Potential therapeutic effects of topical recombinant human erythropoietin on burn wound healing: A preliminary randomized double-blind controlled clinical trial

BACKGROUND

Burn injuries can cause significant mortality and morbidity. This study aimed to evaluate the efficiency of topical recombinant human erythropoietin (rhEPO) on enhancing burn wound healing.

METHODS

In this randomized double-blind controlled clinical trial, we enrolled 40 participants aged 18 years and older who were referred to a burn center during the first 24 h of burning. The participants with no concurrent comorbidities had superficial and deep second-degree burns, no respiratory burns, no face and perineum burns, no keloid formation, or a healed, fully epithelialized, hypertrophic burn scar. Topical rhEPO or nitrofurazone/Vitamin A was administered every other day, and the patients were scheduled for follow-up visits to receive wound cleansing, debridement, and dressing changes. Burn wound healing response to treatment was measured as the study main outcome.

RESULTS

At the second follow-up visit, all parameters were significantly lower in the rhEPO group compared with the control group except for itchiness. The results of the next two follow-up sessions were also the same. The total value of the modified Vancouver Scar Scale (VSS) at days 5, 7, and 14 was significantly lower in the rhEPO group compared with the routine of care group. Trial Registry Date: 2022-03-02, Trial Registry number: IRCT20190810044500N23 CONCLUSIONS: The results of the present study suggested that topical rhEPO is a potential option in burn wounds and patient satisfaction, without causing intolerable side effects.

Microvascular Fragment-Loaded Platelet-Rich Plasma Dressing Promotes Cutaneous Wound Healing

Objective: Chronic wounds represent a considerable burden for the affected patients and the health care system. To overcome this problem, effective treatment strategies are urgently required. In this study, we tested a novel approach by combining platelet-rich plasma (PRP) and microvascular fragments (MVF) to create a prevascularized gel dressing. Approach: MVF were enzymatically isolated from the epididymal fat pads of transgenic green fluorescent protein (GFP)+ C57BL/6J donor mice. Subsequently, 5,000 MVF were suspended in 10 μL murine PRP as carrier and transferred into full-thickness skin wounds within dorsal skinfold chambers of C57BL/6J wild-type mice (PRP+MVF). Wound healing in comparison to empty wounds (control) and wounds filled with PRP alone was repeatedly analyzed throughout 14 days by means of stereomicroscopy, histology, and immunohistochemistry. Results: Planimetric assessment of the wound size over time revealed a significantly accelerated and improved healing of PRP+MVF-treated wounds when compared with PRP-treated and empty control wounds. These wounds also exhibited a significantly higher density of blood and lymph vessels, which originated from the GFP+ MVF isolates and effectively promoted granulation tissue formation inside the skin defects. Innovation: This study is the first to combine PRP and MVF for the improvement of wound healing. Conclusion: The combination of PRP and MVF represents a promising approach for the future treatment of wounds that do not heal spontaneously due to poor wound-healing conditions.

Evaluation of Preventive Role of Systemically Applied Erythropoietin after Tooth Extraction in a Bisphosphonate-Induced MRONJ Model

Background and Objectives: In this experimental study, the prophylactic effect of systemically administered erythropoietin (EPO) in medication-related osteonecrosis of the jaw (MRONJ) was evaluated. Materials and Methods: The osteonecrosis model was established using 36 Sprague Dawley rats. EPO was systemically applied before and/or after tooth extraction. Groups were formed based on the application time. All samples were evaluated histologically, histomorphometrically, and immunohistochemically. A statistically significant difference in new bone formation was observed between the groups (p < 0.001). Results: When new bone-formation rates were compared, no significant differences were observed between the control group and the EPO, ZA+PostEPO, and ZA+Pre-PostEPO groups (p = 1, 0.402, and 1, respectively); however, this rate was significantly lower in the ZA+PreEPO group (p = 0.021). No significant differences in new bone formation were observed between the ZA+PostEPO and ZA+PreEPO groups (p = 1); however, this rate was significantly higher in the ZA+Pre-PostEPO group (p = 0.009). The ZA+Pre-PostEPO group demonstrated significantly higher intensity level in VEGF protein expression than the other groups (p < 0.001). Conclusions: Administering EPO two weeks pre-extraction and continuing EPO treatment for three weeks post-extraction in ZA-treated rats optimized the inflammatory reaction, increased angiogenesis by inducing VEGF, and positively affected bone healing. Further studies are needed to determine the exact durations and doses.

Relation Between Gender and Concomitant Medications With Erythropoietin-Treatment on Wound Healing in Burn Patients. Post Hoc Subgroup-Analysis of the Randomized, Placebo-Controlled Clinical Trial “EPO in Burns”

Burns are leading causes of mortality and morbidity, including prolonged hospitalization, disfigurement, and disability. Erythropoietin (EPO) is a well-known hormone causing erythropoiesis. However, EPO may play a role in healing acute and chronic wounds due to its anti-inflammatory and pro-regenerative effects. Therefore, the large, prospective, placebo-controlled, randomized, double-blind, multi-center clinical trial “EPO in Burns” was initiated to investigate the effects of EPO versus placebo treatment in severely burned patients. The primary endpoint of “EPO in Burns” was defined as the time elapsed until complete re-epithelialization of a defined split skin graft donor site. Additional analyses of post hoc defined subgroups were performed in view of the primary endpoint. The verum (n 45) and control (n 39) groups were compared with regard to the time it took for study wounds (a predefined split skin graft donor site) to reach the three stages of wound healing (re-epithelialization levels). In addition, the effects of gender (females n 18) and concomitant medications insulin (n 36), non-steroidal anti-inflammatory drugs (NSAIDs) (n 41), and vasopressor agents (n 43) were tested. Life tables were used to compare study groups (EPO vs. placebo) within subgroups. The Cox regression model was applied to evaluate interactions between the study drug (EPO) and concomitant medications for each re-epithelialization level. Using our post hoc defined subgroups, we observed a lower chance of wound healing for women compared to men (in terms of hazard ratio: hr^100%: 5.984 [95%-CI: (0.805–44.490), p = 0.080]) in our study population, regardless of the study medication. In addition, results indicated an earlier onset of re-epithelialization in the first days of EPO treatment (EPO: 10% vs. Placebo: 3%). Moreover, the interpretation of the hazard ratio suggested EPO might have a positive, synergistic effect on early stages of re-epithelialization when combined with insulin [hr^50%: 1.307 (p = 0.568); hr^75%: 1,199 (p = 0.715)], as well as a stabilizing effect on critically ill patients [reduced need for vasopressors in the EPO group (EPO: 44% vs. Placebo 59%)]. However, additional high-quality data from clinical trials designed to address these endpoints are required to gain further insight into these effects.

Mupirocin Promotes Wound Healing by Stimulating Growth Factor Production and Proliferation of Human Keratinocytes

Mupirocin has been reported for its role in the treatment of infected wounds through its antibacterial activity, however the role of mupirocin in promoting wound healing via alternative mechanisms has not been extensively evaluated. This study aimed to evaluate the potential effect of mupirocin to promote wound healing, not only through its antibacterial activity but by increasing human keratinocyte proliferation and growth factor production. In the scratch assay, using human keratinocytes (HaCat), mupirocin (at 0.1 and 0.2 mM) significantly increased wound closure compared to the vehicle control. Cell viability, measured from the scratch assay, verified the increase in wound closure, where mupirocin at both concentrations showed higher cell viability compared to the vehicle control. In addition, mupirocin at 0.1 mM significantly stimulated the production of hepatocyte growth factor and M-CSF in HaCat cells, whereas at 0.2 mM, PDGF-AA and EPO were increased. The findings of this study suggest that mupirocin, which is commonly used as an antibacterial agent for the treatment of wounds, also facilitates the wound healing process by stimulating the proliferation of human keratinocytes and enhancing the production of several growth factors involved in wound healing. This is the first report on the effect of mupirocin on growth factors expressed by human keratinocytes as well as the stimulation of keratinocyte proliferation.

Engineering microparticles based on solidified stem cell secretome with an augmented pro-angiogenic factor portfolio for therapeutic angiogenesis

Tissue (re)vascularization strategies face various challenges, as therapeutic cells do not survive long enough in situ, while the administration of pro-angiogenic factors is hampered by fast clearance and insufficient ability to emulate complex spatiotemporal signaling. Here, we propose to address these limitations by engineering a functional biomaterial capable of capturing and concentrating the pro-angiogenic activities of mesenchymal stem cells (MSCs).

In particular, dextran sulfate, a high molecular weight sulfated glucose polymer, supplemented to MSC cultures, interacts with MSC-derived extracellular matrix (ECM) components and facilitates their co-assembly and accumulation in the pericellular space. Upon decellularization, the resulting dextran sulfate-ECM hybrid material can be processed into MIcroparticles of SOlidified Secretome (MIPSOS). The insoluble format of MIPSOS protects protein components from degradation, while facilitating their sustained release. Proteomic analysis demonstrates that MIPSOS are highly enriched in pro-angiogenic factors, resulting in an enhanced pro-angiogenic bioactivity when compared to naïve MSC-derived ECM (cECM). Consequently, intravital microscopy of full-thickness skin wounds treated with MIPSOS demonstrates accelerated revascularization and healing, far superior to the therapeutic potential of cECM. Hence, the microparticle-based solidified stem cell secretome provides a promising platform to address major limitations of current therapeutic angiogenesis approaches.

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Dextran sulfate assembles with mesenchymal stem cell secretome.

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As a result, microparticles of solidified stem cell secretome (MIPSOS) are formed.

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The insoluble MIPSOS format protects proteins from premature degradation.

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MIPSOS are enriched in pro-angiogenic factors and exhibit gradual release kinetics.

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MIPSOS demonstrate superior pro-angiogenic properties and thus therapeutic potential.

Topical Application of Antrodia cinnamomea Ointment in Diabetic Wound Healing

The number of diagnosed diabetic patients is increasing worldwide. Many people with diabetes develop wounds that are slow to, or never, heal, which can lead to serious health issues. Diabetes causes long-term excessive blood glucose buildup in human body, which leads to an over-reactive inflammatory response and excessive oxidative stress. As a result, varied wound healing effects were observed according to different circumstances and stage of healing. We used two diabetic wound animal models to analyze the wound healing effect of Antrodia cinnamomea ointment in either topical application and/or oral administration, and explored its mechanism by Western blot analysis. The results showed that topical Antrodia cinnamomea treatment can significantly promote wound healing. The increased expressions of angiopoietin 1 and angiopoietin 2 protein and reduction of CD68 expression were found around wound area. Simultaneous treatment of oral and topical Antrodia cinnamomea ointment did not show an accelerated healing effect in our animal model. This study is the first report to demonstrate the effect of topical application of Antrodia cinnamomea ointment on diabetic wounds healing, and its relationship with angiogenesis. This may also open a new field for future development and application of Taiwan Antrodia cinnamomea.

Adipose Tissue-Derived Microvascular Fragments From Male and Female Fat Donors Exhibit a Comparable Vascularization Capacity

Adipose tissue-derived microvascular fragments (MVF) represent effective vascularization units for tissue engineering. Most experimental studies exclusively use epididymal fat tissue of male donor mice as a source for MVF isolation. However, in future clinical practice, MVF-based approaches may be applied in both male and female patients. Therefore, we herein compared the vascularization capacity of MVF isolated from the epididymal and peri-ovarian fat tissue of male and female donor mice. Freshly isolated MVF from male and female donors did not differ in their number, length distribution, viability and cellular composition. After their assembly into spheroids, they also exhibited a comparable in vitro sprouting activity. Moreover, they could be seeded onto collagen-glycosaminoglycan matrices, which were implanted into full-thickness skin defects within mouse dorsal skinfold chambers. Repetitive intravital fluorescence microscopy as well as histological and immunohistochemical analyses revealed a comparable vascularization and incorporation of implants seeded with MVF of male and female origin. Taken together, these findings demonstrate that the vascularization capacity of MVF is not gender-specific.

Evaluation of topical erythropoietin application on the healing outcome of gingival graft recipient site; a randomized controlled clinical trial

Background

Free gingival graft (FGG) is a highly predictable method to increase the width of keratinized gingiva. Various materials have been reported to accelerate the wound healing process. Considering the positive effect of EPO on dermal wound healing this study aimed to investigate the effects of EPO on the rate of healing and degree of inflammation in free gingival grafts.

Methods

Seventeen patients with bilateral lack of keratinized gingiva in mandible were selected for this clinical trial. The surgical intervention was performed after phase I periodontal therapy.

Recipient site was prepared apical to the mucogingival line, and FGG was harvested from the palate. Before graft placement, the test side and control side were treated with 1 ml of EPO 4000 IU/ml and distilled water, respectively, for 2 min. On days 7, 14, 21, 28, 60, and 90 after surgery, the grafted sites were examined by blinded observers to compare the healing and inflammation of the areas.

Results

All the 17 patients completed the surgeries and follow-up examinations. Direct examination revealed significantly better healing in EPO group only on the 28th day. Assessment of the photographs showed a significant value in favor of the test group at some other time points as well. The EPO group demonstrated less inflammation, which was statistically significant in many time points. The graft area was 80.88 ± 30.21 mm² and 71.35 ± 15.62 mm² in the EPO and control groups, respectively. The difference was not significant, though.

Conclusions

Topical application of erythropoietin can accelerate the healing of gingival grafts and reduce the inflammation during healing period. The final graft outcome, nevertheless, does not seem to be influenced by EPO.

Trial registration This was a split-mouth randomized controlled clinical trial (IRCT201201278830N1). The first registration date: 2016-10-22

Vascularization of Microvascular Fragment Isolates from Visceral and Subcutaneous Adipose Tissue of Mice

Background:

Adipose tissue-derived microvascular fragments (MVF) represent effective vascularization units for tissue engineering. Most experimental studies in rodents exclusively use epididymal adipose tissue as a visceral fat source for MVF isolation. However, in future clinical practice, MVF may be rather isolated from liposuctioned subcutaneous fat tissue of patients. Therefore, we herein compared the vascularization characteristics of MVF isolates from visceral and subcutaneous fat tissue of murine origin.

Methods:

MVF isolates were generated from visceral and subcutaneous fat tissue of donor mice using two different enzymatic procedures. For in vivo analyses, the MVF isolates were seeded onto collagen-glycosaminoglycan scaffolds and implanted into full-thickness skin defects within dorsal skinfold chambers of recipient mice.

Results:

By means of the two isolation procedures, we isolated a higher number of MVF from visceral fat tissue when compared to subcutaneous fat tissue, while their length distribution, viability and cellular composition were comparable in both groups. Intravital fluorescence microscopy as well as histological and immunohistochemical analyses revealed a significantly reduced vascularization of implanted scaffolds seeded with subcutaneous MVF isolates when compared to implants seeded with visceral MVF isolates. Light and scanning electron microscopy showed that this was due to high amounts of undigested connective tissue within the subcutaneous MVF isolates, which clogged the scaffold pores and prevented the interconnection of individual MVF into new microvascular networks.

Conclusion:

These findings indicate the need for improved protocols to generate connective tissue-free MVF isolates from subcutaneous fat tissue for future translational studies.

Effects of Extracorporeal Shock Waves on Microcirculation and Angiogenesis in the in vivo Wound Model of the Diver Box

INTRODUCTION

Extracorporeal shock waves (ESWs) have been shown to have a positive effect on skin wound healing; however, little is known on the regeneration of the microcirculation and angiogenesis as well as the different application modes.

METHODS

A total of 40 BALB/c mice were provided with dorsal skin fold chambers and were divided into 3 therapy groups (n = 30) and one control group (n = 10). The 3 therapy groups were treated with shock waves at different pulse rates (500-1,000 pulses/min) and application frequencies (day 0 and day 6 or day 0 only). Photographic documentation and intravital microscopy were carried out on day 1, 2, 4, and 6 after wounding.

RESULTS

Using the newly developed Diver Box, shock waves could be applied in vivo without mechanical tissue damage. Shock wave therapy to skin wounds demonstrated to induce faster wound closure rates in the beginning than controls in groups with higher pulse rates and frequencies of the shock waves. Furthermore, the regeneration of microcirculation and perfusion in the healing skin was significantly improved after the application of, in particular, higher pulse rates as given by increased numbers of perfused capillaries and functional vessel density. The study of inflammation showed, especially in high-pulse ESW groups, higher leukocyte counts, and rolling leukocytes over time until day 6 as a response to the induction of inflammatory reaction after ESW application. Angiogenesis showed a marked increase in positive areas as given by sprouts, coils, and recruitments in all ESW groups, especially between days 4 and 6.

CONCLUSION

The major findings of this trial demonstrate that ESW therapy to skin wounds is effective and safe. This is demonstrated by the initially faster wound closure rate, but later the same wound closure rate in the treatment groups than in controls. Furthermore, during the regeneration of microcirculation and perfusion in the healing skin, a significant improvement was observed after the application of, in particular, higher ESW pulse rates, suggesting an ESW-related increase in nutrient and oxygen supply in the wound tissue.

Experimental Models to Study Skin Wound Healing with a Focus on Angiogenesis

A large number of models are now available for the investigation of skin wound healing. These can be used to study the processes that take place in a phase-specific manner under both physiological and pathological conditions. Most models focus on wound closure, which is a crucial parameter for wound healing. However, vascular supply plays an equally important role and corresponding models for selective or parallel investigation of microcirculation regeneration and angiogenesis are also described. In this review article, we therefore focus on the different levels of investigation of skin wound healing (in vivo to in virtuo) and the investigation of angiogenesis and its parameters.

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.

Systemic low-dose erythropoietin administration improves the vascularization of collagen-glycosaminoglycan matrices seeded with adipose tissue-derived microvascular fragments

Adipose tissue-derived microvascular fragments (MVF) are used as vascularization units in tissue engineering. In this study, we investigated whether the vascularization capacity of MVF can be improved by systemic low-dose erythropoietin (EPO) administration. MVF were isolated from the epididymal fat of donor mice and seeded onto collagen-glycosaminoglycan matrices, which were implanted into full-thickness skin defects within dorsal skinfold chambers of recipient mice. Both donor and recipient mice were treated daily with either EPO (500 IU/kg) or vehicle (0.9% NaCl). The implants were analyzed by stereomicroscopy, intravital fluorescence microscopy, histology, and immunohistochemistry. EPO-treated MVF contained a comparable number of proliferating Ki67⁺ but less apoptotic cleaved caspase-3⁺ endothelial cells when compared to vehicle-treated controls. Moreover, EPO treatment accelerated and improved the in vivo vascularization, blood vessel maturation, and epithelialization of MVF-seeded matrices. These findings indicate that systemic low-dose EPO treatment is suitable to enhance the viability and network-forming capacity of MVF.

Nanocomposite scaffolds for accelerating chronic wound healing by enhancing angiogenesis

Skin is the body's first barrier against external pathogens that maintains the homeostasis of the body. Any serious damage to the skin could have an impact on human health and quality of life. Tissue engineering aims to improve the quality of damaged tissue regeneration. One of the most effective treatments for skin tissue regeneration is to improve angiogenesis during the healing period. Over the last decade, there has been an impressive growth of new potential applications for nanobiomaterials in tissue engineering. Various approaches have been developed to improve the rate and quality of the healing process using angiogenic nanomaterials. In this review, we focused on molecular mechanisms and key factors in angiogenesis, the role of nanobiomaterials in angiogenesis, and scaffold-based tissue engineering approaches for accelerated wound healing based on improved angiogenesis.

Vascularization Strategies in the Prevention of Nonunion Formation

Delayed healing and nonunion formation are major challenges in orthopedic surgery, which require the development of novel treatment strategies. Vascularization is considered one of the major prerequisites for successful bone healing, providing an adequate nutrient supply and allowing the infiltration of progenitor cells to the fracture site. Hence, during the last decade, a considerable number of studies have focused on the evaluation of vascularization strategies to prevent or to treat nonunion formation. These involve (1) biophysical applications, (2) systemic pharmacological interventions, and (3) tissue engineering, including sophisticated scaffold materials, local growth factor delivery systems, cell-based techniques, and surgical vascularization approaches. Accumulating evidence indicates that in nonunions, these strategies are indeed capable of improving the process of bone healing. The major challenge for the future will now be the translation of these strategies into clinical practice to make them accessible for the majority of patients. If this succeeds, these vascularization strategies may markedly reduce the incidence of nonunion formation. Impact statement Delayed healing and nonunion formation are a major clinical problem in orthopedic surgery. This review provides an overview of vascularization strategies for the prevention and treatment of nonunions. The successful translation of these strategies in clinical practice is of major importance to achieve adequate bone healing.

Injectable thermosensitive chitosan/gelatin-based hydrogel carried erythropoietin to effectively enhance maxillary sinus floor augmentation in vivo

OBJECTIVE

Maxillary sinus floor augmentation (MSFA) is commonly used to increase the alveolar bone height in the posterior maxilla before implant placement. In the present study, we evaluated if the injectable thermosensitive chitosan/β-sodium glycerophosphate disodium salt hydrate/gelatin (CS/GP/GA) hydrogel carried erythropoietin (EPO) could enhance the new bone formation for MSFA in vivo.

METHODS

EPO-CS/GP/GA hydrogel was prepared by ionic crosslinking. Then, characteristics of EPO-CS/GP/GA were evaluated by morphology, injectable property and pH on the gelling time (GT). The release profile of EPO was evaluated by enzyme linked immunosorbent assay (ELISA), and effects of EPO on proliferation and osteoblastic differentiation of bone marrow stromal cells (BMSC) were analyzed by 3-[4,5-dimethylthiazol-2-yl]-2,5-diphenyl tetrazolium bromide (MTT) and reverse transcription quantitative real-time PCR (RT-qPCR), respectively. Finally, EPO-CS/GP/GA was injected into the maxillary sinus floor of the rabbit to test the potential application for MSFA.

RESULTS

Results showed that GT was decreased with the increase of pH value. The GT was 110±15s at pH 7.0. SEM images showed that the CS/GP/GA hydrogel had a sponge network structure. Results from ELISA assay revealed that the cumulative release of EPO from the EPO-CS/GP/GA hydrogel reached 67% at 4h, and 94% at 15 days. MTT assay showed that EPO within EPO-CS/GP/GA hydrogel could significantly promote proliferation of BMSCs compared to control group (p<0.001) . Results of RT-qPCR assays demonstrated that the expression of Sp7, Runx2, Col I and Alp were significantly increased from EPO-CS/GP/GA group compared to control group on day 14 (p<0.001). Importantly, EPO-CS/GP/GA hydrogel could significantly induce bone formation (81.98mm³) compared with control group (43.11mm³) after 12 weeks post-implantation in vivo. The calculation of thickness of mesenchymal condensation indicated that thickness of mesenchymal condensation was significantly increased from EPO-CS/GP/GA group (∼121.4μm) compared to control group (∼37μm) resulting in enhancing intramembranous ossification.

SIGNIFICANCE

The EPO-CS/GP/GA hydrogel provides a novel strategy for MSFA with a minimally invasive way.

The effect of erythropoietin on rat rotator cuff repair model: An experimental study

OBJECTIVES

The aim of this study was to determine whether erythropoietin (EPO) can enhance rotator cuff healing in rats as measured by histological analysis and biomechanical testing.

METHODS

A total of 72 rats were included in this study. In the control group (n = 24), repair was performed without EPO injection. In the local group (n = 24) EPO was injected in the repair site. In the systemic group (n = 24) EPO was administered as an intraperitoneal injection every day for 10 days after repair. Rats were euthanized on day 10 (n = 12 from each group) and day 28 (n = 12 from each group). Histopathological (n = 6) and biomechanical examinations (n = 6) were done.

RESULTS

Biomechanical results reveal that the maximum load to failure values of the early control group were statistically lower than those of the early systemic group (p = 0.006). Comparing the the total Bonar values histopathologically reveal that the early systemic group was statistically higher than those of the early local group (p = 0.043). The late control group was statistically higher than those of the late local group (p = 0.003) and the late systemic group (p = 0.034). The late systemic group was statistically higher than those of the late local group (p = 0.003).

CONCLUSIONS

EPO application had a positive effect biomechanically in the early euthanized group and histopathologically in the late euthanized group.

Nrf2 signaling and inflammation are key events in physical plasma-spurred wound healing

Wound healing is strongly associated with the presence of a balanced content of reactive species in which oxygen-dependent, redox-sensitive signaling represents an essential step in the healing cascade. Numerous studies have demonstrated that cold physical plasma supports wound healing due to its ability to deliver a beneficial mixture of reactive species directly to the cells.

Methods: We described a preclinical proof-of-principle-concept of cold plasma use in a dermal, full-thickness wound model in immunocompetent SKH1 mice. Quantitative PCR, Western blot analysis, immunohistochemistry and immunofluorescence were perfomed to evaluate the expression and cellular translocation of essential targets of Nrf2 and p53 signaling as well as immunomodulatory and angiogenetic factors. Apoptosis and proliferation were detected using TUNEL assay and Ki67 staining, respectively. Cytokine levels in serum were measured using bead-based multiplex cytokine analysis. Epidermal keratinocytes and dermal fibroblasts were isolated from mouse skin to perform functional knockdown experiments. Intravital fluorescence analysis was used to illustrate and quantified microvascular features.

Results: Plasma exerted significant effects on wound healing in mice, including the promotion of granulation and reepithelialization as a consequence of the migration of skin cells, the balance of antioxidant and inflammatory response, and the early induction of macrophage and neutrophil recruitment to the wound sites. Moreover, through an early and local plasma-induced p53 inhibition with a concomitant stimulation of proliferation, the upregulation of angiogenetic factors, and an increased outgrowth of new vessels, our findings explain why dermal skin repair is accelerated. The cellular redox homeostasis was maintained and cells were defended from damage by a strong modulation of the nuclear E2-related factor (Nrf2) pathway and redox-sensitive p53 signaling.

Conclusions: Although acute wound healing is non-problematic, the pathways highlighted that mainly the activation of Nrf2 signaling is a promising strategy for the clinical use of cold plasma in chronic wound healing.

Prevascularization of collagen-glycosaminoglycan scaffolds: stromal vascular fraction versus adipose tissue-derived microvascular fragments

Background

The seeding of scaffolds with the stromal vascular fraction (SVF) of adipose tissue is a common prevascularization strategy in tissue engineering. Alternatively, adipose tissue-derived microvascular fragments (ad-MVF) may serve as vascularization units. In contrast to SVF single cells, they represent a mixture of intact arteriolar, capillary and venular vessel segments. Therefore, we herein hypothesized that the ad-MVF-based prevascularization of scaffolds is superior to the conventional SVF single cells-based approach.

Results

SVF single cells and ad-MVF were enzymatically isolated from epididymal fat pads of green fluorescent protein (GFP)⁺ donor mice to assess their viability and cellular composition using fluorescence microscopy and flow cytometry. Moreover, collagen-glycosaminoglycan matrices (Integra®) were seeded with identical amounts of the isolates and implanted into full-thickness skin defects within dorsal skinfold chambers of GFP⁻ recipient mice for the intravital fluorescent microscopic, histological and immunohistochemical analysis of implant vascularization and incorporation throughout an observation period of 2 weeks. Non-seeded matrices served as controls. While both isolates contained a comparable fraction of endothelial cells, perivascular cells, adipocytes and stem cells, ad-MVF exhibited a significantly higher viability. After in vivo implantation, the vascularization of ad-MVF-seeded scaffolds was improved when compared to SVF-seeded ones, as indicated by a significantly higher functional microvessel density. This was associated with an enhanced cellular infiltration, collagen content and density of CD31⁺/GFP⁺ microvessels particularly in the center of the implants, demonstrating a better incorporation into the surrounding host tissue. In contrast, non-seeded matrices exhibited a poor vascularization, incorporation and epithelialization over time.

Conclusions

The present study demonstrates that ad-MVF are highly potent vascularization units that markedly accelerate and improve scaffold vascularization when compared to the SVF.

Electronic supplementary material

The online version of this article (10.1186/s13036-018-0118-3) contains supplementary material, which is available to authorized users.

A Randomized Controlled Trial: Regenerative Effects, Efficacy and Safety of Erythropoietin in Burn and Scalding Injuries

In adult’s burn injuries belong to the top 15 causes of injury. Annually more than a million patients receive specialized treatment. Improving burned patients’ outcomes is still a challenge. Effects of erythropoietin (EPO) are reported to be pro-angiogenic, pro-regenerative, anti-inflammatory, immunomodulatory and hypoxia/ischemia protective. Study objectives were to demonstrate cytoprotective and regenerative effects of EPO in burned patients in terms of improved wound healing, reduced morbidity and mortality. This was a prospective, placebo-controlled, randomized, double-blind trial. The trial was conducted in 13 specialized burn care centers in Germany. Adult Patients with 2b° or 3° burn injuries were included. Patients received state of the art burn care including obligatory split skin graft transplantation. Study medication was EPO or placebo every other day for 21 days. Between 12/08 and 06/14, 116 patients were randomized, 84 received study medication (EPO 45, Placebo 39). Primary endpoint analysis revealed inconclusive results, as only a minority of patients reached the primary endpoint [100% re-epithelialization: EPO: 23% (9/40); Placebo 30% (11/37)]. Several secondary endpoints such as SOFA score (morbidity), EPO level in blood and wound healing onset revealed clinical, and statistically significant results in favor of the EPO group. Adverse Events (AEs) and Severe Adverse Events (SAEs) were in expected ranges; AEs EPO: 80%, (36/45), Placebo: 77%, (30/39); SAEs EPO: 24%, (11/45), Placebo: 24%, (8/39). Out of 84 patients two died, one per group, thus mortality was lower than expected. Results (SOFA score) indicate a lower morbidity of the EPO group, suggesting pro-regenerative effects of EPO in burned patients. Higher EPO levels might influence the faster onset of re-epithelialization in the first 10 days of the treatment. Both effects could reveal new therapeutic options.

Clinical Trial Registration: ISRCT Number: ISRCTN95777824 and EudraCT Number: 2006-002886-38, Protocol Number: 0506.

Is prolactin a negative neuroendocrine regulator of human skin re-epithelisation after wounding?

Chronic wounds remain a major unmet healthcare challenge, associated with substantial morbidity and economic costs. Therefore, novel treatment strategies and therapeutic approaches need to be urgently developed. Yet, despite the increasingly recognized importance of neurohormonal signaling in skin physiology, the neuroendocrine regulation of cutaneous wound healing has received surprisingly little attention. Human skin, and its appendages, locally express the pleiotropic neurohormone prolactin (PRL), which not only regulates lactation but also hair follicle cycling, angiogenesis, keratinocyte proliferation, and epithelial stem cell functions. Therefore, we examined the effects of PRL in experimentally wounded female human skin organ culture. Overall, this revealed that PRL slightly, but significantly, inhibited epidermal regeneration (reepithelialisation), cytokeratin 6 protein expression and intraepidermal mitochondrial activity (MTCO1 expression), while it promoted keratinocyte terminal differentiation (i.e. involucrin expression) ex vivo. If the current pilot data are confirmed by further studies, PRL may serve as one of the-rarely studied-negative regulators of cutaneous wound healing that control excessive reepithelialisation. This raises the intriguing and clinically relevant question of whether PRL receptor antagonists could actually promote epidermal repair after human skin wounding.

A Novel Technique for the Standardized Application of Shock Waves in Experimental Research: The Diver Box

The Diver Box is designed to prevent impedance differences, energy loss or damage to neighboring structures caused by the use of shock waves with application gels. The Diver Box is an acrylic glass container filled with tempered water and includes a coupling membrane to prevent the impedance jump from air to water and to avoid the continuous propagation of shock waves into the tissue, maintaining wave dynamics. Different modes of extracorporeal shock waves can be applied to a mouse skin wound without energy loss and protected from harmful phase-reversed waves. Macroscopic changes were seen in only 5% to 12% of tested specimens. Hazardous phase reversal, back reflection and mechanical tissue damage can be avoided by use of the Diver Box, ensuring standardized extracorporeal shock wave application.

Development of tensile strength methodology for murine skin wound healing

In this study, a methodology was evaluated and improved to quickly measure the tensile strength of murine skin in a biomechanical assay for an incisional wound healing model. The aim was to streamline and enhance the wound model, skin specimen preparation, and tensile test so that large numbers of fresh tissue could be tested reliably and rapidly. Linear incisions of 25-mm length were made in the dorsal skin of mice along the spine and metallic staples were used to close the wound. After 20 days, the mice were sacrificed, and a square-shaped section of skin containing the linear incision was excised. Two metallic punches were fabricated and used to punch 15-mm long strips of skin of 2 mm width whose length was orthogonal to the direction of incision. The tensiometer configuration was modified to expedite tensile measurements on fresh skin, and load-to-failure was measured for each strip of skin from the cephalad to the caudal region. We evaluated sources of error in the animal model and the testing protocol and developed procedures to maximize speed and reproducibility in tensile strength measurements. This report provides guidance for efficient and reproducible tensile strength measurement of large numbers of skin specimens from freshly sacrificed animals.

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Tattoo placement to identify the two ends of the healing incisional wound assisted in decreasing error in the position and orientation of tensile strips.

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Custom-made punches to prepare skin strips for tensile testing helped conduct tensile tests of fresh tissue rapidly.

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Alteration of the manual grips of the tensile tester enabled specimens to be gripped rapidly to significantly accelerate testing for each skin strip.

ARA290, a Specific Agonist of Erythropoietin/CD131 Heteroreceptor, Improves Circulating Endothelial Progenitors' Angiogenic Potential and Homing Ability

BACKGROUND

Alternate erythropoietin (EPO)-mediated signaling via the EPOR/CD131 heteromeric receptor exerts the tissue-protective actions of EPO in a wide spectrum of injuries, especially ischemic diseases. Circulating endothelial progenitor cells contribute to endothelial repair and post-natal angiogenesis after chronic ischemic injury. This work aims to investigate the effects of ARA290, a specific agonist of EPOR/CD131 complex, on a subpopulation of endothelial progenitor cells named endothelial colony-forming cells (ECFCs) and to characterize its contribution to ECFCs-induced angiogenesis after peripheral ischemia.

METHODS

ARA290 effects on ECFCs properties were studied using cell cultures in vitro. We injected ARA290 to mice undergoing chronic hindlimb ischemia (CLI) in combination with ECFC transplantation. The homing of transplanted ECFC to ischemic tissue in vivo was assessed by SPECT/CT imaging.

RESULTS

In vitro, ARA290 enhanced the proliferation, migration, and resistance to H2O2-induced apoptosis of ECFCs. After ECFC transplantation to mice with CLI, a single ARA290 injection enhanced the ischemic/non-ischemic ratio of hindlimb blood flow and capillary density after 28 days and the homing of radiolabeled transplanted cells to the ischemic leg 4 h after transplantation. Prior neutralization of platelet-endothelial cell adhesion molecule-1 (CD31) expressed by the transplanted cells inhibited ARA290-induced improvement of homing.

DISCUSSION

ARA290 induces specific improvement of the biological activity of ECFCs. ARA290 administration in combination with ECFCs has a synergistic effect on post-ischemic angiogenesis in vivo. This potentiation appears to rely, at least in part, on a CD31-dependent increase in homing of the transplanted cells to the ischemic tissue.

Activation of the EPOR-β common receptor complex by cibinetide ameliorates impaired wound healing in mice with genetic diabetes

Diabetes is characterized by poor wound healing which currently lacks an efficacious treatment. The innate repair receptor (IRR) is a master regulator of tissue protection and repair which is expressed as a response injury or metabolic stress, including in diabetes. Activation of the IRR might provide benefit for diabetic wound healing. A specific IRR agonist cibinetide was administered in an incisional wound healing model performed mice with genetic diabetes (db⁺/db⁺) and compared to the normal wild-type. Animals were treated daily with cibinetide (30μg/kg/s.c.) or vehicle and euthanized 3, 7, and 14days after the injury to quantitate vascular endothelial growth factor (VEGF), malondialdehyde (MAL), phospho-Akt (pAkt), phospho e-NOS (p-eNOS), and nitrite/nitrate content within the wound. Additional evaluations included quantification of skin histological change, angiogenesis, scar strength, and time to complete wound closure. Throughout the wound healing process diabetic animals treated with vehicle exhibited increased wound MAL with reduced VEGF, pAkt, peNOS and nitrite/nitrate, all associated with poor re-epitheliziation, angiogenesis, and wound breaking strength. Cibenitide administration significantly improved these abnormalities. The results suggest that cibinetide-mediated IRR activation may represent an interesting strategy to treat diabetes-associated wound healing.

Oxytocin effects on experimental skin wound healing

OBJECTIVE

Oxytocin (OXY) has significant effects on mammalian behavior. Next to its role in lactation and social interactions, it is described to support better wound healing as well. However, direct OXY effects on wound healing and the regeneration of the microvascular network are still not clarified. We therefore examined the effects of OXY and an OXY receptor antagonist [atosiban (ATO)] on skin wound healing, focusing on epithelialization and neovascularization.

METHODS

Skin wound healing has been assessed using intravital fluorescence microscopy in a model of full dermal thickness wounds in the dorsal skin fold chamber of hairless mice. Animals received repetitive low or high doses of OXY or ATO. Morphological and cellular characterization of skin tissue repair was performed by histology and in vitro cell assays.

RESULTS

The assessment of skin tissue repair using this therapy regimen showed that OXY and ATO had no major influence on epithelialization, neovascularization, wound cellularity, or inflammation. Moreover, OXY and ATO did neither stimulate nor deteriorate keratinocyte or fibroblast migration and proliferation.

CONCLUSION

In summary, this study is the first to demonstrate that OXY application does not impair skin wound healing or cell behavior. However, until now, the used transmitter system seems not to be clarified in detail, and it might be proposed that it is associated with the stress response of the organism to various stimuli.

The effect of erythropoietin on biomechanical properties of the Achilles tendon during the healing process: an experimental study

Background

The aim of this study was to examine the potential biomechanical and histological benefits of systemic erythropoietin administration during the healing of Achilles tendon injury in a rat experimental model.

Methods

Eighty Sprague-Dawley female rats were included in this study. Animals were randomly assigned into two groups with 40 animals in each: erythropoietin group and control group. Then each group was further divided into four subgroups corresponding to four time points with 10 animals in each. A full-thickness cut was made on the Achilles tendon of each animal and then the tendon was sutured with modified Kessler method. Erythropoietin groups received intraperitoneal erythropoietin (500 IU/kg/day) every day at same time throughout the study period, and the control groups received saline in a similar manner. Animals were sacrificed at four time points, and tensile test was performed on each tendon sample to assess maximum load for each sample. In addition, histopathological examination and scoring was done.

Results

Both groups had improvement on tensile test (maximum load) over time. However, groups did not differ with regard to maximum load in any of the time points. Similarly, groups did not differ with regard to any of the histopathological scores over time.

Conclusions

The findings of this study do not support the benefit of systemic erythropoietin administration in Achilles tendon healing process. Further evidence from larger experimental studies is required to justify any such potential benefit.

Electronic supplementary material

The online version of this article (doi:10.1186/s13018-016-0390-1) contains supplementary material, which is available to authorized users.

Aberrant expression of erythropoietin in uterine leiomyoma: implications in tumor growth

OBJECTIVE

Myomatous erythrocytosis syndrome is a rare complication of uterine leiomyoma caused by erythropoietin (EPO) that is produced by tumor cells. We assessed the EPO expression in leiomyomas and investigated the effects of EPO on the tumor growth.

STUDY DESIGN

Tissue samples were collected from 114 patients with uterine leiomyomas who underwent myomectomy or hysterectomy in Yokohama City University Hospital. From 17 patients, the corresponding normal myometrium was also collected. All samples were analyzed for EPO messenger RNA (mRNA) expression by real-time reverse transcription-polymerase chain reaction. EPO protein expression was determined by an enzyme-linked immunosorbent assay. The relationships between EPO expression and clinicopathological features were retrospectively analyzed using the patients' charts. Blood vessel density and maturity were assessed using hematoxylin-eosin staining and CD34 immunohistochemistry.

RESULTS

EPO mRNA expression was detected in 108 of 114, or 95%, of the leiomyomas. The mean EPO mRNA expression in the leiomyoma was higher than the corresponding normal myometrium (3836 ± 4122 vs 1455 ± 2141; P = .025 by Wilcoxon rank test). The EPO mRNA expression in the leiomyomas varied extensively among samples, ranging from undetectable levels to 18-fold above the mean EPO mRNA of normal myometrium. EPO protein production was observed concomitant with mRNA expression. A positive correlation of leiomyoma size and EPO mRNA expression was shown by Spearman rank correlation coefficient (ρ = 0.294; P = .001), suggesting the involvement of EPO in leiomyoma growth. The blood vessel maturity was also significantly increased in EPO-producing leiomyomas (high vessel maturity in high vs low EPO group: 67% vs 20%; P = .013 by Fisher exact test).

CONCLUSION

This report demonstrates that EPO is produced in most of conventional leiomyomas and supports a model in which EPO accelerates tumor growth, possibly by inducing vessel maturity. Our study suggests one possible mechanism by which some uterine leiomyomas reach a large size, and the understanding of EPO expression patterns in these tumors may be useful for management of the patients with leiomyomas.

Epoetin Alpha and Epoetin Zeta: A Comparative Study on Stimulation of Angiogenesis and Wound Repair in an Experimental Model of Burn Injury

Deep second-degree burns are characterized by delayed formation of granulation tissue and impaired angiogenesis. Erythropoietin (EPO) is able to stimulate angiogenesis and mitosis, activating vascularization and cell cycle. The aim of our study was to investigate whether two biosimilar recombinant human erythropoietins, EPO-α and EPO-Z, may promote these processes in an experimental model of burn injury. A total of 84 mice were used and a scald burn was produced on the back after shaving, in 80°C water for 10 seconds. Mice were then randomized to receive EPO-α (400 units/kg/day/sc) or EPO-Z (400 units/kg/day/sc) or their vehicle (100 μL/day/sc 0.9% NaCl solution). After 12 days, both EPO-α and EPO-Z increased VEGF protein expression. EPO-α caused an increased cyclin D1/CDK6 and cyclin E/CDK2 expression compared with vehicle and EPO-Z (p<0.001). Our study showed that EPO-α and EPO-Z accelerated wound closure and angiogenesis; however EPO-α resulted more effectively in achieving complete skin regeneration. Our data suggest that EPO-α and EPO-Z are not biosimilars for the wound healing effects. The higher efficacy of EPO-α might be likely due to its different conformational structure leading to a more efficient cell proliferation and skin remodelling.

Skin regeneration in deep second-degree scald injuries either by infusion pumping or topical application of recombinant human erythropoietin gel

Large doses of recombinant growth factors formulated in solution form directly injected into the body is usual clinical practice in treating second-degree scald injuries, with promising results, but this approach creates side effects; furthermore, it may not allow appropriate levels of the factor to be sensed by the target injured tissue/organ in the specific time frame, owing to complications arising from regeneration. In this research, two delivery methods (infusion pumping and local topical application) were applied to deliver recombinant human erythropoietin (rHuEPO) for skin regeneration. First, rHuEPO was given in deep second-degree scald injury sites in mice by infusion pump. Vascularization was remarkably higher in the rHuEPO pumping group than in controls. Second, local topical application of rHuEPO gel was given in deep second-degree scald injury sites in rats. Histological analysis showed that epithelialization rate was significantly higher in the rHuEPO gel-treated group than in controls. Immunohistochemical studies showed that the rHuEPO gel-treated group showed remarkably higher expression of skin regeneration makers than the control group. An accurate method for visualization and quantification of blood vessel networks in target areas has still not been developed up to this point, because of technical difficulties in detecting such thin blood vessels. A method which utilizes a series of steps to enhance the image, removes noise from image background, and tracks the vessels edges for vessel segmentation and quantification has been used in this study. Using image analysis methods, we were able to detect the microvascular networks of newly formed blood vessels (less than 500 μm thickness), which participate in the healing process, providing not only nutrition and oxygen to grow tissues but also necessary growth factors to grow tissue cells for complete skin regeneration. The rHuEPO-treated group showed higher expression of stem cell markers (CD 31, CD 90, CD 71, and nestin), which actively contribute to in-wound-healing processes for new hair follicle generation as well as skin regeneration. Collectively, both rHuEPO group pumping into the systemic circulation system, and injection into the local injury area, prompted mice and rats to form new blood vessel networks in scald injury sites, which significantly participate in the scald healing process. These results may lead to the development of novel treatments for scald wounds.

The osteogenic effect of erythropoietin on human mesenchymal stromal cells is dose-dependent and involves non-hematopoietic receptors and multiple intracellular signaling pathways

Erythropoietin (EPO) is a pleiotropic growth factor. Of interest for skeletal tissue engineering, the non-hematopoietic capabilities of EPO include its osteogenic and angiogenic potencies. The main aim of this study was to investigate the dose-response relationship and determine the lowest effective dose of EPO that reliably increases the osteogenic differentiation of human mesenchymal stromal cells (hMSCs). Additional aims were to elucidate the surface receptors and to investigate the role of the intracellular signaling pathways by blocking the mammalian target of rapamycin (mTOR), Jak-2 protein tyrosine kinase (JAK2), and phosphoinositide 3-kinases (PI3K). The primary outcome measures were two mineralization assays, Arsenazo III and alizarin red, applied after 10, 14, and 21 days. Moreover, alkaline phosphatase activity, cell number, and cell viability were determined after 2 and 7 days. A proportional dose-response relationship was observed. In vivo, the lowest effective dose of 20 IU/ml should be used for further research to accommodate safety concerns about adverse effects. Ex vivo, the most effective dose of 100 IU/ml could facilitate vascularization and bone ingrowth in cell-based scaffolds. The expression of non-hematopoietic receptors EPOR and CD131 was documented, and EPO triggered all three examined intracellular pathways. Future studies of the efficacy of EPO in cell-based tissue engineering can benefit from our findings.

Effects of recombinant human erythropoietin on revascularization of full thickness skin grafts in rat

Background:

Autologous skin graft is frequently used in the field of plastic, and reconstructive surgery. The engraftment is dependent upon revascularization and angiogenesis, which can be regulated by different factors. In addition to its hematopoietic effects, erythropoietin is shown to positively affect the wound healing process.

Objectives:

We studied effects of human erythropoietin on revascularization of full thickness skin grafts in rat.

Materials and Methods:

Forty adult Albino male rats were selected for this study. Full thickness skin graft was performed for them, and the effects of systemic, and localized administration of erythropoietin on vascularization of the graft area were evaluated in four groups as following: inverse group underwent full thickness skin graft; in normal saline group normal saline was injected under the fascia of grafted area for seven days; systemic EPO group received systemic erythropoietin for seven days after the surgery; and in graft EPO group, erythropoietin was injected under the fascia of grafted area after full thickness skin grafting for seven days.

Results:

Forty adult Albino male rats (n = 40), with weights ranging from 356 to 469 g (mean 391.5 ± 29.6 g) were included. The vascular densities of central margins were significantly different between inverse group and graft EPO groups (P value = 0.01), and vascular density of central margins of normal saline group and graft EPO groups were significantly different too (P value = 0.04).

Conclusions:

EPO can stimulate angiogenesis which has an important role in wound healing. So, local administration of EPO seems to be beneficial in engraftment.

Increased progression to kidney fibrosis after erythropoietin is used as a treatment for acute kidney injury

Treatment of renal ischemia-reperfusion (IR) injury with recombinant human erythropoietin (rhEPO) reduces acute kidney injury and improves function. We aimed to investigate whether progression to chronic kidney disease associated with acute injury was also reduced by rhEPO treatment, using in vivo and in vitro models. Rats were subjected to bilateral 40-min renal ischemia, and kidneys were studied at 4, 7, and 28 days postreperfusion for renal function, tubular injury and repair, inflammation, and fibrosis. Acute injury was modulated using rhEPO (1,000 or 5,000 IU/kg, intraperitoneally) at the time of reperfusion. Renal tubular epithelial cells or fibroblasts in culture were subjected to hypoxia or oxidative stress, with or without rhEPO (200 IU/ml), and fibrogenesis was studied. The results of the in vivo model confirmed functional and structural improvement with rhEPO at 4 days post-IR (P < 0.05). At 7 days post-IR, fibrosis and myofibroblast stimulation were increased with IR with and without rhEPO (P < 0.01). However, at 28 days post-IR, renal fibrosis and myofibroblast numbers were significantly greater with IR plus rhEPO (P < 0.01) compared with IR only. Mechanistically, rhEPO stimulated profibrotic transforming growth factor-β, oxidative stress (marker 8-hydroxy-deoxyguanosine), and phosphorylation of the signal transduction protein extracellular signal-regulated kinase. In vitro, rhEPO protected tubular epithelium from apoptosis but stimulated epithelial-to-mesenchymal transition and also protected and activated fibroblasts, particularly with oxidative stress. In summary, although rhEPO was protective of renal function and structure in acute kidney injury, the supraphysiological dose needed for renoprotection contributed to fibrogenesis and stimulated chronic kidney disease in the long term.

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.

Effects of systemic pretreatment with CpG oligodeoxynucleotides on skin wound healing in mice

Unmethylated CpG oligodeoxynucleotides (ODN) bind to the Toll-like receptor 9, thus stimulating the immune system. To study the effects of systemic pretreatment with CpG ODN on dermal regeneration, C57BL6/J Tyr mice were treated with CpG or control ODN 6 days prior to implantation of a dorsal skinfold chamber and skin wounding. Wound epithelialization was analyzed by planimetric microscopy. On day 18, wound tissues were taken for (immuno)histochemical staining. CpG ODN increased epithelialization compared with control ODN treatment. Histological analysis revealed reduced capillary density, reduced wound cellularity, and reduced numbers of infiltrating leukocytes, as well as reduced F4/80-positive macrophages, but increased numbers of RELM-α-positive M2 macrophages after CpG ODN treatment, reflecting a better quality of wound healing on day 18 compared with control ODN treatment. Reverse transcription-polymerase chain reaction analysis of Toll-like receptor 9 showed the receptor expression on both fibroblasts and keratinocytes. Fibroblasts showed an increase of migration upon increasing dosages of CpG and not control ODN, reaching ∼50% of the response of basic fibroblast growth factor-exposed cells. Keratinocytes dose-dependently responded to both CpG and control ODN up to values found in keratinocyte growth factor-exposed cells. In summary, CpG ODN support late tissue-remodeling processes that contribute to resolution of inflammation and solid wounds during skin regeneration.

A multi-center study on the regenerative effects of erythropoietin in burn and scalding injuries: study protocol for a randomized controlled trial

Background

Although it was initially assumed that erythropoietin (EPO) was a hormone that only affected erythropoiesis, it has now been proposed that EPO plays an additional key role in the regulation of acute and chronic tissue damage.

Via the inhibition of inflammatory reactions and of apoptosis, stem cell recruitment, advancement of angiogenesis and growth factor release, EPO enhances healing and thus restitutio ad integrum after trauma. Human skin contains EPO receptors and is able to synthesize EPO. We therefore hypothesize that EPO is able to optimize wound healing in thermally injured patients.

Methods/Design

This is a large, prospective, randomized, double-blind, multi-center study, funded by the German Federal Ministry of Education and Research, and fully approved by the designated ethics committee. The trial, which is to investigate the effects of EPO in severely burned patients, is in its recruitment phase and is being carried out in 13 German burn care centers. A total of 150 patients are to be enrolled to receive study medication every other day for 21 days (EPO 150 IU/kg body weight or placebo). A follow-up of one year is planned. The primary endpoint of this study is the time until complete re-epithelialization of a defined skin graft donor site is reached. Furthermore, clinical parameters such as wound healing, scar formation (using the Vancouver scar scale), laboratory values, quality of life (SF-36), angiogenic effects, and gene- and protein-expression patterns are to be determined. The results will be carefully evaluated for gender differences.

Discussion

We are seeking new insights into the mechanisms of wound healing in thermally injured patients and more detailed information about the role EPO plays, specifically in these complex interactions. We additionally expect that the biomimetic effects of EPO will be useful in the treatment of acute thermal dermal injuries.

Trial registration

EudraCT Number: 2006-002886-38, Protocol Number: 0506, ISRCT Number: http://controlled-trials.com/ISRCTN95777824/ISRCTN95777824.

The mouse dorsal skin fold chamber as a means for the analysis of tissue engineered skin

The therapy of extensive and deep burn wounds is still a challenging task for reconstructive plastic surgery. The outcome is generally not satisfactory, neither from the functional nor from the aesthetic aspect. Several available skin substitutes are used but there is need for optimization of new skin substitutes which have to be tested in vitro as well as in vivo. Here, we show that the dorsal skin fold chamber preparation of mice is well suited for the testing of skin substitutes in vivo. Dermal skin constructs consisting of matriderm(®) covered with a collagen type I gel were inserted into full thickness skin wounds in the skin fold chambers. The skin substitutes integrated well into the adjacent skin and got epithelialized from the wound edges within 11 days. The epithelialization by keratinocytes is the prerequisite that also cell-free dermal substitutes might be used in the case of the lack of sufficient areas to gain split thickness skin grafts. Further advantage of the chambers is the lack of wound contraction, which is common but undesired in rodent wound healing. Furthermore, this model allows a sophisticated histological as well as immunohistochemical analysis. As such, we conclude that this model is well suited for the analysis of tissue engineered skin constructs. Besides epithelialization the mode and extend of neovascularization and contraction of artificial grafts may be studied under standardized conditions.

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.

Skin regeneration with conical and hair follicle structure of deep second-degree scalding injuries via combined expression of the EPO receptor and beta common receptor by local subcutaneous injection of nanosized rhEPO

Background

Acceleration of skin regeneration is still an unsolved problem in the clinical treatment of patients suffering from deep burns and scalds. Although erythropoietin (EPO) has a protective role in a wide range of organs and cells during ischemia and after trauma, it has been recently discovered that EPO is not tissue-protective in the common β subunit receptor (βCR) knockout mouse. The protective capacity of EPO in tissue is mediated via a heteroreceptor complex comprising both the erythropoietin receptor (EPOR) and βCR. However, proof of coexpression of these heterogenic receptors in regenerating skin after burns is still lacking.

Methods

To understand the role of nanosized recombinant human erythropoietin (rhEPO) in wound healing, we investigated the effects of subcutaneous injections of EPO on skin regeneration after deep second-degree scalding injuries. Our aim was to determine if joint expression of EPOR and βCR is a prerequisite for the tissue-protective effect of rhEPO. The efficiency in wound regeneration in a skin scalding injury mouse model was examined. A deep second-degree dermal scald injury was produced on the backs of 20 female Balb/c mice which were subsequently randomized to four experimental groups, two of which received daily subcutaneous injections of rhEPO. At days 7 and 14, the mice were sacrificed and the effects of rhEPO were analyzed with respect to grade of re-epithelialization (wound closure) and stage of epidermal maturation. This was investigated using different histological parameters of epithelial covering, such as depth of the epidermal layer, epidermal stratification, and presence of conical and hair follicle structures.

Results

Expression of EPOR, βCR, and growth hormone receptor at the mRNA and protein levels was demonstrated with reverse transcriptase polymerase chain reaction and Western blot analysis. After rhEPO treatment, the rate of re-epithelialization of the scalding injury was increased and the time to final wound closure was reduced. In addition, the quality of regenerated skin was improved. In this investigation, for the first time, we demonstrated coexpression of EPOR and βCR at the RNA and protein levels in vivo using a deep second-degree scalding injury mouse model. These results highlight the potential role of rhEPO in the improved treatment of burns patients, which might be crucial for the development of innovative new therapy regimes.

Conclusion

Local injection of nanosized rhEPO directly to the injury site rather than systemic administration for deep second-degree scalding injuries achieved complete skin regeneration with conical and hair follicle structure via combined expression of EPOR and βCR.