Developing a pro-regenerative biomaterial scaffold microenvironment requires T helper 2 cells

Comparison of skeletal muscle decellularization protocols and recellularization with adipose-derived stem cells for tissue engineering

Decellularization is a novel technique employed for scaffold manufacturing, as a strategy for skeletal muscle (SM) tissue engineering applications. However, poor decellularization efficacy is still a problem for the use of decellularized scaffolds as truly biocompatible biomaterials. For recellularization, adipose-derived stem cells (ASCs) are a good option, due to their immunomodulatory and pro-regenerative capacity, but few studies have described their combination with muscle-decellularized matrices (mDMs). This work aimed to evaluate the efficiency of four multi-step decellularization protocols to produce mDMs and to investigate in vitro biocompatibility with ASCs. Here, we described the different efficacies of muscle decellularization methods, suggesting the need for stricter standardization of the method, considering the large range of applications in SM tissue engineering, which is also a promising platform for preclinical studies with rat disease models using autologous cells.

Neutrophil Extracellular Traps in Breast Cancer: Roles in Metastasis and Beyond

Despite advances in the treatment of breast cancer, the disease continues to exhibit high global morbidity and mortality. The importance of neutrophils in cancer development has been increasingly recognized. Neutrophil extracellular traps (NETs) are web-like structures released into the extracellular space by activated neutrophils, serving as a potential antimicrobial mechanism for capturing and eliminating microorganisms. The roles played by NETs in cancer development have been a subject of intense research in the last decade. In breast cancer, current evidence suggests that NETs are involved in various stages of cancer development, particularly during metastasis. In this review, we try to provide an updated overview of the roles played by NETs in breast cancer metastasis. These include: 1) facilitating systemic dissemination of cancer cells; 2) promoting cancer-associated inflammation; 3) facilitating cancer-associated thrombosis; 4) facilitating pre-metastatic niche formation; and 5) awakening dormant cancer cells. The translational implications of NETs in breast cancer treatment are also discussed. Understanding the relationship between NETs and breast cancer metastasis is expected to provide important insights for developing new therapeutic strategies for breast cancer patients.

Macrophage Polarization Dynamics in Biomaterials: Implications for in Vitro Wound Healing

The interaction between biomaterials and the immune system plays a pivotal role in determining the success or failure of implantable devices. Macrophages, as key orchestrators of immune responses, exhibit diverse reactions that influence tissue integration or lead to implant failure. This study focuses on unraveling the intricate relationship between macrophage phenotypes and biomaterials, specifically hydrogels, by employing THP-1 cells as a model. Through a comprehensive investigation using polysaccharide, polymer, and protein-based hydrogels, our research sheds light on how the properties of hydrogels influence macrophage polarization. Phenotypic observations, biochemical assays, surface marker expression, and gene expression profiles collectively demonstrate the differential macrophage polarization abilities of polysaccharide-, polymer-, and protein-based hydrogels. Moreover, our indirect coculture studies reveal that hydrogels fostering M2 polarization exhibit exceptional wound-healing capabilities. These findings highlight the crucial role of the hydrogel microenvironment in adjusting macrophage polarization, offering a fresh avenue for refining biomaterials to bolster advantageous immune responses and improve tissue integration. This research contributes valuable insights for designing biomaterials with tailored properties that can guide macrophage behavior, ultimately improving the overall success of implantable devices.

Engineering Antigen-Specific Tolerance to an Artificial Protein Hydrogel

Artificial protein hydrogels are an emerging class of biomaterials with numerous prospective applications in tissue engineering and regenerative medicine. These materials are likely to be immunogenic due to their frequent incorporation of novel amino acid sequence domains, which often serve a functional role within the material itself. We engineered injectable "self" and "nonself" artificial protein hydrogels, which were predicted to have divergent immune outcomes in vivo on the basis of their primary amino acid sequence. Following implantation in mouse, the nonself gels raised significantly higher antigel antibody titers than the corresponding self gels. Prophylactic administration of a fusion antibody targeting the nonself hydrogel epitopes to DEC-205, an endocytic receptor involved in Treg induction, fully suppressed the elevated antibody titer against the nonself gels. These results suggest that the clinical immune response to artificial protein biomaterials, including those that contain highly antigenic sequence domains, can be tuned through the induction of antigen-specific tolerance.

Extracellular Matrix Scaffold-Assisted Tumor Vaccines Induce Tumor Regression and Long-Term Immune Memory

Injectable scaffold delivery is a strategy to enhance the efficacy of cancer vaccine immunotherapy. The choice of scaffold biomaterial is crucial, impacting both vaccine release kinetics and immune stimulation via the host response. Extracellular matrix (ECM) scaffolds prepared from decellularized tissues facilitate a pro-healing inflammatory response that promotes local cancer immune surveillance. Here, an ECM scaffold-assisted therapeutic cancer vaccine that maintains an immune microenvironment consistent with tissue reconstruction is engineered. Several immune-stimulating adjuvants are screened to develop a cancer vaccine formulated with decellularized small intestinal submucosa (SIS) ECM scaffold co-delivery. It is found that the STING pathway agonist cyclic di-AMP most effectively induces cytotoxic immunity in an ECM scaffold vaccine, without compromising key interleukin 4 (IL-4) mediated immune pathways associated with healing. ECM scaffold delivery enhances therapeutic vaccine efficacy, curing 50-75% of established E.G-7OVA lymphoma tumors in mice, while none are cured with soluble vaccine. SIS-ECM scaffold-assisted vaccination prolonged antigen exposure is dependent on CD8+ cytotoxic T cells and generates long-term antigen-specific immune memory for at least 10 months post-vaccination. This study shows that an ECM scaffold is a promising delivery vehicle to enhance cancer vaccine efficacy while being orthogonal to characteristics of pro-healing immune hallmarks.

Biomaterial engineering for cell transplantation

The current paradigm of medicine is mostly designed to block or prevent pathological events. Once the disease-led tissue damage occurs, the limited endogenous regeneration may lead to depletion or loss of function for cells in the tissues. Cell therapy is rapidly evolving and influencing the field of medicine, where in some instances attempts to address cell loss in the body. Due to their biological function, engineerability, and their responsiveness to stimuli, cells are ideal candidates for therapeutic applications in many cases. Such promise is yet to be fully obtained as delivery of cells that functionally integrate with the desired tissues upon transplantation is still a topic of scientific research and development. Main known impediments for cell therapy include mechanical insults, cell viability, host's immune response, and lack of required nutrients for the transplanted cells. These challenges could be divided into three different steps: 1) Prior to, 2) during the and 3) after the transplantation procedure. In this review, we attempt to briefly summarize published approaches employing biomaterials to mitigate the above technical challenges. Biomaterials are offering an engineerable platform that could be tuned for different classes of cell transplantation to potentially enhance and lengthen the pharmacodynamics of cell therapies.

Recent Biomaterial-Assisted Approaches for Immunotherapeutic Inhibition of Cancer Recurrence

Biomaterials possess distinctive properties, notably their ability to encapsulate active biological products while providing biocompatible support. The immune system plays a vital role in preventing cancer recurrence, and there is considerable demand for an effective strategy to prevent cancer recurrence, necessitating effective strategies to address this concern. This review elucidates crucial cellular signaling pathways in cancer recurrence. Furthermore, it underscores the potential of biomaterial-based tools in averting or inhibiting cancer recurrence by modulating the immune system. Diverse biomaterials, including hydrogels, particles, films, microneedles, etc., exhibit promising capabilities in mitigating cancer recurrence. These materials are compelling candidates for cancer immunotherapy, offering in situ immunostimulatory activity through transdermal, implantable, and injectable devices. They function by reshaping the tumor microenvironment and impeding tumor growth by reducing immunosuppression. Biomaterials facilitate alterations in biodistribution, release kinetics, and colocalization of immunostimulatory agents, enhancing the safety and efficacy of therapy. Additionally, how the method addresses the limitations of other therapeutic approaches is discussed.

The role of the skin microbiome in wound healing

The efficient management of skin wounds for rapid and scarless healing represents a major clinical unmet need. Nonhealing skin wounds and undesired scar formation impair quality of life and result in high healthcare expenditure worldwide. The skin-colonizing microbiota contributes to maintaining an intact skin barrier in homeostasis, but it also participates in the pathogenesis of many skin disorders, including aberrant wound healing, in many respects. This review focuses on the composition of the skin microbiome in cutaneous wounds of different types (i.e. acute and chronic) and with different outcomes (i.e. nonhealing and hypertrophic scarring), mainly based on next-generation sequencing analyses; furthermore, we discuss the mechanistic insights into host-microbe and microbe-microbe interactions during wound healing. Finally, we highlight potential therapeutic strategies that target the skin microbiome to improve healing outcomes.

Intersection of Immunity, Metabolism, and Muscle Regeneration in an Autoimmune-Prone MRL Mouse Model

Due to the limited capacity of mammals to regenerate complex tissues, researchers have worked to understand the mechanisms of tissue regeneration in organisms that maintain that capacity. One example is the MRL/MpJ mouse strain with unique regenerative capacity in ear pinnae that is absent from other strains, such as the common C57BL/6 strain. The MRL/MpJ mouse has also been associated with an autoimmune phenotype even in the absence of the mutant Fas gene described in its parent strain MRL/lpr. Due to these findings, the differences between the responses of MRL/MpJ versus C57BL/6 strain are evaluated in volumetric muscle injury and subsequent material implantation. One salient feature of the MRL/MpJ response to injury is robust adipogenesis within the muscle. This is associated with a decrease in M2-like polarization in response to biologically derived extracellular matrix scaffolds. In pro-fibrotic materials, such as polyethylene, there are fewer foreign body giant cells in the MRL/MpJ mice. As there are reports of both positive and negative influences of adipose tissue and adipogenesis on wound healing, this model can provide an important lens to investigate the interplay between stem cells, adipose tissue, and immune responses in trauma and material implantation.

Myocardial Matrix Hydrogels Mitigate Negative Remodeling and Improve Function in Right Heart Failure Model

This study evaluates the effectiveness of myocardial matrix (MM) hydrogels in mitigating negative right ventricular (RV) remodeling in a rat model of RV heart failure. The goal was to assess whether a hydrogel derived from either the right or left ventricle could promote cardiac repair. Injured rat right ventricles were injected with either RV-or left ventricular-derived MM hydrogels. Both hydrogels improved RV function and morphology and reduced negative remodeling. This study supports the potential of injectable biomaterial therapies for treating RV heart failure.

Biphasic calcium phosphate recruits Tregs to promote bone regeneration

The use of bone substitute materials is crucial for the healing of large bone defects. Immune response induced by bone substitute materials is essential in bone regeneration. Prior research has mainly concentrated on innate immune cells, such as macrophages. Existing research suggests that T lymphocytes, as adaptive immune cells, play an indispensable role in bone regeneration. However, the mechanisms governing T cell recruitment and specific subsets that are essential for bone regeneration remain unclear. This study demonstrates that CD4+ T cells are indispensable for ectopic osteogenesis by biphasic calcium phosphate (BCP). Subsequently, the recruitment of CD4+ T cells is closely associated with the activation of calcium channels in macrophages by BCP to release chemokines Ccl3 and Ccl17. Finally, these recruited CD4+ T cells are predominantly Tregs, which play a significant role in ectopic osteogenesis by BCP. These findings not only shed light on the immune-regenerative process after bone substitute material implantation but also establish a theoretical basis for developing bone substitute materials for promoting bone tissue regeneration. STATEMENT OF SIGNIFICANCE: Bone substitute material implantation is essential in the healing of large bone defects. Existing research suggests that T lymphocytes are instrumental in bone regeneration. However, the specific mechanisms governing T cell recruitment and specific subsets that are essential for bone regeneration remain unclear. In this study, we demonstrate that activation of calcium channels in macrophages by biphasic calcium phosphate (BCP) causes them to release the chemokines Ccl3 and Ccl17 to recruit CD4+ T cells, predominantly Tregs, which play a crucial role in ectopic osteogenesis by BCP. Our findings provide a theoretical foundation for developing bone substitute material for bone tissue regeneration.

Elastic porous microspheres/extracellular matrix hydrogel injectable composites releasing dual bio-factors enable tissue regeneration

Injectable biomaterials have garnered increasing attention for their potential and beneficial applications in minimally invasive surgical procedures and tissue regeneration. Extracellular matrix (ECM) hydrogels and porous synthetic polymer microspheres can be prepared for injectable administration to achieve in situ tissue regeneration. However, the rapid degradation of ECM hydrogels and the poor injectability and biological inertness of most polymeric microspheres limit their pro-regenerative capabilities. Here, we develop a biomaterial system consisting of elastic porous poly(l-lactide-co-ε-caprolactone) (PLCL) microspheres mixed with ECM hydrogels as injectable composites with interleukin-4 (IL-4) and insulin-like growth factor-1 (IGF-1) dual-release functionality. The developed multifunctional composites have favorable injectability and biocompatibility, and regulate the behavior of macrophages and myogenic cells following injection into muscle tissue. The elicited promotive effects on tissue regeneration are evidenced by enhanced neomusle formation, vascularization, and neuralization at 2-months post-implantation in a male rat model of volumetric muscle loss. Our developed system provides a promising strategy for engineering bioactive injectable composites that demonstrates desirable properties for clinical use and holds translational potential for application as a minimally invasive and pro-regenerative implant material in multiple types of surgical procedures.

Spatially Resolved Transcriptomes of CD30+-Transformed Mycosis Fungoides and Cutaneous Anaplastic Large-Cell Lymphoma

Mycosis fungoides with large-cell transformation (MF-LCT) occurs in a minor proportion of aggressive lesions, which express CD30 similar to primary cutaneous anaplastic large-cell lymphoma (pcALCL). We investigated the differences in spatially resolved transcriptome profiles of MF-LCT and pcALCL using CD30 morphology markers and 28 and 24 regions of interest (ROIs) in MF-LCT and pcALCL, respectively. Differentially expressed genes, pathway analysis, and immune-cell deconvolution by selective analysis of CD30-positive tumor cells and CD30-negative extratumoral areas were undertaken. In CD30-positive ROIs of MF-LCT, 190 differentially expressed genes were upregulated (29 were directly or indirectly associated with extracellular matrix remodeling), whereas 255 differentially expressed genes were downregulated, compared with those of pcALCL. Except for cornified envelope formation and keratinization, all six pathways enriched in CD30-positive ROIs of MF-LCT were associated with extracellular matrix remodeling. In CD30-positive ROIs in MF-LCT compared with those in pcALCL, immune-cell deconvolution revealed significantly increased fibroblasts and M2 macrophages (P = 0.012 and P = 0.023, respectively) but decreased M1 macrophages (P = 0.031). In CD30-negative ROIs in MF-LCT compared with those in pcALCL, memory B (P = 0.021), plasma (P = 0.023), and CD8 memory T (P = 0.001) cells significantly decreased, whereas regulatory T cells (P = 0.024) increased. Predomination of extracellular matrix remodeling pathways and immunosuppressive microenvironment in MF-LCT indicates pathophysiological differences between MF-LCT and pcALCL.

Matrix-bound nanovesicle-associated IL-33 supports functional recovery after skeletal muscle injury by initiating a pro-regenerative macrophage phenotypic transition

Injuries to skeletal muscle are among the most common injuries in civilian and military populations, accounting for nearly 60% of extremity injuries. The standard of care for severe extremity injury has been focused upon limb salvage procedures and the utilization of tissue grafts or orthotics in conjunction with rehabilitation to avoid amputation. Nonetheless, many patients have persistent strength and functional deficits that permanently impact their quality of life. Preclinical and clinical studies have shown that partial restoration of functional skeletal muscle tissue following injury can be achieved by the implantation of a biologic scaffold composed of extracellular matrix (ECM). These favorable outcomes are mediated, at least in part, through local immunomodulation. The mechanisms underlying this immunomodulatory effect, however, are poorly understood. The present study investigates a potential mechanistic driver of the immunomodulatory effects; specifically, the effect of selected ECM components upon inflammation resolution and repair. Results show that the host response to skeletal muscle injury is profoundly altered and functional recovery decreased in il33-/- mice compared to age- and sex-matched wildtype counterparts by 14 days post-injury. Results also show that IL-33, contained within matrix-bound nanovesicles (MBV), supports skeletal muscle regeneration by regulating local macrophage activation toward a pro-remodeling phenotype via canonical and non-canonical pathways to improve functional recovery from injury compared to untreated il33-/- counterparts. Taken together, these data suggest that MBV and their associated IL-33 cargo represent a novel homeostatic signaling mechanism that contributes to skeletal muscle repair.

Recent Advances in Implantable Biomaterials for the Treatment of Volumetric Muscle Loss

BACKGROUND

Volumetric muscle loss (VML) causes pain and disability in patients who sustain traumatic injury from invasive surgical procedures, vehicle accidents, and battlefield wounds. Clinical treatment of VML injuries is challenging, and although options such as free-flap autologous grafting exist, patients inevitably develop excessive scarring and fatty infiltration, leading to muscle weakness and reduced quality of life.

SUMMARY

New bioengineering approaches, including cell therapy, drug delivery, and biomaterial implantation, have emerged as therapies to restore muscle function and structure to pre-injury levels. Of these, acellular biomaterial implants have attracted wide interest owing to their broad potential design space and high translational potential as medical devices. Implantable biomaterials fill the VML defect and create a conduit that permits the migration of regenerative cells from the intact muscle tissue to the injury site. Invading cells and regenerating myofibers are sensitive to the biomaterial's structural and biochemical properties, which can play instructive roles in guiding cell fate and organization into functional tissue.

KEY MESSAGES

Many diverse biomaterials have been developed for skeletal muscle regeneration with variations in biophysical and biochemical properties, and while many have been tested in vitro, few have proven their regenerative potential in clinically relevant in vivo models. Here, we provide an overview of recent advances in the design, fabrication, and application of acellular biomaterials made from synthetic or natural materials for the repair of VML defects. We specifically focus on biomaterials with rationally designed structural (i.e., porosity, topography, alignment) and biochemical (i.e., proteins, peptides, growth factors) components, highlighting their regenerative effects in clinically relevant VML models.

Magnesium Ion-Doped Mesoporous Bioactive Glasses Loaded with Gallic Acid Against Myocardial Ischemia/Reperfusion Injury by Affecting the Biological Functions of Multiple Cells

Introduction

Excessive generation of reactive oxygen species (ROS) following myocardial ischemia-reperfusion (I/R) can result in additional death of myocardial cells. The rapid clearance of ROS after reperfusion injury and intervention during subsequent cardiac repair stages are crucial for the ultimate recovery of cardiac function.

Methods

Magnesium-doped mesoporous bioactive glasses were prepared and loaded with the antioxidant drug gallic acid into MgNPs by sol-gel method. The antioxidant effects of MgNPs/GA were tested for their pro-angiogenic and anti-inflammatory effects based on the release characteristics of GA and Mg2+ from MgNPs/GA. Later, we confirmed in our in vivo tests through immunofluorescence staining of tissue sections at various time points that MgNPs/GA exhibited initial antioxidant effects and had both pro-angiogenic and anti-inflammatory effects during the cardiac repair phase. Finally, we evaluated the cardiac function in mice treated with MgNPs/GA.

Results

We provide evidence that GA released by MgNPs/GA can effectively eliminate ROS in the early stage, decreasing myocardial cell apoptosis. During the subsequent cardiac repair phase, the gradual release of Mg2+ from MgNPs/GA stimulated angiogenesis and promoted M2 macrophage polarization, thereby reducing the release of inflammatory factors.

Conclusion

MgNPs/GA acting on multiple cell types is an integrated solution for comprehensive attenuation of myocardial ischaemia-reperfusion injury and cardiac function protection.

Synthetic injectable and porous hydrogels for the formation of skeletal muscle fibers: Novel perspectives for the acellular repair of substantial volumetric muscle loss

In severe skeletal muscle damage, muscle tissue regeneration process has to face the loss of resident muscle stem cells (MuSCs) and the lack of connective tissue necessary to guide the regeneration process. Biocompatible and standardized 3D structures that can be injected to the muscle injury site, conforming to the defect shape while actively guiding the repair process, holds great promise for skeletal muscle tissue regeneration. In this study, we explore the use of an injectable and porous lysine dendrimer/polyethylene glycol (DGL/PEG) hydrogel as an acellular support for skeletal muscle regeneration. We adjusted the DGL/PEG composition to achieve a stiffness conducive to the attachment and proliferation of murine immortalized myoblasts and human primary muscle stems cells, sustaining the formation and maturation of muscle fibers in vitro. We then evaluated the potential of one selected "myogenic-porous hydrogel" as a supportive structure for muscle repair in a large tibialis anterior muscle defect in rats. This injectable and porous formulation filled the defect, promoting rapid cellularization with the presence of endothelial cells, macrophages, and myoblasts, thereby supporting neo-myogenesis more specifically at the interface between the wound edges and the hydrogel. The selected porous DGL/PEG hydrogel acted as a guiding scaffold at the periphery of the defect, facilitating the formation and anchorage of aligned muscle fibers 21 days after injury. Overall, our results indicate DGL/PEG porous injectable hydrogel potential to create a pro-regenerative environment for muscle cells after large skeletal muscle injuries, paving the way for acellular treatment in regenerative muscle medicine.

Polarization of M2 Tumor-Associated Macrophages (TAMs) in Cancer Immunotherapy

We have witnessed in the last decade new milestones in the treatment of various resistant cancers with new immunotherapeutic modalities. These advances have resulted in significant objective durable clinical responses in a subset of cancer patients. These findings strongly suggested that immunotherapy should be considered for the treatment of all subsets of cancer patients. Accordingly, the mechanisms underlying resistance to immunotherapy must be explored and develop new means to target these resistant factors. One of the pivotal resistance mechanisms in the tumor microenvironment (TME) is the high infiltration of tumor-associated macrophages (TAMs) that are highly immunosuppressive and responsible, in large part, of cancer immune evasion. Thus, various approaches have been investigated to target the TAMs to restore the anti-tumor immune response. One approach is to polarize the M2 TAMS to the M1 phenotype that participates in the activation of the anti-tumor response. In this review, we discuss the various and differential properties of the M1 and M2 phenotypes, the molecular signaling pathways that participate in the polarization, and various approaches used to target the polarization of the M2 TAMs into the M1 anti-tumor phenotype. These approaches include inhibitors of histone deacetylases, PI3K inhibitors, STAT3 inhibitors, TLR agonists, and metabolic reprogramming. Clearly, due to the distinct features of various cancers and their heterogeneities, a single approach outlined above might only be effective against some cancers and not others. In addition, targeting by itself may not be efficacious unless used in combination with other therapeutic modalities.

ε-Poly-l-lysine-hydroxyphenyl propionic acid/IL-4 composite hydrogels with inflammation regulation and antibacterial activity for improving integration stability of soft tissues and orthopedic implants

The failure of orthopedic implants is usually caused by inflammation, poor tissue integration, and infection, which can lead to pain, limited mobility, dysfunction of patients. This may require additional surgical interventions, such as removal, replacement, or repair of implants, as well as related treatment measures such as antibiotic therapy, physical therapy. Here, an injectable hydrogel carrier was developed for the steady release of inflammatory regulators to reduce the surface tissue inflammatory response of orthopedic implants and induce soft tissue regeneration, ultimately achieving the promotion of implants stability. The hydrogels carrier was prepared by hydroxyphenyl propionic acid-modified ε-Poly-l-lysine (EPA), hydrogen peroxide and horseradish peroxidase, which showed antibacterial bioactive and stable factor release ability. Due to the introduction of IL-4, EPA@IL-4 hydrogels showed good inflammatory regulation. EPA@IL-4 hydrogels regulated the differentiation of macrophages into M2 in inflammatory environment in vitro, and promoted endothelial cells to show a more obvious trend of tube formation. The composite hydrogels reduced the inflammation on the surface of the implants in vivo, induced local endothelial cell angiogenesis, and had more collagen deposition and new granulation tissue. Therefore, EPA hydrogels based on IL-4 release are promising candidates for promoting of implants surface anti-inflammatory, soft tissue regeneration, and anti-infection.

Bone Marrow Mobilization and Local Stromal Cell-Derived Factor-1α Delivery Enhances Nascent Supraspinatus Muscle Fiber Growth

Rotator cuff tear is a significant problem that leads to poor clinical outcomes due to muscle degeneration after injury. The objective of this study was to synergistically increase the number of proregenerative cells recruited to injure rotator cuff muscle through a novel dual treatment system, consisting of a bone marrow mobilizing agent (VPC01091), hypothesized to "push" prohealing cells into the blood, and localized delivery of stromal cell-derived factor-1α (SDF-1α), to "pull" the cells to the injury site. Immediately after rotator cuff tendon injury in rat, the mobilizing agent was delivered systemically, and SDF-1α-loaded heparin-based microparticles were injected into the supraspinatus muscle. Regenerative and degenerative changes to supraspinatus muscle and the presence of inflammatory/immune cells, mesenchymal stem cells (MSCs), and satellite cells were assessed via flow cytometry and histology for up to 21 days. After dual treatment, significantly more MSCs (31.9 ± 8.0% single cells) and T lymphocytes (6.7 ± 4.3 per 20 × field of view) were observed in supraspinatus muscle 7 days after injury and treatment compared to injury alone (14.4 ± 6.5% single cells, 1.2 ± 0.7 per 20 × field of view), in addition to an elevated M2:M1 macrophage ratio (3.0 ± 0.5), an indicator of a proregenerative environment. These proregenerative cellular changes were accompanied by increased nascent fiber formation (indicated by embryonic myosin heavy chain staining) at day 7 compared to SDF-1α treatment alone, suggesting that this method may be a promising strategy to influence the early cellular response in muscle and promote a proregenerative microenvironment to increase muscle healing after severe rotator cuff tear.

Pro-regenerative biomaterials recruit immunoregulatory dendritic cells after traumatic injury

During wound healing and surgical implantation, the body establishes a delicate balance between immune activation to fight off infection and clear debris and immune tolerance to control reactivity against self-tissue. Nonetheless, how such a balance is achieved is not well understood. Here we describe that pro-regenerative biomaterials for muscle injury treatment promote the proliferation of a BATF3-dependent CD103+XCR1+CD206+CD301b+ dendritic cell population associated with cross-presentation and self-tolerance. Upregulation of E-cadherin, the ligand for CD103, and XCL-1 in injured tissue suggests a mechanism for cell recruitment to trauma. Muscle injury recruited natural killer cells that produced Xcl1 when stimulated with fragmented extracellular matrix. Without cross-presenting cells, T-cell activation increases, pro-regenerative macrophage polarization decreases and there are alterations in myogenesis, adipogenesis, fibrosis and increased muscle calcification. These results, previously observed in cancer progression, suggest a fundamental mechanism of immune regulation in trauma and material implantation with implications for both short- and long-term injury recovery.

Manganese Enhances the Osteogenic Effect of Silicon-Hydroxyapatite Nanowires by Targeting T Lymphocyte Polarization

Biomaterials encounter considerable challenges in extensive bone defect regeneration. The amelioration of outcomes may be attainable through the orchestrated modulation of both innate and adaptive immunity. Silicon-hydroxyapatite, for instance, which solely focuses on regulating innate immunity, is inadequate for long-term bone regeneration. Herein, extra manganese (Mn)-doping is utilized for enhancing the osteogenic ability by mediating adaptive immunity. Intriguingly, Mn-doping engenders heightened recruitment of CD4+ T cells to the bone defect site, concurrently manifesting escalated T helper (Th) 2 polarization and an abatement in Th1 cell polarization. This consequential immune milieu yields a collaborative elevation of interleukin 4, secreted by Th2 cells, coupled with attenuated interferon gamma, secreted by Th1 cells. This orchestrated interplay distinctly fosters the osteogenesis of bone marrow stromal cells and effectuates consequential regeneration of the mandibular bone defect. The modulatory mechanism of Th1/Th2 balance lies primarily in the indispensable role of manganese superoxide dismutase (MnSOD) and the phosphorylation of adenosine 5'-monophosphate-activated protein kinase (AMPK). In conclusion, this study highlights the transformative potential of Mn-doping in amplifying the osteogenic efficacy of silicon-hydroxyapatite nanowires by regulating T cell-mediated adaptive immunity via the MnSOD/AMPK pathway, thereby creating an anti-inflammatory milieu favorable for bone regeneration.

Stimuli-Responsive Nanoradiosensitizers for Enhanced Cancer Radiotherapy

Radiotherapy (RT) has been a classical therapeutic method of cancer for several decades. It attracts tremendous attention for the precise and efficient treatment of local tumors with stimuli-responsive nanomaterials, which enhance RT. However, there are few systematic reviews summarizing the newly emerging stimuli-responsive mechanisms and strategies used for tumor radio-sensitization. Hence, this review provides a comprehensive overview of recently reported studies on stimuli-responsive nanomaterials for radio-sensitization. It includes four different approaches for sensitized RT, namely endogenous response, exogenous response, dual stimuli-response, and multi stimuli-response. Endogenous response involves various stimuli such as pH, hypoxia, GSH, and reactive oxygen species (ROS), and enzymes. On the other hand, exogenous response encompasses X-ray, light, and ultrasound. Dual stimuli-response combines pH/enzyme, pH/ultrasound, and ROS/light. Lastly, multi stimuli-response involves the combination of pH/ROS/GSH and X-ray/ROS/GSH. By elaborating on these responsive mechanisms and applying them to clinical RT diagnosis and treatment, these methods can enhance radiosensitive efficiency and minimize damage to surrounding normal tissues. Finally, this review discusses the additional challenges and perspectives related to stimuli-responsive nanomaterials for tumor radio-sensitization.

Collagen biomaterials promote the regenerative repair of abdominal wall defects in Bama miniature pigs

Due to adhesion and rejection of recent traditional materials, it is still challenging to promote the regenerative repair of abdominal wall defects caused by different hernias or severe trauma. However, biomaterials with a high biocompatibility and low immunogenicity have exhibited great potential in the regeneration of abdominal muscle tissue. Previously, we have designed a biological collagen scaffold material combined with growth factor, which enables a fusion protein-collagen binding domain (CBD)-basic fibroblast growth factor (bFGF) to bind and release specifically. Though experiments in rodent animals have indicated the regeneration function of CBD-bFGF modified biological collagen scaffolds, its translational properties in large animals or humans are still in need of solid evidence. In this study, the abdominal wall defect model of Bama miniature pigs was established by artificial operations, and the defective abdominal wall was sealed with or without a polypropylene patch, and unmodified and CBD-bFGF modified biological collagen scaffolds. Results showed that a recurrent abdominal hernia was observed in the defect control group (without the use of mesh). Although the polypropylene patch can repair the abdominal wall defect, it also induced serious adhesion and inflammation. Meanwhile, both kinds of collagen biomaterials exhibited positive effects in repairing abdominal wall defects and reducing regional adhesion and inflammation. However, CBD-bFGF-modified collagen biomaterials failed to induce the regenerative repair reported in rat experiments. In addition, unmodified collagen biomaterials induced abdominal wall muscle regeneration rather than fibrotic repair. These results indicated that the unmodified collagen biomaterials are a better option among translational patches for the treatment of abdominal wall defects.

The foreign body response: emerging cell types and considerations for targeted therapeutics

The foreign body response (FBR) remains a clinical challenge in the field of biomaterials due to its ability to elicit a chronic and sustained immune response. Modulating the immune response to materials is a modern paradigm in tissue engineering to enhance repair while limiting fibrous encapsulation and implant isolation. Though the classical mediators of the FBR are well-characterized, recent studies highlight that our understanding of the cell types that shape the FBR may be incomplete. In this review, we discuss the emerging role of T cells, stromal-immune cell interactions, and senescent cells in the biomaterial response, particularly to synthetic materials. We emphasize future studies that will deepen the field's understanding of these cell types in the FBR, with the goal of identifying therapeutic targets that will improve implant integration. Finally, we briefly review several considerations that may influence our understanding of the FBR in humans, including rodent models, aging, gut microbiota, and sex differences. A better understanding of the heterogeneous host cell response during the FBR can enable the design and development of immunomodulatory materials that favor healing.

Extreme environments and human health: From the immune microenvironments to immune cells

Exposure to extreme environments causes specific acute and chronic physiological responses in humans. The adaptation and the physiological processes under extreme environments predominantly affect multiple functional systems of the organism, in particular, the immune system. Dysfunction of the immune system affected by several extreme environments (including hyperbaric environment, hypoxia, blast shock, microgravity, hypergravity, radiation exposure, and magnetic environment) has been observed from clinical macroscopic symptoms to intracorporal immune microenvironments. Therefore, simulated extreme conditions are engineered for verifying the main influenced characteristics and factors in the immune microenvironments. This review summarizes the responses of immune microenvironments to these extreme environments during in vivo or in vitro exposure, and the approaches of engineering simulated extreme environments in recent decades. The related microenvironment engineering, signaling pathways, molecular mechanisms, clinical therapy, and prevention strategies are also discussed.

Senolytic treatment reduces oxidative protein stress in an aging male murine model of post-traumatic osteoarthritis

Senolytic drugs are designed to selectively clear senescent cells (SnCs) that accumulate with injury or aging. In a mouse model of osteoarthritis (OA), senolysis yields a pro-regenerative response, but the therapeutic benefit is reduced in aged mice. Increased oxidative stress is a hallmark of advanced age. Therefore, here we investigate whether senolytic treatment differentially affects joint oxidative load in young and aged animals. We find that senolysis by a p53/MDM2 interaction inhibitor, UBX0101, reduces protein oxidative modification in the aged arthritic knee joint. Mass spectrometry coupled with protein interaction network analysis and biophysical stability prediction of extracted joint proteins revealed divergent responses to senolysis between young and aged animals, broadly suggesting that knee regeneration and cellular stress programs are contrarily poised to respond as a function of age. These opposing responses include differing signatures of protein-by-protein oxidative modification and abundance change, disparate quantitative trends in modified protein network centrality, and contrasting patterns of oxidation-induced folding free energy perturbation between young and old. We develop a composite sensitivity score to identify specific key proteins in the proteomes of aged osteoarthritic joints, thereby nominating prospective therapeutic targets to complement senolytics.

Ectopic adipogenesis in response to injury and material implantation in an autoimmune mouse model

Due to the limited capacity of mammals to regenerate complex tissues, researchers have worked to understand the mechanisms of tissue regeneration in organisms that maintain that capacity. One example is the MRL/MpJ mouse strain with unique regenerative capacity in ear pinnae that is absent from other strains, such as the common C57BL/6 strain. The MRL/MpJ mouse has also been associated with an autoimmune phenotype even in the absence of the mutant Fas gene described in its parent strain MRL/lpr. Due to these findings, we evaluated the differences between the responses of MRL/MpJ versus C57BL/6 strain in traumatic muscle injury and subsequent material implantation. One salient feature of the MRL/MpJ response to injury was a robust adipogenesis within the muscle. This was associated with a decrease in M2-like polarization in response to biologically derived extracellular matrix scaffolds. In pro-fibrotic materials, such as polyethylene, there were fewer foreign body giant cells in the MRL/MpJ mice. As there are reports of both positive and negative influences of adipose tissue and adipogenesis on wound healing, this model could provide an important lens to investigate the interplay between stem cells, adipose tissue, and immune responses in trauma and materials implantation.

Macrophages and fibrosis: how resident and infiltrating mononuclear phagocytes account for organ injury, regeneration or atrophy

Mononuclear phagocytes (MP), i.e., monocytes, macrophages, and dendritic cells (DCs), are essential for immune homeostasis via their capacities to clear pathogens, pathogen components, and non-infectious particles. However, tissue injury-related changes in local microenvironments activate resident and infiltrating MP towards pro-inflammatory phenotypes that contribute to inflammation by secreting additional inflammatory mediators. Efficient control of injurious factors leads to a switch of MP phenotype, which changes the microenvironment towards the resolution of inflammation. In the same way, MP endorses adaptive structural responses leading to either compensatory hypertrophy of surviving cells, tissue regeneration from local tissue progenitor cells, or tissue fibrosis and atrophy. Under certain circumstances, MP contribute to the reversal of tissue fibrosis by clearance of the extracellular matrix. Here we give an update on the tissue microenvironment-related factors that, upon tissue injury, instruct resident and infiltrating MP how to support host defense and recover tissue function and integrity. We propose that MP are not intrinsically active drivers of organ injury and dysfunction but dynamic amplifiers (and biomarkers) of specific tissue microenvironments that vary across spatial and temporal contexts. Therefore, MP receptors are frequently redundant and suboptimal targets for specific therapeutic interventions compared to molecular targets upstream in adaptive humoral or cellular stress response pathways that influence tissue milieus at a contextual level.

Contribution of αβ T cells to macrophage polarization and MSC recruitment and proliferation on titanium implants

Physiochemical cues like topography and wettability can impact the inflammatory response and tissue integration after biomaterial implantation. T cells are essential for immunomodulation of innate immune cells and play an important role in the host response to biomaterial implantation. This study aimed to understand how CD4+ and CD8+ T cell subsets, members of the αβ T cell family, polarize in response to smooth, rough, or rough-hydrophilic titanium (Ti) implants and whether their presence modulates immune cell crosstalk and mesenchymal stem cell (MSC) recruitment following biomaterial implantation. Post-implantation in mice, we found that CD4+ and CD8+ T cell subsets polarized differentially in response to modified Ti surfaces. Additionally, mice lacking αβ T cells had significantly more pro-inflammatory macrophages, fewer anti-inflammatory macrophages, and reduced MSC recruitment in response to modified Ti post-implantation than αβ T cell -competent mice. Our results demonstrate that T cell activation plays a significant role during the inflammatory response to implanted biomaterials, contributing to macrophage polarization and MSC recruitment and proliferation, and the absence of αβ T cells compromises new bone formation at the implantation site. STATEMENT OF SIGNIFICANCE: T cells are essential for immunomodulation and play an important role in the host response to biomaterial implantation. Our results demonstrate that T cells actively participate during the inflammatory response to implanted biomaterials, controlling macrophage phenotype and recruitment of MSCs to the implantation site.

Tracing immune cells around biomaterials with spatial anchors during large-scale wound regeneration

Skin scarring devoid of dermal appendages after severe trauma has unfavorable effects on aesthetic and physiological functions. Here we present a method for large-area wound regeneration using biodegradable aligned extracellular matrix scaffolds. We show that the implantation of these scaffolds accelerates wound coverage and enhances hair follicle neogenesis. We perform multimodal analysis, in combination with single-cell RNA sequencing and spatial transcriptomics, to explore the immune responses around biomaterials, highlighting the potential role of regulatory T cells in mitigating tissue fibrous by suppressing excessive type 2 inflammation. We find that immunodeficient mice lacking mature T lymphocytes show the typical characteristic of tissue fibrous driven by type 2 macrophage inflammation, validating the potential therapeutic effect of the adaptive immune system activated by biomaterials. These findings contribute to our understanding of the coordination of immune systems in wound regeneration and facilitate the design of immunoregulatory biomaterials in the future.

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.

Novel HALO® image analysis to determine cell phenotype in porous precision-templated scaffolds

Image analysis platforms have gained increasing popularity in the last decade for the ability to automate and conduct high-throughput, multiplex, and quantitative analyses of a broad range of pathological tissues. However, imaging tissues with unique morphology or tissues containing implanted biomaterial scaffolds remain a challenge. Using HALO®, an image analysis platform specialized in quantitative tissue analysis, we have developed a novel method to determine multiple cell phenotypes in porous precision-templated scaffolds (PTS). PTS with uniform spherical pores between 30 and 40 μm in diameter have previously exhibited a specific immunomodulation of macrophages toward a pro-healing phenotype and an overall diminished foreign body response (FBR) compared to PTS with larger or smaller pore sizes. However, signaling pathways orchestrating this pro-healing in 40 μm PTS remain unclear. Here, we use HALO® to phenotype PTS resident cells and found a decrease in pro-inflammatory CD86 and an increase in pro-healing CD206 expression in 40 μm PTS compared to 100 μm PTS. To understand the mechanisms that drive these outcomes, we investigated the role of myeloid-differentiation-primary-response gene 88 (MyD88) in regulating the pro-healing phenomenon observed only in 40 μm PTS. When subcutaneously implanted in MyD88KO mice, 40 μm PTS reduced the expression of CD206, and the scaffold resident cells displayed an average larger nuclear size compared to 40 μm PTS implanted in mice expressing MyD88. Overall, this study demonstrates a novel image analysis method for phenotyping cells within PTS and identifies MyD88 as a critical mediator in the pore-size-dependent regenerative healing and host immune response to PTS.

Design of cell-type-specific hyperstable IL-4 mimetics via modular de novo scaffolds

The interleukin-4 (IL-4) cytokine plays a critical role in modulating immune homeostasis. Although there is great interest in harnessing this cytokine as a therapeutic in natural or engineered formats, the clinical potential of native IL-4 is limited by its instability and pleiotropic actions. Here, we design IL-4 cytokine mimetics (denoted Neo-4) based on a de novo engineered IL-2 mimetic scaffold and demonstrate that these cytokines can recapitulate physiological functions of IL-4 in cellular and animal models. In contrast with natural IL-4, Neo-4 is hyperstable and signals exclusively through the type I IL-4 receptor complex, providing previously inaccessible insights into differential IL-4 signaling through type I versus type II receptors. Because of their hyperstability, our computationally designed mimetics can directly incorporate into sophisticated biomaterials that require heat processing, such as three-dimensional-printed scaffolds. Neo-4 should be broadly useful for interrogating IL-4 biology, and the design workflow will inform targeted cytokine therapeutic development.

Gelatin nanofiber-reinforced decellularized amniotic membrane promotes axon regeneration and functional recovery in the surgical treatment of peripheral nerve injury

Effective recovery of peripheral nerve injury (PNI) after surgical treatment relies on promoting axon regeneration and minimizing the fibrotic response. Decellularized amniotic membrane (dAM) has unique features as a natural matrix for promoting PNI repair due to its pro-regenerative extracellular matrix (ECM) structure and anti-inflammatory properties. However, the fragile nature and rapid degradation rate of dAM limit its widespread use in PNI surgery. Here we report an engineered composite membrane for PNI repair by combining dAM with gelatin (Gel) nanofiber membrane to construct a Gel nanofiber-dAM composite membrane (Gel-dAM) through interfacial bonding. The Gel-dAM showed enhanced mechanical properties and reduced degradation rate, while retaining maximal bioactivity and biocompatibility of dAM. These factors led to improved axon regeneration, reduced fibrotic response, and better functional recovery in PNI repair. As a fully natural materials-derived off-the-shelf matrix, Gel-dAM exhibits superior clinical translational potential for the surgical treatment of PNI.

Arthritic Microenvironment-Dictated Fate Decisions for Stem Cells in Cartilage Repair

The microenvironment and stem cell fate guidance of post-traumatic articular cartilage regeneration is primarily the focus of cartilage tissue engineering. In articular cartilage, stem cells are characterized by overlapping lineages and uneven effectiveness. Within the first 12 weeks after trauma, the articular inflammatory microenvironment (AIME) plays a decisive role in determining the fate of stem cells and cartilage. The development of fibrocartilage and osteophyte hyperplasia is an adverse outcome of chronic inflammation, which results from an imbalance in the AIME during the cartilage tissue repair process. In this review, the sources for the different types of stem cells and their fate are summarized. The main pathophysiological events that occur within the AIME as well as their protagonists are also discussed. Additionally, regulatory strategies that may guide the fate of stem cells within the AIME are proposed. Finally, strategies that provide insight into AIME pathophysiology are discussed and the design of new materials that match the post-traumatic progress of AIME pathophysiology in a spatial and temporal manner is guided. Thus, by regulating an appropriately modified inflammatory microenvironment, efficient stem cell-mediated tissue repair may be achieved.

Pro-angiogenic photo-crosslinked silk fibroin hydrogel: a potential candidate for repairing alveolar bone defects

OBJECTIVE

This study aimed to develop a pro-angiogenic hydrogel with in situ gelation ability for alveolar bone defects repair.

METHODOLOGY

Silk fibroin was chemically modified by Glycidyl Methacrylate (GMA), which was evaluated by proton nuclear magnetic resonance (1H-NMR). Then, the photo-crosslinking ability of the modified silk fibroin was assessed. Scratch and transwell-based migration assays were conducted to investigate the effect of the photo-crosslinked silk fibroin hydrogel on the migration of human umbilical vein endothelial cells (HUVECs). In vitro angiogenesis was conducted to examine whether the photo-crosslinked silk fibroin hydrogel would affect the tube formation ability of HUVECs. Finally, subcutaneous implantation experiments were conducted to further examine the pro-angiogenic ability of the photo-crosslinked silk fibroin hydrogel, in which the CD31 and α-smooth muscle actin (α-SMA) were stained to assess neovascularization. The tumor necrosis factor-α (TNF-α) and interleukin-1β (IL-1β) were also stained to evaluate inflammatory responses after implantation.

RESULTS

GMA successfully modified the silk fibroin, which we verified by our 1H-NMR and in vitro photo-crosslinking experiment. Scratch and transwell-based migration assays proved that the photo-crosslinked silk fibroin hydrogel promoted HUVEC migration. The hydrogel also enhanced the tube formation of HUVECs in similar rates to Matrigel®. After subcutaneous implantation in rats for one week, the hydrogel enhanced neovascularization without triggering inflammatory responses.

CONCLUSION

This study found that photo-crosslinked silk fibroin hydrogel showed pro-angiogenic and inflammation inhibitory abilities. Its photo-crosslinking ability makes it suitable for matching irregular alveolar bone defects. Thus, the photo-crosslinkable silk fibroin-derived hydrogel is a potential candidate for constructing scaffolds for alveolar bone regeneration.

Conserved and tissue-specific immune responses to biologic scaffold implantation

Upon implantation into a patient, any biomaterial induces a cascade of immune responses that influences the outcome of that device. This cascade depends upon several factors, including the composition of the material itself and the location in which the material is implanted. There is still significant uncertainty around the role of different tissue microenvironments in the immune response to biomaterials and how that may alter downstream scaffold remodeling and integration. In this study, we present a study evaluating the immune response to decellularized extracellular matrix materials within the intraperitoneal cavity, the subcutaneous space, and in a traumatic skeletal muscle injury microenvironment. All different locations induced robust cellular recruitment, specifically of macrophages and eosinophils. The latter was most prominent in the subcutaneous space. Intraperitoneal implants uniquely recruited B cells that may alter downstream reactivity as adaptive immunity has been strongly implicated in the outcome of scaffold remodeling. These data suggest that the location of tissue implants should be taken together with the composition of the material itself when designing devices for downline therapeutics.

Hydrophilic nanofibers with aligned topography modulate macrophage-mediated host responses via the NLRP3 inflammasome

Successful biomaterial implantation requires appropriate immune responses. Macrophages are key mediators involved in this process. Currently, exploitation of the intrinsic properties of biomaterials to modulate macrophages and immune responses is appealing. In this study, we prepared hydrophilic nanofibers with an aligned topography by incorporating polyethylene glycol and polycaprolactone using axial electrospinning. We investigated the effect of the nanofibers on macrophage behavior and the underlying mechanisms. With the increase of hydrophilicity of aligned nanofibers, the inflammatory gene expression of macrophages adhering to them was downregulated, and M2 polarization was induced. We further presented clear evidence that the inflammasome NOD-like receptor thermal protein domain associated protein 3 (NLRP3) was the cellular sensor by which macrophages sense the biomaterials, and it acted as a regulator of the macrophage-mediated response to foreign bodies and implant integration. In vivo, we showed that the fibers shaped the implant-related immune microenvironment and ameliorated peritendinous adhesions. In conclusion, our study demonstrated that hydrophilic aligned nanofibers exhibited better biocompatibility and immunological properties.

A synthetic metastatic niche reveals antitumor neutrophils drive breast cancer metastatic dormancy in the lungs

Biomaterial scaffolds mimicking the environment in metastatic organs can deconstruct complex signals and facilitate the study of cancer progression and metastasis. Here we report that a subcutaneous scaffold implant in mouse models of metastatic breast cancer in female mice recruits lung-tropic circulating tumor cells yet suppresses their growth through potent in situ antitumor immunity. In contrast, the lung, the endogenous metastatic organ for these models, develops lethal metastases in aggressive breast cancer, with less aggressive tumor models developing dormant lungs suppressing tumor growth. Our study reveals multifaceted roles of neutrophils in regulating metastasis. Breast cancer-educated neutrophils infiltrate the scaffold implants and lungs, secreting the same signal to attract lung-tropic circulating tumor cells. Second, antitumor and pro-tumor neutrophils are selectively recruited to the dormant scaffolds and lungs, respectively, responding to distinct groups of chemoattractants to establish activated or suppressive immune environments that direct different fates of cancer cells.

Cells resident to precision templated 40-µm pore scaffolds generate small extracellular vesicles that affect CD4+ T cell phenotypes through regulatory TLR4 signaling

Precision porous templated scaffolds (PTS) are a hydrogel construct of uniformly sized interconnected spherical pores that induce a pro-healing response (reducing the foreign body reaction, FBR) exclusively when the pores are 30-40µm in diameter. Our previous work demonstrated the necessity of Tregs in the maintenance of PTS pore size specific differences in CD4+ T cell phenotype. Work here characterizes the role of Tregs in the responses to implanted 40µm and 100µm PTS using WT and FoxP3+ cell (Treg) depleted mice. Proteomic analyses indicate that integrin signaling, monocytes/macrophages, cytoskeletal remodeling, inflammatory cues, and vesicule endocytosis may participate in Treg activation and the CD4+ T cell equilibrium modulated by PTS resident cell-derived small extracellular vesicles (sEVs). The role of MyD88-dependent and MyD88-independent TLR4 activation in PTS cell-derived sEV-to-T cell signaling is quantified by treating WT, TLR4ko, and MyD88ko splenic T cells with PTS cell-derived sEVs. STAT3 and mTOR are identified as mechanisms for further study for pore-size dependent PTS cell-derived sEV-to-T cell signaling. STATEMENT OF SIGNIFICANCE: Unique cell populations colonizing only within 40µm pore size PTS generate sEVs that resolve inflammation by modifying CD4+ T cell phenotypes through TLR4 signaling.

Engineered biomaterials in stem cell-based regenerative medicine

Stem cell-based regenerative therapies, which harness the self-renewal and differentiation properties of stem cells, have been in the spotlight due to their widespread applications in treating degenerative, aging, and other, generally intractable diseases. Therapeutically effective hematopoietic stem cells, mesenchymal stem cells, embryonic stem cells, and induced pluripotent stem cells have been used in numerous basic and translational studies with exciting results. However, pre-/post-transplantation issues of poor cell survival and retention, uncontrolled differentiation, and insufficient numbers of cells engrafted into host tissues are the major challenges in stem cell-based regenerative therapies. Engineered biomaterials have adjustable biochemical and biophysical properties that significantly affect cell behaviors, such as cell engraftment, survival, migration, and differentiation outcomes, thereby enhancing the engraftment of implanted stem cells and guiding tissue regeneration. Therefore, the combination of stem cell biology with bioengineered materials is a promising strategy to improve the therapeutic outcomes of stem cell-based regenerative therapy. In this review, we summarize the advances in the modulation of behaviors of stem cells via engineered biomaterials. We then present different approaches to harnessing bioengineered materials to enhance the transplantation of stem cells. Finally, we will provide future directions in regenerative therapy using stem cells.

Combining Allograft Adipose and Fascia Matrix as an Off-the-Shelf Scaffold for Adipose Tissue Engineering Stimulates Angiogenic Responses and Activates a Proregenerative Macrophage Profile in a Rodent Model

OBJECTIVE

Bioscaffolds for treating soft tissue defects have limitations. As a bioscaffold, allograft adipose matrix (AAM) is a promising approach to treat soft tissue defects. Previously, we revealed that combining superficial adipose fascia matrix with AAM, components of the hypodermis layer of adipose tissue, improved volume retention, adipogenesis, and angiogenesis in rats 8 weeks after it was implanted compared with AAM alone. Here, we modified the fascia matrix and AAM preparation, examined the tissue over 18 weeks, and conducted a deeper molecular investigation. We hypothesized that the combined matrices created a better scaffold by triggering angiogenesis and proregenerative signals.

METHODS

Human AAM and fascia matrix were implanted (4 [1 mL] implants/animal) into the dorsum of male Fischer rats (6-8 weeks old; ~140 g) randomly as follows: AAM, fascia, 75/25 (AAM/fascia), 50/50, and 50/50 + hyaluronic acid (HA; to improve extrudability) (n = 4/group/time point). After 72 hours, as well as 1, 3, 6, 9, 12, and 18 weeks, graft retention was assessed by a gas pycnometer. Adipogenesis (HE), angiogenesis (CD31), and macrophage infiltration (CD80 and CD163) were evaluated histologically at all time points. The adipose area and M1/M2 macrophage ratio were determined using ImageJ. RNA sequencing (RNA-seq) and bioinformatics were conducted to evaluate pathway enrichments.

RESULTS

By 18 weeks, the adipose area was 2365% greater for 50/50 HA (281.6 ± 21.6) than AAM (11.4 ± 0.9) (P < 0.001). The M1/M2 macrophage ratio was significantly lower for 50/50 HA (0.8 ± 0.1) than AAM (0.9 ± 0.1) at 6 weeks (16%; P < 0.05). This inversely correlated with adipose area (r = -0.6; P > 0.05). The RNA-seq data revealed that upregulated adipogenesis, angiogenesis, and macrophage-induced tissue regeneration genes were temporally different between the groups.

CONCLUSIONS

Combining the fascia matrix with AAM creates a bioscaffold with an improved retention volume that supports M2 macrophage-mediated angiogenesis and adipogenesis. This bioscaffold is worthy of further investigation.

Identification of Immune Infiltration in Odontogenic Keratocyst by Integrated Bioinformatics Analysis

BACKGROUND

Odontogenic keratocyst (OKC) is a relatively common odontogenic lesion characterized by local invasion in the maxillary and mandibular bones. In the pathological tissue slices of OKC, immune cell infiltrations are frequently observed. However, the immune cell profile and the molecular mechanism for immune cell infiltration of OKC are still unclear. We aimed to explore the immune cell profile of OKC and to explore the potential pathogenesis for immune cell infiltration in OKC.

METHODS

The microarray dataset GSE38494 including OKC and oral mucosa (OM) samples were obtained from the Gene Expression Omnibus (GEO) database. The differentially expressed genes (DEGs) in OKC were analyzed by R software. The hub genes of OKC were performed by protein-protein interaction (PPI) network. The differential immune cell infiltration and the potential relationship between immune cell infiltration and the hub genes were performed by single-sample gene set enrichment analysis (ssGSEA). The expression of COL1A1 and COL1A3 were confirmed by immunofluorescence and immunohistochemistry in 17 OKC and 8 OM samples.

RESULTS

We detected a total of 402 differentially expressed genes (DEGs), of which 247 were upregulated and 155 were downregulated. DEGs were mainly involved in collagen-containing extracellular matrix pathways, external encapsulating structure organization, and extracellular structure organization. We identified ten hub genes, namely FN1, COL1A1, COL3A1, COL1A2, BGN, POSTN, SPARC, FBN1, COL5A1, and COL5A2. A significant difference was observed in the abundances of eight types of infiltrating immune cells between the OM and OKC groups. Both COL1A1 and COL3A1 exhibited a significant positive correlation with natural killer T cells and memory B cells. Simultaneously, they demonstrated a significant negative correlation with CD56dim natural killer cells, neutrophils, immature dendritic cells, and activated dendritic cells. Immunohistochemistry analysis showed that COL1A1 (P = 0.0131) and COL1A3 (P < 0.001) were significantly elevated in OKC compared with OM.

CONCLUSIONS

Our findings provide insights into the pathogenesis of OKC and illuminate the immune microenvironment within these lesions. The key genes, including COL1A1 and COL1A3, may significantly impact the biological processes associated with OKC.

Integrated Multi-omics Analysis of Early Lung Adenocarcinoma Links Tumor Biological Features with Predicted Indolence or Aggressiveness

Lung adenocarcinoma (LUAD) is a heterogeneous group of tumors associated with different survival rates, even when detected at an early stage. Here, we aim to investigate the biological determinants of early LUAD indolence or aggressiveness using radiomics as a surrogate of behavior. We present a set of 92 patients with LUAD with data collected across different methodologies. Patients were risk-stratified using the CT-based Score Indicative of Lung cancer Aggression (SILA) tool (0 = least aggressive, 1 = most aggressive). We grouped the patients as indolent (x ≤ 0.4, n = 14), intermediate (0.4 > x ≤ 0.6, n = 27), and aggressive (0.6 > x ≤ 1, n = 52). Using Cytometry by time of flight (CyTOF), we identified subpopulations with high HLA-DR expression that were associated with indolent behavior. In the RNA sequencing (RNA-seq) dataset, pathways related to immune response were associated with indolent behavior, while pathways associated with cell cycle and proliferation were associated with aggressive behavior. We extracted quantitative radiomics features from the CT scans of the patients. Integrating these datasets, we identified four feature signatures and four patient clusters that were associated with survival. Using single-cell RNA-seq, we found that indolent tumors had significantly more T cells and less B cells than aggressive tumors, and that the latter had a higher abundance of regulatory T cells and Th cells. In conclusion, we were able to uncover a correspondence between radiomics and tumor biology, which could improve the discrimination between indolent and aggressive LUAD tumors, enhance our knowledge in the biology of these tumors, and offer novel and personalized avenues for intervention.

Significance

This study provides a comprehensive profiling of LUAD indolence and aggressiveness at the biological bulk and single-cell levels, as well as at the clinical and radiomics levels. This hypothesis generating study uncovers several potential future research avenues. It also highlights the importance and power of data integration to improve our systemic understanding of LUAD and to help reduce the gap between basic science research and clinical practice.

Targeting the biology of aging with mTOR inhibitors

Inhibition of the protein kinase mechanistic target of rapamycin (mTOR) with the Food and Drug Administration (FDA)-approved therapeutic rapamycin promotes health and longevity in diverse model organisms. More recently, specific inhibition of mTORC1 to treat aging-related conditions has become the goal of basic and translational scientists, clinicians and biotechnology companies. Here, we review the effects of rapamycin on the longevity and survival of both wild-type mice and mouse models of human diseases. We discuss recent clinical trials that have explored whether existing mTOR inhibitors can safely prevent, delay or treat multiple diseases of aging. Finally, we discuss how new molecules may provide routes to the safer and more selective inhibition of mTOR complex 1 (mTORC1) in the decade ahead. We conclude by discussing what work remains to be done and the questions that will need to be addressed to make mTOR inhibitors part of the standard of care for diseases of aging.

Antimicrobial Biomaterials for Chronic Wound Care

Chronic wounds encompass a myriad of lesions, including venous and arterial leg ulcers, diabetic foot ulcers (DFUs), pressure ulcers, non-healing surgical wounds and others. Despite the etiological differences, chronic wounds share several features at a molecular level. The wound bed is a convenient environment for microbial adherence, colonization and infection, with the initiation of a complex host-microbiome interplay. Chronic wound infections with mono- or poly-microbial biofilms are frequent and their management is challenging due to tolerance and resistance to antimicrobial therapy (systemic antibiotic or antifungal therapy or antiseptic topicals) and to the host's immune defense mechanisms. The ideal dressing should maintain moisture, allow water and gas permeability, absorb wound exudates, protect against bacteria and other infectious agents, be biocompatible, be non-allergenic, be non-toxic and biodegradable, be easy to use and remove and, last but not least, it should be cost-efficient. Although many wound dressings possess intrinsic antimicrobial properties acting as a barrier to pathogen invasion, adding anti-infectious targeted agents to the wound dressing may increase their efficiency. Antimicrobial biomaterials may represent a potential substitute for systemic treatment of chronic wound infections. In this review, we aim to describe the available types of antimicrobial biomaterials for chronic wound care and discuss the host response and the spectrum of pathophysiologic changes resulting from the contact between biomaterials and host tissues.

Biologic Mechanisms of Macrophage Phenotypes Responding to Infection and the Novel Therapies to Moderate Inflammation

Pro-inflammatory and anti-inflammatory types are the main phenotypes of the macrophage, which are commonly notified as M1 and M2, respectively. The alteration of macrophage phenotypes and the progression of inflammation are intimately associated; both phenotypes usually coexist throughout the whole inflammation stage, involving the transduction of intracellular signals and the secretion of extracellular cytokines. This paper aims to address the interaction of macrophages and surrounding cells and tissues with inflammation-related diseases and clarify the crosstalk of signal pathways relevant to the phenotypic metamorphosis of macrophages. On these bases, some novel therapeutic methods are proposed for regulating inflammation through monitoring the transition of macrophage phenotypes so as to prevent the negative effects of antibiotic drugs utilized in the long term in the clinic. This information will be quite beneficial for the diagnosis and treatment of inflammation-related diseases like pneumonia and other disorders involving macrophages.

Engineered collagen polymeric materials create noninflammatory regenerative microenvironments that avoid classical foreign body responses

The efficacy and longevity of medical implants and devices is largely determined by the host immune response, which extends along a continuum from pro-inflammatory/pro-fibrotic to anti-inflammatory/pro-regenerative. Using a rat subcutaneous implantation model, along with histological and transcriptomics analyses, we characterized the tissue response to a collagen polymeric scaffold fabricated from polymerizable type I oligomeric collagen (Oligomer) in comparison to commercial synthetic and collagen-based products. In contrast to commercial biomaterials, no evidence of an immune-mediated foreign body reaction, fibrosis, or bioresorption was observed with Oligomer scaffolds for beyond 60 days. Oligomer scaffolds were noninflammatory, eliciting minimal innate inflammation and immune cell accumulation similar to sham surgical controls. Genes associated with Th2 and regulatory T cells were instead upregulated, implying a novel pathway to immune tolerance and regenerative remodeling for biomaterials.