The role of growth factors in wound healing

Platelet growth factors from allogeneic platelet-rich plasma for clinical improvement in split-thickness skin graft

Background and objectives:

Platelets are a source of numerous growth factors which facilitate repair and healing. Thus platelet rich plasma has been increasingly used as a treatment modality in the field of reconstructive surgeries for wound healing. This preliminary study was carried out to explore whether platelet growth factors from platelet rich plasma could be used for enhancement of split thickness skin graft survival.

Materials and Methods:

Twenty patients (13 males and 7 females) requiring split thickness skin graft for various clinical reasons were enrolled in the study. Platelet rich plasma was collected by apheresis and frozen at −80° C. It was thawed at room temperature immediately before its intended application. PRP was applied only on one half of the wound, while another half served as control. Patient was followed for 6 weeks. The effect was assessed at first dressing in terms of graft uptake and subsequently as time taken for complete healing.

Results:

There was 100% uptake of the graft in the area where platelet rich plasma was applied. In the control area, there was complete graft loss in 4 cases, partial loss in 7 cases and complete uptake in 9 cases.

Conclusion:

This study demonstrated promising results on application of PRP to split thickness skin grafts. Further randomized studies with greater sample size may be undertaken to establish platelet rich plasma as a validated treatment modality.

Efficacy Study of Broken Rice Maltodextrin in In Vitro Wound Healing Assay

Maltodextrins that contain both simple sugars and polymers of saccharides have been widely used as ingredients in food products and pharmaceutical delivery systems. To date, no much work has been reported on the applications of maltodextrin from broken rice (RB) sources. Therefore, the objective of this work was to investigate the in vitro wound healing efficacy of RB maltodextrin at different conditions. Wounds treated with lower dextrose equivalent (DE) range (DE 10–14) of maltodextrins at a concentration of 10% obtained from RB were found to be able to heal the wounds significantly faster (p < 0.01) than maltodextrin with higher DE ranges (DE 15–19 and DE 20–24) and concentrations of 5% and 20%. The findings from both BrdU and MTT assay further confirmed its wound healing properties as the NIH 3T3 fibroblast wounded cells were able to proliferate without causing cytotoxic effect when wounded cell was treated with maltodextrin. All these findings indicated that the RB maltodextrin could perform better than the commercial maltodextrin at the same DE range. This study showed that RB maltodextrins had better functionality properties than other maltodextrin sources and played a beneficial role in wound healing application.

Effects of kynurenine on CD3+ and macrophages in wound healing

As prolongation of the inflammation phase in a healing process frequently leads to wound impairment, here we queried whether kynurenine (Kyn) could modulate this phase of wound healing. To address this, a protein microarray, quantitative polymerase chain reaction (qPCR), flow cytometry for immune cells and immune cell proliferation in the presence and absence of Kyn were conducted and compared. The result of a protein microarray revealed that the expression of 12 pro-inflammatory cytokines and chemokines was modulated in Kyn-treated mouse splenocytes as compared with those of control. These findings were then evaluated by conducting a qPCR for the gene expression of these factors and showed a significant reduction in the gene expression of majority of these cytokines and chemokines (interleukin [IL]-2, IL-17, C-X-C motif chemokine ligand [CXCL] 10, CXCL1, C-C motif ligand [CCL] 12, CXCL9, CCL4, CXCL2, and CCL5) in response to Kyn treatment. To test the anti-inflammatory effect of Kyn in an animal model, dorsal surface wounds were generated in a mouse model and wounds received daily topical application of either nothing (control), dermal cream (second control), or Kyn cream using uninjured skin tissue as another control. The wounded tissues were harvested on days 3, 6, and 10 postwounding. As anticipated, the results of fluorescence-activated cell sorting analysis revealed that upon wounding, the number of total infiltrated CD3+ cells and macrophages (CD11b+) significantly increased on day 3, peaked on day 6, and reduced on day 10 post-wounding. Interestingly, as compared with those of uninjured and dermal cream alone-treated wounds, Kyn treatment significantly reduced the number of infiltrated CD3+ cells, but not CD11b+ cells, at different time intervals examined. These findings collectively suggest that Kyn, as a small molecule, can potentially be used to overcome the difficulties associated with persistency of inflammation in healing wounds.

Determining the Effect of Preparation and Storage: An Effort to Streamline Platelet Components as a Source of Growth Factors for Clinical Application

BACKGROUND

In the present study, different methods for preparation of platelet-rich plasma (PRP) are investigated in order to standardize the component in terms of growth factor content. The effects of concentration technique and storage duration are also analyzed.

METHODS

PRP was collected from 40 donors by plateletpheresis as well as by the buffy coat and tube method. Concentration of growth factors was performed using double freeze thaw- and CaCl2-induced degranulation techniques. Growth factor estimation was performed using ELISA.

RESULTS

The levels of growth factors were highest in PRP from buffy coat, moderately lower in plasma gained by plateletpheresis and lowest in that obtained by the tube method. Mean levels of platelet-derived growth factors (PDGF) AB and BB are significantly higher when CaCl2 was used for concentrating the growth factors. The mean levels of transforming growth factor β1 and insulin-like growth factor I were higher when applying the double freeze thaw technique. There was a substantial decline in the levels of growth factors during storage.

CONCLUSION

The buffy coat method is suitable as preparation method for PRP in most settings. The double freeze thaw technique is better suited as concentration technique as it causes lysis of both platelets and white blood cells for releasing growth factors and is easier to perform. Growth factors are not stable in plasma, thus PRP should be frozen immediately after preparation.

Momordica charantia ointment accelerates diabetic wound healing and enhances transforming growth factor-β expression

OBJECTIVE

Transforming growth factor-β (TGF-β) plays an important role in wound healing. Delayed wound healing is a consequence of diabetes, leading to high morbidity and poor quality of life. Momordica charantia (MC) fruit possesses anti-diabetic and wound healing properties. This study aimed to explore the changes in TGF-β expression in diabetic wounds treated with topical MC fruit extract.

METHODS

Fifty-six male Sprague-Dawley rats were divided into a normal control group and five diabetic groups of ten rats each. Intravenous streptozotocin (50mg/kg) was given to induce diabetes in the diabetic groups. Full thickness excision wounds were created on the thoracodorsal region of the animals, and these wounds were then treated with vehicle, MC powder, MC ointment and povidone ointment or ointment base for ten days. Wound healing was determined by the rate of wound closure, total protein content and TGF-β expression in the wounds, and histological observation.

RESULTS

Diabetic groups showed delayed wound closure rates compared to the control group. The wound closure rate in the MC ointment group was significantly faster than that of the untreated diabetic group (p<0.05). The MC ointment group also showed intense TGF-β expression and a high level of total protein content.

CONCLUSION

MC ointment has a promising potential for use as an alternative topical medication for diabetic wounds. This work has shown that it accelerates wound healing in diabetic rats, and it is suggested here that this occurs by enhancing TGF-β expression. Further work is recommended to explore this effect.

The basic science of platelet-rich plasma (PRP): what clinicians need to know

Platelet-rich plasma (PRP) has been advocated for the biological augmentation of tissue healing and regeneration through the local introduction of increased levels (above baseline) of platelets and their associated bioactive molecules. In theory, the increased levels of autologous growth factors and secretory proteins provided by the concentrated platelets may enhance the wound healing process, especially in degenerative tissues or biologically compromised individuals. Although PRP has been increasingly utilized in the treatment of a variety of sports-related injuries, improvements in healing and clinical outcomes have not been universally reported. One reason for this may be the fact that all PRP preparations are not the same. Variations in the volume of whole blood taken, the platelet recovery efficacy, the final volume of plasma in which the platelets are suspended, and the presence or absence of white blood cells, and the addition of exogenous thrombin to activate the platelets or calcium chloride to induce fibrin formation, can all affect the character and potential efficacy of the final PRP product. This article will review the basic principles involved in creating PRP and examine the potential basic scientific significance of the individual blood components contained in the various forms of PRP currently used in sports medicine.

Production of functional active human growth factors in insects used as living biofactories

Growth factors (GFs) are naturally signalling proteins, which bind to specific receptors on the cell surface. Numerous families of GFs have already been identified and remarkable progresses have been made in understanding the pathways that these proteins use to activate/regulate the complex signalling network involved in cell proliferation or wound healing processes. The bottleneck for a wider clinical and commercial application of these factors relay on their scalable cost-efficient production as bioactive molecules. The present work describes the capacity of Trichoplusia ni insect larvae used as living bioreactors in combination with the baculovirus vector expression system to produce three fully functional human GFs, the human epidermal growth factor (huEGF), the human fibroblast growth factor 2 (huFGF2) and the human keratinocyte growth factor 1 (huKGF1). The expression levels obtained per g of insect biomass were of 9.1, 2.6 and 3mg for huEGF, huFGF2 and huKGF1, respectively. Attempts to increase the productivity of the insect/baculovirus system we have used different modifications to optimize their production. Additionally, recombinant proteins were expressed fused to different tags to facilitate their purification. Interestingly, the expression of huKGF1 was significantly improved when expressed fused to the fragment crystallizable region (Fc) of the human antibody IgG. The insect-derived recombinant GFs were finally characterized in terms of biological activity in keratinocytes and fibroblasts. The present work opens the possibility of a cost-efficient and scalable production of these highly valuable molecules in a system that favours its wide use in therapeutic or cosmetic applications.

The Effect of Bone-Marrow-Derived Stem Cells and Adipose-Derived Stem Cells on Wound Contraction and Epithelization

Objective: The relationship between the wound contraction and levels of α-smooth muscle actin (α-SMA) has been revealed in different studies. We aimed to investigate the effects of mesenchymal stem cells (MSCs), mainly bone-marrow-derived stem cells (BSCs) and adipose-derived stem cells (ASCs), and find out the α-SMA, fibroblast growth factor (FGF), transforming growth factor beta, and vascular endothelial growth factor (VEGF) levels on an in vivo acute wound healing model after the application of MSCs. Approach: Four circular skin defects were formed on the dorsum of Fisher rats (n=20). The defects were applied phosphate-buffered saline (PBS), ASCs, BSCs, and patchy skin graft, respectively. The healing time and scar area were noted. Results: There was a statistical decrease in the healing time in ASC, BSC, and skin graft groups (p<0.05). However, the scar was smaller in the PBS group (p<0.05). The α-SMA levels were statistically lower in ASC, BSC, and graft groups (p<0.05). The FGF levels were statistically higher in ASC and BSC groups (p<0.05). The differentiation of the injected MSCs to endothelial cells and keratinocytes was observed. Innovation and Conclusion: MSCs decrease the healing time and contraction of the wound while increasing the epithelization rate by increasing angiogenesis.

The role of growth factor Sadat-Habdan mesenchymal stimulating peptide in healing of burn wounds

BACKGROUND

Burns occur in everyday life and cause morbidity and mortality due to delayed healing. Many agents were tried to accelerate healing of burns. The aim of this study was to assess for the first time Sadat-Habdan mesenchymal stimulating peptide (SHMSP) known angiogenesis factor in healing of experimentally created burns in rats.

METHODS

Forty male rats weighing (200-250 g) were randomly divided into 2 groups of 20 each. Under general anesthesia, reproducible, deep, partial-thickness, thermal burn injury was created by 1-cm aluminum template on the dorsal aspect of the body of each animal by heating the template at 80 °C for 10 seconds. Alternate rats were assigned to 1 of the 2 groups to minimize the difference of timing of the burn. Sadat-Habdan mesenchymal stimulating peptide 10 mg was applied on daily burn area, covered with a nonabsorbent dressing. All animals were kept in similar standard laboratory conditions. Its application continued 14 days as described by the inventors, and burned areas were photographed. On day 15, blood was collected from the animals for serum albumin levels, and the animals were killed, then the entire burn areas were excised for biopsy for general morphology and histopathology.

RESULTS

There were no deaths among groups. The majority of the animals showed good to excellent healing compared with the control group. Clinical pictures revealed better healing in the SHMSP-treated group. Quantitative and qualitative analyses of images revealed significant contraction of burned areas. Image analysis showed that improved healing in the form of exaggerated fibroplasia in 19 of 20 in the study group and 11 of 20 in the control group. Regeneration of the panniculous muscle layer was observed in 19 of 20 of the study group and 5 of 20 of the control group. The mean vessel index in the study group was 53.18 ± 4.74 mm(2) and in the control group 23.7 ± 6.37 mm(2) (P < 0.001; confidence interval, 25.88-33.04), whereas the mean of vessel area density was 24.76 ± 7.35 versus 8.68 ± 4.04 mm(2) (P < 0.001; confidence interval, 12.28-19.88) in the control group. Histopathologic analysis by hematoxylin-eosin stain, CD31, and factor VIII stains showed significant angiogenesis in the quantity and quality of the new blood vessels in the study group compared with the control group.

CONCLUSIONS

Sadat-Habdan mesenchymal stimulating peptide has potential of early healing of experimentally produced burns in rats. Healing was effective and better in the study group compared with the control group, in qualitative and quantitative measures.

Topical pluronic F-127 gel application enhances cutaneous wound healing in rats

Pluronic F-127 gel is used as vehicle for various topical applications. In the present study, effects of topical application of pluronic F-127 gel were evaluated in cutaneous wound healing in Wistar rats. Normal saline solution and pluronic F-127 gel (25%) were applied topically on open excision wounds for 14 days. Photography, determination of percentage wound contraction, and collection of granulation tissue were done on days 3, 7, 11 and 14 post-wounding. Topical application of gel (once daily) significantly increased the wound closure on days 11 and 14. The gel application increased the expressions of vascular endothelial growth factor (VEGF) and transforming growth factor-beta1 (TGF-β₁) on days 3 and 7. Histopathologically, more leukocyte infiltration followed by well formed granulation tissue with marked fibroblast proliferation was evident in the gel-treated group, as compared to the saline-treated control group. Immunohistochemistry of CD31 on day 7 revealed significant higher microvessel density in gel-treated wounds. Picrosirius staining demonstrated higher collagen fraction in gel-treated wounds. Thus, from the results, it could be concluded that pluronic F-127 gel has a mild inflammatory nature and enhanced the healing by stimulating expression of VEGF and TGF-β₁.

Effect of blockade of the EGF system on wound healing in patients vaccinated with CIMAvax® EGF

Background

The epidermal growth factor receptor (EGFR) signaling system is frequently unbalanced in human malignancies due to increased ligand production, receptor overexpression, receptor mutations, and/or cross-talk with other receptor systems. For this reason, the EGFR is an attractive target for anticancer therapy. The epidermal growth factor also plays an important role in regulating multiple facets of cutaneous wound healing, including inflammation, wound contraction, proliferation, migration, and angiogenesis. In the Center of Molecular Immunology, a cancer vaccine is produced (CIMAvax® EGF) that blocks the binding of EGF to its receptor. This blockade causes a significant inverse association between the anti-EGF antibody titers and EGF concentration. Around 1,500 patients with non-small cell lung cancer have been treated, showing that this vaccine is safe, immunogenic, increases survival and improves quality of life. Taking into account the therapeutic benefits of CIMAvax® EGF vaccination and the role of EGF-EGFR system in the wound healing process, we decided to conduct a retrospective research with the aim of determining the effect to the CIMAvax® EGF vaccine on the wound healing process in patients undergoing surgical treatment.

Methods

Medical records of 452 vaccinated patients were reviewed and only six patients receiving surgical treatment were identified. Further information about these six patients was obtained from source documents, including medical records and operative reports using an observational list that included different variables. Post-surgical wound healing complications were identified using the National Cancer Institute Common Toxicity Criteria for Adverse Events (NCI-CTC) version 3.0.

Results

None of the six patients operated on presented adverse events related to the wound healing, that is to say, no wound dehiscence, wound infection, delayed wound healing, fistula formation, abscess formation or hemorrhage/bleeding associated with surgery during treatment with CIMAvax® EGF occurred.

Conclusions

These results suggest that the use of CIMAvax® EGF does not produce a deleterious effect in the wound healing process.

The pivotal role of vascularization in tissue engineering

Vascularization is one of the great challenges that tissue engineering faces in order to achieve sizeable tissue and organ substitutes that contain living cells. There are instances, such as skin replacement, in which a tissue-engineered substitute does not absolutely need a preexisting vascularization. However, tissue or organ substitutes in which any dimension, such as thickness, exceeds 400 μm need to be vascularized to ensure cellular survival. Consistent with the wide spectrum of approaches to tissue engineering itself, which vary from acellular synthetic biomaterials to purely biological living constructs, approaches to tissue-engineered vascularization cover numerous techniques. Those techniques range from micropatterns engineered in biomaterials to microvascular networks created by endothelial cells. In this review, we strive to provide a critical overview of the elements that must be considered in the pursuit of this goal and the major approaches that are investigated in hopes of achieving it.

Recent advances in topical wound care

There are a wide variety of dressing techniques and materials available for management of both acute wounds and chronic non-healing wounds. The primary objective in both the cases is to achieve a healed closed wound. However, in a chronic wound the dressing may be required for preparing the wound bed for further operative procedures such as skin grafting. An ideal dressing material should not only accelerate wound healing but also reduce loss of protein, electrolytes and fluid from the wound, and help to minimize pain and infection. The present dictum is to promote the concept of moist wound healing. This is in sharp contrast to the earlier practice of exposure method of wound management wherein the wound was allowed to dry. It can be quite a challenge for any physician to choose an appropriate dressing material when faced with a wound. Since wound care is undergoing a constant change and new products are being introduced into the market frequently, one needs to keep abreast of their effect on wound healing. This article emphasizes on the importance of assessment of the wound bed, the amount of drainage, depth of damage, presence of infection and location of wound. These characteristics will help any clinician decide on which product to use and where,in order to get optimal wound healing. However, there are no ‘magical dressings’. Dressings are one important aspect that promotes wound healing apart from treating the underlying cause and other supportive measures like nutrition and systemic antibiotics need to be given equal attention.

The combined effect of recombinant human epidermal growth factor and erythropoietin on full-thickness wound healing in diabetic rat model

Diabetic wound is a chronic wound in which normal process of wound healing is interrupted. Lack of blood supply, infection and lack of functional growth factors are assumed as some of the conditions that lead to non-healing environment. Epidermal growth factor (EGF) acts primarily to stimulate epithelial cell growth across wound. Erythropoietin (EPO) is a haematopoietic factor, which stimulates the production, differentiation and maturation of erythroid precursor cells. This study hypothesised combining these two factors, non-healing process of diabetic wound will be compensated and eventually lead to acceleration of wound healing compared with single growth factor treatment. A total of 30 diabetic Sprague-Dawley rats were divided into three treatment groups (single treatment of rh-EPO or rh-EGF or combined treatment on a full-thickness skin wound). To assess the wound healing effects of the components, the wound size and the healing time were measured in each treatment groups. The skin histology was examined by light microscopy and immunohistochemical analysis of proliferating markers was performed. The combined treatment with rh-EPO and rh-EGF improved full-thickness wound significantly (P < 0·05) accelerating 50% healing time with higher expression of Ki-67 compared with single growth factor-treated groups. The combined treatment failed to accelerate the total healing time when compared with single growth factor treatments. However, the significant improvement were found in wound size reduction in the combined treatment group on day 4 against single growth factor-treated groups (P < 0·05). This study demonstrated that the combined treatment of rh-EPO and rh-EGF improved the wound healing possibly through a synergistic action of each growth factor. This application provides further insight into combined growth factor therapy on non-healing diabetic wounds.

Effects of an epidermal growth factor receptor-based cancer vaccine on wound healing and inflammation processes in murine experimental models

Anti-epidermal growth factor receptor (EGFR) therapies have been proven clinically effective for a variety of epithelial tumours. Vaccination of mice with the extracellular domain (ECD) of autologous EGFR overcomes the tolerance to self-EGFR and has antimetastatic effect on EGFR+ tumour. Because EGF/EGFR-signalling plays an important role in the inflammation stage of wound healing, the main objective of this study was to explore the possible role of murine (m) EGFR-ECD vaccine in the croton-oil-induced ear oedema and wound healing process in mice as autologous experimental models, mimicking the possible post-surgical wound complication in patients treated with human EGFR-ECD/VSSP vaccine. Mice were intramuscularly immunised four times; biweekly with the mEGFR-ECD/VSSP/Mont. Seven days later, an 8 mm diameter, full-thickness skin wound was created on the back of each animal. Immunisation induced a strong specific humoral response against the mEGFR-ECD protein and a DTH dose-response curve but interestingly, animals treated with mEGFR-ECD/VSSP/Mont had similar inflammatory and healing speed responses compared to control ones. These data suggest that application of mEGFR-ECD/VSSP vaccine as a therapeutic approach in cancer patients could not elicit a poor healing process after surgery.

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

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

Topical embryonic stem cells enhance wound healing in diabetic rats

The effects of embryonic stem cells (ESCs) on diabetic wound healing were investigated using an excisional skin wound model in 110 diabetes-induced rats. We transplanted a clonal population of ESCs (5 × 10(6)) by topical injection into full thickness skin wounds. Four study groups were used; nondiabetic rats as a control, non-insulin controlled diabetic rats not treated with ESCs, insulin controlled diabetic rats not treated with ESCs, and insulin controlled diabetic rats treated with ESCs. Five rats in each experimental group were sacrificed on days 1, 5, 10, 15, and 20 after wounding. Wounds images were acquired daily and wound sizes were calculated. We measured the mRNA levels of epidermal growth factor (EGF) and vascular endothelial growth factor (VEGF), and fibronectin levels in extracellular matrix, and assessed wound healing by assessing histological parameters of epidermal regeneration, granulation tissue thickness, and angiogenesis. In the ESC-treated group, wound sizes were significantly smaller than in the insulin controlled diabetic group not treated with ESCs on days 5 and 10 (p < 0.05), and EGF and VEGF levels were markedly higher on days 5 and 10, fibronectin levels on day 5 after injection. All histological scores in the ESC-treated group were significantly higher than those of the insulin controlled diabetic group on day 5 (p < 0.05). Our results shows that topical ESCs enhance diabetic wound healing during the early stage, and suggest that ESCs transplantation offers a novel therapeutic modality for the treatment of diabetic wounds.

Functions of rhomboid family protease RHBDL2 and thrombomodulin in wound healing

The expression of thrombomodulin (TM), a membrane glycoprotein, is upregulated in neoepidermis during cutaneous wound healing. Rhomboid-like-2 (RHBDL2), an intramembrane serine protease, specifically cleaves TM at the transmembrane domain and causes the release of soluble TM (sTM). However, the physiological functions of TM and RHBDL2 in wound healing remain unclear. We demonstrated that both TM and RHBDL2 are upregulated in HaCaT cells stimulated by scratch wounds; furthermore, increased sTM was found in culture medium. Conversely, inhibition of RHBDL2 by 3,4-dichloroisocoumarin (DCI) or short hairpin RNA significantly inhibited wound-induced TM ectodomain shedding and wound healing. Both conditioned media from multiple-scratch-wounded HaCaT and recombinant sTM accelerated wound healing in HaCaT cells; such effects were abrogated by anti-TM antibodies. The RNA released from injured cells is involved in the induction of TM and RHBDL2. RHBDL2 and sTM were upregulated in ex vivo tissue culture of the injured skin. Furthermore, DCI inhibited sTM production and wound healing; this was reversed by recombinant sTM in mice. Thus, RHBDL2 and TM have important roles in wound healing via the release of sTM from keratinocytes; this may function as an autocrine/paracrine signal promoting wound healing.

Bone regeneration in osseous defects using hydroxyapatite graft and the extent of ossification in osseous defects treated without grafts: a comparative evaluation

OBJECTIVES

Objective of this study is to evaluate the new bone formation in bony defects following insertion of hydroxyapatite graft and to compare the efficacy and regenerative potential of this bone graft material.

METHOD

The patients having osseous defects after surgery were selected. Preoperatively a brief history, examination, relevant blood investigation and radiographs were taken. Post operative observation period of 6 months was planned. Radiographic and bone scintigraphic (isotope study of bone activity) evaluation of bone specimens was completed in defined time.

RESULTS

Radiographic evaluation indicated increased calcification surrounding the material, indicative of acceptance of the graft to the bone. Bone scintigraphic evaluation indicated area of increased bone metabolism and is evidenced as area of increased radiotracer uptake, namely 'hot spots' (active bone formation).

CONCLUSION

It can be concluded that the hydroxyapatite graft met the clinical requirement of a bone substitute material which is biocompatible and non-allergic. The use of this material is advantageous over other bone grafts because of simplicity of application, cost effectiveness and easy availability. Due to its microstructure, complete resorption and neo bone formation took place during the course of this study.

Platelet gel in the treatment of cutaneous ulcers: the experience of the Immunohaematology and Transfusion Centre of Parma

BACKGROUND

Platelet gel is being ever more frequently used to promote healing of cutaneous ulcers. However, the factors that determine the often variable clinical outcome of this procedure are still incompletely understood.

AIMS

The aims of this study were to demonstrate that platelet gel, even when obtained under strictly controlled conditions, produces highly variable outcomes in patients with cutaneous ulcers and to propose a method for in vitro standardisation of the biological properties of platelet gel. MATERIAL AND METHODS.: Patients were enrolled on the basis of a pre-defined protocol. Platelet concentrate was produced with standard methods, with a variability in platelet count among the different samples of less than 10%. The platelet gel for clinical use was obtained, under strictly standardized conditions, by adding thrombin and calcium gluconate to the concentrates. For in vitro studies, platelet gel, obtained from platelet-rich plasma from four donors, was frozen and thawed twice so as to increase gel contraction. The supernatant was used to modify cell proliferation, protein synthesis, and the expression of selected genes in cultures of human diploid fibroblasts.

RESULTS

Seventeen patients (aged 44-78 years) with ulcers (4 diabetic, 11 vascular, 1 post-traumatic, 1 decubitus) were treated with platelet gel (4 autologous, 13 homologous). Complete re-epithelialisation of four ulcers (1 diabetic, 1 post-traumatic, 2 vascular) was obtained after applications of platelet gel (2 autologous, 2 homologous); in 11 other cases there was a greater than 50% reduction in the size of the ulcer. Two patients had no benefit. The supernatant of the platelet gel was able to promote dose-dependent proliferation and changes in gene expression as well as in metabolic activities related to protein synthesis.

CONCLUSIONS

Although the use of platelet gel in the treatment of cutaneous ulcers is increasing, and conditions for its production are better standardised, very considerable variability of clinical outcomes is still observed, even within single centres, suggesting that there are differences in biological properties of platelet concentrates from individual patients which cannot be readily controlled with current techniques. The biological effects of the platelet gel supernatant described in this article may provide the basis for a simple biological validation of platelet preparations before their clinical use, so as to reduce this potentially important source of variability.

The role of endothelin-1 in the pathogenesis of idiopathic pulmonary fibrosis

The endothelin system participates in a number of critical biologic pathways, including normal wound healing. In addition, emerging basic science, and animal and human data all suggest that endothelin-1 (EDN1, also known as ET-1) is a potentially important contributor in the pathobiology of fibrosing disorders, including those that affect the lung. For example, EDN1 drives fibroblast activation, proliferation, as well as differentiation into myofibroblasts - processes that lead to excessive collagen deposition. Patients with idiopathic pulmonary fibrosis (IPF) have increased levels of EDN1 in both their bronchoalveolar lavage fluid and lung tissue. Beyond this, rodent models suggest that endothelin receptor antagonists can limit bleomycin-induced lung fibrosis. This suggests a biologic rationale for the blockade of EDN1 to limit the evolution of lung fibrosis in humans. Initial results from a trial examining the efficacy of a dual endothelin receptor antagonist suggest that this approach may delay disease progression in a subset of patients with IPF.

Matrix therapy in regenerative medicine, a new approach to chronic wound healing

Nonhealing wounds remain a major health problem whose treatment is challenging and costly. Treatments based on cells or growth factors are still not very effective. We developed an entirely novel strategy consisting in treatment of the wound-tissue matrix with biopolymers engineered to mimic heparan sulfates called OTR4120. This compound was dextran polymer with sulfated and carboxymethyl groupments. After binding to matrix proteins, the heparan-sulfate-mimicking polymer protects the microenvironment, maintaining the normal production of signals and growth factors needed for healing to occur. Here, we show that a specific biopolymer accelerates ulcer closure and improves re-epithelialization and dermal-matrix-component remodeling. OTR4120 treatment was associated with faster maturation of epidermal structures, most notably regarding the number of epithelial-cell layers, and with an appearance that more closely resembled normal skin. Treatment had also a main effect on collagen I and III expression. Necrotic skin ulcers induced in mice with doxorubicin recovered normal collagen levels and organization, with no evidence of fibrosis. Thus, appropriate polymer-based matrix therapy is a valid and simple alternative to regenerative medicine.

The effect of adipose-derived stem cells on ischemia-reperfusion injury: immunohistochemical and ultrastructural evaluation

BACKGROUND

Advances in the treatment of reperfusion injury have created an opportunity for plastic surgeons to apply these treatments to flaps and implanted tissues. The authors examined the direct and indirect effects of adipose-derived stem cells on ischemia-reperfusion injury on a skin flap model to determine the in vivo differentiation of adipose-derived stem cells to endothelial cells; the levels of vascular endothelial growth factor (VEGF), transforming growth factor-beta, and fibroblast growth factor; and the ultrastructural changes apparent with scanning electron microscopy to clarify the initial events and the following cascades.

METHODS

Two identical cranial based random flaps with a dimension of 1 x 5 cm were elevated on the dorsums of 20 ICR mice. The left flap was designated as the control and the right flap was injected with adipose-derived stem cells. The flaps were then subjected to 6 hours of ischemia by clamping the pedicle, and then reperfusion.

RESULTS

The mean viable flap length in the control and experimental groups was 15.2 +/- 3.4 mm and 24.4 +/- 2.9 mm, respectively. The mean viable flap area in the control and experimental groups was 12.9 +/- 4.1 mm and 21.8 +/- 3.7 mm, respectively. The in vivo differentiation of adipose-derived stem cells to endothelial cells was observed. The immunohistochemical stainings, VEGF, transforming growth factor-beta, and fibroblast growth factor revealed increased levels in the experimental groups. Scanning electron microscopy indicated mild injury in the experimental group.

CONCLUSIONS

The adipose-derived stem cells could prevent ischemia-reperfusion injury, mainly by regulating the growth factors. Although VEGF was the foremost inhibitor of injury, the overall cascade was enhanced by adipose-derived stem cells, with the help of the other growth factors.

The science of wound bed preparation

The concept of wound bed preparation (WBP) heralded a new era in terms of how we treat wounds. It emphasized the difference between acute and chronic wounds, and it cemented the idea that the processes involved in the healing of acute wounds do not apply completely to the healing of chronic wounds. The arbitrary division of the normal healing process into the phases of hemostasis, inflammation, proliferation, and maturation addresses the events in acute wound healing. We have realized that the impediments to healing in chronic wounds lead to a failure to progress through these phases and are independent factors that make the chronic wound a much more complex condition. A major advance in resolving or addressing the chronic wound has been the concept of WBP. WBP allows us to address the problems of wound healing individually the presence of necrotic tissue, hypoxia, high bacterial burden, corrupt matrix, and senescent cells within the wound bed. In WBP we can optimize our therapeutic agents to accelerate endogenous healing or to increase the effectiveness of advanced therapies.

Which is the better option: recombinant human PDGF-BB 0.01% gel or standard wound care, in diabetic neuropathic large plantar ulcers off-loaded by a customized contact cast?

This study compares the efficacy of 0.01% rh-PDGF-BB with standard wound care in 20 patients with diabetes mellitus with neuropathic large plantar ulcers off-loaded with modified total contact cast. The incidence, duration and rate of healing were compared. An accelerated rate of healing in rhPDGF group was observed.

Wound healing dressings and drug delivery systems: a review

The variety of wound types has resulted in a wide range of wound dressings with new products frequently introduced to target different aspects of the wound healing process. The ideal dressing should achieve rapid healing at reasonable cost with minimal inconvenience to the patient. This article offers a review of the common wound management dressings and emerging technologies for achieving improved wound healing. It also reviews many of the dressings and novel polymers used for the delivery of drugs to acute, chronic and other types of wound. These include hydrocolloids, alginates, hydrogels, polyurethane, collagen, chitosan, pectin and hyaluronic acid. There is also a brief section on the use of biological polymers as tissue engineered scaffolds and skin grafts. Pharmacological agents such as antibiotics, vitamins, minerals, growth factors and other wound healing accelerators that take active part in the healing process are discussed. Direct delivery of these agents to the wound site is desirable, particularly when systemic delivery could cause organ damage due to toxicological concerns associated with the preferred agents. This review concerns the requirement for formulations with improved properties for effective and accurate delivery of the required therapeutic agents. General formulation approaches towards achieving optimum physical properties and controlled delivery characteristics for an active wound healing dosage form are also considered briefly.

Epidermal growth factor therapy and wound healing--past, present and future perspectives

The role ofepidermal growth factor (EGF) has been extensively investigated in normal and pathological wound healing. It is implicated in keratinocyte migration, fibroblast function and the formation of granulation tissue. Since the discovery of EGF, the first growth factor to be isolated, over 45 years ago, growth factor therapy has progressed into clinical practice in the treatment ofwounds. The investigation EGF in wound healing has progressed from the treatment of acute wounds, to its limited effect in chronic wounds. EGF is readily degraded in the chronic wound environment, but with the recent focus of research in new drug delivery systems that are able to protect and stabilise the protein, the potential healing effects of EGF are at the forefront of research. In this review, the history of EGF and wound healing research is considered, as are current and future therapeutic options.

Use of microparticulate systems to accelerate skin wound healing

Rapid and proper healing is important in the treatment of skin wounds. The dressing achieves the functions of the natural skin by protecting the wound area from the bulk loss of tissue and creating an effective barrier to outside contaminants without increasing the bacterial load on the wound surface. There are many wound dressings available on the market which can be used in the healing process. Different dressings have been used according to the condition of the wound and the phases of wound healing. Biodegradable polymers are being widely used in drug delivery and also in wound healing. These polymers that are applicable as a wound dressing protect the wound site against unwanted external effects, inhibit wound contraction, and, if possible, stimulate the healing process. Micro- and nanoparticulates are currently being evaluated as a potential drug delivery in clinical applications. Growth factors also play a vital role in wound healing. Polymers used in wound healing act as sustained release vehicles for growth factors. Controlled release of growth factors from microspheres has provided a higher degree of healing in the wound areas. This review is intended to provide information regarding the various formulations and microparticulate systems used in wound healing.

Microgravity and the implications for wound healing

Wound healing is a sophisticated response ubiquitous to various traumatic stimuli leading to an anatomical/functional disruption. The aim of present article was to review the current evidence regarding the effects of microgravity on wound healing dynamics. Modulation of haemostatic phase because of alteration of platelet quantity and function seems probable. Furthermore, production of growth factors that are released from activated platelets and infiltration/function of inflammatory cells seem to be impaired by microgravity. Proliferation of damaged structures is dependent on orchestrated function of various growth factors, for example transforming growth factors, platelet-derived growth factor and epidermal growth factor, all of which are affected by microgravitational status. Moreover, gravity-induced alterations of gap junction, neural inputs, and cell populations have been reported. It may be concluded that different cellular and extracellular element involved in the healing response are modified through effect of microgravity which may lead to impairment in healing dynamics.

Preparation of highly concentrated and white cell-poor platelet-rich plasma by plateletpheresis

BACKGROUND AND OBJECTIVES

Contaminating white blood cells (WBC) contribute remarkably to the overall growth factor content of locally applicable platelet-rich plasma (PRP) or platelet (PLT) gel and change the relative proportions of the contained growth factors.

MATERIALS AND METHODS

To study the independent effects of locally applicated highly concentrated PLTs, the development of preparations is needed that contain large amounts of PLTs and no or at least very few leucocytes. Therefore, 20 plateletpheresis procedures were performed in voluntary blood donors to get highly concentrated and extremely WBC-poor plateletpheresis concentrates. The degree of spontaneous PLT activation, the PLT aggregation response to agonists and the level of the growth factor TGF-beta1 (transforming growth factor beta1) were measured immediately after the donation and 1 day later.

RESULTS

The concentrates contained 1.96 +/- 0.36 x 10e11 PLTs per unit in 55.2 +/- 7.9 ml, respectively. In comparison to the donors' blood, the PLT-enrichment factor was 15.3 +/- 5.4. At the same time, the concentrates contained extremely low residual numbers of WBCs (0.8 +/- 3.3 x 10e3/ml). The concentration of the growth factor TGF-beta1 was 743.2 +/- 243.9 ng/ml. On day 1, the PLT concentration and the TGF-beta1 content of the PLT concentrates had not decreased.

CONCLUSIONS

In summary, plateletpheresis is suited to provide PRP products with higher concentrations of human platelets and platelet-derived growth factors than previously reported PRP preparation methods but with extremely low numbers of contaminating leucocytes.

The science of wound bed preparation

The concept of wound bed preparation (WBP) heralded a new era in terms of how we treat wounds. It emphasized the difference between acute and chronic wounds, and it cemented the idea that the processes involved in the healing of acute wounds do not apply completely to the healing of chronic wounds. The arbitrary division of the normal healing process into the phases of hemostasis, inflammation, proliferation, and maturation addresses the events in acute wound healing. We have realized that the impediments to healing in chronic wounds lead to a failure to progress through these phases and are independent factors that make the chronic wound a much more complex condition. A major advance in resolving or addressing the chronic wound has been the concept of WBP. WBP allows us to address the problems of wound healing individually-the presence of necrotic tissue, hypoxia, high bacterial burden, corrupt matrix, and senescent cells within the wound bed. In WBP we can optimize our therapeutic agents to accelerate endogenous healing or to increase the effectiveness of advanced therapies.

Neurovascular factors in wound healing in the foot skin of type 2 diabetic subjects

OBJECTIVE

Delayed wound healing in diabetic patients without large-vessel disease has been attributed to microvascular dysfunction, neuropathy, and abnormal cellular and inflammatory responses. The role of these abnormalities has mainly been examined in animal models. Few studies have been undertaken in diabetic patients, and those that have are limited due to analysis in wounds from chronic ulcers. In this study, we quantified the rate of wound healing in relation to skin neurovascular function and structure following a dorsal foot skin biopsy in type 2 diabetes.

RESEARCH DESIGN AND METHODS

Twelve healthy control subjects and 12 type 2 diabetic subjects with neuropathy but without macrovascular disease were studied. We quantified rate of wound healing and related it to skin microvascular function (laser Doppler imager [LDI](max)), blood vessel density, small nerve fiber function (LDI(flare)) and nerve fiber density, vascular endothelial growth factor (VEGF) and its receptor (FLK1), and hypoxia-inducible factor (HIF)-1alpha expression.

RESULTS

The rate of wound closure was identical between control subjects and diabetic patients despite a significant reduction in maximum hyperemia (LDI(max)), epidermal and dermal VEGF-A, and epidermal and dermal blood vessel VEGFR-2 expression as well as the neurogenic flare response (LDI(flare)) and dermal nerve fiber density. There was no significant difference in HIF-1alpha and dermal blood vessel density between control subjects and diabetic patients.

CONCLUSIONS

In conclusion, the results of this study suggest that wound closure in subjects with type 2 diabetes is not delayed despite significant alterations in neurovascular function and structure.

Collagen membranes loaded with collagen-binding human PDGF-BB accelerate wound healing in a rabbit dermal ischemic ulcer model

Studies have shown that exogenous platelet-derived growth factor-BB (PDGF-BB) could accelerate the ulcer healing, but the lack of efficient growth factor delivery system limits its clinical application. Our previous work has demonstrated that the native human PDGF-BB was added a collagen-binding domain (CBD), TKKTLRT, to develop a collagen-based PDGF targeting delivery system. Here, we showed that this CBD-fused PDGF-BB (CBD-PDGF) could bind to collagen membrane efficiently. We used the rabbit dermal ischemic ulcer model to study the effects of CBD-PDGF loaded on collagen membranes. Results revealed that this system maintained a higher concentration and stronger bioactivity of PDGF-BB on the collagen membranes and promoted the re-epithelialization of dermal ulcer wounds, the collagen deposition, and the formation of capillary lumens within the newly formed tissue area. It demonstrated that collagen membranes loaded with collagen-targeting human PDGF-BB could effectively promote ulcer healing.

Sinus floor elevation using autogenous bone or bone substitute combined with platelet-rich plasma

OBJECTIVE

Sinus augmentation is a common approach for patients with severe alveolar ridge atrophy. However, autogenous bone sometimes results in donor site complications. Bone substitutes with platelet-rich plasma (PRP) promote early bone formation with autogenous bone. Use of PRP on autogenous bone and a bovine bone substitute were investigated in this split-mouth animal study.

STUDY DESIGN

Premolars were extracted from minipigs. Each animal received sinus augmentation using a lateral approach with simultaneous insertion of 3 implants in each site. Groups were randomized using autogenous bone alone and combined with PRP or a bovine hydroxyapatite alone in combination with PRP.

RESULTS

Microradiographic findings in the autogenous group did not show significantly different rates by using autogenous bone alone or combined with PRP. Using the bovine hydroxyapatite as augmentation material only at 8 weeks, a nonsignificant effect in the PRP group could be seen. At all other observation periods, no significant influence was observed.

CONCLUSION

No significant influence of PRP was found.

Growth factors in the treatment of diabetic foot ulcers: new technologies, any promises?

Foot ulcers remain a common problem, leading to increased morbidity in patients with diabetes. Despite the progress that has been achieved in revascularization techniques as well as in off-loading to relieve high-pressure areas, diabetic foot wounds remain a clinical challenge. Growth factors are a major technological advance that promised to change the face of wound healing. The most important of growth factors are recombinant human platelet-derived growth factor-BB and granulocyte colony-stimulating factor. The former has been approved by the FDA for the treatment of neuropathic ulcers when there is adequate blood supply. The latter is less demonstrably useful. Advances include methods of delivering growth factors.

Effects of the basic fibroblast growth factor and its anti-factor in the healing and collagen maturation of infected skin wound

PURPOSE: The infection is one of the main factors that affect the physiological evolution of the surgical wounds. The aim of this work is to evaluate the effects of fibroblast growth factor (FGFâ) and anti-FGFâ in the healing, synthesis and maturation of collagen when topically used on infected skin wounds of rats. METHODS: An experimental study was perfomed in 60 male Wistar rats. All animals were divided in two groups (A and B). Each group was divided in three subgroups A1, B1; A2, B2 and A3, B3. After anesthesia with pentobarbital, two open squared wounds (1cm²), 4cm distant to each other, were done in the dorsal skin of all the rats. In group A (n=30) the wounds were contaminated with multibacterial standard solution, and in group B(n=30) the wounds were maintained sterile. These wounds were named F1 (for inflammation analysis) and F2 (for collagen study). The open wounds of A1 and B1 rats were topically treated with saline solution, A2 and B2 were treated with FGFâ and subgroups A3 and B3 were treated with FGFâ and anti-FGFâ. The rats were observed until complete epitelization of F2 wounds for determination of healing time and the expression of types I and III collagen, using Picro Sirius Red staining. Inflammatory reaction in F1 wounds was studied using hematoxilineosin staining. The three variable was measured by the Image Pro-Plus Média Cybernetics software. The statistical analysis was performed by ANOVA and Tukey test, considering p<0.05 as significant. RESULTS: It was observed that infection retarded significantly (p<0.05) the time of wound scarring and the topical application of FCFb reverted the inhibition of healing caused by bacteria. The inflammatory reaction was greater in the subgroup B2 than in B1 and A3, and the difference was significant (p<0.05). It was observed greater expression of type I collagen in all the subgroups treated with FCFb, when compared with the untreated subgroups. Type III collagen was significantly decreased in wounds of B3 rats, comparing to the other subgroups. CONCLUSIONS: The FCFb accelerated the healing of open infected wounds and contributed with maturation of collagen, enhancing the type I collagen density. The anti-FCFb antibody was able to attenuate the production of both type I and III collagen.

Effect of xenogenic immobilized bone matrix on the course of wound process

The effect of xenogenic demineralized bone matrix as a component of film coating on healing of a full-thickness skin wound was studied. Regenerative processes were more intensive in wounds dressed with a complex film containing demineralized bone matrix than in uncovered wounds and wounds covered with films without bone matrix. Film coating with antibiotics suppressed the development of wound microflora. In vitro experiments demonstrated different effects of demineralized bone matrix on some enzymes in rat skin and liver homogenates. Biological activity of xenogenic demineralized bone matrix as a component of wound coating is shown.

Expression of bone matrix proteins during the osseus healing of topical conditioned implants: an experimental study

OBJECTIVES

Osseointegration of implants depends on time and local bone conditions regarding quality and quantity. This led to the bone classification by Lekholm et al. The aim of the present study was to follow the expression of bone matrix proteins during the phase of osseointegration after conditioning of the bone bed by means of immunohistochemistry.

METHODS

In the porcine frontal skull, implant beds of identical size were created. Before placement of the implants (Ankylos 4 x 3.5 mm), the implant beds were conditioned using bone condensation (cond), an osteoinductive collagen (Co) and platelet-rich plasma (PRP). These conditioning methods were compared with standard procedure. The animals were sacrificed after 2, 4 and 8 weeks. The specimens were then analyzed by light microcopy and immunohistochemistry for expression of bone morphogenic proteins (BMP)2, procollagen I and osteocalcin (OC).

RESULTS

Light microscopy revealed an initial effect of condensation and the bovine collagen at 2 weeks in comparison with the standard group. The PRP did not achieve a significant effect. At 8 weeks, the results of the standard, bone condensation and the bovine collagen group had aligned. The PRP group showed a significantly lower bone-implant contact (BIC) (P=0.003) compared with the standard group. BMP2 expression was significantly higher in all evaluated test groups at 4 and 8 weeks, as well as at 2 weeks in the condensation group. The procollagen I expression at 2 weeks was significantly increased for PRP and lower in the collagen and condensation group compared with standard procedure. Values for 4 and 8 weeks were slightly higher than in the standard group. No significant differences were obvious in the OC group at any time.

CONCLUSIONS

During the initial healing phase, an effect of the evaluated methods of topical bone conditioning can be demonstrated by differences in the expression of BMP2 and procollagen I. These findings had leveled at 8 weeks and were, in contrast, not detectable in the expression of OC or by means of light microscopy.