Wound repair and regeneration: mechanisms, signaling, and translation

Wound Healing and Omega-6 Fatty Acids: From Inflammation to Repair

Wound healing is an evolutionarily conserved process that is essential for species survival. Wound healing involves a series of biochemical and cellular events that are tightly controlled, divided into 3 concomitant and overlapping phases: inflammation, proliferation, and remodelling. Poor wound healing or a chronic wound represents a silent epidemic that affects billions of people worldwide. Considering the involvement of immune cells in its resolution, recent studies are focused on investigating the roles of immune nutrients such as amino acids, minerals, and fatty acids on wound healing. Among the fatty acids, much attention has been given to omega-6 (ω-6) fatty acids since they can modulate cell migration and proliferation, phagocytic capacity, and production of inflammatory mediators. The present review summarizes current knowledge about the role of ω-6 fatty acids in the wound healing context.

In vivo migration of mesenchymal stem cells to burn injury sites and their therapeutic effects in a living mouse model

Mesenchymal stem cell (MSC)-based therapy has emerged as a promising therapeutic strategy for tissue regeneration and repair. In this study, we non-invasively monitored the tracking of MSCs toward burn injury sites using MSCs expressing firefly luciferase (Fluc) gene in living mice, and evaluated the effects of the MSCs at the injury site. Murine MSCs co-expressing Fluc and green fluorescent protein (GFP) were established using a retroviral system (referred to as MSC/Fluc). To evaluate the ability of MSC migration toward burn injury sites, cutaneous burn injury was induced in the dorsal skin of mice. MSC/Fluc was intravenously administrated into the mice model and bioluminescence imaging (BLI) was performed to monitor MSC tracking at designated time points. BLI signals of MSC/Fluc appeared in burn injury lesions at 4 days after the cell injection and then gradually decreased. Immunoblotting analysis was conducted to determine the expression of neovascularization-related genes such as TGF-β1 and VEGF in burnt skin. The levels of TGF-β1 and VEGF were higher in the MSC/Fluc-treated group than in the burn injury group. Our observations suggested that MSCs might assist burn wound healing and that MSCs expressing Fluc could be a useful tool for optimizing MSC-based therapeutic strategies for burn wound healing.

Development versus Evolution in Cancer Biology

The terms 'development' and 'evolution' are both used to describe the unfolding of the carcinogenic process. However, there is increasing awareness of an essential difference in the meanings of these two terms with reference to cancer. We discuss evidence suggesting that the concepts of development and evolution are both pertinent to the description of carcinogenesis; however, they appropriately apply to distinct phases of a multistep process. Such a distinction bears important implications for the study and management of cancer.

Alginate in Wound Dressings

Alginate is a biopolymer used in a variety of biomedical applications due to its favourable properties, such as biocompatibility and non-toxicity. It has been particularly attractive in wound healing applications to date. It can be tailored to materials with properties suitable for wound healing. Alginate has been used to prepare different forms of materials for wound dressings, such as hydrogels, films, wafers, foams, nanofibres, and in topical formulations. The wound dressings prepared from alginate are able to absorb excess wound fluid, maintain a physiologically moist environment, and minimize bacterial infections at the wound site. The therapeutic efficacy of these wound dressings is influenced by the ratio of other polymers used in combination with alginate, the nature of cross linkers used, the time of crosslinking, nature of excipients used, the incorporation of nanoparticles, and antibacterial agents. This review provides a comprehensive overview of the different forms of wound dressings containing alginate, in vitro, and in vivo results.

Nanomedicines and gene therapy for the delivery of growth factors to improve perfusion and oxygenation in wound healing

Oxygen plays a key role in wound healing, and hypoxia is a major cause of wound healing impairment; therefore, treatments to improve hemodynamics and increase wound oxygenation are of particular interest for the treatment of chronic wounds. This article describes the roles of oxygen and angiogenesis in wound healing as well as the tools used to evaluate tissue oxygenation and perfusion and then presents a review of nanomedicines and gene therapies designed to improve perfusion and oxygenation and accelerate wound healing.

Blood derivatives awaken in regenerative medicine strategies to modulate wound healing

Blood components play key roles in the modulation of the wound healing process and, together with the provisional fibrin matrix ability to selectively bind bioactive molecules and control its spatial-temporal presentation, define the complex microenvironment that characterize this biological process. As a biomimetic approach, the use of blood derivatives in regenerative strategies has awakened as a source of multiple therapeutic biomolecules. Nevertheless, and despite their clinical relevance, blood derivatives have been showing inconsistent therapeutic results due to several factors, including proper control over their delivery mechanisms. Herein, we highlight recent trends on the use biomaterials to protect, sequester and deliver these pools of biomolecules in tissue engineering and regenerative medicine approaches. Particular emphasis is given to strategies that enable to control their spatiotemporal delivery and improve the selectivity of presentation profiles of the biomolecules derived from blood derivatives rich in platelets. Finally, we discussed possible directions for biomaterials design to potentiate the aimed regenerative effects of blood derivatives and achieve efficient therapies.

Drug delivery and tissue engineering to promote wound healing in the immunocompromised host: Current challenges and future directions

As regenerative medicine matures as a field, more promising technologies are being translated from the benchtop to the clinic. However, many of these strategies are designed with otherwise healthy hosts in mind and validated in animal models without other co-morbidities. In reality, many of the patient populations benefiting from drug delivery and tissue engineering-based devices to enhance wound healing also have significant underlying immunodeficiency. Specifically, patients suffering from diabetes, malignancy, human immunodeficiency virus, post-organ transplantation, and other compromised states have significant pleotropic immune defects that affect wound healing. In this work, we review the role of different immune cells in the regenerative process, highlight the effect of several common immunocompromised states on wound healing, and discuss different drug delivery strategies for overcoming immunodeficiencies.

An aligned porous electrospun fibrous membrane with controlled drug delivery - An efficient strategy to accelerate diabetic wound healing with improved angiogenesis

A chronic wound in diabetic patients is usually characterized by poor angiogenesis and delayed wound closure. The exploration of efficient strategy to significantly improve angiogenesis in the diabetic wound bed and thereby accelerate wound healing is still a significant challenge. Herein, we reported a kind of aligned porous poly (l-lactic acid) (PlLA) electrospun fibrous membranes containing dimethyloxalylglycine (DMOG)-loaded mesoporous silica nanoparticles (DS) for diabetic wound healing. The PlLA electrospun fibers aligned in a single direction and there were ellipse-shaped nano-pores in situ generated onto the surface of fibers, while the DS were well distributed in the fibers and the DMOG as well as Si ion could be controlled released from the nanopores on the fibers. The in vitro results revealed that the aligned porous composite membranes (DS-PL) could stimulate the proliferation, migration and angiogenesis-related gene expression of human umbilical vein endothelial cells (HUVECs) compared with the pure PlLA membranes. The in vivo study further demonstrated that the prepared DS-PL membranes significantly improved neo-vascularization, re-epithelialization and collagen formation as well as inhibited inflammatory reaction in the diabetic wound bed, which eventually stimulated the healing of the diabetic wound. Collectively, these results suggest that the combination of hierarchical structures (nanopores on the aligned fibers) with the controllable released DMOG drugs as well as Si ions from the membranes, which could create a synergetic effect on the rapid stimulation of angiogenesis in the diabetic wound bed, is a potential novel therapeutic strategy for highly efficient diabetic wound healing.

STATEMENT OF SIGNIFICANCE

A chronic wound in diabetic patients is usually characterized by the poor angiogenesis and the delayed wound closure. The main innovation of this study is to design a new kind of skin tissue engineered scaffold, aligned porous poly (l-lactic acid) (PlLA) electrospun membranes containing dimethyloxalylglycine (DMOG)-loaded mesoporous silica nanoparticles (DS), which could significantly improve angiogenesis in the diabetic wound bed and thereby accelerate diabetic wound healing. The results revealed that the electrospun fibers with ellipse-shaped nano-pores on the surface were aligned in a single direction, while there were DS particles distributed in the fibers and the DMOG as well as Si ions could be controllably released from the nanopores on the fibers. The in vitro studies demonstrated that the hierarchical nanostructures (nanopores on the aligned fibers) and the controllable released chemical active agents (DMOG drugs and Si ions) from the DS-PL membranes could exert a synergistic effect on inducing the endothelial cell proliferation, migration and differentiation. Above all, the scaffolds distinctly induced the angiogenesis, collagen deposition and re-epithelialization as well as inhibited inflammation reaction in the wound sites, which eventually stimulated the healing of diabetic wounds in vivo. The significance of the current study is that the combination of the hierarchical aligned porous nanofibrous structure with DMOG-loaded MSNs incorporated in electrospun fibers may suggest a high-efficiency strategy for chronic wound healing.

miRNA delivery for skin wound healing

The wound healing has remained a worldwide challenge as one of significant public health problems. Pathological scars and chronic wounds caused by injury, aging or diabetes lead to impaired tissue repair and regeneration. Due to the unique biological wound environment, the wound healing is a highly complicated process, efficient and targeted treatments are still lacking. Hence, research-driven to discover more efficient therapeutics is a highly urgent demand. Recently, the research results have revealed that microRNA (miRNA) is a promising tool in therapeutic and diagnostic fields because miRNA is an essential regulator in cellular physiology and pathology. Therefore, new technologies for wound healing based on miRNA have been developed and miRNA delivery has become a significant research topic in the field of gene delivery.

Delivery of cellular factors to regulate bone healing

Bone tissue has a strong intrinsic regenerative capacity, thanks to a delicate and complex interplay of cellular and molecular processes, which tightly involve the immune system. Pathological settings of anatomical, biomechanical or inflammatory nature may lead to impaired bone healing. Innovative strategies to enhance bone repair, including the delivery of osteoprogenitor cells or of potent cytokines/morphogens, indicate the potential of 'orthobiologics', but are not fully satisfactory. Here, we review different approaches based on the delivery of regenerative cues produced by cells but in cell-free, possibly off-the-shelf configurations. Such strategies exploit the paracrine effect of the secretome of mesenchymal stem/stromal cells, presented in soluble form, shuttled through extracellular vesicles, or embedded within the network of extracellular matrix molecules. In addition to osteoinductive molecules, attention is given to factors targeting the resident immune cells, to reshape inflammatory and immunity processes from scarring to regenerative patterns.

Highly Diluted Acetylcholine Promotes Wound Repair in an In Vivo Model

Objective: Wound healing is a dynamic, interactive, and complex process that involves a series of events, including inflammation, migration, proliferation, granulation tissue formation, and matrix remodeling. Despite the high frequency of serious slow-healing wounds, there is still no adequate therapy. The aim of this study is to evaluate a new highly diluted acetylcholine (Ach) formulation obtained through a sequential kinetic activation (SKA) method applied to a wound healing in vivo model to verify the hypothesis that a low dose of Ach could be a more physiological stimulus for healing, by stimulating muscarinic and nicotinic receptors and their related intracellular pathways.

Approach: Two different concentrations (10 fg/mL and 1 pg/mL) and two formulations (either kinetically or nonkinetically activated) of Ach were used to verify the wound healing process. Area closure, histological aspect, and nicotinic and muscarinic receptors, matrix metalloproteinase 9 (MMP-9), Nestin, and von Willebrand's factor have been assessed by Western blot or ELISA and compared to 147 ng/mL Ach, used as positive control. Moreover, the systemic effect through plasmatic radical oxygen species (ROS) production and Ach concentration has been evaluated.

Results: Ach SKA 1 pg/mL revealed a significant capacity to restore the integrity of tissue compared to other formulation and this effect was more evident after a single administration.

Innovation: Topical application on skin of Ach SKA 1 pg/mL accelerates wound closure stimulating non-neuronal cholinergic system.

Conclusion: Our results demonstrate for the first time the importance in an in vivo model of highly diluted SKA Ach during wound healing, suggesting a potential use in skin disease.

Delivery systems of current biologicals for the treatment of chronic cutaneous wounds and severe burns

While wound therapy remains a clinical challenge in current medical practice, much effort has focused on developing biological therapeutic approaches. This paper presents a comprehensive review of delivery systems for current biologicals for the treatment of chronic wounds and severe burns. The biologicals discussed here include proteins such as growth factors and gene modifying molecules, which may be delivered to wounds free, encapsulated, or released from living systems (cells, skin grafts or skin equivalents) or biomaterials. Advances in biomaterial science and technologies have enabled the synthesis of delivery systems such as scaffolds, hydrogels and nanoparticles, designed to not only allow spatially and temporally controlled release of biologicals, but to also emulate the natural extracellular matrix microenvironment. These technologies represent an attractive field for regenerative wound therapy, by offering more personalised and effective treatments.

Involvements of γδT Lymphocytes in Acute and Chronic Skin Wound Repair

Wound healing involves three stages including inflammation, proliferation, and tissue remodeling. The underlying mechanisms remain to be further elucidated. The inflammation is characterized by spatially and temporally changing patterns of various leukocyte subsets. It is regarded as the most crucial stage since the inflammatory response is instrumental to supplying various factors and cytokines that orchestrate healing events. As a subtype of T lymphocytes, γδ T cells play an important role in skin homeostasis, tumor immunosurveillance, and wound repair. However, either the dynamics of γδ T cells in healing process or the anticipated association of γδ T cells with chronic or refractory wounds were not well understood. In this study, we determine the dynamics of γδ T cells and γδ T cell-produced effectors during acute and chronic wound repair by establishing a third-degree burn model in mice skin or human skin from diabetic patients. Our data show that the involvement of γδ T cells in acute and chronic skin wound healing. The protein levels and mRNA expressions of γδ T cell-produced effectors were increased in acute healing model, whereas those effectors were decreased in chronic repair, suggesting γδ T cells are essential for wound repair. This study probes into the significant relevance of γδ T cells with effective wound repair and provides new enlightenments for the mechanisms of the formation of chronic and/or refractory wounds.

Vitality and wound-age estimation in forensic pathology: review and future prospects

Determining the age of a wound is challenging in forensic pathology, but it can contribute to the reconstruction of crime scenes and lead to arrest of suspects. Forensic scholars have tended to focus on evaluating wound vitality and determining the time elapsed since the wound was sustained. Recent progress in forensic techniques, particularly high-throughput analyses, has enabled evaluation of materials at the cellular and molecular levels, as well as simultaneous assessment of multiple markers. This paper provides an update on wound-age estimation in forensic pathology, summarizes the recent literature, and considers useful additional information provided by each marker. Finally, the future prospects for estimating wound age in forensic practise are discussed with the hope of providing something useful for further study.

Re-thinking our understanding of immunity: Robustness in the tissue reconstruction system

Robustness, understood as the maintenance of specific functionalities of a given system against internal and external perturbations, is pervasive in today's biology. Yet precise applications of this notion to the immune system have been scarce. Here we show that the concept of robustness sheds light on tissue repair, and particularly on the crucial role the immune system plays in this process. We describe the specific mechanisms, including plasticity and redundancy, by which robustness is achieved in the tissue reconstruction system (TRS). In turn, tissue repair offers a very important test case for assessing the usefulness of the concept of robustness, and identifying different varieties of robustness.

Stem Cells and Engineered Scaffolds for Regenerative Wound Healing

The normal wound healing process involves a well-organized cascade of biological pathways and any failure in this process leads to wounds becoming chronic. Non-healing wounds are a burden on healthcare systems and set to increase with aging population and growing incidences of obesity and diabetes. Stem cell-based therapies have the potential to heal chronic wounds but have so far seen little success in the clinic. Current research has been focused on using polymeric biomaterial systems that can act as a niche for these stem cells to improve their survival and paracrine activity that would eventually promote wound healing. Furthermore, different modification strategies have been developed to improve stem cell survival and differentiation, ultimately promoting regenerative wound healing. This review focuses on advanced polymeric scaffolds that have been used to deliver stem cells and have been tested for their efficiency in preclinical animal models of wounds.

Development of Graphene Oxide Composite Aerogel with Proanthocyanidins with Hemostatic Properties As a Delivery System

The graphene aerogels' potential for use as both a hemostatic agent and dermal delivery system has scarcely been investigated. In this study, we used a sol-gel process for generating dry and stable composite aerogels based on graphene oxide (GO) and poly(vinyl alcohol) (PVA). Furthermore, we incorporated natural extract of País grape seed (SD) and skin (SK), rich in proanthocyanidins (PAs or condensed tannins). The effect of the incorporation of the grape extracts was investigated in relation to the aerogels' structure, coagulation performance and the release of the extracts. The results demonstrated that they have a porous structure and low density, capable of absorbing water and blood. The incorporation of 12% (w/w) of PA extracts into the aerogel increased the negative zeta potential of the material by 33% (-18.3 ± 1.3 mV), and the coagulation time was reduced by 37% and 28% during the first 30 and 60 s of contact between the aerogel and whole blood, respectively. The release of extracts from the GO-PVA-SD and GO-PVA-SK aerogels was prolonged to 3 h with 20%, probably due to the existence of strong binding between PAs andGO-PVA, both characterized by the presence of aromatic and hydroxyl groups that can form noncovalent bonds but are strong and stable enough to avoid a greater release into the medium. This study provides a new GO-based aerogel, which has a great potential use in the field of dermal delivery, wound healing and/or the treatment of trauma bleeding.

The effect of mesenchymal stem cells combined with platelet-rich plasma on skin wound healing

INTRODUCTION

Mesenchymal stem cells (MSCs) are multipotent stem cells that have the potential of proliferation, high self-renewal, and the potential of multilineage differentiation. The differentiation potential of the MSCs in vivo and in vitro has caused these cells to be regarded as potentially appropriate tools for wound healing. After the burn, trauma or removal of the tumor of wide wounds is developed. Although standard treatment for skin wounds is primary healing or skin grafting, they are not always practical mainly because of limited autologous skin grafting.

EVIDENCE ACQUISITIONS

Directory of Open Access Journals (DOAJ), Google Scholar, PubMed (NLM), LISTA (EBSCO), and Web of Science have been searched.

EVIDENCE SYNTHESIS

For clinical use of the MSCs in wound healing, two key issues should be taken into account: First, engineering biocompatible scaffolds clinical use of which leads to the least amount of side effects without any immunologic response and secondly, use of stem cells secretions with the least amount of clinical complications despite their high capability of healing damage.

CONCLUSION

In light of the MSCs' high capability of proliferation and multilineage differentiation as well as their significant role in modulating immunity, these cells can be used in combination with tissue engineering techniques. Moreover, the MSCs' secretions can be used in cell therapy to heal many types of wounds. The combination of MSCs and PRP aids wound healing which could potentially be used to promote wound healing.

Involvement of Tsukushi in diverse developmental processes

Tsukushi (TSK) is a small signaling molecule which takes part in different developmental processes of multiple vertebrate organisms. The diverse activity of TSK depends on its ability to bind various intermediate molecules from different major signaling pathways. Interactions of TSK with BMP, FGF, TGF-β and Wnt pathways have already been confirmed. In this review, we will introduce the latest information regarding the involvement of TSK in developmental events. We suggest a fine tuning role for TSK in multiple signaling cascades. Also, we recommend further studies on the developmental role of TSK to fully reveal its potential.

Drug delivery systems and materials for wound healing applications

Chronic, non-healing wounds place a significant burden on patients and healthcare systems, resulting in impaired mobility, limb amputation, or even death. Chronic wounds result from a disruption in the highly orchestrated cascade of events involved in wound closure. Significant advances in our understanding of the pathophysiology of chronic wounds have resulted in the development of drugs designed to target different aspects of the impaired processes. However, the hostility of the wound environment rich in degradative enzymes and its elevated pH, combined with differences in the time scales of different physiological processes involved in tissue regeneration require the use of effective drug delivery systems. In this review, we will first discuss the pathophysiology of chronic wounds and then the materials used for engineering drug delivery systems. Different passive and active drug delivery systems used in wound care will be reviewed. In addition, the architecture of the delivery platform and its ability to modulate drug delivery are discussed. Emerging technologies and the opportunities for engineering more effective wound care devices are also highlighted.

Mesenchymal stromal cells prevent bleomycin-induced lung and skin fibrosis in aged mice and restore wound healing

Fibrosis can develop in nearly any tissue leading to a wide range of chronic fibrotic diseases. However, current treatment options are limited. In this study, we utilized an established aged mouse model of bleomycin-induced lung fibrosis (BLM) to test our hypothesis that fibrosis may develop simultaneously in multiple organs by evaluating skin fibrosis and wound healing. Fibrosis was induced in lung in aged (18-22-month-old) C57BL/6 male mice by intratracheal BLM administration. Allogeneic adipose-derived mesenchymal stromal cells (ASCs) or saline were injected intravenously 24 hr after BLM administration. Full thickness 8-mm punch wounds were performed 7 days later to study potential systemic anti-fibrotic and wound healing effects of intravenously delivered ASCs. Mice developed lung and skin fibrosis as well as delayed wound closure. Moreover, we observed similar changes in the expression of known pro-fibrotic factors in both lung and skin wound tissue, including miR-199 and protein expression of its corresponding target, caveolin-1, as well as phosphorylation of protein kinase B. Importantly, ASC-treated mice exhibited attenuation of BLM-induced lung and skin fibrosis and accelerated wound healing, suggesting that ASCs may prime injured tissues and prevent end-organ fibrosis.

Teaching Wound Care to Family Caregivers

: This article is part of a series, Supporting Family Caregivers: No Longer Home Alone, published in collaboration with the AARP Public Policy Institute. Results of focus groups, conducted as part of the AARP Public Policy Institute's No Longer Home Alone video project, supported evidence that family caregivers aren't given the information they need to manage the complex care regimens of family members. This series of articles and accompanying videos aims to help nurses provide caregivers with the tools they need to manage their family member's health care at home.The articles in this new installment of the series provide simple and useful instructions that nurses should reinforce with family caregivers who perform wound care tasks. Each article also includes an informational tear sheet-Information for Family Caregivers-that contains links to instructional videos. To use this series, nurses should read the article first, so they understand how best to help family caregivers, and then encourage caregivers to watch the videos and ask questions. For additional information, see Resources for Nurses.

[Construction and bioactivity evaluation of hepatocyte growth factor-loaded poly (lactic-co-glycolic acid) nanoparticles]

OBJECTIVE

To explore the optimum conditions for preparing poly(lactic-co-glycolic) acid (PLGA) nanoparticles and evaluate the bioactivity of hepatocyte growth factor (HGF)-loaded PLGA nanoparticles.

METHODS

Bovine serum albumin (BSA)-loaded PLGA nanoparticles were prepared using a double emulsion-solvent evaporation method. The preparation process of nanoparticles was optimized by orthogonal test with the particle size, encapsulation efficiency (EE), drug loading (DD), and recovery as the indexes. HGF-loaded nanoparticles were then prepared under the optimized conditions. The EE, DD and release characteristics of BSA?loaded nanoparticles and HGF-loaded nanoparticles were evaluated using a BCA kit and HGF ELISA kit. The bioactivity of HGF-loaded nanoparticles was evaluated using CCK8 proliferation assay.

RESULTS

The HGF-loaded nanoparticles prepared under the optimized conditions had a uniform size with a mean diameter of 234.4∓4.8 nm, an EE of (77.75∓3.04)% and a recovery rate of (49.33∓9.34)%. The in vitro release curve highlighted an initial burst drug release followed by sustained release from the nanoparticles. HGF-loaded nanoparticles obviously promoted the proliferation of Hacat keratinocytes in vitro.

CONCLUSION

HGF-loaded nanoparticles prepared using double emulsion?solvent evaporation method under optimized conditions possesses a high EE with a good sustained drug release profile and a good bioactivity.

[Construction and bioactivity evaluation of hepatocyte growth factor-loaded poly (lactic-co-glycolic acid) nanoparticles]

OBJECTIVE

To explore the optimum conditions for preparing poly(lactic-co-glycolic) acid (PLGA) nanoparticles and evaluate the bioactivity of hepatocyte growth factor (HGF)-loaded PLGA nanoparticles.

METHODS

Bovine serum albumin (BSA)-loaded PLGA nanoparticles were prepared using a double emulsion-solvent evaporation method. The preparation process of nanoparticles was optimized by orthogonal test with the particle size, encapsulation efficiency (EE), drug loading (DD), and recovery as the indexes. HGF-loaded nanoparticles were then prepared under the optimized conditions. The EE, DD and release characteristics of BSA?loaded nanoparticles and HGF-loaded nanoparticles were evaluated using a BCA kit and HGF ELISA kit. The bioactivity of HGF-loaded nanoparticles was evaluated using CCK8 proliferation assay.

RESULTS

The HGF-loaded nanoparticles prepared under the optimized conditions had a uniform size with a mean diameter of 234.4∓4.8 nm, an EE of (77.75∓3.04)% and a recovery rate of (49.33∓9.34)%. The in vitro release curve highlighted an initial burst drug release followed by sustained release from the nanoparticles. HGF-loaded nanoparticles obviously promoted the proliferation of Hacat keratinocytes in vitro.

CONCLUSION

HGF-loaded nanoparticles prepared using double emulsion?solvent evaporation method under optimized conditions possesses a high EE with a good sustained drug release profile and a good bioactivity.

Delivery of Allogeneic Adipose Stem Cells in Polyethylene Glycol-Fibrin Hydrogels as an Adjunct to Meshed Autografts After Sharp Debridement of Deep Partial Thickness Burns

Harvesting of autografts results in donor site morbidities and is limited in scenarios such as large total body surface area burns. In these instances, coverage is increased by meshing grafts at the expense of delayed biologic closure. Moreover, graft meshing increases the likelihood of contraction and hypertrophic scarring, limits range of motion, and worsens cosmesis. Many tissue engineering technologies have touted the promise of adipose‐derived stem cells (ASCs) for burn wounds. The primary objective of the current study was to determine feasibility and efficacy of in situ ASC delivery via PEGylated fibrin (FPEG) hydrogels as adjuncts to meshed split thickness skin grafts in a porcine model. Deep partial thickness burns were created on the dorsum of anesthetized Yorkshire pigs, and subsequently debrided on post‐burn day 4. After debridement, wounds were treated with: split thickness skin grafts (STSG); meshed STSG (mSTSG); and mSTSG + FPEG with increasing doses of ASCs. We show that FPEG hydrogels can be delivered in situ to prevent the contraction seen after meshing of STSG. Moreover, ASCs delivered in FPEG dose‐dependently increase blood vessel size which significantly correlates with CD31 protein levels. The current study reports a dual‐action adjunct therapy to autografting administered in situ, wherein FPEG acts as both scaffolding to prevent contraction, and as a delivery vehicle for ASCs to accelerate angiogenesis. This strategy may be used to incorporate other biologics for generating tissue engineered products aimed at improving wound healing and minimizing donor sites or scarring. stemcellstranslationalmedicine2018;7:360–372

Topical delivery of l-theanine ameliorates TPA-induced acute skin inflammation via downregulating endothelial PECAM-1 and neutrophil infiltration and activation

l-theanine, the most abundant free amino acid in tea, has been documented to possess many different bioactive properties through oral or intragastrical delivery. However, little is known about the effect of topical delivery of l-theanine on acute inflammation. In the present study, by using 12-O-tetradecanoylphorbol-13-acetate (TPA, 2.5 μg/ear)-induced ear edema model in mice, we first found that single-dose local pretreatment of l-theanine 30 min before TPA time- and dose-dependently suppressed the increases in both skin thickness and weight. Subsequently l-theanine ameliorated TPA-induced erythema, vascular permeability increase, epidermal and dermal hyperplasia, neutrophil infiltration and activation via downregulating the expression of PECAM-1 (a platelet endothelial adhesion molecule-1) in blood vessels and the production of pro-inflammatory cytokines IL-1β, TNF-α, and mediator cyclooxygenase-2 (COX-2), which is mainly expressed in neutrophils. It highlighted the potential of l-theanine as a locally administrable therapeutic agent for acute cutaneous inflammation.

Keratin-chitosan/n-ZnO nanocomposite hydrogel for antimicrobial treatment of burn wound healing: Characterization and biomedical application

In the Present-day medicinally applied wound bandages have many drawbacks for, instance, rigidity, non-porosity, low mechanical potency, also an affinity for bandages to stick onto the injury exterior; additionally, a greater part of the bandages did not secure bactericidal activity. Hydrogel derived injury bandages would be supportive to afford a chill feeling with a humidity atmosphere, in addition, to performing as an obstruction to bacteria. To overcome these drawbacks, we have fabricated porous keratin-chitosan/n-ZnO nanocomposite (KCBZNs) bandages via the inclusion of nano-ZnO into the keratin-chitosan hydrogel. The functional group and surface of as-fabricated bandages were characterized using Fourier transform infrared spectroscopy (FT-IR), X-ray diffractometry (XRD), and scanning electron microscopy with energy-dispersive X-ray spectroscopy (SEM-EDX) and transmission electron microscopy with selected area diffraction (TEM-SAD). Moreover, mechanical, swelling, bactericidal, bio-compatibility of nanocomposite was assessed to exhibit its efficacy for biological applications. The nanocomposite illustrated increased swelling, and bactericidal activity. Bio-compatibility of the nanocomposite has been investigated in normal human fibroblast cells. Also, the in vivo assessments in SD rats exposed that as-fabricated nanocomposite bandages increased the wound curing with assisted for quicker skin cell construction along with collagen development. Hence, the acquired information strongly supports to utilize of this nanocomposite hydrogels for burn wounds.

Role of MicroRNA in Proliferation Phase of Wound Healing

Wound healing is a complex biological process that is generally composed of four phases: hemostasis, inflammation, proliferation, and remodeling. The proliferation phase is crucial for effective healing compared to other phases. Many critical events occur during this phase, i.e., migration of fibroblasts, re-epithelialization, angiogenesis and wound contraction. Chronic wounds are common and are considered a major public health problem. Therefore, there is the increasing need to discover new therapeutic strategies. MicroRNA (miRNA) research in the field of wound healing is in its early phase, but the knowledge of the recent discoveries is essential for developing effective therapies for the treatment of chronic wounds. In this review, we focused on recently discovered miRNAs which are involved in the proliferation phase of wound healing in the past few years and their role in wound healing.

The Biological Role of Nestin(+)-Cells in Physiological and Pathological Cardiovascular Remodeling

The intermediate filament protein nestin was identified in diverse populations of cells implicated in cardiovascular remodeling. Cardiac resident neural progenitor/stem cells constitutively express nestin and following an ischemic insult migrate to the infarct region and participate in angiogenesis and neurogenesis. A modest number of normal adult ventricular fibroblasts express nestin and the intermediate filament protein is upregulated during the progression of reparative and reactive fibrosis. Nestin depletion attenuates cell cycle re-entry suggesting that increased expression of the intermediate filament protein in ventricular fibroblasts may represent an activated phenotype accelerating the biological impact during fibrosis. Nestin immunoreactivity is absent in normal adult rodent ventricular cardiomyocytes. Following ischemic damage, the intermediate filament protein is induced in a modest population of pre-existing adult ventricular cardiomyocytes bordering the peri-infarct/infarct region and nestin⁽⁺⁾-ventricular cardiomyocytes were identified in the infarcted human heart. The appearance of nestin⁽⁺⁾-ventricular cardiomyocytes post-myocardial infarction (MI) recapitulates an embryonic phenotype and depletion of the intermediate filament protein inhibits cell cycle re-entry. Recruitment of the serine/threonine kinase p38 MAPK secondary to an overt inflammatory response after an ischemic insult may represent a seminal event limiting the appearance of nestin⁽⁺⁾-ventricular cardiomyocytes and concomitantly suppressing cell cycle re-entry. Endothelial and vascular smooth muscle cells (VSMCs) express nestin and upregulation of the intermediate filament protein may directly contribute to vascular remodeling. This review will highlight the biological role of nestin⁽⁺⁾-cells during physiological and pathological remodeling of the heart and vasculature and discuss the phenotypic advantage attributed to the intermediate filament protein.

Aerogels made of chitosan and chondroitin sulfate at high degree of neutralization: Biological properties toward wound healing

In this study, highly neutralized, highly porous, and ultralight polymeric aerogels prepared from aqueous colloidal suspensions of chitosan (CS) and chondroitin sulfate (ChS) nanocomplexes, formulated as quasi-equimolar amounts of both, are described. These aerogels were designed as healing agents under the inspiration of minimizing the amount of matter applied to wounds, reducing the electrostatic potential of the material and avoiding covalent cross-linkers in order to decrease metabolic stress over wounds. Aerogels synthesized under these criteria are biocompatible and provide specific properties for the induction of wound healing. They do not affect neither the metabolic activity of cultured 3T3 fibroblasts nor the biochemical parameters of experimental animals, open wounds close significantly faster and, unlike control wounds, complete reepithelialization and scarring can be attained 14 days after surgery. Because of its hydration abilities, rapid adaptation to the wound bed and the early accelerator effect of wound closure, the CS/ChS aerogels appear to be functional inducers of the healing. Previous information show that CS/ChS aerogels improve wound bed quality, increase granulation tissue and have pain suppressive effect. CS/ChS aerogels are useful as safe, inexpensive and easy to handle materials for topical applications, such as skin chronic wounds. © 2018 Wiley Periodicals, Inc. J Biomed Mater Res Part B: Appl Biomater, 106B: 2464-2471, 2018.

Regenerative potential of tonsil mesenchymal stem cells on surgical cutaneous defect

As tissue engineering and regenerative medicine have evolved recently, stem cell therapy has been investigated in the field of impaired wound healing. Several studies have reported that mesenchymal stem cells derived from various tissues including bone marrow and adipose tissue can exert the regenerative efficacy in the wound healing. Previously, we have demonstrated the isolation and characterization of tonsil-derived mesenchymal stem cells (TMSCs) with excellent proliferative property. In the present study, we aimed to evaluate the regenerative efficacy of TMSCs in the wound healing process. Two distinct cutaneous surgical defects were generated in the dorsum of mice. Each wound was treated with TMSCs or phosphate-buffered saline (PBS), respectively. After sacrifice, the skin and subcutaneous tissues around the surgical defect were harvested and assessed for inflammation, re-epithelialization, dermal regeneration, and granulation tissue formation. The administration of TMSCs into wound beds significantly promoted the repair of surgical defects in mice. Especially, TMSCs efficiently contributed to the attenuation of excessive inflammation in the surgical lesion, as well as the augmentation of epidermal and dermal regeneration. To elucidate the underlying mechanisms, TMSCs were analyzed for their potency in immunomodulatory ability on immune cells, stimulatory effect on the proliferation of keratinocytes, and fibroblasts, as well as the regulation of fibroblast differentiation. TMSCs inhibited the non-specific or T-cell-specific proliferation of peripheral blood mononuclear cells, as well as the M1 polarization of macrophage-like cells. Moreover, TMSCs augmented the proliferation of skin-constituting fibroblasts and keratinocytes while they suppressed the differentiation of fibroblasts into myofibroblasts. Taken together, our findings demonstrate the regenerative potential of TMSCs in wound healing process through the regulation on inflammation, proliferation, and remodeling of various skin cells, implying that TMSCs can be a promising alternative for wound repair.

A bioengineered living cell construct activates an acute wound healing response in venous leg ulcers

Chronic nonhealing venous leg ulcers (VLUs) are widespread and debilitating, with high morbidity and associated costs; about $15 billion is spent annually on the care of VLUs in the United States. Despite this, there is a paucity of treatments for VLUs because of the lack of pathophysiologic insight into ulcer development as well as the lack of knowledge regarding biologic actions of existing VLU-targeted therapies. The bioengineered bilayered living cellular construct (BLCC) skin substitute is a U.S. Food and Drug Administration-approved biologic treatment for healing VLUs. To elucidate the mechanisms through which the BLCC promotes healing of chronic VLUs, we conducted a clinical trial (NCT01327937) in which patients with nonhealing VLUs were treated with either standard of care (compression therapy) or the BLCC together with standard of care. Tissue was collected from the VLU edge before and 1 week after treatment, and the samples underwent comprehensive microarray mRNA and protein analyses. Ulcers treated with the BLCC skin substitute displayed three distinct transcriptomic patterns, suggesting that BLCC induced a shift from a nonhealing to a healing tissue response, involving modulation of inflammatory and growth factor signaling, keratinocyte activation, and attenuation of Wnt/β-catenin signaling. In these ways, BLCC application orchestrated a shift from the chronic nonhealing ulcer microenvironment to a distinctive healing milieu resembling that of an acute, healing wound. Our findings provide in vivo evidence in VLU patients of pathways that can be targeted in the design of new therapies to promote healing of chronic VLUs.

NF-κB signaling is key in the wound healing processes of silk fibroin

Silk fibroin (SF) is a well-studied biomaterial for tissue engineering applications including wound healing. However, the signaling mechanisms underlying the impact of SF on this phenomenon have not been determined. In this study, through microarray analysis, regulatory genes of NF-ĸB signaling were activated in SF-treated NIH3T3 cells along with other genes. Immunoblot analysis confirmed the activation of the NF-ĸB signaling pathway as SF induced protein expression levels of IKKα, IKKβ, p65, and the degradation of IκBα. The treatment of NIH3T3 cells with SF also increased the expression of cyclin D1, vimentin, fibronectin, and vascular endothelial growth factor (VEGF). The expression of these factors by SF treatment was abrogated when NF-ĸB was inhibited by a pharmacological inhibitor Bay 11-7082. Knockdown of NF-ĸB using siRNA of IKKα and IKKβ also inhibited the SF-induced wound healing response of the NIH3T3 cells in a wound scratch assay. Collectively, these results indicated that SF-induced wound healing through the canonical NF-κB signaling pathway via regulation of the expression of cyclin D1, vimentin, fibronectin, and VEGF by NIH3T3 cells. Using an in vivo study with a partial-thickness excision wound in rats we demonstrated that SF-induced wound healing via NF-κB regulated proteins including cyclin D1, fibronectin, and VEGF. The in vitro and in vivo data suggested that SF induced wound healing via modulation of NF-ĸB signaling regulated proteins.

STATEMENT OF SIGNIFICANCE

Silk fibroin has been effectively used as a dressing for wound treatment for more than a century. However, mechanistic insight into the basis for wound healing via silk fibroin has not been elucidated. Here we report a key mechanism involved in silk fibroin induced wound healing both in vitro and in vivo. Using genetic- and protein-level analyses, NF-κB signaling was found to regulate silk fibroin-induced wound healing by modulating target proteins. Thus, the NF-κB signaling pathway may be utilized as a therapeutic target during the formulation of silk fibroin-based biomaterials for wound healing and tissue engineering.

BH3 mimetics as anti-fibrotic therapy: Unleashing the mitochondrial pathway of apoptosis in myofibroblasts

Organs and tissues in mammals can undergo self-repair following injury. However, chronic or severe tissue injury leads to the development of dense scar tissue or fibrosis at the expense of regeneration. The identification of novel therapeutic strategies aiming at reversing fibrosis is therefore a major clinical unmet need in regenerative medicine. Persistent activation of scar-forming myofibroblasts distinguishes non-resolving pathological fibrosis from self-limited physiological wound healing. Thus, therapeutic strategies selectively inducing myofibroblast apoptosis could prevent progression and potentially reverse established fibrosis in fibrotic diseases. In this Review, we discuss recent findings that have demonstrated that activated myofibroblasts, traditionally viewed as apoptosis-resistant cells, are actually "primed for death". In this state, mitochondria of activated myofibroblasts are loaded with proapoptotic BH3 proteins, which creates a cellular "addiction" to individual antiapoptotic proteins to block prodeath signaling and ensure survival. This creates a novel therapeutic opportunity to treat organ fibrosis by inducing myofibroblast apoptosis with the so-called BH3 mimetic drugs, which have recently shown potent antifibrotic activities in experimental models. Finally, we discuss the potential use of BH3 profiling as a functional tool to diagnose myofibroblast addiction to individual antiapoptotic proteins, which may serve to guide and assign the most effective BH3 mimetic drug for patients with fibrotic disease.

Non-classical Immunity Controls Microbiota Impact on Skin Immunity and Tissue Repair

Mammalian barrier surfaces are constitutively colonized by numerous microorganisms. We explored how the microbiota was sensed by the immune system and the defining properties of such responses. Here, we show that a skin commensal can induce T cell responses in a manner that is restricted to non-classical MHC class I molecules. These responses are uncoupled from inflammation and highly distinct from pathogen-induced cells. Commensal-specific T cells express a defined gene signature that is characterized by expression of effector genes together with immunoregulatory and tissue-repair signatures. As such, non-classical MHCI-restricted commensal-specific immune responses not only promoted protection to pathogens, but also accelerated skin wound closure. Thus, the microbiota can induce a highly physiological and pleiotropic form of adaptive immunity that couples antimicrobial function with tissue repair. Our work also reveals that non-classical MHC class I molecules, an evolutionarily ancient arm of the immune system, can promote homeostatic immunity to the microbiota.

Injury-activated glial cells promote wound healing of the adult skin in mice

Cutaneous wound healing is a complex process that aims to re-establish the original structure of the skin and its functions. Among other disorders, peripheral neuropathies are known to severely impair wound healing capabilities of the skin, revealing the importance of skin innervation for proper repair. Here, we report that peripheral glia are crucially involved in this process. Using a mouse model of wound healing, combined with in vivo fate mapping, we show that injury activates peripheral glia by promoting de-differentiation, cell-cycle re-entry and dissemination of the cells into the wound bed. Moreover, injury-activated glia upregulate the expression of many secreted factors previously associated with wound healing and promote myofibroblast differentiation by paracrine modulation of TGF-β signalling. Accordingly, depletion of these cells impairs epithelial proliferation and wound closure through contraction, while their expansion promotes myofibroblast formation. Thus, injury-activated glia and/or their secretome might have therapeutic potential in human wound healing disorders.

Cell-instructive pectin hydrogels crosslinked via thiol-norbornene photo-click chemistry for skin tissue engineering

Cell-instructive hydrogels are attractive for skin repair and regeneration, serving as interactive matrices to promote cell adhesion, cell-driven remodeling and de novo deposition of extracellular matrix components. This paper describes the synthesis and photocrosslinking of cell-instructive pectin hydrogels using cell-degradable peptide crosslinkers and integrin-specific adhesive ligands. Protease-degradable hydrogels obtained by photoinitiated thiol-norbornene click chemistry are rapidly formed in the presence of dermal fibroblasts, exhibit tunable properties and are capable of modulating the behavior of embedded cells, including the cell spreading, hydrogel contraction and secretion of matrix metalloproteases. Keratinocytes seeded on top of fibroblast-loaded hydrogels are able to adhere and form a compact and dense layer of epidermis, mimicking the architecture of the native skin. Thiol-ene photocrosslinkable pectin hydrogels support the in vitro formation of full-thickness skin and are thus a highly promising platform for skin tissue engineering applications, including wound healing and in vitro testing models.

STATEMENT OF SIGNIFICANCE

Photopolymerizable hydrogels are attractive for skin applications due to their unique spatiotemporal control over the hydrogel formation. This study reports the design of a promising photo-clickable pectin hydrogel which biophysical and biochemical properties can be independently tailored to control cell behavior. A fast method for the norbornene-functionalization of pectin was developed and hydrogels fabricated through UV photoinitiated thiol-norbornene chemistry. This one-pot click reaction was performed in the presence of cells using cell-adhesive and matrix metalloproteinase-sensitive peptides, yielding hydrogels that support extensive cell spreading. Keratinocytes seeded on top of the fibroblast-loaded hydrogel formed a compact epidermis with morphological resemblance to human skin. This work presents a new protease-degradable hydrogel that supports in vitro skin formation with potential for skin tissue engineering.

Learning from regeneration research organisms: The circuitous road to scar free wound healing

The skin is the largest organ in the body and plays multiple essential roles ranging from regulating temperature, preventing infection and ultimately defining who we are physically. It is a highly dynamic organ that constantly replaces the outermost cells throughout life. However, when faced with a major injury, human skin cannot restore a significant lesion to its original functionality, instead a reparative scar is formed. In contrast to this, many other species have the unique ability to regenerate full thickness skin without formation of scar tissue. Here we review recent advances in the field that shed light on how the skin cells in regenerative species react to injury to prevent scar formation versus scar forming humans.

Helminth Modulation of Lung Inflammation

Parasitic helminths must establish chronic infections to complete their life cycle and therefore are potent modulators of multiple facets of host physiology. Parasitic helminths have coevolved with humans to become arguably master selectors of our immune system, whereby they have impacted on the selection of genes with beneficial mutations for both host and parasite. While helminth infections of humans are a significant health burden, studies have shown that helminths or helminth products can alter susceptibility to unrelated infectious or inflammatory diseases. This has generated interest in the use of helminth infections or molecules as therapeutics. In this review, we focus on the impact of helminth infections on pulmonary immunity, especially with regard to homeostatic lung function, pulmonary viral and bacterial (co)infections, and asthma.

Injectable hyperbranched poly(β-amino ester) hydrogels with on-demand degradation profiles to match wound healing processes

1A series of hyperbranched poly(β-amino ester) polymers have been synthesized via a Michael addition approach for the fabrication of hydrogels for wound healing.

Adjusting biomaterial degradation profiles to match tissue regeneration is a challenging issue. Herein, biodegradable hyperbranched poly(β-amino ester)s (HP-PBAEs) were designed and synthesized via “A2 + B4” Michael addition polymerization, and displayed fast gelation with thiolated hyaluronic acid (HA-SH) via a “click” thiol–ene reaction. HP-PBAE/HA-SH hydrogels showed tunable degradation profiles both in vitro and in vivo using diamines with different alkyl chain lengths and poly(ethylene glycol) diacrylates with varied PEG spacers. The hydrogels with optimized degradation profiles encapsulating ADSCs were used as injectable hydrogels to treat two different types of humanized excisional wounds – acute wounds with faster healing rates and diabetic wounds with slower healing and neo-tissue formation. The fast-degrading hydrogel showed accelerated wound closure in acute wounds, while the slow-degrading hydrogel showed better wound healing for diabetic wounds. The results demonstrate that the new HP-PBAE-based hydrogel in combination with ADSCs can be used as a well-controlled biodegradable skin substitute, which demonstrates a promising approach in the treatment of various types of skin wounds.