[Therapeutic effect of amniotic membrane-fibrin sealant cement on severe ocular surface alkali burn in rabbits]

Objective To prepare a biologically active amniotic membrane powder and explore its preservation conditions, and to evaluate the efficacy of the amniotic membrane (AM)-fibrin sealant (FS) cement made from the amniotic powder on the rabbit severe ocular surface alkali burn model. Methods Experimental research. Fresh AM was air-dried, cooled with liquid nitrogen, ground into amniotic powder and sterilized by radiation. The expression of transformed growth factor, nerve growth factor receptor (NGFR), hepatocyte growth factor (HGF), epidermal growth factor (EGF) and basic fibroblast growth factor (bFGF) after preparation and 10, 20 and 30 days after storage at room temperature, 4 ℃ and -20 ℃ was tested and compared with that in the fresh AM. The AM-FS cement containing different concentrations of amniotic powder and no amniotic powder was diluted. Rabbit corneal epithelial cells were cultured for 72 hours. The effects of different concentrations of amniotic powder on epithelial cell growth were observed by light microscopy, and the amniotic powder concentration with the largest absorbance value at 450 nm was selected for subsequent animal experiments. Thirty-two right eyes of 32 rabbits as the severe ocular surface alkali burn model were divided using the random counting method into the AM-FS cement group, fresh AM transplantation group, FS group and antibiotic control group (8 rabbits each group) and given different interventions. After weekly observation of corneal repair, hematoxylin and eosin staining, immunohistochemical staining of monocyte chemotaxis protein 1 (MCP-1)and vascular endothelial growth factor (VEGF) were performed and detected by light microscopy at 28 days. The logFC values of the growth factor or receptor expression difference ratio were corrected by BH; the data were analyzed by t-test and analysis of variance. Results: The expression of TGF in the amniotic membrane powder compared with the fresh amniotic membrane group (logFC=-0.11), and the expression of NGFR (HGF, EGF, bFGF) was higher than that of the fresh amniotic membrane group (logFC=-2.07, 0.72, 0.46, 2.62; P<0.05); the expression of HGF, bFGF and EGF in amniotic membrane powder stored for 10 days and 20 days were no lower than fresh amniotic membrane; at 30 days, the expression of growth factors or receptors except HGF and bFGF were decreased, and HGF, bFGF and EGF were no less than 4 ℃ and -20 ℃.The maximum A value was obtained for 0.25 mg/ml of the amniotic membrane powder after 72 hours of the CEC culture 0.98±0.05. The corneal recovery was better in the AM-FS and fresh amniotic membrane transplant groups, with corneal turbidity scores of 3.75±0.46 and 3.50±0.46, respectively, on 28 days, lower than antibiotics (4.29±0.45) (t=2.480, 3.629; P=0.019, 0.001). The corneal neovascular area in the antibiotic control group was compared with the other three groups (t=4.040, 4.339, 2.820; all P<0.001); the corneal neovascular area in the AM-FS group was (9.88±0.20) and (18.96±0.18) mm² at 7 and 28 days. The corneal neovascularization area at 7 and 28 days in the fresh AM group [(9.54±0.22) and (18.08±0.96) mm²] was smaller than the AM-FS group (t=3.085, 3.017, P=0.005, 0.005). Despite the tiny statistical difference (0.34, 0.88), there was no clinical difference. Hematoxylin and eosin staining showed corneal structures were intact in the AM-FS and fresh AM groups, the epithelial arrangement became normal, and the corneal healing was superior to the FS and antibiotic control groups. Immunohistochemistry showed that the positive expression of VEGF in the fresh AM group was weaker than that in the remaining three groups. MCP-1 was expressed to a similar extent in the AM-FS and fresh AM groups. Conclusions: The active cytokine had high expression and stable properties at room temperature. The AM-FS cement containing 0.25 mg/ml amniotic powder can promote the repair of corneal epithelium, reduce inflammatory reaction and corneal neovascularization after alkali burning in rabbit eyes.

TSG-6 mediates the effect of tendon derived stem cells for rotator cuff healing

BACKGROUND

Bone marrow stem cells (MSCs) were able to reduce fibrovascular tissues formation via TNF alpha-stimulated gene/protein 6 (6TSG-6) in various animal models. At the same time, tendon-derived stem cells (TDSCs) were able to promote rotator cuff healing; however, the mechanism is still unknown.

AIM

To investigate the role of TSG-6 in the treatment of rotator cuff healing with TDSCs.

MATERIALS AND METHODS

45 rats underwent unilateral detachment and repair of the supraspinatus tendon. 15 animals received TDSCs in a fibrin glue carrier(Group A), 15 received TSG-6 silenced TDSCs (Group B), and 15 received fibrin glue for control (Group C). Animals were sacrificed at 4 weeks and evaluated for the biomechanical testing. Statistical analysis was performed with an independent t test with significance set at p = 0.05.

RESULTS

The ultimate stress was greater in the TDSCs group (4.91 ± 1.41 N/mm(2)) as compared with the Control group (2.99 ± 1.04 N/mm(2)) (p < 0.05). However, when silent the expression of TSG-6, the TSG-6 silenced group (3.36 ± 0.96 N/mm(2)) showed no benefit over the control group (p = 0.32).

CONCLUSIONS

TSG-6 mediates the function of TDSCs to improve the structure and the attachment strength of the healing tendon-bone interface.

Effects of fibrin, thrombin, and blood on breast capsule formation in a preclinical model

BACKGROUND

The root cause of capsular contracture (CC) associated with breast implants is unknown. Recent evidence points to the possible role of fibrin and bacteria in CC formation.

OBJECTIVES

The authors sought to determine whether fibrin, thrombin, and blood modulated the histological and microbiological outcomes of breast implant capsule formation in a rabbit model.

METHODS

The authors carried out a case-control study to assess the influence of fibrin, thrombin, and blood on capsule wound healing in a rabbit model. Eighteen New Zealand white rabbits received four tissue expanders. One expander acted as a control, whereas the other expander pockets received one of the following: fibrin glue, rabbit blood, or thrombin sealant. Intracapsular pressure/volume curves were compared among the groups, and histological and microbiological evaluations were performed (capsules, tissue expanders, rabbit skin, and air). The rabbits were euthanized at two or four weeks.

RESULTS

At four weeks, the fibrin and thrombin expanders demonstrated significantly decreased intracapsular pressure compared to the control group. In the control and fibrin groups, mixed inflammation correlated with decreased intracapsular pressure, whereas mononuclear inflammation correlated with increased intracapsular pressure. The predominant isolate in the capsules, tissue expanders, and rabbit skin was coagulase-negative staphylococci. For fibrin and thrombin, both cultures that showed an organism other than staphylococci and cultures that were negative were associated with decreased intracapsular pressure, whereas cultures positive for staphylococci were associated with increased intracapsular pressure.

CONCLUSIONS

Fibrin application during breast implantation may reduce rates of CC, but the presence of staphylococci is associated with increased capsule pressure even in the presence of fibrin, so care should be taken to avoid bacterial contamination.

Implantation of VEGF transfected preadipocytes improves vascularization of fibrin implants on the cylinder chorioallantoic membrane (CAM) model

The successful substitution or augmentation of soft tissues by implantation of three dimensional cell constructs, consisting of human preadipocytes and fibrin glue as a carrier matrix, requires a rapid and homogeneous vascularization of the whole implant in order to provide a sufficient blood supply of centrally situated cells. Previous investigations have shown that under in vivo conditions primary human preadipocytes induce vascularization of fibrin matrices by secretion of several growth factors, such as VEGF and bFGF. The current study investigates whether vascularization of implants can be improved by transplantation of preadipocytes following transfection with a VEGF-vector. Transfection was performed by electroporation with an pCMX-GFP and pCMX-VEGF165 vector. Transfection efficiency (GFP expression) and VEGF expression were determined in vitro by FACS analysis and VEGF immunoassay, respectively. In vivo investigations to determine the vascularization of the implants were performed on the cylinder chorioallantoic membrane (CAM). Four million VEGF transfected cells were transferred within a fibrin matrix onto the CAM on the 7(th) day of incubation and after 8 days the vascularization of the implant was histologically examined and evaluated by means of a computer-assisted image analysis program. Transfection of preadipocytes with the GFP vector by electroporation yielded transfection efficiencies between 12% and 41% of surviving cells. Results of the VEGF immunoassay demonstrated that VEGF expression was significantly higher following transfection. Investigations on the CAM outlined a significantly higher rate of vascularization in the transfected vs. control population. Our investigations demonstrate that primary human preadipocytes can be successfully transfected by electroporation with a VEGF vector. The enhanced VEGF expression on transfected cells results in an increase of vascularization of the cell constructs on the CAM.

Adipose precursor cells (preadipocytes) induce formation of new vessels in fibrin glue on the newly developed cylinder chorioallantoic membrane model (CAM)

Successful augmentation of soft tissues by transplantation of preadipocytes within a matrix requires the formation of a new capillary network with connection to the host vessel system. Particularly, cells located centrally within the transplanted cell-matrix-construct represent a population with a blood supply questionable for survival. We demonstrated that under in vivo conditions preadipocytes possess the ability to induce and support the vascularization of the implant presumably by expression of several growth factors, such as VEGF (vascular endothelial growth factor) and bFGF (basic fibroblast growth factor). Fertilized White-Leghorn eggs were incubated under standardized conditions. Opening was performed at day three of incubation and preadipocytes with and without recombinant growth factors were transferred into a fibrin matrix and subsequently placed on the Chorioallantoic Membrane (CAM), respectively. Eight days later, the implanted constructs were explanted, histologically processed and vascularization evaluated by means of a computer-assisted image analysis program. Matrices containing preadipocytes displayed a significantly higher density of vascularization, whereas in the control group (fibrin without preadipocytes) no vessel ingrowth was observed. Daily application of recombinant growth factors added to the medium did not positively influence vascularization of the implant. Our investigations demonstrate that preadipocytes possess a strong angiogenic potential to induce and support neovascularization of 3D-fibrin matrices under in vivo conditions. Addition of recombinant growth factors did not result in any stimulatory effect. Neither did the application of fibrin alone demonstrate an angiogenic potential with regard to induction of vascularization.

Sustained release and osteogenic potential of heparan sulfate-doped fibrin glue scaffolds within a rat cranial model

This paper explores the potential therapeutic role of the naturally occurring sugar heparan sulfate (HS) for the augmentation of bone repair. Scaffolds comprising fibrin glue loaded with 5 microg of embryonically derived HS were assessed, firstly as a release-reservoir, and secondly as a scaffold to stimulate bone regeneration in a critical size rat cranial defect. We show HS-loaded scaffolds have a uniform distribution of HS, which was readily released with a typical burst phase, quickly followed by a prolonged delivery lasting several days. Importantly, the released HS contributed to improved wound healing over a 3-month period as determined by microcomputed tomography (microCT) scanning, histology, histomorphometry, and PCR for osteogenic markers. In all cases, only minimal healing was observed after 1 and 3 months in the absence of HS. In contrast, marked healing was observed by 3 months following HS treatment, with nearly full closure of the defect site. PCR analysis showed significant increases in the gene expression of the osteogenic markers Runx2, alkaline phosphatase, and osteopontin in the heparin sulfate group compared with controls. These results further emphasize the important role HS plays in augmenting wound healing, and its successful delivery in a hydrogel provides a novel alternative to autologous bone graft and growth factor-based therapies.

Preparation and characterization of human thrombin for use in a fibrin glue

Cryoprecipitate is frequently combined with thrombin to produce a fibrin sealant to enhance haemostasis during surgical procedures. We evaluated the thrombin produced from plasma using the Thrombin Processing Device (TPD)trade mark (Thermogenesis, Rancho Cordova, CA, USA). Plasma (250 mL) was processed in the CryoSeal FS System using the CP-3 disposable to produce cryoprecipitate by automated freezing and thawing. Simultaneously, thrombin was generated using the attached TPD. The cryoprecipitate and thrombin were harvested after approximately 50 min and then frozen and stored at -80 degrees C until analysis of total protein, fibrinogen, factor VIII (FVIII) activity, von Willebrand factor (vWF) and thrombin activity. Sodium dodecyl sulphate (SDS) gel electrophoresis was used to compare thrombin. After combining the thrombin with cryoprecipitate, the rate of clot initiation and strength was measured using a Thromboelastograph (TEG) (Haemoscope Corp, Skokie, IL, USA). Cryoprecipitate was produced, with a fibrinogen concentration of 22 +/- 7.7 g L(-1) (20 +/- 2% recovery), FVIII activity of 14.2 +/- 4.0 IU mL(-1) and vWF of 19.9 +/- 5.2 IU mL(-1). The separate thrombin product had a concentration of 64.3 +/- 16.7 IU mL(-1) of thrombin and a total protein of 0.39 +/- 0.1 g, with SDS gel electrophoresis showing a major band at 37 kD, as did the commercial human thrombin. The TEG curves of cryoprecipitate and TPD-produced or commercial thrombin were compared. The R values (time to clot initiation) were somewhat slower with the TPD-produced thrombin, but the maximum strength (MA) of the clots was similar. In conclusion, human thrombin can be produced during automated cryoprecipitate production. This thrombin is in sufficient concentration to initiate clotting and cross-linking of fibrin from cryoprecipitate to produce an entirely autologous fibrin glue.

Engineering of adipose tissue by injection of human preadipocytes in fibrin

BACKGROUND

Despite efforts of plastic surgeons in recent years to discover new alternatives, the techniques currently used for restoration of soft tissue defects still have disadvantages. The gold standard for soft tissue reconstruction remains autologous pedicled/free tissue transfer. This technique often results in high rates of operative morbidity and donor site deformity. Results obtained by autologous fat tissue transfer usually are disappointing because of a high graft resorption rate with unpredictable outcomes. Different tissue engineering approaches have been used in the past to generate adipose tissue. However, long-term results in terms of volume persistence have been disappointing.

METHODS

In this study, different concentrations of undifferentiated human preadipocytes in fibrin were injected into athymic nude mice (n = 8). Mice that had fibrin injection without cells served as control subjects (n = 8). The specimens were explanted after 1, 2, 6, and 9 months, with subsequent qualitative and quantitative analysis of adipose tissue formation by histologic and image analysis.

RESULTS

Within the first 4 weeks after initial volume reduction of the implants, the volume and shape of the implants with preadipocytes remained stable. The implants without cells were completely resorbed within 3 weeks. Histologic analysis demonstrated generation of stable adipose tissue with no signs of an inflammatory response or evidence of tissue necrosis in the implants containing preadipocytes. The best results were obtained after implantation of 30 million preadipocytes. Adipose tissue formation was not observed in the control group.

CONCLUSIONS

The findings demonstrate that long-term stable adipose tissue can be engineered in vivo by simple injection of human preadipocytes using fibrin as a carrier material. After further investigation, this approach may represent an alternative to the techniques currently used for soft tissue restoration.

The venous graft as an effector of early angiogenesis in a fibrin matrix

The arteriovenous loop (AV loop) model is gaining importance as a means of initiating and sustaining perfusion in tissue engineering constructs in vivo. This study represents an attempt to dissect the morphology of early arterialization and angiogenesis in the AV loop in a fibrin matrix with special focus on the interpositional venous graft (IVG) segment. An AV loop was constructed in 30 rats using the femoral vessels and an IVG. The AV loop was encased in an isolation chamber filled with a fibrin matrix. Evaluation methods included scanning electron microscopy (SEM) of corrosion casts, immune histology and micro magnetic resonance angiography (MRA). Direct luminal neovascular sprouting was evident between day 10 and day 14 from the vein and the IVG but not from the arterial segment. Arterialization of the IVG manifested itself on the corrosion casts as a gradual reduction in luminal caliber with onset after day 7. Microdissection of the microvascular replicas could demonstrate for the first time the presence of direct luminal sprouts from the IVG. MRA was used to display the shunt pattern of perfusion in the patent AV loop. From the three segments of the vascular axis in the AV loop the IVG is the most versatile for applications in the clinical as well as the experimental setting. Kinetics of angiogenesis warrant further investigation in the IVG.

Mechanical testing of fixation techniques for scaffold-based tissue-engineered grafts

Full-thickness defects in articular cartilage can be functionally restored by autologous chondrocyte implantation (ACI). In past years, numerous types of scaffolds for tissue-engineered cartilage implants have been developed and thoroughly characterized. However, the fixation stability of the implants has been rarely investigated despite its well-known importance for successful therapy. In this study, we have mechanically tested the fixation stability of four commonly used biomaterials for ACI attached by four different fixation techniques (unfixed, fibrin glue, chondral suture, and transosseous suture) in situ. Scaffolds based on polyglycolic acid (PGA) and polyglycolic acid and poly-L-lactic acid (PGLA), collagen membranes, and a gel-like matrix material were fixed within rectangular full-thickness cartilage defects of 10 x 15 mm(2) and loaded in tension until failure. Fibrin glue fixation of PGLA-scaffolds withstood a load of 2.18 6 +/- 0.47 N, chondral sutured PGA-scaffolds of 26.29 6 +/- 1.55 N, and transosseous fixed PGA-scaffolds of 38.18 6 +/- 9.53 N. The PGA-scaffold could be loaded highest until failure for all fixation techniques compared to the PGLA-scaffold and collagen membrane. Our findings serve as basis for selecting the most suitable fixation technique for scaffold-based tissue-engineered grafts according to the expected in vivo loads.

Perivenous Application of Fibrin Glue as External Support Enhanced Adventitial Adenovirus Transfection in Rabbit Model

BACKGROUND

Placement of an external support has been reported to prevent intimal hyperplasia of vein grafts. However, it's application limited by potential complications. Peri-adventitial gene delivery is a promising alternative therapy to reduce intimal hyperplasia, but it is limited by low and transient levels of gene transfection. To get more effective inhibition of intimal hyperplasia and to avoid the limitations associated with these two approaches, a study was undertaken to investigate whether mixing adenovirus with fibrin glue may increase the level and prolong the time period of gene expression.

METHODS

Right jugular vein to common carotid artery interposition grafting was performed in 36 male New Zealand white rabbits (2.5-3.0 kg) and the animals were divided into four groups: control group (n = 6); fibrin glue group (n = 6); Ad-GAL group (n = 12); fibrin glue/Ad-GAL group (n = 12). Commercially available fibrin glue and adenovirus expressing the gene for beta-galactosidase (Ad-GAL) was applied separately or in mixing around vein grafts. At 7th day and 14th day after implantation, the grafts were harvested to evaluate transfection rate. At 28th day the grafts were harvested for morphometric analysis.

RESULTS

Compared with weak staining in 2.1 +/- 0.5% in Ad-GAL alone grafts, a high level of beta-Galactosidase staining was evident in 13.2 +/- 4.6% in fibrin glue/Ad-GAL grafts at 7th day (P < 0.001). At 14th day, almost no staining (0%) was detected in Ad-GAL alone grafts. However, there was still a relative high level staining (6.3 +/- 3.8%) in fibrin glue/Ad-GAL grafts (P < 0.001 versus Ad-GAL alone group). At 28th day, a statistically significantly decrease in neointimal area (0.68 +/- 0.06 mm(2)versus 1.00 +/- 0.08 mm(2), P < 0.05) was shown in fibrin glue grafts compared with unsupported vein grafts (control group). The same statistically significantly difference was also existed in fibrin glue/Ad-GAL group and unsupported group in neointimal area (0.66 +/- 0.07 mm(2), P < 0.05).

CONCLUSIONS

A novel method of adventitial gene delivery using fibrin glue as external support is proposed. Fibrin glue may be an ideal candidate for controlled release delivery that would facilitate adventitial gene transfer.

Evaluation of a fibrin-based skin substitute prepared in a defined keratinocyte medium

The purpose of this study was to evaluate the influence of fibrin glue and aprotinin on the growth of adult human skin keratinocytes in defined serum-free conditions. The keratinocytes were cultured on cell culture plastics and on a fibrin matrix prepared from fibrin glue. The cell growth was measured by MTT assay, while the growth of clonogenic keratinocytes was evaluated by colony assay and expressed as colony-forming efficiency (CFE). The clonogenic potential of keratinocytes released from subconfluent and confluent cultures grown on fibrin glue was also studied by the colony assay. In comparison to a plastic culture surface the fibrin glue had significantly (P<0.05) increased the clonogenic potential of keratinocytes, as well as enhanced their growth. Keratinocytes released from subconfluent cultures grown on fibrin glue attained a significantly (P<0.05) higher percentage of clonogenic cells than their confluent parallels. At 75, 150, 300 and 450 KIU/ml aprotinin did not influence the growth of keratinocytes (P>0.2). A fibrin-based skin substitute produced in the defined keratinocyte medium could be safely used to treat a number of skin defects.

Structural design of the dry fibrin sealant dressing and its impact on the hemostatic efficacy of the product

We compared the hemostatic efficacy of a production version of a dry fibrin sealant dressing (DFSD) to a prototype that was previously successful in large animal studies. The results were used to improve manufacturing processes. Grade-V liver injuries were induced in swine and treated with gauze sponges (GAU), the prototype dressings (DFSD-1), or the scaled-up production version dressings (DFSD-2 in experiment 1 and DFSD-3 in experiment 2). Blood loss, hemostasis, resuscitation volume, and 60-min survival were quantified. In experiment 1, the DFSD-1 treatment reduced blood loss (p < 0.01), increased hemostasis at 4 min (p < 0.05), and improved survival (p < 0.05) compared with GAU. The DFSHD-2 decreased blood loss (p < 0.05) but did not increase hemostasis or survival significantly. Based on these results, manufacturing processes were altered, producing DFSD-3. In experiment 2, the DFSD-1 and DFSD-3 were equally effective in reducing blood loss (p < 0.01) and resuscitation volume (p < 0.05) compared with GAU. Hemostasis occurred more frequently in both the DFSD-1 and DFSD-3 groups (p < 0.01) compared with GAU. The structural design of DFSD-2 did not meet the efficacy requirement for release of the product. The subsequent change incorporated in DFSD-3 improved all hemostatic parameters of the dressings equal to those of the prototype product.

Basic studies on the clinical applications of platelet-rich plasma

Platelets, which contain many growth factors such as platelet-derived growth factor (PDGF) and transforming growth factor-beta (TGF-beta), are being used in clinical applications as platelet-rich plasma (PRP). Only a few studies, however, have been conducted on the growth factors present in PRP and on the clinical applications using the drug delivery system (DDS). For the purpose of clinical application, we first modified the PRP preparation method and assessed the amounts of growth factors contained in the human platelet concentrates. Furthermore, we assessed fibrin glue as a DDS of platelet concentrates. Platelet precipitations were made by twice centrifuging human whole blood. The precipitated platelet was resuspended to yield the platelet concentrates. The growth factor concentrations were measured. Fibrin glue sheets containing this platelet concentrate were implanted in rabbit pinna and samples were obtained for immunostaining (anti-PDGF antibody) to assess the use of PRP over time using the fibrin glue as the DDS. The mean concentration of growth factors present in the platelet concentrates was three times or greater than that of conventional PRP. Furthermore, the results indicated that when the platelet concentrate was used with fibrin glue as a carrier, the contents were released over a period of about 1 week. This raises the possibility that this system may be useful in clinical applications.

A stable matrix for generation of tissue-engineered nonthrombogenic vascular grafts

The potential of freeze-dried fibrin glue (FG) in combination with growth factor (GF) and gelatin (GEL) is evaluated for use as a matrix for endothelialization of artificial vascular grafts made of polytetrafluoroethylene (PTFE, Teflon) and polyethyleneterephthalate (Dacron). Improved adhesion and proliferation of human umbilical vein endothelial cells are demonstrated on different substrates coated with the FG-GF/FG-GF-GEL mixture, compared with the respective bare surfaces. The strength of adhesion of endothelial cells on the coated matrices was found to be adequate to resist shear stress when monolayers were exposed to forces of flow in an in vitro parallel plate flow chamber. The monolayers maintained physiological nonthrombogenic character as evidenced by in vitro platelet adhesion and response to agonist measurements. Nitric oxide synthesis by cells grown on the study matrices was also found to be normal. Thus, the matrix composition and the coating technique, as presented here, can be easily applied to generate tissue-engineered biomaterials with a nonthrombogenic endothelial cell monolayer for cardiovascular implants. The freeze-drying of the coated matrix ensures prolonged stability and thus the materials can be stored in a ready-to-use state for endothelial cell sodding or seeding.

Fate of fibrin sealant in pericardial space

BACKGROUND

Although fibrin sealant (Beriplast, Aventis Behring, Marburg, Germany) has been widely used as a supplementary measure for hemostasis during cardiac surgery in Europe and is becoming popular in the United States, the pharmocokinetics of fibrin sealant applied in pericardial space has not been elucidated.

METHODS

A small incision was made on the epicardial surface of the left ventricle of a rat, and the incision was sutured. Total 0.2 ml of fibrin sealant containing iodine 125 (125I)-labeled fibrinogen, aprotinin, blood coagulation factor XIII and thrombin was applied to the area around the suture line.

RESULTS

Distributions of 125I-labeled fibrinogen in the heart on postoperative days 1, 3, 7, and 14 were 48.2% +/- 1.8%, 20.7% +/- 2.2%, 0.15% +/- 0.02%, and 0.01% +/- 0.02%, respectively. The radioactivity was negligible in the blood, liver, spleen, and kidney except for the thyroid in which the radioactivity increased to 7.9% +/- 0.7% and 4.3% +/- 0.4%, respectively, on postoperative days 7 and 14. Iodine 125-labeled fibrinogen concentrations of the heart and other organs showed a similar change in the time course of distribution. Dense and thick fibrin network, observed on postoperative day 1, had dissipated and was thinner with collagen formation by postoperative day 7.

CONCLUSIONS

Fibrin sealant applied to the pericardial cavity regresses rapidly and plays an important role in wound healing.

Biochemical properties of the fibrinogen component of a fibrin glue before and after severe dry heat treatment

Functional biochemical properties of 5 batches of the fibrinogen component of a fibrin glue produced by the ZLB Central Laboratory, Bern, each consisting of 4 different in-process samples (taken after the first and second precipitation step, lyophilization, and dry-heat treatment) were studied in vitro. We focused our attention on the effect of the anti-viral treatment of the lyophilized product by dry heat for 1 h at 100 degrees C. A slight reduction in maximal turbidity of all heat-treated samples was observed during the clotting assay compared to nontreated samples. Treatment with dry heat did not result in generation of fibrinogen fragments that might accelerate tissue-plasminogen-activator (t-PA)-enhanced plasminogen to plasmin conversion. The time course of fibrin cross-linking by factor XIII showed no differences between heated and unheated samples. This result indicates that exposure of the fibrinogen component to severe heat neither reduced activity of factor XIIIa nor affected the correct alignment of cross-linking sites in polymerized fibrin. Incubation of fibrinogen with thrombin, plasminogen, and t-PA resulted in a slightly enhanced degradation of fibrin derived from the heat-treated samples. The amount of residual moisture, determined to be within the range of 0.6-2.1% before heat treatment, did not influence clotting, cross-linking, and fibrinolysis parameters. In conclusion, the virus inactivation treatment by dry heat for 1 h at 100 degrees C induces no significant alterations of the in vitro biochemical properties of the fibrinogen component of this fibrin glue.

Neurotrophic agents in fibrin glue mediate adult dorsal root regeneration into spinal cord

OBJECTIVE

The aim of the present study was to determine whether neurotrophic factors (NTFs) exogenously administered in fibrin glue assisted cut dorsal root axons of adult rats to regenerate into the spinal cord.

METHODS

Rats received intraspinal implants of fibrin glue containing neurotrophin-3, brain-derived NTF, ciliary NTF, or Dulbecco's modified Eagle's medium (control) into left dorsal quadrant cavities aspirated in the lumbar enlargement. The transected L5 dorsal root stump was placed at the bottom of the lesion cavity and was secured between the fibrin glue and the spinal cord. Regenerated dorsal root axons were subsequently labeled with immunohistochemical methods to demonstrate those that contained calcitonin gene-related peptide.

RESULTS

Calcitonin gene-related peptide-immunoreactive dorsal root axons regenerated across the dorsal root-spinal cord interface of rats with fibrin glue containing neurotrophin-3, brain-derived NTF, or ciliary NTF, entered the spinal cord, and frequently arborized within clusters of motoneuronal cell bodies. Only a few axons regenerated into the spinal cord of animals with fibrin glue implants that lacked NTF, and their growth within the spinal cord was extremely limited. The results of quantitative studies confirmed these observations.

CONCLUSION

Our results indicate that neurotrophin-3, brain-derived NTF, and ciliary NTF enhance dorsal root regeneration into spinal cord and that fibrin glue is an effective medium for intraspinal delivery of NTF. This method of delivering NTF may therefore provide a strategy for restoring injured spinal reflex arcs.

A novel surgical glue composed of gelatin and N-hydroxysuccinimide activated poly(L-glutamic acid): Part 1. Synthesis of activated poly(L-glutamic acid) and its gelation with gelatin

Although fibrin glue has been widely used as a surgical adhesive, its components, fibrinogen and thrombin, obtained from human blood are not completely free from the risk of virus infection due to acquired immune deficiency and hepatitis. Recently, we have reported that a polymer pair composed of gelatin and poly(L-glutamic acid) (PLGA) promptly forms a gel and can firmly bond to soft tissues when crosslinked with the aid of water-soluble carbodiimide (WSC). The present study was undertaken to design a new PLGA-gelatin glue without using WSC. Two kinds of PLGA with molecular weights of 71 and 22 kDa were employed to prepare N-hydroxysuccinimide (NHS) activated derivatives. The NHS-activated PLGA could be synthesized at high yields and was found to be stable for an extended time without losing the ability to crosslink with gelatin when stored under a dry-cold condition. This NHS-activated PLGA could spontaneously form a gel with gelatin in an aqueous solution within a short time, comparable to a commercial fibrin glue, when gelation was allowed to proceed at pH 8.3. The NHS-activated PLGA prepared from PLGA with the molecular weight of 22 kDa could be readily dissolved at high concentrations and its ability to form a gel was maintained for more than 10 min when an acidic 8% NHS-activated PLGA solution was used. The bonding strength of PLGA gelatin glues with natural tissue was higher than that of fibrin glue. These findings strongly suggest that this combination of gelatin and NHS-PLGA is very promising as a surgical adhesive and may possibly replace fibrin glues prepared from human blood components.

The sustained release of antibiotic from freeze-dried fibrin-antibiotic compound and efficacies in a rat model of osteomyelitis

The kinetics of drug release from fibrin adhesive agent (consisting of fibrinogen, factor 8, thrombin, aportinin and calcium chloride)-antibiotic compound and efficacy on rat experimental osteomyelitis were studied. To enhance the slow release activities of antibiotic, a mixture of fibrin clots was freeze-dried. Effects of freeze-drying were to make a fibrin clot an interlinked pore and to increase crosslinking rate containing an antibiotic. A diffusion test from aminoglycoside (Arbekacin Sulfate: 200 mg) compound was carried out. In vitro study freeze-dried antibiotic compound (FFAC: 1 cm3) was placed in saline (3 ml). The saline was replaced every 48 h and the previous solution was stored at -45 degrees C until assay. The result was that a concentration of 0.4 mg/l, sufficiently high to control Staphylococcus aureus strain IM2-42, was maintained within nine exchanges of saline after 18 days. In vivo animal experiments, FFAC (2 x 2 x 3 mm) were tested in rats with established Staphylococcus aureus osteomyelitis in the proximal tibia. The animals were observed for radiographic signs of infection and tissue was examined histopathologically. Bacterial counts by bone cultures were statistically lower in rats implanted with FFAC than in those only given a drug-free FFC and curettage. Radiographical and histological observations also showed beneficial effects of the FFAC. The results suggest that the FFAC provide a simple drug delivery system, and may be a promising alternative treatment for osteomyelitis.

Application of thrombin based fibrin glue and non-thrombin based batroxobin glue on intact human blood vessels: evidence for transmural thrombin activity

An alternative method of uniting small diameter vessels to obtain tissue union while limiting the thrombogenic effect of suture placement at a vessel anastomosis involves the use of a thrombin based fibrin glue as a surgical sealant. This investigation addresses whether the in vitro application of a thrombin based glue (TG), or batroxobin glue (BG), a non-thrombin based glue made with the snake venom enzyme batroxobin, alters intravascular platelet deposition (PD) or cleaves blood fibrinogen, as measured by fibrinopeptide A (FPA) production, when the respective glue is applied to the external surface of an intact human placental artery or an artery with an anastomosis. When TG was applied to the adventitial surface of an intact vessel or an anastomosis (n = 7) of control and experimental vessels, there was a significant increase in intraluminal platelet deposition, an effect not realized with BG (n = 12, intact vessel TG p = 0.01, BG p = 0.66, anastomosis TG p <0.01, BG p <0.01). Both TG and BG significantly increased FPA levels when human whole blood was perfused through both intact vessels or vessels containing an anastomosis when compared to control vessels (intact vessel TG and BG p <0.01, anastomosis TG and BG p <0.01). Labelled thrombin studies document the rapid passage of thrombin through an intact vessel wall or vessels with an anastomosis when TG was applied to the adventitial surface of the vessel. The data suggest that TG and BG are drug delivery systems for their respective enzymes that either pass through or transfer a message across not only a surgically created anastomosis, but also an intact vessel wall.

Isolation and characterization of a new clotting factor from Bothrops jararacussu (jararacuçu) venom

A detailed procedure for the isolation of a new clotting enzyme from the venom of Bothrops jararacussu (common name jararacuçu) is described. The estimated mol. wt of the native protein was 30,100 but 37,500 after reduction by dithiothreitol. Two major close bands corresponding to pI 5.18 and 5.20 were detected by electrofocusing but, after methanolysis, a single band focused at pI 8.20. The mol. wt of the protein moiety of this glycoprotein was 28,500, showing V-V-G-A-D-N-C-N-F-N... as N-terminal sequence. The content of neutral sugar was 4.8% and that of total sugars 5.3%. This clotting factor degraded only the A alpha-chain of the fibrinogen molecule. The stability of the clot, when produced in the presence of aprotinin opens new uses for snake clotting enzymes in the production of fibrin glue.

Thyroplasty type I with ceramic shim

To prevent side effects from a silicone shim in Isshiki thyroplasty type I, we used a ceramic shim in 10 patients with unilateral recurrent laryngeal nerve paralysis. No published reports have described the use of ceramic in this type of surgery. According to the degree of glottic insufficiency, ceramic shims of various heights were inserted into the fenestration made in the thyroid ala. All patients experienced subjective improvement of voice postoperatively. Laryngoscopies in most cases showed that glottic insufficiency improved postoperatively. In the postoperative examination, the maximum phonation time improved an average of 3.7 s, and the mean flow rate improved an average of 331 ml/s. We have analyzed the relationship of these improvements to the degree of glottic insufficiency and have compared our results with those of other investigators.

Preparation and use of fibrin glue in surgery

Fibrin glue (FG) is used to control bleeding, to adhere tissues together, and to seal tissue defects. FG is prepared from platelet-rich plasma or by mixing concentrated fibrinogen solutions with thrombin. Concentrated fibrinogen solutions are produced by cryoprecipitation or by chemical precipitation of plasma. The literature on FG preparation is reviewed in order to compare the advantages and disadvantages of the different products reported and to summarize the clinical applications. It is concluded that additional studies are needed to fully evaluate the advantages and disadvantages of fibrinogen concentrated using cryoprecipitation and chemical precipitation and that specific advantages exist for use of both pooled homologous and autologous blood.

Interactions between osteoclastic cells and biodegradable polymers in vitro

The use of implants to stabilize fractured diaphyseal bone, to handle difficult bone damage and to perform augmentation or replacement procedures in bone has become a common method in bone surgery. In most cases metal implants were used. Biodegradability of implant materials offers new perspectives. Restoration of the physiological status in the implant site becomes possible. Allergic reaction and second operations to remove the implants can be avoided and transitional aid in wound healing by the use of biomaterials can be achieved. An in-vitro system was established to investigate the interactions between osteoclasts and biomaterials, since it is the osteoclasts which are potentially able to resorb or degrade implants. The cell's resorption capabilities as well as its morphological behavior were documented. Two biodegradable and four nonbiodegradable materials were tested. The non-degradable materials provoked specific cell behaviour patterns but were not resorbed. Fibrin tissue adhesive sealant, however, displayed resorption lacunae mediated by osteoclasts, whereas polydioxanone (PDS) showed no resorption sites but normal cellular morphology when compared to the standard control (cells on hydrophilic coated teflon dishes). Both materials appeared to be well accepted by osteoclasts. This test system was established for the valuation of biodegradable implant materials and can be used to characterize new materials concerning their resorbability and biocompatibility without superposition by other cell systems.