Macrophage response to hydrophilic biomaterials regulates MSC recruitment and T-helper cell populations

Passivated hydrogel interface: Armor against foreign body response and inflammation in small-diameter vascular grafts

The development of small-diameter vascular grafts (SDVGs) still faces significant challenges, particularly in overcoming blockages within vessels. A key issue is the foreign-body response (FBR) triggered by the implants, which impairs the integration between grafts and native vessels. In this study, we applied an interfacial infiltration strategy to create a stable, hydrophilic, and passivated hydrogel coating on SDVGs. This coating effectively resisted FBR and improved integration between the grafts and host tissue. We also incorporated anthocyanins, an antioxidant, into the hydrogel network to mitigate oxidative stress and promote endothelialization. The hydrogel coating exhibited excellent stability, retaining its integrity during continuous flushing over 15 days. Anthocyanins were released in response to reactive oxygen species (ROS), reducing inflammation and enhancing vascularization in a mouse subcutaneous implantation model. In a rabbit carotid artery replacement model, the SDVGs exhibited rapid endothelialization, guided vascular remodeling, and inhibited calcification, showing strong potential for clinical application. This study presents a straightforward and effective approach to improve the patency rate, endothelialization, and anti-calcification properties of SDVGs by equipping them with a protective anti-FBR and anti-inflammation hydrogel layer.

Crosstalk between T cells and fibroblasts in biomaterial-mediated fibrosis

Biomaterial implants are a critical aspect of our medical therapies and biomedical research and come in various forms: stents, implantable glucose sensors, orthopedic implants, silicone implants, drug delivery systems, and tissue engineered scaffolds. Their implantation triggers a series of biological responses that often times lead to the foreign body response and subsequent fibrotic encapsulation, a dense ECM-rich capsule that isolates the biomaterial and renders it ineffective. These responses lead to the failure of biomaterials and is a major hurdle to overcome and in promoting their success. Much attention has been given to macrophage populations for the inflammatory component of these responses to biomaterials but recent work has identified an important role of T cells and their ability to modulate fibroblast activity and vice versa. In this review, we focus on T cell-fibroblast crosstalk by exploring T cell subsets, critical signaling pathways, and fibroblast populations that have been shown to dictate biomaterial-mediated fibrosis. We then highlight emerging technologies and model systems that enable new insights and avenues to T cell-fibroblast crosstalk that will improve biomaterial outcomes.

Macrophage Depletion Reduces Bone Loss and Alters Inflammatory Responses: A Mouse Peri-Implantitis Model

AIM

To evaluate the impact of macrophage depletion on bone loss and inflammatory responses in a mouse model of peri-implantitis, assessing macrophage depletion potential as a therapeutic strategy.

MATERIALS AND METHODS

Using 6-week-old male C57BL/6 mice, peri-implantitis was induced by placing a silk ligature around osteointegrated dental implants. Mice were divided into three groups: Healthy control (Healthy group); peri-implantitis with liposomal phosphate-buffered saline (PBS group); and peri-implantitis with liposomal clodronate for macrophage depletion (CLOD group). Two weeks after ligature placement, micro-CT, histological and real-time PCR analyses were performed to assess bone density, leukocyte infiltration and cytokine levels.

RESULTS

The CLOD group showed a significantly higher bone-to-implant contact (74%) and bone volume relative to total volume (79%) compared to the PBS group (53% and 54%, respectively) and Healthy group (64% and 66%, respectively). Histological analysis revealed significantly reduced leukocyte and macrophage counts in the CLOD group. Additionally, TNF-α and IL-10 levels were significantly decreased in the CLOD group compared with the PBS group.

CONCLUSION

Macrophage depletion effectively reduces bone loss and inflammation in peri-implantitis. This study highlights targeting macrophages as a promising approach for managing peri-implantitis, although further research is needed to optimize therapeutic strategies.

Enhancing the Implant Osteointegration via Supramolecular Co-Assembly Coating with Early Immunomodulation and Cell Colonization

Osteointegration, the effective coupling between an implant and bone tissue, is a highly intricate biological process. The initial stages of bone-related immunomodulation and cellular colonization play crucial roles, but have received limited attention. Herein, a novel supramolecular co-assembled coating of strontium (Sr)-doped metal polyphenol networks (MPN) modified with c(RGDfc) is developed and well-characterized, for eliciting an early immunomodulation and cellular colonization. The results showed that the (Sr-MPN)@RGD coating significantly regulated the polarization of macrophages to the M2 phenotype by controllable release of Sr, and promote the initial adhesion of bone marrow mesenchymal stem cells (BMSCs) by RGD presented on MPN. Notably, the (Sr-MPN)@RGD attenuated osteoclast differentiation and oxidative stress as well as enhanced osteoblast differentiation and angiogenesis due to macrophage polarization toward M2 phenotype, which in turn has a profound effect on neighboring cells through paracrine signaling. In vivo results showed that the (Sr-MPN)@RGD coating manifested superior osseointegration and bone maturation to the bare Ti-rod or Ti-rod coated with MPN and Sr-MPN. This work contributed to the design of multifunctional implant coatings that address the complex biological process of osteointegration from the perspective of orchestrating stem cell recruitment with immunomodulatory strategies.

Obesity prolongs the pro-inflammatory response and attenuates bone healing on titanium implants

Obesity is a metabolic disease resulting from excess body fat accumulation associated with chronic systemic inflammation. Obesity has been shown to impact the function and activity of neutrophils, macrophages, and T cells, contributing to higher circulating levels of pro-inflammatory cytokines. Biomaterial surface properties such as roughness and hydrophilicity can influence the behavior of immune cells in the peri-implant microenvironment. This study aimed to determine how obesity induced by a high-fat diet (HFD) affects the inflammatory response to modified titanium (Ti) implants and subsequent bone formation. Obese mice had significantly more neutrophils, pro-inflammatory macrophages, and T cells and fewer anti-inflammatory macrophages and mesenchymal stem cells (MSCs) in the peri-implant tissue than lean mice. Obesity also increased circulating adipokines and pro-inflammatory cytokines when compared to lean animals. Bone formation around Ti implants was reduced in obese mice compared to controls. Adoptive transfer of bone marrow cells isolated from obese mice into wild-type mice demonstrated the localized impact of obesity on immune cell function and phenotype, promoting a pro-inflammatory peri-implant microenvironment and attenuating bone formation post-implantation. These results show that obesity significantly affects the inflammatory response to modified Ti implants, prolonging the pro-inflammatory response to the implanted biomaterial and compromising bone formation. STATEMENT OF SIGNIFICANCE: Obesity has been shown to significantly alter physiological processes, including the behavior of immune cells, inducing a state of systemic chronic inflammation. Our study demonstrates that obesity-induced via a high-fat diet alters immune cell response to implanted biomaterials, with increased pro-inflammatory response and attenuated immunomodulation that results in decreased biomaterial integration.

Titanium nanotubes modulate immunophenotyping and cytokine secretion of T cells via IL-17A: a bioinformatic analysis and experimental validation

Object

We aim to explore the immunomodulatory properties of T cells on different titanium nanotubes and the key immunological factors involved in this process.

Methods

Transcriptome data from GEO database of healthy people and healthy implants were used to analyze cell infiltration and factor distribution of adaptive immune using bioinformatics tools. T cells from activated rat were cultured on titanium nanotubes that were prepared by anodization with different diameters (P-0, NT15-30 nm, NT40-100 nm, NT70-200 nm). The proliferation and expressions of the main transcription factors and cytokines of T-cells were detected. Magnetic bead sorting of CD3+ T cells and transcriptome sequencing were performed to explore the signaling pathways and key immune factors that may influence the related immune responses.

Results

Bioinformatics analysis showed that healthy peri-implant tissues were enriched by the most of T-cell subtypes. T-cell-mediated adaptive immunological responses involved IL-17A. On the third day, the NT15 and NT40 groups showed significantly higher pro-proliferative effects than the NT70 group (P<0.05). Notably, the NT40 group exhibited the lowest T-bet expression (P<0.05) along with the highest levels of Rorγt, Gata3, and Foxp3(P<0.05), followed by the NT15 group. Additionally, the NT40 group demonstrated reduced RANKL, TNF-α, and IL-6 (P<0.05) and increased OPG and IL-10 (P<0.05). Meanwhile, the NT15 group had lower IFN-γ expression(P>0.05) but higher IL-4, and TGF-β1 expressions(P<0.05). Differential expressed genes (DGEs) of T-cell related to the morphologies of titanium nanotubes were mostly enriched in the IL-17 signaling pathway mediated by IL-17A/F. Gene and protein expressions indicated that the NT40 group had the highest secretion in IL-17A of T cells.

Conclusion

Titanium nanotube morphologies in medium (100 nm) and small (30 nm) sizes significantly influence T cell differentiation and immune factor secretion, with T-cell-derived IL-17A likely playing a key regulatory role.

Advances in osteoimmunomodulation of biomaterials after intrabone implantation: focus on surface hydrophilicity

Biomaterials intended for intrabone implantation are extensively utilized in orthopedic and dental applications. Their surface properties, particularly hydrophilicity, significantly influence the biological interactions surrounding the implant, ultimately determining the implant's in vivo fate. Recently, the role of osteoimmunomodulation in these implantable biomaterials has been recognized for its importance in regulating biomaterial-mediated osteogenesis. Consequently, it is imperative to elucidate the correlation between hydrophilicity and the immune response for the development of osteoimmunomodulatory implants. Herein, this review highlights recent advances in osteoimmunomodulation of biomaterials after intrabone implantation from a novel perspective-surface hydrophilicity, and summarizes the series of immune reactions and subsequent bone remodeling that occur in response to hydrophilic implants, focusing on protein adsorption, the behaviors of major immune cells, and osteoimmunomodulation-enhanced angiogenesis and osteogenesis. Hydrophilic biomaterials have the capacity to alter the surrounding immune microenvironment and accelerate the process of material-tissue bonding, thereby facilitating the successful integration of biomaterials with tissue. Collectively, the authors hope that this article provides strategies for modulating hydrophilicity to achieve osteoimmunomodulatory performance and further promotes the development of novel implantable biomaterials for orthopedic and dental applications.

Adoptive transfer of immunomodulatory macrophages reduces the pro-inflammatory microenvironment and increases bone formation on titanium implants

Macrophages play a central role in orchestrating the inflammatory response to implanted biomaterials and are sensitive to changes in the chemical and physical characteristics of the implant. Macrophages respond to biological, chemical, and physical cues by polarizing into pro-inflammatory (M1) or anti-inflammatory (M2) states. We previously showed that rough-hydrophilic titanium (Ti) implants skew macrophage polarization towards an anti-inflammatory phenotype and increase mesenchymal stem cell (MSC) recruitment and bone formation around the implant. In the present study, we aimed to investigate whether the adoptive transfer of macrophages in different polarization states would alter the inflammatory microenvironment and improve biomaterial integration in macrophage-competent and macrophage-ablated mice. We found that ablating macrophages increased the presence of neutrophils, reduced T cells and MSCs, and compromised the healing and biomaterial integration process. These effects could not be rescued with adoptive transfer of naïve or polarized macrophages. Adoptive transfer of M1 macrophages into macrophage-competent mice increased inflammatory cells and inflammatory microenvironment, resulting in decreased bone-to-implant contact. Adoptive transfer of M2 macrophages into macrophage-competent mice reduced the pro-inflammatory environment in the peri‑implant tissue and increased bone-to-implant contact. Taken together, our results show the importance of macrophages in controlling and modulating the inflammatory process in response to implanted biomaterials and suggest they can be used to improve outcomes following biomaterial implantation. STATEMENT OF SIGNIFICANCE: Macrophages are central in orchestrating the inflammatory response to implanted biomaterials and are sensitive to biomaterial chemical and physical characteristics. Our study shows that a deficiency of macrophages results in prolonged inflammation and abolishes bone-biomaterial integration. Adoptive transfer of immunomodulatory macrophages into macrophage-competent mice reduced the inflammatory environment and increased bone-implant contact.

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.

Silk films with distinct surface topography modulate plasma membrane curvature to polarize macrophages

The physical properties of a biomaterial play a vital role in modulating macrophage polarization. However, discerning the specific effects of individual parameters can be intricate due to their interdependencies, limiting the mechanism underlying a specific parameter on the polarization of macrophages. Here, we engineered silk fibroin (SF) films with tunable surface roughness while maintaining similar physical properties by combining casting and salting out techniques. We demonstrate that increased surface roughness in SF films promotes M2-like macrophage polarization, characterized by enhanced secretion of anti-inflammatory cytokines. Transcriptomic analysis unveils the modulation of genes associated with extracellular matrix-cell interactions, highlighting the role of surface topography in regulating cellular processes. Mechanistically, we show that surface roughness induces macrophage membrane curvature, facilitating integrin αv endocytosis and thereby inhibiting the integrin-NF-kB signaling pathway. In vivo implantation assays corroborate that rough SF films substantially mitigate early inflammatory responses. This work establishes a direct link between surface roughness and intracellular signaling in macrophages, adding to our understanding of the biomaterial surface effect at the material-cell interface and bringing insights into material design.

Zinc-doped bioactive glass-functionalized polyetheretherketone to enhance the biological response in bone regeneration

Polyether ether ketone (PEEK) is gaining recognition as a highly promising polymer for orthopedic implants, attributed to its exceptional biocompatibility, ease of processing, and radiation resistance. However, its long-term in vivo application faces challenges, primarily due to suboptimal osseointegration from postimplantation inflammation and immune reactions. Consequently, biofunctionalization of PEEK implant surfaces emerges as a strategic approach to enhance osseointegration and increase the overall success rates of these implants. In our research, we engineered a multifaceted PEEK implant through the in situ integration of chitosan-coated zinc-doped bioactive glass nanoparticles (Zn-BGNs). This novel fabrication imbues the implant with immunomodulatory capabilities while bolstering its osseointegration potential. The biofunctionalized PEEK composite elicited several advantageous responses; it facilitated M2 macrophage polarization, curtailed the production of inflammatory mediators, and augmented the osteogenic differentiation of bone marrow mesenchymal stem cells. The experimental findings underscore the vital and intricate role of biofunctionalized PEEK implants in preserving normal bone immunity and metabolism. This study posits that utilizing chitosan-BGNs represents a direct and effective method for creating multifunctional implants. These implants are designed to facilitate biomineralization and immunomodulation, making them especially apt for orthopedic applications.

Osteointegration of Ti Bone Implants: A Study on How Surface Parameters Control the Foreign Body Response

The integration of titanium (Ti)-based implants with bone is limited, resulting in implant failure. This lack of osteointegration is due to the foreign body response (FBR) that occurs after the implantation of biodevices. The process begins with protein adsorption, which is governed by implant surface properties, e.g., chemistry, charge, wettability, and/or topography. The distribution and composition of the protein layer in turn influence the recruitment, differentiation, and modulation of immune and bone cells. The subsequent events that occur at the bone-material interface will ultimately determine whether the implant is encapsulated or will integrate with bone. Despite the numerous studies evaluating the influence of surface properties in the various stages of the FBR, the factors that affect tissue-material interactions are often studied in isolation or in small correlations due to the technical challenges involved in assessing them in vitro or in vivo. Consequently, the influence of protein conformation on the Ti bone implant surface design remains an unresolved research question. The objective of this review is to comprehensively evaluate the existing literature on the effect of surface parameters of Ti and its alloys in the stages of FBR, with a particular focus on protein adsorption and osteoimmunomodulation. This evaluation aims to systematically describe these effects on bone formation.

Tropoelastin modulates systemic and local tissue responses to enhance wound healing

Wound healing is facilitated by biomaterials-based grafts and substantially impacted by orchestrated inflammatory responses that are essential to the normal repair process. Tropoelastin (TE) based materials are known to shorten the period for wound repair but the mechanism of anti-inflammatory performance is not known. To explore this, we compared the performance of the gold standard Integra Dermal Regeneration Template (Integra), polyglycerol sebacate (PGS), and TE blended with PGS, in a murine full-thickness cutaneous wound healing study. Systemically, blending with TE favorably increased the F4/80+ macrophage population by day 7 in the spleen and contemporaneously induced elevated plasma levels of anti-inflammatory IL-10. In contrast, the PGS graft without TE prompted prolonged inflammation, as evidenced by splenomegaly and greater splenic granulocyte and monocyte fractions at day 14. Locally, the inclusion of TE in the graft led to increased anti-inflammatory M2 macrophages and CD4+T cells at the wound site, and a rise in Foxp3+ regulatory T cells in the wound bed by day 7. We conclude that the TE-incorporated skin graft delivers a pro-healing environment by modulating systemic and local tissue responses. STATEMENT OF SIGNIFICANCE: Tropoelastin (TE) has shown significant benefits in promoting the repair and regeneration of damaged human tissues. In this study, we show that TE promotes an anti-inflammatory environment that facilitates cutaneous wound healing. In a mouse model, we find that inserting a TE-containing material into a full-thickness wound results in defined, pro-healing local and systemic tissue responses. These findings advance our understanding of TE's restorative value in tissue engineering and regenerative medicine, and pave the way for clinical applications.

Biomaterial Fg/P(LLA-CL) regulates macrophage polarization and recruitment of mesenchymal stem cells after endometrial injury

The process of endometrial repair after injury involves the synergistic action of various cells including immune cells and stem cells. In this study, after combing Fibrinogen(Fg) with poly(L-lacticacid)-co-poly(ε-caprolactone)(P(LLA-CL)) by electrospinning, we placed Fg/P(LLA-CL) into the uterine cavity of endometrium-injured rats, and bioinformatic analysis revealed that Fg/P(LLA-CL) may affect inflammatory response and stem cell biological behavior. Therefore, we verified that Fg/P(LLA-CL) could inhibit the lipopolysaccharide (LPS)-stimulated macrophages from switching to the pro-inflammatory M1 phenotype in vitro. Moreover, in the rat model of endometrial injury, Fg/P(LLA-CL) effectively promoted the polarization of macrophages towards the anti-inflammatory M2 phenotype and enhanced the presence of mesenchymal stem cells at the injury site. Overall, Fg/P(LLA-CL) exhibits significant influence on macrophage polarization and stem cell behavior in endometrial injury, justifying further exploration for potential therapeutic applications in endometrial and other tissue injuries.

The regulatory effect of TiO2 nanotubes loaded with graphene oxide on macrophage polarization in an inflammatory environment

BACKGROUND

Excessive inflammation is a major cause of implant failure. The surface morphology, hydrophilicity, and loading of biomaterials are major properties modulating anti-inflammatory macrophage activation. This paper investigates the regulatory effects of modifying the surface of Titanium dioxide nanotubes (TNTs) with graphene oxide (GO) on the polarization of mouse monocyte macrophages (RAW264.7).

METHODS

TNT was produced by the anodic oxidation of titanium. GO was subsequently electrodeposited on the TNT to obtain a TNT-GO composite. The samples were characterised through scanning electron microscopy (SEM), Raman spectroscopy, and X-ray diffraction. RAW264.7 cells were separately seeded onto the surface of three groups of samples: pure Ti, TNT, and TNT-GO. Under the condition of lipopolysaccharide stimulation, the influence of the sample surfaces on the gene expression profiles was investigated through RNA sequence analysis. In addition, cell spreading was observed through SEM, cell adhesion and proliferation were analysed using the CCK8 assay, and the expression of inflammation-related factors was investigated by ELISA and cellular immunofluorescence staining. The production of reactive oxygen species (ROS) in the RAW264.7 cells on the surface of the three groups was detected via immunofluorescence staining.

RESULTS

The CCK8 results indicated that the adhesion and proliferation of the RAW264.7 cells were reduced on the TNT and TNT-GO surfaces. ELISA results revealed significant differences in the pro-inflammatory factors tumour necrosis factor-α and interleukin-6 secretion among the three groups at 24 h (p < 0.05). The secretion of pro-inflammatory factors significantly reduced and the expression of anti-inflammatory factor IL-10 increased on the TNT and TNT-GO surfaces. The RNA sequencing, ELISA, and cell immunofluorescence staining test results suggested that the inflammatory response of M1 polarization was reduced and the M2 polarization of macrophages was induced on the TNT-GO surface, which may be attributed to the reduction in ROS production.

CONCLUSIONS

Under lipopolysaccharide stimulation, the inflammatory response of the RAW264.7 cells was reduced and the M2 polarization of macrophages was promoted on the TNT-GO surface, which may be caused by the reduced ROS production. Consequently, the designed TNT-GO material is promising for implants owing to its excellent inflammation regulation ability.

Unraveling and Harnessing the Immune Response at the Cell-Biomaterial Interface for Tissue Engineering Purposes

Biomaterials are defined as "engineered materials" and include a range of natural and synthetic products, designed for their introduction into and interaction with living tissues. Biomaterials are considered prominent tools in regenerative medicine that support the restoration of tissue defects and retain physiologic functionality. Although commonly used in the medical field, these constructs are inherently foreign toward the host and induce an immune response at the material-tissue interface, defined as the foreign body response (FBR). A strong connection between the foreign body response and tissue regeneration is suggested, in which an appropriate amount of immune response and macrophage polarization is necessary to trigger autologous tissue formation. Recent developments in this field have led to the characterization of immunomodulatory traits that optimizes bioactivity, the integration of biomaterials and determines the fate of tissue regeneration. This review addresses a variety of aspects that are involved in steering the inflammatory response, including immune cell interactions, physical characteristics, biochemical cues, and metabolomics. Harnessing the advancing knowledge of the FBR allows for the optimization of biomaterial-based implants, aiming to prevent damage of the implant, improve natural regeneration, and provide the tools for an efficient and successful in vivo implantation.

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.

Genetically encoded biocompatible anti-coagulant protein-coated coronary artery stents drive endothelialization

In response to the critical demand for advancements in coronary artery stents, this study addresses the challenges associated with arterial recoil and restenosis post-angioplasty and the imperative to encourage rapid re-endothelialization for minimizing thrombosis risks. We employed an innovative approach inspired by mussel adhesion, incorporating placental anticoagulant protein (AnnexinV) on stent design. The introduction of a post-translationally modified catecholic amino acid L-3,4-dihydroxyphenylalanine (L-Dopa), mimicking mussel characteristics, allowed for effective surface modification of Stainless steel stents through genetic code engineering in AnnexinV (AnxDopa). The efficacy of AnxDopa was analyzed through microscale thermophoresis and flow cytometry, confirming AnxDopa's exceptional binding with phosphatidylserine and activated platelets. AnxDopa coated stainless steel demonstrates remarkable bio-, hemo-, and immuno-compatibility, preventing smooth muscle cell proliferation, platelet adhesion, and fibrin formation. It acts as an interface between the stent and biological fluid, which facilitates the anticoagulation and rapid endothelialization. Surface modification of SS verified through XPS analysis and contact angle measurement attests to the efficacy of AnxDopa mediated surface modification. The hydrophilic nature of the AnxDopa-coated surface enhanced the endothelialization through increased protein absorption. This approach represents a significant stride in developing coronary stents with improved biocompatibility and reduced restenosis risks, offering valuable contributions to scientific and clinical realms alike.

Mesenchymal Stem Cells-based Cell-free Therapy Targeting Neuroinflammation

Emerging from several decades of extensive research, key genetic elements and biochemical mechanisms implicated in neuroinflammation have been delineated, contributing substantially to our understanding of neurodegenerative diseases (NDDs). In this minireview, we discuss data predominantly from the past three years, highlighting the pivotal roles and mechanisms of the two principal cell types implicated in neuroinflammation. The review also underscores the extended process of peripheral inflammation that predates symptomatic onset, the critical influence of neuroinflammation, and their dynamic interplay in the pathogenesis of NDDs. Confronting these complex challenges, we introduce compelling evidence supporting the use of mesenchymal stem cell-based cell-free therapy. This therapeutic strategy includes the regulation of microglia and astrocytes, modulation of peripheral nerve cell inflammation, and targeted anti-inflammatory interventions specifically designed for NDDs, while also discussing engineering and safety considerations. This innovative therapeutic approach intricately modulates the immune system across the peripheral and nervous systems, with an emphasis on achieving superior penetration and targeted delivery. The insights offered by this review have significant implications for the better understanding and management of neuroinflammation.

Advanced Antimicrobial and Anti-Infective Strategies to Manage Peri-Implant Infection: A Narrative Review

Despite reductions in bacterial infection and enhanced success rate, the widespread use of systemic antibiotic prophylaxis in implant dentistry is controversial. This use has contributed to the growing problem of antimicrobial resistance, along with creating significant health and economic burdens. The basic mechanisms that cause implant infection can be targeted by new prevention and treatment methods which can also lead to the reduction of systemic antibiotic exposure and its associated adverse effects. This review aims to summarize advanced biomaterial strategies applied to implant components based on anti-pathogenic mechanisms and immune balance mechanisms. It emphasizes that modifying the dental implant surface and regulating the early immune response are promising strategies, which may further prevent or slow the development of peri-implant infection, and subsequent failure.

Biomaterial design for regenerating aged bone: materiobiological advances and paradigmatic shifts

China's aging demographic poses a challenge for treating prevalent bone diseases impacting life quality. As bone regeneration capacity diminishes with age due to cellular dysfunction and inflammation, advanced biomaterials-based approaches offer hope for aged bone regeneration. This review synthesizes materiobiology principles, focusing on biomaterials that target specific biological functions to restore tissue integrity. It covers strategies for stem cell manipulation, regulation of the inflammatory microenvironment, blood vessel regeneration, intervention in bone anabolism and catabolism, and nerve regulation. The review also explores molecular and cellular mechanisms underlying aged bone regeneration and proposes a database-driven design process for future biomaterial development. These insights may also guide therapies for other age-related conditions, contributing to the pursuit of 'healthy aging'.

CD4+ and CD8+ T cells reduce inflammation and promote bone healing in response to titanium implants

T cells are adaptive immune cells essential in pathogenic response, cancer, and autoimmune disorders. During the integration of biomaterials with host tissue, T cells modify the local inflammatory environment by releasing cytokines that promote inflammatory resolution following implantation. T cells are vital for the modulation of innate immune cells, recruitment and proliferation of mesenchymal stem cells (MSCs), and formation of functional tissue around the biomaterial implant. We have demonstrated that deficiency of αβ T cells promotes macrophage polarization towards a pro-inflammatory phenotype and attenuates MSC recruitment and proliferation in vitro and in vivo. The goal of this study was to understand how CD4+ and CD8+ T cells, subsets of the αβ T cell family, impact the inflammatory response to titanium (Ti) biomaterials. Deficiency of either CD4+ or CD8+ T cells increased the proportion of pro-inflammatory macrophages, lowered anti-inflammatory macrophages, and diminished MSC recruitment in vitro and in vivo. In addition, new bone formation at the implantation site was significantly reduced in T cell-deficient mice compared to T cell-competent mice. Deficiency of CD4+ T cells exacerbated these effects compared to CD8+ T cell deficiency. Our results show the importance of CD4+ and CD8+ T cells in modulating the inflammatory response and promoting new bone formation in response to modified Ti implants. STATEMENT OF SIGNIFICANCE: CD4+ and CD8+ T cells are essential in modulating the peri-implant microenvironment during the inflammatory response to biomaterial implantation. This study shows that deficiency of either CD4+ or CD8+ T cell subsets altered macrophage polarization and reduced MSC recruitment and proliferation at the implantation site.

Ferrocene-functionalized polydopamine film timely mediates M1-to-M2 macrophage polarization through adaptive wettability

Dynamical control of macrophage polarization from M1 (pro-inflammatory) to M2 (anti-inflammatory) at implant surfaces is essential for balancing innate immunity and tissue repair. In this aspect, the design of orthopedic implant that can response to inflammation microenvironment with transformation in surface properties has shown promising in timely driving M1-to-M2 macrophage transition. Considering excessive reactive oxygen species (ROS) contribute to macrophage M1 polarization and progression of inflammation, in this study, ferrocene modified polydopamine (PDA-Fc) films were deposited on plasma sprayed Ti coatings to endow the implants with ROS-responsive and -scavenging abilities. Plasma sprayed Ti (PST) coating and PDA modified PST coating (PST/PDA) served as control. The presence of PDA endowed PST/PDA and PST/PDA-Fc with free-radical scavenging abilities. Moreover, PST/PDA-Fc showed adaptive wettability as evidenced by increased hydrophilicity under H2O2 treatment. With respect to PST/PDA, PST/PDA-Fc exerted greater effects on inducing lipopolysaccharides-induced M1 macrophages to adopt M2-type macrophage phenotype, characterized by higher percentage of CD206-positive cells, increased cell elongation rate and higher expression level of anti-inflammatory cytokine arginase type 1. The results obtained in our study may provide a prospective approach for manipulating an appropriate immune response at implant surfaces.

Evaluation of nanoscale versus hybrid micro/nano surface topographies for endosseous implants

We examined the effect of a nanoscale titanium surface topography (D) versus two hybrid micro/nanoscale topographies (B and OS) on adherent mesenchymal stem cells (MSCs) and bone marrow derived macrophages (BMMs) function in cell culture and in vivo. In the in vitro study, compared to OS and B surfaces, D surface induced earlier and greater cell spreading, and earlier and profound mRNA expression of RUNX2, Osterix and BMP2 in MSCs. D surface induced earlier and higher expression of RUNX2 and BMP2 and lower expression of inflammatory genes in implant adherent cells in vivo. Measurement of osteogenesis at implant surfaces showed greater bone-to-implant contact at D versus OS surfaces after 21 days. We explored the cell population on the D and OS implant surfaces 24 h after placement using single-cell RNA sequencing and identified distinct cell clusters including macrophages, neutrophils and B cells. D surface induced lower expression and earlier reduction of inflammatory genes expression in BMMs in vitro. BMMs on D, B and OS surfaces demonstrated a marked increase of BMP2 expression after 1 and 3 days, and this increase was significantly higher on D surface at day 3. Our data implicates a dynamic process that may be influenced by nanotopography at multiple stages of osseointegration including initial immunomodulation, recruitment of MSCs and later osteoblastic differentiation leading to bone matrix production and mineralization. The results suggest that a nanoscale topography (D) favorably modulates adherent macrophage polarization toward anti-inflammatory and regenerative phenotypes and promotes the osteoinductive phenotype of adherent mesenchymal stem cells. STATEMENT OF SIGNIFICANCE: Our manuscript contains original data developed to define effects of a novel nanotopography on the process of osseointegration at the cell and tissue level.  Few studies have compared the effects of a nanoscale surface versus the more typical hybrid micro/nano-scale surfaces used today. We have utilized single-cell RNA sequencing for the first time to identify earliest cell populations on implant surfaces in vivo. We provide data indicating that the nanoscale surface acts upon both osteoprogenitor and immune cell (macrophages) to alter the process of bone formation in a surface-specific manner. This work represents new observations regarding osseointegration and immunomodulation.

Effects of glass-ceramic produced by the sol-gel route in macrophages recruitment and polarization into bone tissue regeneration

Effective bone substitute biomaterials remain an important challenge in patients with large bone defects. Glass ceramics produced by different synthesis routes may result in changes in the material physicochemical properties and consequently affect the success or failure of the bone healing response. To investigate the differences in the orchestration of the inflammatory and healing process in bone grafting and repair using different glass-ceramic routes production. Thirty male Wistar rats underwent surgical unilateral parietal defects filled with silicate glass-ceramic produced by distinct routes: BS - particulate glass-ceramic produced via the fusion/solidification route, and BG - particulate glass-ceramic produced via the sol-gel route. After 7, 14, and 21 days from biomaterial grafting, parietal bones were removed to be analyzed under H&E and Massons' Trichome staining, and immunohistochemistry for CD206, iNOS, and TGF-β. Our findings demonstrated that the density of lymphocytes and plasma cells was significantly higher in the BS group at 45, and 7 days compared to the BG group, respectively. Furthermore, a significant increase of foreign body giant cells (FBGCs) in the BG group at day 7, compared to BS was found, demonstrating early efficient recruitment of FBGCs against sol-gel-derived glass-ceramic particulate (BS group). According to macrophage profiles, CD206+ macrophages enhanced at the final periods of both groups, being significantly higher at 45 days of BS compared to the BG group. On the other hand, the density of transformation growth factor beta (TGF-β) positive cells on 21 days were the highest in BG, and the lowest in the BS group, demonstrating a differential synergy among groups. Noteworthy, TGF-β+ cells were significantly higher at 21 days of BG compared to the BS group. Glass-ceramic biomaterials can act differently in the biological process of bone remodeling due to their route production, being the sol-gel route more efficient to activate M2 macrophages and specific FBGCs compared to the traditional route. Altogether, these features lead to a better understanding of the effectiveness of inflammatory response for biomaterial degradation and provide new insights for further preclinical and clinical studies involved in bone healing.

Mesenchymal Stem Cell Transplantation in Type 1 Diabetes Treatment: Current Advances and Future Opportunity

Type 1 Diabetes (T1D) is characterized by hyperglycemia, and caused by a lack of insulin secretion. At present there is no cure for T1D and patients are dependent on exogenous insulin for lifelong, which seriously affects their lives. Mesenchymal stem cells (MSCs) can be differentiated to β cell-like cells to rescue the secretion of insulin and reconstruct immunotolerance to preserve the function of islet β cells. Due to the higher proportion of children and adolescents in T1D patients, the efficacy and safety issue of the application of MSC's transplant in T1D was primarily demonstrated and identified by human clinical trials in this review. Then we clarified the mechanism of MSCs to relieve the symptom of T1D and found out that UC-MSCs have no obvious advantage over the other types of MSCs, the autologous MSCs from BM or menstrual blood with less expanded ex vivo could be the better choice for clinical application to treat with T1D through documentary analysis. Finally, we summarized the advances of MSCs with different interventions such as genetic engineering in the treatment of T1D, and demonstrated the advantages and shortage of MSCs intervened by different treatments in the transplantation, which may enhance the clinical efficacy and overcome the shortcomings in the application of MSCs to T1D in future.

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.

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.

Immunomodulatory biomaterials against bacterial infections: Progress, challenges, and future perspectives

Bacterial infectious diseases are one of the leading causes of death worldwide. Even with the use of multiple antibiotic treatment strategies, 4.95 million people died from drug-resistant bacterial infections in 2019. By 2050, the number of deaths will reach 10 million annually. The increasing mortality may be partly due to bacterial heterogeneity in the infection microenvironment, such as drug-resistant bacteria, biofilms, persister cells, intracellular bacteria, and small colony variants. In addition, the complexity of the immune microenvironment at different stages of infection makes biomaterials with direct antimicrobial activity unsatisfactory for the long-term treatment of chronic bacterial infections. The increasing mortality may be partly attributed to the biomaterials failing to modulate the active antimicrobial action of immune cells. Therefore, there is an urgent need for effective alternatives to treat bacterial infections. Accordingly, the development of immunomodulatory antimicrobial biomaterials has recently received considerable interest; however, a comprehensive review of their research progress is lacking. In this review, we focus mainly on the research progress and future perspectives of immunomodulatory antimicrobial biomaterials used at different stages of infection. First, we describe the characteristics of the immune microenvironment in the acute and chronic phases of bacterial infections. Then, we highlight the immunomodulatory strategies for antimicrobial biomaterials at different stages of infection and their corresponding advantages and disadvantages. Moreover, we discuss biomaterial-mediated bacterial vaccines' potential applications and challenges for activating innate and adaptive immune memory. This review will serve as a reference for future studies to develop next-generation immunomodulatory biomaterials and accelerate their translation into clinical practice.

Material matters: exploring the interplay between natural biomaterials and host immune system

Biomaterials are widely used for various medical purposes, for instance, implants, tissue engineering, medical devices, and drug delivery systems. Natural biomaterials can be obtained from proteins, carbohydrates, and cell-specific sources. However, when these biomaterials are introduced into the body, they trigger an immune response which may lead to rejection and failure of the implanted device or tissue. The immune system recognizes natural biomaterials as foreign substances and triggers the activation of several immune cells, for instance, macrophages, dendritic cells, and T cells. These cells release pro-inflammatory cytokines and chemokines, which recruit other immune cells to the implantation site. The activation of the immune system can lead to an inflammatory response, which can be beneficial or detrimental, depending on the type of natural biomaterial and the extent of the immune response. These biomaterials can also influence the immune response by modulating the behavior of immune cells. For example, biomaterials with specific surface properties, such as charge and hydrophobicity, can affect the activation and differentiation of immune cells. Additionally, biomaterials can be engineered to release immunomodulatory factors, such as anti-inflammatory cytokines, to promote a tolerogenic immune response. In conclusion, the interaction between biomaterials and the body's immune system is an intricate procedure with potential consequences for the effectiveness of therapeutics and medical devices. A better understanding of this interplay can help to design biomaterials that promote favorable immune responses and minimize adverse reactions.

Magnesium bioactive glass hybrid functionalized polyetheretherketone with immunomodulatory function to guide cell fate and bone regeneration

Polyetheretherketone (PEEK) is being increasingly recognized as a highly promising polymer implant in orthopaedics due to its advantageous biocompatibility, favorable processability, and radiation resistance. Nonetheless, the long-term application of PEEK implants in vivo faces challenges due to unfavorable post-implantation inflammatory and immune reactions, which result in suboptimal osseointegration rates. Hence, biofunctionalizing the surface of PEEK implants emerges as a viable strategy to enhance osseointegration and increase the success rate. In this study, we developed a multifunctional PEEK implant through the in-situ incorporation of chitosan-coated bioactive glass nanoparticles (BGNs). This approach can impart immunomodulatory properties and enhance the potential for osseointegration. The resulting biofunctionalized PEEK material exhibited multiple beneficial effects. For instance, it facilitated M2 phenotypic polarization of macrophages, diminished the expression of inflammatory factors, and enhanced the osteogenic differentiation of bone marrow mesenchymal stem cells (BMSCs) in vitro. Moreover, it exhibited an improved capacity for osseointegration when tested in vivo. The findings of the experiment highlighted the pivotal and complex role of the biofunctionalized PEEK implant in maintaining typical bone immunity and metabolism. The study proposes that the application of chitosan-BGNs presents a straightforward approach to developing multifunctional implants with the ability to promote biomineralization and immunomodulation, specifically tailored for orthopaedic applications.

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.

3D-printed scaffolds with 2D hetero-nanostructures and immunomodulatory cytokines provide pro-healing microenvironment for enhanced bone regeneration

Three-dimensional (3D) printing technology is driving forward the progresses of various engineering fields, including tissue engineering. However, the pristine 3D-printed scaffolds usually lack robust functions in stimulating desired activity for varied regeneration applications. In this study, we combined the two-dimensional (2D) hetero-nanostructures and immuno-regulative interleukin-4 (IL-4) cytokines for the functionalization of 3D-printed scaffolds to achieve a pro-healing immuno-microenvironment for optimized bone injury repair. The 2D hetero-nanostructure consists of graphene oxide (GO) layers, for improved cell adhesion, and black phosphorous (BP) nanosheets, for the continuous release of phosphate ions to stimulate cell growth and osteogenesis. In addition, the 2D hetero-nanolayers facilitated the adsorption of large content of immuno-regulative IL-4 cytokines, which modulated the polarization of macrophages into M2 phenotype. After in vivo implantation in rat, the immuno-functioned 3D-scaffolds achieved in vivo osteo-immunomodulation by building a pro-healing immunological microenvironment for better angiogenesis and osteogenesis in the defect area and thus facilitated bone regeneration. These results demonstrated that the immuno-functionalization of 3D-scaffolds with 2D hetero-nanostructures with secondary loading of immuno-regulative cytokines is an encouraging strategy for improving bone regeneration.

The integration of peri-implant soft tissues around zirconia abutments: Challenges and strategies

Stable soft tissue integration around the implant abutment attenuates pathogen penetration, protects underlying bone tissue, prevents peri-implantitis and is essential in maintaining long-term implant stability. The desire for "metal free" and "aesthetic restoration" has favored zirconia over titanium abutments, especially for implant restorations in the anterior region and for patients with thin gingival biotype. Soft tissue attachment to the zirconia abutment surface remains a challenge. A comprehensive review of advances in zirconia surface treatment (micro-design) and structural design (macro-design) affecting soft tissue attachment is presented and strategies and research directions are discussed. Soft tissue models for abutment research are described. Guidelines for development of zirconia abutment surfaces that promote soft tissue integration and evidence-based references to inform clinical choice of abutment structure and postoperative maintenance are presented.

Role of dendritic cells in MYD88-mediated immune recognition and osteoinduction initiated by the implantation of biomaterials

Bone substitute material implantation has become an important treatment strategy for the repair of oral and maxillofacial bone defects. Recent studies have shown that appropriate inflammatory and immune cells are essential factors in the process of osteoinduction of bone substitute materials. Previous studies have mainly focused on innate immune cells such as macrophages. In our previous work, we found that T lymphocytes, as adaptive immune cells, are also essential in the osteoinduction procedure. As the most important antigen-presenting cell, whether dendritic cells (DCs) can recognize non-antigen biomaterials and participate in osteoinduction was still unclear. In this study, we found that surgical trauma associated with materials implantation induces necrocytosis, and this causes the release of high mobility group protein-1 (HMGB1), which is adsorbed on the surface of bone substitute materials. Subsequently, HMGB1-adsorbed materials were recognized by the TLR4-MYD88-NFκB signal axis of dendritic cells, and the inflammatory response was activated. Finally, activated DCs release regeneration-related chemokines, recruit mesenchymal stem cells, and initiate the osteoinduction process. This study sheds light on the immune-regeneration process after bone substitute materials implantation, points out a potential direction for the development of bone substitute materials, and provides guidance for the development of clinical surgical methods.

Reduction of neutrophil extracellular traps accelerates inflammatory resolution and increases bone formation on titanium implants

Neutrophils are the most abundant immune cells in the blood and the first cells to be recruited to the biomaterial implantation site. Neutrophils are fundamental in recruiting mononuclear leukocytes to mount an immune response at the injury site. Neutrophils exert significant pro-inflammatory effects through the release of cytokines and chemokines, degranulation and release of myeloperoxidase (MPO) and neutrophil elastase (NE), and the production of large DNA-based networks called neutrophil extracellular traps (NETs). Neutrophils are initially recruited and activated by cytokines and pathogen- and damage-associated molecular patterns, but little is known about how the physicochemical composition of the biomaterial affects their activation. This study aimed to understand how ablating neutrophil mediators (MPO, NE, NETs) affected macrophage phenotype in vitro and osseointegration in vivo. We discovered that NET formation is a crucial mediator of pro-inflammatory macrophage activation, and inhibition of NET formation significantly suppresses macrophage pro-inflammatory phenotype. Furthermore, reducing NET formation accelerated the inflammatory phase of healing and produced greater bone formation around the implanted biomaterial, suggesting that NETs are essential regulators of biomaterial integration. Our findings emphasize the importance of the neutrophil response to implanted biomaterials and highlight innate immune cells' regulation and amplification signaling during the initiation and resolution of the inflammatory phase of biomaterial integration. STATEMENT OF SIGNIFICANCE: Neutrophils are the most abundant immune cells in blood and are the first to be recruited to the injury/implantation site where they exert significant pro-inflammatory effects. This study aimed to understand how ablating neutrophil mediators affected macrophage phenotype in vitro and bone apposition in vivo. We found that NET formation is a crucial mediator of pro-inflammatory macrophage activation. Reducing NET formation accelerated the inflammatory phase of healing and produced greater appositional bone formation around the implanted biomaterial, suggesting that NETs are essential regulators of biomaterial integration.

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.

An immunometabolic patch facilitates mesenchymal stromal/stem cell therapy for myocardial infarction through a macrophage-dependent mechanism

Mesenchymal stromal/stem cells (MSCs) have emerged as a promising approach against myocardial infarction. Due to hostile hyperinflammation, however, poor retention of transplanted cells seriously impedes their clinical applications. Proinflammatory M1 macrophages, which rely on glycolysis as their main energy source, aggravate hyperinflammatory response and cardiac injury in ischemic region. Here, we showed that the administration of an inhibitor of glycolysis, 2-deoxy-d-glucose (2-DG), blocked the hyperinflammatory response within the ischemic myocardium and subsequently extended effective retention of transplanted MSCs. Mechanistically, 2-DG blocked the proinflammatory polarization of macrophages and suppressed the production of inflammatory cytokines. Selective macrophage depletion abrogated this curative effect. Finally, to avoid potential organ toxicity caused by systemic inhibition of glycolysis, we developed a novel chitosan/gelatin-based 2-DG patch that directly adhered to the infarcted region and facilitated MSC-mediated cardiac healing with undetectable side effects. This study pioneered the application of an immunometabolic patch in MSC-based therapy and provided insights into the therapeutic mechanism and advantages of this innovative biomaterial.

Immune cell response to orthopedic and craniofacial biomaterials depends on biomaterial composition

Materials for craniofacial and orthopedic implants are commonly selected based on mechanical properties and corrosion resistance. The biocompatibility of these materials is typically assessed in vitro using cell lines, but little is known about the response of immune cells to these materials. This study aimed to evaluate the inflammatory and immune cell response to four common orthopedic materials [pure titanium (Ti), titanium alloy (TiAlV), 316L stainless steel (SS), polyetheretherketone (PEEK)]. Following implantation into mice, we found high recruitment of neutrophils, pro-inflammatory macrophages, and CD4+ T cells in response to PEEK and SS implants. Neutrophils produced higher levels of neutrophil elastase, myeloperoxidase, and neutrophil extracellular traps in vitro in response to PEEK and SS than neutrophils on Ti or TiAlV. Macrophages co-cultured on PEEK, SS, or TiAlV increased polarization of T cells towards Th1/Th17 subsets and decreased Th2/Treg polarization compared to Ti substrates. Although SS and PEEK are considered biocompatible materials, both induce a more robust inflammatory response than Ti or Ti alloy characterized by high infiltration of neutrophils and T cells, which may cause fibrous encapsulation of these materials. STATEMENT OF SIGNIFICANCE: Materials for craniofacial and orthopedic implants are commonly selected based on their mechanical properties and corrosion resistance. This study aimed to evaluate the immune cell response to four common orthopedic and craniofacial biomaterials: pure titanium, titanium-aluminum-vanadium alloy, 316L stainless steel, and PEEK. Our results demonstrate that while the biomaterials tested have been shown to be biocompatible and clinically successful, the inflammatory response is largely driven by chemical composition of the biomaterials.

Immunomodulatory nanotherapeutic approaches for periodontal tissue regeneration

Periodontitis is an infection-induced inflammatory disease characterized by progressive destruction of tooth supporting tissues, which, if left untreated, can result in tooth loss. The destruction of periodontal tissues is primarily caused by an imbalance between the host immune protection and immune destruction mechanisms. The ultimate goal of periodontal therapy is to eliminate inflammation and promote the repair and regeneration of both hard and soft tissues, so as to restore the physiological structure and function of periodontium. Advancement in nanotechnologies has enabled the development of nanomaterials with immunomodulatory properties for regenerative dentistry. This review discusses the immune mechanisms of the major effector cells in the innate and adaptive immune systems, the physicochemical and biological properties of nanomaterials, and the research advancements in immunomodulatory nanotherapeutic approaches for the management of periodontitis and the regeneration of periodontal tissues. The current challenges, and prospects for future applications of nanomaterials are then discussed so that researchers at the intersections of osteoimmunology, regenerative dentistry and materiobiology will continue to advance the development of nanomaterials for improved periodontal tissue regeneration.

Reambulation following hindlimb unloading attenuates disuse-induced changes in murine fracture healing

Patients with bone and muscle loss from prolonged disuse have higher risk of falls and subsequent fragility fractures. In addition, fracture patients with continued disuse and/or delayed physical rehabilitation have worse clinical outcomes compared to individuals with immediate weight-bearing activity following diaphyseal fracture. However, the effects of prior disuse followed by physical reambulation on fracture healing cellular processes and adjacent bone and skeletal muscle recovery post-injury remains poorly defined. To bridge this knowledge gap and inform future treatment and rehabilitation strategies for fractures, a preclinical model of fracture healing with a history of prior unloading with and without reambulation was employed. First, skeletally mature male and female C57BL/6J mice (18 weeks) underwent hindlimb unloading by tail suspension (HLU) for 3 weeks to induce significant bone and muscle loss modeling enhanced bone fragility. Next, mice had their right femur fractured by open surgical dissection (stabilized with 24-gauge pin). The, mice were randomly assigned to continued HLU or allowed normal weight-bearing reambulation (HLU + R). Mice given normal cage activity throughout the experiment served as healthy age-matched controls. All mice were sacrificed 4-days (DPF4) or 14-days (DPF14) following fracture to assess healing and uninjured hindlimb musculoskeletal properties (6-10 mice per treatment/biological sex). We found that continued disuse following fracture lead to severely diminished uninjured hindlimb skeletal muscle mass (gastrocnemius and soleus) and femoral bone volume adjacent to the fracture site compared to healthy age-matched controls across mouse sexes. Furthermore, HLU led to significantly decreased periosteal expansion (DPF4) and osteochondral tissue formation by DPF14, and trends in increased osteoclastogenesis (DPF14) and decreased woven bone vascular area (DPF14). In contrast, immediate reambulation for 2 weeks after fracture, even following a period of prolonged disuse, was able to increase hindlimb skeletal tissue mass and increase osteochondral tissue formation, albeit not to healthy control levels, in both mouse sexes. Furthermore, reambulation attenuated osteoclast formation seen in woven bone tissue undergoing disuse. Our results suggest that weight-bearing skeletal loading in both sexes immediately following fracture may improve callus healing and prevent further fall risk by stimulating skeletal muscle anabolism and decreasing callus resorption compared to minimal or delayed rehabilitation regimens.

Bone marrow stromal cells generate an osteoinductive microenvironment when cultured on titanium-aluminum-vanadium substrates with biomimetic multiscale surface roughness

Osseointegration of titanium-based implants possessing complex macroscale/microscale/mesoscale/nanoscale (multiscale) topographies support a direct and functional connection with native bone tissue by promoting recruitment, attachment and osteoblastic differentiation of bone marrow stromal cells (MSCs). Recent studies show that the MSCs on these surfaces produce factors, including bone morphogenetic protein 2 (BMP2) that can cause MSCs not on the surface to undergo osteoblast differentiation, suggesting they may produce an osteogenic environmentin vivo. This study examined if soluble factors produced by MSCs in contact with titanium-aluminum-vanadium (Ti6Al4V) implants possessing a complex multiscale biomimetic topography are able to induce osteogenesis ectopically. Ti6Al4V disks were grit-blasted and acid-etched to create surfaces possessing macroscale and microscale roughness (MM), micro/meso/nanoscale topography (MN), and macro/micro/meso/nanoscale topography (MMN^TM). Polyether-ether-ketone (PEEK) disks were also fabricated by machining to medical-grade specifications. Surface properties were assessed by scanning electron microscopy, contact angle, optical profilometry, and x-ray photoelectron spectroscopy. MSCs were cultured in growth media (GM). Proteins and local factors in their conditioned media (CM) were measured on days 4, 8, 10 and 14: osteocalcin, osteopontin, osteoprotegerin, BMP2, BMP4, and cytokines interleukins 6, 4 and 10 (IL6, IL4, and IL10). CM was collected from D14 MSCs on MMN^TMand tissue culture polystyrene (TCPS) and lyophilized. Gel capsules containing active demineralized bone matrix (DBM), heat-inactivated DBM (iDBM), and iDBM + MMN-GM were implanted bilaterally in the gastrocnemius of athymic nude mice (N= 8 capsules/group). Controls included iDBM + GM; iDBM + TCPS-CM from D5 to D10 MSCs; iDBM + MMN-CM from D5 to D10; and iDBM + rhBMP2 (R&D Systems) at a concentration similar to D5-D10 production of MSCs on MMN^TMsurfaces. Legs were harvested at 35D. Bone formation was assessed by micro computed tomography and histomorphometry (hematoxylin and eosin staining) with the histology scored according to ASTM 2529-13. DNA was greatest on PEEK at all time points; DNA was lowest on MN at early time points, but increased with time. Cells on PEEK exhibited small changes in differentiation with reduced production of BMP2. Osteoblast differentiation was greatest on the MN and MMN^TM, reflecting increased production of BMP2 and BMP4. Pro-regenerative cytokines IL4 and IL10 were increased on Ti-based surfaces; IL6 was reduced compared to PEEK. None of the media from TCPS cultures was osteoinductive. However, MMN-CM exhibited increased bone formation compared to iDBM and iDBM + rhBMP2. Furthermore, exogenous rhBMP2 alone, at the concentration found in MMN-CM collected from D5 to D10 cultures, failed to induce new bone, indicating that other factors in the CM play a critical role in that osteoinductive microenvironment. MSCs cultured on MMN^TMTi6Al4V surfaces differentiate and produce an increase in local factors, including BMP2, and the CM from these cultures can induce ectopic bone formation compared to control groups, indicating that the increased bone formation arises from the local response by MSCs to a biomimetic, multiscale surface topography.

Family with sequence similarity 20 member B regulates osteogenic differentiation of bone marrow mesenchymal stem cells on titanium surfaces

Successful bone regeneration on titanium (Ti) surfaces is a key process in dental implant treatment. Bone marrow mesenchymal stem cells (BMSCs) are fundamental cellular components of this process, and their early recruitment, proliferation, and differentiation into bone-forming osteoblasts are crucial. A proteoglycan (PG)-rich layer has been reported to exist between Ti surfaces and bones; however, the molecules that could potentially affect the formation of this layer remain unknown. Family with sequence similarity 20 member B (FAM20B) is a newly identified kinase that regulates the synthesis of glycosaminoglycans, an important component of the PG-rich layer. Because FAM20B is also closely associated with bone development, in this study, we examined the function of FAM20B in osteogenic differentiation of BMSCs on Ti surfaces. For this, BMSC cell lines with knocked down FAM20B (shBMSCs) were cultured on Ti surfaces. The results showed that the depletion of FAM20B reduced the formation of a PG-rich layer between the Ti surfaces and cells. The shBMSCs exhibited downregulated expression of osteogenic marker genes (ALP and OCN) and decreased mineral deposition. Moreover, shBMSCs reduced the molecular levels of p-ERK1/2, which plays an important role in MSC osteogenesis. The nuclear translocation of RUNX2, an important transcription factor for osteogenic differentiation, on the Ti surfaces is inhibited by the depletion of FAM20B in BMSCs. Moreover, the depletion of FAM20B reduced the transcriptional activity of RUNX2, which is important in regulating the expression of osteogenic genes. STATEMENT OF SIGNIFICANCE: Bone healing and regeneration on implanted titanium surfaces is a cell-material interaction. Such an interaction is enabled by bone marrow mesenchymal stem cells (BMSCs), and their early recruitment, proliferation, and differentiation into bone-forming osteoblasts are essential for bone healing and osseointegration. In this study, we found that the family with sequence similarity 20-B influenced the formation of a proteoglycan rich layer between BMSCs and the titanium surface and regulated the differentiation of BMSCs into bone-forming osteoblasts. We believe that our study contributes significantly to the further exploration of bone healing and osseointegration mechanisms on implanted titanium surfaces.

Modulating neuroinflammation through molecular, cellular and biomaterial-based approaches to treat spinal cord injury

The neuroinflammatory response that is elicited after spinal cord injury contributes to both tissue damage and reparative processes. The complex and dynamic cellular and molecular changes within the spinal cord microenvironment result in a functional imbalance of immune cells and their modulatory factors. To facilitate wound healing and repair, it is necessary to manipulate the immunological pathways during neuroinflammation to achieve successful therapeutic interventions. In this review, recent advancements and fresh perspectives on the consequences of neuroinflammation after SCI and modulation of the inflammatory responses through the use of molecular-, cellular-, and biomaterial-based therapies to promote tissue regeneration and functional recovery will be discussed.

Osseointegration of Titanium Implants in a Botox-Induced Muscle Paralysis Rat Model Is Sensitive to Surface Topography and Semaphorin 3A Treatment

Reduced skeletal loading associated with many conditions, such as neuromuscular injuries, can lead to bone fragility and may threaten the success of implant therapy. Our group has developed a botulinum toxin A (botox) injection model to imitate disease-reduced skeletal loading and reported that botox dramatically impaired the bone formation and osseointegration of titanium implants. Semaphorin 3A (sema3A) is an osteoprotective factor that increases bone formation and inhibits bone resorption, indicating its potential therapeutic role in improving osseointegration in vivo. We first evaluated the sema3A effect on whole bone morphology following botox injections by delivering sema3A via injection. We then evaluated the sema3A effect on the osseointegration of titanium implants with two different surface topographies by delivering sema3A to cortical bone defect sites prepared for implant insertion and above the implants after insertion using a copper-free click hydrogel that polymerizes rapidly in situ. Implants had hydrophobic smooth surfaces (PT) or multiscale biomimetic micro/nano topography (SLAnano). Sema3A rescued the botox-impaired bone formation. Furthermore, biomimetic Ti implants improved the bone-to-implant contact (BIC) and mechanical properties of the integrated bone in the botox-treated rats, which sema3A enhanced. This study demonstrated the value of biomimetic approaches combining multiscale topography and biologics in improving the clinical outcomes of implant therapy.

Two-Dimensional Mg2 Si Nanosheet-Enabled Sustained Hydrogen Generation for Improved Repair and Regeneration of Deeply Burned Skin

Molecular hydrogen holds a high potential for wound healing owing to its anti-inflammatory effect and high biosafety, but commonly used hydrogen administration routes hardly achieve the sustained supply of high-dosage hydrogen, limiting hydrogen therapy efficacy. Here, two-dimensional Mg₂ Si nanosheet (MSN) is exploited as a super-persistent hydrogen-releasing nanomaterial with high biocompatibility, and the incorporation of MSN into the chitosan/hyaluronic acid hydrogel (MSN@CS/HA) is developed as a dressing to repair deeply burned skin. The MSN@CS/HA hydrogel dressing can continuously generate hydrogen molecules for about 1 week in the physiological conditions in support of local, long-term, and plentiful hydrogen supply and remarkably promotes the healing and regeneration of deep second-degree and third-degree burn wounds without visible scar and toxic side effect. Mechanistically, a sustained supply of hydrogen molecules induces anti-inflammatory M2 macrophage polarization in time by enhancing CCL2 (chemokine C-C motif ligand 2) expression to promote angiogenesis and reduce fibrosis and also enhances the proliferation and migration capability of skin cells directly and indirectly by locally scavenging overexpressed reactive oxygen species, synergistically favoring wound repair. The proposed synthesis method, therapeutic strategy, and mechanisms will open a window for synthesizing a variety of MSene nanomaterials and developing their various proangiogenesis applications besides wound healing.

Cell-free immunomodulatory biomaterials mediated in situ periodontal multi-tissue regeneration and their immunopathophysiological processes

Cell-free biomaterials-inducing endogenous in situ multi-tissue regeneration is very challenging and applying advanced immunomodulatory biomaterials can be an effective strategy to overcome it. In-depth knowledge of the immunopathophysiological mechanisms should be acquired before applying such an immunomodulation strategy. In this study, we implanted different immunoregulatory cell-free biomaterials into periodontal multi-tissue defects and showed that the outcome of multi-tissue regeneration is closely regulated by the immune reaction. The underlying immunopathophysiological processes, including the blood clotting response and fibrinoid necrosis, innate and adaptive immune response, local and systemic immune reaction, growth factors release, and stem cells recruitment, were revealed. The implantation of biomaterials with anti-inflammatory properties could direct the immunopathophysiological process and make it more favorable for in situ multi-tissue regeneration, ultimately enabling the regeneration of the periodontal ligament, the acellular cementum matrix, and the alveolar bone in the periodontium. These findings further confirm the effectiveness of immunomodulatory based strategy and the unveiling of their immunopathophysiological processes could provide some favorable theoretical bases for the development of advanced cell-free immunomodulatory multi-tissue regenerative biomaterials.

Topography-mediated immunomodulation in osseointegration; Ally or Enemy

Osteoimmunology is at full display during endosseous implant osseointegration. Bone formation, maintenance and resorption at the implant surface is a result of bidirectional and dynamic reciprocal communication between the bone and immune cells that extends beyond the well-defined osteoblast-osteoclast signaling. Implant surface topography informs adherent progenitor and immune cell function and their cross-talk to modulate the process of bone accrual. Integrating titanium surface engineering with the principles of immunology is utilized to harness the power of immune system to improve osseointegration in healthy and diseased microenvironments. This review summarizes current information regarding immune cell-titanium implant surface interactions and places these events in the context of surface-mediated immunomodulation and bone regeneration. A mechanistic approach is directed in demonstrating the central role of osteoimmunology in the process of osseointegration and exploring how regulation of immune cell function at the implant-bone interface may be used in future control of clinical therapies. The process of peri-implant bone loss is also informed by immunomodulation at the implant surface. How surface topography is exploited to prevent osteoclastogenesis is considered herein with respect to peri-implant inflammation, osteoclastic precursor-surface interactions, and the upstream/downstream effects of surface topography on immune and progenitor cell function.

Functionalized multidimensional biomaterials for bone microenvironment engineering applications: Focus on osteoimmunomodulation

As bone biology develops, it is gradually recognized that bone regeneration is a pathophysiological process that requires the simultaneous participation of multiple systems. With the introduction of osteoimmunology, the interplay between the immune system and the musculoskeletal diseases has been the conceptual framework for a thorough understanding of both systems and the advancement of osteoimmunomodulaty biomaterials. Various therapeutic strategies which include intervention of the surface characteristics or the local delivery systems with the incorporation of bioactive molecules have been applied to create an ideal bone microenvironment for bone tissue regeneration. Our review systematically summarized the current research that is being undertaken in the field of osteoimmunomodulaty bone biomaterials on a case-by-case basis, aiming to inspire more extensive research and promote clinical conversion.

The role of dendritic cells in the immunomodulation to implanted biomaterials

Considering the substantial role played by dendritic cells (DCs) in the immune system to bridge innate and adaptive immunity, studies on DC-mediated immunity toward biomaterials principally center on their adjuvant effects in facilitating the adaptive immunity of codelivered antigens. However, the effect of the intrinsic properties of biomaterials on dendritic cells has not been clarified. Recently, researchers have begun to investigate and found that biomaterials that are nonadjuvant could also regulate the immune function of DCs and thus affect subsequent tissue regeneration. In the case of proteins adsorbed onto biomaterial surfaces, their intrinsic properties can direct their orientation and conformation, forming “biomaterial-associated molecular patterns (BAMPs)”. Thus, in this review, we focused on the intrinsic physiochemical properties of biomaterials in the absence of antigens that affect DC immune function and summarized the underlying signaling pathways. Moreover, we preliminarily clarified the specific composition of BAMPs and the interplay between some key molecules and DCs, such as heat shock proteins (HSPs) and high mobility group box 1 (HMGB1). This review provides a new direction for future biomaterial design, through which modulation of host immune responses is applicable to tissue engineering and immunotherapy.