarization profiles of MDMs. IPFP-conditioned media induced increases in CD86+CD206+ MDMs, whereas synovial tissue-conditioned media induced increases in CD86+CD206- MDMs. Synovial fluid treatment (at 1:8 dilution) induced a very subtle polarization in each macrophage subpopulation. PRP was able to shift macrophage subpopulations and partially reverse the profiles of synovial fluid-treated MDMs.

Conclusion

Our study provides an insight on the phenotypes and genotypes of macrophages found in IPFPs and synovial tissues of knee OA patients. We also show that the microenvironment plays a role in driving macrophages to polarize differently and shifting macrophage profiles can be reversed by PRP.

Integrating osteoimmunology and nanoparticle-based drug delivery systems for enhanced fracture healing

Fracture healing is a complex interplay of molecular and cellular mechanisms lasting from days to weeks. The inflammatory phase is the first stage of fracture healing and is critical in setting the stage for successful healing. There has been growing interest in exploring the role of the immune system and novel therapeutic strategies, such as nanoparticle drug delivery systems in enhancing fracture healing. Advancements in nanotechnology have revolutionized drug delivery systems to the extent that they can modulate immune response during fracture healing by leveraging unique physiochemical properties. Therefore, understanding the intricate interactions between nanoparticle-based drug delivery systems and the immune response, specifically macrophages, is essential for therapeutic efficacy. This review provides a comprehensive overview of the relationship between the immune system and nanoparticles during fracture healing. Specifically, we highlight the influence of nanoparticle characteristics, such as size, surface properties, and composition, on macrophage activation, polarization, and subsequent immune responses. IMPACT STATEMENT: This review provides valuable insights into the interplay between fracture healing, the immune system, and nanoparticle-based drug delivery systems. Understanding nanoparticle-macrophage interactions can advance the development of innovative therapeutic approaches to enhance fracture healing, improve patient outcomes, and pave the way for advancements in regenerative medicine.

Microglia Polarization and Antiglioma Effects Fostered by Dual Cell Membrane-Coated Doxorubicin-Loaded Hexagonal Boron Nitride Nanoflakes

Microglial cells play a critical role in glioblastoma multiforme (GBM) progression, which is considered a highly malignant brain cancer. The activation of microglia can either promote or inhibit GBM growth depending on the stage of the tumor development and on the microenvironment conditions. The current treatments for GBM have limited efficacy; therefore, there is an urgent need to develop novel and efficient strategies for drug delivery and targeting: in this context, a promising strategy consists of using nanoplatforms. This study investigates the microglial response and the therapeutic efficacy of dual-cell membrane-coated and doxorubicin-loaded hexagonal boron nitride nanoflakes tested on human microglia and GBM cells. Obtained results show promising therapeutic effects on glioma cells and an M2 microglia polarization, which refers to a specific phenotype or activation state that is associated with anti-inflammatory and tissue repair functions, highlighted through proteomic analysis.

Macrophage-Derived Extracellular DNA Initiates Heterotopic Ossification

Heterotopic ossification (HO) severely affects people's lives; however, its pathological mechanism remains poorly understood. Although extracellular DNA (ecDNA) has been shown to play important roles in pathological calcification, its effects in HO development and progression remain unknown. The in vivo rat Achilles tendon injury model and in vitro collagen I calcification model were used to evaluate the effects of ecDNA in the ectopic calcifications and the main cell types involved in those pathological process. Histology, immunofluorescent staining, reverse transcriptase-polymerase chain reaction analysis and micro-computed tomography were used to identify the distribution of macrophage-derived ecDNA and elucidate their roles in HO. The results showed that the amount of ecDNA and ectopic calcification increased significantly and exhibited a strong correlation in the injured tendons of HO model compared with those of the controls, which was accompanied by a significantly increased number of M2 macrophages in the injured tendon. During in vitro co-culture experiments, M2 macrophages calcified the reconstituted type I collagen and ectopic bone collected from the injured tendons of HO rats, while those effects were inhibited by deoxyribonuclease. More importantly, deoxyribonuclease reversed the pathological calcification in the injured rat tendon HO model. The present study showed that ecDNA from M2 macrophages initiates pathological calcification in HO, and the elimination of ecDNA might be developed into a clinical strategy to prevent ectopic mineralization diseases. The use of deoxyribonuclease for the targeted degradation of ecDNA at affected tissue sites provides a potential solution to treat diseases associated with ectopic mineralization.

Regulation of alveolar macrophage death in pulmonary fibrosis: a review

Pulmonary fibrosis (PF) is a disease in which excessive extracellular matrix (ECM) accumulation occurs in pulmonary mesenchyme, which induces the destruction of alveolar structures and poor prognosis. Macrophage death is responsible for ECM accumulation after alveolar epithelial injury in PF. Depending on the local micro-environments, macrophages can be polarized to either classically activated (M1) or alternatively activated (M2) macrophage phenotypes. In general, M1 macrophages can promote inflammation and sterilization, stop the continuous damage process and prevent excessive repair, while M2 macrophages are anti-inflammatory and promote tissue repair, and excessive M2 macrophage activity may inhibit the absorption and degradation of ECM. Emerging evidence has revealed that death forms such as pyroptosis mediated by inflammasome affect polarization direction and ultimately lead to the development of PF. Pharmacological manipulation of macrophages death signals may serve as a logical therapeutic strategy for PF. This review will focus on the current state of knowledge regarding the regulation and underlying mechanisms of macrophages and their mediators in the influence of macrophage death on the development of PF. We expect to provide help in developing effective therapeutic strategies in clinical settings.

Metal ions: the unfading stars of bone regeneration-from bone metabolism regulation to biomaterial applications

In recent years, bone regeneration has emerged as a remarkable field that offers promising guidance for treating bone-related diseases, such as bone defects, bone infections, and osteosarcoma. Among various bone regeneration approaches, the metal ion-based strategy has surfaced as a prospective candidate approach owing to the extensive regulatory role of metal ions in bone metabolism and the diversity of corresponding delivery strategies. Various metal ions can promote bone regeneration through three primary strategies: balancing the effects of osteoblasts and osteoclasts, regulating the immune microenvironment, and promoting bone angiogenesis. In the meantime, the complex molecular mechanisms behind these strategies are being consistently explored. Moreover, the accelerated development of biomaterials broadens the prospect of metal ions applied to bone regeneration. This review highlights the potential of metal ions for bone regeneration and their underlying mechanisms. We propose that future investigations focus on refining the clinical utilization of metal ions using both mechanistic inquiry and materials engineering to bolster the clinical effectiveness of metal ion-based approaches for bone regeneration.

ECM-engineered electrospun fibers with an immune cascade effect for inhibiting tissue fibrosis

Tissue regeneration/fibrosis after injury is intricately regulated by the immune cascade reaction and extracellular matrix (ECM). Dysregulated cascade signal could jeopardize tissue homeostasis leading to fibrosis. Bioactive scaffolds mimicking natural ECM microstructure and chemistry could regulate the cascade reaction to achieve tissue regeneration. The current study constructed an ECM-engineered micro/nanofibrous scaffold using self-assembled nanofibrous collagen and decorin (DCN)-loaded microfibers to regulate the immune cascade reaction. The ECM-engineered scaffold promoted anti-inflammatory and pro-regenerative effects, M2 polarization of macrophages, by nanofibrous collagen. The ECM-engineered scaffold could release DCN to inhibit inflammation-associated fibrous angiogenesis. Yet, to prevent excessive M2 activity leading to tissue fibrosis, controlled release of DCN was expected to elicit M1 activity and achieve M1/M2 balance in the repair process. Regulated cascade reaction guided favorable crosstalk between macrophages, endothelial cells and fibroblasts by proximity. Additionally, decorin could also antagonize TGF-β1 via TGF-β/Smad3 pathway to suppress fibrotic activity of fibroblasts. Hence, ECM-engineered scaffolds could exert effective regulation of the immune cascade reaction by microstructure and DCN release and achieve the balance between tissue fibrosis and regeneration. STATEMENT OF SIGNIFICANCE: With the incidence of up to 74.6%, failed back surgery syndrome (FBSS) has been a lingering issue in spine surgery, which poses a heavy socio-economic burden to society. Epidural fibrosis is believed to be responsible for the onset of FBSS. Current biomaterial-based strategies treating epidural fibrosis mainly rely on physical barriers and unidirectional suppression of inflammation. Regulation of the immune cascade reaction for inhibiting fibrosis has not been widely studied. Based on the simultaneous regulation of M1/M2 polarization and intercellular crosstalk, the ECM-engineered micro/nanofibrous scaffolds constructed in the current study could exert an immune cascade effect to coordinate tissue regeneration and inhibit fibrosis. This finding makes a significant contribution in the development of a treatment for epidural fibrosis and FBSS.

In vivo Biomedical Imaging of Immune Tolerant, Radiopaque Nanoparticle-Embedded Polymeric Device Degradation

Biomedical implants remain an important clinical tool for restoring patient mobility and quality of life after trauma. While polymers are often used for devices, their degradation profile remains difficult to determine post-implantation. CT monitoring could be a powerful tool for in situ monitoring of devices, but polymers require the introduction of radiopaque contrast agents, like nanoparticles, to be distinguishable from native tissue. As device function is mediated by the immune system, use of radiopaque nanoparticles for serial monitoring therefore requires a minimal impact on inflammatory response. Radiopaque polymer composites were produced by incorporating 0-20wt% TaOx nanoparticles into synthetic polymers: polycaprolactone (PCL) and poly(lactide-co-glycolide) (PLGA). In vitro inflammatory response to TaOx was determined by monitoring mouse bone marrow derived macrophages on composite films. Nanoparticle addition stimulated only a slight inflammatory reaction, namely increased TNFα secretion, mediated by changes to the polymer matrix properties. When devices (PLGA 50:50 + 20wt% TaOx) were implanted subcutaneously in a mouse model of chronic inflammation, no changes to device degradation were noted although macrophage number was increased over 12 weeks. Serial CT monitoring of devices post-implantation provided a detailed timeline of device structural collapse, with no burst release of the nanoparticles from the implant. Changes to the device were not significantly altered with monitoring, nor was the immune system ablated when checked via blood cell count and histology. Thus, polymer devices incorporating radiopaque TaOx NPs can be used for in situ CT monitoring, and can be readily combined with multiple medical imaging techniques, for a truly dynamic view biomaterials interaction with tissues throughout regeneration, paving the way for a more structured approach to biomedical device design.

A Bidens pilosa L. Non-Polar Extract Modulates the Polarization of Human Macrophages and Dendritic Cells into an Anti-Inflammatory Phenotype

Different communities around the world traditionally use Bidens pilosa L. for medicinal purposes, mainly for its anti-inflammatory, antinociceptive, and antioxidant properties; it is used as an ingredient in teas or herbal medicines for the treatment of pain, inflammation, and immunological disorders. Several studies have been conducted that prove the immunomodulatory properties of this plant; however, it is not known whether the immunomodulatory properties of B. pilosa are mediated by its ability to modulate antigen-presenting cells (APCs) such as macrophages (MØs) and dendritic cells (DCs) (through polarization or the maturation state, respectively). Different polar and non-polar extracts and fractions were prepared from the aerial part of B. pilosa. Their cytotoxic and immunomodulatory effects were first tested on human peripheral blood mononuclear cells (PBMCs) and phytohemagglutinin (PHA)-stimulated PBMCs, respectively, via an MTT assay. Then, the non-cytotoxic plant extracts and fractions that showed the highest immunomodulatory activity were selected to evaluate their effects on human MØ polarization and DC maturation (cell surface phenotype and cytokine secretion) through multiparametric flow cytometry. Finally, the chemical compounds of the B. pilosa extract that showed the most significant immunomodulatory effects on human APCs were identified using gas chromatography coupled with mass spectrometry. The petroleum ether extract and the ethyl acetate and hydroalcoholic fractions obtained from B. pilosa showed low cytotoxicity and modulated the PHA-stimulated proliferation of PBMCs. Furthermore, the B. pilosa petroleum ether extract induced M2 polarization or a hybrid M1/M2 phenotype in MØs and a semi-mature status in DCs, regardless of exposure to a maturation stimulus. The immunomodulatory activity of the non-polar (petroleum ether) extract of B. pilosa on human PBMC proliferation, M2 polarization of MØs, and semi-mature status in DCs might be attributed to the low-medium polarity components in the extract, such as phytosterol terpenes and fatty acid esters.

Latest advances: Improving the anti-inflammatory and immunomodulatory properties of PEEK materials

Excellent biocompatibility, mechanical properties, chemical stability, and elastic modulus close to bone tissue make polyetheretherketone (PEEK) a promising orthopedic implant material. However, biological inertness has hindered the clinical applications of PEEK. The immune responses and inflammatory reactions after implantation would interfere with the osteogenic process. Eventually, the proliferation of fibrous tissue and the formation of fibrous capsules would result in a loose connection between PEEK and bone, leading to implantation failure. Previous studies focused on improving the osteogenic properties and antibacterial ability of PEEK with various modification techniques. However, few studies have been conducted on the immunomodulatory capacity of PEEK. New clinical applications and advances in processing technology, research, and reports on the immunomodulatory capacity of PEEK have received increasing attention in recent years. Researchers have designed numerous modification techniques, including drug delivery systems, surface chemical modifications, and surface porous treatments, to modulate the post-implantation immune response to address the regulatory factors of the mechanism. These studies provide essential ideas and technical preconditions for the development and research of the next generation of PEEK biological implant materials. This paper summarizes the mechanism by which the immune response after PEEK implantation leads to fibrous capsule formation; it also focuses on modification techniques to improve the anti-inflammatory and immunomodulatory abilities of PEEK. We also discuss the limitations of the existing modification techniques and present the corresponding future perspectives.

Macrophages and fibroblasts in foreign body reactions: How mechanical cues drive cell functions?

Biomaterials, when implanted in the human body, can induce a series of cell- and cytokine-related reactions termed foreign body reactions (FBRs). In the progression of FBRs, macrophages regulate inflammation and healing by polarizing to either a pro-inflammatory or pro-healing phenotype and recruit fibroblasts by secreting cytokines. Stimulated by the biomaterials, fibrotic capsule is formed eventually. The implant, along with its newly formed capsule, introduces various mechanical cues that influence cellular functions. Mechanosensing proteins, such as integrins or ion channels, transduce extracellular mechanical signals into cytoplasm biochemical signals in response to mechanical stimuli. Consequently, the morphology, migration mode, function, and polarization state of the cells are affected. Modulated by different intracellular signaling pathways and their crosstalk, the expression of fibrotic genes increases with fibroblast activation and fibroblast to myofibroblast transition under stiff or force stimuli. However, summarized in most current studies, the outcomes of macrophage polarization in the effect of different mechanical cues are inconsistent. The underlying mechanisms should be investigated with more advanced technology and considering more interfering aspects. Further research is needed to determine how to modulate the progression of fibrotic capsule formation in FBR artificially.

The miR-183/96/182 cluster is a checkpoint for resident immune cells and shapes the cellular landscape of the cornea

PURPOSE

The conserved miR-183/96/182 cluster (miR-183C) regulates both corneal sensory innervation and corneal resident immune cells (CRICs). This study is to uncover its role in CRICs and in shaping the corneal cellular landscape at a single-cell (sc) level.

METHODS

Corneas of naïve, young adult [2 and 6 months old (mo)], female miR-183C knockout (KO) mice and wild-type (WT) littermates were harvested and dissociated into single cells. Dead cells were removed using a Dead Cell Removal kit. CD45+ CRICs were enriched by Magnetic Activated Cell Sorting (MACS). scRNA libraries were constructed and sequenced followed by comprehensive bioinformatic analyses.

RESULTS

The composition of major cell types of the cornea stays relatively stable in WT mice from 2 to 6 mo, however the compositions of subtypes of corneal cells shift with age. Inactivation of miR-183C disrupts the stability of the major cell-type composition and age-related transcriptomic shifts of subtypes of corneal cells. The diversity of CRICs is enhanced with age. Naïve mouse cornea contains previously-unrecognized resident fibrocytes and neutrophils. Resident macrophages (ResMφ) adopt cornea-specific function by expressing abundant extracellular matrix (ECM) and ECM organization-related genes. Naïve cornea is endowed with partially-differentiated proliferative ResMφ and contains microglia-like Mφ. Resident lymphocytes, including innate lymphoid cells (ILCs), NKT and γδT cells, are the major source of innate IL-17a. miR-183C limits the diversity and polarity of ResMφ.

CONCLUSION

miR-183C serves as a checkpoint for CRICs and imposes a global regulation of the cellular landscape of the cornea.

Immunomodulatory contribution of mast cells to the regenerative biomaterial microenvironment

Bioactive immunomodulatory biomaterials have shown promise for influencing the immune response to promote tissue repair and regeneration. Macrophages and T cells have been associated with this response; however, other immune cell types have been traditionally overlooked. In this study, we investigated the role of mast cells in the regulation of the immune response to decellularized biomaterial scaffolds using a subcutaneous implant model. In mast cell-deficient mice, there was dysregulation of the expected M1 to M2 macrophage transition typically induced by the biomaterial scaffold. Polarization progression deviated in a sex-specific manner with an early transition to an M2 profile in female mice, while the male response was unable to properly transition past a pro-inflammatory M1 state. Both were reversed with adoptive mast cell transfer. Further investigation of the later-stage immune response in male mice determined a greater sustained pro-inflammatory gene expression profile, including the IL-1 cytokine family, IL-6, alarmins, and chemokines. These results highlight mast cells as another important cell type that influences the immune response to pro-regenerative biomaterials.

Macrophage-Derived Cathepsin S Remodels the Extracellular Matrix to Promote Liver Fibrogenesis

BACKGROUND & AIMS

Liver fibrosis is an intrinsic wound-healing response to chronic injury and the major cause of liver-related morbidity and mortality worldwide. However, no effective diagnostic or therapeutic strategies are available, owing to its poorly characterized molecular etiology. We aimed to elucidate the mechanisms underlying liver fibrogenesis.

METHODS

We performed a quantitative proteomic analysis of clinical fibrotic liver samples to identify dysregulated proteins. Further analyses were performed on the sera of 164 patients with liver fibrosis. Two fibrosis mouse models and several biochemical experiments were used to elucidate liver fibrogenesis.

RESULTS

We identified cathepsin S (CTSS) up-regulation as a central node for extracellular matrix remodeling in the human fibrotic liver by proteomic screening. Increased serum CTSS levels efficiently predicted liver fibrosis, even at an early stage. Secreted CTSS cleaved collagen 18A1 at its C-terminus, releasing endostatin peptide, which directly bound to and activated hepatic stellate cells via integrin α5β1 signaling, whereas genetic ablation of Ctss remarkably suppressed liver fibrogenesis via endostatin reduction in vivo. Further studies identified macrophages as the main source of hepatic CTSS, and splenectomy effectively attenuated macrophage infiltration and CTSS expression in the fibrotic liver. Pharmacologic inhibition of CTSS ameliorated liver fibrosis progression in the mouse models.

CONCLUSIONS

CTSS functions as a novel profibrotic factor by remodeling extracellular matrix proteins and may represent a promising target for the diagnosis and treatment of liver fibrosis.

Expression of tumor-associated macrophages and PD-L1 in patients with hepatocellular carcinoma and construction of a prognostic model

BACKGROUND

Hepatocellular carcinoma (HCC) is an inflammation-associated tumor involved in immune tolerance and evasion in the immune microenvironment. Immunotherapy can enhance the immune response of the body, break immune tolerance, and then recognize and kill tumor cells. The polarization homeostasis of M1 and M2 macrophages in tumor microenvironment (TME) is involved in the occurrence and development of tumors and has been considered a hot topic in tumor research. Programmed cell death ligand 1 (PD-L1) plays an important role in the polarity of TAM and affects the prognosis of HCC patients as a target of immunotherapy. To this end, efforts were hereby made to further explore the application value of PD-L1, M1 macrophages (CD86), and M2 macrophages (CD206) in the prognosis assessment of HCC, their correlation with immune cell infiltration in HCC tissues, and their bioenrichment function.

METHODS

The gene expression omnibus (GEO) and the Cancer Genome Atlas (TCGA) database were used to analyze the expression of PD-L1, CD86, and CD206 in different tumor tissues. The correlation between the expression of PD-L1, CD86, and CD206 and the infiltration of immune cells was analyzed using the Tumor Immune Estimation Resource (TIMER). The tissue specimens and clinicopathological data of hepatocellular carcinoma patients having undergone surgical treatment in our hospital were collected. Immunohistochemistry was used to verify the expression of PD-L1, CD86, and CD206, and analyze the relationship with clinicopathological features and prognosis of patients. Besides, nomogram was constructed to predict the overall survival (OS) of patients at 3 and 5 years. Finally, the protein-protein interaction network information was analyzed using STRING database, and GO analysis and KEGG (Kyoto Encyclopedia of Genes and Genomes) analysis were performed to study the biological functions of PD-L1, CD86, and CD206.

RESULT

Bioinformatics analysis found that PD-L1, CD86, and CD206 were underexpressed in various tumor tissues including liver cancer, while the present immunohistochemical detection found that PD-L1, CD86, and CD206 were overexpressed in liver cancer tissues. Expressions of PD-L1, CD86, and CD206 were positively correlated with the infiltration level of immune cells in liver cancer, while the expression of PD-L1 was positively correlated with the degree of tumor differentiation. Meanwhile, the expression level of CD206 was positively correlated with gender and preoperative hepatitis, and patients with high expression of PD-L1 or low expression of CD86 had poor prognosis. AJCC stage, preoperative hepatitis, and the expression levels of PD-L1 and CD86 in cancer tissues were independent risk factors affecting survival of patients after radical hepatoma surgery. KEGG pathway enrichment analysis showed that PD-L1 was significantly enriched in T cell aggregation and lymphocyte aggregation, and might be involved in the formation of T cell antigen receptor CD3 complex and cell membrane. Besides, CD86 was significantly enriched in positive regulation of cell adhesion, regulation of mononuclear cell proliferation, regulation of leukocyte proliferation, and transduction of T cell receptor signaling pathway, while CD206 was significantly enriched in type 2 immune response, cellular response to LPS, cellular response to LPS, and involvement in cellular response to LPS.

CONCLUSION

In conclusion, these results suggest that PD-L1, CD86, and CD206 may be involved not only in the occurrence and development of HCC, but also in immune regulation, indicating the potential role of PD-L1 and CD86 as potential biomarkers and new therapeutic targets for prognosis assessment of liver cancer.

Calreticulin: a multifunctional protein with potential therapeutic applications for chronic wounds

Calreticulin is recognized as a multifunctional protein that serves an essential role in diverse biological processes that include wound healing, modification and folding of proteins, regulation of the secretory pathway, cell motility, cellular metabolism, protein synthesis, regulation of gene expression, cell cycle regulation and apoptosis. Although the role of calreticulin as an endoplasmic reticulum-chaperone protein has been well described, several studies have demonstrated calreticulin to be a highly versatile protein with an essential role during wound healing. These features make it an ideal molecule for treating a complex, multifactorial diseases that require fine tuning, such as chronic wounds. Indeed, topical application of recombinant calreticulin to wounds in multiple models of wound healing has demonstrated remarkable pro-healing effects. Among them include enhanced keratinocyte and fibroblast migration and proliferation, induction of extracellular matrix proteins, recruitment of macrophages along with increased granulation tissue formation, all of which are important functions in promoting wound healing that are deregulated in chronic wounds. Given the high degree of diverse functions and pro-healing effects, application of exogenous calreticulin warrants further investigation as a potential novel therapeutic option for chronic wound patients. Here, we review and highlight the significant effects of topical application of calreticulin on enhancing wound healing and its potential as a novel therapeutic option to shift chronic wounds into healing, acute-like wounds.

Arrhenius-model-based degradable oligourethane hydrogels for controlled growth factor release

Biodegradable hydrogels are growing in demand to enable the delivery of biomolecules (e.g. growth factors) for regenerative medicine. This research investigated the resorption of an oligourethane/polyacrylic acid hydrogel, a biodegradable hydrogel which supports tissue regeneration. The Arrhenius model was used to characterize the resorption of the polymeric gels in relevant in vitro conditions, and the Flory-Rehner equation was used to correlate the volumetric swelling ratio with the extent of degradation. The study found that the swelling rate of the hydrogel follows the Arrhenius model at elevated temperatures, estimating degradation time in saline solution at 37°C to be between 5 and 13 months, serving as a preliminary approximation of degradation in vivo. The degradation products had low cytotoxicity towards endothelial cells, and the hydrogel supported stromal cell proliferation. Additionally, the hydrogels were able to release growth factors and maintain the biomolecules' bioactivity towards cell proliferation. The study of the vascular endothelial growth factor (VEGF) release from the hydrogel used a diffusion process model, showing that the electrostatic attraction between VEGF and the anionic hydrogel allowed for controlled and sustained VEGF release over three weeks. In a rat subcutaneous implant model, a selected hydrogel with desired degradation rates exhibited minimal foreign body response and supported M2a macrophage phenotype, and vascularization. The low M1 and high M2a macrophage phenotypes within the implants were associated with tissue integration. This research supports the use of oligourethane/polyacrylic acid hydrogels as a promising material for delivering growth factors and supporting tissue regeneration. STATEMENT OF SIGNIFICANCE: There is a need for degradable elastomeric hydrogels that can support the formation of soft tissues and minimize long-term foreign body responses. An Arrhenius model was used to estimate the relative breakdown of hydrogels, in-vitro. The results demonstrate that hydrogels made from a combination of poly(acrylic acid) and oligo-urethane diacrylates can be designed to resorb over defined periods ranging from months to years depending on the chemical formulation prescribed by the model. The hydrogel formulations also provided for different release profiles of growth factors, relevant to tissue regeneration. In-vivo, these hydrogels had minimal inflammatory effects and showed evidence of integration into the surrounding tissue. The hydrogel approach can help the field design a broader range of biomaterials for tissue regeneration.

Targeting endometrial inflammation in intrauterine adhesion ameliorates endometrial fibrosis by priming MSCs to secrete C1INH

Intrauterine adhesion (IUA) is a common cause of uterine infertility and its histopathologic characteristic is endometrial fibrosis. A shortage of stem cells in the endometrial basalis has been recognized as a common cause of IUA development because approximately 90% of patients suffer from IUA after endometrial injury. In this study, we provide evidence that persistent inflammation is the main contributor to endometrial fibrosis in IUA patients. We further found that treating an IUA-like mouse model with ITI-hUC-MSCs (hUC-MSCs reprogrammed by IL-1β, TNF-α and IFN-γ) significantly decreased endometrial inflammation and fibrosis. Mechanistically, high levels of complement 1 inhibitor (C1INH) secreted by ITI-hUC-MSCs prevented inflammation from inducing profibrotic CD301+ macrophage polarization by downregulating the JAK-STAT signaling pathway. In conclusion, persistent inflammation in the endometria of IUA patients provides macrophage polarization with a profibrotic niche to promote endometrial fibrosis, and the powerful immunomodulatory effects of ITI-hUC-MSCs improve the immune microenvironment of endometrial regeneration.

Modeling Mechanical Activation of Macrophages During Pulmonary Fibrogenesis for Targeted Anti-Fibrosis Therapy

Pulmonary fibrosis, as seen in idiopathic pulmonary fibrosis (IPF) and COVID-induced pulmonary fibrosis, is an often-fatal lung disease. Increased numbers of immune cells such as macrophages were shown to accumulate in the fibrotic lung, but it is unclear how they contribute to the development of fibrosis. To recapitulate the macrophage mechanical activation in the fibrotic lung tissue microenvironment, we developed a fibrotic microtissue model with cocultured human macrophages and fibroblasts. We show that profibrotic macrophages seeded on topographically controlled stromal tissue constructs become mechanically activated. The resulting co-alignment of macrophages, collagen fibers and fibroblasts promote widespread fibrogenesis in micro-engineered lung tissues. Anti-fibrosis treatment using pirfenidone disrupts the polarization and mechanical activation of profibrotic macrophages, leading to fibrosis inhibition. Pirfenidone inhibits the mechanical activation of macrophages by suppressing integrin αMβ2 (CD11b/CD18) and Rho-associated kinase 2, which is a previously unknown mechanism of action of the drug. Together, these results demonstrate a potential pulmonary fibrogenesis mechanism at the tissue level contributed by mechanically activated macrophages. We propose the coculture, force-sensing microtissue model as a powerful tool to study the complex immune-stromal cell interactions and the mechanism of action of anti-fibrosis drugs.

Mechanosensory feedback loops during chronic inflammation

Epithelial tissues are crucial to maintaining healthy organization and compartmentalization in various organs and act as a first line of defense against infection in barrier organs such as the skin, lungs and intestine. Disruption or injury to these barriers can lead to infiltration of resident or foreign microbes, initiating local inflammation. One often overlooked aspect of this response is local changes in tissue mechanics during inflammation. In this mini-review, we summarize known molecular mechanisms linking disruption of epithelial barrier function to mechanical changes in epithelial tissues. We consider direct mechanisms, such as changes in the secretion of extracellular matrix (ECM)-modulating enzymes by immune cells as well as indirect mechanisms including local activation of fibroblasts. We discuss how these mechanical changes can modulate local immune cell activity and inflammation and perturb epithelial homeostasis, further dysregulating epithelial barrier function. We propose that this two-way relationship between loss of barrier function and altered tissue mechanics can lead to a positive feedback loop that further perpetuates inflammation. We discuss this cycle in the context of several chronic inflammatory diseases, including inflammatory bowel disease (IBD), liver disease and cancer, and we present the modulation of tissue mechanics as a new framework for combating chronic inflammation.

Concentration Selection of Biofriendly Enzyme-Modified Gelatin Hydrogels for Periodontal Bone Regeneration

Periodontitis is challenging to cure radically due to its complex periodontal structure and particular microenvironment of dysbiosis and inflammation. However, with the assistance of various materials, cell osteogenic differentiation could be improved, and the ability of hard tissue regeneration could be enhanced. This study aimed to explore the appropriate concentration ratio of biofriendly transglutaminase-modified gelatin hydrogels for promoting periodontal alveolar bone regeneration. Through a series of characterization and cell experiments, we found that all the hydrogels possessed multi-space network structures and demonstrated their biocompatibility. In vivo and in vitro osteogenic differentiation experiments also confirmed that the group 40-5 (transglutaminase-gelatin concentration ratio) possessed a favorable osteogenic potential. In summary, we conclude that such hydrogel with a 40-5 concentration is most conducive to promoting periodontal bone reconstruction, which might be a new route to deal with the dilemma of clinical periodontal treatment.

Advances in Immunomodulatory Mechanisms of Mesenchymal Stem Cells-Derived Exosome on Immune Cells in Scar Formation

Pathological scars are the result of over-repair and excessive tissue proliferation of the skin injury. It may cause serious dysfunction, resulting in psychological and physiological burdens on the patients. Currently, mesenchymal stem cells-derived exosomes (MSC-Exo) displayed a promising therapeutic effect on wound repair and scar attenuation. But the regulatory mechanisms are opinions vary. In view of inflammation has long been proven as the initial factor of wound healing and scarring, and the unique immunomodulation mechanism of MSC-Exo, the utilization of MSC-Exo may be promising therapeutic for pathological scars. However, different immune cells function differently during wound repair and scar formation. The immunoregulatory mechanism of MSC-Exo would differ among different immune cells and molecules. Herein, this review gave a comprehensive summary of MSC-Exo immunomodulating different immune cells in wound healing and scar formation to provide basic theoretical references and therapeutic exploration of inflammatory wound healing and pathological scars.