Promoting tissue regeneration by modulating the immune system

Effects of exosomes derived from activated corneal stromal keratocytes on the inflammation, proliferation, neuroprotection and epithelial-mesenchymal transition in retinal pigment epithelium cells

AIMS

This study investigated the effects of activated keratocyte-derived exosomes (aKExo) on retinal pigment epithelial (RPE) cells in-vitro, focusing on cell viability, inflammatory cytokine expression, and neuroprotective properties.

MATERIALS AND METHODS

Keratocytes were cultured, and exosomes were extracted and characterized using transmission electron microscopy (TEM), scanning electron microscopy (SEM), flow cytometry, and dynamic light scattering (DLS). RPE cells, isolated from a human donor, were confirmed via RPE65 expression. aKExo effects on RPE cells were assessed using MTT assay at concentrations from 10-1 (35 μg/mL) to 10-5 (3.5 × 10-3 μg/mL). The optimal aKExo concentration (10-5) enhanced cell viability and exhibited the highest proliferative potential compared to the control group, making it the optimal dose for subsequent experiments including gene expression analysis, and ELISA.

KEY FINDINGS

aKExo downregulated IL-6 mRNA (0.70 ± 0.06, p = 0.0009) and marginally reduced TGF-β mRNA (0.75 ± 0.16, p = 0.0575). ELISA confirmed a reduction in IL-6 (31.33 ± 5.77 pg/mL vs. 50.22 ± 13.47 pg/mL, p = 0.0894) and TGF-β (8.91 ± 0.16 pg/mL vs. 11.39 ± 1.49 pg/mL, p = 0.0460). No significant changes were observed for IL-1β expression or other epithelial-mesenchymal transition (EMT)-related genes (α-SMA, ZEB-1, β-catenin). Neuroprotective genes NGF (4.34 ± 1.05, p = 0.0053) and CD90 (1.55 ± 0.25, p = 0.0184) were significantly upregulated, while VEGF-A was elevated (1.65 ± 0.15, p = 0.0018).

SIGNIFICANCE

These findings highlight aKExo's immunomodulatory, neuroprotective, and anti-EMT effects, suggesting potential therapeutic applications for retinal disorders, while noting that VEGF-A upregulation requires further investigation.

Local delivery of lipid-based nanoparticles containing microbial nucleic acid for osteoimmunomodulation

Osteoimmunomodulation is a strategy to promote bone regeneration in implants by modifying the immune environment. CpG-containing oligonucleotides type C (CpG ODN C) and Polyinosinic:polycytidylic acid (Poly[I:C]) are analogs of microbial nucleic acids that have been studied for various immunotherapeutic applications. This research investigates the potential of CpG ODN C and Poly(I:C) as an osteoimmunomodulatory agent for bone regenerative purposes. We encapsulated each nucleic acid in a lipid-based nanoparticle to facilitate the delivery into intracellular pathogen recognition receptors in immune cells. The lipid-based nanoparticles were ±250 nm in size with a negative charge (-36 to -40 mV) and an encapsulation efficiency of ±60 %. Lipid-based nanoparticles containing nucleic acids, Lip/CpG ODN C and Lip/Poly(I:C), increased the production of TNF, IL-6, and IL-10 by primary human macrophages compared to free-form nucleic acids. Conditioned medium from macrophages treated with CpG ODN C (10 µg/ml) and Lip/CpG ODN C (0.1, 1, and 10 µg/ml) promoted osteoblast differentiation of human mesenchymal stromal cells by 2.6-fold and 3-fold, respectively; no effect was seen for Lip/Poly(I:C). Bone implants were prepared, consisting of a biphasic calcium phosphate scaffold, bone morphogenetic protein (BMP) 2, and lipid-based nanoparticles suspended in gelatin methacryloyl (GelMA) hydrogel. Implants were evaluated for de novo bone formation in an extra-skeletal implantation model in rabbits for 5 weeks. Based on the particles suspended in GelMA, six groups of implants were prepared: Lip/CpG ODN C, Lip/Poly(I:C), Lip (empty), CpG ODN C, Poly(I:C), and a control group consisting of empty GelMA. After 5 weeks, healthy bone tissue formed in all of the implants with active osteoblast and osteoclast activity, however, the amount of new bone volume and scaffold degradation were similar for all implants. We suggest that the working concentrations of the nucleic acids employed were inadequate to induce a relevant inflammatory response. Additionally, the dosage of BMP-2 used may potentially mask the immune-stimulatory effect. Lip/CpG ODN C holds potential as a bioactive agent for osteoimmunomodulation, although further in vivo demonstration should corroborate the current in vitro findings.

Osteoimmunomodulation by bone implant materials: harnessing physicochemical properties and chemical composition

Chronic inflammation at bone defect sites can impede regenerative processes, but local immune responses can be adjusted to promote healing. Regulating the osteoimmune microenvironment, particularly through macrophage polarization, has become a key focus in bone regeneration research. While bone implants are crucial for addressing significant bone defects, they are often recognized by the immune system as foreign, triggering inflammation that leads to bone resorption and implant issues like fibrous encapsulation and aseptic loosening. Developing osteoimmunomodulatory implants offers a promising approach to transforming destructive inflammation into healing processes, enhancing implant integration and bone regeneration. This review explores strategies based on tuning the physicochemical attributes and chemical composition of materials in engineering osteoimmunomodulatory and pro-regenerative bone implants.

Regeneration and defense: unveiling the molecular interplay in plants

In both plants and animals, tissue or organ regeneration typically follows wounding, which also activates defense responses against pathogenic microbes and herbivores. Both intrinsic and environmental cues guide the molecular decisions between regeneration and defense. In animal studies, extensive research has highlighted the role of various microbes - including pathogenic, commensal, and beneficial species - in influencing the signaling interplay between immunity and regeneration. Conversely, most plant regeneration studies are conducted under sterile conditions, which leaves a gap in our understanding of how plant innate immunity influences regeneration pathways. Recent findings have begun to elucidate the roles of key defense pathways in modulating plant regeneration and the crosstalk between these two processes. These studies also explore how microbes might influence the molecular choice between defense and regeneration in plants. This review examines the molecular mechanisms governing the balance between plant regeneration and innate immunity, with a focus on the emerging role of aging and microbial interactions in shaping these processes.

Decellularized Extracellular Matrix Scaffold Loaded with Regulatory T Cell-Conditioned Medium Induces M2 Macrophage Polarization

Biomaterials often induce local inflammatory responses following implantation. Scaffolds that cause continuous M1 polarization typically hinder tissue healing and regeneration. Regulating the transformation of macrophages to the M2 phenotype in the inflammatory environment is crucial. We propose that regulatory T cell-conditioned medium (Treg CM) effectively promotes M2 polarization of macrophages induced by decellularized extracellular matrix (dECM) materials in inflammatory environments. In vitro results showed that in the presence of dECM, Treg CM induces the polarization of RAW264.7 macrophages to M2 and inhibits M1 macrophage polarization under inflammatory conditions (lipopolysaccharide + IFN-γ). Additionally, dECM promotes the polarization of bone marrow-derived macrophages (BMDMs) to M2, while Treg CM further promotes M2 polarization and inhibits M1 polarization in an inflammatory environment. These findings were confirmed by transcriptome sequencing. Treg CM inhibited IκB kinase/NF-κB signaling and cellular responses to oxidative stress. In vivo subcutaneous transplantation showed an increase in M2 macrophages, a decrease in M1 macrophages, and an increased M2/M1 ratio in dECM materials loaded with Treg CM. These results suggest that Treg CM can create a pro-M2 polarized microenvironment for dECM, guiding immune responses toward favorable tissue regeneration. Ultimately, this research highlights the potential of Treg CM as a therapeutic approach to modulate the immune response and improve the efficacy of regenerative biomaterials.

Systemic effects of oral tolerance improve the healing of several and concomitant wounds on different parts of the body

Oral tolerance is an immunological phenomenon that results from protein intake and that has systemic effects on inflammation. Previous research has shown that parenteral injection of tolerated proteins reduces inflammatory infiltrate and improves skin wound healing. Herein, we tested whether the injection of tolerated proteins improves the healing of several wounds on different parts of the body, such as on the skin of the back and on the external ear (the auricle). To induce oral tolerance to ovalbumin (OVA), eight-week old C57BL/6 mice drank egg white diluted 1:5 in water for 3 consecutive days. The control mice drank water. Seven days after oral treatment, mice were submitted to excisional injuries on the skin of the back (6 mm) and ears (4 mm). Minutes before the injuries, the mice received an intraperitoneal injection of OVA + Al(OH)3. Seven and 40 days after the injuries, tissue samples were collected and processed for histological analysis of the wounds. The results showed that the injection of OVA in animals that drank OVA reduced the inflammatory infiltrate in all lesions. In addition, injection of OVA in animals that drank OVA promoted better organization of the extracellular matrix, with thicker and intertwined collagen fibers in the neodermis, resulting in smaller scars on the skin. Furthermore, the healing area of the ears of OVA-tolerant animals showed chondrocyte aggregates and less obvious fibrous scar tissue compared with control animals. In conclusion, systemic effects of oral tolerance positively influenced the healing of several lesions on different parts of the body.

The bone microenvironment: new insights into the role of stem cells and cell communication in bone regeneration

Mesenchymal stem cells (MSCs) play a crucial role in bone formation and remodeling. Intrinsic genetic factors and extrinsic environmental cues regulate their differentiation into osteoblasts. Within the bone microenvironment, a complex network of biochemical and biomechanical signals orchestrates bone homeostasis and regeneration. In addition, the crosstalk among MSCs, immune cells, and neighboring cells-mediated by extracellular vesicles and non-coding RNAs (such as circular RNAs and micro RNAs) -profoundly influences osteogenic differentiation and bone remodeling. Recent studies have explored specific signaling pathways that contribute to effective bone regeneration, highlighting the potential of manipulating the bone microenvironment to enhance MSC functionality. The integration of advanced biomaterials, gene editing techniques, and controlled delivery systems is paving the way for more targeted and efficient regenerative therapies. Furthermore, artificial intelligence could improve bone tissue engineering, optimize biomaterial design, and enable personalized treatment strategies. This review explores the latest advancements in bone regeneration, emphasizing the intricate interplay among stem cells, immune cells, and signaling molecules. By providing a comprehensive overview of these mechanisms and their clinical implications, we aim to shed light on future research directions in this rapidly evolving field.

Life-threatening risk factors contribute to the development of diseases with the highest mortality through the induction of regulated necrotic cell death

Chronic diseases affecting the cardiovascular system, diabetes mellitus, neurodegenerative diseases, and various other organ-specific conditions, involve different underlying pathological processes. However, they share common risk factors that contribute to the development and progression of these diseases, including air pollution, hypertension, obesity, high cholesterol levels, smoking and alcoholism. In this review, we aim to explore the connection between four types of diseases with different etiologies and various risk factors. We highlight that the presence of risk factors induces regulated necrotic cell death, leading to the release of damage-associated molecular patterns (DAMPs), ultimately resulting in sterile inflammation. Therefore, DAMP-mediated inflammation may be the link explaining how risk factors can lead to the development and maintenance of chronic diseases. To explore these processes, we summarize the main cell death pathways activated by the most common life-threatening risk factors, the types of released DAMPs and how these events are associated with the pathophysiology of diseases with the highest mortality. Various risk factors, such as smoking, air pollution, alcoholism, hypertension, obesity, and high cholesterol levels induce regulated necrosis. Subsequently, the release of DAMPs leads to chronic inflammation, which increases the risk of many diseases, including those with the highest mortality rates.

DNA-based hydrogels for bone regeneration: A promising tool for bone organoids

DNA-based hydrogels stand out for bone regeneration due to their exceptional biocompatibility and programmability. These hydrogels facilitate the formation of spatial bone structures through bulk hydrogel fabricating, microsphere formatting, and 3D printing. Furthermore, the bone microenvironment can be finely tuned by leveraging the degradation products, nanostructure, targeting, and delivery capabilities inherent to DNA-based materials. In this review, we underscore the advantages of DNA-based hydrogels, detailing their composition, gelation techniques, and structure optimization. We then delineate three critical elements in the promotion of bone regeneration using DNA-based hydrogels: (i) osteogenesis driven by phosphate ions, plasmids, and oligodeoxynucleotides (ODNs) that enhance mineralization and promote gene and protein expression; (ii) vascularization facilitated by tetrahedral DNA nanostructures (TDNs) and aptamers, which boosts gene expression and targeted release; (iii) immunomodulation achieved through loaded factors, TDNs, and bound ions that stimulate macrophage polarization and exhibit antibacterial properties. With these advantages and properties, these DNA-based hydrogels can be used to construct bone organoids, providing an innovative tool for disease modeling and therapeutic applications in bone tissue engineering. Finally, we discuss the current challenges and future prospects, emphasizing the potential impacts and applications in regenerative medicine.

Improving the Wound Healing Process: Pivotal role of Mesenchymal stromal/stem Cells and Immune Cells

Wound healing, a physiological process, involves several different types of cells, from immune cells to non-immune cells, including mesenchymal stromal/stem cells (MSC), and their interactions. Immune cells including macrophages, neutrophils, dendritic cells (DC), innate lymphoid cells (ILC), natural killer (NK) cells, and B and T lymphocytes participate in wound healing by secreting various mediators and interacting with other cells. MSCs, as self-renewing, fast proliferating, and multipotent stromal/stem cells, are found in a wide variety of tissues and critically involved in different phases of wound healing by secreting various molecules that help to improve tissue healing and regeneration. In this review, first, we described the four main phases of wound healing, second, we reviewed the function of MSCs, MSC secretome and immune cells in improving the progress of wound repair (mainly focusing on skin wound healing), third, we explained the immune cells/MSCs interactions in the process of wound healing and regeneration, and finally, we introduce clinical applications of MSCs to improve the process of wound healing.

Biopolymeric Scaffolds with Melatonin for Tissue Engineering-A Review

Melatonin, a natural hormone with antioxidant, anti-inflammatory, and regenerative properties, has gained increasing attention in tissue engineering for its ability to enhance the therapeutic potential of biopolymeric scaffolds. These scaffolds, designed to mimic the extracellular matrix, provide structural support and a bioactive environment for tissue regeneration. By integrating melatonin, researchers aim to create multifunctional scaffolds that promote cell proliferation, modulate inflammatory responses, and improve wound healing outcomes. Challenges in utilizing melatonin include maintaining its stability under light, heat, and oxygen exposure, and optimizing its release profile for sustained therapeutic effects. Innovative fabrication methods, such as electrospinning, 3D printing, and lyophilization, have enabled precise control over scaffold architecture and melatonin delivery. These techniques ensure enhanced interactions with target tissues and tailored regeneration processes. Combining melatonin with growth factors, cytokines, and antimicrobial agents offers the potential for multifunctional applications, from chronic wound management to bone and nerve regeneration. Continued research in this field promises transformative solutions in regenerative medicine, expanding the clinical applicability of melatonin-enriched scaffolds. This review highlights the current progress, challenges, and opportunities associated with harnessing melatonin's therapeutic potential within tissue engineering frameworks.

Adipose-Derived Stem Cell Specific Affinity Peptide-Modified Adipose Decellularized Scaffolds for Promoting Adipogenesis

Adipose-derived stem cells (ADSCs) are known to promote angiogenesis and adipogenesis. However, their limited ability to efficiently target and integrate into specific tissues poses a major challenge for ADSC-based therapies. In this study, we identified a seven-amino acid peptide sequence (P7) with high specificity for ADSCs using phage display technology. P7 was then covalently conjugated to decellularized adipose-derived matrix (DAM), creating an "ADSC homing device" designed to recruit ADSCs both in vitro and in vivo. The P7-conjugated DAM significantly enhanced ADSC adhesion and proliferation in vitro. After being implanted into rat subcutaneous tissue, immunofluorescence staining after 14 days revealed that P7-conjugated DAM recruited a greater number of ADSCs, promoting angiogenesis and adipogenesis in the surrounding tissue. Moreover, CD206 immunostaining at 14 days indicated that P7-conjugated DAM facilitated the polarization of macrophages to the M2 phenotype at the implantation site. These findings demonstrate that the P7 peptide has a high affinity for ADSCs, and its conjugation with DAM significantly improves ADSC recruitment in vivo. This approach holds great potential for a wide range of applications in material surface modification.

Therapeutic components of acupuncture stimulation based on characteristics of sensory nerve and nervous signaling pathway

Acupuncture, a therapeutic practice rooted in traditional Chinese medicine and integrated with modern neuroscience, achieves its effects by stimulating sensory nerves at specific anatomical points known as acupoints. This review systematically explores the therapeutic components of acupuncture, emphasizing the interplay between sensory nerve characteristics and neural signaling pathways. Key factors such as acupoint location, needling depth, stimulation intensity, retention time, and the induction of sensations (e.g., Deqi) are analyzed for their roles in neural activation and clinical outcomes. The review highlights how variations in spinal segment targeting, tissue-specific receptor activation, and stimulation modalities (e.g., manual acupuncture, electroacupuncture, moxibustion) influence therapeutic effects. Emerging evidence underscores the significance of ion channels, dermatomes, myotomes, and gene-specific pathways in mediating systemic effects. Additionally, the differential roles of mechanical, thermal and nociceptive stimuli and the temporal dynamics of sensory and immune responses are addressed. While insights from animal models have advanced our understanding, their translation to clinical practice requires further investigation. This comprehensive review identifies critical parameters for optimizing acupuncture therapy, advocating for individualized treatment strategies informed by neuroanatomical and neurophysiological principles, ultimately enhancing its precision and efficacy in modern medicine. Please cite this article as: Wie HS, Kim SN. Therapeutic components of acupuncture stimulation based on characteristics of sensory nerve and nervous signaling pathway. J Integr Med. 2025; 23(2): 106-112.

Dichloroacetate: A metabolic game-changer in alleviating macrophage inflammation and enhancing recovery after myocardial infarction

BACKGROUND

Dichloroacetate (DCA) has shown potential in modulating cellular metabolism and inflammation, particularly in cardiac conditions. This study investigates DCA's protective effects in a mouse model of myocardial infarction (MI), focusing on its ability to enhance cardiac function, reduce inflammation, and shift macrophage polarization from the pro-inflammatory M1 to the anti-inflammatory M2 phenotype.

METHODS

An acute MI model was created using left anterior descending coronary artery ligation. Mice were assigned to four groups: normal control, MI control, MI + 50 mM DCA, and MI + 100 mM DCA. Cardiac fibrosis and injury were assessed through H&E staining. Cardiac function was evaluated via echocardiography, and serum levels of creatine kinase-MB (CK-MB) and lactate dehydrogenase (LDH) were measured. Inflammation and apoptosis were analyzed through immunohistochemistry, ELISA, western blotting, and flow cytometry in heart tissue and RAW264.7 cells. Additionally, macrophage polarization and relevant signaling pathways were examined.

RESULTS

DCA significantly improved cardiac function in MI mice, evidenced by reduced myocardial injury and lower CK-MB and LDH levels. It also decreased inflammatory cytokines (TNF-α, IL-6 and IL-1β) and facilitated macrophage polarization from M1 to M2. Western blotting revealed that DCA inhibited iNOS and COX2 while enhancing Arg1 expression, alongside improved mitochondrial function and reduced apoptosis. Additionally, by injecting AAV-PDHK4 (pyruvate dehydrogenase kinase) into MI mice, we found that DCA effectively inhibited the progression of MI through the suppression of PDHK4.

CONCLUSION

DCA protects against myocardial infarction by enhancing cardiac function, reducing inflammation, and promoting macrophage polarization, likely through inhibition of PDHK4 and NF-κB pathways, positioning it as a potential therapeutic strategy for cardiac repair post-MI.

In Vitro Bioactivity Evaluation of IL-4 and SDF-1 Mimicking Peptides Engineered to Enhance Skeletal Muscle Reconstruction

Skeletal muscle regeneration depends on satellite cells, which, in response to injury, activate, proliferate, and reconstruct damaged tissue. However, under certain conditions, such as large injuries or myopathies, this process may not be properly executed, and muscle function may be affected. Thus, pro-regenerative actions, such as the use of various factors or cells, are widely tested as a tool to improve muscle regeneration. In the current study, we designed peptides derived from the IL-4 and SDF-1 proteins, namely IL-4-X, IL-4-Y, SDF-1-X, and SDF-1-Y. We showed that these peptides can bind to appropriate receptors and can adopt proper structure in solution. Importantly, we documented, using in vitro culture, that they do not negatively affect the cells that are present and active in skeletal muscles, such as myoblasts and fibroblasts, bone marrow stromal cells, as well as induced pluripotent stem cells, which can serve as a source of myoblasts. The presence of peptides did not affect cell proliferation compared to untreated cells. In vitro culture and differentiation protocols documented that selected IL-4 and SDF-1 peptides increased cell migration and inhibited undesirable adipogenic differentiation. Thus, we proved that these peptides are safe to use in in vivo studies aimed at improving skeletal muscle regeneration.

Radiation therapy-induced normal tissue damage: involvement of EMT pathways and role of FLASH-RT in reducing toxicities

Radiation therapy (RT) is fundamental to the fight against cancer because of its exceptional ability to target and destroy cancer cells. However, conventional radiation therapy can significantly affect the adjacent normal tissues, leading to fibrosis, inflammation, and decreased organ function. This tissue damage not only reduces the quality of life but also prevents the total elimination of cancer. The transformation of epithelial cells into mesenchymal-like cells, termed epithelial-mesenchymal transition (EMT), is essential for processes such as fibrosis, embryogenesis, and wound healing. Conventional radiation therapy increases the asymmetric activation of fibrotic and inflammatory pathways, and the resulting chronic fibrotic changes and organ dysfunction are linked to radiation-induced epithelial-mesenchymal transition. Recent advances in radiation therapy, namely flash radiation therapy (FLASH-RT), have the potential to widen the therapeutic index. Radiation delivered by FLASH-RT at very high dose rates (exceeding 40 Gy/s) can protect normal tissue from radiation-induced damage, a phenomenon referred to as the "FLASH effect". Preclinical studies have demonstrated that FLASH-RT successfully inhibits processes associated with fibrosis and epithelial-mesenchymal transition, mitigates damage to normal tissue, and enhances regeneration. Three distinct types of EMT have been identified: type-1, associated with embryogenesis; Type-2, associated with injury potential; and type-3, related with cancer spread. The regulation of EMT via pathways, including TGF-β/SMAD, WNT/β-catenin, and NF-κB, is essential for radiation-induced tissue remodelling. This study examined radiation-induced EMT, TGF-β activity, multiple signalling pathways in fibrosis, and the potential of FLASH-RT to reduce tissue damage. FLASH-RT is a novel approach to treat chronic tissue injury and fibrosis post-irradiation by maintaining epithelial properties and regulating mesenchymal markers including vimentin and N-cadherin. Understanding these pathways will facilitate the development of future therapies that can alleviate fibrosis, improve the efficacy of cancer therapy, and improve the quality of life of patients.

Rational design of 3D-printed scaffolds for breast tissue engineering using structural analysis

Best cosmetic outcomes of breast reconstruction using tissue engineering techniques rely on the scaffold architecture and material, which are currently both to be determined. This study suggests an approach for a rational design of breast-shaped scaffold architecture, in which structural analysis is implemented to predict its stiffness and adjust it to that of the native tissue. This approach can help achieve the goal of optimal scaffold architecture for breast tissue engineering. Based on specifications defined in a preliminary implantation study of a non-rationally designed scaffold, and using analytical modeling and finite element analysis, we rationally designed a polycaprolactone made, 3D-printed, highly porous, breast-shaped scaffold with a stiffness similar to the breast adipose tissue. This scaffold had an architecture of a double-shelled dome connected by pillars, with no bottom to allow direct contact of its fat graft with the host's blood vessels (shelled hemisphere adaptive design (SHAD)). To demonstrate the potential of the SHAD scaffold in breast tissue engineering, a proof-of-concept study was performed, in which SHAD scaffolds were embedded with human adipose derived mesenchymal stem cells, isolated from lipoaspirates, and implanted in nod-scid-gamma mouse model with a delayed fat graft injection. After 4 weeks of implantation, the SHAD implants were vascularized with a viable fat graft, indicating the suitability of the SHAD scaffold for breast tissue engineering.

Polysaccharide-Based Self-Healing Hydrogel for pH-Induced Smart Release of Lauric Acid to Accelerate Wound Healing

It is highly desirable yet significantly challenging to fabricate an injectable, self-healing, controlled-release wound dressing that is responsive to the alkaline pH of the wounds. Herein, we propose a facile approach to prepare pH-responsive chitosan-oxidized carboxymethyl cellulose (CS-o-CMC) hydrogel constructs in which gelation was achieved via electrostatic and Schiff base formation. Importantly, the Schiff base was formed in acidic medium and the final pH of pregel solution was intrinsically raised to 7.0-7.4 due to the cross-linking by β-glycerol phosphate. The self-healing behavior of the hydrogel was an enthalpy-driven process and efficient in alkaline compared to acidic pH. The pH responsiveness offered a controlled release of lauric acid (LA) from CS-o-CMC/LA hydrogel and regulated the M2 polarization. Overall, reduction in inflammation led to rapid vascularization, reepithelialization, and significantly accelerated wound healing in rats. Our findings demonstrate a promising strategy for developing injectable, immunomodulatory wound dressings tailored to the challenging environment of wounds.

Autophagy in Tissue Repair and Regeneration

Autophagy is a cellular recycling system that, through the sequestration and degradation of intracellular components regulates multiple cellular functions to maintain cellular homeostasis and survival. Dysregulation of autophagy is closely associated with the development of physiological alterations and human diseases, including the loss of regenerative capacity. Tissue regeneration is a highly complex process that relies on the coordinated interplay of several cellular processes, such as injury sensing, defense responses, cell proliferation, differentiation, migration, and cellular senescence. These processes act synergistically to repair or replace damaged tissues and restore their morphology and function. In this review, we examine the evidence supporting the involvement of the autophagy pathway in the different cellular mechanisms comprising the processes of regeneration and repair across different regenerative contexts. Additionally, we explore how modulating autophagy can enhance or accelerate regeneration and repair, highlighting autophagy as a promising therapeutic target in regenerative medicine for the development of autophagy-based treatments for human diseases.

Synergistic Enhancement of Antibacterial and Osteo-Immunomodulatory Activities of Titanium Implants via Dual-Responsive Multifunctional Surfaces

Bone implant-associated infections and inflammations, primarily caused by bacteria colonization, frequently result in unsuccessful procedures and pose significant health risks to patients. To mitigate these challenges, the development of engineered implants with spatiotemporal regulation capabilities, designed to inhibit bacterial survival and modulate immune responses in the early stage, while promoting bone defect healing in the late stage is proposed. The implants are functionalized with ε-poly-l-lysine-phenylboronic acid (PP) via dynamic boronic ester bonds, which facilitate its release through a reactive oxygen species (ROS) and pH-responsive strategy, thereby establishing an antibacterial microenvironment on and around the implants. Additionally, the dynamic metal coordination interaction facilitates the loading and sustained release of Sr2+ under an acidic environment, providing immunomodulatory and osteogenic effects. The ROS/pH-responsive feature, coupled with the implant-bone tissue integration process, affords precise spatiotemporal regulation of the Ti-TA-Sr-PP implants. This strategy represents a promising approach for the preparation of advanced bone implants.

Immunomodulation with M2 macrophage-derived extracellular vesicles for enhanced titanium implant osseointegration under diabetic conditions

M2 macrophage-derived extracellular vesicles (M2-EVs) demonstrate the capacity to reduce pro-inflammatory M1 macrophage formation, thereby restoring the M1-M2 macrophage balance and promoting immunoregulation. However, the efficacy of M2-EVs in regulating macrophage polarization and subsequently enhancing osseointegration around titanium (Ti) implants in patients with diabetes mellitus (DM) remains to be elucidated. In this study, Ti implants were coated with polydopamine to facilitate M2-EVs adherence. In vitro experiment results demonstrated that M2-EVs could carry miR-23a-3p, inhibiting NOD-like receptor protein3(NLRP3) inflammasome activation in M1 macrophage and reducing the levels of inflammatory cytokines such as IL-1β by targeting NEK7. This improved the M1-M2 macrophage balance and enhanced mineralization on the Ti implant surfaces. The in vivo experiment results demonstrated that in diabetic conditions, the nanocoated M2-EVs significantly promoted high-quality bone deposition around the Ti implants. The current results provide a novel perspective for simple and effective decoration of M2-EVs on Ti implants; clinically, the method may afford osteoimmunomodulatory effects enhancing implant osseointegration in patients with DM.

Regenerative Functions of Regulatory T Cells and Current Strategies Utilizing Mesenchymal Stem Cells in Immunomodulatory Tissue Regeneration

BACKGROUND

Regulatory T cells (Tregs) are essential for maintaining immune homeostasis and facilitating tissue regeneration by fostering an environment conducive to tissue repair. However, in damaged tissues, excessive inflammatory responses can overwhelm the immunomodulatory capacity of Tregs, compromising their functionality and potentially hindering effective regeneration. Mesenchymal stem cells (MSCs) play a key role in enhancing Treg function. MSCs enhance Treg activity through indirect interactions, such as cytokine secretion, and direct interactions via membrane proteins.

METHODS

This review examines the regenerative functions of Tregs across various tissues, including bone, cartilage, muscle, and skin, and explores strategies to enhance Treg functionality using MSCs. Advanced techniques, such as the overexpression of relevant genes in MSCs, are highlighted for their potential to further enhance Treg function. Additionally, emerging technologies utilizing extracellular vesicles (EVs) and cell membrane-derived vesicles derived from MSCs offer promising alternatives to circumvent the potential side effects associated with live cell therapies. This review proposes approaches to enhance Treg function and promote tissue regeneration and also outlines future research directions.

RESULTS AND CONCLUSION

This review elucidates recent technological advancements aimed at enhancing Treg function using MSCs and examines their potential to improve tissue regeneration efficiency.

Advanced Immunomodulatory Biomaterials for Therapeutic Applications

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

The Order of Concurrent Training Affects Acute Immunological Stress Responses and Measures of Muscular Fitness in Female Youth Judo Athletes

This study aimed to examine the acute effects of concurrent muscle strength and sport-specific endurance exercise order on immunological stress responses, metabolic response, muscular-fitness, and rating-of-perceived-exertion (RPE) in highly trained youth female judo athletes. Thirteen female participants randomly performed two concurrent training (CT) sessions; strength-endurance and endurance-strength. Immune response, metabolic response, muscular fitness (i.e., countermovement jump-derived force and power [CMJ-force and CMJ-power]), and RPE were measured at different time points (i.e., PRE, MID, POST, POST6h, and POST22h). There were significant time × order interactions for lymphocytes (p = 0.006, ES = 1.31), granulocyte-lymphocyte ratio (p = 0.002, ES = 1.56), and systemic inflammation index (p = 0.029, ES = 1.11), blood glucose and lactate (p < 0.001, ES = 2.09 and p = 0.0018, ES = 1.51, respectively), CMJ-force (p = 0.033, ES = 1.26), and CMJ-power (p = 0.007, ES = 1.40) as well as RPE (p < 0.001, ES = 2.05). CT-induced acute (i.e., POST) but not delayed (i.e., POST6h and POST22h) order-dependent immune cell count alterations in highly trained youth female judo athletes. All markers of the immune system went back to baseline values at POST22h. Metabolic responses were slightly higher following the endurance exercise (irrespective of the applied exercise order). CMJ-measures and RPE fluctuated during both CT sessions but returned to baseline 6 h post-exercise.

Maternal Roughage Sources Influence the Gastrointestinal Development of Goat Kids by Modulating the Colonization of Gastrointestinal Microbiota

During pregnancy and lactation, maternal nutrition is linked to the full development of offspring and may have long-term or lifelong effects. However, the influence of the doe's diet on the gastrointestinal (GI) tract of young kids remains largely unexplored. Therefore, we investigated the effects of doe roughage sources (alfalfa hay, AH, or corn straw, CS) during pregnancy and lactation on kid growth, GI morphology, barrier function, metabolism, immunity, and microbiome composition. The results indicate that, compared with the CS group, does fed an AH diet had significantly higher feed intake (p < 0.01). However, CS-fed does exhibited higher neutral detergent fiber (NDF) digestibility (p < 0.05). There were no significant differences in animal (doe or kid) weight among the groups (p > 0.05). In the rumen of goat kids, the AH group exhibited a higher papillae width and increased levels of interleukin-10 (IL-10) compared with the CS group (p < 0.05). In the jejunum of goat kids, the AH group showed a higher villus-height-to-crypt-depth (VH/CD) ratio, as well as elevated levels of secretory immunoglobulin A (SIgA), immunoglobulin G (IgG), IL-10, acetate, and total volatile fatty acids (TVFAs), when compared with the CS group (p < 0.05). Transcriptome analysis revealed that the source of roughage in does was associated with changes in the GI transcriptome of the kids. Differentially expressed genes (DEGs) in the rumen were mainly associated with tissue development and immune regulation, while the DEGs in the jejunum were mainly associated with the regulation of transferase activity. Spearman correlation analyses indicated significant associations between GI DEGs and phenotypic indicators related to GI development, immunity, and metabolism. LEfSe analysis identified 14 rumen microbial biomarkers and 6 jejunum microbial biomarkers. Notably, these microorganisms were also enriched in the rumen or day 28 milk of the does. Further microbial composition analysis revealed significant correlations between the rumen and milk microbiomes of does and the rumen or jejunum microbiomes of kids. Association analyses indicated that microbial biomarkers interact with host genes, thereby affecting the development and function of the GI system. Additionally, correlation analyses revealed significant association between milk metabolites and the rumen and jejunum microbiomes of kids. This study demonstrated that maternal diet significantly influences the development of microbial ecosystems in offspring by modulating microbial communities and metabolite composition. The early colonization of GI microorganisms is crucial for the structural development, barrier function, immune capacity, and microbial metabolic activity of the GI system.

Regional Gene Therapy for Bone Tissue Engineering: A Current Concepts Review

The management of segmental bone defects presents a complex reconstruction challenge for orthopedic surgeons. Current treatment options are limited by efficacy across the spectrum of injury, morbidity, and cost. Regional gene therapy is a promising tissue engineering strategy for bone repair, as it allows for local implantation of nucleic acids or genetically modified cells to direct specific protein expression. In cell-based gene therapy approaches, a variety of different cell types have been described including mesenchymal stem cells (MSCs) derived from multiple sources-bone marrow, adipose, skeletal muscle, and umbilical cord tissue, among others. MSCs, in particular, have been well studied, as they serve as a source of osteoprogenitor cells in addition to providing a vehicle for transgene delivery. Furthermore, MSCs possess immunomodulatory properties, which may support the development of an allogeneic "off-the-shelf" gene therapy product. Identifying an optimal cell type is paramount to the successful clinical translation of cell-based gene therapy approaches. Here, we review current strategies for the management of segmental bone loss in orthopedic surgery, including bone grafting, bone graft substitutes, and operative techniques. We also highlight regional gene therapy as a tissue engineering strategy for bone repair, with a focus on cell types and cell sources suitable for this application.

Inhalation of macrophage membrane-coated hydrogel microparticles for inflammation alleviation of acute lung injury in vivo

Hydrogel microparticles (HMPs) have many advantages for biomedical applications, particularly for minimally invasive therapy, for example, acute lung injury (ALI) that is characterized by high levels of reactive oxygen species (ROS) and pro-inflammatory mediators in the microenvironment. In this study, ROS-scavenging and pro-inflammatory cytokine-neutralizing HMPs were designed and prepared by using a membrane emulsification device. The HMPs were composed of double bond-modified hyaluronic acid and ROS-cleavable hyperbranched poly(acrylate-capped thioketone-containing ethylene glycol) (HBPAK) containing thioketal linkages and unsaturated double bonds. Surface-coating of inflammatory macrophage (M1) cell membranes was performed to obtain the membrane-coated HBPAK HMPs (mem HMPs) via electrostatic force. The mem HMPs exhibited strong ROS-scavenging and anti-inflammatory properties both in vitro and in vivo. After administered by inhalation in an ALI mouse model, the mem HMPs reduced neutrophil infiltration and tissue oxidative damage, thereby alleviating lung inflammation. Our results suggest that the mem HMPs could serve as a potential therapeutic platform for treating inflammatory diseases with high efficiency. STATEMENT OF SIGNIFICANCE: Hydrogel microparticles (HMPs) with minimally invasive delivery are advantageous for acute lung injury (ALI) characterized by high levels of reactive oxygen species (ROS) and pro-inflammatory mediators. Herein, ROS-scavenging and pro-inflammatory cytokine-neutralizing HMPs were prepared by copolymerizing double bond-modified hyaluronic acid and ROS-cleavable hyperbranched poly(acrylate-capped thioketone-containing ethylene glycol) (HBPAK) containing thioketal bonds and unsaturated double bonds in a membrane emulsification device. The HMPs covered with inflammatory macrophage (M1) cell membranes (mem HMPs) exhibited strong ROS-scavenging and anti-inflammation properties, reduced neutrophil infiltration and tissue oxidative damage, thereby alleviating lung inflammation.

RNA sequencing reveals key factors modulating TNFα-stimulated odontoblast-like differentiation of dental pulp stem cells

Inflammation is a complex host response to harmful infections or injuries, playing both beneficial and detrimental roles in tissue regeneration. Notably, clinical dentinogenesis associated with caries development occurs within an inflammatory environment. Reparative dentinogenesis is closely linked to intense inflammation, which triggers the recruitment and differentiation of dental pulp stem cells (DPSCs) into the dentin lineage. Understanding how inflammatory responses influence DPSCs is essential for elucidating the mechanisms underlying dentin and pulp regeneration. Given the limited data on this process, a broad approach is employed here to gain a deeper understanding of the complex mechanisms involved and to identify downstream signaling targets. This study aims to investigate the role of inflammation and the complement receptor C5L2 in the odontoblastic differentiation of DPSCs and the associated transcriptomic changes using poly-A RNA sequencing (RNA-seq). RNA-seq techniques provide insight into the transcriptome of a cell, offering higher coverage and greater resolution of its dynamic nature. Following inflammatory stimulation, DPSCs exhibit significantly altered gene profiles, including marked upregulation of key odontogenic genes, highlighting the critical role of inflammation in dentinogenesis. We demonstrate that TNFα-treated odontoblast-like differentiating DPSCs, under C5L2 modulation, exhibit significant differential gene expression and transcriptomic changes. The data presented may provide new avenues for experimental approaches to uncover pathways in dentinogenesis by identifying specific transcription factors and gene profiles.

α-Ketoglutaric Acid Reprograms Macrophages by Altering Energy Metabolism to Promote the Regeneration of Small-Diameter Vascular Grafts

Small-diameter vascular grafts still cannot clinically replace autologous blood vessels due to high restenosis rates caused by long-term inflammatory infiltration. Foreign body reactions to vascular grafts induce macrophages to adopt the pro-inflammatory M1 phenotype, releasing inflammatory factors such as interleukin-1β (IL-1β) and tumor necrosis factor-α (TNF-α). This induces a phenotypic switch in smooth muscle cells, eventually leading to intimal hyperplasia. Herein, we constructed small-diameter artificial vascular grafts capable of modulating immune responses through the controlled release of α-ketoglutaric acid (α-KG). Our findings verify that the delivery of α-KG reprograms the macrophage phenotype from a pro-inflammatory M1 to an anti-inflammatory and pro-repair M2 phenotype by regulating the energy metabolism of the tricarboxylic acid cycle (TAC). More interestingly, the delivery of α-KG positively influences the behavior of vascular cells by enhancing the proliferation of human umbilical vein endothelial cells (HUVECs) and inhibiting the expansion of mouse aortic vascular smooth muscle cells (MOVAS), thereby reducing vascular restenosis. In vivo evaluation in rabbit carotid artery replacement confirms the optimal performance of α-KG-doped vascular grafts in terms of endothelial coverage and long-term patency. Collectively, our work presents a promising approach for creating artificial vascular grafts with inflammatory regulation to ensure rapid endothelialization and sustained patency.

An Overview on Bioactive Glasses for Bone Regeneration and Repair: Preparation, Reinforcement, and Applications

Synthetic bone transplantation has emerged in recent years as a highly promising strategy to address the major clinical challenge of bone tissue defects. In this field, bioactive glasses (BGs) have been widely recognized as a viable alternative to traditional bone substitutes due to their unique advantages, including favorable biocompatibility, pronounced bioactivity, excellent biodegradability, and superior osseointegration properties. This article begins with a comprehensive overview of the development and success of BGs in bone tissue engineering, and then focuses on their composite reinforcement systems with biodegradable metals, calcium-phosphorus (Ca-P)-based bioceramics, and biodegradable medical polymers, respectively. Moreover, the article outlines some frequently used manufacturing methods for three-dimensional BG-based bone bioscaffolds and highlights the remarkable achievements of these scaffolds in the field of bone defect repair in recent years. Lastly, based on the many potential challenges encountered in the preparation and application of BGs, a brief outlook on their future directions is presented. This review may help to provide new ideas for researchers to develop ideal BG-based bone substitutes for bone reconstruction and functional recovery.

Innovative Hydrogel Design: Tailoring Immunomodulation for Optimal Chronic Wound Recovery

Despite significant progress in tissue engineering, the full regeneration of chronic wounds persists as a major challenge, with the immune response to tissue damage being a key determinant of the healing process's quality and duration. Post-injury, a crucial aspect is the transition of macrophages from a pro-inflammatory state to an anti-inflammatory. Thus, this alteration in macrophage polarization presents an enticing avenue within the realm of regenerative medicine. Recent advancements have entailed the integration of a myriad of cellular and molecular signals into hydrogel-based constructs, enabling the fine-tuning of immune cell activities during different phases. This discussion explores modern insights into immune cell roles in skin regeneration, underscoring the key role of immune modulation in amplifying the overall efficacy of wounds. Moreover, a comprehensive review is presented on the latest sophisticated technologies employed in the design of immunomodulatory hydrogels to regulate macrophage polarization. Furthermore, the deliberate design of hydrogels to deliver targeted immune stimulation through manipulation of chemistry and cell integration is also emphasized. Moreover, an overview is provided regarding the influence of hydrogel properties on immune traits and tissue regeneration process. Conclusively, the accent is on forthcoming pathways directed toward modulating immune responses in the milieu of chronic healing.

Mesenchymal Stem Cells in Cancer Therapy

The mesenchymal stem/stromal cells (MSCs) are multipotent cells that were initially discovered in the bone marrow in the late 1960s but have so far been discovered in almost all tissues of the body. The multipotent property of MSCs enables them to differentiate into various cell types and lineages, such as adipocytes, chondrocytes, and osteocytes. The immunomodulation capacity and tumor-targeting features of MSCs made their use crucial for cell-based therapies in cancer treatment, yet limited advancement could be observed in translational medicine prospects due to the need for more information regarding the controversial roles of MSCs in crosstalk tumors. In this review, we discuss the therapeutic potential of MSCs, the controversial roles played by MSCs in cancer progression, and the anticancer therapeutic strategies that are in association with MSCs. Finally, the clinical trials designed for the direct use of MSCs for cancer therapy or for their use in decreasing the side effects of other cancer therapies are also mentioned in this review to evaluate the current status of MSC-based cancer therapies.

Healing action of Interleukin-4 (IL-4) in acute and chronic inflammatory conditions: Mechanisms and therapeutic strategies

Interleukin-4 (IL-4), which is traditionally associated with inflammation, has emerged as a key player in tissue regeneration. Produced primarily by T-helper 2 (Th2) and other immune cells, IL-4 activates endogenous lymphocytes and promotes M2 macrophage polarization, both of which are crucial for tissue repair. Moreover, IL-4 stimulates the proliferation and differentiation of various cell types, contributing to efficient tissue regeneration, and shows promise for promoting tissue regeneration after injury. This review explores the multifaceted roles of IL-4 in tissue repair, summarizing its mechanisms and potential for clinical application. This review delves into the multifaceted functions of IL-4, including its immunomodulatory effects, its involvement in tissue regeneration, and its potential therapeutic applications. We discuss the mechanisms underlying IL-4-induced M2 macrophage polarization, a crucial process for tissue repair. Additionally, we explore innovative strategies for delivering IL-4, including gene therapy, protein-based therapies, and cell-based therapies. By leveraging the regenerative properties of IL-4, we can potentially develop novel therapies for various diseases, including chronic inflammatory disorders, autoimmune diseases, and organ injuries. While early research has shown promise for the application of IL-4 in regenerative medicine, further studies are needed to fully elucidate its therapeutic potential and optimize its use.

Cutaneous Immune Responses to Ablative Fractional Laser, Heat- and Cold-Based Dermatological Procedures

OBJECTIVE

Physical treatment modalities, such as ablative fractional laser (AFL), electrocautery, and cryotherapy, are extensively used in the field of dermatology. This study aimed to characterize the short-term innate and adaptive immune responses induced by AFL compared with heat- and cold-based procedures.

MATERIALS AND METHODS

Innate (CD11b+Ly6G+ neutrophils) and adaptive (CD8+CD3+ T cells) immune cell infiltration and histopathological changes were examined in murine skin on Days 1 and 7, following AFL, monopolar-electrocautery (RF), thermocautery, and cryotherapy. Interventions were standardized to reach the reticular dermis. Clinical skin reactions were photo-documented daily. As a comparator, the adaptive immune response was examined in murine basal cell carcinomas (BCC) on Day 7 after AFL exposure.

RESULTS

Baseline histopathology confirmed immediate deep dermal tissue impact by all procedures. Immune cell dynamics varied across treatments throughout the progression of clinical and histopathological responses. On Day 1, AFL and heat-based procedures triggered an innate immune response, characterized by CD11b+Ly6G+ neutrophil cell infiltration that correlated with histopathological findings and immediate onset of clinical skin reactions. In addition, heat-based procedures led to an increase in overall dermal CD45+ cells (Day 1), which continued to rise for AFL and RF-electrocautery at Day 7 posttreatment. On the contrary, cryotherapy did not induce immediate (Day 1) innate immune responses, but instead a delayed increase in neutrophil and CD45+ cell infiltration (Day 7), which coincided with the late onset of clinical reaction. CD3+ T cells and CD8+CD3+ T cells demonstrated a similar pattern, with an increase observed for heat-based procedures on Day 1 and a delayed increase for cryotherapy on Day 7. Distinctive for AFL-treated skin, the level of dermal CD3+ T cells increased over time, significant by Day 7, and AFL-treated mouse BCCs responded with increased CD8+ T cell infiltration at Day 7 posttreatment.

CONCLUSION

Heat- and cold-based procedures developed distinct cutaneous immune responses, with cryotherapy resulting in a delayed response compared to immediate immune responses from heat-based procedures. The substantial T cell response induced by AFL in the skin and BCC tumors indicates a potential for AFL as an adjuvant in immunotherapeutic treatments of keratinocyte cancers.

Exploiting the Potential of Decellularized Extracellular Matrix (ECM) in Tissue Engineering: A Review Study

While significant progress has been made in creating polymeric structures for tissue engineering, the therapeutic application of these scaffolds remains challenging owing to the intricate nature of replicating the conditions of native organs and tissues. The use of human-derived biomaterials for therapeutic purposes closely imitates the properties of natural tissue, thereby assisting in tissue regeneration. Decellularized extracellular matrix (dECM) scaffolds derived from natural tissues have become popular because of their unique biomimetic properties. These dECM scaffolds can enhance the body's ability to heal itself or be used to generate new tissues for restoration, expanding beyond traditional tissue transfers and transplants. Enhanced knowledge of how ECM scaffold materials affect the microenvironment at the injury site is expected to improve clinical outcomes. In this review, recent advancements in dECM scaffolds are explored and relevant perspectives are offered, highlighting the development and application of these scaffolds in tissue engineering for various organs, such as the skin, nerve, bone, heart, liver, lung, and kidney.

Locally Injectable, ROS-Scavenging, and ROS-/pH-Responsive Polymeric-Micelles-Embedded Hydrogels for Precise Minimally Invasive and Long-Lasting Rheumatoid Therapy

Rheumatoid arthritis (RA) is a chronic autoimmune disease characterized by synovitis, bone-erosion, and joint-destruction. Here, we developed a locally injectable, ROS-scavenging, and ROS-/pH-responsive drug-delivery platform (HC@PTM) by bio-compositing of aldolizing hyaluronic acid (HA) crosslinked with chitosan (CS), and ROS-triggered/eliminated micelles (PTM) coupled with the drug methotrexate(MTX). The PTM efficiently eradicate excessive ROS in RA-joints, precisely triggering drug-release within inflamed arthritic-sites and further confer exceptional antioxidant origins to HC@PTM. HC@PTM with outstanding shape-adaptability and self-repairing properties effectively conformed to irregular articular cartilage while resisting joint-induced deformations. Further, the platform's pH-responsive nature enables on-demand drug-release within acidic inflamed synovium, serving as a drug-reservoir for precise and sustained therapeutic effects. Extensive in vitro and in vivo investigations confirm HC@PTM's ability to induce M2 macrophage polarization, downregulate inflammatory factor expression, and ameliorate the RA-microenvironment, ultimately achieving synergistic therapeutic outcomes. This study represents significant advancements in precise and long-term RA-treatment through a minimally invasive approach, offering potential strategies for novel precision medicine.

The intensity of subacute local biological effects after the implantation of ALBO-OS dental material based on hydroxyapatite and poly(lactide-co-glycolide): in vivo evaluation in rats

OBJECTIVES

This study aimed to evaluate the intensity of the subacute local biological effects after implantation and osseoconductive potential of novel hydroxyapatite-based bone substitute coated with poly (lactide-co-glycolide), named ALBO-OS, in comparison to Bio-Oss®.

METHODS

Fifteen male Wistar rats, randomly assigned into groups: 10, 20, and 30 days (n꞊5), were subcutaneously implanted with ALBO-OS and Bio-Oss®. Furthermore, artificially made bone defects on both rat's tibias were implanted with experimental materials. Unimplanted defects represented negative control. After the animals' euthanizing, tissue samples were prepared and analyzed histologically and histomorphometrically.

RESULTS

Normal healing of the epithelial tissue was observed, with no signs of infection or necrosis. Minimal vascular congestion was noted immediately around the graft, with no signs of tissue oedema, with a minimal capsule thickness. The applied material did not cause an inflammatory response (IR) of significant intensity, and 20 days after implantation, the IR was mainly assessed as minimal. The tibial specimen showed that ALBO-OS has good osseoconductive potential, similar to Bio-Oss®, as well as low levels of acute and subacute inflammation.

CONCLUSIONS

The tested material exhibits satisfying biocompatibility, similar to Bio-Oss®.

Bioactive peptides and proteins for tissue repair: microenvironment modulation, rational delivery, and clinical potential

Bioactive peptides and proteins (BAPPs) are promising therapeutic agents for tissue repair with considerable advantages, including multifunctionality, specificity, biocompatibility, and biodegradability. However, the high complexity of tissue microenvironments and their inherent deficiencies such as short half-live and susceptibility to enzymatic degradation, adversely affect their therapeutic efficacy and clinical applications. Investigating the fundamental mechanisms by which BAPPs modulate the microenvironment and developing rational delivery strategies are essential for optimizing their administration in distinct tissue repairs and facilitating clinical translation. This review initially focuses on the mechanisms through which BAPPs influence the microenvironment for tissue repair via reactive oxygen species, blood and lymphatic vessels, immune cells, and repair cells. Then, a variety of delivery platforms, including scaffolds and hydrogels, electrospun fibers, surface coatings, assisted particles, nanotubes, two-dimensional nanomaterials, and nanoparticles engineered cells, are summarized to incorporate BAPPs for effective tissue repair, modification strategies aimed at enhancing loading efficiencies and release kinetics are also reviewed. Additionally, the delivery of BAPPs can be precisely regulated by endogenous stimuli (glucose, reactive oxygen species, enzymes, pH) or exogenous stimuli (ultrasound, heat, light, magnetic field, and electric field) to achieve on-demand release tailored for specific tissue repair needs. Furthermore, this review focuses on the clinical potential of BAPPs in facilitating tissue repair across various types, including bone, cartilage, intervertebral discs, muscle, tendons, periodontal tissues, skin, myocardium, nervous system (encompassing brain, spinal cord, and peripheral nerve), endometrium, as well as ear and ocular tissue. Finally, current challenges and prospects are discussed.

The senescence-associated secretory phenotype and its physiological and pathological implications

Cellular senescence is a state of terminal growth arrest associated with the upregulation of different cell cycle inhibitors, mainly p16 and p21, structural and metabolic alterations, chronic DNA damage responses, and a hypersecretory state known as the senescence-associated secretory phenotype (SASP). The SASP is the major mediator of the paracrine effects of senescent cells in their tissue microenvironment and of various local and systemic biological functions. In this Review, we discuss the composition, dynamics and heterogeneity of the SASP as well as the mechanisms underlying its induction and regulation. We describe the various biological properties of the SASP, its beneficial and detrimental effects in different physiological and pathological settings, and its impact on overall health span. Finally, we discuss the use of the SASP as a biomarker and of SASP inhibitors as senomorphic interventions to treat cancer and other age-related conditions.

Carboxymethylated yeast β-glucan: Biological activity screening in zebrafish, sprayable hydrogel preparation, and wound healing study in diabetic mice

Yeast β-glucan exhibits dramatic potential as wound healing regent owing to its various biological properties including immunomodulatory, anti-inflammatory, and antioxidant. But, the poor water solubility of yeast β-glucan limits its application. In this study, some carboxymethylated yeast β-glucans (CMGs) with different substitution degree was prepared. The effect of substitution degree on biological activities of carboxymethylated yeast β-glucan was investigated using zebrafish model. CMG3 with substitution degree 0.55 showed anti-inflammatory, antioxidant, and immunomodulatory activities in zebrafish. CMG3 also showed potential ability to promote angiogenesis and caudal fin regeneration. The cytotoxicity of CMG3 was investigated on L929 cells and the effect of CMG3 on cell migration was studied by scratch test. The hemolysis ratio of CMG3 was determined, and the in vitro antioxidant activity was studied. Next, CMG3 was used to prepare a sprayable hydrogel through a simple method, and the wound healing ability was studied using a streptozotocin-induced diabetic mice model. The results indicated that CMG3-based sprayable hydrogel could accelerate wound healing in a diabetic mice and influence the expression of biomarkers related to inflammatory, macrophage polarization, and angiogenesis.

The Immune-Centric Revolution Translated into Clinical Application: Peripheral Blood Mononuclear Cell (PBMNC) Therapy in Diabetic Patients with No-Option Critical Limb-Threatening Ischemia (NO-CLTI)-Rationale and Meta-Analysis of Observational Studies

Chronic limb-threatening ischemia (CLTI), the most advanced form of peripheral arterial disease (PAD), is the comorbidity primarily responsible for major lower-limb amputations, particularly for diabetic patients. Autologous cell therapy has been the focus of efforts over the past 20 years to create non-interventional therapeutic options for no-option CLTI to improve limb perfusion and wound healing. Among the different available techniques, peripheral blood mononuclear cells (PBMNC) appear to be the most promising autologous cell therapy due to physio-pathological considerations and clinical evidence, which will be discussed in this review. A meta-analysis of six clinical studies, including 256 diabetic patients treated with naive, fresh PBMNC produced via a selective filtration point-of-care device, was conducted. PBMNC was associated with a mean yearly amputation rate of 15.7%, a mean healing rate of 62%, and a time to healing of 208.6 ± 136.5 days. Moreover, an increase in TcPO2 and a reduction in pain were observed. All-cause mortality, with a mean rate of 22.2% and a yearly mortality rate of 18.8%, was reported. No serious adverse events were reported. Finally, some practical and financial considerations are provided, which point to the therapy's recommendation as the first line of treatment for this particular and crucial patient group.

Human macrophage polarisation and regulation of angiogenesis and osteogenesis is dependent on culture extracellular matrix and dimensionality

The immune system plays a crucial role in tissue repair and regeneration. Macrophages have been identified as master regulators of the early immune response and healing outcome, by orchestrating the temporal nature of the initial inflammation phase and coordinating the fate of stem/progenitor cells involved in regeneration. However, traditional in-vitro models for the study of macrophages often fail to fully replicate the complexity of the in-vivo microenvironment, therefore generating models which do not fully capture the extensive spectrum of macrophage behaviour seen in native tissues. To this end, we used a hematoma-mimetic 3D fibrin matrix characteristic of early injured tissues to generate a 3D in-vitro model mirroring the local macrophage microenvironment. Leveraging this framework, we demonstrated significant effects of extracellular matrix and dimensionality on macrophage basal signalling and polarisation, achieving more pronounced regenerative phenotypes upon stimulation with the M2a polarisation factors compared to traditional 2D tissue culture conditions. Moreover, this enhanced physiological macrophage behaviour corresponded to increased coordination of angiogenesis and osteogenesis, better mirroring the healing processes seen in-vivo. Taken together, this study demonstrates the critical importance of integrating tissue composition and 3D architecture when investigating the macrophage behaviour in-vitro, establishing a powerful tool that overcomes known limitations associated with traditional 2D culture on plastic, and can be used to identify and validate novel immunomodulation strategies to enhance tissue regeneration.

A critical review on advances and challenges of bioprinted cardiac patches

Myocardial infarction (MI), which causes irreversible myocardium necrosis, affects 0.25 billion people globally and has become one of the most significant epidemics of our time. Over the past few years, bioprinting has moved beyond a concept of simply incorporating cells into biomaterials, to strategically defining the microenvironment (e.g., architecture, biomolecular signalling, mechanical stimuli, etc.) within which the cells are printed. Among the different bioprinting applications, myocardial repair is a field that has seen some of the most significant advances towards the management of the repaired tissue microenvironment. This review critically assesses the most recent biomedical innovations being carried out in cardiac patch bioprinting, with specific considerations given to the biomaterial design parameters, growth factors/cytokines, biomechanical and bioelectrical conditioning, as well as innovative biomaterial-based "4D" bioprinting (3D scaffold structure + temporal morphology changes) of myocardial tissues, immunomodulation and sustained delivery systems used in myocardium bioprinting. Key challenges include the ability to generate large quantities of cardiac cells, achieve high-density capillary networks, establish biomaterial designs that are comparable to native cardiac extracellular matrix, and manage the sophisticated systems needed for combining cardiac tissue microenvironmental cues while simultaneously establishing bioprinting technologies yielding both high-speed and precision. This must be achieved while considering quality assurance towards enabling reproducibility and clinical translation. Moreover, this manuscript thoroughly discussed the current clinical translational hurdles and regulatory issues associated with the post-bioprinting evaluation, storage, delivery and implantation of the bioprinted myocardial patches. Overall, this paper provides insights into how the clinical feasibility and important regulatory concerns may influence the design of the bioink (biomaterials, cell sources), fabrication and post-fabrication processes associated with bioprinting of the cardiac patches. This paper emphasizes that cardiac patch bioprinting requires extensive collaborations from imaging and 3D modelling technical experts, biomaterial scientists, additive manufacturing experts and healthcare professionals. Further, the work can also guide the field of cardiac patch bioprinting moving forward, by shedding light on the potential use of robotics and automation to increase productivity, reduce financial cost, and enable standardization and true commercialization of bioprinted cardiac patches. STATEMENT OF SIGNIFICANCE: The manuscript provides a critical review of important themes currently pursued for heart patch bioprinting, including critical biomaterial design parameters, physiologically-relevant cardiac tissue stimulations, and newly emerging cardiac tissue bioprinting strategies. This review describes the limited number of studies, to date in the literature, that describe systemic approaches to combine multiple design parameters, including capabilities to yield high-density capillary networks, establish biomaterial composite designs similar to native cardiac extracellular matrix, and incorporate cardiac tissue microenvironmental cues, while simultaneously establishing bioprinting technologies that yield high-speed and precision. New tools such as artificial intelligence may provide the analytical power to consider multiple design parameters and identify an optimized work-flow(s) for enabling the clinical translation of bioprinted cardiac patches.

Constructing Electron-Rich Ru Clusters on Non-Stoichiometric Copper Hydroxide for Superior Biocatalytic ROS Scavenging to Treat Inflammatory Spinal Cord Injury

Traumatic spinal cord injury (SCI) represents a complex neuropathological challenge that significantly impacts the well-being of affected individuals. The quest for efficacious antioxidant and anti-inflammatory therapies is both a compelling necessity and a formidable challenge. Here, in this work, the innovative synthesis of electron-rich Ru clusters on non-stoichiometric copper hydroxide that contain oxygen vacancy defects (Ru/def-Cu(OH)2), which can function as a biocatalytic reactive oxygen species (ROS) scavenger for efficiently suppressing the inflammatory cascade reactions and modulating the endogenous microenvironments in SCI, is introduced. The studies reveal that the unique oxygen vacancies promote electron redistribution and amplify electron accumulation at Ru clusters, thus enhancing the catalytic activity of Ru/def-Cu(OH)2 in multielectron reactions involving oxygen-containing intermediates. These advancements endow the Ru/def-Cu(OH)2 with the capacity to mitigate ROS-mediated neuronal death and to foster a reparative microenvironment by dampening inflammatory macrophage responses, meanwhile concurrently stimulating the activity of neural stem cells, anti-inflammatory macrophages, and oligodendrocytes. Consequently, this results in a robust reparative effect on traumatic SCI. It is posited that the synthesized Ru/def-Cu(OH)2 exhibits unprecedented biocatalytic properties, offering a promising strategy to develop ROS-scavenging and anti-inflammatory materials for the management of traumatic SCI and a spectrum of other diseases associated with oxidative stress.

Incorporating Microbial Stimuli for Osteogenesis in a Rabbit Posterolateral Spinal Fusion Model

Autologous bone grafts are commonly used to repair defects in skeletal tissue, however, due to their limited supply there is a clinical need for alternatives. Synthetic ceramics present a promising option but currently lack biological activity to stimulate bone regeneration. One potential approach to address this limitation is the incorporation of immunomodulatory agents. In this study, we investigate the application of microbial stimuli to stimulate bone formation. Three different microbial stimuli were incorporated in a biphasic calcium phosphate (BCP) ceramic: Bacille Calmette-Guérin (BCG), gamma-irradiated Staphylococcus aureus (γi-S. aureus), or γi-Candida albicans (γi-C. Albicans). The constructs were then implanted in both a rabbit posterolateral spinal fusion (PLF) and an intramuscular implant model for 10 weeks and compared to a nonstimulated control construct. For the PLF model, the formation of a bony bridge was evaluated by manual palpation, micro computed tomography, and histology. While complete fusion was not observed, the BCG condition was most promising with higher manual stiffness and almost twice as much bone volume in the central fusion mass compared to the control (9 ± 4.4% bone area vs. 4.6 ± 2.3%, respectively). Conversely, the γi-S. aureus or γi-C. albicans appeared to inhibit bone formation (1.4 ± 1.4% and 1.2 ± 0.6% bone area). Bone induction was not observed in any of the intramuscular implants. This study indicates that incorporating immunomodulatory agents in ceramic bone substitutes can affect bone formation, which can be positive when selected carefully. The readily available and clinically approved BCG showed promising results, which warrants further research for clinical translation.

Validation of Active Compound of Terminalia catappa L. Extract and Its Anti-Inflammatory and Antioxidant Properties by Regulating Mitochondrial Dysfunction and Cellular Signaling Pathways

As chronic inflammation and oxidative stress cause various diseases in the human body, this study aimed to develop functional materials to prevent inflammation and oxidative stress. This study investigated the biological function and components of Terminalia catappa L. extract prepared using its leaves and branches (TCE). TCE was determined using ultraperformance liquid chromatography-quadrupole-time-of-flight mass spectrometry. Using RAW 264.7 mouse macrophages, inhibitory effects of the identified compounds on nitric oxide (NO) and reactive oxygen species (ROS) generation were analyzed. Therefore, α-punicalagin was selected as an active compound with the highest content (986.6 ± 68.4 μg/g) and physiological activity. TCE exhibited an inhibitory effect on lipopolysaccharide (LPS)-induced inflammatory markers, including NO, inducible nitric oxide synthase, and inflammatory cytokines without exerting cytotoxicity. Moreover, TCE prevented excessive ROS production mediated by LPS and upregulated hemeoxygenase-1 expression via the nuclear translocation of nuclear factor erythroid 2-related factor 2. Interestingly, TCE prevented LPS-induced mitochondrial membrane potential loss, mitochondrial ROS production, and dynamin-related protein 1 phosphorylation (serine 616), a marker of abnormal mitochondrial fission. Furthermore, TCE considerably repressed the activation of LPS-induced mitogen-activated protein kinase pathway. Thus, TCE is a promising anti-inflammatory and antioxidant pharmaceutical or nutraceutical, as demonstrated via mitochondrial dysfunction and cellular signaling pathway regulation.

Terminal differentiation precedes functional circuit integration in the peduncle neurons in regenerating Hydra vulgaris

Understanding how neural circuits are regenerated following injury is a fundamental question in neuroscience. Hydra is a powerful model for studying this process because it has a simple neural circuit structure, significant and reproducible regenerative abilities, and established methods for creating transgenics with cell-type-specific expression. While Hydra is a long-standing model for regeneration and development, little is known about how neural activity and behavior is restored following significant injury. In this study, we ask if regenerating neurons terminally differentiate prior to reforming functional neural circuits, or if neural circuits regenerate first and then guide the constituent naive cells toward their terminal fate. To address this question, we developed a dual-expression transgenic Hydra line that expresses a cell-type-specific red fluorescent protein (tdTomato) in ec5 peduncle neurons, and a calcium indicator (GCaMP7s) in all neurons. With this transgenic line, we can simultaneously record neural activity and track the reappearance of the terminally-differentiated ec5 neurons. Using SCAPE (Swept Confocally Aligned Planar Excitation) microscopy, we monitored both calcium activity and expression of tdTomato-positive neurons in 3D with single-cell resolution during regeneration of Hydra's aboral end. The synchronized neural activity associated with a regenerated neural circuit was observed approximately 4 to 8 hours after expression of tdTomato in ec5 neurons. These data suggest that regenerating ec5 neurons undergo terminal differentiation prior to re-establishing their functional role in the nervous system. The combination of dynamic imaging of neural activity and gene expression during regeneration make Hydra a powerful model system for understanding the key molecular and functional processes involved in neural regeneration following injury.

Loss of the ability to regenerate body appendages in vertebrates: from side effects of evolutionary innovations to gene loss

The ability to regenerate large body appendages is an ancestral trait of vertebrates, which varies across different animal groups. While anamniotes (fish and amphibians) commonly possess this ability, it is notably restricted in amniotes (reptiles, birds, and mammals). In this review, we explore the factors contributing to the loss of regenerative capabilities in amniotes. First, we analyse the potential negative impacts on appendage regeneration caused by four evolutionary innovations: advanced immunity, skin keratinization, whole-body endothermy, and increased body size. These innovations emerged as amniotes transitioned to terrestrial habitats and were correlated with a decline in regeneration capability. Second, we examine the role played by the loss of regeneration-related enhancers and genes initiated by these innovations in the fixation of an inability to regenerate body appendages at the genomic level. We propose that following the cessation of regenerative capacity, the loss of highly specific regeneration enhancers could represent an evolutionarily neutral event. Consequently, the loss of such enhancers might promptly follow the suppression of regeneration as a side effect of evolutionary innovations. By contrast, the loss of regeneration-related genes, due to their pleiotropic functions, would only take place if such loss was accompanied by additional evolutionary innovations that compensated for the loss of pleiotropic functions unrelated to regeneration, which would remain even after participation of these genes in regeneration was lost. Through a review of the literature, we provide evidence that, in many cases, the loss in amniotes of genes associated with body appendage regeneration in anamniotes was significantly delayed relative to the time when regenerative capability was lost. We hypothesise that this delay may be attributed to the necessity for evolutionary restructuring of developmental mechanisms to create conditions where the loss of these genes was a beneficial innovation for the organism. Experimental investigation of the downregulation of genes involved in the regeneration of body appendages in anamniotes but absent in amniotes offers a promising avenue to uncover evolutionary innovations that emerged from the loss of these genes. We propose that the vast majority of regeneration-related genes lost in amniotes (about 150 in humans) may be involved in regulating the early stages of limb and tail regeneration in anamniotes. Disruption of this stage, rather than the late stage, may not interfere with the mechanisms of limb and tail bud development during embryogenesis, as these mechanisms share similarities with those operating in the late stage of regeneration. Consequently, the most promising approach to restoring regeneration in humans may involve creating analogs of embryonic limb buds using stem cell-based tissue-engineering methods, followed by their transfer to the amputation stump. Due to the loss of many genes required specifically during the early stage of regeneration, this approach may be more effective than attempting to induce both early and late stages of regeneration directly in the stump itself.

Muscle-resident mesenchymal progenitors sense and repair peripheral nerve injury via the GDNF-BDNF axis

Fibro-adipogenic progenitors (FAPs) are muscle-resident mesenchymal progenitors that can contribute to muscle tissue homeostasis and regeneration, as well as postnatal maturation and lifelong maintenance of the neuromuscular system. Recently, traumatic injury to the peripheral nerve was shown to activate FAPs, suggesting that FAPs can respond to nerve injury. However, questions of how FAPs can sense the anatomically distant peripheral nerve injury and whether FAPs can directly contribute to nerve regeneration remained unanswered. Here, utilizing single-cell transcriptomics and mouse models, we discovered that a subset of FAPs expressing GDNF receptors Ret and Gfra1 can respond to peripheral nerve injury by sensing GDNF secreted by Schwann cells. Upon GDNF sensing, this subset becomes activated and expresses Bdnf. FAP-specific inactivation of Bdnf (Prrx1Cre; Bdnffl/fl) resulted in delayed nerve regeneration owing to defective remyelination, indicating that GDNF-sensing FAPs play an important role in the remyelination process during peripheral nerve regeneration. In aged mice, significantly reduced Bdnf expression in FAPs was observed upon nerve injury, suggesting the clinical relevance of FAP-derived BDNF in the age-related delays in nerve regeneration. Collectively, our study revealed the previously unidentified role of FAPs in peripheral nerve regeneration, and the molecular mechanism behind FAPs' response to peripheral nerve injury.

Local administration of regulatory T cells promotes tissue healing

Regulatory T cells (Tregs) are crucial immune cells for tissue repair and regeneration. However, their potential as a cell-based regenerative therapy is not yet fully understood. Here, we show that local delivery of exogenous Tregs into injured mouse bone, muscle, and skin greatly enhances tissue healing. Mechanistically, exogenous Tregs rapidly adopt an injury-specific phenotype in response to the damaged tissue microenvironment, upregulating genes involved in immunomodulation and tissue healing. We demonstrate that exogenous Tregs exert their regenerative effect by directly and indirectly modulating monocytes/macrophages (Mo/MΦ) in injured tissues, promoting their switch to an anti-inflammatory and pro-healing state via factors such as interleukin (IL)-10. Validating the key role of IL-10 in exogenous Treg-mediated repair and regeneration, the pro-healing capacity of these cells is lost when Il10 is knocked out. Additionally, exogenous Tregs reduce neutrophil and cytotoxic T cell accumulation and IFN-γ production in damaged tissues, further dampening the pro-inflammatory Mo/MΦ phenotype. Highlighting the potential of this approach, we demonstrate that allogeneic and human Tregs also promote tissue healing. Together, this study establishes exogenous Tregs as a possible universal cell-based therapy for regenerative medicine and provides key mechanistic insights that could be harnessed to develop immune cell-based therapies to enhance tissue healing.