Cause Of Impaired Wound Healing Research Articles

A multilayer hydrogel incorporating urolithin B promotes diabetic wound healing via ROS scavenging and angiogenesis

Impaired wound healing is one of the most prevalent complications associated with diabetes. Reactive oxygen species (ROS) and subsequent endothelial dysfunction are the primary causes of impaired wound healing in patients with diabetes. One of the metabolites of ellagitannins in gut microbiota, urolithin B (UB), has attracted increasing research interest due to its ability to scavenge ROS and exert anti-inflammatory effects. However, the role and molecular mechanisms of UB in diabetic wound healing have not yet been elucidated. We found that UB mitigated oxidative stress and cell senescence induced by tert-butyl hydroperoxide stimulation and restored angiogenesis in human umbilical vein endothelial cells (HUVECs) through the activation of the nuclear factor erythroid derived 2-related factor 2 (NRF2)/heme oxygenase 1 (HO-1) pathway. Furthermore, a novel multilayer ROS-responsive hydrogel was designed and loaded with UB (MRRH@UB) to promote wound healing in diabetic wounds. This composite hydrogel exhibited excellent biocompatibility, robust mechanical properties and strong antioxidative activity. Additionally, by serving as a carrier, it facilitates the controlled and sustained release of UB, synergistically enhancing antioxidant stress. The in vivo and in vitro results demonstrate that MRRH@UB exhibits remarkable antioxidant and anti-senescence properties, promotes neovascularization, and enhances wound healing. Consequently, this composite hydrogel holds tremendous clinical potential for the treatment of chronic diabetic wounds.

Eradication of Mature Bacterial Biofilms with Concurrent Improvement in Chronic Wound Healing Using Silver Nanoparticle Hydrogel Treatment.

Biofilm-associated infections are a major cause of impaired wound healing. Despite the broad spectrum of anti-bacterial benefits provided by silver nanoparticles (AgNPs), these materials still cause controversy due to cytotoxicity and a lack of efficacy against mature biofilms. Herein, highly potent ultrasmall AgNPs were combined with a biocompatible hydrogel with integrated synergistic functionalities to facilitate elimination of clinically relevant mature biofilms in-vivo combined with improved wound healing capacity. The delivery platform showed a superior release mechanism, reflected by high biocompatibility, hemocompatibility, and extended antibacterial efficacy. In vivo studies using the S. aureus wound biofilm model showed that the AgNP hydrogel (200 µg/g) was highly effective in eliminating biofilm infection and promoting wound repair compared to the controls, including silver sulfadiazine (Ag SD). Treatment of infected wounds with the AgNP hydrogel resulted in faster wound closure (46% closure compared to 20% for Ag SD) and accelerated wound re-epithelization (60% for AgNP), as well as improved early collagen deposition. The AgNP hydrogel did not show any toxicity to tissue and/or organs. These findings suggest that the developed AgNP hydrogel has the potential to be a safe wound treatment capable of eliminating infection and providing a safe yet effective strategy for the treatment of infected wounds.

Antioxidant and anti-inflammatory activities of Prussian blue nanozyme promotes full-thickness skin wound healing

Excessive reactive oxygen species (ROS) and unresolved inflammations are the major causes of impaired wound healing as they overwhelm the cellular antioxidant system and impede the healing process. In this study, we examined the application of Prussian blue (PB) nanozyme as a novel material for cutaneous wound healing through the alleviation of excessive ROS and inflammation modulation. The PB nanoparticles not only exhibited hydrogen peroxide (H2O2) degradation activity but also showed strong superoxide scavenging ability. PB nanozyme mitigated the intracellular ROS at a high oxidative stress environment, resulting in a pronounced cytoprotective effect. Moreover, PB nanozyme also displayed significant anti-inflammatory activity, as evident from the suppression of inflammatory mediators in the lipopolysaccharide (LPS) induced macrophage cells. Encouraged by the in vitro results, we evaluated the in vivo therapeutic efficacy of PB nanozyme in a full-thickness cutaneous wound model combined with LPS treatment to mimic bacterial infection. The beneficial effects of topically applied PB nanozyme on wound healing and tissue regeneration were evident compared to the control. The periodical administration of a low amount (50 μg × 4) of PB nanoparticles exhibited faster wound closure as well as collagen deposition, maturation, and organization. Moreover, the PB treatment effectively induced the differentiation of keratinocytes, enhanced the neovascularization, and reduced macrophage burden in the entire wound site. Thus, PB nanozyme not only accelerated the healing process in an infection-mimicking cutaneous wound model but also exhibited tissue regeneration characteristics owing to the synergistic effect of ROS-scavenging and anti-inflammatory activities.

Topical Alpha-Gal Nanoparticles Enhances Wound Healing in Radiated Tissue

BACKGROUND: Radiation is a common primary, adjuvant, and neoadjuvant therapy in oncologic patients. It is well known that surgery on radiated tissues is associated with significantly higher complication rates due to permanently compromised wound healing. It is thought that one cause of impaired wound healing is the aberrant inflammatory response that occurs in radiated tissues. Previous work has demonstrated that the topical application of naturally occurring antigen α-gal (Galα1-3Galb1-[3]4GlcNAc-R) nanoparticles (AGNs) onto wound surface accelerates macrophage recruitment. As we have already observed accelerated wound healing in both normal and diabetic wounds treated with topical AGN, we hypothesized that application of this natural antigen would similarly enhance healing of the wounds in irradiated tissue. METHODS: To simulate human physiology, α-1,3galactosyltransferase knockout mice (KO), which do not produce the antigen and therefore can be stimulated to produce antibodies against it, were used. KO were exposed to the antigen to produce anti α-gal antibodies at titers comparable to those seen in humans. Ten days before wounding, dorsal skin was isolated using a low-pressure clamp as previously described and was irradiated with one session of 40 Gy. Bilateral 6-mm dorsal splinted full-thickness wounds were created and treated with AGN in a 2% carboxymethyl cellulose carrier, immediately after wounding and again on postoperative day 1. Control knocked out group underwent similar irradiation and wounding protocols but were treated with phosphate buffered saline (PBS) in 2% carboxymethyl cellulose. Wild-type mice, which are indolent to the antigen, went through the same radiation and wounding to eliminate confounding factors other than immunogenic response to AGN. Wounds were harvested from all animals up to 21 days after the wounding for histologic and immunohistochemistry measures. The extent of keratinocyte migration, neovascularization, and macrophage recruitment was assessed. RESULTS: Full closure of all wounds by day 9 in the nonradiated control compared to no completely closed wounds in the radiated group confirmed the known inhibitory effects of irradiation on wound healing. In addition, histologic changes such as increased epidermal thickness in the skin surrounding the wound further confirmed the effects of irradiation on the skin. Histologic analysis demonstrated enhanced keratinocyte migration in the AGN-treated KO wounds, which was significantly improved in comparison to PBS-treated KO wounds noted by day 15 and until the end of the study (P < 0.01). On day 21, ≈63% of all α-gal–treated wounds were completely healed as opposed to only ≈17% in the PBS-treated group. In wild-type mice, treatment with AGN showed no improvement in keratinocyte migration or time to full closure. CONCLUSIONS: Topical application of AGN onto radiated wounds significantly ameliorate the delayed wound healing in radiated tissue resulting in faster wound closure. We believe that this naturally occurring agent has great promise for clinical translation as it has demonstrated efficacy in not only normal wounds but pathologic (diabetic, radiated) ones as well.

Spatio-temporal Models of Lymphangiogenesis in Wound Healing.

Several studies suggest that one possible cause of impaired wound healing is failed or insufficient lymphangiogenesis, that is the formation of new lymphatic capillaries. Although many mathematical models have been developed to describe the formation of blood capillaries (angiogenesis), very few have been proposed for the regeneration of the lymphatic network. Lymphangiogenesis is a markedly different process from angiogenesis, occurring at different times and in response to different chemical stimuli. Two main hypotheses have been proposed: (1) lymphatic capillaries sprout from existing interrupted ones at the edge of the wound in analogy to the blood angiogenesis case and (2) lymphatic endothelial cells first pool in the wound region following the lymph flow and then, once sufficiently populated, start to form a network. Here, we present two PDE models describing lymphangiogenesis according to these two different hypotheses. Further, we include the effect of advection due to interstitial flow and lymph flow coming from open capillaries. The variables represent different cell densities and growth factor concentrations, and where possible the parameters are estimated from biological data. The models are then solved numerically and the results are compared with the available biological literature.

Application of Electron Paramagnetic Resonance (EPR) Oximetry to Monitor Oxygen in Wounds in Diabetic Models

A lack of oxygen is classically described as a major cause of impaired wound healing in diabetic patients. Even if the role of oxygen in the wound healing process is well recognized, measurement of oxygen levels in a wound remains challenging. The purpose of the present study was to assess the value of electron paramagnetic resonance (EPR) oximetry to monitor pO2 in wounds during the healing process in diabetic mouse models. Kinetics of wound closure were carried out in streptozotocin (STZ)-treated and db/db mice. The pO2 was followed repeatedly during the healing process by 1 GHz EPR spectroscopy with lithium phthalocyanine (LiPc) crystals used as oxygen sensor in two different wound models: a full-thickness excisional skin wound and a pedicled skin flap. Wound closure kinetics were dramatically slower in 12-week-old db/db compared to control (db/+) mice, whereas kinetics were not statistically different in STZ-treated compared to control mice. At the center of excisional wounds, measurements were highly influenced by atmospheric oxygen early in the healing process. In pedicled flaps, hypoxia was observed early after wounding. While reoxygenation occurred over time in db/+ mice, hypoxia was prolonged in the diabetic db/db model. This observation was consistent with impaired healing and microangiopathies observed using intravital microscopy. In conclusion, EPR oximetry using LiPc crystals as the oxygen sensor is an appropriate technique to follow wound oxygenation in acute and chronic wounds, in normal and diabetic animals. Nevertheless, the technique is limited for measurements in pedicled skin flaps and cannot be applied to excisional wounds in which diffusion of atmospheric oxygen significantly affects the measurements.

A mathematical model for lymphangiogenesis in normal and diabetic wounds

Several studies suggest that one possible cause of impaired wound healing is failed or insufficient lymphangiogenesis, that is the formation of new lymphatic capillaries. Although many mathematical models have been developed to describe the formation of blood capillaries (angiogenesis) very few have been proposed for the regeneration of the lymphatic network. Moreover, lymphangiogenesis is markedly distinct from angiogenesis, occurring at different times and in a different manner. Here a model of five ordinary differential equations is presented to describe the formation of lymphatic capillaries following a skin wound. The variables represent different cell densities and growth factor concentrations, and where possible the parameters are estimated from experimental and clinical data. The system is then solved numerically and the results are compared with the available biological literature. Finally, a parameter sensitivity analysis of the model is taken as a starting point for suggesting new therapeutic approaches targeting the enhancement of lymphangiogenesis in diabetic wounds. The work provides a deeper understanding of the phenomenon in question, clarifying the main factors involved. In particular, the balance between TGF-β and VEGF levels, rather than their absolute values, is identified as crucial to effective lymphangiogenesis. In addition, the results indicate lowering the macrophage-mediated activation of TGF-β and increasing the basal lymphatic endothelial cell growth rate, inter alia, as potential treatments. It is hoped the findings of this paper may be considered in the development of future experiments investigating novel lymphangiogenic therapies.

Inhibition of Prostaglandin Transporter (PGT) Promotes Perfusion and Vascularization and Accelerates Wound Healing in Non-Diabetic and Diabetic Rats.

Peripheral ischemia, resulting from diminished arterial flow and defective local vascularization, is one of the main causes of impaired wound healing in diabetes. Vasodilatory prostaglandins (PGs), including PGE2 and PGI2, regulate blood flow in peripheral tissues. PGs also stimulate angiogenesis by inducing vascular endothelial growth factor. However, PG levels are reduced in diabetes mainly due to enhanced degradation. We hypothesized that inhibition of the prostaglandin transporter (PGT) (SLCO2A1), which mediates the degradation of PGs, would increase blood flow and stimulate vascularization, thereby mitigating peripheral ischemia and accelerating wound healing in diabetes. Here we report that inhibiting PGT with intravenously injected PGT inhibitor, T26A, increased blood flow in ischemic hind limbs created in non-diabetic rats and streptozotocin induced diabetic rats. Systemic, or combined with topical, T26A accelerated closure of cutaneous wounds. Immunohistochemical examination revealed that inhibition of PGT enhanced vascularization (marked by larger numbers of vessels formed by CD34+ cells), and accelerated re-epithelialization of cutaneous wounds. In cultured primary human bone marrow CD34+ cells and human epidermal keratinocytes (HEKs) either inhibiting or silencing PGT increased migration in both cell lines. Thus PGT directly regulates mobilization of endothelial progenitor cells (EPCs) and HEKs, which could contribute to PGT-mediated vascularization and re-epithelialization. At the molecular level, systemic inhibition of PGT raised circulating PGE2. Taken together, our data demonstrate that PGT modulates arterial blood flow, mobilization of EPCs and HEKs, and vascularization and epithelialization in wound healing by regulating vasodilatory and pro-angiogenic PGs.

Accelerated wound healing and anti-inflammatory effects of physically cross linked polyvinyl alcohol–chitosan hydrogel containing honey bee venom in diabetic rats

Diabetes is one of the leading causes of impaired wound healing. The objective of this study was to develop a bee venom-loaded wound dressing with an enhanced healing and anti-inflammatory effects to be examined in diabetic rats. Different preparations of polyvinyl alcohol (PVA), chitosan (Chit) hydrogel matrix-based wound dressing containing bee venom (BV) were developed using freeze-thawing method. The mechanical properties such as gel fraction, swelling ratio, tensile strength, percentage of elongation and surface pH were determined. The pharmacological activities including wound healing and anti-inflammatory effects in addition to primary skin irritation and microbial penetration tests were evaluated. Moreover, hydroxyproline, glutathione and IL-6 levels were measured in the wound tissues of diabetic rats. The bee venom-loaded wound dressing composed of 10 % PVA, 0.6 % Chit and 4 % BV was more swellable, flexible and elastic than other formulations. Pharmacologically, the bee venom-loaded wound dressing that has the same previous composition showed accelerated healing of wounds made in diabetic rats compared to the control. Moreover, this bee venom-loaded wound dressing exhibited anti-inflammatory effect that is comparable to that of diclofenac gel, the standard anti-inflammatory drug. Simultaneously, wound tissues covered with this preparation displayed higher hydroxyproline and glutathione levels and lower IL-6 levels compared to control. Thus, the bee venom-loaded hydrogel composed of 10 % PVA, 0.6 % Chit and 4 % BV is a promising wound dressing with excellent forming and enhanced wound healing as well as anti-inflammatory activities.

Evaluating the Effect of the Different Diabetic Control's Methods Including Tight Control on the Healing Response of Diabetic Foot Ulcer Treated with Low Level Laser Therapy (LLLT)

INTRODUCTION: Low-level laser therapy (LLLT) is shown effective in healing diabetic foot ulcer when combined with conventional therapy. Since; Diabetes mellitus is a leading cause of impaired wound healing. The aim of this study is to determine the effect of different diabetic control’s methods on the healing response of diabetic foot ulcer in those patients treated with Low level laser therapy (LLLT), added to conventional therapy.METHODS: This study contains 74 diabetic foot-ulcers which most of them prone to resistance to conventional therapy. Different stages of diabetic foot ulcers and ways of controlling blood glucose level are included in this study. There were 3 response groups; Group 1-Insulin receiving patients, most of them had a very tight blood glyceamic level profile controlling. Group 2- Non-insulin receiving or drug dependent patients, had a periodical blood glyceamic level profile with flatuance. Group 3- Mixed methods. Most of the patients in this group had tight blood glyceamic level profile controlling. The way to control blood glucose level should be according to the internist`s consult. The wounds irradiation are performed by the combination of infra-red and red, (860 nm and 650 nm) laser, with the total energy density of 3.6 J/cm² in addition of intravenous laser therapy (IVL) with 2.5 MW, 650 nm (red) laser used for 30 minutes. All wounds have been photographed from equal distance, before and after treatments, and all the wounds were staged by a surgeon who was neutral about the effects of the laser therapy. The surgeon’s judgment was established only by the visual assessments of the wounds. All the mathematical and statistical analysis is based on the descriptive statistics using the software package SPSS16.CONCLUSION: LLLT promote the tissue repair process of diabetic foot ulcer. Healing response of the patients was not dependent on methods of controlling blood glucose level. Previously it was reported that tight control of diabetes containing continuous subcutaneous insulin infusion and others on split mixed doses promotes healing of diabetic foot lesions. In this study; we found interruption of LLLT in the treatment of diabetic wound; can give a very acceptable result even in the absence of tight controlling of glucose level. When the quantity presentations value of the mean blood glucose level distribution was on the range of 144- 275 mg/dl. In this multi-disciplinary method we achieved a remarkably shorter mean healing time of two months, compared with other reported studies with healing time of three to six months.

Tight glycaemic control is a key factor in wound healing enhancement strategies in an experimental diabetes mellitus model

Diabetes mellitus is a leading cause of impaired wound healing. The aim of this study was to establish a glucose-controlled diabetic wound healing model. Sprague-Dawley rats were divided into three groups: Control group (C), Diabetic Non-glucose Controlled group (DNC) and Diabetic glucose Controlled group (DC). Glucose control was achieved using Insulman Rapid (average daily glucose level <10 mmol/L). 18 Sprague-Dawley rats underwent a dorsal skin wound incision and 10 days later were killed. Fresh and fixed wound tensile strength, hydroxyproline and transforming growth factor beta-1 levels were improved in the DC group when compared to the DNC group. The quantity of fibroblasts present was similar in each group. This study demonstrates the impact that diabetes has on acute wound healing and suggests that wound modulating agents must be tested in both the tightly glucose-controlled as well as the poorly glucose-controlled diabetic animal models prior to proceeding with translational clinical studies.

Research of PDGF-BB Gel on the Wound Healing of Diabetic Rats and Its Pharmacodynamics

One of the leading causes of impaired wound healing is diabetes mellitus. In diabetic patients, a minor skin wound often leads to serious complications. Many experiments had demonstrated that the expression of platelet-derived growth factor (PDGF) and its receptor was decreased in wounds of healing-impaired diabetic mice, indicating that a certain expression level of PDGF is essential for normal repair. The diabetic rats was induced by a single i.p. injection of streptozotocin and a 1.8 cm diameter full-thickness wound was made on each side of the rat mid-back. Then the rats were randomly divided into five groups, with eight animals in each group as follows: blank control, vehicle control, 3.5 microg PDGF-BB/cm(2) treatment group, 7 microg PDGF-BB/cm(2) treatment group and 14 microg PDGF-BB/cm(2) treatment group for either 7 or 14 consecutive days after wounding. Re-epithelialization area was measured by computerized planimetry, percentage wound closure and percentage wound contraction was calculated, granulation tissue and collagen formation was assessed by Masson trichrome, cell proliferation (proliferating cell nuclear antigen staining) and angiogenesis (Factor VIII related antigen staining) was assessed by immunohistological methods. PDGF-BB treatment improved healing quality, enhanced angiogenesis, cell proliferation and epithelialization, and formed thicker and more highly organized collagen fiber deposition in full-thickness excisional wound of diabetic rats. The effects of topically applied PDGF-BB were dose-dependent. PDGF-BB is an important future clinical tool, particularly for stimulating soft tissue repair in patients with an impaired capacity for wound healing.

COMP-angiopoietin-1 promotes wound healing through enhanced angiogenesis, lymphangiogenesis, and blood flow in a diabetic mouse model.

Microvascular dysfunction is a major cause of impaired wound healing seen in diabetic patients. Therefore, reestablishment of structural and functional microvasculature could be beneficial to promote wound healing in these patients. Angiopoietin-1 (Ang1) is a specific growth factor functioning to generate a stable and functional vasculature through the Tie2 and Tie1 receptors. Here we determined the effectiveness of cartilage oligomeric matrix protein (COMP)-Ang1, a soluble, stable, and potent form of Ang1, on promotion of healing in cutaneous wounds of diabetic mice. An excisional full-thickness wound was made in the dorsal side of the tail of diabetic (db/db) mice, and mice were then treated systemically with adenovirus (Ade) encoding COMP-Ang1 or with control virus encoding beta-gal (Ade-beta-gal) or treated topically with recombinant COMP-Ang1 protein or BSA. Time course observations revealed that mice treated with Ade-COMP-Ang1 or COMP-Ang1 protein showed accelerated wound closure and epidermal and dermal regeneration, enhanced angiogenesis and lymphangiogenesis, and higher blood flow in the wound region compared with mice treated with control virus or BSA. COMP-Ang1 promotion of wound closure and angiogenesis was not dependent on endothelial nitric oxide synthase or inducible nitric oxide synthase alone. Taken together, these findings indicate that COMP-Ang1 can promote wound healing in diabetes through enhanced angiogenesis, lymphangiogenesis, and blood flow.

Effects of induction therapy on wound healing at bronchial anastomosis sites in rats.

Preoperative chemotherapy is frequently used for advanced lung cancer. As a valid alternative to pneumonectomy, bronchoplasty has the advantage of enabling lung parenchyma function to be preserved. The effects of antineoplastic agents on healing bronchial anastomosis remain unclear. We studied the effects of preoperative chemotherapy on wound healing in bronchial anastomoses and clarified causes of wound healing impairment in rats. In experiment I, at 3 days before surgery, rats were injected with cyclophosphamide, doxorubicin, and vincristine (CAV group) or cisplatin and etoposide (PVP treated rats). In experiment II, at 48 hrs before surgery, rats were treated with rabbit antirat macrophage serum and antirat monocyte chemoattractant protein-1 antibody to inhibit macrophage infiltration. On days 3, 5, and 7 after bronchus anastomosis, wound healing was assessed by examining bursting strength and hydroxyproline tissue content. CAV-treated rats showed significant impaired wound healing, marked severe leucopenia, and reduced macrophage infiltration. The PVP group showed no significant changes. In experiment II, rats exhibited inhibited macrophage infiltration, which is associated with significantly impaired of wound healing. Our study suggests that induction chemotherapy, associated with leukopenia in the early phase of wound healing, increases the risk of bronchial anastomosis leakage. Postoperative macrophage depletion is one of the most important causes of impaired wound healing.