Interactive Role of Trauma Cytokines and Erythropoietin and Their Therapeutic Potential for Acute and Chronic Wounds

Effects of direct pulp capping with recombinant human erythropoietin and/or mineral trioxide aggregate on inflamed rat dental pulp

OBJECTIVE

This study aimed to evaluate the dental pulp responses to recombinant human erythropoietin (rhEPO) and/or mineral trioxide aggregate (MTA) in pulp capping of inflamed dental pulp in vivo.

MATERIALS AND METHODS

In accordance with ARRIVE guidelines, pulp inflammation was induced by exposing the maxillary first molars (n = 64) of Wistar rats (n = 32) to the oral environment for two days. The exposed pulps were randomly assigned four groups based on the pulp capping material: rhEPO, MTA, MTA + rhEPO, or an inert membrane. An additional eight rats formed the healthy control group. After four weeks, the animals were euthanized, and histological, qRT-PCR, and spectrophotometric techniques were employed to analyze the left maxillary segments, right first maxillary molars, and blood samples, respectively. Statistical significance was set at p < 0.05 and < 0.001.

RESULTS

Pulp capping with rhEPO, MTA, or MTA + rhEPO resulted in lower inflammation and higher mineralization scores compared to untreated control. MTA + rhEPO group exhibited significantly decreased expression of tumor necrosis factor-alpha, and interleukin 1-beta, while MTA group showed substantially reduced expression of interferon-gamma. Both rhEPO and MTA + rhEPO groups presented elevated dentin matrix protein 1 levels compared to untreated control. Furthermore, pulp capping with rhEPO and/or MTA led to increased transforming growth factor-beta 1 expression and reductions of pro-inflammatory/immunoregulatory cytokine ratios and prooxidative markers. Pulp capping with rhEPO also resulted in increase of systemic antioxidative stress markers.

CONCLUSION

Capping with rhEPO or MTA + rhEPO resulted in a favorable effect that was similar or even superior to that of MTA.

Vascular Endothelial Growth Factor, Epidermal Growth Factor, and Epithelialization Analysis on Full-Thickness Wound Applied with Topical Erythropoietin

BACKGROUND: Skin wounds are a major challenge, such as full-thickness wounds that need a long time to heal. However, the addition of erythropoietin can accelerate the wound healing process. AIM: This study was aimed to determine the effect of topical erythropoietin administration on vascular endothelial growth factor (VEGF), epidermal growth factor (EGF), and epithelialization in the wound healing process. METHODS: This was randomized controlled trial. Full-thickness wounds were created on the back of each white rat. No treatment was administered in the control group (n=16), and topical erythropoietin was applied in the treatment group (n=16). The rats were euthanized on day 3 and day 6 post-surgery, respectively. The expression levels of VEGF, EGF, and microscopic epithelialization rate were examined. RESULTS: The level of EGF expression in the treatment group increased significantly on day 3 by 2.84 times compared to the control group and on day 6 increased to 4.89 times compared to the control group (p < 0.001). The level of VEGF expression in the treatment group on day 3 increased 2.18 times compared to the control group and on day 6 increased to 2.65 times compared to the control group (p < 0.001). Meanwhile, epithelialization in the treatment group on day 3 increased 1.3 times compared to the control group and on day 6 increased up to 7.62 times compared to the control group (p < 0.001). CONLUSION: Topical administration of erythropoietin could increase the expression of VEGF, EGF, and epithelialization in both early inflammatory and proliferative phases.

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

The effects of topical erythropoietin on non-surgical treatment of periodontitis: a preliminary study

Background

The purpose of periodontal treatments is to reduce inflammation, restore gingival health and clinical attachment level gain by controlling microbial plaque formation and other etiological factors. One of the drugs that has been tested in many areas and shown good anti-inflammatory properties is erythropoietin (EPO). We evaluated the effect of this drug on the improvement of periodontitis after the phase I treatment.

Methods

This study was conducted on 30 patients with stage III periodontitis who had at least two bilateral teeth with CAL of ≥ 5 mm and PPD ≥ 6 mm at ≥ 2 non‐adjacent teeth and bleeding on probing. After oral hygiene instruction and scaling and root planning (SRP), EPO gel containing a solution of 4000 units was applied deeply in the test group and placebo gel was deeply administered in the control pockets (5 times, every other day). The clinical parameters of the plaque index (PI), gingival index (GI), clinical attachment level (CAL), probing depth (PD) and bleeding index (BI) were measured at baseline and after three months of follow up. The P-value was set at 0.05.

Results

All clinical variables improved after treatment in both groups. The BI and GI scores (which reflects the degree of gingival inflammation) showed statistically more reduction in test group. The CAL decreased from 5.1 ± 4.1 to 3.40 ± 2.71 mm; and 5.67 ± 4.32 to 4.33 ± 3.19 mm in test and control group, respectively (P < 0.00). After the treatment, there was a significant greater reduction in CAL and also PD values in test group (P < 0.01).

Conclusion

Local application of EPO gel in adjunct to SRP can improve clinical inflammation and CAL gain in periodontitis.

Trial registration: This study was registered at 2017-11-06 in IRCT. All procedures performed in this study were approved with ID number of IR.TUMS.DENTISTRY.REC.1396.3139 in Tehran University of medical science.

Supplementary Information

The online version contains supplementary material available at 10.1186/s12903-021-01607-y.

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.

Topical Erythropoietin Accelerates Wound Closure in Patients with Diabetic Foot Ulcers: A Prospective, Multicenter, Single-Blind, Randomized, Controlled Trial

The diabetic foot ulcer (DFU) is a major disabling complication of diabetes mellitus. Growing evidence suggests that topical erythropoietin (EPO) can promote wound healing. The aim of this study is to clinically assess the efficacy of a proprietary topical EPO-containing hydrogel for treating DFUs. We conducted a randomized, controlled trial in 20 patients with DFUs. After a 14-day screening period, the DFUs of 20 eligible participants who fulfilled the inclusion criteria were randomly assigned (1:1) to either a 12-week of daily treatment with topical EPO and standard-of-care (SOC) or SOC treatment alone. The DFUs were assessed weekly until week 12. The primary outcome was 75% ulcer closure or higher. After 12 weeks of treatment, 75% ulcer closure was achieved in 6 of the 10 patients whose DFUs were treated with topical EPO and in one of the 8 patients whose DFUs were treated with SOC alone. The mean area of the DFUs that were treated with topical EPO and SOC was significantly smaller than those treated with SOC alone (1.2 ± 1.4 cm² vs. 4.2 ± 3.4 cm²; p = 0.023). Re-epithelialization was faster in the topically EPO-treated DFUs than in the SOC-treated DFUs. There were no treatment-related adverse events. We conclude that topical EPO is a promising treatment for promoting the healing of DFUs. Clinical Trial Registration number: NCT02361931.

Interim Results of the Remede d'Or Study: A Multicenter, Single-Blind, Randomized, Controlled Trial to Assess the Safety and Efficacy of an Innovative Topical Formulation of Erythropoietin for Treating Diabetic Foot Ulcers

Objective: To inform on the interim results of the Remede d'Or study, which is a prospective, multicenter, single-blind, randomized, controlled clinical study on the safety and efficacy of RMD-G1, a topical carbopol-based hydrogel with a fibronectin matrix whose active pharmaceutical ingredient is erythropoietin (EPO), for treating diabetic foot ulcers (DFU). Approach: The trial will comprise 20 patients with type 2 diabetes mellitus with neuroischemic DFUs who will be randomized into two groups: (1) a control group in which standard-of-care (SOC) will be used to treat the DFUs, and (2) a test group in which SOC and RMD-G1 will be used to treat the DFUs. On day 0, all participants will be randomized to receive either RMD-G1 and SOC treatment or SOC alone. The primary endpoint of the study is complete closure of the DFU within the 12-week study period following daily treatments and dressing changes. Results: Interim results reveal that those DFUs which were treated with RMD-G1 responded positively: there was a significant reduction in the wound areas. In contrast, the condition of those DFUs which were treated with only SOC deteriorated. Innovation: To date, no topical therapies with proven efficacy for treating DFUs exist. Topical application of EPO-based RMD-G1 in conjunction with SOC to a DFU accelerates their healing and closure. Conclusions: The interim results of this trial indicate that topical RMD-G1 is a safe adjunctive therapy to SOC, which accelerates the closure of a DFU. RMD-G1 is safe pharmaceutical because EPO has a proven safety profile.

Qualitative and Quantitative Analysis of Cardiac Progenitor Cells in Cases of Myocarditis and Cardiomyopathy

We aimed to identify and quantify CD117⁺ and CD90⁺ endogenous cardiac progenitor cells (CPC) in human healthy and diseased hearts. We hypothesize that these cells perform a locally acting, contributing function in overcoming medical conditions of the heart by endogenous means. Human myocardium biopsies were obtained from 23 patients with the following diagnoses: Dilatative cardiomyopathy (DCM), ischemic cardiomyopathy (ICM), myocarditis, and controls from healthy cardiac patients. High-resolution scanning microscopy of the whole slide enabled a computer-based immunohistochemical quantification of CD117 and CD90. Those signals were evaluated by Definiens Tissue Phenomics® Technology. Co-localization of CD117 and CD90 was determined by analyzing comparable serial sections. CD117⁺/CD90⁺ cardiac cells were detected in all biopsies. The highest expression of CD90 was revealed in the myocarditis group. CD117 was significantly higher in all patient groups, compared to healthy specimens (^*p < 0.05). The highest co-expression was found in the myocarditis group (6.75 ± 3.25 CD90⁺CD117⁺ cells/mm²) followed by ICM (4 ± 1.89 cells/mm²), DCM (1.67 ± 0.58 cells/mm²), and healthy specimens (1 ± 0.43 cells/mm²). We conclude that the human heart comprises a fraction of local CD117⁺ and CD90⁺ cells. We hypothesize that these cells are part of local endogenous progenitor cells due to the co-expression of CD90 and CD117. With novel digital image analysis technologies, a quantification of the CD117 and CD90 signals is available. Our experiments reveal an increase of CD117 and CD90 in patients with myocarditis.

Alternative Erythropoietin Receptors in the Nervous System

In addition to its regulatory function in the formation of red blood cells (erythropoiesis) in vertebrates, Erythropoietin (Epo) contributes to beneficial functions in a variety of non-hematopoietic tissues including the nervous system. Epo protects cells from apoptosis, reduces inflammatory responses and supports re-establishment of compromised functions by stimulating proliferation, migration and differentiation to compensate for lost or injured cells. Similar neuroprotective and regenerative functions of Epo have been described in the nervous systems of both vertebrates and invertebrates, indicating that tissue-protective Epo-like signaling has evolved prior to its erythropoietic function in the vertebrate lineage. Epo mediates its erythropoietic function through a homodimeric Epo receptor (EpoR) that is also widely expressed in the nervous system. However, identification of neuroprotective but non-erythropoietic Epo splice variants and Epo derivatives indicated the existence of other types of Epo receptors. In this review, we summarize evidence for potential Epo receptors that might mediate Epo's tissue-protective function in non-hematopoietic tissue, with focus on the nervous system. In particular, besides EpoR, we discuss three other potential neuroprotective Epo receptors: (1) a heteroreceptor consisting of EpoR and common beta receptor (βcR), (2) the Ephrin (Eph) B4 receptor and (3) the human orphan cytokine receptor-like factor 3 (CRLF3).

Trauma and Stem Cells: Biology and Potential Therapeutic Implications

Trauma may cause irreversible tissue damage and loss of function despite current best practice. Healing is dependent both on the nature of the injury and the intrinsic biological capacity of those tissues for healing. Preclinical research has highlighted stem cell therapy as a potential avenue for improving outcomes for injuries with poor healing capacity. Additionally, trauma activates the immune system and alters stem cell behaviour. This paper reviews the current literature on stem cells and its relevance to trauma care. Emphasis is placed on understanding how stem cells respond to trauma and pertinent mechanisms that can be utilised to promote tissue healing. Research involving notable difficulties in trauma care such as fracture non-union, cartilage damage and trauma induced inflammation is discussed further.

Current concepts on burn wound conversion-A review of recent advances in understanding the secondary progressions of burns

Burn wound conversion describes the process by which superficial partial thickness burns convert into deeper burns necessitating surgical intervention. Fully understanding and thus controlling this phenomenon continues to defy burn surgeons. However, potentially guiding burn wound progression so as to obviate the need for surgery while still bringing about healing with limited scarring is the major unmet challenge. Comprehending the pathophysiologic background contributing to deeper progression of these burns is an essential prerequisite to planning any intervention. In this study, a review of articles examining burn wound progression over the last five years was conducted to analyze trends in recent burn progression research, determine changes in understanding of the pathogenesis of burn conversion, and subsequently examine the direction for future research in developing therapies. The majority of recent research focuses on applying therapies from other disease processes to common underlying pathogenic mechanisms in burn conversion. While ischemia, inflammation, and free oxygen radicals continue to demonstrate a critical role in secondary necrosis, novel mechanisms such as autophagy have also been shown to contribute affect significantly burn progression significantly. Further research will have to determine whether multiple mechanisms should be targeted when developing clinical therapies.

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.

Preclinical and clinical evidence for stem cell therapies as treatment for diabetic wounds

Diabetic wounds remain a global unsolved problem and the cost of diabetes-related amputations and diabetic wound treatment is approximately US$3 billion and US$9 billion per year, respectively. Diabetic foot ulcers (DFUs) occur in 15% of all patients with diabetes and precede 84% of all diabetes-related lower leg amputations. Currently, there is no satisfying treatment for these hard-to-heal-wounds. However, as we discuss here, experimental preclinical evidence for the successful use of adult stem cell therapies for diabetic wounds gives new hope for the development of effective treatments for use in the clinic.

The role of microRNAs in skin fibrosis

Fibrotic skin disorders may be debilitating and impair quality of life. There are few effective treatment options for cutaneous fibrotic diseases. In this review, we discuss our current understanding of the role of microRNAs (miRNAs) in skin fibrosis. miRNAs are a class of small, non-coding RNAs involved in skin fibrosis. These small RNAs range from 18 to 25 nucleotides in length and modify gene expression by binding to target messenger RNA (mRNA), causing degradation of the target mRNA or inhibiting the translation into proteins. We present an overview of the biogenesis, maturation and function of miRNAs. We highlight miRNA’s role in key skin fibrotic processes including: transforming growth factor-beta signaling, extracellular matrix deposition, and fibroblast proliferation and differentiation. Some miRNAs are profibrotic and their upregulation favors these processes contributing to fibrosis, while anti-fibrotic miRNAs inhibit these processes and may be reduced in fibrosis. Finally, we describe the diagnostic and therapeutic significance of miRNAs in the management of skin fibrosis. The discovery that miRNAs are detectable in serum, plasma, and other bodily fluids, and are relatively stable, suggests that miRNAs may serve as valuable biomarkers to monitor disease progression and response to treatment. In the treatment of skin fibrosis, antifibrotic miRNAs may be upregulated using mimics and viral vectors. Conversely, profibrotic miRNAs may be downregulated by employing anti-miRNAs, sponges, erasers and masks. We believe that miRNA-based therapies hold promise as important treatments and may transform the management of fibrotic skin diseases by physicians.

Utility of a human-mouse xenograft model and in vivo near-infrared fluorescent imaging for studying wound healing

To study the complex cellular interactions involved in wound healing, it is essential to have an animal model that adequately mimics the human wound microenvironment. Currently available murine models are limited because wound contraction introduces bias into wound surface area measurements. The purpose of this study was to demonstrate utility of a human-mouse xenograft model for studying human wound healing. Normal human skin was harvested from elective abdominoplasty surgery, xenografted onto athymic nude (nu/nu) mice, and allowed to engraft for 3 months. The graft was then wounded using a 2-mm punch biopsy. Wounds were harvested on sequential days to allow tissue-based markers of wound healing to be followed sequentially. On the day of wound harvest, mice were injected with XenoLight RediJect cyclooxygenase-2 (COX-2) probe and imaged according to package instructions. Immunohistochemistry confirms that this human-mouse xenograft model is effective for studying human wound healing in vivo. Additionally, in vivo fluorescent imaging for inducible COX-2 demonstrated upregulation from baseline to day 4 (P = 0·03) with return to baseline levels by day 10, paralleling the reepithelialisation of the wound. This human-mouse xenograft model, combined with in vivo fluorescent imaging provides a useful mechanism for studying molecular pathways of human wound healing.

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.

Stem-cell-based, tissue engineered tracheal replacement in a child: a 2-year follow-up study

BACKGROUND

Stem-cell-based, tissue engineered transplants might offer new therapeutic options for patients, including children, with failing organs. The reported replacement of an adult airway using stem cells on a biological scaffold with good results at 6 months supports this view. We describe the case of a child who received a stem-cell-based tracheal replacement and report findings after 2 years of follow-up.

METHODS

A 12-year-old boy was born with long-segment congenital tracheal stenosis and pulmonary sling. His airway had been maintained by metal stents, but, after failure, a cadaveric donor tracheal scaffold was decellularised. After a short course of granulocyte colony stimulating factor, bone marrow mesenchymal stem cells were retrieved preoperatively and seeded onto the scaffold, with patches of autologous epithelium. Topical human recombinant erythropoietin was applied to encourage angiogenesis, and transforming growth factor β to support chondrogenesis. Intravenous human recombinant erythropoietin was continued postoperatively. Outcomes were survival, morbidity, endoscopic appearance, cytology and proteomics of brushings, and peripheral blood counts.

FINDINGS

The graft revascularised within 1 week after surgery. A strong neutrophil response was noted locally for the first 8 weeks after surgery, which generated luminal DNA neutrophil extracellular traps. Cytological evidence of restoration of the epithelium was not evident until 1 year. The graft did not have biomechanical strength focally until 18 months, but the patient has not needed any medical intervention since then. 18 months after surgery, he had a normal chest CT scan and ventilation-perfusion scan and had grown 11 cm in height since the operation. At 2 years follow-up, he had a functional airway and had returned to school.

INTERPRETATION

Follow-up of the first paediatric, stem-cell-based, tissue-engineered transplant shows potential for this technology but also highlights the need for further research.

FUNDING

Great Ormond Street Hospital NHS Trust, The Royal Free Hampstead NHS Trust, University College Hospital NHS Foundation Trust, and Region of Tuscany.

New strategies in clinical care of skin wound healing

The prevalence of chronic wounds is closely correlated to the aging population and so-called civilizational diseases. Therefore, they are causing morbidity and mortality of millions of patients worldwide, with an unbroken upward trend. As a consequence, chronic wounds induce enormous and rapidly growing costs for our health care systems and society in general. Thus, medically effective and cost-efficient treatment methods are urgently needed. Methods of 'regenerative medicine' might offer innovative scientific solutions, including the use of stem cells, growth factors and new bioactive materials. These tools are experimentally well described but clinically poorly performed. The main reasons for this are both legislative and economic. This review describes state-of-the-art techniques, up-to-date research projects, innovative preclinical and clinical approaches in wound care, and activities to translate these innovative techniques into clinical routine.

The concept of in vivo airway tissue engineering

We investigated whether decellularized pig tracheas could regenerate in vivo, without being recellularized before transplantation, using the own body as bioreactor. Decellularized pig tracheal scaffolds were intraoperative conditioned with mononuclear cells and growth and differentiation factors. During the postoperative period, the in situ regeneration was boosted by administering bioactive molecules to promote peripheral mobilization and differentiation of stem/progenitor cells and ultimately the regenerative process. Results revealed, after 2 weeks, a nearly normal trachea, with respiratory epithelium and a double-banded cartilage but without any mechanical differences compared to the native tissue. The growth factor administration resulted in a mobilization of progenitor and stem cells into the peripheral circulation and in an up-regulation of anti-apoptotic genes. Isolated stem/progenitor cells could be differentiated in vitro into several cell types, proving their multipotency. We provide evidence that the own body can be used as bioreactor to promote in vivo tissue engineering replacement. Moreover, we demonstrated the beneficial effect of additional pharmaceutical intervention for an improved engraftment of the transplant.

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.