Acceleration of wound healing in healing-impaired db/db mice with a photocrosslinkable chitosan hydrogel containing fibroblast growth factor-2

Application of ultraviolet light irradiation to a photocrosslinkable chitosan (Az-CH-LA) aqueous solution including fibroblast growth factor-2 (FGF-2) results within 30 seconds in an insoluble, flexible hydrogel. The FGF-2 molecules retained in the chitosan hydrogel remain biologically active and are released from the chitosan hydrogel upon in vivo biodegradation of the hydrogel. To evaluate the accelerating effect on wound healing of this hydrogel, full-thickness skin incisions were made in the backs of healing-impaired diabetic (db/db) mice and their normal (db/+) littermates. The mice were later killed, and histological sections of the wound were prepared. The degree of wound healing was evaluated using several histological parameters such as the rate of contraction, epithelialization, and tissue filling. Application of the chitosan hydrogel significantly advanced the rate of contraction on Days 0 to 2 in db/db and db/+ mice. Although the addition of FGF-2 into the chitosan hydrogel in db/+ mice had little effect, application of the chitosan hydrogel-containing FGF-2 further accelerated the adjusted tissue filling rate (Days 2 to 4 and Days 4 to 8) in db/db mice. Furthermore, the chitosan hydrogel-containing FGF-2 markedly increased the number of CD-34-positive vessels in the wound areas of db/db mice on Day 4. Thus, the application of chitosan hydrogel-containing FGF-2 onto a healing-impaired wound induces significant wound contraction and accelerates wound closure and healing.     

Inhibition of vascular prosthetic graft infection using a photocrosslinkable chitosan hydrogel

BACKGROUND: Despite improvements in surgical techniques and antimicrobial therapies, prosthetic aortic graft infections remain a clinical problem. It is well known that chitosan has strong antibacterial activities to a wide variety of bacteria including Staphylococcus aureus, epidermidis and Escherichia coli (E. coli). The antibacterial activity by adhering a photocrosslinkable chitosan hydrogel to Dacron grafts was investigated in vitro and in vivo using a rabbit model. MATERIALS AND METHODS: The photocrosslinkable chitosan hydrogel (50microl) coated grafts (3 x 2mm fragments) were evaluated on a resistance against E. coliin vitro. The graft infections in vivo were also initiated through implantation of a Dacron graft fragment into the infrarenal aorta of a rabbit, followed by a topical inoculation with 10(6) colony-forming units of E. coli. The graft infection was allowed to develop over the following 1 week. RESULTS: The photocrosslinkable chitosan hydrogel-coated grafts exhibited a resistance against E. coliin vitro. Furthermore, application of 0.1ml photocrosslinkable chitosan hydrogel on the Dacron implant in vivo substantially inhibited graft infection with E. coli. CONCLUSIONS: These preliminary results suggested the potential use of a photocrosslinkable chitosan hydrogel in directing graft infection prophylaxis.     

Development of a new chitosan hydrogel for wound dressing

Wound healing is a complex process involving an integrated response by many different cell types and growth factors in order to achieve rapid restoration of skin architecture and function. The present study evaluated the applicability of a chitosan hydrogel (CH) as a wound dressing. Scanning electron microscopy analysis was used to characterize CH morphology. Fibroblast cells isolated from rat skin were used to assess the cytotoxicity of the hydrogel. CH was able to promote cell adhesion and proliferation. Cell viability studies showed that the hydrogel and its degradation by-products are noncytotoxic. The evaluation of the applicability of CH in the treatment of dermal burns in Wistar rats was performed by induction of full-thickness transcutaneous dermal wounds. Wound healing was monitored through macroscopic and histological analysis. From macroscopic analysis, the wound beds of the animals treated with CH were considerably smaller than those of the controls. Histological analysis revealed lack of a reactive or a granulomatous inflammatory reaction in skin lesions with CH and the absence of pathological abnormalities in the organs obtained by necropsy, which supported the local and systemic histocompatibility of the biomaterial. The present results suggest that this biomaterial may aid the re-establishment of skin architecture.     

Acceleration of wound healing with topically applied deoxyribonucleosides.

HYPOTHESIS: We hypothesized that a topical mixture of purified deoxyribonucleosides would accelerate wound healing in an open wound model. DESIGN: Full-thickness 6-mm wounds were made on the ears of young adult rabbits. In some experiments, 2 of the 3 arteries in each ear were divided to induce wound ischemia. INTERVENTIONS: An equiweight mixture containing all 4 of the major deoxyribonucleosides (deoxyadenosine, deoxycytidine, deoxyguanosine, and thymidine), designated PN105, or other subgroups of deoxyribonucleosides, or vehicle (saline) was applied to wounds on 1 ear every 2 days, with the other ear serving as a control. MAIN OUTCOME MEASURES: Wound tissue was processed for histological examination 7 days after the initial wounding. Granulation tissue formation and epithelialization were measured in histological cross sections of wounds. RESULTS: Treatment of wounds with PN105 resulted in a 191% increase in total new granulation tissue (P<.05) and a higher incidence of complete wound reepithelialization (67% vs 37%; P<.05) when compared with controls, and a similar increase under ischemic conditions on day 7. Wound ischemia markedly impairs healing; PN 105 treatment resulted in a 242% increase in the amount of new granulation tissue formed by day 7 in ischemic wounds, relative to the appropriate controls (P<.05). All 4 of the major deoxyribonucleosides were required for optimum activity; mixtures with 3 or 2 were less active or inactive. CONCLUSIONS: Topically applied deoxyribonucleosides reproducibly accelerate wound healing in normal and ischemic wounds, and to a magnitude equivalent to that of recombinant growth factors such as platelet-derived growth factor, previously studied in this model. In view of their safety, availability, and efficacy, deoxyribonucleosides hold considerable promise for improving healing of chronic wounds.     

Acceleration of cutaneous wound healing by brassinosteroids

Brassinosteroids are plant growth hormones involved in cell growth, division, and differentiation. Their effects in animals are largely unknown, although recent studies showed that the anabolic properties of brassinosteroids are possibly mediated through the phosphoinositide 3‐kinase/protein kinase B signaling pathway. Here, we examined biological activity of homobrassinolide (HB) and its synthetic analogues in in vitro proliferation and migration assays in murine fibroblast and primary keratinocyte cell culture. HB stimulated fibroblast proliferation and migration and weakly induced keratinocyte proliferation in vitro. The effects of topical HB administration on progression of wound closure were further tested in the mouse model of cutaneous wound healing. C57BL/6J mice were given a full‐thickness dermal wound, and the rate of wound closure was assessed daily for 10 days, with adenosine receptor agonist CGS‐21680 as a positive control. Topical application of brassinosteroid significantly reduced wound size and accelerated wound healing in treated animals. mRNA levels of transforming growth factor beta and intercellular adhesion molecule 1 were significantly lower, while tumor necrosis factor alpha was nearly suppressed in the wounds from treated mice. Our data suggest that topical application of brassinosteroids accelerates wound healing by positively modulating inflammatory and reepithelialization phases of the wound repair process, in part by enhancing Akt signaling in the skin at the edges of the wound and enhancing migration of fibroblasts in the wounded area. Targeting this signaling pathway with brassinosteroids may represent a promising approach to the therapy of delayed wound healing.     

Acceleration of wound healing by a live yeast cell derivative

Acceleration of the normal rate of burn wound healing would serve to decrease the morbidity and possibly the mortality of burn victims. A live yeast cell derivative (LYCD) has previously been reported to stimulate wound epithelialization and this study was designed to evaluate that hypothesis. Twenty-six human skin graft donor sites in nine patients were compared in a double-blind, randomized, single-center inpatient study. Thin donor sites were used as a model for superficial wound healing. Statistically significant earlier angiogenesis and epithelialization occurred in donor sites treated with LYCD ointment as compared with donor sites in the same patients treated simultaneously with ointment base. Stinging pain was noted by seven patients, but in all cases the pain was mild and required no analgesia.     

Efficacy of photocrosslinkable chitosan hydrogel containing fibroblast growth factor-2 in a rabbit model of chronic myocardial infarction

BACKGROUND: Therapeutic angiogenesis in ischemic myocardium has been shown to be an effective strategy to improve regional blood flow and myocardial function. However, no effective delivery system for growth factor administration is yet known to induce important therapeutic angiogenic responses in ischemic myocardium. MATERIALS AND METHODS: FGF-2-incorporated chitosan (FGF-2/chitosan) hydrogels were immobilized on the surface of ischemic myocardium of rabbit models of chronic myocardial infarction by UV-irradiation. After 4 weeks, cardiac functional analyses by noradrenalin challenge and histopathological analyses were performed to evaluate the efficacy of a controlled release of FGF-2 from FGF-2/chitosan hydrogel immobilized on the surface of ischemic myocardium. RESULTS: Significant improvement by application of FGF-2/chitosan hydrogels was found in systolic pressure at the left ventricle, +dp/dt maximum, and -dp/dt maximum during noradrenalin challenge at a dose of 1 microg/kg/min. Histological observations showed that a significantly larger amount of viable myocardium and CD 31 immunostained blood vessels were found in the FGF-2/chitosan hydrogel-applied group than only the chitosan-applied and control groups. CONCLUSIONS: These preliminary results indicate that the controlled release of biologically active FGF-2 molecules from FGF-2/chitosan hydrogel induces angiogenesis and possibly collateral circulation in ischemic myocardium, thereby protecting the myocardium.     

Acceleration of wound healing by local application of fibronectin

Summary The process of wound healing under the influence of locally applied fibronectin, heparin and thrombin was studied in adult rabbits. Using immunofluorescence microscopy, a higher concentration of fibronectin within the wound area was found on the 1st day after fibronectin treatment. The tensile strength of the wounds was tested on the 6th, 9th and 12th day after operation. On the 9th day the tensile strength of the fibronectin-treated wounds was significantly higher than that of the control wounds on the 12th day after operation. The addition of heparin and thrombin, each in combination with fibronectin, did not show any significant effect on wound healing.Ph.D. thesis by D. Litzkow [14] prepared under the direction of Prof. J. Franke and B. Rahfoth     

Combination therapy of hydrogel and stem cells for diabetic wound healing

Diabetic wounds (DWs) are a common complication of diabetes mellitus; DWs have a low cure rate and likely recurrence, thus affecting the quality of patients’ lives. As traditional therapy cannot effectively improve DW closure, DW has become a severe clinical medical problem worldwide. Unlike routine wound healing, DW is difficult to heal because of its chronically arrested inflammatory phase. Although mesenchymal stem cells and their secreted cytokines can alleviate oxidative stress and stimulate angiogenesis in wounds, thereby promoting wound healing, the biological activity of mesenchymal stem cells is compromised by direct injection, which hinders their therapeutic effect. Hydro-gels form a three-dimensional network that mimics the extracellular matrix, which can provide shelter for stem cells in the inflammatory microenvironment with reactive oxygen species in DW, and maintains the survival and viability of stem cells. This review summarizes the mechanisms and applications of stem cells and hydrogels in treating DW; additionally, it focuses on the different applications of therapy combining hydrogel and stem cells for DW treatment.     

硒化壳聚糖促创面愈合作用的体内研究

目的:研究硒化壳聚糖软膏促浅Ⅱ度烫伤小鼠创面愈合的作用。方法:147只昆明种小鼠随机分为硒化壳聚糖软膏治疗组、基质治疗组和京万红治疗组,每组49只,采用将脱毛区置于70℃恒温水浴中6s的方法制成10%体表面积浅Ⅱ度烫伤模型,伤情经病理切片证实。各组创面分别用硒化壳聚糖软膏纱布(1ml/cm2)、基质纱布(1ml/cm2)、京万红纱布(1ml/cm2)覆盖包扎固定后放回笼中饲养,换药1次/天,观察愈合时间,于伤后12h,第1、3、5、7和9天,分别处死各组小鼠7只,检测含水量、羟脯氨酸、TNF、NO、ALT,另取7只做为正常对照。结果:①创面愈合时间:硒化壳聚糖软膏组为(12.9±2.9)天、基质组为(16.3±2.1)天、京万红组为(11.8±2.4)天,硒化壳聚糖软膏组比基质组明显缩短(P<0.05);②创面含水量:伤后第1、3、5天硒化壳聚糖软膏组[(86.3±3.5)%、(77.8±3.9)%、(72.3±2.7)%]创面含水量显著低于基质组[(92.8±3.2)%、(84.9±4.2)%、(77.2±2.8)%,(P<0.05)],伤后7～9天,各组均基本恢复到正常水平;③创面TNF-α水平:伤后12h至1天达高峰,随后逐渐下降,至伤后第5天仍高于正常对照组(P<0.05);伤后12h、1天、3天、5天,硒化壳聚糖软膏组和京万红组TNF水平明显低于基质组(P<0.05);④创面组织NO含量:伤后12h各烫伤组NO含量达高峰,随后下降,至伤后第9天仍高于正常对照组(P<0.05);伤后12h、1天,硒化壳聚糖软膏组和京万红组NO含量明显低于基质组(P<0.05);⑤创面羟脯氨酸含量:伤后5、7、9天硒化壳聚糖软膏组羟脯氨酸含量显著高于基质组和京万红组(P<0.05)。结论:硒化壳聚糖软膏能有效减少烫伤后早期创面组织NO和TNF-α释放,减少渗出和水肿,晚期通过增强创面胶原合成来促进创面愈合。     

Acceleration of wound healing by topical drug delivery via liposomes

Background: Despite intensive research, impaired wound healing remains a considerable complication. Therefore, topically applied liposome-encapsulated buflomedil hydrochloride was investigated for its ability to improve wound repair in normal (n=16) and ischemic (n=16) skin tissue. Methods: Experiments were performed using the wound healing model of the ear of hairless mice. Standardized skin wounds (4.25 mm²) were created by circular excision of the epidermal layer and the subcutaneous tissue. Liposomes were applied daily until complete neovascularization of the wound occurred. Tissue regeneration by complete epithelialization and neovascularization of the wound area, microcirculatory parameters, and leukocyte–endothelium interaction were investigated by means of intravital microscopy. Microvascular perfusion was assessed by laser-Doppler flowmetry. Results: Topical application of buflomedil liposomes led to a significantly (P<0.05) accelerated wound closure in both normal (9.6±0.7 days) and ischemic (13.4±0.1 days) skin tissue compared with animals that were treated with unloaded liposomes (controls; 13.1±0.8 days; 15.3±0.6 days). Complete neovascularization of the wound was also enhanced (P<0.05) in buflomedil-treated animals (normal tissue 18.8±0.4 days; ischemic tissue 19.6±0.7 days) compared with controls (20.6±0.6 days; 22.6±1.2 days). Conclusion: These data suggest that buflomedil-loaded liposomes might be of beneficial use for clinical wound care. Received: 20 January 1999; in revised form: 18 August 1999 Accepted: 20 August 1999     

Anti-inflammatory properties of a liposomal hydrogel with povidone-iodine (Repithel) for wound healing in vitro

A liposomal hydrogel with 3% povidone-iodine (PVP-ILH, Repithel((R))) has shown clinical benefit in settings where inflammation and/or reactive oxygen species are thought to impede wound healing (e.g., burns, chronic wounds and in smokers). This in vitro study investigated whether PVP-ILH is able to reduce inflammatory events responsible for the impairment of the wound healing process in such patients. Therefore, the following assays were conducted with PVP-ILH (and derived control hydrogels to identify the component responsible for the effect): inhibition of reactive oxygen species production by human polymorphonuclear neutrophils (PMNs) and in a cell-free system, oxygen consumption assay of PMNs (prior to oxidative burst), inhibition of human complement (limiting the generation of complement factors), mast cell degranulation, nitric oxide production by murine macrophages and TNF-alpha production by human monocytes/macrophages. Where toxicity could cause cell inhibition, cell viability was assessed. PVP-ILH and its components interacted in our series of bioassays at various stages in the inflammation cascade. Scavenging of superoxide anions was the most pronounced effect. Furthermore, povidone-iodine inhibited PMN production of reactive oxygen species (inhibition of oxygen consumption) and a mast cell inhibitory (stabilising) activity was observed. Based on these results, the clinically observed, beneficial wound healing effects of PVP-ILH may also be attributed to an impediment of inflammatory activity, mainly by iodine's free radical scavenging. Controlling oxidative stress in the wound may be of great importance, especially since further reactions as, e.g., the formation of peroxynitrite from NO and ROS are prevented.     

A novel in situ-formed hydrogel wound dressing by the photocross-linking of a chitosan derivative

In situ photopolymerized hydrogel dressings create minimally invasive methods that offer advantages over the use of preformed dressings such as conformability in any wound bed, convenience of application, and improved patient compliance and comfort. Here, we report an in situ-formed hydrogel membrane through ultraviolet cross-linking of a photocross-linkable azidobenzoic hydroxypropyl chitosan aqueous solution. The hydrogel membrane is stable, flexible, and transparent, with a bulk network structure of smoothness, integrity, and density. Fluid uptake ability, water vapor transmission rate, water retention, and bioadhesion of the thus resulted hydrogel membranes (0.1 mm thick) were determined to range from 97.0–96.3%, 2,934–2,561 g/m²/day, 36.69–22.94% (after 6 days), and 4.8–12.3 N/cm², respectively. These data indicate that the hydrogel membrane can maintain a long period of moist environment over the wound bed for enhancing reepithelialization. Specifically, these properties of the hydrogel membrane were controllable to some extent, by adjusting the substitution degree of the photoreactive azide groups. The hydrogel membrane also exhibited barrier function, as it was impermeable to bacteria but permeable to oxygen. In vitro experiments using two major skin cell types (dermal fibroblast and epidermal keratinocyte) revealed the hydrogel membrane have neither cytotoxicity nor an effect on cell proliferation. Taken together, the in situ photocross-linked azidobenzoic hydroxypropyl chitosan hydrogel membrane has a great potential in the management of wound healing and skin burn.     

Experimental evaluation of photocrosslinkable chitosan as a biologic adhesive with surgical applications.

BACKGROUND: In various surgical cases, effective tissue adhesives are required for both hemostasis (eg, intraoperative bleeding) and air sealing (eg, thoracic surgery). We have designed a chitosan molecule (Az-CH-LA) that can be photocrosslinked by ultraviolet (UV) light irradiation, thereby forming a hydrogel. The purpose of this work was to evaluate the effectiveness and safety of the photocrosslinkable chitosan hydrogel as an adhesive with surgical applications. METHODS: The sealing ability of the chitosan hydrogel, determined as a bursting pressure, was assessed with removed thoracic aorta, trachea, and lung of farm pigs and in a rabbit model. The carotid artery and lung of rabbits were punctured with a needle, and the chitosan hydrogel was applied to, respectively, stop the bleeding and the air leakage. In vivo chitosan degradability and biologic responses were histologically assessed in animal models. RESULTS: The bursting pressure of chitosan hydrogel (30 mg/mL) and fibrin glue, respectively, was 225 +/- 25 mm Hg (mean +/- SD) and 80 +/- 20 mm Hg in the thoracic aorta; 77 +/- 29 mm Hg and 48 +/- 21 mm Hg in the trachea; and in the lung, 51 +/- 11 mm Hg (chitosan hydrogel), 62 +/- 4 mm Hg (fibrin glue, rubbing method), and 12 +/- 2 mm Hg (fibrin glue, layer method). The sealing ability of the chitosan hydrogel was stronger than that of fibrin glue. All rabbits with a carotid artery (n = 8) or lung (n = 8) that was punctured with a needle and then sealed with chitosan hydrogel survived the 1-month observation period without any bleeding or air leakage from the puncture sites. Histologic examinations demonstrated that 30 days after application, a fraction of the chitosan hydrogel was phagocytosed by macrophages, had partially degraded, and had induced the formation of fibrous tissues around the hydrogel. CONCLUSIONS: A newly developed photocrosslinkable chitosan has demonstrated strong sealing ability and a great potential for use as an adhesive in surgical operations.     

Release of basic fibroblast growth factor from a crosslinked glycosaminoglycan hydrogel promotes wound healing

We describe synthetic extracellular matrix (sECM) hydrogel films composed of co-crosslinked thiolated derivatives of chondroitin 6-sulfate (CS) and heparin (HP) for controlled-release delivery of basic fibroblast growth factor (bFGF) to full-thickness wounds in genetically diabetic (db/db) mice. In this model for chronic wound repair, full-thickness wounds were treated with CS, CS-bFGF, or CS-HP-bFGF films. At 2 and 4 weeks postinjury, wound closure and formation of the new epidermis and dermis were determined. Both CS and CS-HP hydrogel films accelerated wound repair, even without bFGF. Addition of bFGF to CS films showed partial dose-dependent acceleration of wound repair. Importantly, addition of bFGF to co-crosslinked CS-HP sECM films showed a dramatic bFGF dose-dependent acceleration of wound healing, as well as improved dermis formation and vascularization. Compared with 27% wound closure in 2 weeks in the controls, 89% wound closure was observed for mice treated with the CS-HP-bFGF films. The synthetic CS-HP sECM films mimic the chemistry and biology of heparan sulfate proteoglycans, and may have clinical potential for topical delivery of growth factors to patients with compromised wound healing.     

Electrospun chitosan/polyvinyl alcohol nanofibre mats for wound healing

Chitosan (CS) aqueous salt blended with polyvinyl alcohol (PVA) nanofibre mats was prepared by electrospinning. CS was dissolved with hydroxybenzotriazole (HOBt), thiamine pyrophosphate (TPP) and ethylenediaminetetraacetic acid (EDTA) in distilled water without the use of toxic or hazardous solvents. The CS aqueous salts were blended with PVA at different weight ratios, and the effect of the solution ratios was investigated. The morphologies and mechanical and swelling properties of the generated fibres were analysed. Indirect cytotoxicity studies indicated that the CS/PVA nanofibre mats were non‐toxic to normal human fibroblast cells. The CS‐HOBt/PVA and CS‐EDTA/PVA nanofibre mats demonstrated satisfactory antibacterial activity against both gram‐positive and gram‐negative bacteria, and an in vivo wound healing test showed that the CS‐EDTA/PVA nanofibre mats performed better than gauze in decreasing acute wound size during the first week after tissue damage. In conclusion, the biodegradable, biocompatible and antibacterial CS‐EDTA/PVA nanofibre mats have potential for use as wound dressing materials.     

A multifunctional in situ–forming hydrogel for wound healing

In this study, a multifunctional in situ–forming hydrogel (MISG) was prepared as a wound dressing designed to stop bleeding, inhibit inflammation, relieve pain, and improve healing. A mixture of poloxamers 407 and 188 was used for the matrix of the MISG. Other ingredients include aminocaproic acid (to stop bleeding), povidone iodine (anti‐infective), lidocaine (pain relief), and chitosan (to enhance wound healing and regeneration). The incipient gelation temperature of the MISG was modified by varying the poloxamer concentration. Poloxamer cytotoxicity was evaluated in addition to the effect of the MISG on hemostasis in rabbits, pain relief in mice, bacteriostasis in vitro, and wound healing. The optimal MISG matrix consisted of 30% (w/v) poloxamer (407/188, 1 : 1, w/w) solution and was able to change to a gel within 10 minutes at 37 °C. The poloxamer solution had no cytotoxicity in fibroblasts. Compared to sterile gauze alone, the MISG significantly shortened average hemostasis time and decreased bleeding. The hydrogel showed strong bacteriostatic action similar to povidone iodine solution. It markedly increased the pain threshold and accelerated wound healing compared to the gauze. The MISG is a promising formulation for wound healing in emergency situations.     

Clinical experience with a new hydrogel wound dressing

A new dressing is described which appears to improve wound healing after partial-thickness skin loss. The period between dressing changes is increased and patient discomfort decreased. It has been particularly useful in the treatment of scalds in children. There is no evidence of an increased infection rate. Alternative methods of sterilization may reduce the small number of minor hypersensitivity reactions.