Human plasma fibronectin potentiates the mitogenic activity of platelet-derived growth factor and complements its wound healing effects

A review of platelet-rich plasma for enteric fistula management

Enteric fistula (EF), a serious complication after abdominal surgery, refers to unnatural communication between the gastrointestinal tract and the skin or other hollow organs. It is associated with infection, massive fluid/electrolyte loss, and malnutrition, resulting in an unhealed course. Despite advances in surgical techniques, wound care, infection control, and nutritional support, EF remains associated with considerable morbidity and mortality. Autologous platelet-rich plasma (PRP) containing elevated platelet concentrations has been proposed to promote healing in many tissues. However, the mechanism of action of PRP in EF treatment remains unclear owing to its complicated clinical manifestations. In this review, we summarized the clinical approaches, outlined the principal cytokines involved in the healing effects, and discussed the advantages of PRP for EF therapy. In addition, we defined the mechanism of autologous PRP in EF management, which is essential for further developing EF therapies.

An Extracellular Matrix-Liposome Composite, a Novel Extracellular Matrix Delivery System for Accelerated Tissue Regeneration

The unfolded states of fibronectin (FN) subsequently induce the formation of an extracellular matrix (ECM) fibrillar network, which is necessary to generate new substitutive tissues. Here, the authors demonstrate that negatively charged small unilamellar vesicles (SUVs) qualify as candidates for FN delivery due to their remarkable effects on the autonomous binding and unfolding of FN, which leads to increased tissue regeneration. In vitro experiments revealed that the FN-SUV complex remarkably increased the attachment, differentiation, and migration of fibroblasts. The potential utilization of this complex in vivo to treat inflammatory colon diseases is also described based on results obtained for ameliorated conditions in rats with ulcerative colitis (UC) that had been treated with the FN-SUV complex. Their findings provide a new ECM-delivery platform for ECM-based therapeutic applications and suggest that properly designed SUVs may be an unprecedented FN-delivery system that is highly effective in treating UC and inflammatory bowel diseases.

Platelet-Released Growth Factors Induce Genes Involved in Extracellular Matrix Formation in Human Fibroblasts

Platelet concentrate products are increasingly used in many medical disciplines due to their regenerative properties. As they contain a variety of chemokines, cytokines, and growth factors, they are used to support the healing of chronic or complicated wounds. To date, underlying cellular mechanisms have been insufficiently investigated. Therefore, we analyzed the influence of Platelet-Released Growth Factors (PRGF) on human dermal fibroblasts. Whole transcriptome sequencing and gene ontology (GO) enrichment analysis of PRGF-treated fibroblasts revealed an induction of several genes involved in the formation of the extracellular matrix (ECM). Real-time PCR analyses of PRGF-treated fibroblasts and skin explants confirmed the induction of ECM-related genes, in particular transforming growth factor beta-induced protein (TGFBI), fibronectin 1 (FN1), matrix metalloproteinase-9 (MMP-9), transglutaminase 2 (TGM2), fermitin family member 1 (FERMT1), collagen type I alpha 1 (COL1A1), a disintegrin and metalloproteinase 19 (ADAM19), serpin family E member 1 (SERPINE1) and lysyl oxidase-like 3 (LOXL3). The induction of these genes was time-dependent and in part influenced by the epidermal growth factor receptor (EGFR). Moreover, PRGF induced migration and proliferation of the fibroblasts. Taken together, the observed effects of PRGF on human fibroblasts may contribute to the underlying mechanisms that support the beneficial wound-healing effects of thrombocyte concentrate products.

Platlet-Rich Plasma - Review of Literature

Wound healing is a dynamic and physiological process for restoring the normal architecture and functionality of damaged tissue. Platelet-rich plasma (PRP) is an autologous whole blood product that contains a large number of platelets in a small volume of plasma with complete set of coagulation factors, which are in physiological concentrations. PRP has haemostatic, adhesive properties and acts supraphysiologically in the process of wound healing and osteogenesis. Platelets play a very important role in the wound healing process by providing growth factors that enhance the rate and quality of wound healing by many different mechanisms. The aim of this review is to describe: the biology of platelets and their role in the wound healing process, the terminology of platelet rich products, PRP preparation, activation and concentration of PRP, as well as the use of PRP in plastic surgery.

Fibronectin in development and wound healing

Fibronectin structure and composition regulate contextual cell signaling. Recent advances have been made in understanding fibronectin and its role in tissue organization and repair. This review outlines fibronectin splice variants and their functions, evaluates potential therapeutic strategies targeting or utilizing fibronectin, and concludes by discussing potential future directions to modulate fibronectin function in development and wound healing.

Platelet-Released Growth Factors and Platelet-Rich Fibrin Induce Expression of Factors Involved in Extracellular Matrix Organization in Human Keratinocytes

Platelet-released growth factor (PRGF) is a thrombocyte concentrate lysate which, like its clinically equivalent variations (e.g., Vivostat PRF^® (platelet-rich fibrin)), is known to support the healing of chronic and hard-to-heal wounds. However, studies on the effect of PRGF on keratinocytes remain scarce. This study aims to identify genes in keratinocytes that are significantly influenced by PRGF. Therefore, we performed a whole transcriptome and gene ontology (GO) enrichment analysis of PRGF-stimulated human primary keratinocytes. This revealed an increased expression of genes involved in extracellular matrix (ECM) organization. Real-time polymerase chain reaction (PCR) and enzyme-linked immunosorbent assay (ELISA) analysis confirmed the PRGF-mediated induction of selected ECM-related factors such as transforming growth factor beta-induced protein, fibronectin 1, matrix metalloproteinase-9, transglutaminase 2, fermitin family member 1, collagen type I alpha 1 and collagen type XXII alpha 1. PRGF-induced expression of the above factors was influenced by blockade of the epidermal growth factor receptor (EGFR), a receptor playing a crucial role in wound healing. A differential induction of the investigated factors was also detected in skin explants exposed to PRGF and in experimentally generated in vivo wounds treated with Vivostat PRF^®. Together, our study indicates that the induction of ECM-related factors may contribute to the beneficial wound-healing effects of PRGF-based formulations.

Effectiveness of autologous platelet-rich plasma gel in the treatment of hard-to-heal leg ulcers: a randomised control trial

OBJECTIVE

Regenerative medicine products such as autologous platelet-rich plasma (autologous PRP) gel may speed up the process of healing. Clinical studies show promising results in the treatment of diabetic foot ulcers (DFUs), however there is lack of scientific evidence of autologous PRP effectiveness in treating leg ulcers of other aetiology. This study evaluates the effectiveness of autologous PRP gel in the treatment of hard-to-heal leg ulcers compared with existing conventional treatment.

METHOD

A prospective, randomised controlled, open-labelled clinical trial was carried out between 2014 and 2018. An eight-week study protocol was chosen or until 100% wound re-epithelialisation was observed. Wound size reduction, granulation tissue formation, microbiological wound bed changes and safety were evaluated.

RESULTS

A total of 69 patients (35 in the autologous PRP group and 34 in the control group) were included in the study; 25.71% of the autologous PRP group and 17.64% of control group had ulcers completely re-epithelialised (p>0.05). Wound size reduction in the autologous PRP group was 52.35% and 33.36% in the control group (p=0.003). The autologous PRP group showed superiority over conventional treatment in wound bed coverage with granulation (p=0.001). However, more frequent wound contamination was observed at the end of treatment in the autologous PRP group (p=0.024). No severe adverse events were noted during the study. Both treatment methods were considered equally safe.

CONCLUSION

Topical application of autologous PRP gel in leg ulcers of various aetiology show beneficial results in wound size reduction and induces the granulation tissue formation. However, it is associated with more frequent microbiological wound contamination.

Biological responses of dental pulp cells to surfaces modified by collagen 1 and fibronectin

Collagen 1 (COL1) and fibronectin (FN) are extracellular matrix proteins that contribute in cell activity and involve in regulating dental pulp cells (DPCs). The purpose of this study was to investigate the effect of COL1 and FN on the behavior of DPCs. Here, DPCs were grown under three different conditions: COL1 coating, FN coating, and control group without coating. The proliferation and differentiation of DPCs were investigated. DPCs in osteogenic media were able to differentiate into osteoblastic phenotype. The morphological analysis revealed no obvious difference on the shape of cells. Cells had spread well on both coated and noncoated culture plates with slightly more spreading in the coated plates after 24 hr. The MTT analysis did not demonstrate a significant difference at 1 and 3 hr among the groups, but interestingly, the analysis disclosed more cells on the coated plates after longer cultures, which indicated a higher proliferative capacity in response to COL1 and FN. RT-PCR, Western Blotting and mineralization assays did not reveal significant differences between the coated and noncoated surfaces in relation to osteogenic differential potential. Our data suggested that the surface coating of COL1 and FN were able to promote cellular proliferation and the osteogenic differentiation tendency of DPCs was also observed in vitro.

New method in treatment of post-operative air leakage with fresh frozen plasma

BACKGROUND

No consensus regarding the best post-operative treatment option for air leak has been established. In this study, we evaluate the use of intra-pleural fresh frozen plasma (FFP) as a promising treatment method.

METHODS

Treatment for a sustained air leak (3 days) was warranted in approximately 12% of the lung surgeries at our institution. Fifty-two patients were treated with FFP by application of 250 mL daily. The patients were divided into two cohorts: cohort 1 consisted of 35 patients undergoing anatomical lung resections and cohort 2 consisted of 17 patients after miscellaneous types of lung surgery. Successfulness of the procedure as well as the potential influential factors was evaluated statistically and validated by a bootstrapping. Area under receiver operating characteristic curve was used to establish a cut-off value of the predictor.

RESULTS

In the first cohort, air leakage was successfully treated in 28 (80%), while in seven (20%) it was still present after third treatment with FFP. The success rate in cohort 2 was 76.5%. The only covariate which appeared to remain significant in both cohorts was flow as displayed on the digital suction device prior to application of FFP. Flow ≤375 mL/min was indicative of successful aerostasis.

CONCLUSION

Intra-pleural instillation of FFP seems to be a feasible method for the treatment of post-operative air leakage. Although the optimum strategy regarding its application as well as its limitations is yet to be established, an absence of complications or undesirable events makes this (off label) method a safe and promising alternative to existing options.

Fibronectin in cell adhesion and migration via N-glycosylation

Directed cell migration is an important step in effective wound healing and requires the dynamic control of the formation of cell-extracellular matrix interactions. Plasma fibronectin is an extracellular matrix glycoprotein present in blood plasma that plays crucial roles in modulating cellular adhesion and migration and thereby helping to mediate all steps of wound healing. In order to seek safe sources of plasma fibronectin for its practical use in wound dressing, we isolated fibronectin from human (homo) and porcine plasma and demonstrated that both have a similar ability as a suitable substrate for the stimulation of cell adhesion and for directing cell migration. In addition, we also defined the N-glycosylation sites and N-glycans present on homo and porcine plasma fibronectin. These N-glycosylation modifications of the plasma fibronectin synergistically support the integrin-mediated signals to bring about mediating cellular adhesion and directed cell migration. This study not only determines the important function of N-glycans in both homo and porcine plasma fibronectin-mediated cell adhesion and directed cell migration, but also reveals the potential applications of porcine plasma fibronectin if it was applied as a material for clinical wound healing and tissue repair.

Fibronectin in tissue regeneration: timely disassembly of the scaffold is necessary to complete the build

Tissue injury initiates extracellular matrix molecule expression, including fibronectin production by local cells and fibronectin leakage from plasma. To benefit tissue regeneration, fibronectin promotes opsonization of tissue debris, migration, proliferation, and contraction of cells involved in the healing process, as well as angiogenesis. When regeneration proceeds, the fibronectin matrix is fully degraded. However, in a diseased environment, fibronectin clearance is often disturbed, allowing structural variants to persist and contribute to disease progression and failure of regeneration. Here, we discuss first how fibronectin helps tissue regeneration, with a focus on normal cutaneous wound healing as an example of complete tissue recovery. Then, we continue to argue that, although the fibronectin matrix generated following cartilage and central nervous system white matter (myelin) injury initially benefits regeneration, fibronectin clearance is incomplete in chronic wounds (skin), osteoarthritis (cartilage), and multiple sclerosis (myelin). Fibronectin fragments or aggregates persist, which impair tissue regeneration. The similarities in fibronectin-mediated mechanisms of frustrated regeneration indicate that complete fibronectin clearance is a prerequisite for recovery in any tissue. Also, they provide common targets for developing therapeutic strategies in regenerative medicine.

Role of fibronectin in normal wound healing

Fibronectin is an adhesive molecule that plays a crucial role in wound healing, particularly in extracellular matrix (ECM) formation and also in reepithelialisation. Fibronectin plays many different roles in the wound healing process because of the presence of specific function domains and binding sites in its structure. Fibronectin interacts with different cell types, cytokines and the ECM. The main role of fibronectin is ECM formation. First, plasma fibronectin forms a provisional fibrin-fibronectin matrix, which will later be replaced by the mature ECM-containing tissue fibronectin.

Cellular events and biomarkers of wound healing

Researchers have identified several of the cellular events associated with wound healing. Platelets, neutrophils, macrophages, and fibroblasts primarily contribute to the process. They release cytokines including interleukins (ILs) and TNF-α, and growth factors, of which platelet-derived growth factor (PDGF) is perhaps the most important. The cytokines and growth factors manipulate the inflammatory phase of healing. Cytokines are chemotactic for white cells and fibroblasts, while the growth factors initiate fibroblast and keratinocyte proliferation. Inflammation is followed by the proliferation of fibroblasts, which lay down the extracellular matrix. Simultaneously, various white cells and other connective tissue cells release both the matrix metalloproteinases (MMPs) and the tissue inhibitors of these metalloproteinases (TIMPs). MMPs remove damaged structural proteins such as collagen, while the fibroblasts lay down fresh extracellular matrix proteins. Fluid collected from acute, healing wounds contains growth factors, and stimulates fibroblast proliferation, but fluid collected from chronic, nonhealing wounds does not. Fibroblasts from chronic wounds do not respond to chronic wound fluid, probably because the fibroblasts of these wounds have lost the receptors that respond to cytokines and growth factors. Nonhealing wounds contain high levels of IL1, IL6, and MMPs, and an abnormally high MMP/TIMP ratio. Clinical examination of wounds inconsistently predicts which wounds will heal when procedures like secondary closure are planned. Surgeons therefore hope that these chemicals can be used as biomarkers of wounds which have impaired ability to heal. There is also evidence that the application of growth factors like PDGF will help the healing of chronic, nonhealing wounds.

BLOOD-DERIVED, TISSUE ENGINEERING BIOMATERIALS

Fibrin sealant and platelet gels are human blood-derived, biodegradable, non toxic, surgical products obtained by mixing a fibrinogen concentrate or a platelet rich plasma with thrombin, respectively. Fibrin sealant is now a well known surgical tool increasingly used to stop or control bleeding, or to provide air and fluid tightness in many surgical situations. Platelet gels are newly developed preparations that are of specific interest because they contain numerous physiological growth factors and cytikines that are released upon the activation of blood platelets by thrombin. These growth factors, including PDGF, TGF-β 1, BMP, and VEGF have been shown to stimulate cell growth and differentiation with special clinical benefits for soft and bony tissue healing and regeneration. Platelet gels allow surgeons to manipulate the cellular environment of surgical sites and to guide tissue regeneration. A specific interest of such products is observed for the induction of osteogenesis and chondrogenesis. Advances in the preparation, clinical use, and safety of these two important classes of blood-derived biomaterials are reviewed.

Direct chemical cross-linking of platelet-derived growth factor-BB to the demineralized bone matrix improves cellularization and vascularization

In previous studies, we have described the use of demineralized bone matrix (DBM) as a carrier for the localized delivery system of growth factors in vitro and in vivo. The aim of the present work was to develop a direct chemical approach to immobilize the platelet-derived growth factor-BB (PDGF-BB) on DBM with cross-linking reagents. The amount of PDGF-BB covalently immobilized on DBM was significantly increased. The increased proliferation of fibroblasts demonstrated that the biological activity of PDGF-BB was not significantly reduced by cross-linking. Compared with control groups, there was a statistically significant increase in blood vessel density in the PDGF-C-DBM group after having been subcutaneously implanted into the dorsal side of the rats. The surface bioactivity of scaffolds on stimulation cell and new blood vessel invasion was improved. Therefore, the direct chemical cross-linking approach could be used to retain growth factors on collagen scaffolds effectively to develop functional biomaterials.

Estimating the pathogen safety of manufactured human plasma products: application to fibrin sealants and to thrombin

BACKGROUND

Plasma fractionators have implemented many improvements over the past decade directed toward reducing the likelihood of pathogen transmission by purified blood products, yet little has been published attempting to assess the overall impact of these improvements on the probability of safety of the final product.

STUDY DESIGN AND METHODS

Safety margins for human immunodeficiency virus (HIV), hepatitis C virus (HCV), hepatitis B virus (HBV), hepatitis A virus (HAV), parvovirus B19, and variant form of Creutzfeldt-Jakob disease (vCJD) were calculated for the two fibrin sealants licensed in the United States and for thrombin. These products were selected because their use in a clinical setting is, in most cases, optional, and both were relatively recently approved for marketing by the US Food and Drug Administration (FDA). Moreover, thrombin and fibrinogen both undergo two dedicated virus inactivation steps and/or removal steps in accord with the recommendations of regulatory agencies worldwide. Safety margins were determined by comparing the potential maximum viral loads in contaminated units to viral clearance factors, ultimately leading to the calculation of the residual risk per vial.

RESULTS

The residual risk of pathogen transmission per vial was calculated to be less than 1 in 10(-15) for HIV, HCV, HBV, and HAV for both fibrinogen and thrombin. Owing to the greater quantities that can be present and its greater thermal stability, the calculated risk for parvovirus transmission was 1 in 500,000 vials for fibrinogen and less than 1 in 10(7) per vial for thrombin. Assuming that vCJD is found to be present in plasma donations, its risk of transmission by these purified and processed plasma derivatives would appear to be very low.

CONCLUSIONS

The pathogen safety initiatives implemented by plasma fractionators over the past 10 to 20 years have resulted in products with excellent pathogen safety profiles. Of the agents examined, parvovirus continues to have the lowest calculated margin of safety. Despite this, parvovirus transmissions should be rare. Manufacturers are encouraged to continue exploring processes to further enlarge parvovirus safety margins and to continue exploring ways of eliminating prions.

Effects of 4-chloro-2,6-bis-(2-hydroxyl-benzyl)-phenol on healing of skin wounds and growth of bacteria

In this investigation, the effects of synthesized 4-chloro-2,6-bis-(2-hydroxyl-benzyl)-phenol (CBHBP) on cutaneous wound healing and growth of some of the wound contaminating microorganisms were studied. The antibacterial effects of this compound were then evaluated on Staphylococcus aureus (S. aureus), Pseudomonas aeruginosa (P. aeruginosa), Escherichia coli (E. coli) and Klebsiella spp., using solid dilution method. It was demonstrated that CBHBP has a significant antimicrobial activity against S. aureus but it is not effective in the case of other microorganisms studied in this experiment. The effect of local administration of CBHBP on healing of a standard full-thickness 2 cm skin incision of skeletally mature rats was evaluated. Histological changes together with mechanical properties and dry weight content of the healing tissues at the site of the lesions were assessed in treated and untreated animals. It was observed that the injured area of the treated animals was more organized and showed more fibroblasts and less inflammatory cells. Much better maturation criteria in treated tissues were observed in comparison with those of the untreated ones which contained numerous polymorphonuclear inflammatory cells after 14 days post-injury. Many infiltrated macrophages and lymphocytes were present even 28 days after injury induction in the haphazardly organized dermis and also in subcutaneous tissues of the untreated animals. The percentage dry weight content of the treated lesions at 14 days post-injury was remarkably higher than those of the untreated animals. The results of biomechanical tensile testing showed that the ultimate tensile strength and stress of the injured skin of the treated animals were higher than those of the untreated ones. From these results, it could be concluded that CBHBP can be effective on wound healing and may be considered as a treatment regimen after evaluating its mechanism of action as well as testing its contraindications.

Absorption of bioactive molecules into OASIS wound matrix

OBJECTIVE

To examine the ability of OASIS Wound Matrix to absorb, retain, and protect bioactive molecules from solution.

DESIGN

Samples of OASIS Wound Matrix were incubated in solutions of bioactive molecules, specifically heparin, albumin, fibronectin, basic fibroblast growth factor 2, and platelet-derived growth factor (PDGF). Half of the samples were then rinsed, and all of the samples were evaluated using enzyme-linked immunosorbent assays (ELISAs) and dye-mediated spectrophotometric methods for absorption and retention of the bioactive molecules. Protection of PDGF was measured by placing PDGF-incubated and control samples into a degradation solution containing plasmin. Intact PDGF levels were then evaluated using a PDGF-specific ELISA.

MAIN OUTCOME MEASURES

The main outcome measures were the amount of each bioactive molecule that was absorbed after incubation in solutions and retained after rinses as well as the amount of PDGF remaining after plasmin degradation.

MAIN RESULTS

OASIS Wound Matrix absorbed bioactive molecules from solution, selectively absorbed PDGF from serum, and protected PDGF from protease degradation.

CONCLUSIONS

Although OASIS Wound Matrix potentially has multiple functions in wound healing, it likely promotes wound healing, in part, by absorbing, retaining, and protecting bioactive molecules from the wound environment.

Androgens influence expression of matrix proteins and proteolytic factors during cutaneous wound healing

Excessive proteolytic activity is a feature of chronic wounds such as venous ulcers, in which resolution of the inflammatory response fails and restorative matrix accumulation is delayed as a consequence. The inflammatory actions of native androgens during the healing of acute skin wounds have lately been characterized. We have now investigated the hypothesis that such activities may impact upon the balance between anabolic and catabolic processes during wound healing. We report that wound deposition of both type I collagen and fibronectin is increased in castrated rats compared with control animals. This response is accompanied by early increases and later decreases in overall wound levels of the key collagenolytic enzymes, matrix metalloproteinase (MMP)-1 and MMP-13. Moreover, the activities of MMP-2 and MMP-9, two further enzymes that contribute to collagen digestion during venous ulceration, were significantly decreased in the wounds of castrated rats. Additional analyses provide evidence that androgens directly stimulate dermal fibroblast collagen production, which supports the suggestion that increased wound collagen deposition in androgen-deprived rats results from reduced matrix degradation (as opposed to enhanced matrix protein biosynthesis). Androgen-mediated dysregulation of the parallel processes of collagen deposition and turnover may underscore the delayed healing of cutaneous wounds in elderly male patients and further contribute to the increased incidence of non-healing wounds in this population.

Lymphatic involvement in the histopathogenesis of mucous retention cyst

Mucous retention cyst results from extravasation of saliva. Our intent was to study the role of lymphatics in its pathogenesis. Twenty-three surgical specimens of mucous retention cyst of the lip were examined for involvement of lymphatic vessels by a comparative immunohistochemical demonstration of lymphatic and blood vascular endothelial cells, as well as lymphatic and salivary contents. Mucous retention cysts were histopathologically classified into three stages: early, intermediate, and advanced. In the early stage, there was diffuse extravasation of mucous material in the interstitium of the lamina propria or the submucosal layer of the oral mucosa. In the intermediate stage, lymphatics, which were clearly revealed and immunohistochemically distinguished from blood vessels by monoclonal antibody D2-40, were dilated and finally ruptured, leaving fragments of lymphatic walls in the periphery of mucous pools. In the advanced stage, thick cyst walls of granulation tissue were formed around mucous retention. Lymphatics were no longer involved in the granulation tissue wall, which was actively driven by blood vessel formation. The results suggest that the lymphatic rupture seems to contribute to the enlargement in the pathogenesis of mucous retention cyst.

Fibronectin and Laminin Increase in the Mouse Brain after Controlled Cortical Impact Injury

The complex environment of the traumatically injured brain exhibits aspects of inhibition and ongoing cell death together with attempts at repair and regeneration. Elucidating these events and exploiting those factors involved in endogenous repair and regeneration may aid in developing more effective treatments for traumatic brain injury. Two extracellular matrix proteins critical to neural development--fibronectin and laminin--may also play a protective or reparative role in the injury response. While both of these proteins have been found to increase following human brain injury,the presence of these proteins has not been studied in a clinically-relevant animal model of blunt head trauma. In this study, we examined the spatiotemporal profile of both fibronectin and laminin in the mouse brain following controlled cortical impact injury. Fibronectin and laminin reactivity was localized to the injury penumbra up to 14 days post-injury and was significantly higher than uninjured controls at 3 days post-injury. Upon examining the spatial relationship of fibronectin and laminin to support cells, we found macrophages/activated microglia prominently present in the fibronectin-rich tissue, consistent with a role for fibronectin in facilitating debris clearing. Furthermore, reactive astrocyte processes were found sheathing laminin positive vasculature, suggesting that laminin may play a role in repairing the blood-brain barrier. These and other hypothesized reparative roles for fibronectin and laminin after traumatic brain injury are discussed.

Platelet-rich plasma: a review of biology and applications in plastic surgery

Healing of hard and soft tissue is mediated by a complex array of intracellular and extracellular events that are regulated by signaling proteins, a process that is, at present, incompletely understood. What is certain, however, is that platelets play a prominent if not deciding role. Controlled animal studies of soft and hard tissues have suggested that the application of autogenous platelet-rich plasma can enhance wound healing. The clinical use of platelet-rich plasma for a wide variety of applications has been reported; however, many reports are anecdotal and few include controls to definitively determine the role of platelet-rich plasma. The authors describe platelet biology and its role in wound healing; the preparation, characterization, and use of platelet-rich plasma; and those applications in plastic surgery for which it may be useful.

Platelet Rich Plasma: Biology and New Technology

Platelets play a central role in hemostasis and wound healing. The latter is mediated by release of secretory proteins on platelet activation, which directly or indirectly influences virtually all aspects of the wound healing cascade. Studies in basic science have shown a dose-response relationship between the platelet concentration and levels of secretory proteins, as well as between platelet concentration and certain proliferative events of significance to the healing wound. Technologies to provide autologous platelet rich plasma to the repair site are now being used in a wide variety of clinical applications, with the majority of such studies suggesting a role in the surgeon's armamentarium. Little standardization in the field exists, which has made it difficult to fully evaluate the literature on the subject and unequivocally establish applications for which the technology truly has merit. This article presents fundamental background on platelet biology and the role of platelets in both hemostasis and wound healing, as well as methods of preparing, characterizing, and using platelet rich plasma, to provide the reader a foundation on which to critically evaluate prior studies and plan future work.

Topical treatment of ocular surface defects: comparison of the epitheliotrophic capacity of fresh frozen plasma and serum on corneal epithelial cells in an in vitro cell culture model

Accelerated healing of ocular surface disorders was reported using serum for topical application. It is supposed that growth factors, fibronectin and vitamins in serum support the proliferation of corneal epithelial cells. The use of fresh frozen plasma (FFP) instead of serum is theoretically attractive, as it is more easily available from blood banks. In this study, serum and FFP were investigated for composition of epitheliotrophic factors and effect on corneal epithelial cells. Whole blood was taken from five donors. Serum and FFP were prepared, and the concentrations of epithelial growth factor (EGF), Platelet-derived growth factor (PDGF), transforming growth factor-beta1, fibronectin and vitamin A were determined. Immortalized human corneal epithelial cells were used to investigate growth, migration and differentiation in response to both blood products. Significant differences were found regarding the mediator composition of serum and FFP. Serum rather than FFP was significantly superior in stimulating cell growth, migration and differentiation. The epitheliotrophic capacity of blood products depends upon the composition of growth factors and vitamins. Blood clotting strongly influences the growth factor pattern. The superior epitheliotrophic capacity of serum might be due to the higher concentration of proliferation mediators such as EGF and PDGF and its higher content of vitamin A.

Angiogenesis in mucous retention cyst: a human in vivo-like model of endothelial cell differentiation in mucous substrate

BACKGROUND

Mucous retention cysts contain a mucous pool in the lumina, in which pure angiogenic processes are occasionally observed. By using this unique human material, our aim was to understand the in vivo angiogenic process.

METHODS

Fifteen surgical tissue samples of mucous retention cysts of the lip were examined for expression of vascular endothelial markers and extracellular matrix molecules by immunohistochemistry and in situ hybridization (ISH).

RESULTS

Endothelial cells forming new vascular channels showed immunopositivities for CD31, CD34, vascular endothelial growth factor (VEGF), and von Willebrand factor (vWF). These newly formed capillaries were surrounded by tenascin-positive matrices and further by a dense infiltration of CD68-positive cells with foamy to epitheloid appearances. Some of these cells were simultaneously positive for CD34, VEGF, and one of its receptors, Flk-1, and they showed definite mRNA as well as protein signals for tenascin. In addition, these cells often tended to be aligned, which suggested tubule formation.

CONCLUSION

The results suggest that monocyte/macrophage lineage cells are a major source for endothelial cells at least in mucous retention cysts and that tenascin produced by those cells plays an important role in differentiation of endothelial cells.

A fibronectin fragment induces tumor necrosis factor production of rat basophilic leukemia cells

Proteolytic digest of fibronectin (FN), but not intact FN, induced TNF-alpha secretion of rat basophilic leukemia (RBL-2H3) cells. As a result of the identification of FN fragment responsible for TNF-alpha secretion, a 30-kDa fragment derived from the carboxyl-terminal heparin-binding (Hep 2) domain of FN was isolated from the FN digest. The TNF-alpha secretion was abrogated by treatment of RBL-2H3 cells with cycloheximide, indicating the de novo synthesis of TNF-alpha, but not with polymyxin B, excluding the possible TNF-alpha induction by some contaminated lipopolysaccharides. A 22-mer synthetic peptide originated from the Hep 2 domain, termed FNIII14, which has been found to negatively modulate the beta1 integrin activation, had the ability to induce TNF-alpha production, whereas this activity of FNIII14 disappeared by shuffling a YTIYVIAL sequence essential for the integrin-inactivating activity. FNIII14 suppressed the spreading of RBL-2H3 cells on FN substrate, wherein RBL-2H3 cell proliferation was inhibited with FNIII14 in a dose-dependent manner. Thus, it appears that FN fragments containing the YTIYVIAL anti-adhesive site affect the activation status of RBL-2H3 mast cells, characterized by the stimulation of TNF-alpha production and growth suppression, probably due to negative regulation of beta1 integrin activity.