Immunomodulatory Biomaterials Research Articles

Abstract IA010: Bioengineering cell-based therapeutics

Abstract Cell-based therapeutics are an emerging modality that can potentially treat many currently intractable diseases through uniquely powerful modes of action. Our group is innovating new biomaterials and cellular constructs for medicine and biology by combining chemical biology, cellular engineering, and multi-scale fabrication. We have pioneered innovative approaches to synthesizing and in vivo screening of large libraries of biomaterial formulations for tailored applications in immunology and medicine. In my talk, I will describe our advances in discovering immunomodulatory biomaterials that can interact appropriately with the host immune system for localized immunomodulation. I will highlight our efforts to develop “cytokine factories” locally activating the innate and adaptive immune response to generate systemic immunotherapy and eradicate metastatic cancer. This approach has advanced to phase I/II human clinical trials for treating recurrent, refractory ovarian cancer. Citation Format: Omid Veiseh. Bioengineering cell-based therapeutics [abstract]. In: Proceedings of the AACR Special Conference in Cancer Research: Optimizing Therapeutic Efficacy and Tolerability through Cancer Chemistry; 2024 Dec 9-11; Toronto, Ontario, Canada. Philadelphia (PA): AACR; Mol Cancer Ther 2024;23(12_Suppl):Abstract nr IA010.

Development of Biomaterials to Modulate the Function of Macrophages in Wound Healing.

Wound healing is a complex and precisely regulated process that encompasses multiple stages, including inflammation, anti-inflammation, and tissue repair. It involves various cells and signaling molecules, with macrophages demonstrating a significant degree of plasticity and playing a crucial regulatory role at different stages. In recent years, the use of biomaterials, which include both natural and synthetic polymers or macromolecules, has proliferated for the purpose of enhancing wound healing. This review summarizes how these diverse biomaterials promote wound healing by modulating macrophage behavior and examines the broader implications of these modulations. Additionally, we discuss the limitations associated with the clinical application of immunomodulatory biomaterials and propose potential solutions. Finally, we look towards future developments in the design of immunomodulatory biomaterials intended to enhance wound healing.

Immunomodulatory Biomaterials: Tailoring Surface Properties to Mitigate Foreign Body Reaction and Enhance Tissue Regeneration.

The immune cells have demonstrated the ability to promote tissue repair by removing debris, breaking down the extracellular matrix, and regulating cytokine secretion profile. If the behavior of immune cells is not well directed, chronic inflammation and foreign body reaction (FBR) will lead to scar formation and loss of biomaterial functionality. The immunologic response toward tissue repair or chronic inflammation after injury and implantation can be modulated by manipulating the surface properties of biomaterials. Tailoring surface properties of biomaterials enables the regulation of immune cell fate such as adhesion, proliferation, recruitment, polarization, and cytokine secretion profile. This review begins with an overview of the role of immune cells in tissue healing and their interactions with biomaterials. It then discusses how the surface properties of biomaterials influence immune cell behavior. The core focus is reviewing surface modification methods to create innovative materials that reduce foreign body reactions and enhance tissue repair and regeneration by modulating immune cell activities. The review concludes with insights into future advancements in surface modification techniques and the associated challenges.

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.

Phosphatidylserine-functional polydimethylsiloxane substrates regulate macrophage M2 polarization via modulus-dependent NF-κB/PPARγ pathway

Macrophages, highly plastic innate immune cells, critically influence the success of implantable devices by responding to biochemical and physical cues. However, the mechanisms underlying their synergistic regulation of macrophage polarization on implant surfaces remain poorly understood. Therefore, we constructed anti-inflammatory phosphatidylserine (PS) modified polydimethylsiloxane (PDMS) substrates with low, medium, and high modulus (1–100 kPa) to investigate the combined effects and underlying mechanisms of substrate modulus and biochemical signal on macrophage polarization. The introduction of PS on the PDMS surface not only significantly enhanced the polarization of M0 to M2 but also potently suppressed lipopolysaccharide (LPS)-induced M1 activation, with this effect further potentiated by a reduction in substrate modulus. In vivo subcutaneous implantation experiments also corroborated the synergistic effect of PS functionalization and low modulus PDMS in inhibiting M1 activation and promoting M2 polarization. Notably, reduced modulus led to decreased integrin αV/β3 clustering and cytoskeletal protein aggregation, ultimately diminishing YAP activation and nuclear translocation. Concomitantly, this disruption of the Piezo1-cytoskeletal protein positive feedback loop resulted in reduced p65/IκB phosphorylation and inflammation, while concurrently promoting PPARγ expression. Overall, our findings underscore the pivotal role of substrate modulus in modulating PS-mediated biomaterial-cell interactions, synergistically potentiating PS-induced M2 macrophage polarization, thus paving the way for the design of advanced immunomodulatory biomaterials.

Design Principles for Immunomodulatory Biomaterials.

The immune system is imperative to the survival of all biological organisms. A functional immune system protects the organism by detecting and eliminating foreign and host aberrant molecules. Conversely, a dysfunctional immune system characterized by an overactive or weakened immune system causes life-threatening autoimmune or immunodeficiency diseases. Therefore, a critical need exists to develop technologies that regulate the immune system to ensure homeostasis or treat several diseases. Accumulating evidence shows that biomaterials─artificial materials (polymers, metals, ceramics, or engineered cells and tissues) that interact with biological systems─can trigger immune responses, offering a materials science-based strategy to modulate the immune system. This Review discusses the expanding frontiers of biomaterial-based immunomodulation, focusing on principles for designing these materials. This Review also presents examples of immunomodulatory biomaterials, which include polymers and metal- and carbon-based nanomaterials, capable of regulating the innate and adaptive immune systems.

Immunoprotection Strategies in β-Cell Replacement Therapy: A Closer Look at Porcine Islet Xenotransplantation.

Type 1 diabetes mellitus (T1DM) is characterized by absolute insulin deficiency primarily due to autoimmune destruction of pancreatic β-cells. The prevailing treatment for T1DM involves daily subcutaneous insulin injections, but a substantial proportion of patients face challenges such as severe hypoglycemic episodes and poorly controlled hyperglycemia. For T1DM patients, a more effective therapeutic option involves the replacement of β-cells through allogeneic transplantation of either the entire pancreas or isolated pancreatic islets. Unfortunately, the scarcity of transplantable human organs has led to a growing list of patients waiting for an islet transplant. One potential alternative is xenotransplantation of porcine pancreatic islets. However, due to inter-species molecular incompatibilities, porcine tissues trigger a robust immune response in humans, leading to xenograft rejection. Several promising strategies aim to overcome this challenge and enhance the long-term survival and functionality of xenogeneic islet grafts. These strategies include the use of islets derived from genetically modified pigs, immunoisolation of islets by encapsulation in biocompatible materials, and the creation of an immunomodulatory microenvironment by co-transplanting islets with accessory cells or utilizing immunomodulatory biomaterials. This review concentrates on delineating the primary obstacles in islet xenotransplantation and elucidates the fundamental principles and recent breakthroughs aimed at addressing these challenges.

Piezoelectric stimulation enhances bone regeneration in alveolar bone defects through metabolic reprogramming of macrophages.

Immunomodulation has emerged as a promising strategy for promoting bone regeneration. However, designing osteoimmunomodulatory biomaterial that can respond to mechanical stress in the unique microenvironment of alveolar bone under continuous occlusal stress remains a significant challenge. Herein, a wireless piezoelectric stimulation system, namely, piezoelectric hydrogel incorporating BaTiO3 nanoparticles (BTO NPs), is successfully developed to generate piezoelectric potentials for modulating macrophage reprogramming. The piezoelectric stimulation reprograms macrophages towards the M2 phenotype, which subsequently induces osteogenicdifferentiation of bone marrow mesenchymal stem cells (BMSCs). RNA sequencing analysis reveals that piezoelectricity-modulated macrophage M2 polarization is closely associated with metabolic reprogramming, including increased amino acid biosynthesis and fatty acid oxidation. The composite hydrogel with excellent biocompatibility exhibits immunomodulatory and osteoinductive activities. In a rat model of alveolar bone defects, the piezoelectric hydrogel effectively promotes endogenous bone regeneration at the load-bearing sites. The piezoelectric-driven osteoimmunomodulation proposed in this study not only broadens understanding of the mechanism underlying piezoelectric biomaterials for tissue regeneration but also provides new insights into the design and development of next-generation immunomodulatory biomaterials.

Immunoengineering Biomaterials for Musculoskeletal Tissue Repair across Lifespan.

Musculoskeletal diseases and injuries are among the leading causes of pain and morbidity worldwide. Broad efforts have focused on developing pro-regenerative biomaterials to treat musculoskeletal conditions; however, these approaches have yet to make a significant clinical impact. Recent studies have demonstrated that the immune system is central in orchestrating tissue repair and that targeting pro-regenerative immune responses can improve biomaterial therapeutic outcomes. However, aging is a critical factor negatively affecting musculoskeletal tissue repair and immune function. Hence, understanding how age affects the response to biomaterials is essential for improving musculoskeletal biomaterial therapies. This review focuses on the intersection of the immune system and aging in response to biomaterials for musculoskeletal tissue repair. The article introduces the general impacts of aging on tissue physiology, the immune system, and the response to biomaterials. Then, it explains how the adaptive immune system guides the response to injury and biomaterial implants in cartilage, muscle, and bone and discusses how aging impacts these processes in each tissue type. The review concludes by highlighting future directions for the development and translation of personalized immunomodulatory biomaterials for musculoskeletal tissue repair.

Matrix stiffness regulates macrophage polarisation via the Piezo1-YAP signalling axis.

Macrophages play a pivotal role in the immunological cascade activated in response to biomedical implants, which predetermine acceptance or rejection of implants by the host via pro- and anti-inflammatory polarisation states. The role of chemical signals in macrophage polarisation is well-established, but how physical cues regulate macrophage function that may play a fundamental role in implant-bone interface, remains poorly understood. Here we find that bone marrow-derived macrophages (BMDM) cultured on polyacrylamide gels of varying stiffness exhibit different polarisation states. BMDM are 'primed' to a pro-inflammatory M1 phenotype on stiff substrates, while to an anti-inflammatory M2 phenotype on soft and medium stiffness substrates. It is further observed that matrix stiffening increases Piezo1 expression, as well as leads to subsequent activation of the mechanotransduction signalling effector YAP, thus favouring M1 polarisation whilst suppressing M2 polarisation. Moreover, upon treatment with YAP inhibitor, we successfully induce macrophage re-polarisation to the M2 state within the implant site microenvironment, which in turn promotes implant osseointegration. Collectively, our present study thus characterises the critical role of the Piezo1-YAP signalling axis in macrophage mechanosensing and stiffness-mediated macrophage polarisation and provides cues for the design of immuno-modulatory biomaterials that can regulate the macrophage phenotype.

Multifunctional biomimetic hydrogel dressing provides anti-infection treatment and improves immunotherapy by reprogramming the infection-related wound microenvironment

The advancement of biomaterials with antimicrobial and wound healing properties continues to present challenges. Macrophages are recognized for their significant role in the repair of infection-related wounds. However, the interaction between biomaterials and macrophages remains complex and requires further investigation. In this research, we propose a new sequential immunomodulation method to enhance and expedite wound healing by leveraging the immune properties of bacteria-related wounds, utilizing a novel mixed hydrogel dressing. The hydrogel matrix is derived from porcine acellular dermal matrix (PADM) and is loaded with a new type of bioactive glass nanoparticles (MBG) doped with magnesium (Mg-MBG) and loaded with Curcumin (Cur). This hybrid hydrogel demonstrates controlled release of Cur, effectively eradicating bacterial infection in the early stage of wound infection, and the subsequent release of Mg ions (Mg2+) synergistically inhibits the activation of inflammation-related pathways (such as MAPK pathway, NF-κB pathway, TNF-α pathway, etc.), suppressing the inflammatory response caused by infection. Therefore, this innovative hydrogel can safely and effectively expedite wound healing during infection. Our design strategy explores novel immunomodulatory biomaterials, offering a fresh approach to tackle current clinical challenges associated with wound infection treatment.

Engineering immunomodulatory biomaterials to combat bacterial infections

Modulating the immune system using engineered materials is an emerging strategy to combat bacterial infections. Bacteria adopt immune evasion strategies to ensure their survival, ultimately leading to persistence and recurrence of infections. With a rise in antimicrobial resistance and a decrease in antibiotic efficacy, host-directed therapies using immunomodulatory biomaterials are a promising approach to infection management. Here, we review biomaterials developed to modulate the immune system, with an emphasis on innate immunity. We specifically highlight the recent implementation of functionalized surfaces for immunomodulation, including metal ion releasing coatings, stimuli-responsive polymeric coatings, and interleukin releasing surfaces. We also describe immunomodulatory nanoparticles, including lipid-based nanoparticles, biomimetic nanoparticles, and inorganic nanocarriers. Lastly, we explore immunomodulatory hydrogels used primarily for the treatment of wound infections. These approaches offer new strategies for treating bacterial infections and enhancing existing antimicrobial approaches, all while avoiding complications associated with antimicrobial resistance.

Bioengineering Cell Therapy for Treatment of Peripheral Artery Disease.

Peripheral artery disease is an atherosclerotic disease associated with limb ischemia that necessitates limb amputation in severe cases. Cell therapies comprised of adult mononuclear or stromal cells have been clinically tested and show moderate benefits. Bioengineering strategies can be applied to modify cell behavior and function in a controllable fashion. Using mechanically tunable or spatially controllable biomaterials, we highlight examples in which biomaterials can increase the survival and function of the transplanted cells to improve their revascularization efficacy in preclinical models. Biomaterials can be used in conjunction with soluble factors or genetic approaches to further modulate the behavior of transplanted cells and the locally implanted tissue environment in vivo. We critically assess the advances in bioengineering strategies such as 3-dimensional bioprinting and immunomodulatory biomaterials that can be applied to the treatment of peripheral artery disease and then discuss the current challenges and future directions in the implementation of bioengineering strategies.

TOWARDS UNDERSTANDING HOW NEUTROPHIL INSTRUCT THE IMMUNE RESPONSE TO BIOMATERIALS

Biomaterials with mechanical or biological competence are ubiquitous in musculoskeletal disorders, and understanding the inflammatory response they trigger is key to guide tissue regeneration. While macrophage role has been widely investigated, immune response is regulated by other immune cells, including neutrophils, the most abundant leukocyte in human blood. As first responders to injury, infection or material implantation, neutrophils recruit other immune cells, and therefore influence the onset and resolution of chronic inflammation, and macrophage polarization. This response depends on the physical and chemical properties of the biomaterials, among other factors. In this study we report an in vitro culture model to describe the most important neutrophil functions in relation to tissue repair.We identified neutrophil survival and death, neutrophils extracellular trap formation, release of reactive oxygen species and degranulation with cytokines release as key functions and introduced a corresponding array of assays. These tests were suitable to identify clear differences in the response by neutrophils that were cultured on material of different origin, stiffness and chemical composition. Overall, substrates from biopolymers of natural origin resulted in increased survival, less neutrophil extracellular trap formation, and more reactive oxygen species production than synthetic polymers. Within the range of mechanical properties explored (storage modulus below 5 k Pa), storage modulus of covalently crosslinked hyaluronic acid hydrogels did not significantly alter neutrophils response, whereas polyvinyl alcohol gels of matching mechanical properties displayed a response indicating increased activation.Additionally, we present the effect of material stiffness, charge, coating and culture conditions in the measured neutrophils response. Further studies are needed to correlate the neutrophil response to tissue healing.By deciphering how neutrophils initiate and modulate the immune response to material implantation, we aim at introducing new principles to design immunomodulatory biomaterials for musculoskeletal disorders.AcknowledgmentsThis work was supported by the AO Foundation, AO CMF, grant AOCMF-21-04S.

Investigating Immunomodulatory Biomaterials for Preventing the Foreign Body Response.

Implantable biomaterials represent the forefront of regenerative medicine, providing platforms and vessels for delivering a creative range of therapeutic benefits in diverse disease contexts. However, the chronic damage resulting from implant rejection tends to outweigh the intended healing benefits, presenting a considerable challenge when implementing treatment-based biomaterials. In response to implant rejection, proinflammatory macrophages and activated fibroblasts contribute to a synergistically destructive process of uncontrolled inflammation and excessive fibrosis. Understanding the complex biomaterial-host cell interactions that occur within the tissue microenvironment is crucial for the development of therapeutic biomaterials that promote tissue integration and minimize the foreign body response. Recent modifications of specific material properties enhance the immunomodulatory capabilities of the biomaterial and actively aid in taming the immune response by tuning interactions with the surrounding microenvironment either directly or indirectly. By incorporating modifications that amplify anti-inflammatory and pro-regenerative mechanisms, biomaterials can be optimized to maximize their healing benefits in harmony with the host immune system.

Copper-Zinc-Doped Bilayer Bioactive Glasses Loaded Hydrogel with Spatiotemporal Immunomodulation Supports MRSA-Infected Wound Healing.

Developing biomaterials with antimicrobial and wound-healing activities for the treatment of wound infections remains challenging. Macrophages play non-negligible roles in healing infection-related wounds. In this study, a new sequential immunomodulatory approach is proposed to promote effective and rapid wound healing using a novel hybrid hydrogel dressing based on the immune characteristics of bacteria-associated wounds. The hydrogel dressing substrate is derived from a porcine dermal extracellular matrix (PADM) and loaded with a new class of bioactive glass nanoparticles (BGns) doped with copper (Cu) and zinc (Zn) ions (Cu-Zn BGns). This hybrid hydrogel demonstrates a controlled release of Cu2+ and Zn2+ and sequentially regulates the phenotypic transition of macrophages from M1 to M2 by alternately activating nucleotide-binding oligomerization domain (NOD) and inhibiting mitogen-activated protein kinases (MAPK) signaling pathways. Additionally, its dual-temporal bidirectional immunomodulatory function facilitates enhanced antibacterial activity and wound healing. Hence, this novel hydrogel is capable of safely and efficiently accelerating wound healing during infections. As such, the design strategy provides a new direction for exploring novel immunomodulatory biomaterials to address current clinical challenges related to the treatment of wound infections.

Cu-Sr Bilayer Bioactive Glass Nanoparticles/Polydopamine Functionalized Polyetheretherketone Enhances Osteogenic Activity and Prevents Implant-Associated Infections through Spatiotemporal Immunomodulation.

Key factors contributing to implantation failures include implant-associated infections (IAIs) and insufficient osseointegration of the implants. Polyetheretherketone (PEEK) is widely used in orthopedics, yet its clinical applications are restricted due to its poor osteogenic and antibacterial properties as well as inadequate immune responses. To overcome these drawbacks, a novel spatiotemporal immunomodulation approach is proposed, chelating Cu-Sr bilayer bioactive glass nanoparticles (CS-BGNs) onto the PEEK surface via polydopamine (PDA). The CS-BGNs possess a bilayer core-shell structure where copper is distributed in the outer layer and strontium is clustered in the inner layer. The results show that CS-BGNs/PDA functionalized PEEK demonstrates a controlled and sequential release of Cu2+ and Sr2+ . In the earlystage, Cu2+ from the outer layer releases rapidly, while Sr2+ from the inner layer releases in the late stage. This well-ordered release pattern modulates the phenotypic transition of macrophages, which induces M1 polarization in the early stage and M2 polarization in the late stage. Combined with the direct effects of Cu2+ and Sr2+ , the spatiotemporal immunomodulation not only benefits the early antibacterial and tissue-healing process, but also promotes the long-term process of osseointegration, providing new perspectives on the design of novel immunomodulatory biomaterials.

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.

Bioinspired Materials for Immunoengineering of T Cells and Natural Killer Cells

AbstractImmune responses are directed by the complex interactions of different cell types, including T cells and Natural Killer (NK) cells, with a key type of interaction being the formation of close cell‐cell adhesions: immune synapses. Drawing on biophysical characteristics of the immune synapse and the immune cell surface, researchers are developing bioinspired materials for immunoengineering. Here are reviewed key biophysical variables that impact immune cell signaling, and how these have been exploited to develop immunomodulatory biomaterials. Mechanical forces and material properties such as stiffness are sensed by immune cells. This has enabled the modulation of cell activation using mechanically‐controlled biomaterials: hydrogels, micropillars, and nanowire arrays. In parallel, microscopy has revealed micro‐scale and nanoscale molecular patterning at cell surfaces, inspiring the creation of micro‐ and nanopatterned materials using lithography and nanoparticle approaches. The complex 3D structures of immune cells have inspired the creation of topographically patterned substrates and controlled 3D microenvironments. Finally, technologies have been developed to externally modulate biophysical variables, using magnetic and optical fields to stimulate biomaterials and drive immune cell activation. Together, these bioinspired materials are enhancing the understanding of immunology. A challenge is translation to the clinic, e.g., via improved ex vivo cell engineering for adoptive immunotherapies.

Early osteoimmunomodulation by mucin hydrogels augments the healing and revascularization of rat critical-size calvarial bone defects.

The design principle of osteogenic bone grafts has shifted from immunological inertness to limiting foreign body response to combined osteoimmunomodulatory activity to promote high-quality endogenous bone regeneration. Recently developed immunomodulatory mucin hydrogels have been shown to elicit very low complement activation and suppress macrophage release and activation after implantation in vivo. However, their immunoregulatory activity has not yet been studied in the context of tissue repair. Herein, we synthesized mucin-monetite composite materials and investigated their early osteoimmunomodulation using a critical-size rat bone defect model. We demonstrated that the composites can polarize macrophages towards the M2 phenotype at weeks 1 and 2. The early osteoimmunomodulation enhanced early osteogenesis and angiogenesis and ultimately promoted fracture healing and engraftment (revascularization of the host vasculature) at weeks 6 and 12. Overall, we demonstrated the applicability of mucin-based immunomodulatory biomaterials to enhance tissue repair in tissue engineering and regenerative medicine.