Phase I trial on the safety of topical rhVEGF on chronic neuropathic diabetic foot ulcers

The effect of VEGF stimulation in diabetic foot ulcers: A systematic review

Diabetic foot ulcers are a common and severe complication of diabetes mellitus, and a risk factor for amputation. Because of the vessel insufficiency in diabetic foot ulcers (DFU), vascular endothelial growth factor (VEGF) that simulates angiogenesis is of interest to promote wound healing. This systematic review evaluates the last 16 years of in-vivo studies with VEGF stimulation as a treatment for DFU, developed based on the last published systematic article. A total of 961 articles were identified through databases in two phases. 947 articles were excluded by exclusion criteria, and four articles met our inclusion criteria and were included. The effects of VEGF on wound healing were analysed in all four studies. In three studies, the VEGF-treated wounds showed statistically faster healing than those not treated with VEGF. In one study, the VEGF-treated wounds revealed a positive trend toward faster healing. Furthermore, all four studies were in favor of using VEGF, but concluded that further research is needed. These studies showed a positive trend towards faster healing and was safe when using VEGF topically on humans. Furthermore, viral particles of VEGF seem to have a systematic effect when a dose exceeding 5.0 × 109 vp pr wound. Future research in using VEGF on DFU should focus on VEGF's relevant dosage, release rate, and specific mechanism. This review inspires further research, and a consistent study design is prerequisite such that results are more homogenic and comparable. Much effort is needed to translate the results into our clinical practice.

Effectiveness of interventions to enhance healing of chronic foot ulcers in diabetes: A systematic review

BACKGROUND

It is critical that interventions used to enhance the healing of chronic foot ulcers in diabetes are backed by high-quality evidence and cost-effectiveness. In previous years, the systematic review accompanying guidelines published by the International Working Group of the Diabetic Foot performed 4-yearly updates of previous searches, including trials of prospective, cross-sectional and case-control design.

AIMS

Due to a need to re-evaluate older studies against newer standards of reporting and assessment of risk of bias, we performed a whole new search from conception, but limiting studies to randomised control trials only.

MATERIALS AND METHODS

For this systematic review, we searched PubMed, Scopus and Web of Science databases for published studies on randomised control trials of interventions to enhance healing of diabetes-related foot ulcers. We only included trials comparing interventions to standard of care. Two independent reviewers selected articles for inclusion and assessed relevant outcomes as well as methodological quality.

RESULTS

The literature search identified 22,250 articles, of which 262 were selected for full text review across 10 categories of interventions. Overall, the certainty of evidence for a majority of wound healing interventions was low or very low, with moderate evidence existing for two interventions (sucrose-octasulfate and leucocyte, platelet and fibrin patch) and low quality evidence for a further four (hyperbaric oxygen, topical oxygen, placental derived products and negative pressure wound therapy). The majority of interventions had insufficient evidence.

CONCLUSION

Overall, the evidence to support any other intervention to enhance wound healing is lacking and further high-quality randomised control trials are encouraged.

Guidelines on interventions to enhance healing of foot ulcers in people with diabetes (IWGDF 2023 update)

AIMS

Principles of wound management, including debridement, wound bed preparation, and newer technologies involving alternation of wound physiology to facilitate healing, are of utmost importance when attempting to heal a chronic diabetes-related foot ulcer. However, the rising incidence and costs of diabetes-related foot ulcer management necessitate that interventions to enhance wound healing of chronic diabetes-related foot ulcers are supported by high-quality evidence of efficacy and cost effectiveness when used in conjunction with established aspects of gold-standard multidisciplinary care. This is the 2023 International Working Group on the Diabetic Foot (IWGDF) evidence-based guideline on wound healing interventions to promote healing of foot ulcers in persons with diabetes. It serves as an update of the 2019 IWGDF guideline.

MATERIALS AND METHODS

We followed the GRADE approach by devising clinical questions and important outcomes in the Patient-Intervention-Control-Outcome (PICO) format, undertaking a systematic review, developing summary of judgements tables, and writing recommendations and rationale for each question. Each recommendation is based on the evidence found in the systematic review and, using the GRADE summary of judgement items, including desirable and undesirable effects, certainty of evidence, patient values, resources required, cost effectiveness, equity, feasibility, and acceptability, we formulated recommendations that were agreed by the authors and reviewed by independent experts and stakeholders.

RESULTS

From the results of the systematic review and evidence-to-decision making process, we were able to make 29 separate recommendations. We made a number of conditional supportive recommendations for the use of interventions to improve healing of foot ulcers in people with diabetes. These include the use of sucrose octasulfate dressings, the use of negative pressure wound therapies for post-operative wounds, the use of placental-derived products, the use of the autologous leucocyte/platelet/fibrin patch, the use of topical oxygen therapy, and the use of hyperbaric oxygen. Although in all cases it was stressed that these should be used where best standard of care was not able to heal the wound alone and where resources were available for the interventions.

CONCLUSIONS

These wound healing recommendations should support improved outcomes for people with diabetes and ulcers of the foot, and we hope that widescale implementation will follow. However, although the certainty of much of the evidence on which to base the recommendations is improving, it remains poor overall. We encourage not more, but better quality trials including those with a health economic analysis, into this area.

The Combination of Vascular Endothelial Growth Factor A (VEGF-A) and Fibroblast Growth Factor 1 (FGF1) Modified mRNA Improves Wound Healing in Diabetic Mice: An Ex Vivo and In Vivo Investigation

BACKGROUND

Diabetic foot ulcers (DFU) pose a significant health risk in diabetic patients, with insufficient revascularization during wound healing being the primary cause. This study aimed to assess microvessel sprouting and wound healing capabilities using vascular endothelial growth factor (VEGF-A) and a modified fibroblast growth factor (FGF1).

METHODS

An ex vivo aortic ring rodent model and an in vivo wound healing model in diabetic mice were employed to evaluate the microvessel sprouting and wound healing capabilities of VEGF-A and a modified FGF1 both as monotherapies and in combination.

RESULTS

The combination of VEGF-A and FGF1 demonstrated increased vascular sprouting in the ex vivo mouse aortic ring model, and topical administration of a combination of VEGF-A and FGF1 mRNAs formulated in lipid nanoparticles (LNPs) in mouse skin wounds promoted faster wound closure and increased neovascularization seven days post-surgical wound creation. RNA-sequencing analysis of skin samples at day three post-wound creation revealed a strong transcriptional response of the wound healing process, with the combined treatment showing significant enrichment of genes linked to skin growth.

CONCLUSION

f-LNPs encapsulating VEGF-A and FGF1 mRNAs present a promising approach to improving the scarring process in DFU.

Functional characterization of the dimeric form of PDGF-derived fusion peptide fabricated based on theoretical arguments

A skin wound leads to the loss of skin integrity and the influx of pathogens into the tissue. Platelet-derived growth factors (PDGFs) are cytokines released from alpha granules during wound healing and interact with their cell surface receptors and activate signals involved in chemotaxis, growth, proliferation, and differentiation pathways. Due to the low stability of growth factors (GFs), a new peptide-derived PDGF-BB was designed, expressed in the Shuffle strain of E. coli, and purified by Ni-NTA agarose affinity column chromatography. The effect of fusion peptide was then evaluated on L929 fibroblast cells and animal models with skin lesions. In vitro, studies showed that the peptide led to an increase in the migration of fibroblast cells in the scratch assay. Its positive effect on wound healing was also observed in the skin-injured rats after 3, 7, and 12 days. A significant rise in neutrophils and granular tissue formation, re-epithelialization, angiogenesis, and collagen formation was exhibited on the third day of treatment when compared to the control group. The results showed that, despite reducing PDGF size, the fusion peptide was able to maintain at least some of the known functions attributed to full-length PDGF and showed positive results in wound healing.

Comparative efficacy of growth factor therapy in healing diabetes-related foot ulcers: A network meta-analysis of randomized controlled trials

INTRODUCTION

This study examined the relative efficacy of growth factor therapies in healing diabetes-related foot ulcers (DFU).

METHODS

PubMed and Cochrane databases were searched for randomized controlled trials testing growth factor therapies for treating DFU. The primary outcome was complete wound closure. Results were reported as relative risk (RR) ± 95% credible intervals (CrI). The risk of bias was assessed using Cochrane's RoB-2 tool.

RESULTS

A total of 31 RCTs involving 2174 participants were included. Only 13 of the trials (n = 924) reported on the aetiology of the ulcers (85.4% neuropathic and 14.6% ischaemic). Epidermal growth factor (RR 3.83; 95% CrI 1.81, 9.10), plasma-rich protein (PRP) (RR 3.36; 95% CrI 1.66, 8.03) and platelet-derived growth factor (PDGF) (RR 2.47; 95% CrI 1.23, 5.17) significantly improved the likelihood of complete ulcer healing compared to control. Sub-analyses suggested that PRP (3 trials - RR 9.69; 95% CrI 1.37, 103.37) and PDGF (6 trials - RR 2.22; 95% CrI 1.12, 5.19) significantly improved the likelihood of wound closure amongst trial mainly recruiting participants with neuropathic ulcers. Eleven trials had a low risk of bias, 9 had some concerns and 11 had a high risk of bias. Sub-analysis of trials with a low risk of bias suggested that none of the growth factors significantly improved ulcer healing compared with control.

DISCUSSION

This network meta-analysis found low-quality evidence that Epidermal growth factor, PRP and PDGF therapy improved DFU healing likelihood compared with control. Larger well-designed trials are needed.

Therapeutic role of growth factors in treating diabetic wound

Wounds in diabetic patients, especially diabetic foot ulcers, are more difficult to heal compared with normal wounds and can easily deteriorate, leading to amputation. Common treatments cannot heal diabetic wounds or control their many complications. Growth factors are found to play important roles in regulating complex diabetic wound healing. Different growth factors such as transforming growth factor beta 1, insulin-like growth factor, and vascular endothelial growth factor play different roles in diabetic wound healing. This implies that a therapeutic modality modulating different growth factors to suit wound healing can significantly improve the treatment of diabetic wounds. Further, some current treatments have been shown to promote the healing of diabetic wounds by modulating specific growth factors. The purpose of this study was to discuss the role played by each growth factor in therapeutic approaches so as to stimulate further therapeutic thinking.

VEGF-Encoding, Gene-Activated Collagen-Based Matrices Promote Blood Vessel Formation and Improved Wound Repair

Disruption in vascularization during wound repair can severely impair healing. Proangiogenic growth factor therapies have shown great healing potential; however, controlling growth factor activity and cellular behavior over desired healing time scales remains challenging. In this study, we evaluated collagen-mimetic peptide (CMP) tethers for their capacity to control growth factor gene transfer and growth factor activity using our recently developed gene-activated hyaluronic acid-collagen matrix (GAHCM). GAHCM was comprised of DNA/polyethyleneimine (PEI) polyplexes that were retained on hyaluronic acid (HA)-collagen hydrogels using CMPs. We hypothesized that using CMP-collagen tethers to control vascular endothelial growth factor-A (VEGF-A) gene delivery in fibroblasts would provide a powerful strategy to modulate the proangiogenic behaviors of endothelial cells (ECs) for blood vessel formation, resulting in enhanced wound repair. In co-culture experiments, we observed that CMP-modified GAHCM induced tunable gene delivery in fibroblasts as predicted, and correspondingly, VEGF-A produced by the fibroblasts led to increased growth and persistent migration of ECs for at least 7 days, as compared to non-CMP-modified GAHCM. Moreover, when ECs were exposed to fibroblast-containing VEGF-GAHCM with higher levels of CMP modification (50% CMP-PEI, or 50 CP), high CD31 expression was stimulated, resulting in the formation of an interconnected EC network with a significantly higher network volume and a larger diameter network structure than controls. Application of VEGF-GAHCM with 50 CP in murine splinted excisional wounds facilitated prolonged prohealing and proangiogenic responses resulting in increased blood vessel formation, improved granulation tissue formation, faster re-epithelialization, and overall enhanced repair. These findings suggest the benefits of CMP-collagen tethers as useful tools to control gene transfer and growth factor activity for improved treatment of wounds.

Research progress of functional motifs based on growth factors in cartilage tissue engineering: A review

Osteoarthritis is a chronic degenerative joint disease that exerts significant impacts on personal life quality, and cartilage tissue engineering is a practical treatment in clinical. Various growth factors are involved in cartilage regeneration and play important roles therein, which is the focus of current cartilage repair strategy. To compensate for the purification difficulty, high cost, poor metabolic stability, and circulating dilution of natural growth factors, the concept of functional motifs (also known as mimetic peptides) from original growth factor was introduced in recent studies. Here, we reviewed the selection mechanisms, biological functions, carrier scaffolds, and modification methods of growth factor-related functional motifs, and evaluated the repair performance in cartilage tissue engineering. Finally, the prospects of functional motifs in researches and clinical application were discussed.

PLCL/PCL Dressings with Platelet Lysate and Growth Factors Embedded in Fibrin for Chronic Wound Regeneration

Introduction

The formation of diabetic ulcers (DU) is a common complication for diabetic patients resulting in serious chronic wounds. There is therefore, an urgent need for complex treatment of this problem. This study examines a bioactive wound dressing of a biodegradable electrospun nanofibrous blend of poly(L-lactide-co-ε-caprolactone) and poly(ε-caprolactone) (PLCL/PCL) covered by a thin fibrin layer for sustained delivery of bioactive molecules.

Methods

Electrospun PLCL/PCL nanofibers were coated with fibrin-based coating prepared by a controlled technique and enriched with human platelet lysate (hPL), fibroblast growth factor 2 (FGF), and vascular endothelial growth factor (VEGF). The coating was characterized by scanning electron microscopy and fluorescent microscopy. Protein content and its release rate and the effect on human saphenous vein endothelial cells (HSVEC) were evaluated.

Results

The highest protein amount is achieved by the coating of PLCL/PCL with a fibrin mesh containing 20% v/v hPL (NF20). The fibrin coating serves as an excellent scaffold to accumulate bioactive molecules from hPL such as PDGF-BB, fibronectin (Fn), and α-2 antiplasmin. The NF20 coating shows both fast and a sustained release of the attached bioactive molecules (Fn, VEGF, FGF). The dressing significantly increases the viability of human saphenous vein endothelial cells (HSVECs) cultivated on a collagen-based wound model. The exogenous addition of FGF and VEGF during the coating procedure further increases the HSVECs viability. In addition, the presence of α-2 antiplasmin significantly stabilizes the fibrin mesh and prevents its cleavage by plasmin.

Discussion

The NF20 coating supplemented with FGF and VEGF provides a promising wound dressing for the complex treatment of DU. The incorporation of various bioactive molecules from hPL and growth factors has great potential to support the healing processes by providing appropriate stimuli in the chronic wound.

Platelet-rich plasma: a comparative and economical therapy for wound healing and tissue regeneration

Rise in the incidences of chronic degenerative diseases with aging makes wound care a socio-economic burden and unceasingly necessitates a novel, economical, and efficient wound healing treatment. Platelets have a crucial role in hemostasis and thrombosis by modulating distinct mechanistic phases of wound healing, such as promoting and stabilizing the clot. Platelet-rich plasma (PRP) contains a high concentration of platelets than naïve plasma and has an autologous origin with no immunogenic adverse reactions. As a consequence, PRP has gained significant attention as a therapeutic to augment the healing process. Since the past few decades, a robust volume of research and clinical trials have been performed to exploit extensive role of PRP in wound healing/tissue regeneration. Despite these rigorous studies and their application in diversified medical fields, efficacy of PRP-based therapies is continuously questioned owing to the paucity of large samplesizes, controlled clinical trials, and standard protocols. This review systematically delineates the process of wound healing and involvement of platelets in tissue repair mechanisms. Additionally, emphasis is laid on PRP, its preparation methods, handling, classification,application in wound healing, and PRP as regenerative therapeutics combined with biomaterials and mesenchymal stem cells (MSCs).

An appraisal of vascular endothelial growth factor (VEGF): the dynamic molecule of wound healing and its current clinical applications

Angiogenesis is a critical step of wound healing, and its failure leads to chronic wounds. The idea of restoring blood flow to the damaged tissues by promoting neo-angiogenesis is lucrative and has been researched extensively. Vascular endothelial growth factor (VEGF), a key dynamic molecule of angiogenesis has been investigated for its functions. In this review, we aim to appraise its biology, the comprehensive role of this dynamic molecule in the wound healing process, and how this knowledge has been translated in clinical application in various types of wounds. Although, most laboratory research on the use of VEGF is promising, its clinical applications have not met great expectations. We discuss various lacunae that might exist in making its clinical application unsuccessful for commercial use, and provide insight to the foundation for future research.

Novel Three-Dimensional Knitted Fabric for Pressure Ulcer Prevention: Preliminary Clinical Application and Testing in a Diabetic Mouse Model of Pressure Ulcers

Background  Population aging has led to an increased incidence of pressure ulcers, resulting in a social burden and economic costs. We developed a three-dimensional knitted fabric (3-DKF) with a pressure-reducing function that can be applied topically in the early stages of pressure ulcers to prevent progression.

Methods  We evaluated the effects of the 3-DKF in a streptozotocin-induced diabetes mellitus pressure ulcer mouse model, and the fabric was preliminarily applied to patients. Twelve-week-old male C57BL/6 mice were used for the animal experiments. In the pressure ulcer mouse model, an ischemia-reperfusion injury was created using a magnet on the dorsa of the mice. Pressure was measured with BodiTrak before and after applying the 3-DKF to 14 patients at risk of sacral pressure ulcers.

Results  In the 3-DKF-applied mice group, the ulcers were shallower and smaller than those in the control group. Compared with the mice in the control group, the 3-DKF group had lower platelet-derived growth factor-α and neutrophil elastase expression, as parameters related to inflammation, and increased levels of transforming growth factor (TGF)-β1, TGF-β3, proliferating cell nuclear antigen, and α-smooth muscle actin, which are related to growth factors and proliferation. Additionally, typical normal tissue staining patterns were observed in the 3-DKF group. In the preliminary clinical analysis, the average skin pressure was 26.2 mm Hg before applying the 3-DKF, but it decreased to an average of 23.4 mm Hg after 3-DKF application.

Conclusion  This study demonstrated that the newly developed 3-DKF was effective in preventing pressure ulcers through testing in a pressure ulcer animal model and preliminary clinical application.

Cell-Biomaterial Constructs for Wound Healing and Skin Regeneration

Over the years, conventional skin grafts, such as full-thickness, split-thickness, and pre-sterilized grafts from human or animal sources, have been at the forefront of skin wound care. However, these conventional grafts are associated with major challenges, including supply shortage, rejection by the immune system, and disease transmission following transplantation. Due to recent progress in nanotechnology and material sciences, advanced artificial skin grafts-based on the fundamental concepts of tissue engineering-are quickly evolving for wound healing and regeneration applications, mainly because they can be uniquely tailored to meet the requirements of specific injuries. Despite tremendous progress in tissue engineering, many challenges and uncertainties still face skin grafts in vivo, such as how to effectively coordinate the interaction between engineered biomaterials and the immune system to prevent graft rejection. Furthermore, in-depth studies on skin regeneration at the molecular level are lacking; as a consequence, the development of novel biomaterial-based systems that interact with the skin at the core level has also been slow. This review will discuss 1) the biological aspects of wound healing and skin regeneration, 2) important characteristics and functions of biomaterials for skin regeneration applications, and 3) synthesis and applications of common biomaterials for skin regeneration. Finally, the current challenges and future directions of biomaterial-based skin regeneration will be addressed.

Approaches for Regenerative Healing of Cutaneous Wound with an Emphasis on Strategies Activating the Wnt/β-Catenin Pathway

Significance: In adult mammals, spontaneous repair of a cutaneous wound occurs slowly and leaves a scar with skin adnexa deficiencies. To accelerate cutaneous wound-healing rates and avoid scar formation, current studies have focused on regenerative therapies. Recent Advances: Emerging therapeutics for regenerative wound healing often focus on the use of growth factors and stem cells. However, these therapeutic approaches have limited routine clinical use due to high costs and technical requirements. Critical Issue: Understanding the molecular mechanisms involved in the signaling pathways for cutaneous wound healing and neogenic synthesis of the skin components is important for identification of novel targets for the development of regenerative wound-healing agents. Future Directions: The Wnt/β-catenin pathway is a well-known key player for enhancement of the overall healing process involving tissue regeneration via crosstalk with other signaling pathways. Strategies that activate the Wnt/β-catenin pathway via modulation of the pathway-controlling regulatory factors could provide effective therapeutic approaches for regenerative wound healing.

Therapeutic arteriogenesis by factor-decorated fibrin matrices promotes wound healing in diabetic mice

Chronic wounds in type-2 diabetic patients present areas of severe local skin ischemia despite mostly normal blood flow in deeper large arteries. Therefore, restoration of blood perfusion requires the opening of arterial connections from the deep vessels to the superficial skin layer, that is, arteriogenesis. Arteriogenesis is regulated differently from microvascular angiogenesis and is optimally stimulated by high doses of Vascular Endothelial Growth Factor-A (VEGF) together with Platelet-Derived Growth Factor-BB (PDGF-BB). Here we found that fibrin hydrogels decorated with engineered versions of VEGF and PDGF-BB proteins, to ensure protection from degradation and controlled delivery, efficiently accelerated wound closure in diabetic and obese db/db mice, promoting robust microvascular growth and a marked increase in feeding arterioles. Notably, targeting the arteriogenic factors to the intact arterio-venous networks in the dermis around the wound was more effective than the routine treatment of the inflamed wound bed. This approach is readily translatable to a clinical setting.

Bioactive glass-based fibrous wound dressings

Since the discovery of silicate bioactive glass (BG) by Larry Hench in 1969, different classes of BGs have been researched over decades mainly for bone regeneration. More recently, validating the beneficial influence of BGs with tailored compositions on angiogenesis, immunogenicity and bacterial infection, the applicability of BGs has been extended to soft tissue repair and wound healing. Particularly, fibrous wound dressings comprising BG particle reinforced polymer nanofibers and cotton-candy-like BG fibers have been proven to be successful for wound healing applications. Such fibrous dressing materials imitate the physical structure of skin’s extracellular matrix and release biologically active ions e.g. regenerative, pro-angiogenic and antibacterial ions, e.g. borate, copper, zinc, etc., that can provoke cellular activities to regenerate the lost skin tissue and to induce new vessels formation, while keeping an anti-infection environment. In the current review, we discuss different BG fibrous materials meant for wound healing applications and cover the relevant literature in the past decade. The production methods for BG-containing fibers are explained and as fibrous wound dressing materials, their wound healing and bactericidal mechanisms, depending on the ions they release, are discussed. The present gaps in this research area are highlighted and new strategies to address them are suggested.

Nanotechnology-based therapeutic applications: in vitro and in vivo clinical studies for diabetic wound healing

Diabetic wounds often indicate chronic complications that are difficult to treat. Unfortunately, existing conventional treatment modalities often cause unpremeditated side effects, given the need to develop alternative therapeutic phenotypes that are safe or have minimal side effects and risks. Nanotechnology-based platforms, including nanotherapeutics, nanoparticles (NPs), nanofibers, nanohydrogels, and nanoscaffolds, have garnered attention for their groundbreaking potential to decipher the biological environment and offer personalized treatment methods for wound healing. These nanotechnology-based platforms can successfully overcome the impediments posed by drug toxicity, existing treatment modalities, and the physiology and complexity of the wound sites. Furthermore, studies have shown that they play an essential role in influencing angiogenesis, collagen production, and extracellular matrix (ECM) synthesis, which are integral in skin repair mechanisms. In this review, we emphasized the importance of various nanotechnology-based platforms for healing diabetic wounds and report on the innovative preclinical and clinical outcomes of different nanotechnology-based platforms. This review also outlined the limitations of existing conventional treatment modalities and summarized the physiology of acute and chronic diabetic wounds.

Advancements in the Delivery of Growth Factors and Cytokines for the Treatment of Cutaneous Wound Indications

Significance: Wound healing involves the phasic production of growth factors (GFs) and cytokines to progress an acute wound to a resolved scar. Dysregulation of these proteins contributes to both wound chronicity and excessive scarring. Direct supplementation of GFs and cytokines for treatment of healing and scarring complications has, however, been disappointing. Failings likely relate to an inability to deliver recombinant proteins at physiologically relevant levels to an environment conducive to healing. Recent Advances: Inspired by the extracellular matrix, natural biomaterials have been developed that resemble human skin, and are capable of delivering bioactives. Hybrid biomaterials made using multiple polymers, fabrication methods, and proteins are proving efficacious in animal models of acute and impaired wound healing. Critical Issues: For clinical translation, these delivery systems must be tailored for specific wound indications and the correct phase of healing. GFs and cytokines must be delivered in a controlled manner that will target specific healing or scarring impairments. Preclinical assessment in clinically relevant animal models of impaired or excessive healing is critical. Future Directions: Clinical success will likely depend on the GF or cytokine selected, their compatibility with the chosen biomaterial(s), degradation rate of the fabricated system, and the degree of control over release kinetics. Further testing is essential to assess which wound indications are most suited to specific delivery systems and to prove whether they provide superior efficacy over direct protein therapies.

Amniotic fluid allograft enhances the host response to ventral hernia repair using acellular dermal matrix

Ventral hernia repair (VHR) with acellular dermal matrix (ADM) has high rates of recurrence that may be improved with allogeneic growth factor augmentation such as amniotic fluid allograft (AFA). We hypothesized that AFA would modulate the host response to improve ADM incorporation in VHR. Lewis rats underwent chronic VHR with porcine ADM alone or with AFA augmentation. Tissue harvested at 3, 14, or 28 days was assessed for region-specific cellularity, and a validated histomorphometric score was generated for tissue incorporation. Expression of pro-inflammatory (Nos1, Tnfα), anti-inflammatory (Arg1, Il-10, Mrc1) and tissue regeneration (Col1a1, Col3a1, Vegf, and alpha actinin-2) genes were quantified using quantitative reverse-transcription polymerase chain reaction. Amniotic fluid allograft treatment caused enhanced vascularization and cellularization translating to increased histomorphometric scores at 14 days, likely mediated by upregulation of pro-regeneration genes throughout the study period and molecular evidence of anti-inflammatory, M2-polarized macrophage phenotype. Collectively, this suggests AFA may have a therapeutic role as a VHR adjunct.

Tannic acid-inspired, self-healing, and dual stimuli responsive dynamic hydrogel with potent antibacterial and anti-oxidative properties

Due to their intrinsic injectable and self-healing characteristics, dynamic hydrogels, based on dynamic covalent bonds, have gained a great attention. In this study, a novel dynamic hydrogel based on the boronic ester dynamic covalent bond is facilely developed using phenylboronic acid-modified hyaluronic acid (HA-PBA) and plant-derived polyphenol-tannic acid (TA). The dynamic hydrogel gelated quickly under mild conditions and had favorable viscoelastic properties with good self-healing and shear-thinning capabilities. Moreover, the simultaneous utilization of TA as a reductant for the green synthesis of silver nanoparticles (AgNP) inspired the preparation of a TA-reduced AgNP hybrid dynamic hydrogel with potent and broad-spectrum antibacterial activities. The dynamic hydrogels could also be applied for pH- and reactive oxygen species (ROS)-responsive release of loaded protein molecules without showing evident cytotoxicity and hemolysis in vitro. In addition, the dynamic hydrogels showed the anti-oxidative properties of high free radical and ROS scavenging capacity, which was verified by the DPPH (2,2-diphenyl-1-picryl-hydrazyl-hydrate) free radical assay and ROS fluorescence staining. Overall, this novel class of cytocompatible, self-healing, dual stimuli responsive, antibacterial, anti-oxidative, and injectable hydrogels could be promising as a wound dressing for chronic wound healing.

Robust Angiogenesis and Arteriogenesis in the Skin of Diabetic Mice by Transient Delivery of Engineered VEGF and PDGF-BB Proteins in Fibrin Hydrogels

Non-healing ulcers are a serious complication of diabetes mellitus and a major unmet medical need. A major cause for the lack of healing is the impairment of spontaneous vascularization in the skin, despite mostly normal blood flow in deeper large vessels. Therefore, pro-angiogenic treatments are needed to increase therapeutic perfusion by recruiting new arterial connections (therapeutic arteriogenesis). Vascular endothelial growth factor (VEGF) is the master regulator of angiogenesis in physiology and disease, but exploitation of its therapeutic potential requires careful control of its dose distribution in tissue. Co-delivery of platelet derived growth factor-BB (PDGF-BB) has been shown to expand the therapeutic window of VEGF and also improve associated arteriogenesis. We used a highly controlled protein delivery system, based on a clinically applicable fibrin-based platform, to investigate the angiogenic and arteriogenic potential of engineered versions (TG-) of VEGF and PDGF-BB proteins in the skin of diabetic and obese db/db mice. Intradermal delivery of therapeutically relevant doses of TG-VEGF and TG-PDGF-BB induced robust growth of new microvascular networks with similar efficacy as in normal littermate control mice. Further, TG-PDGF-BB prevented the formation of aberrant vascular enlargements by high TG-VEGF levels. As fibrin was degraded after the first week, the induced angiogenesis mostly regressed by 4 weeks, but it promoted effective arteriogenesis in the dermal layer. Therefore, controlled co-delivery of TG-VEGF and TG-PDGF-BB recombinant proteins is effective to induce angiogenesis and arteriogenesis in diabetic mouse skin and should be further investigated to promote diabetic wound healing.

Mathematical Model Predicts that Acceleration of Diabetic Wound Healing is Dependent on Spatial Distribution of VEGF-A mRNA (AZD8601)

Introduction

Pharmacologic approaches for promoting angiogenesis have been utilized to accelerate healing of chronic wounds in diabetic patients with varying degrees of success. We hypothesize that the distribution of proangiogenic drugs in the wound area critically impacts the rate of closure of diabetic wounds. To evaluate this hypothesis, we developed a mathematical model that predicts how spatial distribution of VEGF-A produced by delivery of a modified mRNA (AZD8601) accelerates diabetic wound healing.

Methods

We modified a previously published model of cutaneous wound healing based on coupled partial differential equations that describe the density of sprouting capillary tips, chemoattractant concentration, and density of blood vessels in a circular wound. Key model parameters identified by a sensitivity analysis were fit to data obtained from an in vivo wound healing study performed in the dorsum of diabetic mice, and a pharmacokinetic model was used to simulate mRNA and VEGF-A distribution following injections with AZD8601. Due to the limited availability of data regarding the spatial distribution of AZD8601 in the wound bed, we performed simulations with perturbations to the location of injections and diffusion coefficient of mRNA to understand the impact of these spatial parameters on wound healing.

Results

When simulating injections delivered at the wound border, the model predicted that injections delivered on day 0 were more effective in accelerating wound healing than injections delivered at later time points. When the location of the injection was varied throughout the wound space, the model predicted that healing could be accelerated by delivering injections a distance of 1–2 mm inside the wound bed when compared to injections delivered on the same day at the wound border. Perturbations to the diffusivity of mRNA predicted that restricting diffusion of mRNA delayed wound healing by creating an accumulation of VEGF-A at the wound border. Alternatively, a high mRNA diffusivity had no effect on wound healing compared to a simulation with vehicle injection due to the rapid loss of mRNA at the wound border to surrounding tissue.

Conclusions

These findings highlight the critical need to consider the location of drug delivery and diffusivity of the drug, parameters not typically explored in pre-clinical experiments, when designing and testing drugs for treating diabetic wounds.

Supplementary Information

The online version contains supplementary material available at 10.1007/s12195-021-00678-9.

In vitro vascularization of tissue engineered constructs by non-viral delivery of pro-angiogenic genes

Vascularization is still one of the major challenges in tissue engineering. In the context of tissue regeneration, the formation of capillary-like structures is often triggered by the addition of growth factors which are associated with high cost, bolus release and short half-life. As an alternative to growth factors, we hypothesized that delivering genes-encoding angiogenic growth factors to cells in a scaffold microenvironment would lead to a controlled release of angiogenic proteins promoting vascularization, simultaneously offering structural support for new matrix deposition. Two non-viral vectors, chitosan (Ch) and polyethyleneimine (PEI), were tested to deliver plasmids encoding for vascular endothelial growth factor (pVEGF) and fibroblast growth factor-2 (pFGF2) to human dermal fibroblasts (hDFbs). hDFbs were successfully transfected with both Ch and PEI, without compromising the metabolic activity. Despite low transfection efficiency, superior VEGF and FGF-2 transgene expression was attained when pVEGF was delivered with PEI and when pFGF2 was delivered with Ch, impacting the formation of capillary-like structures by primary human dermal microvascular endothelial cells (hDMECs). Moreover, in a 3D microenvironment, when PEI-pVEGF and Ch-FGF2 were delivered to hDFbs, cells produced functional pro-angiogenic proteins which induced faster formation of capillary-like structures that were retained in vitro for longer time in a Matrigel assay. The dual combination of the plasmids resulted in a downregulation of the production of VEGF and an upregulation of FGF-2. The number of capillary-like segments obtained with this system was inferior to the delivery of plasmids individually but superior to what was observed with the non-transfected cells. This work confirmed that cell-laden scaffolds containing transfected cells offer a novel, selective and alternative approach to impact the vascularization during tissue regeneration. Moreover, this work provides a new platform for pathophysiology studies, models of disease, culture systems and drug screening.

Externally triggered release of growth factors - A tissue regeneration approach

Tissue regeneration aims to achieve functional restoration following injury by creating an environment to enable the body to self-repair. Strategies for regeneration rely on the introduction of biomaterial scaffolding, cells and bioactive molecules into the body, at or near the injury site. Of these bioactive molecules, growth factors (GFs) play a pivotal role in directing regenerative pathways for many cell populations. However, the therapeutic use of GFs has been limited by the complexity of biological injury and repair, and the properties of the GFs themselves, including their short half-life, poor tissue penetration, and off-target side effects. Externally triggered delivery systems have the potential to facilitate the delivery of GFs into the target tissues with considerations of the timing, sequence, amount, and location of GF presentation. This review briefly discusses the challenges facing the therapeutic use of GFs, then, we discuss approaches to externally trigger GF release from delivery systems categorised by stimulation type; ultrasound, temperature, light, magnetic fields and electric fields. Overall, while the use of GFs for tissue regeneration is still in its infancy, externally controlled GF delivery technologies have the potential to achieve robust and effective solutions to present GFs to injured tissues. Future technological developments must occur in conjunction with a comprehensive understanding of the biology at the injury site to ensure translation of promising technologies into real world benefit.

Injectable, self-healing and pH responsive stem cell factor loaded collagen hydrogel as a dynamic bioadhesive dressing for diabetic wound repair

As one of the serious complications of diabetes, diabetic ulcers induce several clinical problems. Although a variety of wound dressings are commonly employed, their role is too simple to integrate wound adaptation, therapeutics and effectiveness. To meet this comprehensive need, an injectable hydrogel (Col/APG) consisting of collagen and polyethylene glycol was prepared and loaded with umbilical cord stem cell factor (SCF) for the treatment of diabetic wounds. The physico-chemical properties of the Col/APG hydrogel, including rheology, self-shaping and self-healing, were demonstrated to adapt to the wound. After loading with the SCF, the adhesion strength of the resulting Col/APG + SCF hydrogel was enhanced to 17 kPa and it also showed favorable biocompatibility. A rapid cellular response, sufficient collagen deposition and marked neovascularization were observed in the whole cortex defect model of a diabetic rat after the Col/APG + SCF hydrogel was applied. Additionally, the skew toward M2 macrophages, credited with providing the anti-inflammatory function, also existed in both hydrogel groups. These findings suggested that the Col/APG hydrogel is a desirable scaffold and the Col/APG hydrogel loaded stem cell factor as a dressing is a promising treatment for diabetic tissue regeneration.

Intracerebroventricular delivery of vascular endothelial growth factor in patients with amyotrophic lateral sclerosis, a phase I study

We studied the feasibility, safety, tolerability and pharmacokinetics of intracerebroventricular delivery of recombinant human vascular endothelial growth factor in patients with amyotrophic lateral sclerosis. In this phase I study in patients with amyotrophic lateral sclerosis, the study drug was delivered using an implantable programmable pump connected to a catheter inserted in the frontal horn of the lateral cerebral ventricle. A first cohort received open label vascular endothelial growth factor (0.2, 0.8 and 2 µg/day), a second cohort received placebo, 0.8 or 2 µg/day of study dug. After the 3-month study period, all patients could participate in an open label extension study. In total, 18 patients with amyotrophic lateral sclerosis, seen at the University Hospitals in Leuven were included. The surgical procedure was well tolerated in most patients. One patient had transient postoperative seizures, due to an ischemic lesion along the catheter tract. The first 3-month study period was completed by 15/18 patients. Administration of 2 µg/day vascular endothelial growth factor resulted in sustained detectable levels in cerebrospinal fluid. A pulmonary embolus occurred in 3 patients, in 1 patient in the first 3-month study, and in 2 patients during the open label extension study. The study drug was well tolerated in the other patients, for up to 6 years in the open label extension study. Our study shows that intracerebroventricular administration of 2 µg/day of vascular endothelial growth factor to patients with amyotrophic lateral sclerosis is feasible, results in detectable cerebrospinal fluid levels and is well tolerated in most patients. The most common serious adverse event was a pulmonary embolus.

Model-Based Analysis Reveals a Sustained and Dose-Dependent Acceleration of Wound Healing by VEGF-A mRNA (AZD8601)

Intradermal delivery of AZD8601, an mRNA designed to produce vascular endothelial growth factor A (VEGF‐A), has previously been shown to accelerate cutaneous wound healing in a murine diabetic model. Here, we develop population pharmacokinetic and pharmacodynamic models aiming to quantify the effect of AZD8601 injections on the dynamics of wound healing. A dataset of 584 open wound area measurements from 131 mice was integrated from 3 independent studies encompassing different doses, dosing timepoints, and number of doses. Evaluation of several candidate models showed that wound healing acceleration is not likely driven directly by time‐dependent VEGF‐A concentration. Instead, we found that administration of AZD8601 induced a sustained acceleration of wound healing depending on the accumulated dose, with a dose producing 50% of the maximal effect of 92 µg. Simulations with this model showed that a single dose of 200 µg AZD8601 can reduce the time to reach 50% wound healing by up to 5 days.

Nanoparticle-Based Therapeutic Approach for Diabetic Wound Healing

Diabetes mellitus (DM) is a common endocrine disease characterized by a state of hyperglycemia (higher level of glucose in the blood than usual). DM and its complications can lead to diabetic foot ulcer (DFU). DFU is associated with impaired wound healing, due to inappropriate cellular and cytokines response, infection, poor vascularization, and neuropathy. Effective therapeutic strategies for the management of impaired wound could be attained through a better insight of molecular mechanism and pathophysiology of diabetic wound healing. Nanotherapeutics-based agents engineered within 1-100 nm levels, which include nanoparticles and nanoscaffolds, are recent promising treatment strategies for accelerating diabetic wound healing. Nanoparticles are smaller in size and have high surface area to volume ratio that increases the likelihood of biological interaction and penetration at wound site. They are ideal for topical delivery of drugs in a sustained manner, eliciting cell-to-cell interactions, cell proliferation, vascularization, cell signaling, and elaboration of biomolecules necessary for effective wound healing. Furthermore, nanoparticles have the ability to deliver one or more therapeutic drug molecules, such as growth factors, nucleic acids, antibiotics, and antioxidants, which can be released in a sustained manner within the target tissue. This review focuses on recent approaches in the development of nanoparticle-based therapeutics for enhancing diabetic wound healing.

An Overview of Ozone Therapy for Treating Foot Ulcers in Patients With Diabetes

Diabetic foot ulcer (DFU) is one of the most common and severe complications of diabetes mellitus, which is becoming increasingly prevalent throughout the world, with high mortality and morbidity. Because of the complex pathophysiological processes involved, DFU is difficult to treat effectively with traditional therapies. Ozone therapy, an emerging method, has been reported as potentially beneficial for closure of DFUs and may gradually move to the forefront of clinical practice. Possible mechanisms of action include antioxidant capacity, pathogen inactivation, vascular and endogenous growth factor modulation, and immune system activation. However, some researchers are skeptical about its safety, and clinical trials are lacking. This article reviews the current research and application of ozone therapy for DFUs.

Orf Virus IL-10 and VEGF-E Act Synergistically to Enhance Healing of Cutaneous Wounds in Mice

Orf virus (OV) is a zoonotic parapoxvirus that causes highly proliferative skin lesions which resolve with minimal inflammation and scarring. OV encodes two immunomodulators, vascular endothelial growth factor (VEGF)-E and interleukin-10 (ovIL-10), which individually modulate skin repair and inflammation. This study examined the effects of the VEGF-E and ovIL-10 combination on healing processes in a murine wound model. Treatments with viral proteins, individually and in combination, were compared to a mammalian VEGF-A and IL-10 combination. Wound biopsies were harvested to measure re-epithelialisation and scarring (histology), inflammation, fibrosis and angiogenesis (immunofluorescence), and gene expression (quantitative polymerase chain reaction). VEGF-E and ovIL-10 showed additive effects on wound closure and re-epithelialisation, and suppressed M1 macrophage and myofibroblast infiltration, while allowing M2 macrophage recruitment. The viral combination also increased endothelial cell density and pericyte coverage, and improved collagen deposition while reducing the scar area. The mammalian combination showed equivalent effects on wound closure, re-epithelialisation and fibrosis, but did not promote blood vessel stabilisation or collagen remodeling. The combination treatments also differentially altered the expression of transforming growth factor beta isoforms, Tgfβ1 and Tgfβ3. These findings show that the OV proteins synergistically enhance skin repair, and act in a complimentary fashion to improve scar quality.

Stammzellen in der Regenerativen Medizin – Translationale Hürden und Möglichkeiten zur Überwindung

Der Einsatz von mesenchymalen Stammzellen in der regenerativen Medizin wird immer populärer. Nichtsdestotrotz ist ihre Anwendung im klinischen Alltag noch immer limitiert. Zahlreiche ethische, rechtliche und translationale Probleme sowie Ungewissheit bzgl. der Sicherheit hemmen noch immer die Entstehung von entsprechenden Therapien aus vielversprechenden wissenschaftlichen Ansätzen.

Diese Arbeit soll die Hauptprobleme bei der Translation von stammzellbasierten Therapien aus der Grundlagenforschung und Präklinik in den klinischen Alltag darstellen, sowie Ansätze aufzeigen, diese zu überwinden.

Deriving Immune Modulating Drugs from Viruses-A New Class of Biologics

Viruses are widely used as a platform for the production of therapeutics. Vaccines containing live, dead and components of viruses, gene therapy vectors and oncolytic viruses are key examples of clinically-approved therapeutic uses for viruses. Despite this, the use of virus-derived proteins as natural sources for immune modulators remains in the early stages of development. Viruses have evolved complex, highly effective approaches for immune evasion. Originally developed for protection against host immune responses, viral immune-modulating proteins are extraordinarily potent, often functioning at picomolar concentrations. These complex viral intracellular parasites have "performed the R&D", developing highly effective immune evasive strategies over millions of years. These proteins provide a new and natural source for immune-modulating therapeutics, similar in many ways to penicillin being developed from mold or streptokinase from bacteria. Virus-derived serine proteinase inhibitors (serpins), chemokine modulating proteins, complement control, inflammasome inhibition, growth factors (e.g., viral vascular endothelial growth factor) and cytokine mimics (e.g., viral interleukin 10) and/or inhibitors (e.g., tumor necrosis factor) have now been identified that target central immunological response pathways. We review here current development of virus-derived immune-modulating biologics with efficacy demonstrated in pre-clinical or clinical studies, focusing on pox and herpesviruses-derived immune-modulating therapeutics.

Cell-modified bioprinted microspheres for vascular regeneration

Cell therapy is a promising strategy in which living cells or cellular materials are delivered to treat a variety of diseases. Here, we developed an electrospray bioprinting method to rapidly generate cell-laden hydrogel microspheres, which limit the migration of the captured cells and provide an immunologically privileged microenvironment for cell survival in vivo. Currently, therapeutic angiogenesis aims to induce collateral vessel formation after limb ischemia. However, the clinical application of gene and cell therapy has been impeded by concerns regarding its inefficacy, as well as the associated risk of immunogenicity and oncogenicity. In this study, hydrogel microspheres encapsulating VEGF-overexpressing HEK293T cells showed good safety via subcutaneously injecting into male C57BL/6 mice. In addition, these cell-modified microspheres effectively promoted angiogenesis in a mouse hind-limb ischemia model. Therefore, we demonstrated the great therapeutic potential of this approach to induce angiogenesis in limb ischemia, indicating that bioprinting has a bright future in cell therapy.

Visible light mediated PVA-tyramine hydrogels for covalent incorporation and tailorable release of functional growth factors

PVA-Tyr hydrogel facilitated covalent incorporation can control release of pristine growth factors while retaining their native bioactivity.

The Role of Recombinant Proteins and Growth Factors in the Management of Diabetic Foot Ulcers: A Systematic Review of Randomized Controlled Trials

BACKGROUND

Recombinant proteins and growth factors are emerging therapies for diabetic foot ulcers. Despite several clinical reports, there has been no comprehensive and systematic assessment of the totality of clinical evidence on the efficacy and safety of recombinant proteins and growth factors in diabetic foot ulcers. We tried to address this gap through an updated systematic review of randomized controlled trials (RCTs).

METHODS

PubMed, the Cochrane Library, Scopus, Embase, and Google Scholar databases were searched, and RCTs on the efficacy of recombinant proteins and growth factors in the treatment of cutaneous wounds in diabetic patients were selected. The literature search and assessment were performed by two independent reviewers. Methodological quality of studies was appraised using the Jadad scale.

RESULTS

We identified 26 RCTs involving diabetic patients with ulcer that evaluated the effectiveness of platelet-derived growth factor, epidermal growth factor, fibroblast growth factor, granulocyte colony-stimulating factor, vascular endothelial growth factor, erythropoietin, transforming growth factor, talactoferrin, and rusalatide acetate. The main primary outcome was complete healing though different indices were employed to define this such as wound closure, granulation tissue formation, or complete reepithelialization. Few studies had a follow-up period to report any recurrence and amputation rate. No adverse effect was reported due to the intervention.

CONCLUSION

Overall, there is a greater agreement on the effectiveness of EGF to enhance the healing of diabetic ulcers. Nevertheless, extant evidence is lacking for other agents since few trials have been conducted for most of the growth factors and available studies are heterogeneous in their methodologies.

Prospects for the application of growth factors in wound healing

As the largest organ of the body, human skin is multifunctional and enjoys two layers, the epidermis and the dermis, the separation of which is performed by a basement membrane zone. Skin protects the body against mechanical forces and infections. Skin wounds represent large and growing challenges to the healthcare systems globally. Skin wound healing, as a protective shield for the body against the external environment, includes interactions among cell types, the neurovascular system, cytokines, and matrix remodeling. Growth factors (GFs) affect the microenvironment of the wound, and cause rises in cell differentiation, proliferation, and migration. Administrating exogenous GFs has revealed potential in enhancing wound healing outcomes. The use of human GFs in the field of wound healing is becoming gradually more interesting, because of the low-invasive techniques required for their use. Reviewed here are the literatures on the healing of skin wounds with emphasize on the role of GFs and their future prospects, containing profits, and probable long-standing side effects accompanied with their use.

Biodegradable Mesoporous Silica Nanocarrier Bearing Angiogenic QK Peptide and Dexamethasone for Accelerating Angiogenesis in Bone Regeneration

In the repair of large segmental bone defects, bone tissue is often unable to heal due to the destruction of the vascular network near the wound site. An ideal bone repair material should have both angiogenic and osteogenic capabilities. To achieve this goal, we used biodegradable mesoporous silica nanoparticles (MSNs) as a delivery vehicle for dexamethasone (DEX), a small-molecule drug that induces osteogenic differentiation. Subsequently, chitosan was covalently modified onto the surface of the nanoparticles by glycidoxypropyltrimethoxysilane (GPTMS) to construct nanoparticulate delivery systems (DEX@chi-MSNs) that induce osteoblast formation. The QK peptide, which mimics the α-helical structure of vascular endothelial growth factor (VEGF) binding to the receptor, was adsorbed to the surface of chitosan-modified MSNs nanoparticles (QK@chi-MSNs) to render them with angiogenic ability. The QK@chi-MSNs can promote the formation of the tubular structure of human umbilical vein endothelial cells (HUVECs) and angiogenesis in vivo, as demonstrated by a chicken embryo chorioallantoic test (CAM) and subcutaneous embedding test. The DEX@chi-MSNs can improve alkaline phosphatase (ALP) activity, mineralized nodule formation, and the expression of osteogenic-related genes and proteins by BMSCs. Furthermore, the ability of bone repair and angiogenesis was evaluated in a critical size skull defect model in rats by using nanocarriers loaded with both DEX and QK (QK/DEX@chi-MSNs). The results of computed tomography (CT) scan, histological examination, and immunofluorescence staining indicated that QK/DEX@chi-MSNs can promote bone formation and angiogenesis in vivo, which has broad application prospects in bone tissue engineering.

Growth factors with enhanced syndecan binding generate tonic signalling and promote tissue healing

Growth factors can stimulate tissue regeneration, but the side effects and low effectiveness associated with suboptimal delivery systems have impeded their use in translational regenerative medicine. Physiologically, growth factor interactions with the extracellular matrix control their bioavailability and spatiotemporal cellular signalling. Growth factor signalling is also controlled at the cell surface level via binding to heparan sulfate proteoglycans, such as syndecans. Here we show that vascular endothelial growth factor-A (VEGF-A) and platelet-derived growth factor-BB (PDGF-BB) that were engineered to have a syndecan-binding sequence trigger sustained low-intensity signalling (tonic signalling) and reduce the desensitization of growth factor receptors. We also show in mouse models that tonic signalling leads to superior morphogenetic activity, with syndecan-binding growth factors inducing greater bone regeneration and wound repair than wild-type growth factors, as well as reduced tumour growth (associated with PDGF-BB delivery) and vascular permeability (triggered by VEGF-A). Tonic signalling via syndecan binding may also enhance the regenerative capacity of other growth factors.

Antimicrobial action of autologous platelet-rich plasma on MRSA-infected skin wounds in dogs

Effective antimicrobial preparations, other than antibiotics, are important for the treatment of potentially fatal drug-resistant infections. Methicillin-resistant Staphylococcus aureus (MRSA) is one of the leading causes of hospital-acquired and post- operative infections. Fortunately, the antimicrobial properties of platelet-rich plasma (PRP) against various microorganisms enable its potential use as an alternative to conventional antibiotics. The present work was designed to evaluate the hypothesized antimicrobial activity of PRP against MRSA infected skin wounds. Six adult male dogs were divided equally into control and PRP groups. Unilateral circular full-thickness skin wounds were created then a MRSA suspension was injected locally. Treatment started at 1st week post infection with subcutaneous infiltration of autologous activated PRP every week in the PRP group and with topical application of clindamycin cream twice daily in the control group. PRP decreased wound size and significantly increased wound contractility and re-epithelization, as confirmed by histopathological and immunohistochemical findings. Also PRP treated group showed significant decrease in ROS and redox imbalance with over expression of the TNF-α and VEGFA genes that indicate angiogenesis and maximum antibacterial activity after three weeks. In conclusion, CaCl₂-activated PRP exhibited antimicrobial activity against MRSA infection, which improved the infected wound healing re-epithelization and granulation tissue formation.

Drug therapies and delivery mechanisms to treat perturbed skin wound healing

Acute wound healing is an orderly process of four overlapping events: haemostasis, inflammation, proliferation and remodelling. A drug delivery system with a temporal control of release could promote each of these events sequentially. However, acute wound healing normally proceeds very well in healthy individuals and there is little need to promote it. In the elderly and diabetics however, healing is often slow and wounds can become chronic and we need to promote their healing. Targeting the events of acute wound healing would not be appropriate for a chronic wound, which have stalled in the proinflammatory phase. They also have many additional problems such as poor circulation, low oxygen, high levels of leukocytes, high reactive oxygen species, high levels of proteolytic enzymes, high levels of proinflammatory cytokines, bacterial infection and high pH. The future challenge will be to tackle each of these negative factors to create a wound environment conducive to healing.

Adipokine concentrations in lipoaspirates may have a role in wound healing

OBJECTIVES

In addition to its use as a volume filler, fat grafting may have a potential role in wound healing based on the concentration of growth factors in the lipoaspirate. In this study, we compare the quantitative and qualitative concentration of the various growth factors and adipokines using the Shippert or the Coleman techniques to prepare the lipoaspirate.

METHODS

We measured leptin, adiponectin and the growth factors, i.e., acidic fibroblast growth factor (aFGF), basic FGF (bFGF), keratinocyte growth factor (KGF), bone morphogenetic protein-2 (BMP-2) and vascular endothelial growth factor (VEGF) by ELISA in solid and liquid fractions obtained with both techniques in human fat obtained with Coleman technique and Shippert technique.

RESULTS

All of these peptides, except BMP-2, were detected in relevant quantities in the solid fraction. The Coleman but not the Shippert technique resulted in statistically higher adiponectin concentrations in the solid tissue fraction. The other four growth factors occurred in significantly higher concentrations in the solid fractions compared to the liquid fractions, independent of the processing technique.

CONCLUSION

In summary, we demonstrated that KGF, aFGF, bFGF and VEGF, as well as leptin and adiponectin, are contained in fat suspensions obtained by liposuction and in the supernatant. Only the concentration of adiponectin was in the range reported to contribute to wound healing.

Predictive Approach Identifies Molecular Targets and Interventions to Restore Angiogenesis in Wounds With Delayed Healing

Impaired angiogenesis is a hallmark of wounds with delayed healing, and currently used therapies to restore angiogenesis have limited efficacy. Here, we employ a computational simulation-based approach to identify influential molecular and cellular processes, as well as protein targets, whose modulation may stimulate angiogenesis in wounds. We developed a mathematical model that captures the time courses for platelets, 9 cell types, 29 proteins, and oxygen, which are involved in inflammation, proliferation, and angiogenesis during wound healing. We validated our model using previously published experimental data. By performing global sensitivity analysis on thousands of simulated wound-healing scenarios, we identified six processes (among the 133 modeled in total) whose modulation may improve angiogenesis in wounds. By simulating knockouts of 25 modeled proteins and by simulating different wound-oxygenation levels, we identified four proteins [namely, transforming growth factor (TGF)-β, vascular endothelial growth factor (VEGF), fibroblast growth factor-2 (FGF-2), and angiopoietin-2 (ANG-2)], as well as oxygen, as therapeutic targets for stimulating angiogenesis in wounds. Our modeling results indicated that simultaneous inhibition of TGF-β and supplementation of either FGF-2 or ANG-2 could be more effective in stimulating wound angiogenesis than the modulation of either protein alone. Our findings suggest experimentally testable intervention strategies to restore angiogenesis in wounds with delayed healing.

Advances in surgical applications of growth factors for wound healing

Growth factors have recently gained clinical importance for wound management. Application of recombinant growth factors has been shown to mimic cell migration, proliferation, and differentiation in vivo, allowing for external modulation of the healing process. Perioperative drug delivery systems can enhance the biological activity of these growth factors, which have a very short in vivo half-life after topical administration. Although the basic mechanisms of these growth factors are well understood, most have yet to demonstrate a significant impact in animal studies or small-sized clinical trials. In this review, we emphasized currently approved growth factor therapies, including a sustained release system for growth factors, emerging therapies, and future research possibilities combined with surgical procedures. Approaches seeking to understand wound healing at a systemic level are currently ongoing. However, further research and consideration in surgery will be needed to provide definitive confirmation of the efficacy of growth factor therapies for intractable wounds.

Skin tissue regeneration for burn injury

The skin is the largest organ of the body, which meets the environment most directly. Thus, the skin is vulnerable to various damages, particularly burn injury. Skin wound healing is a serious interaction between cell types, cytokines, mediators, the neurovascular system, and matrix remodeling. Tissue regeneration technology remarkably enhances skin repair via re-epidermalization, epidermal-stromal cell interactions, angiogenesis, and inhabitation of hypertrophic scars and keloids. The success rates of skin healing for burn injuries have significantly increased with the use of various skin substitutes. In this review, we discuss skin replacement with cells, growth factors, scaffolds, or cell-seeded scaffolds for skin tissue reconstruction and also compare the high efficacy and cost-effectiveness of each therapy. We describe the essentials, achievements, and challenges of cell-based therapy in reducing scar formation and improving burn injury treatment.

Cytokines and Growth Factors

Several cytokines have been used to treat autoimmune diseases, viral infections, and cancer and to regenerate the skin. In particular, interferons (INFs) have been used to treat cancer, hepatitis B and C, and multiple sclerosis, while interleukins (ILs) and tumor necrosis factors (TNFs) have been used in the management of different types of cancer. Concerning the hematopoietic growth factors (HGFs), epoetin has been used for anemia, whereas the colony-stimulating factors (CSFs) have been used for neutropenia. Other growth factors have been extensively explored, although most still need to demonstrate in vivo clinical relevance before reaching the market.This chapter provides an overview on the therapeutic applications of biological medicines containing recombinant cytokines and growth factors (HGFs and others). From this review, we concluded that the clinical relevance of recombinant cytokines has been increasing. Since the 1980s, the European Medicines Agency (EMA) and/or Food and Drug Administration (FDA) have approved 89 biological medicines containing recombinant cytokines. Among these, 18 were withdrawn, 24 are biosimilars, and 18 are orphans.So far, considerable progress has been made in discovering new cytokines, additional cytokine functions, and how they interfere with human diseases. Future prospects include the approval of more biological and biosimilar medicines for different therapeutic applications.

Modified VEGF-A mRNA induces sustained multifaceted microvascular response and accelerates diabetic wound healing

Capable of mediating efficient transfection and protein production without eliciting innate immune responses, chemically modified mRNA holds great potential to produce paracrine factors at a physiologically beneficial level, in a spatiotemporally controlled manner, and with low toxicity. Although highly promising in cardiovascular medicine and wound healing, effects of this emerging therapeutic on the microvasculature and its bioactivity in disease settings remain poorly understood. Here, we longitudinally and comprehensively characterize microvascular responses to AZD8601, a modified mRNA encoding vascular endothelial growth factor A (VEGF-A), in vivo. Using multi-parametric photoacoustic microscopy, we show that intradermal injection of AZD8601 formulated in a biocompatible vehicle results in pronounced, sustained and dose-dependent vasodilation, blood flow upregulation, and neovessel formation, in striking contrast to those induced by recombinant human VEGF-A protein, a non-translatable variant of AZD8601, and citrate/saline vehicle. Moreover, we evaluate the bioactivity of AZD8601 in a mouse model of diabetic wound healing in vivo. Using a boron nanoparticle-based tissue oxygen sensor, we show that sequential dosing of AZD8601 improves vascularization and tissue oxygenation of the wound bed, leading to accelerated re-epithelialization during the early phase of diabetic wound healing.