Effect of glycation on basic fibroblast growth factor induced angiogenesis and activation of associated signal transduction pathways in vascular endothelial cells: possible relevance to wound healing in diabetes

Revealing the molecular mechanisms in wound healing and the effects of different physiological factors including diabetes, age, and stress

Wounds are the common fates in various microbial infections and physical damages including accidents, surgery, and burns. In response, a healthy body with a potent immune system heals that particular site within optimal time by following the coagulation, inflammation, proliferation, and remodeling phenomenon. However, certain malfunctions in the body due to various diseases particularly diabetes and other physiological factors like age, stress, etc., prolong the process of wound healing through various mechanisms including the Akt, Polyol, and Hexosamine pathways. The current review thoroughly explains the wound types, normal wound healing mechanisms, and the immune system's role. Moreover, the mechanistic role of diabetes is also elaborated comprehensively.

The dynamic roles of advanced glycation end products

Advanced glycation end products (AGEs) are a heterogeneous group of potentially harmful molecules that can form as a result of a non-enzymatic reaction between reducing sugars and proteins, lipids, or nucleic acids. The total body pool of AGEs reflects endogenously produced AGEs as well as exogeneous AGEs that come from sources such as diet and the environment. Engagement of AGEs with their cellular receptor, the receptor for advanced glycation end products (RAGE), which is expressed on the surface of various cell types, converts a brief pulse of cellular activation to sustained cellular dysfunction and tissue destruction. The AGEs/RAGE interaction triggers a cascade of intracellular signaling pathways such as mitogen-activated protein kinase/extracellular signal-regulated kinase, phosphoinositide 3-kinases, transforming growth factor beta, c-Jun N-terminal kinases (JNK), and nuclear factor kappa B, which leads to the production of pro-inflammatory cytokines, chemokines, adhesion molecules, and oxidative stress. All these events contribute to the progression of several chronic diseases. This chapter will provide a comprehensive understanding of the dynamic roles of AGEs in health and disease which is crucial to develop interventions that prevent and mitigate the deleterious effects of AGEs accumulation.

Photobiomodulation Therapy Improves Inflammatory Responses by Modifying Stereological Parameters, microRNA-21 and FGF2 Expression

Introduction: Photobiomodulation treatment (PBMT) is a relatively invasive method for treating wounds. An appropriate type of PBMT can produce desired and directed cellular and molecular processes. The aim of this study was to investigate the impacts of PBMT on stereological factors, bacterial count, and the expression of microRNA-21 and FGF2 in an infected, ischemic, and delayed wound healing model in rats with type one diabetes mellitus. Methods: A delayed, ischemic, and infected wound was produced on the back skin of all 24 DM1 rats. Then, they were put into 4 groups at random (n=6 per group): 1=Control group day4 (CGday4); 2=Control group day 8 (CGday8); 3=PBMT group day4 (PGday4), in which the rats were exposed to PBMT and killed on day 4; 4=PBMT group day8 (PGday8), in which the rats received PBMT and they were killed on day 8. The size of the wound, the number of microbial colonies, stereological parameters, and the expression of microRNA-21 and FGF2 were all assessed in this study throughout the inflammation (day 4) and proliferation (day 8) stages of wound healing. Results: On days 4 and 8, we discovered that the PGday4 and PGday8 groups significantly improved stereological parameters in comparison with the same CG groups. In terms of ulcer area size and microbiological counts, the PGday4 and PGday8 groups performed much better than the same CG groups. Simultaneously, the biomechanical findings in the PGday4 and PGday8 groups were much more extensive than those in the same CG groups. On days 4 and 8, the expression of FGF2 and microRNA-21 was more in all PG groups than in the CG groups (P<0.01). Conclusion: PBMT significantly speeds up the repair of ischemic and MARS-infected wounds in DM1 rats by lowering microbial counts and modifying stereological parameters, microRNA-21, and FGF2 expression.

Advanced polymer hydrogels that promote diabetic ulcer healing: mechanisms, classifications, and medical applications

Diabetic ulcers (DUs) are one of the most serious complications of diabetes mellitus. The application of a functional dressing is a crucial step in DU treatment and is associated with the patient's recovery and prognosis. However, traditional dressings with a simple structure and a single function cannot meet clinical requirements. Therefore, researchers have turned their attention to advanced polymer dressings and hydrogels to solve the therapeutic bottleneck of DU treatment. Hydrogels are a class of gels with a three-dimensional network structure that have good moisturizing properties and permeability and promote autolytic debridement and material exchange. Moreover, hydrogels mimic the natural environment of the extracellular matrix, providing suitable surroundings for cell proliferation. Thus, hydrogels with different mechanical strengths and biological properties have been extensively explored as DU dressing platforms. In this review, we define different types of hydrogels and elaborate the mechanisms by which they repair DUs. Moreover, we summarize the pathological process of DUs and review various additives used for their treatment. Finally, we examine the limitations and obstacles that exist in the development of the clinically relevant applications of these appealing technologies. This review defines different types of hydrogels and carefully elaborate the mechanisms by which they repair diabetic ulcers (DUs), summarizes the pathological process of DUs, and reviews various bioactivators used for their treatment.

Sex difference on fibroblast growth factors (FGFs) expression in skin and wound of streptozotocin(STZ)-induced type 1 diabetic mice

BACKGROUND

Fibroblast growth factors (FGFs) are key factors affecting diabetic wound healing. However, the FGF family's expression patterns in skin and wounds influenced by both diabetes and sex are still unknown.

METHODS AND RESULTS

In this study, normal and Streptozotocin (STZ)-induced type 1 diabetic C57BL/6J male and female mice were used to study the FGF family's expression in non-wound skin and wounds. We found that the expression patterns of Fgfs were affected by sex in both normal and diabetic animals during wound healing. In normal control mice, sex difference had a limited effect on basal skin Fgf expressions. However, it significantly influenced Fgf expressions in wounds. Type 1 diabetes reduced basal and wound-induced skin Fgf expressions. Female mice had far lower wound-induced skin Fgf expressions in diabetic mice. In addition, sex differently influenced Fibroblast growth factors receptor (Fgfr) expression patterns of non-wound skin and wounds in both normal and diabetic mice. Moreover, female mice had a lower relative level of Fibronectin leucine-rich repeat transmembrane protein 2 (FLRT2) - a FGFR activation marker gene - in wound and blood plasma. Correspondingly, the wound areas of female animals were larger than that of male animals in the early stage of wound healing (less than 3-day injury).

CONCLUSION

Our research shows that the FGF family have different expression patterns in normal and diabetic wound healing in mice of different sex. Additionally, we also provide the signatures of individual FGFs in diabetic wound healing, which deserve further investigation.

Ceria Nanoenzyme-Based Hydrogel with Antiglycative and Antioxidative Performance for Infected Diabetic Wound Healing

Diabetic wound healing still faces a dilemma because of the hostile hyperglycemic, oxidative, and easily-infected wound microenvironment. In addition, advanced glycation end products (AGEs) further impede wound repair by altering the immunological balance. Herein, ceria nanorods with distinctive antiglycative and excellent antioxidative capacities are innovatively introduced into a self-healing and erasable hydrogel, which could reshape the wound microenvironment by expediting hemostasis, inhibiting infection, reducing AGEs, and continuously depleting reactive oxygen species. The remitted oxidative stress and glycosylation synergistically regulate inflammatory responses, and promote revascularization and extracellular matrix deposition, resulting in accelerated diabetic wound repair. This study provides a highly efficient strategy for constructing nanoenzyme-reinforced antiglycative hydrogel that regulates every wound healing stage for diabetic wound management.

Influence of Diabetes-Induced Glycation and Oxidative Stress on the Human Rotator Cuff

Most shoulder rotator cuff tears (RCTs) are caused by non-traumatic age-related rotator cuff degeneration, of which hyperglycemia is a risk factor due to its glycation reaction and oxidative stress. We aimed to identify the influence of diabetes-induced glycation and oxidative stress in patients with non-traumatic shoulder RCTs. Twenty patients, aged over 50 years, with non-traumatic shoulder RCTs participated in this study. Patients with a history of diabetes mellitus or preoperative HbA1c ≥ 6.5% were assigned to the diabetic group (n = 10), and the rest to the non-diabetic group (n = 10). Cell proliferation; expression of genes related to oxidative stress, glycation reaction, inflammation, and collagen; intracellular reactive oxygen species (ROS) levels; and apoptosis rates were analyzed. The diabetic group had significantly lower cell proliferation than the non-diabetic group. In the diabetic group, the mRNA expression levels of NOX1, NOX4, IL6, RAGE, type III collagen, MMP2, TIMP1, and TIMP2 were significantly higher; type I collagen expression was significantly lower; and the rate of ROS-positive cells and apoptotic cells, as well as the expression of advanced glycation end-products (AGEs) and the receptor for AGEs (RAGE), was significantly higher. In conclusion, hyperglycemia caused by diabetes mellitus increased AGE and RAGE expression, and led to increased NOX expression, ROS production, and apoptosis in the human rotator cuff. This provides scope to find a preventive treatment for non-traumatic RCTs by inhibiting glycation and oxidative stress.

The Role of Oxidative Stress and Antioxidants in Diabetic Wound Healing

Foot ulcers are one of the most common and severe complication of diabetes mellitus with significant resultant morbidity and mortality. Multiple factors impair wound healing include skin injury, diabetic neuropathy, ischemia, infection, inadequate glycemic control, poor nutritional status, and severe morbidity. It is currently believed that oxidative stress plays a vital role in diabetic wound healing. An imbalance of free radicals and antioxidants in the body results in overproduction of reactive oxygen species which lead to cell, tissue damage, and delayed wound healing. Therefore, decreasing ROS levels through antioxidative systems may reduce oxidative stress-induced damage to improve healing. In this context, we provide an update on the role of oxidative stress and antioxidants in diabetic wound healing through following four perspectives. We then discuss several therapeutic strategies especially dietary bioactive compounds by targeting oxidative stress to improve wounds healing.

Acceleration of wound healing activity with syringic acid in streptozotocin induced diabetic rats

Impaired wound healing is a serious concern of uncontrolled hyperglycemia that can lead to gangrene, and even death. There is an urgent need to look for better alternative therapy because of the undesirable side effects of currently available synthetic drugs in the market. Syringic acid (SA) is a natural phenolic compound abundantly available in edible fruits and plants. In this study, wound healing activities of 2.5% and 5.0% SA were evaluated in type 2 diabetic rats using incisional wound model. SA-treated diabetic wounds showed faster rate of wound closure and epithelization with enhanced contents of hydroxyproline and protein compared to diabetic wounds. SA effectively prevents alterations in blood glucose levels, serum insulin and dyslipidemia in diabetic wound rats. The SA-treated diabetic wounds after 14 days of treatment demonstrated inhibition of pro-inflammatory response (NF-κB p65, TNF-α, IL-1β, IL-8 and IL-2) with improvement in anti-inflammatory response (IL-10), inhibited the elevated oxidative stress and decreased the concentrations of matrix metalloproteinases (MMP-2, -8 and -9) and increased the concentrations of TIMP-1 & TIMP- 2. Furthermore, the diabetic wounds were presented with an increase in expression of CD 31 and 68, growth factors (TGF-β1, collagen-I and α-SMA and VEGF) with significant improvement in collagen deposition, re-epithelialization and complete skin structure as revealed by histological analysis after treatment of diabetic wounds with SA for 14 days. Hence, the results of this study designate that SA significantly improves wound healing in diabetic rats and could be used as a potential therapy for treatment of diabetic wounds.

Biopolymer-based biomaterials for accelerated diabetic wound healing: A critical review

Non-healing, chronic wounds place a huge burden on healthcare systems as well as individual patients. These chronic wounds especially diabetic wounds will ultimately lead to compromised mobility, amputation of limbs and even death. Currently, wounds and limb ulcers associated with diabetes remain significant health issues; the associated healthcare cost ultimately leads to the increased clinical burden. The presence of diabetes interrupts a highly coordinated cascade of events in the wound closure process. Advances in the understanding of pathophysiological conditions associated with diabetic wounds lead to the development of drug delivery systems which can enhance wound healing by targeting various phases of the impaired processes. Wound environments typically contain degradative enzymes, along with an elevated pH and demonstrate a physiological cascade involved in the regeneration of tissue, which requires the application of an effective delivery system. This article aims to review the pathophysiological conditions associated with chronic and diabetic wounds. The delivery systems, involved in their treatment are described, highlighting potential biomaterials and polymers for establishing drug delivery systems, specifically for the treatment of diabetic wounds and the promotion of the associated mechanisms involved in advanced wound healing. Emerging approaches and engineered devices for effective wound care are reported. The discussion will give insight into the mechanisms relevant to all stages of wound healing.

Influence of advanced glycation end products on rotator cuff

BACKGROUND

Most rotator cuff tears are the result of age-related degenerative changes, but the mechanisms underlying these changes have not been reported. Recently, advanced glycation end products (AGEs) have been regarded as an important factor in senescence. Therefore, we hypothesized that AGEs would have detrimental effects on rotator cuff-derived cells. In this study, we investigated the influence of AGEs on rotator cuff-derived cells in vitro and ex vivo.

METHODS

Rotator cuff-derived cells were obtained from human supraspinatus tendons. The cells were cultured in the following media: (1) regular medium with 500 μg/mL AGEs (High-AGEs), (2) regular medium with 100 μg/mL AGEs (Low-AGEs), and (3) regular medium alone (Control). Cell viability, secretion of vascular endothelial growth factor, and the expressions of hypoxia-inducible factor-1α, reactive oxygen species, and apoptosis were assessed after cultivation. An ex vivo tissue culture with AGEs was also performed to measure the tensile strength.

RESULTS

Cell viability in the High-AGEs group was significantly suppressed relative to that in the Controls. The amount of vascular endothelial growth factor secretion was significantly greater in the High- and Low-AGEs groups than in the Controls. Immunofluorescence stain demonstrated enhancement of hypoxia-inducible factor-1α and reactive oxygen species expressions and cell apoptosis in the High- and Low-AGEs groups relative to that in the Controls. In ex vivo mechanical testing, tensile strength was significantly higher in the Control group than in the AGEs groups.

DISCUSSION

These results indicated that AGEs caused age-related degenerative rotator cuff changes. The reduction of AGEs might prevent rotator cuff senescence-related degeneration.

The link between advanced glycation end products and apoptosis in delayed wound healing

Advanced glycation end products (AGEs) are naturally occurring molecules that start to accumulate from embryonic developmental stages and form as part of normal ageing. When reducing sugars interact with and modify proteins or lipids, AGE production occurs. AGE formation accelerates in chronic hyperglycemic conditions, and high AGE levels have been associated with the pathogenesis of various diseases. In addition, enhanced levels of AGEs have been linked to delayed wound healing as seen in patients with diabetes mellitus. Research has provided numerous ways in which a high AGE concentration results in impaired wound healing, including oxidative stress, structural and functional changes to proteins important in wound repair, an enhanced inflammatory response by activation of transcription factors, and possible exaggerated apoptosis of cells necessary to the wound repair process. Apoptosis is a naturally occurring cell death process that is significant for normal tissue functioning and plays an important role in wound repair by preventing a prolonged inflammatory response and excessive scar formation. Abnormal apoptosis affects wound healing, resulting in slow healing wounds. This review will summarize the role of AGEs in wound healing, focusing on the mechanisms by which AGEs lead to apoptosis in various cell types. The review provides the way forward for medical research and molecular studies as it focuses on the mechanisms by which AGEs induce apoptosis in various cell types, including fibroblasts, osteoblasts, neuronal cells, and endothelial cells. Reviewing the mechanisms of AGE-linked apoptosis is important in understanding the impact of high AGE levels in delayed wound healing in diabetic patients due to abnormal apoptosis of cells necessary to the wound healing process.

Essential Role of IL-12 in Angiogenesis in Type 2 Diabetes

Recently, IL-12 emerged as a critical player in type 2 diabetes complications. We previously reported that ischemia-induced angiogenesis is compromised in type 2 diabetic mice. In this study, we determined that IL-12 disruption rescued angiogenesis and arteriogenesis in type 2 diabetic mice. To induce type 2 diabetes, wild-type (WT), p40IL-12^-/- (p40^-/-), and p35IL-12^-/- (p35^-/-) mice were fed a high-fat diet (HFD) for 12 weeks. Body weight, glucose test tolerance, and insulin test tolerance were assessed. After 12 weeks of an HFD, the femoral artery was ligated and blood flow recovery was measured every week for 4 weeks. WT, p40^-/-, and p35^-/- mice fed an HFD become obese after 12 weeks and exhibit glucose intolerance and insulin resistance. Blood flow recovery was fully restored in 2 to 3 weeks after femoral artery ligation in all groups of mice fed a normal diet. However, after 12 weeks of an HFD, blood flow recovery was compromised in WT mice, whereas it was fully recovered in p40^-/- and p35^-/- mice. The mechanism of blood flow recovery involves an increase in capillary/arteriole density, endothelial nitric oxide synthase/Akt/vascular endothelial growth factor receptor 2 signaling, and a reduction in oxidative stress and inflammation. The disruption of IL-12 promotes angiogenesis and increases blood flow recovery in obese type 2 diabetic mice by an endothelial nitric oxide synthase/Akt/vascular endothelial growth factor receptor 2/oxidative stress-inflammation-dependent mechanism.

Altered ECM deposition by diabetic foot ulcer-derived fibroblasts implicates fibronectin in chronic wound repair

Current chronic wound treatments often fail to promote healing of diabetic foot ulcers (DFU), leading to amputation and increased patient morbidity. A critical mediator of proper wound healing is the production, assembly, and remodeling of the extracellular matrix (ECM) by fibroblasts. However, little is known about how these processes are altered in fibroblasts within the DFU microenvironment. Thus, we investigated the capacity of multiple, primary DFU-derived fibroblast strains to express, produce, and assemble ECM proteins compared to diabetic patient-derived fibroblasts and healthy donor-derived fibroblasts. Gene expression microarray analysis showed differential expression of ECM and ECM-regulatory genes by DFU-derived fibroblasts which translated to functional differences in a 3D in vitro ECM tissue model. DFU-derived fibroblasts produced thin, fibronectin-rich matrices, and responded abnormally when challenged with transforming growth factor-beta, a key regulator of matrix production during healing. These results provide novel evidence that DFU-derived fibroblasts contribute to the defective matrices of DFUs and chronic wound pathogenesis.

Heparin-Based Coacervate of FGF2 Improves Dermal Regeneration by Asserting a Synergistic Role with Cell Proliferation and Endogenous Facilitated VEGF for Cutaneous Wound Healing

Effective wound healing requires complicated, coordinated interactions and responses at protein, cellular, and tissue levels involving growth factor expression, cell proliferation, wound closure, granulation tissue formation, and vascularization. In this study, we develop a heparin-based coacervate consisting of poly(ethylene argininylaspartate digylceride) (PEAD) as a storage matrix, heparin as a bridge, and fibroblast growth factor-2 (FGF2) as a cargo (namely heparin-FGF2@PEAD) for wound healing. First, in vitro characterization demonstrates the loading efficiency and control release of FGF2 from the heparin-FGF2@PEAD coacervate. The following in vivo studies examine the wound healing efficiency of the heparin-FGF2@PEAD coacervate upon delivering FGF2 to full-thickness excisional skin wounds in vivo, in comparison with the other three control groups with saline, heparin@PEAD as vehicle, and free FGF2. Collective in vivo data show that controlled release of FGF2 to the wounds by the coacervate significantly accelerates the wound healing by promoting cell proliferation, stimulating the secretion of vascular endothelial growth factor (VEGF) for re-epithelization, collagen deposition, and granulation tissue formation, and enhancing the expression of platelet endothelial cell adhesion molecule (CD31) and alpha-smooth muscle actin (α-SMA) for blood vessel maturation. In parallel, no obvious wound healing effect is found for the control, vehicle, and free FGF2 groups, indicating the important role of the coavervate in the wound healing process. This work designs a suitable delivery system that can protect and release FGF2 in a sustained and controlled manner, which provides a promising therapeutic potential for topical treatment of wounds.

A new in vivo model using a dorsal skinfold chamber to investigate microcirculation and angiogenesis in diabetic wounds

Introduction: Diabetes mellitus describes a dysregulation of glucose metabolism due to improper insulin secretion, reduced insulin efficacy or both. It is a well-known fact that diabetic patients are likely to suffer from impaired wound healing, as diabetes strongly affects tissue angiogenesis. Until now, no satisfying in vivo murine model has been established to analyze the dynamics of angiogenesis during diabetic wound healing. To help understand the pathophysiology of diabetes and its effect on angiogenesis, a novel in vivo murine model was established using the skinfold chamber in mice.

Materials and Methods: Mutant diabetic mice (db; BKS.Cg-m+/+Lepr^db/J), wildtype mice (dock7Lepr^db+/+m) and laboratory BALB/c mice were examined. They were kept in single cages with access to laboratory chow with an 12/12 hour day/night circle. Lesions of the panniculus muscle (Ø 2 mm) were created in the center of the transparent window chamber and the subsequent muscular wound healing was then observed for a period of 22 days. Important analytic parameters included vessel diameter, red blood cell velocity, vascular permeability, and leakage of muscle capillaries and post capillary venules. The key parameters were functional capillary density (FCD) and angiogenesis positive area (APA).

Results: We established a model which allows high resolution in vivo imaging of functional angiogenesis in diabetic wounds. As expected, db mice showed impaired wound closure (day 22) compared to wounds of BALB/c or WT mice (day 15). FCD was lower in diabetic mice compared to WT and BALB/c during the entire observation period. The dynamics of angiogenesis also decreased in db mice, as reflected by the lowest APA levels. Significant variations in the skin buildup were observed, with the greatest skin depth in db mice. Furthermore, in db mice, the dermis:subcutaneous ratio was highly shifted towards the subcutaneous layers as opposed to WT or BALB/c mice.

Conclusion: Using this new in vivo model of the skinfold chamber, it was possible to analyze and quantify microangiopathical changes which are essential for a better understanding of the pathophysiology of disturbed wound healing. Research in microcirculation is important to display perfusion in wounds versus healthy tissue. Using our model, we were able to compare wound healing in diabetic and healthy mice. We were also able to objectively analyze perfusion in wound edges and compare microcirculatory parameters. This model may be well suited to augment different therapeutic options.

Aminoguanidine cream ameliorates skin tissue microenvironment in diabetic rats

INTRODUCTION

The aim of the study was to explore the effect of aminoguanidine cream on the skin tissue microenvironment in diabetic rats.

MATERIAL AND METHODS

A total of 51 healthy male Sprague Dawley (SD) rats were randomly divided into three groups: the diabetes group (n = 18), the aminoguanidine group (n = 18) and the control group (n = 15). Rats in the diabetes group and aminoguanidine group were injected with 65 mg/kg streptozotocin to induce the diabetes model, and in the control group with citrate buffer. After successful induction of diabetes, the back hair of all rats was stripped by barium sulfide, and the aminoguanidine group was treated with aminoguanidine cream using disinfected cotton swabs twice every day for 40 days, while the diabetes and control groups were treated with the cream matrix. The pathological changes of skin were observed by HE staining, while the content of inflammatory cytokines (TNF-α, IL-8, ICAM and IL-1α) and the antioxidant indexes (T-AOC, GSH-PX, MPO MDA H2O2) were examined using commercial kits.

RESULTS

After 40 days of treatment, the diabetes group manifested tissue lesions, whereas the aminoguanidine group seemed normal. Compared with the diabetes group, the content of inflammatory cytokines TNF-α, IL-8, ICAM and IL-1α was dramatically lower in the aminoguanidine group. T-AOC in all groups underwent dramatic changes and returned to normal finally. The activities of GSH-PX and MPO and content of H2O2 in the diabetes group were all higher than those in the aminoguanidine group.

CONCLUSIONS

Aminoguanidine may have a good systemic effect on alleviating the pathological changes of skin tissue in diabetic rats, which may be attributed to the regulation of GSH-PX, TNF-α, IL-8, ICAM and IL-1α.

Effect of living cellular sheets on the angiogenic potential of human microvascular endothelial cells

BACKGROUND

A fundamental issue limiting the efficacy of surgical approaches designed to correct periodontal mucogingival defects is that new tissues rely on limited sources of blood supply from the adjacent recipient bed. Accordingly, therapies based on tissue engineering that leverage local self-healing potential may represent promising alternatives for the treatment of mucogingival defects by inducing local vascularization. The aim of this study is to evaluate the effect of commercially available living cellular sheets (LCS) on the angiogenic potential of neonatal dermal human microvascular endothelial cells (HMVEC-dNeo).

METHODS

The effect of LCS on HMVEC-dNeo proliferation, migration, capillary tube formation, gene expression, and production of angiogenic factors was evaluated over time.

RESULTS

LCS positively influenced HMVEC-dNeo proliferation and migration. Moreover, HMVEC-dNeo incubated with LCS showed transcriptional profiles different from those of untreated cells. Whereas increased expression of angiogenic genes predominated early on in response to LCS, late-phase responses were characterized by up- and downregulation of angiostatic and angiogenic genes. However, this trend was not confirmed at the protein level, as LCS induced increased production of most of the angiogenic factors tested (i.e., epidermal growth factor [EGF], heparin-binding EGF-like growth factor, interleukin 6, angiopoietin, platelet-derived growth factor-BB, placental growth factor, and vascular endothelial growth factor) throughout the investigational period. Finally, although LCS induced HMVEC-dNeo proliferation, migration, and expression of angiogenic factors, additional factors and environmental pressures are likely to be required to promote the development of complex, mesh-like vascular structures.

CONCLUSION

LCS favor initial mechanisms that govern angiogenesis but failed to enhance or accelerate HMVEC-dNeo morphologic transition to complex vascular structures.

Understanding regulatory pathways of neovascularization in diabetes

Diabetes mellitus and its associated comorbidities represent a significant health burden worldwide. Vascular dysfunction is the major contributory factor in the development of these comorbidities, which include impaired wound healing, cardiovascular disease and proliferative diabetic retinopathy. While the etiology of abnormal neovascularization in diabetes is complex and paradoxical, the dysregulation of the varied processes contributing to the vascular response are due in large part to the effects of hyperglycemia. In this review, we explore the mechanisms by which hyperglycemia disrupts chemokine expression and function, including the critical hypoxia inducible factor-1 axis. We place particular emphasis on the therapeutic potential of strategies addressing these pathways; as such targeted approaches may one day help alleviate the healthcare burden of diabetic sequelae.

Glycation: the angiogenic paradox in aging and age-related disorders and diseases

Angiogenesis is generally a quiescent process which, however, may be modified by different physiological and pathological conditions. The "angiogenic paradox" has been described in diabetes because this disease impairs the angiogenic response in a manner that differs depending on the organs involved and disease evolution. Aging is also associated with pro- and antiangiogenic processes. Glycation, the post-translational modification of proteins, increases with aging and the progression of diabetes. The effect of glycation on angiogenesis depends on the type of glycated proteins and cells involved. This complex link could be responsible for the "angiogenic paradox" in aging and age-related disorders and diseases. Using diabetes as a model, the present work has attempted to review the age-related angiogenic paradox, in particular the effects of glycation on angiogenesis during aging.

In vitro and in vivo epidermal growth factor gene therapy for diabetic ulcers with electrospun fibrous meshes

Human epidermal growth factor (hEGF) gene therapy was achieved with an electrospun nanofibrous mesh with matrix metalloproteinase (MMP) responsiveness to control release of plasmid human epidermal growth factor (phEGF) in diabetic ulcers. For MMP responsiveness, linear poly(ethyleneimine) (LPEI) was immobilized on the surface of the nanofiber via an MMP-cleavable linker. phEGF was electrostatically incorporated into LPEI-immobilized nanofibrous meshes with various charge ratios and phEGF incorporation efficiency was increased with increasing charge ratios. The release of both phEGF and LPEI was significantly increased in the presence of MMP-2 due to the enzymatic digestion of the MMP-cleavable linkage between the matrix and LPEI. Human dermal fibroblasts with the released fraction showed a higher expression level of hEGF compared to naked phEGF or phEGF/LPEI complexes. Diabetic wounds treated with phEGF-incorporated nanofibrous meshes showed high hEGF expression level and accelerated wound recovery rates without wound contractions for 14days. Neocollagen and cytokeratin accumulation were significantly increased as well as the expression of the keratinocyte-specific markers at the re-epithelized tissue treated with phEGF nanofibrous meshes, which clearly indicates that EGF gene was transfected to dermal cells and this consequently assisted wound recovery without phenotypic changes of the re-epithelized tissues. Thus, phEGF-incorporated nanofibrous mesh is expected to accelerate the wound-healing process as well as reduce wound contraction during recovery from diabetic ulcers.

Wound bed preparation for chronic diabetic foot ulcers

The escalating incidence of diabetic mellitus has given rise to the increasing problems of chronic diabetic ulcers that confront the practice of medicine. Peripheral vascular disease, neuropathy, and infection contribute to the multifactorial pathogenesis of diabetic ulcers. Approaches to the management of diabetic ulcers should start with an assessment and optimization of the patient's general conditions, followed by considerations of the local and regional factors. This paper aims to address the management strategies for wound bed preparation in chronic diabetic foot ulcers and also emphasizes the importance of preventive measures and future directions. The “TIME” framework in wound bed preparation encompasses tissue management, inflammation and infection control, moisture balance, and epithelial (edge) advancement. Tissue management aims to remove the necrotic tissue burden via various methods of debridement. Infection and inflammation control restores bacterial balance with the reduction of bacterial biofilms. Achieving a moist wound healing environment without excessive wound moisture or dryness will result in moisture balance. Epithelial advancement is promoted via removing the physical and biochemical barriers for migration of epithelium from wound edges. These systematic and holistic approaches will potentiate the healing abilities of the chronic diabetic ulcers, including those that are recalcitrant.

Evaluation of wound healing activity of ferulic acid in diabetic rats

In diabetic patients, there is impairment in angiogenesis, neovascularisation and failure in matrix metalloproteineases (MMPs), keratinocyte and fibroblast functions, which affects wound healing mechanism. Hence, diabetic patients are more prone to infections and ulcers, which finally result in gangrene. Ferulic acid (FA) is a natural antioxidant found in fruits and vegetables, such as tomatoes, rice bran and sweet corn. In this study, wound healing activity of FA was evaluated in streptozotocin-induced diabetic rats using excision wound model. FA-treated wounds were found to epithelise faster as compared with diabetic wound control group. The hydroxyproline and hexosamine content increased significantly when compared with diabetic wound control. FA effectively inhibited the lipid peroxidation and elevated the catalase, superoxide dismutase, glutathione and nitric oxide levels along with the increase in the serum zinc and copper levels probably aiding the wound healing process. Hence, the results indicate that FA significantly promotes wound healing in diabetic rats.

Topical application of Sadat-Habdan mesenchymal stimulating peptide (SHMSP) accelerates wound healing in diabetic rabbits

Objective. Diminished wound healing is a common problem in diabetic patients due to diminished angiogenesis. SHMSP was found to promote angiogenesis. The present study was carried out to examine the effect of this peptide in healing of wounds in diabetic rabbits. Materials and Methods. Twenty male New Zealand rabbits were used in this study. Diabetes mellitus was induced and the rabbits were randomly divided into two equal groups: control group and peptide group. A-full thickness punch biopsy was made to create a wound of about 10 mm on the right ears of all rabbits. Every day, the wound was cleaned with saline in control groups. In the peptide group, 15 mg of SHMSP was applied after cleaning. On day 15th, all animals were sacrificed, and the wounds were excised with a rim of 5 mm of normal surrounding tissue. Histo-pathological assessment of wound healing, inflammatory cell infiltration, blood vessel proliferation, and collagen deposition was performed. Results. There were no deaths among the groups. There was significant increase in wound healing, blood vessel proliferation and collagen deposition, and significant decrease in inflammatory cell infiltration in the peptide group compared to the control group. Conclusion. Topical application of SHMSP improves wound healing in diabetic rabbits.

Synergistic interaction between Astragali Radix and Rehmanniae Radix in a Chinese herbal formula to promote diabetic wound healing

ETHNOPHARMACOLOGICAL RELEVANCE

Astragali Radix (AR) and Rehmanniae Radix (RR) are two traditional Chinese medicines widely used in China for treating diabetes mellitus and its complications, such as diabetic foot ulcer.

AIM OF STUDY

In our previous study, a herbal formula NF3 comprising AR and RR in the ratio of 2:1 was found effective in enhancing diabetic wound healing in rats through the actions of tissue regeneration, angiogenesis promotion and inflammation inhibition. The aims of the present study were to investigate the herb-herb interaction (or the possible synergistic effect) between AR and RR in NF3 to promote diabetic wound healing and to identify the principal herb in the formula by evaluating the potencies of individual AR and RR in different mechanistic studies.

MATERIALS AND METHODS

A chemically induced diabetic foot ulcer rat model was used to examine the wound healing effect of NF3 and its individual herbs AR and RR. For mechanistic studies, murine macrophage cell (RAW 264.7) inflammation, human fibroblast (Hs27) proliferation and human endothelial cell (HMEC-1) migration assays were adopted to investigate the anti-inflammatory, granulation formation and angiogenesis-promoting activities of the herbal extracts, respectively.

RESULTS

In the foot ulcer animal model, neither AR nor RR at clinical relevant dose (0.98g/kg) promoted diabetic wound healing. However, when they were used in combination as NF3, synergistic interaction was demonstrated, of which NF3 could significantly reduce the wound area of rats when compared to water group (p<0.01). For anti-inflammation and granulation formation, AR was more effective than RR in inhibiting lipopolysaccharide (LPS)-induced nitric oxide production from RAW 264.7 cells and promoting Hs27 fibroblast proliferation. In the aspect of angiogenesis promotion, only NF3 promoted cell migration of HMEC-1 cells.

CONCLUSIONS

AR plays a preeminent role in the anti-inflammatory and fibroblast-proliferating activities of NF3. The inclusion of RR, however, is crucial for NF3 to exert its overall wound-healing as well as the underlying angiogenesis-promoting effects. The results of present study justified the combined usage of AR and RR in the ratio of 2:1 as NF3 to treat diabetic foot ulcer and illustrated that AR is the principal herb in this herbal formula.

Effect of autologous bone marrow mononuclear cells transplantation in diabetic patients with ST-segment elevation myocardial infarction

BACKGROUND

To investigate the efficacy and proposed mechanism of bone marrow mononuclear cells (BMMNCs) transplantation for diabetic and non-diabetic patients with ST-segment elevation myocardial infarction (STEMI).

METHODS

One hundred and sixteen patients with STEMI who had successfully undergone percutaneous coronary intervention (PCI) were divided into a diabetic group (n=51) and non-diabetic group (n=65). All of the patients received intracoronary injection of BMMNCs.

RESULTS

Diabetes down-regulated IGF-1, IGFBP-5, VEGF, SDF-1, IL-6, IL-1α and TNF-α expression and affected the expression of Bmi-1, Gfi1, Tel and Hox-B4 which could prevent premature senescence and maintain the self-renewal capacity of stem cells. Event-free survival rates were not statistically different between the diabetic and non-diabetic group (80% vs. 72.5%, p=0.382). LV ejection fraction (LVEF) and wall motion score index (WMSI) were evaluated by echocardiography and found to be significantly improved in the non-diabetic group compared to the diabetic group over the 4-year follow-up period. Improved myocardial perfusion and reduced infarct size in the non-diabetic group compared to the diabetic group was verified using single-photon emission computed tomographic (SPECT) imaging. The non-diabetic group also had reduced anginal symptoms as assessed by changes in their Seattle Angina Questionnaire scores and Canadian Cardiovascular Society (CCS) Functional Angina classification. An improvement of 6-minute walk distance (6MWD) was also noted to be higher in the non-diabetic group during the follow-up period.

CONCLUSION

This study indicates that the beneficial effect of BMMNCs transplantation for STEMI is less pronounced in diabetic patients. The mechanism is associated with decreased BMMNCs function in diabetic patients.

Numerous isoforms of Fgf8 reflect its multiple roles in the developing brain

Soluble growth factors play an important role in the coordination and integration of cell proliferation, differentiation, fate determination, and morphogenesis during development of multicellular organisms. Fibroblast growth factors (FGFs) are a large family of polypeptide growth factors that are present in organisms ranging from nematodes to humans. RNA alternative splicing of FGFs and their receptors further enhances the complexity of this ligand-receptor system. The mouse Fgf8 gene produces eight splice variants, which encode isoform proteins with different N-termini and distinct receptor-binding affinity and biological activity. In this article, we review the roles of Fgf8 in vertebrate development and summarize the recent findings on the in vivo function of different Fgf8 splice variants. We propose that multiple Fgf8 isoform proteins act in concert to regulate the overall function of Fgf8 and account for the diverse and essential role of Fgf8 during vertebrate development.

Changes in cardiac heparan sulfate proteoglycan expression and streptozotocin-induced diastolic dysfunction in rats

Background

Changes in the proteoglycans glypican and syndecan-4 have been reported in several pathological conditions, but little is known about their expression in the heart during diabetes. The aim of this study was to investigate in vivo heart function changes and alterations in mRNA expression and protein levels of glypican-1 and syndecan-4 in cardiac and skeletal muscles during streptozotocin (STZ)-induced diabetes.

Methods

Diabetes was induced in male Wistar rats by STZ administration. The rats were assigned to one of the following groups: control (sham injection), after 24 hours, 10 days, or 30 days of STZ administration. Echocardiography was performed in the control and STZ 10-day groups. Western and Northern blots were used to quantify protein and mRNA levels in all groups. Immunohistochemistry was performed in the control and 30-day groups to correlate the observed mRNA changes to the protein expression.

Results

In vivo cardiac functional analysis performed using echocardiography in the 10-day group showed diastolic dysfunction with alterations in the peak velocity of early (E) diastolic filling and isovolumic relaxation time (IVRT) indices. These functional alterations observed in the STZ 10-day group correlated with the concomitant increase in syndecan-4 and glypican-1 protein expression. Cardiac glypican-1 mRNA and skeletal syndecan-4 mRNA and protein levels increased in the STZ 30-day group. On the other hand, the amount of glypican in skeletal muscle was lower than that in the control group. The same results were obtained from immunohistochemistry analysis.

Conclusion

Our data suggest that membrane proteoglycans participate in the sequence of events triggered by diabetes and inflicted on cardiac and skeletal muscles.

Benefit-risk assessment of becaplermin in the treatment of diabetic foot ulcers

Becaplermin is a recombinant platelet-derived growth factor composed of two B chains that is approved for the treatment of neuropathic diabetic foot ulcers extending into or beyond the subcutaneous tissue in patients with adequate arterial perfusion. The aim of this review is to assess the benefits and risks associated with the use of this agent. Randomized controlled trials have provided evidence for the efficacy of becaplermin in increasing healing rates, and cost analyses have repeatedly shown a favourable cost-effectiveness ratio. However, clinical experience has not met these high expectations and becaplermin is not widely used. Moreover, this agent has not been compared with other additional treatment modalities, notably bioengineered skin substitutes and extracellular matrix proteins, and such comparisons are eagerly awaited. Of particular note, increased cancer risk has been reported in patients treated with more than three tubes of becaplermin; thus, this agent should be used only when the anticipated benefits outweigh the potential harm, and with extreme caution in patients with diagnosed malignancy. Finally, longer follow-up data are necessary to shed more light on the potential risk of malignancy in connection with becaplermin use.

Hyperglycemic oxoaldehyde, glyoxal, causes barrier dysfunction, cytoskeletal alterations, and inhibition of angiogenesis in vascular endothelial cells: aminoguanidine protection

Vascular endothelium is vulnerable to the attack of glucose-derived oxoaldehydes (glyoxal and methylglyoxal) during diabetes, through the formation of advanced glycation end products (AGEs). Although aminoguanidine (AG) has been shown to protect against the AGE-induced adverse effects, its protection against the glyoxal-induced alterations in vascular endothelial cells (ECs) such as cytotoxicity, barrier dysfunction, and inhibition of angiogenesis has not been reported and we investigated this in the bovine pulmonary artery ECs (BPAECs). The results showed that glyoxal (1-10 mM) significantly induced cytotoxicity and mitochondrial dysfunction in a dose- and time-dependent (4-12 h) fashion in ECs. Glyoxal was also observed to significantly inhibit EC proliferation. The study also revealed that glyoxal induced EC barrier dysfunction (loss of trans-endothelial electrical resistance), actin cytoskeletal rearrangement, and tight junction alterations in BPAECs. Furthermore, the results revealed that glyoxal significantly inhibited in vitro angiogenesis on the Matrigel. For the first time, this study demonstrated that AG significantly protected against the glyoxal-induced cytotoxicity, barrier dysfunction, cytoskeletal rearrangement, and inhibition of angiogenesis in BPAECs. Therefore, AG appears as a promising protective agent in the treatment of AGE-induced vascular endothelial alterations and dysfunction during diabetes, presumably by blocking the reactivity of the sugar-derived dicarbonyls such as glyoxal and preventing the formation of AGEs.

Hyperglycemia and glycation in diabetic complications

Diabetes mellitus is a multifactorial disease, classically influenced by genetic determinants of individual susceptibility and by environmental accelerating factors, such as lifestyle. It is considered a major health concern,as its incidence is increasing at an alarming rate, and the high invalidating effects of its long-term complications affect macro- and microvasculature, heart, kidney, eye, and nerves. Increasing evidence indicates that hyperglycemia is the initiating cause of the tissue damage occurring in diabetes, either through repeated acute changes in cellular glucose metabolism, or through the long-term accumulation of glycated biomolecules and advanced glycation end products (AGEs). AGEs represent a heterogeneous group of chemical products resulting from a nonenzymatic reaction between reducing sugars and proteins, lipids, nucleic acids, or a combination of these.The glycation process (glucose fixation) affects circulating proteins (serum albumin, lipoprotein, insulin, hemoglobin),whereas the formation of AGEs implicates reactive intermediates such as methylglyoxal. AGEs form cross-links on long-lived extracellular matrix proteins or react with their specific receptor RAGE, resulting inoxidative stress and proinflammatory signaling implicated in endothelium dysfunction, arterial stiffening, and microvascular complications. This review summarizes the mechanism of glycation and of AGEs formation and the role of hyperglycemia, AGEs, and oxidative stress in the pathophysiology of diabetic complications.

Advanced glycoxidation products and impaired diabetic wound healing

Impaired wound healing is an important diabetic complication associated with increased morbidity and mortality. It appears to be the net result of micro- and macrovascular disease. Diabetic neuropathy and the resulting loss of protective sensation (LOPS) has been recognized as one of the major causes for delayed healing in diabetic foot ulcer patients. In addition, hyperglycemia and a number of hyperglycemia-related factors have been linked to impaired diabetic wound healing, including advanced glycation end products (AGE). A large body of evidence from in vitro and in vivo studies and also data from studies using anti-AGE agents, indicate that AGE may play a role in the pathogenesis of impaired diabetic wound healing. AGE affect the wound healing process either directly by their interference with a variety of components involved or indirectly through their association with diabetic neuropathy and/or angiopathy. However, further studies need to be performed, mostly clinical studies, to evaluate the exact role of AGE in the impaired diabetic wound healing, suggesting new therapeutic approaches.

Stilbene glycosides are natural product inhibitors of FGF-2-induced angiogenesis

BACKGROUND

Angiogenesis, the growth of new blood vessels from the pre-existing vasculature is associated with pathological processes, in particular tumour development, and is a target for the development of new therapies. We have investigated the anti-angiogenic potential of two naturally occurring stilbene glycosides (compounds 1 and 2) isolated from the medicinal plant Boswellia papyriferai using large and smallvessel-derived endothelial cells. Compound 1 (trans-4',5'-dihydroxy-3-methoxystilbene-5-O-{alpha-L-rhamnopyranosyl-(1-->2)-[alpha-L-rhamnopyranosyl-(1-->6)}-beta-D-glucopyranoside was the more hydrophilic and inhibited FGF-2-induced proliferation, wound healing, invasion in Matrigel, tube formation and angiogenesis in large and small vessel-derived endothelial cells and also in the chick chorioallantoic membrane assay. Using a binding assay we were able to show compound 1 reduced binding of FGF-2 to fibroblast growth factor receptors-1 and -2. In all cases the concentration of compound 1 which caused 50% inhibition (IC50) was determined. The effect of compound 1 on EGF and VEGF-induced proliferation was also investigated.

RESULTS

Compound 1 inhibited all stages of FGF-2 induced angiogenesis with IC50 values in the range 5.8 +/- 0.18 - 48.90 +/- 0.40 microM but did not inhibit EGF or VEGF-induced angiogenesis. It also inhibited FGF-2 binding to FGF receptor-1 and -2 with IC50 values of 5.37 +/- 1.04 and 9.32 +/- 0.082 muM respectively and with concommotant down-regulation of phosphorylated-ERK-1/-2 expression. Compound 2 was an ineffective inhibitor of angiogenesis despite its structural homology to compound 1.

CONCLUSION

Compound 1 inhibited FGF-2 induced angiogenesis by binding to its cognate receptors and is an addition to the small number of natural product inhibitors of angiogenesis.

Inflammation and neuropeptides: the connection in diabetic wound healing

Abnormal wound healing is a major complication of both type 1 and type 2 diabetes, with nonhealing foot ulcerations leading in the worst cases to lower-limb amputation. Wound healing requires the integration of complex cellular and molecular events in successive phases of inflammation, cell proliferation, cell migration, angiogenesis and re-epithelialisation. A link between wound healing and the nervous system is clinically apparent as peripheral neuropathy is reported in 30-50% of diabetic patients and is the most common and sensitive predictor of foot ulceration. Indeed, a bidirectional connection between the nervous and the immune systems and its role in wound repair has emerged as one of the focal features of the wound-healing dogma. This review provides a broad overview of the mediators of this connection, which include neuropeptides and cytokines released from nerve fibres, immune cells and cutaneous cells. In-depth understanding of the signalling pathways in the neuroimmune axis in diabetic wound healing is vital to the development of successful wound-healing therapies.

Anti-angiogenic activity of sesterterpenes; natural product inhibitors of FGF-2-induced angiogenesis

Angiogenesis, the growth of new blood vessels from the pre-existing vasculature is of physiological and pathological importance. We have investigated the anti-angiogenic potential of two naturally occurring sesterterpenes, leucosesterterpenone (compound 1) and leucosterlactone (compound 2) isolated from the Himalayan plant Leucosceptrum canum and identified as having biological activity in preliminary screening. Compound 1 inhibited fibroblast growth factor-2-induced proliferation, migration in a wounding assay, chemotaxis and tube formation with small vessel (human dermal) and large vessel (bovine aortic) endothelial cells while compound 2 was largely inactive. Both compounds were also active in an in vivo angiogenic model using the chick chorioallantoic membrane. Neither compounds showed inhibitory activity in the absence of fibroblast growth factor-2. We were able to demonstrate in a binding assay that compounds 1 and 2 bound to the fibroblast growth factor-2 receptor-1 with IC(50) values of 1.4 +/- 0.956 and 132.47 +/- 7.90 muM, respectively, with a concomitant down regulation of phosphorylated ERK1/2 but did not bind to receptor-2. Compound 1 was less hydrophobic than compound 2 and this may contribute to its increased activity. Compound 1 is a new addition to the small number of inhibitors of fibroblast growth factor-2-induced angiogenesis. The compound was a specific inhibitor in that it had no effect on vascular endothelial growth factor or epithelial growth factor-induced angiogenesis. Since angiogenesis is essential for tumour development we conclude that these compounds may have potential as anti-tumour agents.

Analysis of carbohydrates and glycoconjugates by matrix-assisted laser desorption/ionization mass spectrometry: an update covering the period 2001-2002

This review is the second update of the original review on the application of MALDI mass spectrometry to the analysis of carbohydrates and glycoconjugates that was published in 1999. It covers fundamental aspects of the technique as applied to carbohydrates, fragmentation of carbohydrates, studies of specific carbohydrate types such as those from plant cell walls and those attached to proteins and lipids, studies of glycosyl-transferases and glycosidases, and studies where MALDI has been used to monitor products of chemical synthesis. Use of the technique shows a steady annual increase at the expense of older techniques such as FAB. There is an increasing emphasis on its use for examination of biological systems rather than on studies of fundamental aspects and method development and this is reflected by much of the work on applications appearing in tabular form.

Cheiradone: a vascular endothelial cell growth factor receptor antagonist

BACKGROUND

Angiogenesis, the growth of new blood vessels from the pre-existing vasculature is associated with physiological (for example wound healing) and pathological conditions (tumour development). Vascular endothelial growth factor (VEGF), fibroblast growth factor-2 (FGF-2) and epidermal growth factor (EGF) are the major angiogenic regulators. We have identified a natural product (cheiradone) isolated from a Euphorbia species which inhibited in vivo and in vitro VEGF- stimulated angiogenesis but had no effect on FGF-2 or EGF activity. Two primary cultures, bovine aortic and human dermal endothelial cells were used in in vitro (proliferation, wound healing, invasion in Matrigel and tube formation) and in vivo (the chick chorioallantoic membrane) models of angiogenesis in the presence of growth factors and cheiradone. In all cases, the concentration of cheiradone which caused 50% inhibition (IC50) was determined. The effect of cheiradone on the binding of growth factors to their receptors was also investigated.

RESULTS

Cheiradone inhibited all stages of VEGF-induced angiogenesis with IC50 values in the range 5.20-7.50 microM but did not inhibit FGF-2 or EGF-induced angiogenesis. It also inhibited VEGF binding to VEGF receptor-1 and 2 with IC50 values of 2.9 and 0.61 microM respectively.

CONCLUSION

Cheiradone inhibited VEGF-induced angiogenesis by binding to VEGF receptors -1 and -2 and may be a useful investigative tool to study the specific contribution of VEGF to angiogenesis and may have therapeutic potential.

Chronic hyperglicemia and nitric oxide bioavailability play a pivotal role in pro-atherogenic vascular modifications

Diabetes is associated with accelerated atherosclerosis and macrovascular complications are a major cause of morbidity and mortality in this disease. Although our understanding of vascular pathology has lately greatly improved, the mechanism(s) underlying enhanced atherosclerosis in diabetes remain unclear. Endothelial cell dysfunction is emerging as a key component in the pathophysiology of cardiovascular abnormalities associated with diabetes. Although it has been established that endothelium plays a critical role in overall homeostasis of the vessels, vascular smooth muscle cells (vSMC) in the arterial intima have a relevant part in the development of atherosclerosis in diabetes. However, high glucose induced alterations in vSMC behaviour are not fully characterized. Several studies have reported that impaired nitric oxide (NO) synthesis and/or actions are often present in diabetes and endothelial dysfunction. Furthermore, although endothelial cells are by far the main site of vascular NO synthesis, vSMC do express nitric oxyde synthases (NOSs) and NO synthesis in vSMC might be important in vessel's function. Although it is known that vSMC contribute to vascular pathology in diabetes by their change from a quiescent state to an activated proliferative and migratory phenotype (termed phenotypic modulation), whether this altered phenotypic modulation might also involve alterations in the nitrergic systems is still controversial. Our recent data indicate that, in vivo, chronic hyperglycemia might induce an increased number of vSMC proliferative clones which persist in culture and are associated with increased eNOS expression and activity. However, upregulation of eNOS and increased NO synthesis occur in the presence of a marked concomitant increase of O(2-) production. Since NO bioavailabilty might not be increased in high glucose stimulated vSMC, it is tempting to hypothesize that the proliferative phenotype observed in cells from diabetic rats is associated with a redox imbalance responsible quenching and/or trapping of NO, with the consequent loss of its biological activity. This might provide new insight on the mechanisms responsible for accelerated atherosclerosis in diabetes.

Diabetic foot ulcers — a comprehensive review

As the incidence of diabetes mellitus is increasing globally, complications related to this endocrine disorder are also mounting. Because of the large number of patients, foot ulcers developing in the feet of diabetics have become a public health problem. The predisposing factors include abnormal plantar pressure points, foot deformities, and minor trauma. Vulnerable feet usually already have vascular insufficiency and peripheral neuropathy. The complex nature of these ulcers deserves special care. The most useful prognostic feature for healing remains the ulcer depth, ulcers heal poorly if they clearly involve underlying tendons, ligament or joints and, particularly, when gangrenous tissue is seen. Local treatment of the ulcer consists of repeated debridement and dressing. No 'miraculous' outcome is expected, even with innovative agents like skin cover synthetics, growth factors and stem cells. Simple surgery like split skin grafting or minor toe amputations may be necessary. Sophisticated surgery like flap coverages are indicated for younger patients. The merits of an intact lower limb with an abnormal foot have to be weighed against amputation and prosthesis in the overall planning of limb salvage or sacrifice. If limb salvage is the decision, additional means like oxygen therapy, and other alternative medicines, might have benefits. The off-loading of footwear should always be a major consideration as a prevention of ulcer formation.

Angiogenesis and chronic inflammation: cause or consequence?

Evidence has been gathered regarding the association between angiogenesis and inflammation in pathological situations. These two phenomena have long been coupled together in many chronic inflammatory disorders with distinct etiopathogenic origin, including psoriasis, rheumatoid arthritis, Crohn's disease, diabetes, and cancer. Lately, this concept has further been substantiated by the finding that several previously established non-inflammatory disorders, such as osteoarthritis and obesity, display both inflammation and angiogenesis in an exacerbated manner. In addition, the interplay between inflammatory cells, endothelial cells and fibroblasts in chronic inflammation sites, together with the fact that inflammation and angiogenesis can actually be triggered by the same molecular events, further strengthen this association. Therefore, elucidating the underlying cellular and molecular mechanisms that gather together the two processes is mandatory in order to understand their synergistic effect, and to develop new therapeutic approaches for the management of these disorders that cause a great deal of discomfort, disability, and in some cases death.

Emerging drugs for diabetic foot ulcers

Diabetic foot ulceration results from factors extrinsic to the foot such as repeated trauma, ischaemia and infection, as well as intrinsic factors that lead to impairment of wound healing. Intrinsic factors are less well understood, but include deficiency of growth factors, changes in extracellular matrix components with excess proteases, reduced fibroblast activity, cellular abnormalities, deficiencies of angiogenesis, nitric oxide abnormalities and hyperglycaemia. The scientific rationale of therapy is to correct both the external factors that cause diabetic foot ulcers and the internal factors that lead to impairment of wound healing. Current research is leading to new therapies that can be divided into the following classes: growth factors, skin substitutes, extracellular matrix proteins, stem cell therapy, gene therapy, protease inhibitors, angiogenesis stimulants, nitric oxide-releasing agents, adenosine agonists, immunostimulants, vasoactive compounds and granulating agents. These therapies should be considered when existing treatments to correct extrinsic factors have failed to heal ulceration in the diabetic foot.

Comparison of protective effects of aspirin, d-penicillamine and vitamin E against high glucose-mediated toxicity in cultured endothelial cells

This study compared the protective effects of three different anti-glycation compounds, aspirin, D-penicillamine and vitamin E, against high glucose and advanced glycation endproduct (AGE) mediated toxicity in cultured bovine aortic endothelial cells using two approaches. Their proliferation was assessed in culture in different concentrations of glucose (5.5-100 mmol/l) with and without these inhibitors. A monolayer of cultured endothelial cells was wounded and recovery at the wound site was measured following exposure to different concentrations of glucose with and without inhibitors. The ability of these compounds to protect cultured endothelial cells following exposure to bovine serum albumin-derived advanced glycation endproducts (BSA-AGE) was also studied. Addition of glucose to cultured endothelial cells inhibited their proliferation in a dose dependent manner. All three compounds protected against the anti-proliferative effects of high glucose, with vitamin E being the most effective. The migration of cultured endothelial cells following wounding was inhibited by increasing concentrations of glucose but was maintained in the presence of all three anti-glycation compounds with vitamin E, again giving the greatest protection. Vitamin E was also the most effective at protecting against the anti-proliferative effects of BSA-AGE. D-penicillamine was not as effective as vitamin E whereas aspirin offered no significant protection against AGE-induced cellular toxicity. Our studies suggest that compounds, such as vitamin E, with combined antiglycation and antioxidant properties offer maximum therapeutic potential in protection against high glucose and AGE-mediated cellular toxicity.