Erythropoietin Stimulates Wound Healing and Angiogenesis in Mice

A comprehensive review of capillary electrophoresis-based techniques for erythropoietin isoforms analysis

Different CE techniques have been used to analyze erythropoietin. These techniques have been shown to be effective in differentiating and quantifying erythropoietin isoforms, including natural and recombinant origins. This review provides a comprehensive overview of various capillary electrophoresis-based techniques used for the analysis of erythropoietin isoforms. The importance of erythropoietin in clinical practice and the necessity for the accurate analysis of its isoforms are first discussed. Various techniques that have been used for erythropoietin isoform analysis are then described. The main body of the review focuses on the different capillary electrophoresis-based methods that have been developed for erythropoietin isoform analysis, including capillary zone electrophoresis and capillary isoelectric focusing. The advantages and drawbacks of each method as well as their applications are discussed. Suggestions into the future directions of the area are also described.

Efficacy of erythropoietin for wound healing: A systematic review of the literature

Objectives

To systematically review the available literature on the efficacy of erythropoietin for wound healing in human patients.

Design

The review was reported following Preferred Reporting Items for Systematic Reviews and Meta-Analysis guidelines. A descriptive-analytical method was used to analyse and integrate review findings.

Data sources

A primary search of electronic databases was performed using a combination of search terms related to the following areas of interest: ‘efficacy’, ‘erythropoietin’ and ‘wound healing’. A secondary search of the grey literature was conducted in addition to checking the reference list of included studies and review papers.

Results

Seven distinct studies involving 150 patients met the inclusion criteria for the review. The included studies suggest that topical and subcutaneous application of erythropoietin improves the wound healing process via faster re-epithelialization and reducing wound area and depth.

Conclusions

There were a limited number of studies and a great degree of heterogeneity of evidence due to differences in the course of concomitant illness, wound aetiology, and the time and dosing regimens adopted. Further research adopting validated and consistent outcome measures is recommended to determine the efficacy and safety of erythropoietin for wound healing.

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Topical and subcutaneous application of erythropoietin improves the wound healing process in human patients.

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Topical and subcutaneous application of erythropoietin contributes to reducing wound area and depth in human patients.

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Topical and subcutaneous application of erythropoietin has the potential to prevent wounds from becoming chronic.

Regenerative Properties of Recombinant Human Erythropoietin in the Wound Healing

BACKGROUND: Erythropoietin (EPO) is the main stimulator of erythropoiesis, but EPO also has non-hematopoietic effects. The recent data show the positive effects of EPO on tissue regeneration. AIM: This review aims to know highlights the pathophysiological mechanisms of EPO at different stages of tissue regeneration, and possible clinical applications in wound healing. METHODS: A review of the literature considering reviews, clinical studies, original papers, and articles from electronic data has been used. RESULTS: Analysis of animal studies and several clinical trials using EPO in context of wound healing revealed that EPO has a positive effect on all stages of regeneration process and may be a promising therapeutic strategy for the treatment of chronic wounds. CONCLUSION: An improved understanding of the functions and regulatory mechanisms of EPO in the context of wound healing may lead to new considerations of this growth hormone for its regular clinical application in patients.

Effect of freeze drying on stability, thermo-responsive characteristics, and in vivo wound healing of erythropoietin-loaded trimethyl chitosan/glycerophosphate hydrogel

Erythropoietin (EPO) was successfully incorporated into a bioadhesive thermosensitive hydrogel based on trimethyl chitosan (TMC)/β-glycerophosphate (GP) for prevention and treatment of oral mucositis in cancerous patients. The aim of the present study was to evaluate the effect of freeze drying on thermo-responsive property of the hydrogel and structural stability of the loaded protein. The freeze-dried EPO-loaded hydrogel were characterized using various methods. Gelation property by rheological analysis, EPO aggregation in formulations by sodium dodecyl sulfate polyacrylamide gel electrophoresis (SDS-PAGE), protein secondary structure by far ultraviolet-circular dichroism (CD), and the antigenic activity of EPO with ELISA techniques. The healing effects of the freeze-dried formulation was also investigated in Sprague-Dawley rats with chemotherapy-induced mucositis and compared with freshly prepared mixture. Finally, the retention time of the gel in the oral cavity was assessed in healthy volunteers. SDS-PAGE, CD, and ELISA confirmed the stability of conformational structure of loaded and released EPO. Severity of mucositis was markedly reduced in animals treated with freeze-dried EPO hydrogel; whereas the group received normal saline did not show any significant healing. EPO salvia level was decreased rapidly following EPO solution compared to the gel application. Approximately, 40% of EPO was maintained on the buccal areas in patients receiving the hydrogel system after 30 min. Therefore, the TMC/GP could preserve EPO stability after freeze drying and has the potential in the treatment of oral mucositis and other oral or subcutaneous wounds.

Effects of dimethyloxalylglycine on wound healing of palatal mucosa in a rat model

Background

Rapid wound healing of oral soft tissue may reduce the opportunity of infection and discomfort of patients. Previous studies have demonstrated that enhancement of angiogenesis is an effective way to accelerate wound repair. In this study, to enhance angiogenesis and healing of palatal wounds, dimethyloxalylglycine (DMOG) was applied to a rat palatal wound model. DMOG is known to inhibit oxygen-dependent degradation of hypoxia inducible factor-1 alpha (HIF-1α), which can lead to up-regulation of angiogenesis markers, favoring wound repair. We also evaluated the effects of DMOG on cell migration and HIF-1α expression of rat palatal (RP) cells. Furthermore, mRNA and protein expression of vascular endothelial growth factor (VEGF) were analyzed in DMOG-treated RP cells.

Methods

Primary cultures of rat palatal (RP) cells were obtained from Sprague–Dawley (SD) rats. Effects of DMOG on cell viability and migration of RP cells were evaluated by using a formazan and culture insert, respectively. VEGF mRNA was observed by real-time PCR, and VEGF and HIF-1α proteins were detected by Western blotting. For the animal study, excisional wounds, 3 mm in diameter, were made at the central part of the palate of SD rats. DMOG with hyaluronic acid ointment was topically applied three times during 1 week, and then wound closures were quantitated photographically and histologically.

Results

DMOG was cytotoxic to RP cells at concentrations higher than 2 mM and did not affect cell migration at non-cytotoxic concentrations. mRNA and protein expression of VEGF were significantly stimulated by DMOG treatment. The protein level of HIF-1α was also stabilized in RP cells by DMOG. In the animal study, groups treated with 1 mg/ml DMOG showed an increase of rat palatal wound contractures.

Conclusions

DMOG enhanced wound healing of rat palatal mucosa, which was likely due to the angiogenic effect of the agent.

Erythropoietin, a novel repurposed drug: an innovative treatment for wound healing in patients with diabetes mellitus

Developing a new drug is expensive: the cost of going from bench to bedside is about $US1 billion. Therefore, the repurposing of an approved drug is potentially rewarding because it expands the drug's existing therapeutic profile and preempts additional development costs. As the safety profile of a repurposed drug is already well known, any new investigations could then focus on its efficacy and other therapeutic benefits. Recombinant erythropoietin (EPO) is a potential candidate for repurposing because the results of numerous studies have shown that systemic and topical EPO is therapeutically beneficial when it is administered to healthy and diabetic animals with acute and chronic skin wounds and burns. Moreover, the molecular mechanisms of EPO's actions have been elucidated: EPO acts on those nonhematopoietic cells which are involved in the innate immune response where it promotes cellular proliferation and differentiation, exerts its cytoprotective actions, and inhibits apoptosis. In this review, the mechanism of EPO's action in skin wound healing is reviewed, and its potential for treating acute and chronic skin wounds and stimulating tissue regeneration in diabetic patients is discussed.

Evaluation of the potentials of autologous blood injection for healing in diabetic foot ulcers

Healing is a complex multifactorial process, hence it is not easy to be studied accurately. In this paper we tried to demonstrate the potentials of application of autologous blood by injection into the raw areas and ulcers of three diabetic patients using their blood as an alternative to synthesized and cultured stem cells or growth factors. It was found that a natural easily obtained blood can be used to enrich the media of the wound. Also it was applicable in relation to its cost-effectiveness as well as availability. The healing process was accelerated in the injected side more than the non-injected one.

The nonhematopoietic effects of erythropoietin in skin regeneration and repair: from basic research to clinical use

Erythropoietin (EPO) is the main regulator of red blood cell production but there exists also a variety of nonhematopoietic properties. More recent data show that EPO is also associated with the protection of tissues suffering from ischemia and reperfusion injury as well as with improved regeneration in various organ systems, in particular the skin. This review highlights the mechanisms of EPO in the different stages of wound healing and the reparative processes in the skin emphasizing pathophysiological mechanisms and potential clinical applications. There is clear evidence that EPO effectively influences all wound-healing phases in a dose-dependent manner. This includes inflammation, tissue, and blood vessel formation as well as the remodeling of the wound. The molecular mechanism is predominantly based on an increased expression of the endothelial and inducible nitric oxide (NO) synthase with a consecutive rapid supply of NO as well as an increased content of vascular endothelial growth factor (VEGF) in the wound. The improved understanding of the functions and regulatory mechanisms of EPO in the context of wound-healing problems and ischemia/reperfusion injury, especially during flap surgery, may lead to new considerations of this growth hormone for its regular clinical application in patients.

Erythropoietin improves the healing of skin necrosis resulting from Doxorubicin extravasation in a rat model

BACKGROUND

Doxorubicin is an antineoplastic agent that causes skin necrosis when extravasated. Various agents have been tried to reduce tissue damage owing to extravasation. Erythropoietin (EPO) is an obligatory growth factor for red blood cells and has beneficial effects on wound healing.

OBJECTIVE

The aim of this study was to test the hypothesis that local EPO injection can prevent and improve healing of necrosis at the doxorubicin injection site in rats.

METHODS

We used 31 female Sprague-Dawley rats. The dorsal area of each rat was shaved, and 2 mg of doxorubicin in 0.5 mL saline was injected intradermally. The rats were then divided into 3 groups: control; control with intradermal injection of saline; and treatment, which received an intradermal injection of EPO. EPO in saline was injected into 4 quadrants of the same site where doxorubicin was injected 1 hour before. The rats were monitored and the area of each ulcer was measured. Skin biopsies were excised at the end of 4 weeks using anesthetic pentobarbital. Inflammation, edema, epithelization, neovascularization, necrosis, fibroblast proliferation, and collagen synthesis were evaluated and compared between groups.

RESULTS

The average areas of the lesions were significantly smaller in the EPO-injected rats (P = 0.03). The histopathologic evaluation revealed that the scores for epithelization, neovascularization, fibroblast proliferation, and collagen synthesis were higher (P < 0.001, P < 0.001, P = 0.002, and P = 0.04, respectively) and the score for necrosis was lower (P < 0.001) in the EPO-injected group than in both the saline-injected and control groups.

CONCLUSIONS

In this study using female Sprague-Dawley rats, EPO treatment improved the healing of skin necrosis caused by doxorubicin injection. This finding may lead to a new therapeutic approach for the management of skin necrosis caused by doxorubicin extravasation.

Fibronectin potentiates topical erythropoietin-induced wound repair in diabetic mice

Diabetes mellitus disrupts all phases of the wound repair cascade and leads to development of chronic wounds. We previously showed that topical erythropoietin (EPO) can promote wound repair in diabetic rats. Fibronectin (FN) has a critical role throughout the process of wound healing, yet it is deficient in wound tissues of diabetic patients. Therefore, we investigated the effect of topical treatment of both EPO and FN (EPO/FN) on wound repair in diabetic mice. Full-thickness excisional skin wounds in diabetic and nondiabetic mice were treated with a cream containing vehicle, EPO, FN, or EPO/FN. We assessed the rate of wound closure, angiogenesis, apoptosis, and expression of inflammatory cytokines, endothelial nitric oxide synthase (eNOS) and β1-integrin, in the wound tissues. We also investigated the effect of EPO, FN, and EPO/FN on human dermal microvascular endothelial cells and fibroblasts cultured on fibrin-coated plates, or in high glucose concentrations. EPO/FN treatment significantly increased the rate of wound closure and this effect was associated with increased angiogenesis, increased eNOS and β1-integrin expression, and reduced expression of inflammatory cytokines and apoptosis. Our findings show that EPO and FN have an additive effect on wound repair in diabetic mice.

Local erythropoietin and endothelial progenitor cells improve regional cardiac function in acute myocardial infarction

Background

Expanded endothelial progenitor cells (eEPC) improve global left ventricular function in experimental myocardial infarction (MI). Erythropoietin beta (EPO) applied together with eEPC may improve regional myocardial function even further by anti-apoptotic and cardioprotective effects. Aim of this study was to evaluate intramyocardial application of eEPCs and EPO as compared to eEPCs or EPO alone in experimental MI.

Methods and Results

In vitro experiments revealed that EPO dosed-dependently decreased eEPC and leukocyte apoptosis. Moreover, in the presence of EPO mRNA expression in eEPC of proangiogenic and proinflammatory mediators measured by TaqMan PCR was enhanced. Experimental MI was induced by ligation and reperfusion of the left anterior descending coronary artery of nude rats (n = 8-9). After myocardial transplantation of eEPC and EPO CD68+ leukocyte count and vessel density were enhanced in the border zone of the infarct area. Moreover, apoptosis of transplanted CD31 + TUNEL + eEPC was decreased as compared to transplantation of eEPCs alone. Regional wall motion of the left ventricle was measured using Magnetic Resonance Imaging. After injection of eEPC in the presence of EPO regional wall motion significantly improved as compared to injection of eEPCs or EPO alone.

Conclusion

Intramyocardial transplantation of eEPC in the presence of EPO during experimental MI improves regional wall motion. This was associated with an increased local inflammation, vasculogenesis and survival of the transplanted cells. Local application of EPO in addition to cell therapy may prove beneficial in myocardial remodeling.

Comparison of the effects of collagenase and extract of Centella asiatica in an experimental model of wound healing: an immunohistochemical and histopathological study

In this study, we compared the effects of collagenase and Centella asiatica in the rat model. Twenty-seven female rats were divided into three groups, and two full-thickness wounds were made for each animal. Collagenase ointment was applied topically to Group I and C. asiatica ointment to Group II rats. In Group III, no treatment was applied. On the third day of treatment, wounds on the left side of three animals of each group were excised. On the fifth and eighth day of the treatments, the same procedure was performed for the remaining animals. Indirect immunohistochemical examination was performed to detect transforming growth factor beta (TGF)-beta, endothelial and inducible nitric oxide synthase (eNOS and iNOS), vascular endothelial growth factor, TGF-alpha, laminin, fibronectin, collagen I, and interleukin-1beta. According to the measurements of the wound areas and wound healing periodo, collagenase was superior to the control group. Immunohistochemical examinations showed strong (+++) iNOS and TGF-beta immunoreactivities in C. asiatica group. eNOS immunoreactivity was moderate (++) in this group. For the collagenase group, iNOS, eNOS, and TGF-beta immunoreactivities were moderate (++). In the collagenase group, while TGF-beta and iNOS immunoreactivities were weaker, laminin and fibronectin reactivities were stronger than in C. asiatica and control groups. Collagenase was superior to C. asiatica according to the immunohistochemical findings. Collagenase ointment significantly improves the quality of wound healing and scar formation and is a more appropriate treatment choice than extract of C. asiatica in the early stages of the wound healing process.

Nonerythropoietic tissue protective compounds are highly effective facilitators of wound healing

Erythropoietin (EPO) is a type I cytokine that utilizes different receptor isoforms either to maintain hematopoiesis or protect against injuries that arise from widely diverse etiologies. EPO also facilitates healing by reducing inflammation and mobilizing endothelial progenitor cells to participate in restorative neoangiogenesis, but it is unclear which EPO receptor isoform is responsible for healing and whether this receptor use varies according to the type of wound. In the present studies carried out in the rat, we have utilized receptor-selective derivatives of EPO to determine which receptor type operates in (i) a nonischemic wound (skin punch biopsy), (ii) a permanently ischemic wound (raised musculocutaneous flap), (iii) an intermittent ischemic reperfusion wound (pressure or decubitus ulcer), or (iv) wounds complicated by infection (cecal ligation and perforation). Using these models, we demonstrate that nonerythropoietic tissue protective compounds administered immediately following injury limit wound size and accelerate eschar closure independent of wound type. Moreover, in a model of peritonitis-induced adhesions, daily administration of the nonerythropoietic derivative carbamyl-EPO (10 microg/kg-bw) was associated with significantly lower serum TNFalpha concentration, illness scores, increased survival, as well as decreased adhesion formation. These results confirm that wound healing is mediated by the tissue protective receptor isoform and argue that nonerythropoietic tissue protective molecules constitute promising new.

Erythropoietin reduces lipopolysaccharide-induced cell Damage and midkine secretion in U937 human histiocytic lymphoma cells

INTRODUCTION

Erythropoietin (EPO) is a haematopoietic stimulatory protein that is used to treat anaemia in patients on dialysis. In addition, EPO has been shown to have anti-inflammatory properties, which may be important as dialysis patients tend to exist within a chronic, low-grade inflammatory state, and tend to be more susceptible to infections. It has been suggested that EPO has direct immunomodulatory potency on monocytes/macrophages.

METHODS

In this study, we aimed to clarify the effects of EPO during the inflammatory processes in human mononuclear phagocytic cells by monitoring the secretion of the following cytokines; midkine, tumour necrosis factor alpha (TNF-alpha), and interleukin-6 (IL-6). For this purpose, U937 human histiocytic lymphoma cell lines were used. Time-dependent effects of varying doses of EPO (0.1 to 50 IU/ml) treatment during lipopolysaccharide (LPS)-mediated cytotoxicity was measured by 3-[4,5-dimethylthiazol-2-yl]-2,5 diphenyltetrazolium bromide test. LPS-stimulated midkine secretion was measured immunohistochemically and quantification of TNF-alpha, IL-6 and midkine secretion was achieved by ELISA.

RESULTS

EPO treatment prevented the direct toxic effects of LPS on the U937 cells. TNF-alpha, IL-6 and midkine secretions were found to increase in the U937 cells in response to LPS treatment. Interleukin-6 response was varied in a doseand time-dependent manner.

CONCLUSION

Treatment with EPO significantly inhibits the LPS-induced secretion of midkine and TNF-alpha regardless of the dosage. The data presented here provide the first evidence to indicate that EPO treatment directly reverses some of the cytotoxic and secretory effects of LPS in mononuclear cells. Inhibition of midkine secretion might be responsible for the anti-inflammatory role of EPO.

New insights into nephrogenic systemic fibrosis

Nephrogenic systemic fibrosis is a new disorder reported almost exclusively in patients who have renal insufficiency and are exposed to contrast media formulated with gadolinium. High morbidity and mortality are associated with this severely disabling and painful condition. The acute phase begins upon exposure to gadolinium contrast media, characterized by a systemic inflammatory response involving iron mobilization, and then as a progressive, chronic phase in which fibrosis develops. Proposed is a unifying model of cumulative risk factors in which the interplay of systemic inflammation and stimulated hematopoietic environment associated with hyperparathyroidism and erythropoietin may tie to a common pathogenic mechanism of fibrogenesis. Because there are no uniformly effective interventions to treat nephrogenic systemic fibrosis other than successful renal transplantation, prevention by avoiding gadolinium contrast media in patients with chronic kidney disease is vital. On the basis of suspected pathogenesis, it is also reasonable to limit erythropoietin and iron therapy to dosages ensuring recommended targets and adequately control hyperparathyroidism. Herein is reviewed what is currently known about this subject.

The expression patterns of vascular endothelial growth factor and thrombospondin 2 after corneal alkali burn

The aim of the investigation was to explore the expression patterns of VEGF and TSP2 after corneal alkali burn in vivo. After the model of corneal alkali burn was established in mice, the expression levels of VEGF and TSP2 were determined by immunohistochemistry (IHC), RT-PCR, image analysis and statistical evaluation. Compared with control group, the expression level of VEGF increased significantly at 6h after alkali burn and reached its maximum at 12h. Then, it increased again till the second peak appeared at 96h and 192h. The VEGF-positive reaction mainly gathered in the stroma of cornea. On the other hand, the expression of TSP2 enhanced at 3h and attained two peaks at 6h and 96h, respectively, with the process of wound healing. TSP2 was expressed mainly in the base of epithelial layer. The expression patterns of VEGF and TSP2 reflect the complicated interaction with many factors including promoted and inhibited vascularization in vivo. Moreover, it might provide a novel method for controlling vascular hyperplasia in future clinical work according to the data of VEGF and TSP2.

Soft tissue wounds and principles of healing

Wound healing is a complex interchange, orchestrated between cellular components that play their respective parts signaled by and mediated by different cellular instruments of healing. When healing is performed well, the final product is a thing of beauty. When healing is delayed, interrupted, or excessive, then unsightly scars of chronic painful wounds that are frustrating to the patient and physician occur.

MicroRNA in Cutaneous Wound Healing: A New Paradigm

Repair of a defect in the human skin is a highly orchestrated physiological process involving numerous factors that act in a temporally resolved synergistic manner to re-establish barrier function by regenerating new skin. The inducible expression and repression of genes represents a key component of this regenerative process. MicroRNAs (miRNAs) are approximately 22-nucleotide-long endogenously expressed non-coding RNAs that regulate the expression of gene products by inhibition of translation and/or transcription in animals. miRNAs play a key role in skin morphogenesis and in regulating angiogenesis. The vascular endothelial growth factor signaling path seems to be under repressor control by miRNAs. Mature miRNA-dependent mechanisms impair angiogenesis in vivo. It is critically important to recognize that the understanding of cutaneous wound healing is incomplete without appreciating the functional significance of wound-induced miRNA. Ongoing work in our laboratory has led to the observation that the cutaneous wound healing process involves changes in the expression of specific miRNA at specific phases of wound healing. We hypothesize that dysregulation of specific miRNA is critical in derailing the healing sequence in chronic problem wounds. If tested positive, this hypothesis is likely to lead to completely novel diagnostic and therapeutic strategies for the treatment of problem wounds.