Wound-healing studies in transgenic and knockout mice

Applications of blood plasma derivatives for cutaneous wound healing: A mini-review of clinical studies

Skin injuries are a global healthcare problem. Chronic ulcers do not heal in a timely fashion, so it is essential to help the body with skin repair. There are some treatments that have been applied to chronic ulcers. One of these treatments is growth factor (GF) therapy. Platelet-rich plasma (PRP) and Platelet-poor plasma (PPP) are two types of plasma derivatives containing many GFs important for wound healing. Several works have reported their application in wound healing and tissue regeneration. The use of autologous PRP is now an adequate alternative in regenerative medicine. It was also demonstrated that PPP is a hemostatic agent for wounds. This review has studied the latest clinical studies, which have applied PRP and PPP to patients with chronic wounds.

Time-course swRNA-seq uncovers a hierarchical gene regulatory network in controlling the response-repair-remodeling after wounding

Wounding initiates intricate responses crucial for tissue repair and regeneration. Yet, the gene regulatory networks governing wound healing remain poorly understood. Here, employing single-worm RNA sequencing (swRNA-seq) across 12 time-points, we delineated a three-stage wound repair process in C. elegans: response, repair, and remodeling. Integrating diverse datasets, we constructed a dynamic regulatory network comprising 241 transcription regulators and their inferred targets. We identified potentially seven autoregulatory TFs and five cross-autoregulatory loops involving pqm-1 and jun-1. We revealed that TFs might interact with chromatin factors and form TF-TF combinatory modules via intrinsically disordered regions to enhance response robustness. We experimentally validated six regulators functioning in transcriptional and translocation-dependent manners. Notably, nhr-76, daf-16, nhr-84, and oef-1 are potentially required for efficient repair, while elt-2 may act as an inhibitor. These findings elucidate transcriptional responses and hierarchical regulatory networks during C. elegans wound repair, shedding light on mechanisms underlying tissue repair and regeneration.

Roles for epithelial integrin α3β1 in regulation of the microenvironment during normal and pathological tissue remodeling

Integrin receptors for the extracellular matrix activate intracellular signaling pathways that are critical for tissue development, homeostasis, and regeneration/repair, and their loss or dysregulation contributes to many developmental defects and tissue pathologies. This review will focus on tissue remodeling roles for integrin α3β1, a receptor for laminins found in the basement membranes (BMs) that underlie epithelial cell layers. As a paradigm, we will discuss literature that supports a role for α3β1 in promoting ability of epidermal keratinocytes to modify their tissue microenvironment during skin development, wound healing, or tumorigenesis. Preclinical and clinical studies have shown that this role depends largely on ability of α3β1 to govern the keratinocyte's repertoire of secreted proteins, or the "secretome," including 1) matrix proteins and proteases involved in matrix remodeling and 2) paracrine-acting growth factors/cytokines that stimulate other cells with important tissue remodeling functions (e.g., endothelial cells, fibroblasts, inflammatory cells). Moreover, α3β1 signaling controls gene expression that helps epithelial cells carry out these functions, including genes that encode secreted matrix proteins, proteases, growth factors, or cytokines. We will review what is known about α3β1-dependent gene regulation through both transcription and posttranscriptional mRNA stability. Regarding the latter, we will discuss examples of α3β1-dependent alternative splicing (AS) or alternative polyadenylation (APA) that prevents inclusion of cis-acting mRNA sequences that would otherwise target the transcript for degradation via nonsense-mediated decay or destabilizing AU-rich elements (AREs) in the 3'-untranslated region (3'-UTR). Finally, we will discuss prospects and anticipated challenges of exploiting α3β1 as a clinical target for the treatment of cancer or wound healing.

In Vitro, Ex Vivo, and In Vivo Approaches for Investigation of Skin Scarring: Human and Animal Models

Significance: The cutaneous repair process naturally results in different types of scarring that are classified as normal or pathological. Affected individuals are often affected from an esthetic, physical (functional), and psychosocial perspective. The distinct nature of scarring in humans, particularly the formation of pathological scars, makes the study of skin scarring a challenge for researchers in this area. Several established experimental models exist for studying scar formation. However, the increasing development and validation of newly emerging models have made it possible to carry out studies focused on different variables that influence this unique process. Recent Advances: Experimental models such as in vitro, ex vivo, and in vivo models have obtained different degrees of success in the reproduction of the scar formation in its native milieu and true environment. These models also differ in their ability to elucidate the molecular, cellular, and structural mechanisms involved in scarring, as well as for testing new agents and approaches for therapies. The models reviewed here, including cells derived from human skin and in vivo animal models, have contributed to the advancement of skin scarring research. Critical Issues and Future Directions: The absence of experimental models that faithfully reproduce the typical characteristics of the different types of human skin scars makes the improvement of validated models and the establishment of new ones a critical unmet need. The fields of wound healing research combined with tissue engineering have offered newer alternatives for experimental studies with the potential to provide clinically useful knowledge about scar formation.

Animal models for the study of acute cutaneous wound healing

The process of wound healing is critical to maintaining homeostasis after injury. Although a considerable amount has been learned about this complex process, much remains unknown. Whereas, studies with human volunteers are ideal given the unique nature of the human skin anatomy and immune system, the lack of such clinical access has made animal models prime candidates for use in preclinical studies. This review aims to discuss the strengths and limitations of the commonly used mammalian species in wound healing studies: murine, rabbit and porcine. Thereafter, a survey of models of various acute wounds such as cutaneous, ear, and implant are presented and representative studies that use them are described. This review is intended to acquaint readers with the vast spectrum of models available, each of which has a distinct utility. At the same time, it highlights the importance of utilising clinical samples to complement investigations conducted in animal models. Through this strategy, it is hoped that forthcoming research may be more reflective of the acute wound healing process as it occurs in humans.

Reoxygenation Modulates the Adverse Effects of Hypoxia on Wound Repair

Hypoxia is a major stressor and a prominent feature of pathological conditions, such as bacterial infections, inflammation, wounds, and cardiovascular defects. In this study, we investigated whether reoxygenation has a protective effect against hypoxia-induced acute injury and burn using the C57BL/6 mouse model. C57BL/6 mice were exposed to hypoxia and treated with both acute and burn injuries and were in hypoxia until wound healing. Next, C57BL/6 mice were exposed to hypoxia for three days and then transferred to normoxic conditions for reoxygenation until wound healing. Finally, skin wound tissue was collected to analyze healing-related markers, such as inflammation, vascularization, and collagen. Hypoxia significantly increased inflammatory cell infiltration and decreased vascular and collagen production, and reoxygenation notably attenuated hypoxia-induced infiltration of inflammatory cells, upregulation of pro-inflammatory cytokine levels (IL-6 and TNF-α) in the wound, and remission of inflammation in the wound. Immunofluorescence analysis showed that reoxygenation increased the expression of the angiogenic factor α-SMA and decreased ROS expression in burn tissues compared to hypoxia-treated animals. Moreover, further analysis by qPCR showed that reoxygenation could alleviate the expression of hypoxic-induced inflammatory markers (IL-6 and TNF), increase angiogenesis (SMA) and collagen synthesis (Col I), and thus promote wound healing. It is suggested that oxygen can be further evaluated in combination with oxygen-releasing materials as a supplementary therapy for patients with chronic hypoxic wounds.

3D bioprinted mesenchymal stromal cells in skin wound repair

Skin tissue regeneration and repair is a complex process involving multiple cell types, and current therapies are limited to promoting skin wound healing. Mesenchymal stromal cells (MSCs) have been proven to enhance skin tissue repair through their multidifferentiation and paracrine effects. However, there are still difficulties, such as the limited proliferative potential and the biological processes that need to be strengthened for MSCs in wound healing. Recently, three-dimensional (3D) bioprinting has been applied as a promising technology for tissue regeneration. 3D-bioprinted MSCs could maintain a better cell ability for proliferation and expression of biological factors to promote skin wound healing. It has been reported that 3D-bioprinted MSCs could enhance skin tissue repair through anti-inflammatory, cell proliferation and migration, angiogenesis, and extracellular matrix remodeling. In this review, we will discuss the progress on the effect of MSCs and 3D bioprinting on the treatment of skin tissue regeneration, as well as the perspective and limitations of current research.

What good is maths in studies of wound healing?

Wound healing is an aspect of normal physiology that we all take for granted until it goes wrong, such as, for example, the scarring that results from a severe burn, or those patients who suffer from debilitating chronic wounds that fail to heal. Ever since wound repair research began as a discipline, clinicians and basic scientists have collaborated to try and understand the cell and molecular mechanisms that underpin healthy repair in the hope that this will reveal clues for the therapeutic treatment of pathological healing. In recent decades mathematicians and physicists have begun to join in with this important challenge. Here we describe examples of how mathematical modeling married to biological experimentation has provided insights that biology alone could not fathom. To date, these studies have largely focused on wound re-epithelialization and inflammation, but we also discuss other components of wound healing that might be ripe for similar interdisciplinary approaches.

The Effect of Epidermal Growth Factor on Anastomotic Leaks: An Experimental Study in Rats

INTRODUCTION

To investigate the effects of local epidermal growth factor (EGF) use on anastomotic healing during primary repair of anastomosis in rats with anastomotic leaks (AL).

METHODS

Thirty albino Wistar rats were divided into three groups. Anastomoses were performed in group 1 after colon transection. In groups 2 and 3, ALs were created with an incomplete colon anastomosis model. Relaparotomy was conducted on rats in groups 2 and 3 72 h after the first procedure. ALs of the rats were repaired with a primary suture in group 2 and with a primary suture and the application of submucosal EGF in group 3. All rats were sacrificed through cervical dislocation on the 6th day after the first procedure. Four-centimeter colonic segments containing 2-cm distal and proximal parts of the anastomotic lines of the subjects were resected. The primary outcome was anastomotic burst pressure (ABP). The secondary outcomes included limitation in inflammation, increased neovascularization, increased fibroblast activation and increased collagen synthesis.

RESULTS

The ABP value of group 2 was significantly lower than that of group 3 (P < 0.05). No significant difference was detected in the ABP value between group 3 and group 1 (P > 0.05). There was significantly less inflammatory cell infiltration in group 3 than in group 2 (P < 0.05). Collagen synthesis and neovascularization were significantly higher in group 3 than in group 2 (P < 0.05).

CONCLUSIONS

A single-dose of submucosal EGF applied to the AL line limited inflammation and stimulated neovascularization. It also had a positive effect on the strength of the anastomosis.

Tie-Over Bolster Pressure Dressing Improves Outcomes of Skin Substitutes Xenografts on Athymic Mice

The efficacy of skin substitutes is established for the treatment of burn injuries, but its use is not limited to this condition. This technology has the potential to improve the treatment of various conditions by offering highly advanced and personalized treatments. In vivo studies are challenging but essential to move to clinical use in humans. Mice are the most widely used species in preclinical studies, but the main drawback of this model is the limited surface area of the graft in long-term transplantation studies caused by the displacement and the contraction of the graft. We improved the conventional surgical procedures by stabilizing the chamber covering the graft with intramuscular sutures and by adding a tie-over bolster dressing. The current study was therefore performed to compare outcomes of skin grafts between the conventional and optimized skin graft model. Human self-assembled skin substitutes (SASSs) were prepared and grafted to athymic mice either by the conventional method or by the new grafting method. Graft healing and complications were assessed using digital photographs on postoperative days 7, 14, and 21. Similar structure and organization were observed by histological staining. The new grafting method reduced medium and large displacement events by 1.26-fold and medium and large contraction events by 1.8-fold, leading to a 1.6-fold increase in graft surface area compared to skin substitutes grafted with the usual method. This innovation ensures better reproducibility and consistency of skin substitute transplants on mice.

Methods for the Improvement of Acne Scars Used in Dermatology and Cosmetology: A Review

Acne vulgaris is a chronic skin disease that, depending on its course, is characterized by the occurrence of various skin eruptions such as open and closed comedones, pustules, papules, and cysts. Incorrectly selected treatment or the presence of severe acne vulgaris can lead to the formation of atrophic scars. In this review, we summarize current knowledge on acne scars and methods for their improvement. There are three types of atrophic scars: icepick, rolling, and boxcar. They are of different depths and widths and have different cross-sections. Scars can combine to form clusters. If acne scars are located on the face, they can reduce the patient’s quality of life, leading to isolation and depression. There are multiple effective modalities to treat acne scars. Ablative lasers, radiofrequency, micro-needling, and pilings with trichloroacetic acid have very good treatment results. Contemporary dermatology and cosmetology use treatments that cause minimal side effects, so the patient can return to daily functioning shortly after treatment. Proper dermatological treatment and skincare, as well as the rapid implementation of cosmetological treatments, will certainly achieve satisfactory results in reducing atrophic scars.

The Topical Effect of rhGDF-5 Embedded in a Collagen–Gelatin Scaffold for Accelerated Wound Healing

The application of exogenous growth factors such as the recombinant human growth and differentiation factor 5 (rhGDF-5) represents a major research topic with great potential for the treatment of complex wounds. In a randomized, controlled minipig study, the topical effect of rhGDF-5 on full-thickness skin defects was evaluated. A total of 60 deep dermal wounds were either treated with rhGDF-5 embedded in an innovative collagen scaffold or another commonly used collagen matrix or left untreated. Wound healing was analyzed by planimetric analysis to determine wound closure over time. After 21 days, the areas of the initial wounds were excised, and the newly formed tissue was examined histologically. In comparison to untreated wounds, all examined matrices accelerated dermal wound healing. The largest acceleration of wound healing was seen with the high-dose rhGDF-5-treated wounds, which, compared to the untreated wounds, accelerated wound healing by 2.58 days, improved the neoepidermal thickness by 32.40 µm, and increased the epidermal cell density by 44.88 cells. The innovative collagen scaffold delivered rhGDF-5 adequately, served as a template to guide proliferating and restructuring cells, and accelerated wound healing. Thus, this composite product offers a novel tool for developing effective wound dressings in regenerative medicine.

Implantation of a neoantigen-targeted hydrogel vaccine prevents recurrence of pancreatic adenocarcinoma after incomplete resection

Tumor involvement of major vascular structures limits surgical options in pancreatic adenocarcinoma (PDAC), which in turn limits opportunities for cure. Despite advances in locoregional approaches, there is currently no role for incomplete resection. This study evaluated a gelatinized neoantigen-targeted vaccine applied to a grossly positive resection margin in preventing local recurrence. Incomplete surgical resection was performed in mice bearing syngeneic flank Panc02 tumors, leaving a 1 mm rim adherent to the muscle bed. A previously validated vaccine consisting of neoantigen peptides, a stimulator of interferon genes (STING) agonist and AddaVax^TM (termed PancVax) was embedded in a hyaluronic acid hydrogel and applied to the tumor bed. Tumor remnants, regional lymph nodes, and spleens were analyzed using histology, flow cytometry, gene expression profiling, and ELISPOT assays. The immune microenvironment at the tumor margin after surgery alone was characterized by a transient influx of myeloid-derived suppressor cells (MDSCs), prolonged neutrophil influx, and near complete loss of cytotoxic T cells. Application of PancVax gel was associated with enhanced T cell activation in the draining lymph node and expansion of neoantigen-specific T cells in the spleen. Mice implanted with PancVax gel demonstrated no evidence of residual tumor at two weeks postoperatively and healed incisions at two months postoperatively without local recurrence. In summary, application of PancVax gel at a grossly positive tumor margin led to systemic expansion of neoantigen-specific T cells and effectively prevented local recurrence. These findings support further work into locoregional adjuncts to immune modulation in PDAC.

Accelerative action of topical piperonylic acid on mice full thickness wound by modulating inflammation and collagen deposition

Epidermal growth factor (EGF) promotes cell growth, proliferation, and survival in numerous tissues. Piperonylic acid, a metabolite present in peppers (Piper nigrum L. and Piper longum L.), can bind to the epidermal growth factor receptor (EGFR) and induce an intracellular signaling cascade leading to the transcription of genes responsible for these actions, especially in keratinocytes. These cells are fundamental in maintaining cutaneous homeostasis and are the first to be damaged in the case of a wound. Thus, we hypothesized that piperonylic acid improves wound healing. C57BL6/J male mice were submitted to dorsal skin wounds caused by a 6 mm punch and treated topically with piperonylic acid or vehicle. The wounds were evaluated macro- and microscopically, and tissue samples were collected for immunofluorescence and real-time PCR analyses on days 6, 9 and 19 post-injury. Topical piperonylic acid improved wound healing from day 6 post-injury until closure. This phenomenon apparently occurred through EGFR activation. In addition, piperonylic acid modulated the gene expression of interleukin (Il)-6, il-1β, tumor necrosis factor (Tnf)-α, il-10, monocyte chemoattractant protein (Mcp)-1 and insulin-like growth factor (Igf)-1, which are important for the healing process. By day 19 post-injury, the new tissue showed greater deposition of type I collagen and a morphology closer to intact skin, with more dermal papillae and hair follicles. We conclude that piperonylic acid may be a viable option for the treatment of skin wounds.

Immunomodulatory Biomaterials for Tissue Repair

All implanted biomaterials are targets of the host's immune system. While the host inflammatory response was once considered a detrimental force to be blunted or avoided, in recent years, it has become a powerful force to be leveraged to augment biomaterial-tissue integration and tissue repair. In this review, we will discuss the major immune cells that mediate the inflammatory response to biomaterials, with a focus on how biomaterials can be designed to modulate immune cell behavior to promote biomaterial-tissue integration. In particular, the intentional activation of monocytes and macrophages with controlled timing, and modulation of their interactions with other cell types involved in wound healing, have emerged as key strategies to improve biomaterial efficacy. To this end, careful design of biomaterial structure and controlled release of immunomodulators can be employed to manipulate macrophage phenotype for the maximization of the wound healing response with enhanced tissue integration and repair, as opposed to a typical foreign body response characterized by fibrous encapsulation and implant isolation. We discuss current challenges in the clinical translation of immunomodulatory biomaterials, such as limitations in the use of in vitro studies and animal models to model the human immune response. Finally, we describe future directions and opportunities for understanding and controlling the biomaterial-immune system interface, including the application of new imaging tools, new animal models, the discovery of new cellular targets, and novel techniques for in situ immune cell reprogramming.

Fermitin family homolog 2 (Kindlin-2) affects vascularization during the wound healing process by regulating the Wnt/β-catenin signaling pathway in vascular endothelial cells

Kindlin-2 is a member of the FERM-containing cytoskeletal protein family that regulates cell–matrix interactions. Previous studies have shown that Kindlin-2 recruits focal adhesion proteins and regulates integration by binding to the focal adhesion region of the integrin β-segment. Although Kindlin-2 has been reported to be involved in various skin diseases and many kinds of tumors, its role in the skin wound healing process remains unclear. The aim of the present study was to investigate the role of Kindlin-2 in the regulation of wound healing. The effects of Kindlin-2 on wound healing were studied by a wound healing model, kindlin-2 (±) mice. The effects of Kindlin-2 on cell migration, cellular tube formation, and cell adhesion and spreading were evaluated in human umbilical vein endothelial cells (HUVECs) with downregulated Kindlin-2 expression. We found that the expression of kindlin-2 was elevated in wound healing tissues and that interfering with the expression of Kindlin-2 delayed the wound healing process and reduced neovascularization. We found that the wound healing of kindlin-2 (±) mice was delayed, with a decreased number of new blood vessels. Furthermore, depletion of Kindlin-2 impaired HUVEC spreading, migration and tube formation. Intriguingly, we found that kindlin-2 binds to β-catenin in the Wnt/β-catenin signaling pathway and cooperates with β-catenin to enter the nucleus from the cytoplasm, activating the downstream Wnt/β-catenin signaling pathway. Taken together, these results help to elucidate the mechanism of Kindlin-2 in the regulation of the wound healing process and provide a theoretical basis for further study of wound healing and abnormal healing.

Wound Healing Driver Gene and Therapeutic Development: Political and Scientific Hurdles

Significance: Since the last Food and Drug Administration (FDA) approval of a wound healing therapeutic in 1997, no new therapeutic candidate (excluding physical therapies, devices, dressings, and antimicrobial agents) has advanced to clinical applications. During this period, the FDA drug approvals for tumors, which have been referred to as "wounds that do not heal," have reached a total of 284 (by end of 2018). Both political and scientific factors may explain this large discrepancy in drug approvals for the two seemingly related and equally complex pathophysiological conditions. Recent Advances: Using the current research funding ratio of 1:150 for wound healing to cancer and the 5% FDA drug approval rate for oncology, we reach a crude estimate of a 0.03% success rate for wound healing therapeutics. Unless a drastic improvement of the current situation, we express a pessimistic outlook toward new and effective wound healing drugs. Critical Issues: We argue that successful development of wound healing therapeutics will rely on identification of wound healing driver genes (WDGs), and the focus should be on WDGs for the wound closure phase of wound healing. Therefore, WDGs must be both necessary and sufficient for wound closure; the absence of a WDG disrupts wound closure, while its supplementation alone is sufficient to restore full wound closure. Successful translation of a WDG into therapeutics requires availability of well-defined animal models with a high degree of relevance to humans. This review discusses the main hurdles faced by the wound healing research community behind the development of so-called "rescuing drugs" for wound healing. Future Directions: Given the lack of new wound healing drugs for the past 23 years, there is a need for a wide range of fresh, innovative, and thorough debates on wound healing drug development, including an organized movement to raise public support for wound healing research.

The Role of MSC in Wound Healing, Scarring and Regeneration

Tissue repair and regeneration after damage is not completely understood, and current therapies to support this process are limited. The wound healing process is associated with cell migration and proliferation, extracellular matrix remodeling, angiogenesis and re-epithelialization. In normal conditions, a wound will lead to healing, resulting in reparation of the tissue. Several risk factors, chronic inflammation, and some diseases lead to a deficient wound closure, producing a scar that can finish with a pathological fibrosis. Mesenchymal stem/stromal cells (MSCs) are widely used for their regenerative capacity and their possible therapeutically potential. Derived products of MSCs, such as exosomes or extravesicles, have shown a therapeutic potential similar to MSCs, and these cell-free products may be interesting in clinics. MSCs or their derivative products have shown paracrine beneficial effects, regulating inflammation, modifying the fibroblast activation and production of collagen and promoting neovascularization and re-epithelialization. This review describes the effects of MSCs and their derived products in each step of the wound repair process. As well, it reviews the pre-clinical and clinical use of MSCs to benefit in skin wound healing in diabetic associated wounds and in pathophysiological fibrosis.

Cerium-Containing N-Acetyl-6-Aminohexanoic Acid Formulation Accelerates Wound Reparation in Diabetic Animals

Background: The main goal of our study was to explore the wound-healing property of a novel cerium-containing N-acethyl-6-aminohexanoate acid compound and determine key molecular targets of the compound mode of action in diabetic animals. Methods: Cerium N-acetyl-6-aminohexanoate (laboratory name LHT-8-17) as a 10 mg/mL aquatic spray was used as wound experimental topical therapy. LHT-8-17 toxicity was assessed in human skin epidermal cell culture using (4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide (MTT) assay. A linear wound was reproduced in 18 outbred white rats with streptozotocin-induced (60 mg/kg i.p.) diabetes; planar cutaneous defect was modelled in 60 C57Bl₆ mice with streptozotocin-induced (200 mg/kg i.p.) diabetes and 90 diabetic db/db mice. Firmness of the forming scar was assessed mechanically. Skin defect covering was histologically evaluated on days 5, 10, 15, and 20. Tissue TNF-α, IL-1β and IL-10 levels were determined by quantitative ELISA. Oxidative stress activity was detected by Fe-induced chemiluminescence. Ki-67 expression and CD34 cell positivity were assessed using immunohistochemistry. FGFR3 gene expression was detected by real-time PCR. LHT-8-17 anti-microbial potency was assessed in wound tissues contaminated by MRSA. Results: LHT-8-17 4 mg twice daily accelerated linear and planar wound healing in animals with type 1 and type 2 diabetes. The formulated topical application depressed tissue TNF-α, IL-1β, and oxidative reaction activity along with sustaining both the IL-10 concentration and antioxidant capacity. LHT-8-17 induced Ki-67 positivity of fibroblasts and pro-keratinocytes, upregulated FGFR3 gene expression, and increased tissue vascularization. The formulation possessed anti-microbial properties. Conclusions: The obtained results allow us to consider the formulation as a promising pharmacological agent for diabetic wound topical treatment.

Investigation of Skin Wound Healing Using a Mouse Model

Wound repair is a fundamental physiological process to keep the integrity of the skin, and its dysregulation results in diseases, such as chronic nonhealing wounds or excessive scarring. To study the underlying cellular and molecular mechanisms and identify new therapeutic targets, animal models are often used in the wound healing research. In this chapter, we describe an easy step-by-step protocol to generate skin wounds in a mouse model. Briefly, two full-thickness wounds extending through the panniculus carnosus are made on the dorsum on each side of the midline of a mouse, which is followed by monitoring and quantifying the wound closure. Moreover, the biopsy tissues of skin and wound-edges are collected at different time points for subsequent histology and gene expression analysis.

A Novel Bespoke Hypertrophic Scar Treatment: Actualizing Hybrid Pressure and Silicone Therapies with 3D Printing and Scanning

The treatment of hypertrophic scars (HSs) is considered to be the most challenging task in wound rehabilitation. Conventional silicone sheet therapy has a positive effect on the healing process of HSs. However, the dimensions of the silicone sheet are typically larger than those of the HS itself which may negatively impact the healthy skin that surrounds the HS. Furthermore, the debonding and displacement of the silicone sheet from the skin are critical problems that affect treatment compliance. Herein, we propose a bespoke HS treatment design that integrates pressure sleeve with a silicone sheet and use of silicone gel using a workflow of three-dimensional (3D) printing, 3D scanning and computer-aided design, and manufacturing software. A finite element analysis (FEA) is used to optimize the control of the pressure distribution and investigate the effects of the silicone elastomer. The result shows that the silicone elastomer increases the amount of exerted pressure on the HS and minimizes unnecessary pressure to other parts of the wrist. Based on this treatment design, a silicone elastomer that perfectly conforms to an HS is printed and attached onto a customized pressure sleeve. Most importantly, unlimited scar treating gel can be applied as the means to optimize treatment of HSs while the silicone sheet is firmly affixed and secured by the pressure sleeve.

A Review on Chitosan's Uses as Biomaterial: Tissue Engineering, Drug Delivery Systems and Cancer Treatment

Chitosan, derived from chitin, is a biopolymer consisting of arbitrarily distributed β-(1-4)-linked D-glucosamine and N-acetyl-D-glucosamine that exhibits outstanding properties— biocompatibility, biodegradability, non-toxicity, antibacterial activity, the capacity to form films, and chelating of metal ions. Most of these peculiar properties are attributed to the presence of free protonable amino groups along the chitosan backbone, which also gives it solubility in acidic conditions. Moreover, this biopolymer can also be physically modified, thereby presenting a variety of forms to be developed. Consequently, this polysaccharide is used in various fields, such as tissue engineering, drug delivery systems, and cancer treatment. In this sense, this review aims to gather the state-of-the-art concerning this polysaccharide when used as a biomaterial, providing information about its characteristics, chemical modifications, and applications. We present the most relevant and new information about this polysaccharide-based biomaterial’s applications in distinct fields and also the ability of chitosan and its various derivatives to selectively permeate through the cancer cell membranes and exhibit anticancer activity, and the possibility of adding several therapeutic metal ions as a strategy to improve the therapeutic potential of this polymer.

Biotech-Educated Platelets: Beyond Tissue Regeneration 2.0

The increasing discoveries regarding the biology and functions of platelets in the last decade undoubtedly show that these cells are one of the most biotechnological human cells. This review summarizes new advances in platelet biology, functions, and new concepts of biotech-educated platelets that connect advanced biomimetic science to platelet-based additive manufacturing for tissue regeneration. As highly responsive and secretory cells, platelets could be explored to develop solutions that alter injured microenvironments through platelet-based synthetic biomaterials with instructive extracellular cues for morphogenesis in tissue engineering beyond tissue regeneration 2.0.

Understanding the Role of the Clitellum in the Regeneration Events of the Earthworm Eudrilus eugeniae

Regeneration is a complex mechanism to restore lost or damaged body parts. In earthworms, regeneration capability varies among different species, and it is important to explore the mechanism behind the regeneration process. Interestingly, regeneration in earthworms is either dependent or independent of clitellum segments. In the present study, juvenile earthworms (Eudrilus eugeniae) were amputated at 3 different sites, namely the head, clitellum, and tail segments (at segments 10, 15, and 30, respectively), and their regeneration ability was documented using a foldscope. The amputated segments having the intact clitellum were able to heal the wounds and form the regenerative blastema. The smaller portions of the amputated segments (segments 1-10 and 1-15) without intact clitellum were unable to heal the wound, and death occurs within 12-24 h. The larger portions of the amputated segments (segments 15 and 30 to anus) without intact clitellum were able to heal the wound but lacked the regeneration capability. In control worms, alkaline phosphatase (ALP) signals were observed at the anterior tip, clitellum, and gut epithelium tissues, whereas, upon amputation, the enriched signals from the clitellum diminished, but profound signals were observed at the amputation site and regenerative blastema. Interestingly, on days 3 and 4, blastemal tips lacked ALP signals due to initiation of the differentiation process in the regeneration blastema. In summary, using a foldscope microscope, the role of the clitellum in the regeneration mechanism was indicated by ALP activity.

Regeneration-Competent and -Incompetent Murids Differ in Neutrophil Quantity and Function

Regeneration is rare in mammals, but spiny mice (Acomys spp.) naturally regenerate skin and ear holes. Inflammation is thought to inhibit regeneration during wound healing, but aspects of inflammation contribute to both regeneration and pathogen defense. We compared neutrophil traits among uninjured, regeneration-competent (Acomys: A. cahirinus, A. kempi, A. percivali) and -incompetent (Mus musculus: Swiss Webster, wild-caught strains) murids to test for constitutive differences in neutrophil quantity and function between these groups. Neutrophil quantity differed significantly among species. In blood, Acomys had lower percentages of circulating neutrophils than Mus; and in bone marrow, Acomys had higher percentages of band neutrophils and lower percentages of segmented neutrophils. Functionally, Acomys and Mus neutrophils did not differ in their ability to migrate or produce reactive oxygen species, but Acomys neutrophils phagocytosed more fungal zymosan. Despite this enhanced phagocytosis activity, Acomys neutrophils were not more effective than Mus neutrophils at killing Escherichia coli. Interestingly, whole blood bacteria killing was dominated by serum in Acomys versus neutrophils only or neutrophils and serum in Mus, suggesting that Acomys primarily rely on serum to kill bacteria whereas Mus do not. These subtle differences in neutrophil traits may allow regeneration-competent species to offset damaging effects of inflammation without compromising pathogen defense.

A wheat germ-derived peptide YDWPGGRN facilitates skin wound-healing processes

Wheat germ derivatives have been shown to inhibit inflammation-related diseases. In this study, a small peptide (YDWPGGRN) isolated from wheat germ was used to study its anti-inflammatory activity and its application in skin wound healing. Both the in vitro and in vivo results clearly showed that YDWPGGRN significantly inhibited the LPS-stimulated NO, IL-1β, IL-6 and TNF-α production but promoted the release of an anti-inflammatory cytokine, IL-10. In addition, YDWPGGRN directly enhanced the proliferation and migration of HaCaT cells and L929 cells. Furthermore, the results demonstrated that YDWPGGRN was able to stimulate angiogenesis and collagen production in wound areas, consequently accelerating the skin wound-healing processes in a rat model with a full thickness dermal wound. The current findings suggest that YDWPGGRN promotes wound healing by anti-inflammatory reactions and enhances the proliferation and migration of keratinocytes and fibroblasts; therefore, it may be applicable for skin wound therapeutics.

Role of TGF-β in Skin Chronic Wounds: A Keratinocyte Perspective

Chronic wounds are characterized for their incapacity to heal within an expected time frame. Potential mechanisms driving this impairment are poorly understood and current hypotheses point to the development of an unbalanced milieu of growth factor and cytokines. Among them, TGF-β is considered to promote the broadest spectrum of effects. Although it is known to contribute to healthy skin homeostasis, the highly context-dependent nature of TGF-β signaling restricts the understanding of its roles in healing and wound chronification. Historically, low TGF-β levels have been suggested as a pattern in chronic wounds. However, a revision of the available evidence in humans indicates that this could constitute a questionable argument. Thus, in chronic wounds, divergences regarding skin tissue compartments seem to be characterized by elevated TGF-β levels only in the epidermis. Understanding how this aspect affects keratinocyte activities and their capacity to re-epithelialize might offer an opportunity to gain comprehensive knowledge of the involvement of TGF-β in chronic wounds. In this review, we compile existing evidence on the roles played by TGF-β during skin wound healing, with special emphasis on keratinocyte responses. Current limitations and future perspectives of TGF-β research in chronic wounds are discussed.

The Henna pigment Lawsone activates the Aryl Hydrocarbon Receptor and impacts skin homeostasis

As a first host barrier, the skin is constantly exposed to environmental insults that perturb its integrity. Tight regulation of skin homeostasis is largely controlled by the aryl hydrocarbon receptor (AhR). Here, we demonstrate that Henna and its major pigment, the naphthoquinone Lawsone activate AhR, both in vitro and in vivo. In human keratinocytes and epidermis equivalents, Lawsone exposure enhances the production of late epidermal proteins, impacts keratinocyte differentiation and proliferation, and regulates skin inflammation. To determine the potential use of Lawsone for therapeutic application, we harnessed human, murine and zebrafish models. In skin regeneration models, Lawsone interferes with physiological tissue regeneration and inhibits wound healing. Conversely, in a human acute dermatitis model, topical application of a Lawsone-containing cream ameliorates skin irritation. Altogether, our study reveals how a widely used natural plant pigment is sensed by the host receptor AhR, and how the physiopathological context determines beneficial and detrimental outcomes.

Mast cells play role in wound healing through the ZnT2/GPR39/IL-6 axis

Zinc (Zn) is an essential nutrient and its deficiency causes immunodeficiency and skin disorders. Various cells including mast cells release Zn-containing granules when activated; however, the biological role of the released Zn is currently unclear. Here we report our findings that Zn transporter ZnT2 is required for the release of Zn from mast cells. In addition, we found that Zn and mast cells induce IL-6 production from inflammatory cells such as skin fibroblasts and promote wound healing, a process that involves inflammation. Zn induces the production of a variety of pro-inflammatory cytokines including IL-6 through signaling pathways mediated by the Zn receptor GPR39. Consistent with these findings, wound healing was impaired in mice lacking IL-6 or GPR39. Thus, our results show that Zn and mast cells play a critical role in wound healing through activation of the GPR39/IL-6 signaling axis.

After Conventional Wisdom Has Failed, What Drives Wound Healing?

Between 2006 and 2015, the U.S. Food and Drug Administration’s (FDA) overall likelihood of approval (LOA) from Phase I clinical trials for all therapeutic candidates was 9.6%, with the highest LOA in haematology (26.1%) and the lowest in oncology (5.1%). Two critical features attributed to the success of advancing trials were i) targeting driver genes responsible for disease, and ii) use of human disease-relevant animal models during preclinical studies. For decades, conventional wisdom has been that growth factors are the drivers of wound healing, but few have either advanced to clinical applications or proven effective. The purpose of this paper is to explore heat shock protein 90-alpha (Hsp90α)’s role as a potential driver of wound healing and as a possible future therapeutic entity through a review of recent literature, including studies with human disease-relevant animal models. Of the approximately 7,000 gene products generated by a given mammalian cell type, the Hsp90 family of proteins (Hsp90α and Hsp90β) accounts for 2–3% of them. Hsp90β fulfils the role of an intracellular chaperone, but Hsp90α’s intracellular function is surprisingly dispensable. Instead, the abundancy of Hsp90α appears to have been prepared for extracellular purposes. When secreted via exosomes by cells under environmental stress, such as injury, Hsp90α protects cells from hypoxia-induced cell death, reduces local inflammation, and subsequently promotes cell migration to repair the injured tissue. Unlike conventional growth factors, secreted Hsp90α stimulates all major cell types involved in wound healing equally, resists microenvironmental inhibitors like TGFβ and hyperglycaemia, and is highly stable. Inhibition of exosome-mediated Hsp90α secretion, neutralisation of Hsp90α’s ATPase-independent extracellular functions, or interruption of Hsp90α-LRP-1 signalling blocks wound closure in vivo. Topical application of Hsp90α’s therapeutic entity, F-5 (a 115-amino acid peptide), has shown great promise for healing acute burn and diabetic wounds in mice and pigs.

The origins and non-canonical functions of macrophages in development and regeneration

The discovery of new non-canonical (i.e. non-innate immune) functions of macrophages has been a recurring theme over the past 20 years. Indeed, it has emerged that macrophages can influence the development, homeostasis, maintenance and regeneration of many tissues and organs, including skeletal muscle, cardiac muscle, the brain and the liver, in part by acting directly on tissue-resident stem cells. In addition, macrophages play crucial roles in diseases such as obesity-associated diabetes or cancers. Increased knowledge of their regulatory roles within each tissue will therefore help us to better understand the full extent of their functions and could highlight new mechanisms modulating disease pathogenesis. In this Review, we discuss recent studies that have elucidated the developmental origins of various macrophage populations and summarize our knowledge of the non-canonical functions of macrophages in development, regeneration and tissue repair.

The Interplay Between Lymphatic Vessels and Chemokines

Chemokines are a family of small protein cytokines that act as chemoattractants to migrating cells, in particular those of the immune system. They are categorized functionally as either homeostatic, constitutively produced by tissues for basal levels of cell migration, or inflammatory, where they are generated in association with a pathological inflammatory response. While the extravasation of leukocytes via blood vessels is a key step in cells entering the tissues, the lymphatic vessels also serve as a conduit for cells that are recruited and localized through chemoattractant gradients. Furthermore, the growth and remodeling of lymphatic vessels in pathologies is influenced by chemokines and their receptors expressed by lymphatic endothelial cells (LECs) in and around the pathological tissue. In this review we summarize the diverse role played by specific chemokines and their receptors in shaping the interaction of lymphatic vessels, immune cells, and other pathological cell types in physiology and disease.

Collagen-based sponge hastens wound healing via decrease of inflammatory cytokines

The objective of this study was to compare and evaluate the efficacy of collagen-based sponge compared to commercial collagen sponge as a potent open wound-dressing material. In this study, 10 mm diameter skin incision was made on lateral side of rats. The wound was monitored regularly until day 12. Histopathology results revealed the faster re-epithelialization and lesser inflammatory cells, and also masson's trichrome staining showed that collagen fibrils were horizontal and interwoven in collagen-based sponge group. The expression of growth factors such as VEGF and TGF-β1 was found to be upregulated in transcriptional and translational levels, suggesting the importance of collagen-based sponge as a potent wound-healing material. Furthermore, IL-6 and TNF-α in the wound tissue were significantly down-regulated in 2 and 6 days in collagen-based sponge group and anti-inflammatory cytokine IL-10 level was found to be upregulated throughout 12 days. These results cumulatively revealed that collagen-based sponge may serve as novel material for wound healing in the animal model.

SR-B1 involvement in keratinocytes in vitro wound closure

Skin represents the most extended organ of human body, having as main function the protection of our body from outdoor stressors. Its protective ability is compromised when the skin is disrupted as a consequence of mechanical insults. For this purpose, cutaneous tissue is equipped with an efficient and fine mechanism involved in repairing the wounded area. Among the numerous players that take part in the wound healing process, SR-B1 has been recently shown to have a role in keratinocyte re-epithelialization. SR-B1 is a mediator of cholesterol uptake from HDLs, whereas it is implicated in other cellular processes such as vitamins absorption, vesicle trafficking or pathogen identification. The aim of this study was to investigate the mechanisms involved in SR-B1 role in skin wound closure. Our in vitro data demonstrated that SR-B1 influenced keratinocyte proliferation and migration through a downregulation of nuclear cyclin D1 levels and active MMP9 expression respectively possibly in an NF-kB-dependent mechanism. In addition, SR-B1 was also able to modulate keratinocyte morphology into a pro-migratory cytoskeleton rearrangement. The present in vitro study suggests a new role of SRB1 as a possible new key player in cutaneous wound healing mechanism.

Recent Understandings of Biology, Prophylaxis and Treatment Strategies for Hypertrophic Scars and Keloids

Hypertrophic scars and keloids are fibroproliferative disorders that may arise after any deep cutaneous injury caused by trauma, burns, surgery, etc. Hypertrophic scars and keloids are cosmetically problematic, and in combination with functional problems such as contractures and subjective symptoms including pruritus, these significantly affect patients’ quality of life. There have been many studies on hypertrophic scars and keloids; but the mechanisms underlying scar formation have not yet been well established, and prophylactic and treatment strategies remain unsatisfactory. In this review, the authors introduce and summarize classical concepts surrounding wound healing and review recent understandings of the biology, prevention and treatment strategies for hypertrophic scars and keloids.

A functional chitosan-based hydrogel as a wound dressing and drug delivery system in the treatment of wound healing

Functional active wound dressings are expected to provide a moist wound environment, offer protection from secondary infections, remove wound exudate and accelerate tissue regeneration, as well as to improve the efficiency of wound healing. Chitosan-based hydrogels are considered as ideal materials for enhancing wound healing owing to their biodegradable, biocompatible, non-toxic, antimicrobial, biologically adhesive, biological activity and hemostatic effects. Chitosan-based hydrogels have been demonstrated to promote wound healing at different wound healing stages, and also can alleviate the factors against wound healing (such as excessive inflammatory and chronic wound infection). The unique biological properties of a chitosan-based hydrogel enable it to serve as both a wound dressing and as a drug delivery system (DDS) to deliver antibacterial agents, growth factors, stem cells and so on, which could further accelerate wound healing. For various kinds of wounds, chitosan-based hydrogels are able to promote the effectiveness of wound healing by modifying or combining with other polymers, and carrying different types of active substances. In this review, we will take a close look at the application of chitosan-based hydrogels in wound dressings and DDS to enhance wound healing.

Advances in keratinocyte delivery in burn wound care

This review gives an updated overview on keratinocyte transplantation in burn wounds concentrating on application methods and future therapeutic cell delivery options with a special interest in hydrogels and spray devices for cell delivery. To achieve faster re-epithelialisation of burn wounds, the original autologous keratinocyte culture and transplantation technique was introduced over 3 decades ago. Application types of keratinocytes transplantation have improved from cell sheets to single-cell solutions delivered with a spray system. However, further enhancement of cell culture, cell viability and function in vivo, cell carrier and cell delivery systems remain themes of interest. Hydrogels such as chitosan, alginate, fibrin and collagen are frequently used in burn wound care and have advantageous characteristics as cell carriers. Future approaches of keratinocyte transplantation involve spray devices, but optimisation of application technique and carrier type is necessary.

Chitosan nanoparticles loaded hydrogels promote skin wound healing through the modulation of reactive oxygen species

This study developed a novel bioactive chitosan nanoparticle loaded calcium alginate hydrogel to regulate inflammation and neovascularization for accelerated wound healing in vivo. It was found that chitosan nanoparticles loaded calcium alginate hydrogel exhibited remarkable antibacterial activity. Through the modulation of generation of ROS, it promoted the synthesis and secretion of IL-6 in vascular endothelial cell (VEC), suggesting its potential proinflammatory activation. Further, it promoted VEC invasion, metastasis and neovascularization to accelerate wound healing.

Involvement of RNA helicase p68 in skin wound healing process in rats

PURPOSE

RNA helicase p68 plays an important role in organ development and maturation through tuning cell proliferation. However, the character and role of p68 in the whole wound healing process need more study.

METHODS

First, we characterize expression of p68 in normal rat skin development postnatal. Then, we assayed dynamic change of p68 in rat skin from different stage after injury, and explored the role of p68 in proliferation and migration of three types of wound healing related cells.

RESULTS

p68 was down-regulated during skin developmental and maturation process, up-regulated after wound, peaked on day 14 and then significantly decreased. Wound fluid enhanced wound healing related cell proliferation and up-regulated expression of p68. Conversely, reducing p68 expression by RNA interference resulted in significantly slower proliferation and migration.

CONCLUSION

Our results define an important role of RNA helicase p68 in skin wound healing process.

IL-15 Enhances Activation and IGF-1 Production of Dendritic Epidermal T Cells to Promote Wound Healing in Diabetic Mice

Altered homeostasis and dysfunction of dendritic epidermal T cells (DETCs) contribute to abnormal diabetic wound healing. IL-15 plays important roles in survival and activation of T lymphocytes. Recently, reduction of epidermal IL-15 has been reported as an important mechanism for abnormal DETC homeostasis in streptozotocin -induced diabetic animals. However, the role of IL-15 in impaired diabetic wound healing remains unknown. Here, we found that, through rescuing the insufficient activation of DETCs, IL-15 increased IGF-1 production by DETCs and thereby promoted diabetic skin wound repair. Regulation of IGF-1 in DETCs by IL-15 was partly dependent on the mTOR pathway. In addition, expression of IL-15 and IGF-1 were positively correlated in wounded epidermis. Together, our data indicated that IL-15 enhanced IGF-1 production by DETCs to promoting diabetic wound repair, suggesting IL-15 as a potential therapeutic agent for managing diabetic wound healing.

Ozone oil promotes wound healing by increasing the migration of fibroblasts via PI3K/Akt/mTOR signaling pathway

Skin injury affects millions of people via the uncontrolled inflammation and infection. Many cellular components including fibroblasts and signaling pathways such as transforming growth factor-β (TGF-β) were activated to facilitate the wound healing to repair injured tissues. C57BL/6 female mice were divided into control and ozone oil treated groups. Excisional wounds were made on the dorsal skin and the fibroblasts were isolated from granulation tissues. The skin injured mouse model revealed that ozone oil could significantly decrease the wound area and accelerate wound healing compared with control group. QPCR and Western blotting assays showed that ozone oil up-regulated collagen I, α-SMA, and TGF-β1 mRNA and protein levels in fibroblasts. Wound healing assay demonstrated that ozone oil could increase the migration of fibroblasts. Western blotting assay demonstrated that ozone oil increased the epithelial–mesenchymal transition (EMT) process in fibroblasts via up-regulating fibronectin, vimentin, N-cadherin, MMP-2, MMP-9, insulin-like growth factor binding protein (IGFBP)-3, IGFBP5, and IGFBP6, and decreasing epithelial protein E-cadherin and cellular senescence marker p16 expression. Mechanistically, Western blotting assay revealed that ozone oil increased the phosphorylation of PI3K, Akt, and mTOR to regulate the EMT process, while inhibition of PI3K reversed this effect of ozone oil. At last, the results from Cytometric Bead Array (CBA) demonstrated ozone oil significantly decreased the inflammation in fibroblasts. Our results demonstrated that ozone oil facilitated the wound healing via increasing fibroblast migration and EMT process via PI3K/Akt/mTOR signaling pathway in vivo and in vitro. The cellular and molecular mechanisms we found here may provide new therapeutic targets for the treatment of skin injury.

Interleukin (IL)-6 modulates transforming growth factor-β receptor I and II (TGF-βRI and II) function in epidermal keratinocytes

It been shown that IL-6 modulates TGF-β1 expression in fibroblasts, however, what role IL-6 plays concerning TGF-βR expression and function in skin is unknown. Therefore, the aim of this study was to investigate the mechanism by which IL-6 might modulates TGF-β receptors in skin. Skin from WT, IL-6 over-expressing mice and IL-6 treated keratinocyte cultures was analysed for TGF-βRI and TGF-βRII expression via histology, PCR and flow cytometry. Receptor function was assessed by cell migration, bromodeoxyuridine (BrdU) proliferation assays, and Smad7 expression and Smad2/3 phosphorylation. Receptor localization within the membrane was determined by co-immunoprecipitation. IL-6 overexpression and treatment increased TGF-βRII expression in the epidermis. IL-6 treatment of keratinocytes induced TGF-βRI and II expression and augmented TGF-β1-induced function as demonstrated through increased migration and decreased proliferation. Additionally, IL-6 treatment of keratinocytes altered receptor activity as indicated by altered Smad2/3 phosphorylation and increased Smad7 and membrane localization. These results suggest that IL-6 regulates keratinocyte function by modulating TGF-βRI and II expression and signal transduction via trafficking of the receptor to lipid raft pools.

The role of secreted heat shock protein-90 (Hsp90) in wound healing - how could it shape future therapeutics?

INTRODUCTION

Defects in tissue repair or wound healing pose a clinical, economic and social problem worldwide. Despite decades of studies, there have been few effective therapeutic treatments. Areas covered: We discuss the possible reasons for why growth factor therapy did not succeed. We point out the lack of human disorder-relevant animal models as another blockade for therapeutic development. We summarize the recent discovery of secreted heat shock protein-90 (Hsp90) as a novel wound healing agent. Expert commentary: Wound healing is a highly complex and multistep process that requires participations of many cell types, extracellular matrices and soluble molecules to work together in a spatial and temporal fashion within the wound microenvironment. The time that wounds remain open directly correlates with the clinical mortality associated with wounds. This time urgency makes the healing process impossible to regenerate back to the unwounded stage, rather forces it to take many shortcuts in order to protect life. Therefore, for therapeutic purpose, it is crucial to identify so-called 'driver genes' for the life-saving phase of wound closure. Keratinocyte-secreted Hsp90α was discovered in 2007 and has shown the promise by overcoming several key hurdles that have blocked the effectiveness of growth factors during wound healing.

Acute Molecular Changes in Synovial Fluid Following Human Knee Injury: Association With Early Clinical Outcomes

Objective

To investigate whether molecules found to be up‐regulated within hours of surgical joint destabilization in the mouse are also elevated in the analogous human setting of acute knee injury, how this molecular response varies between individuals, and whether it is related to patient‐reported outcomes in the 3 months after injury.

Methods

Seven candidate molecules were analyzed in blood and synovial fluid (SF) from 150 participants with recent structural knee injury at baseline (<8 weeks from injury) and in blood at 14 days and 3 months following baseline. Knee Injury and Osteoarthritis Outcome Score 4 (KOOS₄) was obtained at baseline and 3 months. Patient and control samples were compared using Meso Scale Discovery platform assays or enzyme‐linked immunosorbent assay.

Results

Six of the 7 molecules were significantly elevated in human SF immediately after injury: interleukin‐6 (IL‐6), monocyte chemotactic protein 1, matrix metalloproteinase 3 (MMP‐3), tissue inhibitor of metalloproteinases 1 (TIMP‐1), activin A, and tumor necrosis factor–stimulated gene 6 (TSG‐6). There was low‐to‐moderate correlation with blood measurements. Three of the 6 molecules were significantly associated with baseline KOOS₄ (those with higher SF IL‐6, TIMP‐1, or TSG‐6 had lower KOOS₄). These 3 molecules, MMP‐3, and activin A were all significantly associated with greater improvement in KOOS₄ over 3 months, after adjustment for other relevant factors. Of these, IL‐6 alone significantly accounted for the molecular contribution to baseline KOOS₄ and change in KOOS₄ over 3 months.

Conclusion

Our findings validate relevant human biomarkers of tissue injury identified in a mouse model. Analysis of SF rather than blood more accurately reflects this response. The response is associated with patient‐reported outcomes over this early period, with SF IL‐6 acting as a single representative marker. Longitudinal outcomes will determine if these molecules are biomarkers of subsequent disease risk.

Laboratory Models for the Study of Normal and Pathologic Wound Healing

Current knowledge of wound healing is based on studies using various in vitro and in vivo wound models. In vitro models allow for biological examination of specific cell types involved in wound healing. In vivo models generally provide the full spectrum of biological responses required for wound healing, including inflammation and angiogenesis, and provide cell-cell interactions not seen in vitro. In this review, the authors aim to delineate the most relevant wound healing models currently available and to discuss their strengths and limitations in their approximation of the human wound healing processes to aid scientists in choosing the most appropriate wound healing models for designing, testing, and validating their experiments.

Conditional knockout of N-WASP in mouse fibroblast caused keratinocyte hyper proliferation and enhanced wound closure

Neural-Wiskott Aldrich Syndrome Protein (N-WASP) is expressed ubiquitously, regulates actin polymerization and is essential during mouse development. We have previously shown that N-WASP is critical for cell-ECM adhesion in fibroblasts. To characterize the role of N-WASP in fibroblast for skin development, we generated a conditional knockout mouse model in which fibroblast N-WASP was ablated using the Cre recombinase driven by Fibroblast Specific Protein promoter (Fsp-Cre). N-WASP^FKO (N-WASP^fl/fl; Fsp-cre) were born following Mendelian genetics, survived without any visible abnormalities for more than 1 year and were sexually reproductive, suggesting that expression of N-WASP in fibroblast is not critical for survival under laboratory conditions. Histological sections of N-WASP^FKO mice skin (13 weeks old) showed thicker epidermis with higher percentage of cells staining for proliferation marker (PCNA), suggesting that N-WASP deficient fibroblasts promote keratinocyte proliferation. N-WASP^FKO mice skin had elevated collagen content, elevated expression of FGF7 (keratinocyte growth factor) and TGFβ signaling proteins. Wound healing was faster in N-WASP^FKO mice compared to control mice and N-WASP deficient fibroblasts were found to have enhanced collagen gel contraction properties. These results suggest that N-WASP deficiency in fibroblasts improves wound healing by growth factor-mediated enhancement of keratinocyte proliferation and increased wound contraction in mice.

Specific disruption of Lnk in murine endothelial progenitor cells promotes dermal wound healing via enhanced vasculogenesis, activation of myofibroblasts, and suppression of inflammatory cell recruitment

BACKGROUND

Although endothelial progenitor cells (EPCs) contribute to wound repair by promoting neovascularization, the mechanism of EPC-mediated wound healing remains poorly understood due to the lack of pivotal molecular targets of dermal wound repair.

METHODS AND RESULTS

We found that genetic targeting of the Lnk gene in EPCs dramatically enhances the vasculogenic potential including cell proliferation, migration, and tubule-like formation as well as accelerates in vivo wound healing, with a reduction in fibrotic tissue and improved neovascularization via significant suppression of inflammatory cell recruitment. When injected into wound sites, Lnk ^-/- EPCs gave rise to a significant number of new vessels, with remarkably increased survival of transplanted cells and decreased recruitment of cytotoxic T cells, macrophages, and neutrophils, but caused activation of fibroblasts in the wound-remodeling phase. Notably, in a mouse model of type I diabetes, transplanted Lnk ^-/- EPCs induced significantly better wound healing than Lnk ^+/+ EPCs did.

CONCLUSIONS

The specific targeting of Lnk may be a promising EPC-based therapeutic strategy for dermal wound healing via improvement of neovascularization but inhibition of excessive inflammation as well as activation of myofibroblasts during dermal tissue remodeling.

Can Human Recombinant Epidermal Growth Factor Improve Ischemia and Induce Healing of Anastomosis in an Experimental Study in a Rabbit Model?

PURPOSE

Anastomotic leaks following intestinal operations may cause devastating effects on patients. Ischemia may also occur at the intestinal walls in the presence of strangulations. In this study, we examined the effects of human recombinant (Hr)-epidermal growth factor (EGF) given at a single intramural dose into the intestinal walls and daily intraperitoneal cavity on ischemia and the healing process of anastomosis.

MATERIALS AND METHODS

Sixteen male New Zeland white rabbits were randomly divided into four groups (n = 4 in each group). In Group 1, two different segments of ileum were identified and, then, transected and the free ends were sutured each other. In the other groups, ischemia was induced by ligating the mesenteric vascular arcade. After the ischemic induction, Group 2 received intramural injections of %0.9 saline, Group 3 received intramural injections of a single dose of EGF, and Group 4 received intramural and intraperitoneal injections of EGF. Bursting pressures and tissue hydroxyproline levels were analyzed. Necrosis, fibroblastic activity, collagen deposition and neovascularization were also studied.

RESULTS

The mean levels of bursting pressures in Group 4 (148.6 ± 25.3 mmHg) were higher than Group 2 (70 ± 21.5 mmHg) (p = 0.001). The mean level of bursting pressures was not statistically significant between Group 1 (170.1 ± 35 mmHg) and Group 4 (p = 0.073). Hydroxyproline levels in Group 2 were lower than Groups 3 and 4. There was a statistically significant difference in the mucosal ischemia, mucosal healing and degree of adhesion, but not in the mural anastomotic healing among the groups.

CONCLUSIONS

Intramural injection with daily intraperitoneal administration of low-dose EGF enhances the bursting pressure and collagen accumulation in ischemic anastomosis, improving many histological variables associated with ischemic intestinal anastomosis.