Wound healing. The role of platelet-derived growth factor and transforming growth factor beta

Advances and Challenges in Targeting TGF-β Isoforms for Therapeutic Intervention of Cancer: A Mechanism-Based Perspective

The TGF-β family is a group of 25 kDa secretory cytokines, in mammals consisting of three dimeric isoforms (TGF-βs 1, 2, and 3), each encoded on a separate gene with unique regulatory elements. Each isoform plays unique, diverse, and pivotal roles in cell growth, survival, immune response, and differentiation. However, many researchers in the TGF-β field often mistakenly assume a uniform functionality among all three isoforms. Although TGF-βs are essential for normal development and many cellular and physiological processes, their dysregulated expression contributes significantly to various diseases. Notably, they drive conditions like fibrosis and tumor metastasis/progression. To counter these pathologies, extensive efforts have been directed towards targeting TGF-βs, resulting in the development of a range of TGF-β inhibitors. Despite some clinical success, these agents have yet to reach their full potential in the treatment of cancers. A significant challenge rests in effectively targeting TGF-βs' pathological functions while preserving their physiological roles. Many existing approaches collectively target all three isoforms, failing to target just the specific deregulated ones. Additionally, most strategies tackle the entire TGF-β signaling pathway instead of focusing on disease-specific components or preferentially targeting tumors. This review gives a unique historical overview of the TGF-β field often missed in other reviews and provides a current landscape of TGF-β research, emphasizing isoform-specific functions and disease implications. The review then delves into ongoing therapeutic strategies in cancer, stressing the need for more tools that target specific isoforms and disease-related pathway components, advocating mechanism-based and refined approaches to enhance the effectiveness of TGF-β-targeted cancer therapies.

The Growth Factor Release from a Platelet-Rich Plasma Preparation Is Influenced by the Onset of Guttate Psoriasis: A Case Report

The involvement of platelets in immune and inflammatory processes is generally recognized; nevertheless, in psoriasis, their role is not clearly understood. We studied the in vitro growth factor release from a platelet-rich plasma preparation, the concentrated growth factors (CGF), in a case of a psoriasis subject three days before the onset of the papule. The CGF clots were incubated in a cell culture medium without growth supplements for 5 h and 1, 3, 6, 7, and 8 days, and the release kinetics of PDGF-AB, VEGF, TNF-α, and TGF-β1 were evaluated. The data, based on the results obtained during the case study, report a general increase in growth factor release in the psoriasis subject with respect to the healthy control, indicating an imbalance of growth factor production from blood cells. Although the results should be validated in the future, they show new aspects of this dermatological pathology, opening new possibilities both as the method of study, using CGF, and the involvement of platelets and growth factors in its development and maintenance.

Regenerative potential of platelets in patients with chronic kidney disease

INTRODUCTION

Chronic kidney disease (CKD) is a systemic disease affecting many organs. Progression of renal failure aggravates ongoing inflammation and increases oxidative stress. In the final stage of CKD, it is necessary to use renal replacement therapy. A side effect of dialysis therapy is the synthesis of proinflammatory factors and increased oxidative stress, which activates platelets and immune cells.

AIM OF THE STUDY

To determine the regenerative potential of platelets in patients with CKD based on the analysis of the relationships between substances with potential regenerative action, as well as analysis of the influence of the type of renal replacement therapy used on regeneration of platelets.

MATERIALS AND METHODS

The study group consisted of 117 patients. Based on the type of therapy used, patients were divided into four groups: hemodialysis, peritoneal dialysis, kidney transplant patients, and conservative treatment (30, 30, 27, and 30 patients). The control group consisted of 30 healthy volunteers. The concentrations of IGF-1, TGF-β, and PDGF-B in the blood serum were measured by ELISA methods.

RESULTS

It was shown that renal replacement therapy significantly influences the concentration of platelet growth factors (IGF-1: p = 0.025 and PDGF-B: p = 0.012). There was a relationship between the type of renal replacement therapy and the duration of dialysis, and the concentration of IGF-1, PDGF-B (p < 0.00001, p < 0.001).

CONCLUSIONS

The type of renal replacement therapy has a different effect on the concentration of platelet-derived growth factors IGF-1 and PDGF-B. PD patients had the highest concentrations of all growth factors, and this may be due to the presence of inflammation induced by dialysis-related advanced end-products of glycosylation (AGE).

Coupling between Osseointegration and Mechanotransduction to Maintain Foreign Body Equilibrium in the Long-Term: A Comprehensive Overview

The permanent interaction between bone tissue and the immune system shows us the complex biology of the tissue in which we insert oral implants. At the same time, new knowledge in relation to the interaction of materials and the host, reveals to us the true nature of osseointegration. So, to achieve clinical success or perhaps most importantly, to understand why we sometimes fail, the study of oral implantology should consider the following advice equally important: a correct clinical protocol, the study of the immunomodulatory capacity of the device and the osteoimmunobiology of the host. Although osseointegration may seem adequate from the clinical point of view, a deeper vision shows us that a Foreign Body Equilibrium could be susceptible to environmental conditions. This is why maintaining this cellular balance should become our therapeutic target and, more specifically, the understanding of the main cell involved, the macrophage. The advent of new information, the development of new implant surfaces and the introduction of new therapeutic proposals such as therapeutic mechanotransduction, will allow us to maintain a healthy host-implant relationship long-term.

Deconvoluting the Bioactivity of Calcium Phosphate-Based Bone Graft Substitutes: Strategies to Understand the Role of Individual Material Properties

Calcium phosphate (CaP)-based ceramics are the most widely applied synthetic biomaterials for repair and regeneration of damaged and diseased bone. CaP bioactivity is regulated by a set of largely intertwined physico-chemical and structural properties, such as the surface microstructure, surface energy, porosity, chemical composition, crystallinity and stiffness. Unravelling the role of each individual property in the interaction between the biomaterial and the biological system is a prerequisite for evolving from a trial-and-error approach to a design-driven approach in the development of new functional biomaterials. This progress report critically reviews various strategies developed to decouple the roles of the individual material properties in the biological performance of CaP ceramics. It furthermore emphasizes on the importance of a comprehensive and adequate material characterization that is needed to enhance our knowledge of the property-function relationship of biomaterials used in bone regeneration, and in regenerative medicine in general.

Effects of Platelet-Rich Plasma on Tissue Expansion in Rabbits

BACKGROUND

Tissue expansion has been widely applied in clinic practice. However, the expanded skin is always insufficient for clinical use and how to promote tissue expansion is still a challenge. Platelet-rich plasma (PRP) contains multiple tissue growth factors and has been widely utilized in hard- and soft-tissue augmentation. However, its feasibility to promote tissue expansion has not been explored. The purpose of this study was to evaluate the possible effect of PRP in tissue expansion.

METHODS

Tissue expanders were implanted in the dorsal sides of rabbit ears, and the left and right side were for the PRP group and the control group randomly. The PRP group was injected with 1.0 mL of autologous PRP in the expansion skin and the control group with the same volume of saline solution. The expanders were inflated regularly by injecting saline solution under the same pressure. After the inflation phase, the expansion skin was harvested and the inflation volume, gross specimen, and histological characteristics were assayed and evaluated.

RESULTS

The mean inflation volume of the PRP group was significantly higher than that of the control (p < 0.05). H&E staining of expanded skin sections showed more epidermal cell layers and thicker skin in the PRP group than that in the control group. There were significantly more capillaries in the expanded skin in the PRP group than those from the control group by IHC staining with its marker anti-CD31. A higher level of mRNA expression of VEGF was observed in the PRP group by real-time PCR.

CONCLUSIONS

The present study suggests that PRP plays a pivotal role in tissue expansion and skin proliferation.

NO LEVEL ASSIGNED

This journal requires that authors assign a level of evidence to each article. For a full description of these Evidence-Based Medicine ratings, please refer to the Table of Contents or the online Instructions to Authors. www.springer.com/00266 .

Integration of growth factor gene delivery with collagen-triggered wound repair cascades using collagen-mimetic peptides

Growth factors (GFs) play vital roles in wound repair. Many GF therapies have reached clinical trials, but success has been hindered by safety concerns and a lack of efficacy. Previously, we presented an approach to produce protein factors in wound beds through localized gene delivery mediated by biomimetic peptides. Modification of polyethylenimine (PEI) DNA polyplexes with collagen-mimetic peptides (CMPs) enabled tailoring of polyplex release/retention and improved gene transfer activity in a cell-responsive manner. In this work, CMP-mediated delivery from collagen was shown to improve expression of platelet-derived growth factor-BB (PDGF-BB) and promote a diverse range of cellular processes associated with wound healing, including proliferation, extracellular matrix production, and chemotaxis. Collagens were pre-exposed to physiologically-simulating conditions (complete media, 37°C) for days to weeks prior to cell seeding to simulate the environment within typical wound dressings. In cell proliferation studies, significant increases in cell counts were demonstrated in collagen gels containing CMP-modified polyplex versus unmodified polyplex, and these effects became most pronounced following prolonged preincubation periods of greater than a week. Collagen containing CMP-modified polyplexes also induced a twofold increase in gel contraction as well as enhanced directionality and migratory activity in response to cell-secreted PDGF-BB gradients. While these PDGF-BB-triggered behaviors were observed in collagens containing unmodified polyplexes, the responses withstood much longer preincubation periods in CMP-modified polyplex samples (10 days vs. <5 days). Furthermore, enhanced closure rates in an in vitro wound model suggested that CMP-based PDGF-BB delivery may have utility in actual wound repair and other regenerative medicine applications.

Cytokine-release kinetics of platelet-rich plasma according to various activation protocols

Objectives

This study was conducted to evaluate the cytokine-release kinetics of platelet-rich plasma (PRP) according to different activation protocols.

Methods

Two manual preparation procedures (single-spin (SS) at 900 g for five minutes; double-spin (DS) at 900 g for five minutes and then 1500 g for 15 minutes) were performed for each of 14 healthy subjects. Both preparations were tested for platelet activation by one of three activation protocols: no activation, activation with calcium (Ca) only, or calcium with a low dose (50 IU per 1 ml PRP) of thrombin. Each preparation was divided into four aliquots and incubated for one hour, 24 hours, 72 hours, and seven days. The cytokine-release kinetics were evaluated by assessing PDGF, TGF, VEGF, FGF, IL-1, and MMP-9 concentrations with bead-based sandwich immunoassay.

Results

The concentration of cytokine released from PRP varied over time and was influenced by various activation protocols. Ca-only activation had a significant effect on the DS PRPs (where the VEGF, FGF, and IL-1 concentrations were sustained) while Ca/thrombin activation had effects on both SS and DS PRPs (where the PDGF and VEGF concentrations were sustained and the TGF and FGF concentrations were short). The IL-1 content showed a significant increase with Ca-only or Ca/thrombin activation while these activations did not increase the MMP-9 concentration.

Conclusion

The SS and DS methods differed in their effect on cytokine release, and this effect varied among the cytokines analysed. In addition, low dose of thrombin/calcium activation increased the overall cytokine release of the PRP preparations over seven days, relative to that with a calcium-only supplement or non-activation.

Cite this article: Professor J. H. Oh. Cytokine-release kinetics of platelet-rich plasma according to various activation protocols. Bone Joint Res 2016;5:37–45. DOI: 10.1302/2046-3758.52.2000540

Comparison of the Cellular Composition and Cytokine-Release Kinetics of Various Platelet-Rich Plasma Preparations

BACKGROUND

Variations in formulations used to prepare platelet-rich plasmas (PRPs) result in differences in the cellular composition and biomolecular characteristics.

PURPOSE

To evaluate the cellular composition and the cytokine-release kinetics of PRP according to differences in the preparation protocols.

STUDY DESIGN

Controlled laboratory study.

METHODS

Five preparation procedures were performed for 14 healthy subjects, including 2 manual procedures (single-spin [SS] at 900 g for 5 minutes; double-spin [DS] at 900 g for 5 minutes and then 1500 g for 15 minutes) and 3 methods with commercial kits (Arthrex ACP, Biomet GPS, and Prodizen Prosys). After evaluation of cellular composition, each preparation was divided into 4 aliquots and incubated for 1 hour, 24 hours, 72 hours, and 7 days for the assessment of cytokine release over time. The cytokine-release kinetics were evaluated by assessing platelet-derived growth factor (PDGF), transforming growth factor (TGF), vascular endothelial growth factor (VEGF), fibroblast growth factor (FGF), interleukin-1 (IL-1), and matrix metalloproteinase-9 (MMP-9) concentrations of each aliquot with bead-based sandwich immunoassay.

RESULTS

The DS PRP had a higher concentration of platelets and leukocytes than did the SS PRP. Every PRP preparation exhibited an increase in PDGF, TGF, VEGF, and FGF release when compared with whole blood samples. The FGF and TGF release occurred quickly and decreased over time, while the PDGF and VEGF release was constant and sustained over 7 days. The PDGF and VEGF concentrations were higher in the DS PRP than in the SS PRP, whereas the TGF and FGF concentrations were higher in the SS PRP than in the DS PRP. Biomet GPS had the highest VEGF and MMP-9 concentrations but the lowest TGF concentration. Arthrex ACP had the highest FGF concentration but the lowest PDGF concentration. Prodizen Prosys had the highest IL-1 concentration and higher PDGF concentration than Arthrex ACP.

CONCLUSION

The DS method generally led to a higher concentration of platelet relative to the SS method. However, the cytokine content was not necessarily proportional to the cellular composition of the PRPs, as the greater content could be different between the SS or DS method depending on the type of cytokine.

CLINICAL RELEVANCE

Physicians should select proper PRP preparations after considering their biomolecular characteristics and patient indications.

Role of peptide growth factors in the rhythm of change hair

The article presents current data on the role growth factors play in hair physiology. Based on a review of literature, the authors described the role growth factors play for initiating, suppressing the growth and differentiating hair follicles. According to them, each morphologic development stage of hair follicles is characterized by its own factor expression pattern. Referring to experimental and clinical studies, the authors describe the role some growth factors play for mechanisms promoting the development of androgynous and focal alopecia.

Growth factors and platelet-rich plasma: promising biological strategies for early intervertebral disc degeneration

Intervertebral disc degeneration (IDD) is a complex process with the mechanism not fully elucidated. The current clinical treatments for IDD are mainly focused on providing symptomatic relief without addressing the underlying cause of the IDD. Biological therapeutic strategies to repair and regenerate the degenerated discs are drawing more attention. Growth factor therapy is one of the biological strategies and holds promising prospects. As a promising bioactive substance, platelet-rich plasma (PRP) is considered to be an ideal growth factor "cocktail" for intervertebral disc (IVD) restoration. Results from many in vitro and in vivo studies have confirmed the efficacy of growth factors and PRP in IVD repair and regeneration. It is essential to advance the research on growth factor therapy and associated mechanism for IDD. This article reviews the background of IDD, current concepts in growth factor and PRP-related therapy for IDD. Future research perspectives and clinical directions are also discussed.

Formation of blood clot on biomaterial implants influences bone healing

The first step in bone healing is forming a blood clot at injured bones. During bone implantation, biomaterials unavoidably come into direct contact with blood, leading to a blood clot formation on its surface prior to bone regeneration. Despite both situations being similar in forming a blood clot at the defect site, most research in bone tissue engineering virtually ignores the important role of a blood clot in supporting healing. Dental implantology has long demonstrated that the fibrin structure and cellular content of a peri-implant clot can greatly affect osteoconduction and de novo bone formation on implant surfaces. This article reviews the formation of a blood clot during bone healing in relation to the use of platelet-rich plasma (PRP) gels. It is implicated that PRP gels are dramatically altered from a normal clot in healing, resulting in conflicting effect on bone regeneration. These results indicate that the effect of clots on bone regeneration depends on how the clots are formed. Factors that influence blood clot structure and properties in relation to bone healing are also highlighted. Such knowledge is essential for developing strategies to optimally control blood clot formation, which ultimately alter the healing microenvironment of bone. Of particular interest are modification of surface chemistry of biomaterials, which displays functional groups at varied composition for the purpose of tailoring blood coagulation activation, resultant clot fibrin architecture, rigidity, susceptibility to lysis, and growth factor release. This opens new scope of in situ blood clot modification as a promising approach in accelerating and controlling bone regeneration.

Autologous platelet rich plasma: topical versus intradermal after fractional ablative carbon dioxide laser treatment of atrophic acne scars

BACKGROUND

A proposal has recently been made regarding the potential adjuvant use of platelet-rich plasma (PRP) with fractional carbon dioxide laser (FCL) for the correction of acne scars.

OBJECTIVE

To compare the efficacy and safety of two administration modes of autologous PRP (intradermal injection (ID) and topical application) after FCL with that of FCL alone in the treatment of atrophic acne scars.

PATIENTS AND METHODS

Thirty patients were randomly divided into two groups. Both underwent split-face therapy. Group 1 was administered FCL followed by ID PRP on one side and FCL followed by ID saline on the other. In group 2, one cheek was treated with FCL followed by ID PRP, and the other received FCL followed by topical PRP. Each patient received 3 monthly sessions. The final assessment took place at 6 months.

RESULTS

Combined PRP- and FCL-treated areas had a significantly better response (p = .03), fewer side effects, and shorter downtime (p = .02) than FCL-treated areas, but there were no significant differences in ID- and topical PRP-treated areas in degree of response and downtime (p = .10); topically treated areas had significantly lower pain scores.

CONCLUSION

The current study introduces the combination of topical PRP and FCL as an effective, safe modality in the treatment of atrophic acne scars with shorter downtime than FCL alone and better tolerability than FCL combined with ID PRP.

Platelet-rich plasma: quantitative assessment of growth factor levels and comparative analysis of activated and inactivated groups

Background

Platelet-rich plasma (PRP) has more concentrated platelets than normal plasma (approximately 150-400×10³ cell/dL). Platelets excrete several growth factors and cytokines that are associated with the healing and regeneration process. However, even though PRP is widely used, the mechanism or actual effect is presently unclear. Therefore, this study was performed to investigate the levels of growth factors and platelet concentration rate.

Methods

Autologous blood for preparing PRP was obtained from healthy subjects aged 25 to 35 years. The samples were divided into 4 experimental groups (inactivated whole blood, inactivated PRP, activated whole blood with thrombin and calcium chloride, and activated PRP). The platelet counts in the blood were analyzed and the growth factors were quantitatively measured. A statistical analysis was performed by using Dunn's multiple comparison test.

Results

In the blood cell analysis, the platelet count of the PRP group was approximately 4.25 times higher than that of the whole blood group. In the quantitative analysis of growth factors, the platelet-derived growth factor (PDGF)-AB, PDGF-BB, and transforming growth factor-β of the inactivated and activated PRP groups were higher than those of the inactivated and activated whole blood groups (P<0.05).

Conclusions

In this study, the platelet count and the levels of PDGF-AB and PDGF-BB in the PRP were determined. Further, more research is required on the bioactivity level of the growth factors secreted during the process of PRP preparation and the potency of growth factors that can be exerted physiologically in vivo.

Effect of transforming growth factor Beta 1 on wound healing in induced diabetic rats

OBJECTIVE

Delayed wound healing is one of the complications of diabetes mellitus, exhibited by profound inflammation and decreased granulation tissues. The current study was carried out to evaluate wound healing in both normal and diabetic rats. In addition, it evaluated the potential protective effect of transforming growth factor β1 (TGF β1), that has the broadest spectrum of actions, affecting all cell types that are involved in all stages of wound healing to accelerate wound healing in normal & diabetic rats.

METHODS

: The present study was performed on 40 male albino rats. Each 10 rats were designed as a group. Group I saved as control. They received incisional wound in their tongues 1 cm length and 1/2 cm depth. Group II received 500 ng/kg of TGF β1 5 minutes before wounding. Group III diabetes was induced then rats were treated as second group. At the 14(th) day post wounding, sections of tongues were taken for hematoxylin and eosin and Masson's trichome staining to examine the histological changes. The intracellular actions of TGF β1 were studied by TEM.

RESULTS

A higher cell proliferation rate and a denser and more organized new extracellular matrix and complete wound closure was detected at the 14(th) days in the TGF β1 treated wound in comparison with the 14(th) days for the untreated, control groups. There were delayed wound healing in diabetic rats, decreased re-epithelialization, granulation tissue thickness, matrix density, number of infiltrated cells, and number of capillaries. In TGF β1 treated diabetic rats, showed significant healing improvement was obvious as compared with diabetic rats.

CONCLUSIONS

A single intravenous injection of TGF β1 was sufficient to enhance wound healing in rat's tongue. This approach represents a new strategy that may be applied to the treatment of incisional wounds in human diabetic patients.

Bone tissue engineering: recent advances and challenges

The worldwide incidence of bone disorders and conditions has trended steeply upward and is expected to double by 2020, especially in populations where aging is coupled with increased obesity and poor physical activity. Engineered bone tissue has been viewed as a potential alternative to the conventional use of bone grafts, due to their limitless supply and no disease transmission. However, bone tissue engineering practices have not proceeded to clinical practice due to several limitations or challenges. Bone tissue engineering aims to induce new functional bone regeneration via the synergistic combination of biomaterials, cells, and factor therapy. In this review, we discuss the fundamentals of bone tissue engineering, highlighting the current state of this field. Further, we review the recent advances of biomaterial and cell-based research, as well as approaches used to enhance bone regeneration. Specifically, we discuss widely investigated biomaterial scaffolds, micro- and nano-structural properties of these scaffolds, and the incorporation of biomimetic properties and/or growth factors. In addition, we examine various cellular approaches, including the use of mesenchymal stem cells (MSCs), embryonic stem cells (ESCs), adult stem cells, induced pluripotent stem cells (iPSCs), and platelet-rich plasma (PRP), and their clinical application strengths and limitations. We conclude by overviewing the challenges that face the bone tissue engineering field, such as the lack of sufficient vascularization at the defect site, and the research aimed at functional bone tissue engineering. These challenges will drive future research in the field.

Transplant of an autologous platelet gel prosthesis to fill defects after tumor excision

BACKGROUND

Tumor excision causes disfigurement in the breast. We present our technique for filling the defect with activated platelet gel, thus avoiding the deformity.

METHODS

Between 2006 and 2011, 23 patients (age range, 45-72 years) underwent tumorectomy for breast cancer. After estimating and extracting the volume of blood required, we centrifuged the blood at 1800 rpm for 8 minutes. Later, the middle and lower thirds of the plasma) were separated and activated with CaCl₂ at a ratio of 1/20, forming a gel, which was used to fill the tumorectomy cavity.

RESULTS

Imaging tests (ultrasound, mammography, and magnetic resonance imaging) performed 12 months after surgery revealed scar tissue in the area where the autoprosthesis had been inserted. Magnetic resonance imaging showed no retraction or deformity in the skin silhouette. Histology study after 1 year demonstrated that the platelet gel had been replaced by fibrous scar tissue with dense collagen and the presence of small capillary vessels. Patients recorded high rates of satisfaction.

CONCLUSIONS

This technique maintains the shape and volume of the breast, avoiding deformities and retractions of the nipple areola complex by filling the defect with an autoprosthesis. After 12 months, the autoprosthesis had been replaced by fibrous tissue and dense collagen. Postoperative control was good, and the effectiveness of adjuvant radiotherapy or chemotherapy was not altered. No cases of tumor relapse were recorded. On palpation, consistency and softness were similar to that of breast tissue. The aesthetic results were highly satisfactory.

Platelet-rich plasma peptides: key for regeneration

Platelet-derived Growth Factors (GFs) are biologically active peptides that enhance tissue repair mechanisms such as angiogenesis, extracellular matrix remodeling, and cellular effects as stem cells recruitment, chemotaxis, cell proliferation, and differentiation. Platelet-rich plasma (PRP) is used in a variety of clinical applications, based on the premise that higher GF content should promote better healing. Platelet derivatives represent a promising therapeutic modality, offering opportunities for treatment of wounds, ulcers, soft-tissue injuries, and various other applications in cell therapy. PRP can be combined with cell-based therapies such as adipose-derived stem cells, regenerative cell therapy, and transfer factors therapy. This paper describes the biological background of the platelet-derived substances and their potential use in regenerative medicine.

Delayed cutaneous wound healing in aged rats compared to younger ones

Delayed wound healing in elderly males is a complex process in which the factors responsible are not fully understood. This study investigated the hormonal, oxidative and angiogenic factors affecting wound healing in aged rats. Two groups consisting of eight healthy male Wistar Albino rats [young (30 ± 7 days) and aged (360 ± 30 days)], and a cutaneous incision wound healing model were used. Scar tissue samples from wounds on the 7th, 14th and 21st days of healing were evaluated for hydroxyproline and vascular endothelial growth factor content. Macrophage, lymphocyte, fibroblast and polymorphonuclear cell infiltration; collagen formation and vascularization were assessed by light and electron microscopy. The free oxygen radical content of the wounds was measured by a chemiluminescence method. Blood sample analysis showed that the hydroxyproline and total testosterone levels were significantly higher, and the oxygen radical content was significantly lower in young rats. Histopathological, immunohistochemical and ultrastructural evaluations revealed higher amounts of fibroblasts and collagen fibers, and more vascularization in young rats. These results are indicative of the delayed wound healing in aged rats. A combination of multiple factors including hormonal regulation, free oxygen radicals and impaired angiogenesis appears to be the cause of delayed cutaneous healing.

Immune responses to implants - a review of the implications for the design of immunomodulatory biomaterials

A key for long-term survival and function of biomaterials is that they do not elicit a detrimental immune response. As biomaterials can have profound impacts on the host immune response the concept emerged to design biomaterials that are able to trigger desired immunological outcomes and thus support the healing process. However, engineering such biomaterials requires an in-depth understanding of the host inflammatory and wound healing response to implanted materials. One focus of this review is to outline the up-to-date knowledge on immune responses to biomaterials. Understanding the complex interactions of host response and material implants reveals the need for and also the potential of "immunomodulating" biomaterials. Based on this knowledge, we discuss strategies of triggering appropriate immune responses by functional biomaterials and highlight recent approaches of biomaterials that mimic the physiological extracellular matrix and modify cellular immune responses.

Heparan sulfate glycosaminoglycan mimetic improves pressure ulcer healing in a rat model of cutaneous ischemia-reperfusion injury

Pressure ulcers are a major clinical problem, with a large burden on healthcare resources. This study evaluated the effects of the heparan sulfate glycosaminoglycan mimetic, OTR4120, on pressure ulceration and healing. Ischemia-reperfusion (I-R) was evoked to induce pressure ulcers by external clamping and then removal of a pair of magnet disks on rat dorsal skin for a single ischemic period of 16 hours. Immediately after magnet removal, rats received an intramuscular injection of OTR4120 weekly for up to 1 month. During the ischemic period, normal skin perfusion was reduced by at least 60% and at least 20-45% reperfused into the ischemic region after compression release. This model caused sustained skin incomplete necrosis for up to 14 days and led to grade 2-3 ulcers. OTR4120 treatment decreased the area of skin incomplete necrosis and degree of ulceration. OTR4120 treatment also reduced inflammation and increased angiogenesis. In OTR4120-treated ulcers, the contents of vascular endothelial growth factor, platelet-derived growth factor, and transforming growth factor beta-1 were increased. Moreover, OTR4120 treatment promoted early expression of alpha-smooth muscle actin and increased collagen biosynthesis. Long-term restoration of wounded tissue biomechanical strength was significantly enhanced after OTR4120 treatment. Taken together, we conclude that OTR4120 treatment reduces pressure ulcer formation and potentiates the internal healing bioavailability.

Novel use of platelet-rich plasma to augment curative diabetic foot surgery

Autologous platelet-rich plasma (PRP) may enhance wound healing through the formation of a platelet plug that provides both hemostasis and the secretion of biologically active proteins, including growth factors such as platelet-derived growth factor, transforming growth factor (TGF)-β, TGF-β2, and epidermal growth factor. The release of these growth factors into the wound may create an environment more conducive to tissue repair and could accelerate postoperative wound healing. To our knowledge, there are no reports of combining the use of PRP with curative diabetic foot surgery. This article provides a summary of the literature regarding PRP and wound healing and presents a case of a 49-year-old man with diabetes and a three-month history of a deep, nonhealing plantar hallux wound in which PRP was combined with a first metatarsophalangeal joint arthroplasty. Through the use of the PRP and bioengineered tissue to supplement curative diabetic foot surgery, the patient healed uneventfully at seven weeks.

Effect of sustained-release PDGF and TGF-beta on cyclophosphamide-induced impaired wound healing

BACKGROUND

Proper wound healing is pivotal to successful surgical outcomes. Previous studies have shown that growth factors can be used to enhance tissue repair under impaired healing conditions. However, because of limited delivery methods, the growth factors in these studies were delivered either topically or as a single local administration.

METHODS

Sixty Sprague-Dawley rats were divided equally into five groups and served as untreated normal controls or were implanted subcutaneously with a novel sustained-release drug delivery system through a dorsal incisional wound. This system delivered either transforming growth factor (TGF)-beta alone, platelet-derived growth factor (PDGF) alone, or TGF-beta and PDGF in combination, or served as unloaded sham controls. Wound healing was impaired in all treated rats by the administration of cyclophosphamide on days 1, 3, and 5. Wound tensile breaking strength was determined on days 4, 7, and 14.

RESULTS

Sustained release of either TGF-beta or PDGF alone not only failed to improve the healing of cyclophosphamide-induced impaired wound healing but resulted in a paradoxical decrease in wound tensile breaking strength by day 7. However, the combined delivery of both TGF-beta and PDGF improved wound healing and significantly increased wound tensile breaking strength by day 7.

CONCLUSIONS

Sustained-release delivery of TGF-beta and PDGF in combination, but not separately, by a subcutaneously implanted drug delivery system significantly improves cyclophosphamide-induced impaired wound healing in rats.

No positive effect of autologous platelet gel after total knee arthroplasty

BACKGROUND AND PURPOSE

Activated platelets release a cocktail of growth factors, some of which are thought to stimulate repair. We investigated whether the use of autologous platelet gel (PG) in total knee arthroplasty (TKA) would improve wound healing and knee function, and reduce blood loss and the use of analgesics.

PATIENTS AND METHODS

102 patients undergoing TKA were randomly assigned to a PG group (n = 50) or to a control (C) group (n = 52). The primary analysis was based on 73 participants (PG: 32; C: 41) with comparison of postoperative wound scores, VAS, WOMAC, knee function, use of analgesics, and the pre- and postoperative hemoglobin values after a follow-up of 3 months. 29 participants were excluded due to insufficient data.

RESULTS

The characteristics of the protocol-compliant patients were similar to those of the patients who were excluded. Analysis was per protocol and focused on the remaining 73 patients. At baseline and after 3 months of follow-up, there were no statistically significant differences between both groups regarding age, height, weight, sex, side of operation, platelet count, hemoglobin values, severity of complaints (WOMAC), and level of pain.

INTERPRETATION

In our patients undergoing TKA, application of PG to the wound site did not promote wound healing. Also, we found that PG had no effect on pain, knee function, or hemoglobin values.

Effects of platelet-rich plasma gel on skin healing in surgical wound in horses

PURPOSE: To establish a low-cost method to prepare platelet-rich plasma (PRP) and evaluates the potential of platelet derived factors to enhance wound healing in the surgical wounds in equine. METHODS: To obtain a PRP gel, calcium gluconate and autologous thrombin were added to platelet-rich plasma. For the tests six saddle horses were used and two surgical incisions were made in each animal. Wounds were treated with PRP gel or untreated. Sequential wound biopsies collected at Treatment 1: at days 5 and 30 and Treatment 2: at days 15 and 45 post wounding permitted comparison of differentiation markers and wound repair. RESULTS: The optimal platelets enrichment over 4.0 time's baseline values was obtained using 300 g for 10 min on the first centrifugation and 640 g for 10 min on the second centrifugation. CONCLUSION: Wounds treated with PRP gel exhibit more rapid epithelial differentiation and enhanced organization of dermal collagen compared to controls in equine

Epidermal growth factor released from platelet-rich plasma promotes endothelial cell proliferation in vitro

BACKGROUND AND OBJECTIVE

The therapeutic benefits of platelet-rich plasma (PRP) for the promotion of healing and regeneration of periodontal tissues are thought to result from enrichment in growth factors released from platelets. The aim of this study was to evaluate the effects of specific growth factors released from PRP on endothelial cell proliferation.

MATERIAL AND METHODS

The levels of vascular endothelial growth factor (VEGF), platelet-derived growth factor BB (PDGF-BB), basic fibroblast growth factor (bFGF) and epidermal growth factor (EGF) in supernatants of calcium- and thrombin-activated PRP samples from five donors were quantified by enzyme-linked immunosorbent assay. Supernatants were treated with neutralizing antibodies specific to each growth factor, and the effects of these treatments on human umbilical vein endothelial cell (HUVEC) proliferation in vitro were determined. The effect of removing EGF from PRP supernatants with antibody-coated beads on HUVEC proliferation was also tested.

RESULTS

Average concentrations of VEGF, PDGF-BB, bFGF and EGF in PRP supernatants were 189, 27,190, 39.5 and 513 pg/mL, respectively. The addition of EGF neutralizing antibodies to the PRP supernatants significantly reduced HUVEC proliferation (up to 40%), while such an inhibition was not observed following neutralization of the other growth factors. Removal of EGF from PRP supernatants by treatment with antibody-coated beads also resulted in a significant decrease in HUVEC proliferation. Recombinant EGF increased HUVEC proliferation in vitro in a dose-dependent manner.

CONCLUSION

This study showed that PRP supernatants are highly mitogenic for endothelial cells and provided evidence that this effect may be due, at least in part, to the presence of EGF. In vivo experiments are needed to confirm the roles of specific growth factors released from PRP in the healing of oral surgical and/or periodontal wounds.

Adipose stromal cells and platelet-rich plasma therapies synergistically increase revascularization during wound healing

BACKGROUND

The authors examined the efficacy of adipose stem cells, when supplied either alone or in platelet-rich fibrin gels, to improve wound healing.

METHODS

A porcine full-thickness wound model was used to compare six topical treatments: platelet-poor plasma; platelet-rich plasma; autologous adipose stem cells plus platelet-poor plasma; autologous adipose stem cells plus platelet-rich plasma; allogeneic adipose stem cells containing green fluorescent protein plus platelet-poor plasma; and saline (control). One week after isolation, adipose stem cells were applied to full-thickness wounds on the paraspinal and thoracic regions of three pigs (44 wounds per pig; each treatment was applied to eight separate wounds). Each wound was monitored over 21 days for closure, cosmesis, and histopathology.

RESULTS

There was no significant difference in the reepithelialization rate, but treatments containing adipose stem cells demonstrated increased microvessel densities (31.75 +/- 5.73 vessels/cm2 versus 7.93 +/- 3.61 vessels/cm2) compared with groups without adipose stem cells. Wound cosmesis was improved in the adipose stem cell plus platelet-rich plasma group compared with other treatment groups (p < 0.05). Vascular endothelial growth factor levels detected in matrices containing adipose stem cells were approximately 7-fold higher compared with platelet-rich plasma or platelet-poor plasma (p < 0.05). Localization of transgenic green fluorescent protein plus adipose stem cells indicated incorporation near neovasculature.

CONCLUSIONS

In normal healing wounds, adipose stem cells appear to enhance the healing process only when provided in a fibrin gel vehicle containing a number of complementary wound-healing trophic factors. Perivascular adipose stem cell localization suggests a function in enhancing blood supply through providing physical and paracrine support to newly forming vessels.

Proliferation-promoting effect of platelet-rich plasma on human adipose-derived stem cells and human dermal fibroblasts

BACKGROUND

This study evaluated changes in platelet-derived growth factor (PDGF)-AB and transforming growth factor (TGF)-beta1 release from platelets by platelet-rich plasma activation, and the proliferation potential of activated platelet-rich plasma and platelet-poor plasma on human adipose-derived stem cells and human dermal fibroblasts.

METHODS

Platelet-rich plasma was prepared using a double-spin method, with the number of platelets counted in each preparation stage. Platelet-rich and platelet-poor plasma were activated with autologous thrombin and calcium chloride, and levels of platelet-released PDGF-AB and TGF-beta1 were determined by enzyme-linked immunosorbent assay. Cells were cultured for 1, 4, or 7 days in serum-free Dulbecco's Modified Eagle Medium supplemented with 5% whole blood plasma, nonactivated platelet-rich plasma, nonactivated platelet-poor plasma, activated platelet-rich plasma, or activated platelet-poor plasma. In parallel, these cells were cultured for 1, 4, or 7 days in serum-free Dulbecco's Modified Eagle Medium supplemented with 1%, 5%, 10%, or 20% activated platelet-rich plasma. The cultured human adipose-derived stem cells and human dermal fibroblasts were assayed for proliferation.

RESULTS

Platelet-rich plasma contained approximately 7.9 times as many platelets as whole blood, and its activation was associated with the release of large amounts of PDGF-AB and TGF-beta1. Adding activated platelet-rich or platelet-poor plasma significantly promoted the proliferation of human adipose-derived stem cells and human dermal fibroblasts. Adding 5% activated platelet-rich plasma to the medium maximally promoted cell proliferation, but activated platelet-rich plasma at 20% did not promote it.

CONCLUSIONS

Platelet-rich plasma can enhance the proliferation of human adipose-derived stem cells and human dermal fibroblasts. These results support clinical platelet-rich plasma application for cell-based, soft-tissue engineering and wound healing.

Evidence-based wound management: a systematic review of therapeutic agents to enhance granulation and epithelialization

Successful management of open wounds in dogs requires knowledge of the physiology of wound healing and application of that knowledge to choose appropriate therapeutic intervention. The authors' objective was to investigate whether or not there are any available therapeutic agents that enhance granulation or epithelialization of open wounds in dogs. Based on the literature identified in the authors' review, there is insufficient evidence to make a recommendation for or against any of the topical wound agents or procedures studied.

Wound-healing properties of trehalose-stabilized freeze-dried outdated platelets

BACKGROUND

The wound-healing applications of platelet (PLT)-derived cytokines, proteins, and membranes is accepted but continues to be investigated. In this study, it is demonstrated that stabilized freeze-dried PLTs prepared from outdated PLTs (FDPOs) accelerate wound healing and form tube structures as well as stabilized indated freeze-dried PLTs (FDPIs) and room-temperature fresh PLTs (RT-PLTs).

STUDY DESIGN AND METHODS

Experiments were designed to compare in vitro and in vivo wound-healing properties of FDPI, FDPO, and RT-PLT preparations. The concentration of PLT-derived growth factor (PDGF)-betabeta and transforming growth factor (TGF)-beta1 was determined, and the abilities of FDPIs, FDPOs and RT-PLTs to induce endothelial cell proliferation and promote endothelial cell tube formation (cells formed solid spouts connecting neighboring cells to form tube structures) were observed. Wound-healing characteristics were measured by surgically inducing 1-cm(2), full-thickness wounds on db/db mice (n = 10 per group). The wounds were treated with single or multiple doses of FDPIs and FDPOs. Wound closure rate was determined, and histology samples were evaluated for cellular makeup.

RESULTS

FDPOs retained the same levels of PDGF-betabeta and TGF-beta1 and were able to promote endothelial cell proliferation and tube formation in vitro as well as FDPIs or RT-PLTs. Multiple applications of FDPO accelerated wound closure and enhanced reepithelialization when compared to untreated wounds in db/db mice.

CONCLUSION

FDPOs enhanced wound healing in db/db mice as well as FDPIs and RT-PLTs. Wound closure was obtained 6 days earlier than untreated wounds and histologic examination revealed reduced granulation and increased cellular angiogenesis.

Pathophysiology of acute wound healing

Wound healing is a complex process that can be divided into at least 3 continuous and overlapping processes: an inflammatory reaction, a proliferative process leading to tissue restoration, and, eventually, tissue remodeling. Wound healing processes are strictly regulated by multiple growth factors and cytokines released at the wound site. Although the desirable final result of coordinated healing would be the formation of tissue with a similar structure and comparable functions as with intact skin, regeneration is uncommon (with notable exceptions such as early fetal healing); healing however results in a structurally and functionally satisfactory but not identical outcome. Alterations that disrupt controlled healing processes would extend tissue damage and repair. The pathobiologic states may lead to chronic or nonhealing wounds or excessive fibrosis.

Initial wound management

A wounded patient can be presented to the veterinary surgeon under a number of circumstances. The wound could result from external trauma,such as vehicle trauma or an animal fight, or it could have been created by surgical intervention, such as the removal of a mass. A wound could also be secondary to a failed initial attempt at wound closure. No matter what the cause, initial wound management often follows similar pathways. A successful wound closure and healing outcome is often dependent on adherence to basic principles of wound assessment, appropriate care, and reassessment. This article covers the approach to and specific options for the initial stages of wound management.

Nucleotide structure of equine platelet-derived growth factor-A and -B and expression in horses with induced acute tendinitis

OBJECTIVE

To characterize the nucleotide sequence of equine platelet-derived growth factor (PDGF)-A and -B and analyze temporal expression of these genes in equine tendon after induced tendinitis injury. Animals-18 mature horses.

PROCEDURES

Genes for equine PDGF-A and -B were reverse transcribed and sequenced from synovial tissue mRNA obtained from a 3-year-old horse. Collagenase-induced lesions were created in the tensile region of the superficial digital flexor tendon in 14 horses; 3 horses served as uninjured control animals. Tendons were harvested and total RNA was isolated from experimental horses 1, 2, 4, 8, and 24 weeks after collagenase injection. Temporal gene expression for PDGF-A and -B was determined by use of quantitative PCR analysis.

RESULTS

Equine PDGF-A shared 83.8% sequence and 87.5% peptide homology with human PDGF-A, with a discrepancy of 70 bp from the human sequence. Equine PDGF-B was similar in length to the human gene, sharing 90.3% and 91.7% nucleotide and peptide identity, respectively. Expression of PDGF-A mRNA in collagenase-induced tendinitis lesions was unchanged, compared with expression for normal control tendon, and remained steady throughout the 24-week study. Expression of PDGF-B mRNA decreased over time, and the expression at 24 weeks was significantly reduced, compared with expression in normal and acutely injured tendon.

CONCLUSIONS AND CLINICAL RELEVANCE

Injured tendon mounts a minimal constitutive PDGF-A or -B mRNA response. Serial exogenous treatment with either PDGF isoform within the first 2 to 4 weeks after tendon injury may bolster the meager PDGF paracrine-autocrine intrinsic response to injury.

The efficacy of autologous platelet gel in pain control and blood loss in total knee arthroplasty. An analysis of the haemoglobin, narcotic requirement and range of motion

Biological materials used to assist in haemostasis following total knee arthroplasty have been the subject of much recent research. Autologous platelet gel is a substance that is derived from platelet-rich plasma extracted from the patient's blood and centrifuged perioperatively, and is applied to exposed tissues, synovium and the lining of the wound at closure. Concentrating and applying these factors directly to the wound at the end of a total knee arthroplasty procedure may lead to more complete haemostasis, a reduction in perioperative blood loss, accelerated tissue repair and decreased postoperative pain. In this study, 98 unilateral total knee arthroplasties were evaluated retrospectively, 61 of which involved the intaroperative use of platelet gel, and 37 of which served as control subjects. Outcomes analysed were postoperative haemoglobin changes, intravenous and oral narcotic requirements, range of motion on discharge and total days in hospital. Patients receiving platelet gel during surgery had less postoperative blood loss as measured by differences in the preoperative and postoperative haemoglobin on day 3 (2.7 vs. 3.2 g/dl; P=0.026). The narcotic requirement was less in the platelet gel group for both intravenous (17.0 vs. 36.3 mg/day; P=0.024) and oral (1.84 vs. 2.75 tabs/day; P=0.063) medication. This group also achieved a higher range of motion prior to discharge (78.2 vs. 71.9; P=0.052) and were discharged an average of 1 day earlier than their control counterparts. Though further prospective trials are necessary, this study indicates that the application of autologous platelet gel may lead to improved haemostasis, better pain control and a shortened hospital stay.

Modulation of Wound Response and Soft Tissue Ingrowth in Synthetic and Allogeneic Implants With Platelet Concentrate

OBJECTIVE

To evaluate the modulation of wound healing and soft tissue ingrowth in synthetic and allogeneic implants with platelet gel. Attempts to influence wound healing with exogenous growth factors are highly dependent on the timing and dosing of treatment. Platelet gel made from autologous platelet concentrate (PC) and activated with calcium thrombin is increasingly used to enhance healing of surgical and chronic wounds, based on the assumption that proteins found in the blood can promote healing.

METHODS

Adult New Zealand white rabbits underwent phlebotomy, and the blood was used to produce nonconcentrated autologous blood clot, platelet-poor plasma (PPP), and PC for each animal. Disks of porous high-density polyethylene (PHDPE) and acellular dermal graft (ADG) were implanted into each animal in a subcutaneous location. Implants of each type were treated with isotonic sodium chloride solution, PPP, PPP followed immediately with PC, or autologous blood clot (by means of manual impregnation). Animals were killed at 2, 7, 14, and 21 days after implantation. Implants were harvested with surrounding soft tissue and examined by means of light microscopy for evidence of acute and chronic inflammatory cells and vascular and fibroblast invasion.

RESULTS

A platelet gel with platelet concentrations averaging 5.8 times greater than those of peripheral blood significantly improved wound healing and soft tissue ingrowth in surgically implanted grafts. Early inflammatory infiltrates were enhanced in PHDPE and ADG implants by PC and autologous blood clot compared with control implants, as evidenced by significantly increased neutrophil and macrophage counts at day 2. Compared with controls, statistically significant increases in fibroblast and endothelial cell counts were noted at day 7 in PC-treated implants (fibroblasts, 61% increase [P < .001] in PHDPE implants and 52% increase [P < .001] in ADG implants; capillaries, 95% increase [P < .05] in PHDPE and 97% increase [P < .001] in ADG implants). Lymphocyte counts were increased by PC in PHDPE and ADG implants (71% [P < .001] and 100% [P < .05], respectively). There were no statistically significant differences in any cell count variables beyond 7 days.

CONCLUSIONS

Treatment with PC prepared at 5 times the baseline platelet count significantly accelerated maturation of experimental wounds. By 14 days, the degree and quality of wound cellularity were equivalent among all treatment groups. Rapid wound healing was expected with this surgical model, which was chosen to observe the biological effects on early wound healing of a platelet gel in a noncompromised wound. Treatment with PC may be useful in scenarios in which enhancement and acceleration of early wound healing is desired.

Platelets in inflammatory bowel disease: clinical, pathogenic, and therapeutic implications

Both Crohn's disease (CD) and ulcerative colitis (UC) are associated with abnormalities of platelet number and function. In the peripheral circulation the state of platelet activation is typically increased, and inflammatory bowel disease (IBD)-involved mucosa frequently contains platelet aggregates within mucosal microthrombi. The relevance of platelet dysfunction to IBD pathogenesis is still unclear, but there is solid evidence demonstrating that platelets, in addition to their traditional role in hemostasis, can also function as potent proinflammatory cells. Upon activation, platelets secrete a large number of biologically active molecules able to induce or amplify an inflammatory process through many of the same cellular and molecular pathways conventionally utilized by immune cells mediating IBD. The aim of this article is to review data on the existence of platelet dysfunction in IBD, substantiate platelets' inflammatory potential, discuss the implications of abnormal platelet activity for chronic intestinal inflammation, and consider the potential benefits of platelet modulation for treatment of IBD.

Platelet-rich plasma gel promotes differentiation and regeneration during equine wound healing

Nonhealing wounds of the lower equine limb represent a challenging model. The platelet is a natural source of a myriad of growth factors and cytokines that promote wound healing. This study evaluates the potential of platelet derived factors to enhance wound healing in the lower equine limb. Platelets were isolated from horse blood and activated with thrombin, a process known to induce growth factor release. This produced a platelet gel composed of platelet-rich plasma (PRP). To test this all-natural wound healant, 2.5-cm(2) full thickness cutaneous wounds were created below the knee and hock of a thoroughbred horse. Wounds were treated with PRP gel or left untreated. Sequential wound biopsies collected at Days 7, 36, and 79 postwounding permitted comparison of the temporal expression of differentiation markers and wound repair. To test the hypothesis that wounds treated with PRP gel exhibit more rapid epithelial differentiation and enhanced organization of dermal collagen compared to controls, tissues were stained for cytokeratin 10, a suprabasal differentiation marker, and the reestablishment of collagen was evaluated by trichrome staining. PRP gel-treated wounds at Day 7 expressed intense cytokeratin 10 staining near the wound junction in suprabasal epidermal layers, while staining in control tissues was less intense and restricted to apical epidermal layers distal to the wound junction. By Day 79, the staining was equal in both groups. However, PRP gel-treated wounds at Day 79 contained abundant, dense collagen bundles oriented parallel to each other and to the overlying epithelium, whereas control tissues contained fewer collagen fibers that were oriented randomly. Thus, treatment of wounds with PRP gel induced accelerated epithelial differentiation and produced tissue with organized, interlocking collagen bundles. This study reveals that this novel all-natural wound healant induced wound repair in injuries previously deemed untreatable.

Results of vitrectomy and the no-touch-technique using autologous adjuvants in macular hole treatment

BACKGROUND

Anatomic and functional results of macular holes using vitrectomy and platelet-concentrate (PC) or autologous whole blood (WB) were investigated without peeling any epiretinal membrane in order to minimize retinal trauma.

METHODS

44 patients with macular holes stage II, III and IV underwent a vitrectomy with removal of posterior cortical vitreous (in stage II and III) and C2F6 gas endotamponade. No peeling of any epiretinal membrane or the ILM was performed. In 14 patients autologous WB was injected and in 30 patients autologous PC. The mean follow-up time was 9.3 months.

RESULTS

An anatomic closure was observed in 36.4% of patients in the WB-group and in 93.9% of patients in the PC-group. SLO-microperimetry showed a reduction of absolute scotomas in 80% of the WB- and in 75% of the PC-group. In the WB-group 1 retinal detachment and 1 branch vein occlusion occurred; in the PC-group 3 retinal detachments, 1 central artery occlusion, 1 macular pucker, 1 cystoid macular edema, 1 late reopening and 1 secondary glaucoma were observed. In both groups no endophthalmitis occurred.

CONCLUSION

If autologous platelet concentrate is available, high anatomic success rates can be achieved without aggressive membrane removal, which may cause retinal damage. Autologous whole blood cannot be recommended as an alternative adjunct for the treatment of macular holes without membrane removal.

A novel controlled drug-delivery system for growth hormone applied to healing skin wounds in diabetic rats

Controlled release systems for drugs, hormones and growth factors can be particularly useful in tissue repair processes. These systems act as a biodegradable support containing the substance to be delivered, allowing their gradual release. In the past years, the local application of growth factors has acquired special relevance as a therapeutic option for use in subjects who show deficient tissue scarring, the hormone dose being the limiting factor for its success. In this study, the in vitro biocompatibility of a copolymer formed by vinylpyrrolidone and 2-hydroxyethyl methacrylate, used as an administration vehicle for hGH, was evaluated. The system was then tested in vivo in terms of its capacity for healing incisional wounds in healthy and diabetic rats. For the in vitro studies, polymer and hormone degradation rates were determined, and polymer biocompatibility was evaluated in fibroblast cultures. In the in vivo experiments, an incision was made in the back of the animals, and polymers discs with/without hGH, were introduced in the aperture. Morphological, immunohistochemical and morphometric evaluations were performed on wound tissue specimens 3-10 days after surgery. In vitro, the polymer was found to be biodegradable and showed no toxic effects on fibroblasts, the hormone being slowly released to the culture medium. In untreated diabetic rats, a delayed skin scarring and cell response were observed, compared to that noted in healthy animals. Skin closure, keratinisation and fibrosis occurred earlier in the presence of the polymer-hGH system. The use of this co-polymer as an administration vehicle for hGH improves the wound scarring process in the pathological setting of diabetes.

TGF-beta-mediated control of allergen-specific T-cell responses

Control of allergen-specific response by suppressive cytokines involves several layers of regulation, including secretion of the cytokine, deviation of cytokine expression by altered T-cell differentiation, immediate (de-) phosphorylation events upon binding of suppressive cytokines, and laterations in susceptibility of suppression.

Evaluation of small-intestinal submucosa implants for repair of meniscal defects in dogs

OBJECTIVE

To assess the effects of porcine small intestinal submucosa (SIS) implants on the healing of meniscal lesions in dogs.

ANIMALS

16 adult Greyhounds of both sexes.

PROCEDURE

Unilateral osteotomy was performed at time 0 to disrupt the medial collateral ligament attachment, and two (1 cranial and 1 caudal) 4-mm circular defects were created in the avascular portion of the medial meniscus. One defect was filled with an SIS graft, and the other defect remained empty (control). Three months later, the identical procedure was performed on the contralateral limb. Three months after the second surgery, dogs were euthanatized, and meniscal tissue specimens from both stifle joints were collected for gross, histologic, biomechanical, and biochemical evaluations.

RESULTS

Regenerative tissue was evident in 4 (2 SIS-implanted and 2 control) of 16 defects examined histologically. In 3 defects, this thin bridge of tissue was composed of immature haphazardly arranged fibrous connective tissue with a relatively uniform distribution of fibroblasts. Aggregate modulus, Poisson ratio, permeability, and shear modulus were not significantly different between control and SIS-implanted defects either 3 or 6 months after surgery. Hydroxyproline content also did not differ between SIS-implanted and control defects at 3 or 6 months.

CONCLUSIONS AND CLINICAL RELEVANCE

Implantation of porcine SIS into experimentally induced meniscal lesions in dogs did not promote tissue regeneration.