Current knowledge of immunomodulation strategies for chronic skin wound repair

Carboxymethyl cellulose/sodium alginate hydrogel with anti-inflammatory capabilities for accelerated wound healing; In vitro and in vivo study

Recently, managing the chronic skin wounds has become increasingly challenging for healthcare professionals due to the intricate orchestration of cellular and molecular processes involved that lead to the uncontrollable inflammatory reactions which hinder the healing process. Therefore, different types of wound dressings with immunomodulatory properties have been developed in recent years to effectively regulate the immune responses, enhance angiogenesis, promote re-epithelialization, and accelerate the wound healing process. This study aims to develop a new type of immunomodulatory wound dressing utilizing carboxymethyl cellulose (CMC)/sodium alginate (Alg)-simvastatin (SIM) to simultaneously enhance the inflammatory responses and the wound healing ratio. The CMC/Alg-SIM hydrogels exhibited appropriate swelling ratio, water vapor transmission rate, and desirable degradation rate, depending on the SIM content. The fabricated dressing showed sustained release of SIM (during 5 days) that improved the proliferation of skin cells. According to the in vitro findings, the CMC/Alg-SIM hydrogel exhibited controlled pro-inflammatory responses (decreased 2.5- and 1.6-times IL-6 and TNF-α, respectively) and improved secretion of anti-inflammatory cytokines (increased 1.5- and 1.3-times IL-10 and TGF-β, respectively) in comparison with CMC/Alg. Furthermore, the CMC/Alg-SIM hydrogel facilitated rapid wound healing in the rat model with a full-thickness skin defect. After 14 days post-surgery, the wound healing ratio in the CMC/Alg hydrogel group (∼93%) was significantly greater than the control group (∼58%). Therefore, the engineered CMC/Alg-SIM hydrogel with desired immunomodulatory properties possesses the potential to enhance and accelerate skin regeneration for the management of chronic wound healing.

Basic immunologic study as a foundation for engineered therapeutic development

Bioengineering and drug delivery technologies play an important role in bridging the gap between basic scientific discovery and clinical application of therapeutics. To identify the optimal treatment, the most critical stage is to diagnose the problem. Often these two may occur simultaneously or in parallel, but in this review, we focus on bottom-up approaches in understanding basic immunologic phenomena to develop targeted therapeutics. This can be observed in several fields; here, we will focus on one of the original immunotherapy targets-cancer-and one of the more recent targets-regenerative medicine. By understanding how our immune system responds in processes such as malignancies, wound healing, and medical device implantation, we can isolate therapeutic targets for pharmacologic and bioengineered interventions.

Expected role of photodynamic therapy to relieve skin damage in nuclear or radiological emergency: Review

Nuclear and radiological accidents can occur due to poor management, in transportation, radiation therapy and nuclear wards in hospitals, leading to extreme radiation exposure and serious consequences for human health. Additionally, in many of previous radiological accidents, skin damage was observed in patients and survivors due to the high radiation exposure. However, as part of a medical countermeasures in a nuclear/radiological emergency, it is critical to plan for the treatment of radiation-induced skin damage. Hence, the new, non-invasive technology of photodynamic therapy (PDT) is projected to be more effectively used for treating skin damage caused by high-dose radiation. PDT plays an important role in treating, repairing skin damage and promoting wound healing as evidenced by research. This review, highlighted and recommended potential impacts of PDT to repair and decrease radiation-induced skin tissue damage. Moreover, we have suggested some photosensitizer (PS) agent as radio-mitigator drugs to decrease radiobiological effects.

Advances in Treatments for Epidermolysis Bullosa (EB): Emphasis on Stem Cell-Based Therapy

Epidermolysis bullosa (EB) is a rare genetic dermatosis characterized by skin fragility and blister formation. With a wide phenotypic spectrum and potential extracutaneous manifestations, EB poses significant morbidity and mortality risks. Currently classified into four main subtypes based on the level of skin cleavage, EB is caused by genetic mutations affecting proteins crucial for maintaining skin integrity. The management of EB primarily focuses on preventing complications and treating symptoms through wound care, pain management, and other supportive measures. However, recent advancements in the fields of stem cell therapy, tissue engineering, and gene therapy have shown promise as potential treatments for EB. Stem cells capable of differentiating into skin cells, have demonstrated positive outcomes in preclinical and early clinical trials by promoting wound healing and reducing inflammation. Gene therapy, on the other hand, aims to correct the underlying genetic defects responsible for EB by introducing functional copies of mutated genes or modifying existing genes to restore protein function. Particularly for severe subtypes like Recessive Dystrophic Epidermolysis Bullosa (RDEB), gene therapy holds significant potential. This review aims to evaluate the role of new therapeutic approaches in the treatment of EB. The review includes findings from studies conducted on humans. While early studies and clinical trials have shown promising results, further research and trials are necessary to establish the safety and efficacy of these innovative approaches for EB treatment.

Antibacterial adhesive based on oxidized tannic acid-chitosan for rapid hemostasis

Currently, bacterial infections and bleeding interfere with wound healing, and multifunctional hydrogels with appropriate blood homeostasis, skin adhesion, and antibacterial activity are desirable. In this study, chitosan-based hydrogels were synthesized using oxidized tannic acid (OTA) and Fe3+ as cross-linkers (CS-OTA-Fe) by forming covalent, non-covalent, and metal coordination bonds between Fe3+ and OTA. Our results demonstrated that CS-OTA-Fe hydrogels showed antibacterial properties against Gram-positive bacteria (Staphylococcus aureus)and Gram-negative bacteria (Escherichia coli), low hemolysis rate (< 2 %), rapid blood clotting ability, in vitro (< 2 min), and in vivo (90 s) in mouse liver bleeding. Additionally, increasing the chitosan concentration from 3 wt% to 4.5 wt% enhanced cross-linking in the network, leading to a significant improvement in the strength (from 106 ± 8 kPa to 168 ± 12 kPa) and compressive modulus (from 50 ± 9 kPa to 102 ± 14 kPa) of hydrogels. Moreover, CS-OTA-Fe hydrogels revealed significant adhesive strength (87 ± 8 kPa) to the cow's skin tissue and cytocompatibility against L929 fibroblasts. Overall, multifunctional CS-OTA-Fe hydrogels with tunable mechanical properties, excellent tissue adhesive, self-healing ability, good cytocompatibility, and fast hemostasis and antibacterial properties could be promising candidates for biomedical applications.

Diagnostic, Therapeutic, and Theranostic Multifunctional Microneedles

Microneedles (MNs) have maintained their popularity in therapeutic and diagnostic medical applications throughout the past decade. MNs are originally designed to gently puncture the stratum corneum layer of the skin and have lately evolved into intelligent devices with functions including bodily fluid extraction, biosensing, and drug administration. MNs offer limited invasiveness, ease of application, and minimal discomfort. Initially manufactured solely from metals, MNs are now available in polymer-based varieties. MNs can be used to create systems that deliver drugs and chemicals uniformly, collect bodily fluids, and are stimulus-sensitive. Although these advancements are favorable in terms of biocompatibility and production costs, they are insufficient for the therapeutic use of MNs. This is the first comprehensive review that discusses individual MN functions toward the evolution and development of smart and multifunctional MNs for a variety of novel and impactful future applications. The study examines fabrication techniques, application purposes, and experimental details of MN constructs that perform multiple functions concurrently, including sensing, drug-molecule release, sampling, and remote communication capabilities. It is highly likely that in the near future, MN-based smart devices will be a useful and important component of standard medical practice for different applications.

Exploring the potential of bovine colostrum as a bioactive agent in human tissue regeneration: A comprehensive analysis of mechanisms of action and challenges to be overcome

The study examines bovine colostrum as a potent source of bioactive compounds, particularly growth factors, for tissue regeneration in humans. While previous research has hinted at therapeutic benefits, a comprehensive understanding of its mechanisms remains elusive, necessitating further investigation. This review analyzes nine selected scientific articles on bovine colostrum's bioactive potential in tissue regeneration. In vitro studies highlight its positive impact on cell behavior, including reduced proliferation and induced differentiation. Notably, optimal concentrations and specific colostrum components, such as extracellular vesicles and insoluble milk fat, show more favorable outcomes. In vivo studies underscore bovine colostrum as a promising natural resource for wound healing, despite some studies failing to identify associated benefits. Further research is crucial to unravel the intricate mechanisms, grasp the full potential in regenerative medicine, and develop more effective wound healing therapies. This refined understanding will pave the way for harnessing the complete regenerative potential of bovine colostrum in clinical applications.

Enhanced wound regeneration by PGS/PLA fiber dressing containing platelet-rich plasma: an in vitro study

Novel wound dressings with therapeutic effects are being continually designed to improve the wound healing process. In this study, the structural, chemical, physical, and biological properties of an electrospun poly glycerol sebacate/poly lactide acid/platelet-rich plasma (PGS/PLA-PRP) nanofibers were evaluated to determine its impacts on in vitro wound healing. Results revealed desirable cell viability in the Fibroblast (L929) and macrophage (RAW-264.7) cell lines as well as human umbilical vein endothelial cells (HUVEC). Cell migration was evident in the scratch assay (L929 cell line) so that it promoted scratch contraction to accelerate in vitro wound healing. Moreover, addition of PRP to the fiber structure led to enhanced collagen deposition (~ 2 times) in comparison with PGS/PLA scaffolds. While by addition PRP to PGS/PLA fibers not only decreased the expression levels of pro-inflammatory cytokines (IL-6 and TNF-α) in RAW-264.7 cells but also led to significantly increased levels of cytokine (IL-10) and the growth factor (TGF-β), which are related to the anti-inflammatory phase (M2 phenotype). Finally, PGS/PLA-PRP was found to induce a significant level of angiogenesis by forming branching points, loops, and tubes. Based on the results obtained, the PGS/PLA-PRP dressing developed might be a promising evolution in skin tissue engineering ensuring improved wound healing and tissue regeneration.

Coaxial electrospun PGS/PCL and PGS/PGS-PCL nanofibrous membrane containing platelet-rich plasma for skin tissue engineering

Wound healing will be enhanced using structures with therapeutic effects. This study fabricated a novel nanofibrous scaffold for skin tissue regeneration using a coaxial structure polyglycerol sebacate (PGS)/platelet-rich plasma (PRP) was embedded in the core and two different compositions were selected for the shell; in one group, polycaprolactone (PCL), and in the other group, PGS/PCL blend was used. The physical, mechanical behavior, drug delivery patterns, and cell response of scaffolds were evaluated. Results revealed that by adding PRP to the core and PGS to the shell, fiber diameters decreased to 260.8 ± 31.3 nm. It also decreased the water contact angle from 66° to 32°, that is ideal candidate for cell attachment. The drug release showed a burst release pattern in the first 30 min, followed by a continuous and slow release during the first day. Adding PGS to the shell decreased the elastic modulus, and its value reached about 500 kPa, which is near the skin elastic modulus and will lead to greater mechanical compatibility for cell proliferation. Particularly, the addition of PRP to the fiber structure enhanced the cell viability and cell adhesion with a suitable morphology. Based on the results, nanofibrous PGS-PRP/PGS-PCL dressing can enhance skin tissue regeneration.

Biomaterials for immunomodulation in wound healing

The substantial economic impact of non-healing wounds, scarring, and burns stemming from skin injuries is evident, resulting in a financial burden on both patients and the healthcare system. This review paper provides an overview of the skin's vital role in guarding against various environmental challenges as the body's largest protective organ and associated developments in biomaterials for wound healing. We first introduce the composition of skin tissue and the intricate processes of wound healing, with special attention to the crucial role of immunomodulation in both acute and chronic wounds. This highlights how the imbalance in the immune response, particularly in chronic wounds associated with underlying health conditions such as diabetes and immunosuppression, hinders normal healing stages. Then, this review distinguishes between traditional wound-healing strategies that create an optimal microenvironment and recent peptide-based biomaterials that modulate cellular processes and immune responses to facilitate wound closure. Additionally, we highlight the importance of considering the stages of wounds in the healing process. By integrating advanced materials engineering with an in-depth understanding of wound biology, this approach holds promise for reshaping the field of wound management and ultimately offering improved outcomes for patients with acute and chronic wounds.

Anti-inflammatory and anti-oxidative electrospun nanofiber membrane promotes diabetic wound healing via macrophage modulation

BACKGROUND

In the inflammatory milieu of diabetic chronic wounds, macrophages undergo substantial metabolic reprogramming and play a pivotal role in orchestrating immune responses. Itaconic acid, primarily synthesized by inflammatory macrophages as a byproduct in the tricarboxylic acid cycle, has recently gained increasing attention as an immunomodulator. This study aims to assess the immunomodulatory capacity of an itaconic acid derivative, 4-Octyl itaconate (OI), which was covalently conjugated to electrospun nanofibers and investigated through in vitro studies and a full-thickness wound model of diabetic mice.

RESULTS

OI was feasibly conjugated onto chitosan (CS), which was then grafted to electrospun polycaprolactone/gelatin (PG) nanofibers to obtain P/G-CS-OI membranes. The P/G-CS-OI membrane exhibited good mechanical strength, compliance, and biocompatibility. In addition, the sustained OI release endowed the nanofiber membrane with great antioxidative and anti-inflammatory activities as revealed in in vitro and in vivo studies. Specifically, the P/G-CS-OI membrane activated nuclear factor-erythroid-2-related factor 2 (NRF2) by alkylating Kelch-like ECH-associated protein 1 (KEAP1). This antioxidative response modulates macrophage polarization, leading to mitigated inflammatory responses, enhanced angiogenesis, and recovered re-epithelization, finally contributing to improved healing of mouse diabetic wounds.

CONCLUSIONS

The P/G-CS-OI nanofiber membrane shows good capacity in macrophage modulation and might be promising for diabetic chronic wound treatment.

Current issues and potential solutions for the electrospinning of major polysaccharides and proteins: A review

Biopolymers, especially polysaccharides and proteins, are the promising green replacement for petroleum based polymers. Due to their innate properties, they are effectively used in biomedical applications, especially tissue engineering, wound healing, and drug delivery. The fibrous morphology of biopolymers is essentially required for the effectiveness in these biomedical applications. Electrospinning (ES) is the most advanced and robust method to fabricate nanofibers (NFs) and provides a complete solution to the conventional methods issues. However, the major issues regarding fabricating polysaccharides and protein nanofibers using ES include poor electrospinnability, lack of desired fundamental properties for a specific application by a single biopolymer, and insolubility among common solvents. The current review provides the main strategies for effective electrospinning of the major biopolymers. The key strategies include blending major biopolymers with suitable biopolymers and optimizing the solvent system. A systematic literature review was done to provide the optimized solvent system of the major biopolymers along with their best possible biopolymeric blend for ES. The review also highlights the fundamental issues with the commercialization of ES based biomedical products and provides future directions to improve the fabrication of biopolymeric nanofibers.

Kappa-carrageenan based hybrid hydrogel for soft tissue engineering applications

Biological materials such as cell-derived membrane vesicles have emerged as alternative sources for molecular delivery systems, owing to multicomponent features, the inherent functionalities and signaling networks, and easy-to-carry therapeutic agents with various properties. Herein, red blood cell membrane (RBCM) vesicle-laden methacrylate kappa-carrageenan (KaMA) composite hydrogel is introduced for soft tissue engineering. Results revealed that the characteristics of hybrid hydrogels were significantly modulated by changing the RBCM vesicle content. For instance, the incorporation of 20% (v/v) RBCM significantly enhanced compressive strength from 103 ± 26 kPa to 257 ± 18 kPa and improved toughness under the cyclic loading from 1.0 ± 0.4 kJ m-3to 4.0 ± 0.5 kJ m-3after the 5thcycle. RBCM vesicles were also used for the encapsulation of curcumin (CUR) as a hydrophobic drug molecule. Results showed a controlled release of CUR over three days of immersion in PBS solution. The RBCM vesicles laden KaMA hydrogels also supportedin vitrofibroblast cell growth and proliferation. In summary, this research sheds light on KaMA/RBCM hydrogels, that could reveal fine-tuned properties and hydrophobic drug release in a controlled manner.

Review: Research progress of adipose-derived stem cells in the treatment of chronic wounds

Although methods are used to treat wounds clinically, there are still many challenges in the treatment of chronic wounds due to excessive inflammatory response, difficulties in epithelialization, vascularization, and other factors. With the increasing research on adipose-derived stem cells (ADSCs) in recent years, accumulating evidence has shown that ADSCs scan promotes the healing of chronic wounds by regulating macrophage function and cellular immunity and promoting angiogenesis and epithelialization. The present study reviewed the difficulties in the treatment of chronic wounds, as well as the advantages and the mechanism of ADSCs in promoting the healing of chronic wounds, to provide a reference for the stem cell therapy of chronic wounds.

The Nocardia Rubra Cell Wall Skeleton Regulates Macrophages and Promotes Wound Healing

The Nocardia rubra cell wall skeleton (Nr-CWS) is an immunomodulator used clinically for its ability to modulate the body's immune function. Macrophages are an important hub of the immune response during wound healing. In this study, we hypothesized that a Nr-CWS could modulate macrophage physiological activities, polarize macrophages toward M2, and promote wound healing. Through in vivo experiments, we made two full-thickness excisional wounds on the backs of mice; one was treated with a Nr-CWS, and the other was treated with saline. We photographed and recorded the wound change every other day. We observed the histopathological examination and collagen deposition using H&E and Masson staining, then analyzed the macrophage surface markers using immunofluorescence. Through in vitro experiments, we studied the effect of the Nr-CWS on RAW264.7 cells through CCK8, transwell, flow cytometry, western blot, immunofluorescence, and ELISA. We found that the Nr-CWS can enhance the proliferation, migration, and phagocytosis of macrophages. In addition, it can promote the recruitment of macrophages on the wound surface, polarize macrophages to M2, and increase the expression of pro-healing cytokines. Ultimately, the Nr-CWS accelerated wound healing.

Immunomodulating Hydrogels as Stealth Platform for Drug Delivery Applications

Non-targeted persistent immune activation or suppression by different drug delivery platforms can cause adverse and chronic physiological effects including cancer and arthritis. Therefore, non-toxic materials that do not trigger an immunogenic response during delivery are crucial for safe and effective in vivo treatment. Hydrogels are excellent candidates that can be engineered to control immune responses by modulating biomolecule release/adsorption, improving regeneration of lymphoid tissues, and enhancing function during antigen presentation. This review discusses the aspects of hydrogel-based systems used as drug delivery platforms for various diseases. A detailed investigation on different immunomodulation strategies for various delivery options and deliberate upon the outlook of such drug delivery platforms are conducted.

Deciphering the focuses and trends in skin regeneration research through bibliometric analyses

Increasing attention to skin regeneration has rapidly broadened research on the topic. However, no bibliometric analysis of the field’s research trends has yet been conducted. In response to this research gap, this study analyzed the publication patterns and progress of skin regeneration research worldwide using a bibliometric analysis of 1,471 papers comprising 1,227 (83.4%) original articles and 244 (16.6%) reviews sourced from a Web of Science search. Publication distribution was analyzed by country/region, institution, journal, and author. The frequency of keywords was assessed to prepare a bibliometric map of the development trends in skin regeneration research. China and the United States were the most productive countries in the field: China had the greatest number of publications at 433 (29.4%) and the United States had the highest H-index ranking (59 with 15,373 citations or 31.9%). Author keywords were classified into four clusters: stem cell, biomaterial, tissue engineering, and wound dressing. “Stem cells,” “chitosan,” “tissue engineering,” and “wound dressings” were the most frequent keywords in each cluster; therefore, they reflected the field’s current focus areas. “Immunomodulation,” “aloe vera,” “extracellular vesicles,” “injectable hydrogel,” and “three-dimensional (3D) bioprinting” were relatively new keywords, indicating that biomaterials for skin regeneration and 3D bioprinting are promising research hotspots in the field. Moreover, clinical studies on new dressings and techniques to accelerate skin regeneration deserve more attention. By uncovering current and future research hotspots, this analysis offers insights that may be useful for both new and experienced scholars striving to expand research and innovation in the field of skin regeneration.

Immunomodulatory strategies for bone regeneration: A review from the perspective of disease types

Tissue engineering strategies for treating bone loss to date have largely focused on targeting stem cells or vascularization. Immune cells, including macrophages and T cells, can also indirectly enhance bone healing via cytokine secretion to interact with other bone niche cells. Bone niche cues and local immune environment vary depending on anatomical location, size of defects and disease types. As such, it is critical to evaluate the role of the immune system in the context of specific bone niche and different disease types. This review focuses on immunomodulation research for bone applications using biomaterials and cell-based strategies, with a unique perspective from different disease types. We first reviewed applications for prolonging orthopaedic implant lifetime and enhancing fracture healing, two clinical challenges where immunomodulatory strategies were initially developed for orthopedic applications. We then reviewed recent research progress in harnessing immunomodulatory strategies for regenerating critical-sized, long bone or cranial bone defects, and treating osteolytic bone diseases. Remaining gaps in knowledge, future directions and opportunities were also discussed.

Skin Wound Healing: Normal Macrophage Function and Macrophage Dysfunction in Diabetic Wounds

Macrophages play a prominent role in wound healing. In the early stages, they promote inflammation and remove pathogens, wound debris, and cells that have apoptosed. Later in the repair process, they dampen inflammation and secrete factors that regulate the proliferation, differentiation, and migration of keratinocytes, fibroblasts, and endothelial cells, leading to neovascularisation and wound closure. The macrophages that coordinate this repair process are complex: they originate from different sources and have distinct phenotypes with diverse functions that act at various times in the repair process. Macrophages in individuals with diabetes are altered, displaying hyperresponsiveness to inflammatory stimulants and increased secretion of pro-inflammatory cytokines. They also have a reduced ability to phagocytose pathogens and efferocytose cells that have undergone apoptosis. This leads to a reduced capacity to remove pathogens and, as efferocytosis is a trigger for their phenotypic switch, it reduces the number of M2 reparative macrophages in the wound. This can lead to diabetic foot ulcers (DFUs) forming and contributes to their increased risk of not healing and becoming infected, and potentially, amputation. Understanding macrophage dysregulation in DFUs and how these cells might be altered, along with the associated inflammation, will ultimately allow for better therapies that might complement current treatment and increase DFU’s healing rates.