Haptotactic and growth stimulatory effects of fibrin(ogen) and thrombin on cultured fibroblasts

Autologous Platelet-Rich Plasma Injection and Platelet-Rich Fibrin Glue Insertion for the Treatment of Extensive Supralevator Anorectal Fistula: A Case Report

Supralevator fistula stays a challenge in general surgery. We present a case with supralevator anorectal fistula and subsequent retroperitoneal necrotizing fasciitis in which autologous platelet-rich plasma and platelet-rich fibrin glue were used for fistula closure. A 59-year-old man was admitted with pelvic pain and fever. Abdominopelvic sonography and CT scan reported a deep horseshoe-shaped anorectal abscess with extension to the pelvic floor, supralevator, psoas, retroperitoneal muscles, and kidneys. He was managed with antibiotics, abscess drainage, repeated radical surgical debridement, and necrosectomy. After 30 days, he was discharged, but he returned to the office with the complaint of purulent discharge from the hypogastric region and a diagnosis of fistula formation. Platelet-rich plasma was injected around the fistula into the tissue, and platelet-rich fibrin glue was introduced to the fistula tract. At the 11-month follow-up, the patient did not have voiding dysfunction, constipation, diarrhea, or fistula tract infection. Autologous platelet-rich plasma injection and platelet-rich fibrin glue insertion suggest a secure and effective approach for treating supralevator anorectal fistula.

Interposing layer of fibrin glue: A new horizon in vesico-vaginal fistula repair

AIM

In this study our idea is to compare the effectiveness of using interposing layer of fibrin glue to omental flap in reducing the failure of laparoscopic vesicovaginal fistula repair.

METHODS

Forty patients with fairly large vesicovaginal fistula were enrolled and divided in two groups of 20 each. We have used fibrin glue in one group and omental flap in the other group.

RESULT

Of 20 patients in fibrin glue group no failure was seen, while 5 patients out of 20 in omental flap group had failure.

CONCLUSION

This result is statistically significant and hence use of fibrin glue to be considered during laparoscopic repair of vesicovaginal fistulas.

Tissue Concentrations of Zinc, Iron, Copper, and Magnesium During the Phases of Full Thickness Wound Healing in a Rodent Model

Wound healing is a complex orchestration of processes involving cell proliferation, migration, differentiation, anabolism, and catabolism in order to restore skin continuity. Within these processes, elements such as metallic ions are involved due to their implications in cell behavior and enzymatic activity regulation. This study analyzed the kinetics of zinc, iron, copper and magnesium concentrations in a full thickness open wound rat model over 14 days. We made wounds with a diameter of 6 mm on the back of Lewis rats and let them heal naturally prior to analysis by histology and inductively coupled plasma mass spectrometry analysis. Histological and immunofluorescence analysis confirmed an inflammation phase until 7 days, epithelial proliferation phase from 16 h to 10 days, and remodeling phase from 7 days onward. These defined phases were correlated with the measured metal element kinetics. Zinc concentrations showed an inverted parabolic progression between 30.4 and a maximum of 39.9 μg/g dry weight. Magnesium values had a similar pattern between 283 and 499 μg/g dry weight. Copper concentrations, on the other hand, followed an inverted sigmoid trend with a decrease from 9.8 to 1.5 μg/g dry weight. Iron had a slight decrease in concentration for 24 h followed by an increase to a maximum of 466 μg/g dry weight. In conclusion, zinc, iron, and copper, even though differing in their total mass within the wound, exhibited concentration curve transitions at day 3. Interestingly, this time point correlates with the maximum proliferating keratinocyte rate during the proliferation phase.

Isolation and expansion of high yield of pure mesenchymal stromal cells from fresh and cryopreserved placental tissues

The injection of placental stromal cells isolated from fetal human tissues (f-hPSC) was reported to indirectly induce tissue regeneration in different animal models. A procedure of f-hPSC isolation from fragments of both selected fresh or cryopreserved bulk placental neonate tissues is proposed, based on their high migratory potential,. The fragments of the desired fetal placental tissues are adhered to a culture dish by traces of diluted fibrin and covered with culture medium. Spontaneous migration of pure f-hPSC from the tissue fragments to the cell culture dishes is followed by their rapid expansion by numerous passages. The isolated f-hPSC express typical mesenchymal surface antigens, including CD29, CD105, CD166 and CD146, with negative expression of white blood cell lineage and endothelial cells markers. Optimal yields of f-hPSC cultures can also be obtained from tissue samples cryopreserved in medium composed of 10% dimethyl sulfoxide (M₂SO) and 50% fetal calf serum. Slightly better yields are obtained with media supplemented with 1% human albumin. Medium with 5% M₂SO and/or 0.25 mg/ml PEG yielded inferior results. The f-hPSC from fresh or cryopreserved tissues express similar cell markers and growth kinetics. The proposed isolation protocol may also be applied for high yield isolation of stromal cells from fresh and cryopreserved tissue of other organs.

Activated dendritic cells delivered in tissue compatible biomatrices induce in-situ anti-tumor CTL responses leading to tumor regression

Dendritic cell (DC) based anti-cancer immunotherapy is well tolerated in patients with advanced cancers. However, the clinical responses seen after adoptive DC therapy have been suboptimal. Several factors including scarce DC numbers in tumors and immunosuppressive tumor microenvironments contribute to the inefficacy of DCs as cellular vaccines. Hence DC based vaccines can benefit from novel methods of cell delivery that would prevent the direct exposure of immune cells to suppressive tumor microenvironments. Here we evaluated the ability of DCs harbored in biocompatible scaffolds (referred to as biomatrix entrapped DCs; beDCs) in activating specific anti-tumor immune responses against primary and post-surgery secondary tumors. Using a preclinical cervical cancer and a melanoma model in mice, we show that single treatment of primary and post-surgery secondary tumors using beDCs resulted in significant tumor growth retardation while multiple inoculations were required to achieve a significant anti-tumor effect when DCs were given in free form. Additionally, we found that, compared to the tumor specific E6/E7 peptide vaccine, total tumor lysate induced higher expression of CD80 and CD40 on DCs that induced increased levels of IFNγ production upon interaction with host lymphocytes. Remarkably, a strong immunocyte infiltration into the host-implanted DC-scaffold was observed. Importantly, the host-implanted beDCs induced the anti-tumor immune responses in the absence of any stromal cell support, and the biomatrix structure was eventually absorbed into the surrounding host tissue. Collectively, these data indicate that the scaffold-based DC delivery may provide an efficient and safe way of delivering cell-based vaccines for treatment of primary and post-surgery secondary tumors.

Fibrin-based biomaterials: modulation of macroscopic properties through rational design at the molecular level

Fibrinogen is one of the primary components of the coagulation cascade and rapidly forms an insoluble matrix following tissue injury. In addition to its important role in hemostasis, fibrin acts as a scaffold for tissue repair and provides important cues for directing cell phenotype following injury. Because of these properties and the ease of polymerization of the material, fibrin has been widely utilized as a biomaterial for over a century. Modifying the macroscopic properties of fibrin, such as elasticity and porosity, has been somewhat elusive until recently, yet with a molecular-level rational design approach it can now be somewhat easily modified through alterations of molecular interactions key to the protein's polymerization process. This review outlines the biochemistry of fibrin and discusses methods for modification of molecular interactions and their application to fibrin based biomaterials.

The molecular basis of memory. Part 2: chemistry of the tripartite mechanism

We propose a tripartite mechanism to describe the processing of cognitive information (cog-info), comprising the (1) neuron, (2) surrounding neural extracellular matrix (nECM), and (3) numerous "trace" metals distributed therein. The neuron is encased in a polyanionic nECM lattice doped with metals (>10), wherein it processes (computes) and stores cog-info. Each [nECM:metal] complex is the molecular correlate of a cognitive unit of information (cuinfo), similar to a computer "bit". These are induced/sensed by the neuron via surface iontophoretic and electroelastic (piezoelectric) sensors. The generic cuinfo are used by neurons to biochemically encode and store cog-info in a rapid, energy efficient, but computationally expansive manner. Here, we describe chemical reactions involved in various processes that underline the tripartite mechanism. In addition, we present novel iconographic representations of various types of cuinfo resulting from"tagging" and cross-linking reactions, essential for the indexing cuinfo for organized retrieval and storage of memory.

A novel method for iatrogenic vesicovaginal fistula treatment: autologous platelet rich plasma injection and platelet rich fibrin glue interposition

PURPOSE

Vesicovaginal fistula remains a challenge in surgical therapy. In this study autologous platelet rich plasma and platelet rich fibrin glue were used as a minimally invasive approach for vesicovaginal fistula closure.

MATERIALS AND METHODS

Data including age, parity, ICIQ-UI (International Consultation on Incontinence Questionnaire-urinary incontinence), ICIQ-QOL (International Consultation on Incontinence Questionnaire-quality of life), duration of leakage, fistula diameter and complications were collected before and after the intervention. Platelet rich plasma and platelet rich fibrin glue were prepared from 12 patients' own blood. De-epithelialization was performed around the fistula until a small hemorrhage occurred. Platelet rich plasma was injected around the fistula into the tissue and platelet rich fibrin glue was interpositioned in the tract.

RESULTS

No complications were observed during and after the injection. Mean ± SD patient age was 39.75 ± 8.45 years. At 6-month followup 11 patients considered themselves clinically cured, and transvaginal physical examination and cystography were normal. ICIQ-UI and ICIQ-QOL showed remarkable improvement in 11 patients. One patient had significant improvement but did not consent to the second injection. None of the patients had voiding dysfunction, urinary incontinence, retention or urinary tract infection.

CONCLUSIONS

Autologous platelet rich plasma injection and platelet rich fibrin glue interposition offer a safe, effective and novel minimally invasive approach for the treatment of vesicovaginal fistula which obviate the need for open surgery. We propose calling this technique the Hamidi-Shirvan method.

Marrow-derived stromal cell delivery on fibrin microbeads can correct radiation-induced wound-healing deficits

Skin that is exposed to radiation has an impaired ability to heal wounds. This is especially true for whole body irradiation, where even moderate non-lethal doses can result in wound healing deficits. Our previous attempts to administer dermal cells locally to wounds to correct radiation-induced deficits were hampered by poor cell retention. Here we improve the outcome by using biodegradable fibrin microbeads (FMB) to isolate a population of mesenchymal marrow-derived stromal cells (MSC) from murine bone marrow by their specific binding to the fibrin matrix, culture them to high density in vitro and deliver them as MSC on FMB at the wound site. MSC are retained and proliferate locally and assist wounds gain tensile strength in whole body irradiated mice with or without additional skin only exposure. MSC-FMB were effective in 2 different mouse strains but were ineffective across a major histocompatability barrier. Remarkably, irradiated mice whose wounds were treated with MSC-FMB showed enhanced hair regrowth suggesting indirect effect on the correction of radiation-induced follicular damage. Further studies showed that additional wound healing benefit could be gained by administration of G-CSF and AMD3100. Collagen strips coated with haptides and MSCs were also highly effective in correcting radiation-induced wound healing deficits.

High thrombin concentrations in fibrin sealants induce apoptosis in human keratinocytes

Over the last century many studies have been performed to assess the impact of fibrin sealant (FS) components on cells. Because of the noncovalent bonding of thrombin to fibrin during fibrin clot formation, we wanted to further evaluate the impact of fibrin bound thrombin on cell viability. Initially, we quantified the activity of thrombin in three different, commercially available FS. This information was used to prepare fibrin clots covering a range of thrombin concentrations from 4 to 820 IU mL(-1), but which were identical with respect to all other constituents. Although these fibrin clots did not differ in their three-dimensional structure, clots prepared with highly concentrated thrombin (820 IU mL(-1)) failed to support adhesion and spreading of primary human keratinocytes (NHEK). The number of attached cells was also significantly reduced on high thrombin activity clots. We hypothesized that these observations are not only the consequence of decreased proliferation but of apoptotic mechanisms, since the expression of cleaved caspase 3 and 7 was strongly enhanced on fibrin clots with high thrombin activity. This was accompanied by an induction of expression of Trail-R2 which is a receptor known to mediate apoptosis signals. Blocking of thrombin activity by hirudin led to an improvement of cell morphology and to an increase in number of attached cells. In addition, the induction of caspase 3 and 7 was also reduced. Thus, here we report for the first time that fibrin bound thrombin does not only decrease proliferation (as already published by others), it also does induce NHEK apoptosis when present at high concentrations.

Effect of age and diabetes on the response of mesenchymal progenitor cells to fibrin matrices

Mesenchymal stem cells are showing increasing promise in applications such as tissue engineering and cell therapy. MSC are low in number in bone marrow, and therefore in vitro expansion is often necessary. In vivo, stem cells often reside within a niche acting to protect the cells. These niches are composed of niche cells, stem cells, and extracellular matrix. When blood vessels are damaged, a fibrin clot forms as part of the wound healing response. The clot constitutes a form of stem cell niche as it appears to maintain the stem cell phenotype while supporting MSC proliferation and differentiation during healing. This is particularly appropriate as fibrin is increasingly being suggested as a scaffold meaning that fibrin-based tissue engineering may to some extent recapitulate wound healing. Here, we describe how fibrin modulates the clonogenic capacity of MSC derived from young/old human donors and normal/diabetic rats. Fibrin was prepared using different concentrations to modulate the stiffness of the substrate. MSC were expanded on these scaffolds and analysed. MSC showed an increased self-renewal on soft surfaces. Old and diabetic cells lost the ability to react to these signals and can no longer adapt to the changed environment.

Mast cell activation by fibrinogen-related homologous c-terminal peptides (haptides) modulates systemic blood pressure

BACKGROUND

Haptides are a family of short peptides homologous to C-termini sequences of fibrinogen chains β and γ (haptides Cβ and preCγ, respectively) which were previously shown to penetrate and bind cells.

OBJECTIVES

This work investigates the systemic effect of the haptides with possible clinical implications.

METHODS

Intra-arterial monitoring in rats recorded the haptides' effects on systemic blood pressure. In parallel, their effect was also tested in vitro on isolated rat peritoneal mast cells and on human mast cells.

RESULTS

Intra-arterial monitoring in rats showed that intravenous administration of low haptides concentrations (35-560 μg/kg rat) caused a shocklike behavior with transient decrease in the systolic and diastolic blood pressure by up to 55% (P < .05) in a dose-dependent manner and a minor increase in their heart rate. Randomly scrambled sequences of the haptides had no such effect, suggesting a specific interaction with receptors. Intravenous administration of blockers to histamine receptors H1 and H2 before haptides administration attenuated this effect. Furthermore, in vitro incubation of human LAD2 mast cell line or isolated rat peritoneal mast cells with the haptides caused degranulation of the mast cells. We found that the haptides Cβ and preCγ activated mast cells causing histamine release, resulting in a steep decrease in blood pressure, comparable to anaphylactic shock.

CONCLUSION

In treating vascular occlusive diseases, massive fibrinolysis is induced, and haptide-containing sequences are released. We suggest that treatment with histamine receptor blockers or with mast cell stabilizing agents in such pathological conditions may overcome this effect.

A family of cell-adhering peptides homologous to fibrinogen C-termini

A family of cell-adhesive peptides homologous to sequences on different chains of fibrinogen was investigated. These homologous peptides, termed Haptides, include the peptides Cβ, preCγ, and CαE, corresponding to sequences on the C-termini of fibrinogen chains β, γ, and αE, respectively. Haptides do not affect cell survival and rate of proliferation of the normal cell types tested. The use of new sensitive assays of cell adhesion clearly demonstrated the ability of Haptides, bound to inert matrices, to mediate attachment of different matrix-dependent cell types including normal fibroblasts, endothelial, and smooth muscle cells. Here we present new active Haptides bearing homologous sequences derived from the C-termini of other proteins, such as angiopoietin 1&2, tenascins C&X, and microfibril-associated glycoprotein-4. The cell adhesion properties of all the Haptides were found to be associated mainly with their 11 N-terminal residues. Mutated preCγ peptides revealed that positively charged residues account for their attachment effect. These results suggest a mechanism of direct electrostatic interaction of Haptides with the cell membrane. The extended Haptides family may be applied in modulating adhesion of cells to scaffolds for tissue regeneration and for enhancement of nanoparticulate transfection into cells.

Platelet-rich fibrin membranes as scaffolds for periosteal tissue engineering

OBJECTIVES

Platelet-rich fibrin (PRF)-based membranes have been used for covering alveolar ridge augmentation side in several in vivo studies. Few in vitro studies on PRF and no studies using human periosteal cells for tissue engineering have been published. The aim is a comparison of PRF with the commonly used collagen membrane Bio-Gide as scaffolds for periosteal tissue engineering.

MATERIAL AND METHODS

Human periosteal cells were seeded on membrane pieces (collagen [Bio-Gide] and PRF) at a density of 10(4) cells/well. Cell vitality was assessed by fluorescein diacetate (FDA) and propidium iodide (PI) staining, biocompatibility with the lactate dehydrogenase (LDH) test and proliferation level with the MTT, WST and BrdU tests and scanning electron microscopy (SEM).

RESULTS

PRF membranes showed slightly inferior biocompatibility, as shown by the LDH test. The metabolic activity measured by the MTT and WST tests was higher for PRF than for collagen (BioGide). The proliferation level as measured by the BrdU test (quantitative) and SEM examinations (qualitative) revealed higher values for PRF.

CONCLUSION

PRF appears to be superior to collagen (Bio-Gide) as a scaffold for human periosteal cell proliferation. PRF membranes are suitable for in vitro cultivation of periosteal cells for bone tissue engineering.

Efficient isolation and chondrogenic differentiation of adult mesenchymal stem cells with fibrin microbeads and micronized collagen sponges

Background: Mesenchymal stem cells (MSCs) have been demonstrated to potentially undergo chondrogenic differentiation. We propose a new matrix for stem cell-based chondrogenesis using dense fibrin microbeads (FMBs) combined with grounded dehydrothermally crosslinked collagen sponges (micronized collagen). Methods: In this study, MSCs were isolated from bone marrow of transgenic green fluorescent protein C57/Bl mice by FMBs in high yield. After 48 h in slowly rotating suspension culture, micronized collagen was added. Results: The cells on the FMBs migrated to the collagen pieces and formed aggregates that developed into cartilage-like structures. Following chondrogenic differentiation, alcian blue staining and collagen type II immunohistochemistry demonstrated the presence of chondrocytes in the 3D structures. PCR for the expression of aggrecan and collagen type II genes supported these findings. The in vitro structures that formed were used for ectopic subdermal implantation in wild-type C57/Bl mice. However, the chondrogenic markers faded relative to the pre-implant in vitro structures. Conclusion: We propose that FMBs with micronized collagen could serve as a simple technology for MSC isolation and chondrogenesis as a basis for implantation.

The use of fibrin based matrices and fibrin microbeads (FMB) for cell based tissue regeneration

BACKGROUND

Due to its good cell attachment capabilities and promotion of cell migration, fibrin serves as an interim cell-binding matrix in wounded tissues. Due to their fast degradation, unprocessed fibrin matrices have limited use in tissue engineering.

OBJECTIVE

To describe stable fibrin-based matrices for isolation, growth and delivery of stem cells for implantation to enhance tissue regeneration.

METHODS

Fibrin microbeads (FMB) were produced by moderate-heat condensation of fibrin particles in oil without compromising the cell binding capability of the fibrin.

RESULTS

Mesenchymal stem cells (MSC) were separated from different sources at much higher yields with FMB. They were further expanded on them in suspension without trypsinization and passages. Cells on FMB could be induced to differentiate into different phenotypes, such as bone and cartilage. This enabled implantation of the cells on FMB for cell-based tissue regeneration.

CONCLUSIONS

FMB technology provides a simple and effective method for cell separation, expansion in suspension and delivery for tissue regeneration.

High-Yield Isolation, Expansion, and Differentiation of Murine Bone Marrow-Derived Mesenchymal Stem Cells Using Fibrin Microbeads (FMB)

Transplantation of adult mesenchymal stem cells (MSCs) could provide a basis for tissue regeneration. MSCs are typically isolated from bone marrow (BM) based on their preferential adherence to plastic, although with low efficiency in terms of yield and purity. Extensive expansion is needed to reach a significant number of MSCs for any application. Fibrin microbeads (FMB) were designed to attach mesenchymal cells and to provide a matrix for their expansion. The current study was aimed at isolating a high yield of purified BM-derived mouse MSCs based on their preferential adherence and proliferation on FMB in suspension cultures. MSCs could be downloaded to plastics or further expanded on FMB. The yield of MSCs obtained by the FMB isolation technique was about one order of magnitude higher than that achieved by plastic adherence, suggesting that these cells are more abundant than previously reported. FMB-isolated cells were classified as MSCs by their fibroblastic morphology, self-renewal ability, and expression profile of their surface antigens, as examined by flow cytometry and immunostaining. In cell culture, the isolated MSCs could be induced to differentiate into three different mesodermal lineages, as demonstrated by histochemical stains and by RT-PCR analyses of tissue-specific genes. MSCs were also able to differentiate into osteocytes while still cultured on FMB. Our results suggest that FMB might serve as an efficient platform for the isolation, expansion, and differentiation of mouse BM-derived MSCs to be subsequently implanted for tissue regeneration.

High-yield isolation, expansion, and differentiation of rat bone marrow-derived mesenchymal stem cells with fibrin microbeads

Fibrin microbeads (FMB), made of extensively cross-linked dense and partially denatured fibrin, were used as a matrix for efficient isolation of mesenchymal stem cells (MSC) from rat bone marrow (BM). After 2 days of incubation of FMB with whole BM in suspension, a high number of cells of mesenchymal origin attached to the FMB. On the 14th day after their transfer to plastic, the yield of the cells isolated via FMB was approximately 3-4 times higher than that obtained by currently used protocols based solely on plastic adhesion. This implies that the number of MSC in BM may be higher than previously reported. FACS analyses and immunostaining showed the mesenchymal characteristics of these cells by positive staining for fibronectin, vimentin, CD49E, and CD29. Immediately after isolation, less than 20% of the cells still expressed the hematopoietic markers CD11b and CD45. Most of these cells were eventually eliminated after further expansion of the isolated cells on plastic. Cells isolated via FMB were expanded in culture for more than 4 months and could be defined as MSC along this time period based on their ability to differentiate into precursors of mesenchymal tissues, such as osteogenic, adipogenic, and chondrogenic cells. Similar differentiation plasticity was observed in clones derived from single cells from whole MSC populations isolated via FMB. Based on our results we propose that FMB can serve as a 3-dimensional biodegradable matrix for isolation, differentiation, and possibly implantation of MSC for tissue regeneration.

Isolation of mesenchymal stem cells from G-CSF-mobilized human peripheral blood using fibrin microbeads

Adult mesenchymal stem cells (MSC) that are able to differentiate into various mesenchymal cell types are typically isolated from bone marrow, but their significant presence in human peripheral blood (PB) is controversial. Fibrin microbeads (FMB) that bind matrix-dependent cells were used to isolate MSC from the mononuclear fraction of mobilized PB of adult healthy human donors treated with a granulocyte colony-stimulating factor. Isolation by plastic adherence resulted in a negligible number of MSC in all samples tested, whereas FMB-based isolation yielded spindle-shaped cell samples that could further expand on plastic or on FMB in eight out of the 11 samples. The yield of these cells at days 17-18 after the harvest was approximately 0.5% of the initial cell number. The isolated cells were grown on plastic and characterized by FACS analysis and immunohistochemistry for specific markers. Following culturing and first passage, the FMB-isolated cells stained positive for mesenchymal stromal cell markers CD90 and CD105, expressed vimentin and fibronectin and were negative for hematopoietic markers CD45 and CD34. These cells could differentiate into osteoblasts, adipocytes and chondrocytes. This study indicates that FMB may have special advantage in isolating MSC from sources such as mobilized PB, where the number of such cells is scarce.

Hemostatic agents and tissue glues in urologic injuries and wound healing

Biosurgical preparations designed to promote surgical hemostasis and tissue adhesion are now available to the urologist and are increasingly being used across all surgical disciplines. Fibrin sealant and gelatin thrombin matrix are the two most widely used bio-surgical adjuncts in urology. Complex reconstructive, oncologic, and laparoscopic genitourinary procedures are those most appropriate for sealant use. This article details the diverse urologic applications of biosurgical products in the management of urologic injuries and the promotion of wound healing.

Current applications of fibrin sealant in urologic surgery

Biosurgical preparations designed to promote surgical hemostasis and tissue adhesion are being increasingly employed across all surgical disciplines. Fibrin sealant is the most widely studied and utilized biosurgical adjunct in urology. Complex reconstructive, oncologic, and laparoscopic genitourinary procedures are those most appropriate for sealant use. This article details the diverse urologic applications of fibrin sealant in the management of genitourinary injuries, surgery, and complications.

Interactions of carboplatin with fibrin(ogen), implications for local slow release chemotherapy

The effect of carboplatin (CPt) on fibrin(ogen) clot formation and the possible use of this combination for local slow release chemotherapy were examined. CPt significantly reduced thrombin-induced fibrin clotting time (CT) and increased clot turbidity in a concentration-dependent manner. When CPt was mixed with physiological levels of fibrinogen (>1 mg/ml), electron-dense nanoparticles (3 nm) were formed, as demonstrated by both optical particle counter and transmission electron microscopy (TEM). Upon thrombin-induced coagulation, the CPt nanoparticles were trapped within the fibrin mesh. At higher fibrinogen levels (>5 mg/ml), the 3-nm CPt nanoparticles aggregated, so that approximately 2% and approximately 0.5% of the CPt on the fibrinogen appeared as larger particles of 10 and 50 nm, respectively. Dialysis experiments showed that 60-70% of the CPt was released from the fibrin clot within one hour as a non-particulate soluble form, while approximately 30% of particulate CPt were retained. Up to 5 mg/ml this portion of firmly attached CPt was dependent of the initial drug level. CPt released from the fibrin by either diffusion or by fibrinolysis exhibited cytotoxic activity towards retinoblastoma (RB) cell lines (Y-79 and Weri RB1) equivalent to free drug. Our study indicates that CPt enhances fibrin clot formation and suggests the use of fibrin with high dose CPt for slow release chemotherapy against localized tumors such as retinoblastoma.

DOES FIBRIN SEALANT DECREASE IMMEDIATE URINARY LEAKAGE FOLLOWING RADICAL RETROPUBIC PROSTATECTOMY?

PURPOSE

We determined the effectiveness of fibrin sealant in decreasing postoperative urinary leakage following radical retropubic prostatectomy performed by 1 surgeon at Washington Hospital Center.

MATERIALS AND METHODS

Between April and November 2003 our group treated 32 consecutive patients with prostate cancer with radical retropubic prostatectomy. The first 16 patients (control) underwent the Walsh described technique and the second group of 16 patients had an additional application of fibrin sealant around the urethro vesical anastomosis. Postoperative drain output was measured every 8 hours. The results of the 2 groups were compared.

RESULTS

The Blake drain was removed after 4 nursing shifts (times 1 through 4) in 81% (13 of 16) of the control group and in 100% (16 of 16) of the fibrin sealant group. The fibrin sealant group had significantly less drainage output overall compared with the control group (p = 0.005). The drainage output from each group decreased with time at a significant rate independent of each other (p <0.001), and there was a larger difference (p = 0.04) in output between groups at times 1 and 2 compared with times 3 and 4. There was no relationship between the amount of urinary drainage and drain output. There was no immediate morbidity associated with the use of fibrin sealant.

CONCLUSIONS

The application of fibrin sealant to the urethro vesical anastomosis during radical retropubic prostatectomy does decrease postoperative drain output. With earlier drain removal, patients would benefit from less discomfort and from skilled nursing requirements. In select patients early drain removal could accelerate discharge home.

A novel in vitro dermal wound-healing model incorporating a response to mechanical wounding and repopulation of a fibrin provisional matrix

Previously our laboratory, and others, described an in vitro model for the study of fibroblast wound repopulation. The so-called punch-wounded, fibroblast-populated collagen lattice has been used extensively in tissue repair research. We now identify certain shortcomings with this model, which have led to its enhancement by the introduction of a provisional matrix fabricated in situ from fibrinogen and alpha-thrombin. In the previous model, fibroblasts repopulate the wound defect (WD) as a monolayer of cells and on reaching confluence, a process reminiscent of fibroplasia fills the wound space. The enhanced model, with fibrin acting as a provisional matrix, allowed fibroblasts to repopulate the WD as a three-dimensional network of cells that were morphologically different from cells migrating over the collagen substratum of the previous model. Fibroblast repopulation of the fibrin matrix was typically around double the rate of repopulation of the empty wound space. We propose this model as an enhanced, yet sufficiently reproducible, model for the study of fibroblast responses to tissue damage. It can be further enhanced by the addition of other cell types and matrix components.

Liposome transduction into cells enhanced by haptotactic peptides (Haptides) homologous to fibrinogen C-termini

Haptides are 19-21mer cell-binding peptides equivalent to sequences on the C-termini of fibrinogen beta chain (Cbeta), gamma chain (preCgamma) and the extended alphaE chain of fibrinogen (CalphaE). In solution, Haptides accumulated in cells by non-saturable kinetics [Exp. Cell Res. 287 (2003) 116]. This study describes Haptide interactions with liposomes and Haptide-mediated liposome uptake by cells. Haptides became incorporated into negatively charged liposomes, changing their zeta potential. Atomic force microscopy and particle sizing by light scattering showed that the liposomes dissolved Haptide nanoparticles and absorbed them from solution. Pre-mixing fluorescent rhodamine-containing liposomes or "stealth" doxorubicin (DOX)-containing liposomes (Doxil) with Cbeta, preCgamma or to a lesser degree CalphaE, significantly enhanced their uptake by fibroblasts and endothelial cells. Confocal microscopy showed Haptide-induced liposome uptake saturated above approximately 40 microM Haptide. Cytotoxicity tests with lower concentrations of Doxil liposomes indicated that premixing with approximately 40 microM Cbeta or preCgamma increased their toxicity by one order of magnitude. It was evident that the liposomes complexed with an amphiphilic Haptide are transduced through cell membranes, probably by a non-receptor-mediated process. These results suggest that Cbeta or pre-Cgamma could be employed to augment the cellular uptake of drugs in liposomal formulations.

Wound pharmacobiology

Wound healing after major joint surgery involves a series of complex events. Over the past several years, thrombin has emerged as a pivotal participant in wound healing. The high incidence of venous thromboembolism following major joint replacement has made prophylaxis with pharmacologic agents a component of postoperative management. Anticoagulant agents of various classes affect different degrees of thrombin inhibition by virtue of their in vivo mechanisms of action. By inhibiting thrombin activity directly, with or without antithrombin III or other antithrombins, traditional anticoagulants may retard the wound healing process and impair completion. Newer, more selective anticoagulants may provide not only more effective alternatives for venous thromboembolism prophylaxis surrounding major orthopedic procedures, but also an anticoagulant environment more favorable to wound healing.

New cell attachment peptide sequences from conserved epitopes in the carboxy termini of fibrinogen

Fibrinogen seems to contribute significantly to cell binding and recruitment into wounds besides its major role in clot formation. We describe 19- to 21-mer cell-binding (haptotactic) peptides from the C-termini of fibrinogen beta-chain (Cbeta), the extended alphaE chain, and near the C-terminal of the gamma-chain. When these peptides were covalently bound to a biologically inert matrix such as Sepharose beads (SB), they elicited beads attachment to cells, mostly of mesenchymal origin (including fibroblasts, endothelial cells, and smooth muscle cells) as well as some transformed cell lines. Based on such haptotactic activity, these peptides were termed "haptides." By contrast, peptides homologous to fibrinogen C-termini alpha- and gamma-chains elicited no such activity. The haptide Cbeta could not block the interaction of fibroblasts with antibodies directed against integrins beta(1), alpha(v), alpha(v)beta(1), alpha(v)beta(3), and alphaIIbeta(3). Moreover, GRGDS peptide could not inhibit enhanced cell binding to SB-Cbeta, as expected from an integrin-mediated process. In soluble form the haptides were accumulated in cells with nonsaturable kinetics without any toxic or proproliferative effects in concentrations up to 80 microM. These findings suggest that the conserved haptidic sequences within fibrin(ogen) can be associated with the adhesion and migration of cells into fibrin clots and may have a significant role in normal wound healing and in various pathological conditions.

Effect of radiation and cell implantation on wound healing in a rat model

BACKGROUND AND OBJECTIVES

Having shown that intra-dermal injection of fibroblasts decreases the effect of radiation on healing of superficial wounds, we now test the effect of fibroblasts and syngeneic marrow stromal cells on irradiated deep and superficial wounds.

METHODS

Wistar rats received bilateral buttock irradiation followed by partial excision of the gluteus muscle bilaterally. In Protocol 1, one irradiated wound was treated with 1.2 x 10(7) autologous cells injected intra-dermally. In Protocol 2, the experimental side was treated with a fibrin and autologous cell implant (1.2 x 10(7) cells). Twenty-one days later, wound mechanical characteristics were tested. In Protocol 3, the effect of pooled marrow stromal cells on healing of superficial irradiated wounds in Lewis rats was similarly tested.

RESULTS

The fibrin-fibroblast implant (Protocol 2) had no effect on wound mechanics. Superficial injection of fibroblasts (Protocol 1) significantly improved wound breaking strength when compared to the control group (mean +/- SEM, breaking strength: treated 504.6 +/- 37.0 g vs. control 353.4 +/- 35.2 g, P = 0.005). The dermal injection of marrow stromal cells also resulted in marked increases in breaking strength (mean +/- SEM, breaking strength: treated 338.5 +/- 39.9 g vs. control 187.1 +/- 12.0 g, P < 0.01). In both Protocols 1 and 3, ultimate tensile strength and toughness were increased in the side receiving cell transplantation.

CONCLUSIONS

Cell implantation holds promise for decreasing the effect of radiation on healing of irradiated wounds.

Characterizing fibrin glue performance as modulated by heparin, aprotinin, and factor XIII

We describe the performance of fibrin glue (FG) as modulated by heparin, aprotinin, or factor XIII levels. In vitro tests and a rat kidney excision model demonstrated that the hemostatic efficacy of fibrin was not modulated by aprotinin. Overlapping rat skin sections demonstrated that adhesion strength (AS) was proportional to the area of overlap as well as to fibrinogen levels. AS was not modulated by exogenous heparin or aprotinin and was independent of the endogenous factor XIII in fibrinogen. SDS-PAGE developed by Coomassie or Western blots with anti-gamma chain antibody confirmed that normal skin sections contain adequate trans-glutaminase to maximally cross-link normal, as well as XIII-depleted, fibrin. Fibrin glue (FG) sprayed onto rat skin incision wounds with a dual channel spray applicator acted in 2 phases: initially (day 1), compared to wounds stapled without or treated with only thrombin, FG significantly increased breaking strength. In the second phase of wound healing (after day 3), all groups achieved increased but equivalent breaking strength. FG containing aprotinin (to 3000 U/m; Immuno, Behringwerke, Germany) exhibited initial tissue bonding strength equivalent to fibrin without aprotinin, but histological examination showed delayed fibrinolysis and a concomitant slower regeneration of granulation tissue. Thus, our data indicated that aprotinin was not particularly beneficial to wound healing and that the endogenous factor XIII level in the fibrinogen did not contribute significantly to skin bonding. Rather, the tissue supplied adequate trans-glutaminase activity required to crosslink fibrin to itself and to the tissue.

Fibrin microbeads for isolating and growing bone marrow-derived progenitor cells capable of forming bone tissue

It has been demonstrated that bone marrow (BM)-derived pluripotent stem cells can be incorporated into muscle, bone, nerve, lung, stomach, intestine, and skin. Fibrin-based biodegradable microbeads (FMB) were developed for culturing, in suspension, a high density of cells, mostly of mesenchymal origin. In the current study, FMB were used to isolate and expand mesenchymal progenitor cells from BM of mice and rats. Cells from BM isolated on FMB (FMB-BM cells) were visualized by fluorescent confocal microscopy and quantified by a modified MTS colorimetric assay. Downloading the BM cells from FMB onto plastic induced their differentiation into islets of cells with osteogenic phenotype that secreted mineralized extracellular matrix. This was augmented by inducers of osteogenesis, such as ascorbic acid, beta-glycerophosphate, and dexamethasone, or osteoblast-growth peptides (OGP). Implanting FMB-BM cells under the kidney capsule in mouse tested the osteogenic potential of these cells in vivo. Thirty days after implantation, bone structures with typical BM elements were seen in 8/53 kidneys in 6-Gy-irradiated mice and in 1/10 kidneys in nonirradiated recipients; bone formation was verified by soft x-ray imaging and elemental analysis that showed elevated Ca and Fe in the implant region. FMB-BM cells - downloaded onto plastic flasks, cultured for 2 weeks, mechanically harvested and then implanted - induced 100% bone formation in both irradiated (6/6) and nonirradiated (3/3) mice. Histology revealed well-organized bone structures under the kidney capsule, including osteoblasts and typical elements of BM. Our findings demonstrate that FMB are capable of isolating and expanding progenitor cells from BM for osteogenesis and possibly for regenerating other mesenchymal tissues.

Plasminogen activator inhibitor type 1 increases neointima formation in balloon-injured rat carotid arteries

BACKGROUND

Elevated plasma levels of plasminogen activator inhibitor type 1 (PAI-1) are associated with myocardial infarction, atherosclerosis, and restenosis. PAI-1 is increased in atherosclerotic arteries and failed vein grafts. No experimental data, however, support a causal relationship between elevated PAI-1 expression and vascular lesions. Paradoxically, data generated in PAI-1 knockout mice suggest that PAI-1 might decrease lesion formation after arterial injury and that PAI-1 gene transfer might prevent restenosis.

METHODS AND RESULTS

Using the rat carotid balloon injury model and a PAI-1-expressing adenoviral vector, we tested whether elevated arterial PAI-1 expression would alter neointima formation. Compared with control-transduced arteries, neointima formation in PAI-1-transduced arteries was initially retarded. By 14 days, however, the intimas of PAI-1-transduced arteries were significantly larger than intimas of control-transduced arteries (1.6+/-0.1x10(5) versus 1.2+/-0.1x10(5) micrometer(2), n=18 to 19, P<0.03). PAI-1 expression in individual arteries correlated with increased cell proliferation at 4 and 8 days after injury (R=0.6, P<0.02 and P<0.006). PAI-1 expression also correlated with fibrin(ogen) accumulation (R=0.77, P<0.001), and fibrin(ogen) accumulation correlated strongly with proliferation (R=0.86, P<0.00001).

CONCLUSIONS

Increased expression of PAI-1 in the artery wall promotes neointima growth after balloon injury. Therefore, despite encouraging data generated in other animal models, PAI-1 is not a promising agent for gene therapy to prevent restenosis. Moreover, our data associate elevated PAI-1 expression with fibrin(ogen) accumulation and increased cell proliferation. These data suggest a mechanism to explain the association between elevated PAI-1 expression and the progression of arterial disease.

The respiratory burst response of surface-adhering leukocytes. A key to tissue engineering

Biomaterials implanted into tissue will participate in the complex signalling between cells during wound healing. Recent studies have revealed that crucial cellular signalling pathways are regulated by the extra- and intracellular redox states and that reactive oxygen species function as intercellular signal molecules. Biomaterials have been shown to affect the respiratory burst response of surface-adhering leukocytes, thus interfering with major regulatory functions of cells also in surrounding tissues. The respiratory burst of surface-adhering leukocytes may thus be a key event in the understanding of biomaterial interaction with tissues, and the aim of this review is to highlight this field of research.

Elastase activity enhances the adhesion of neutrophil and cancer cells to vascular endothelial cells

BACKGROUND

Elastase activity in cancer cells has been reported to promote their metastasis. Hence, we analyzed the influence of elastase activity of cancer cells on their responsive adhesion to vascular endothelial cells.

MATERIALS AND METHODS

Human pancreatic (S2-007, S2-013, S2-020, S2-028) and colonic (COLO205) cancer cell lines were used. S2-007, S2-013, and S2-020 possess high elastase activity, whereas S2-028 and COLO205 have low elastase activity. Adhesive reactions of these cancer cells and neutrophils to TNFalpha-activated HUVEC were analyzed. Bound cells onto HUVEC were counted after incubation for 10 min. The effects of suppression of elastase activity by ZD8321, a potent elastase inhibitor, and supplementation of human neutrophil elastase (NE) on the adhesive reactions were also analyzed. In addition, E-selectin expression on HUVEC and concentrations of soluble E-selectin in the medium were measured.

RESULTS

Adhesion of cells with high intracellular elastase activity to TNFalpha-activated HUVEC was suppressed by ZD8321. On the other hand, adhesion of cells with low elastase activity was enhanced by exogenous NE. Expression of E-selectin, a key molecule in leukocyte-endothelial cell interaction, on HUVEC was increased by NE. Soluble E-selectin concentration in the medium increased after the adhesive reaction between neutrophils and HUVEC. This increase was thought to be due to the shedding of cell surface E-selectin. Such responses were inhibited by ZD8321.

CONCLUSION

Elastase activity has a biological function of stimulating both the E-selectin expression on HUVEC and the resultant adhesive reaction of cancer cells with them. Inhibition of elastase activity is a potent strategy for controlling cancer metastasis.

Fibrin microbeads (FMB) as biodegradable carriers for culturing cells and for accelerating wound healing

We have developed biodegradable fibrin-derived microbeads as potent cell carriers. The fibrin-derived microbeads, 50-200 microm in diameter, were tested for their attachment to a wide range of cell types. Fibrin-derived microbeads were shown to be greatly haptotactic to cells (such as endothelial cells, smooth muscle cells and fibroblasts), which respond to fibrinogen in contrast to keratinocytes and different cell lines derived from leukocytic lineage. The cells on fibrin-derived microbeads could be maintained for more than 10 d and achieved a high density. 31P-nuclear magnetic resonance was employed to monitor phosphate metabolism in cells, with densities on the order of 100 million cells per g of fibrin-derived microbeads. The 31P-nuclear magnetic resonance adenosine triphosphate and phosphocreatine signals, equivalent to the signal obtained with perfused normal skin, indicated that metabolism of cells on fibrin-derived microbeads was responsive to oxygenation and nutrients. Light, fluorescent, and confocal laser microscopy revealed that the porous fibrin-derived microbeads accommodate up to 200-300 cells due to their high surface area which minimized contact inhibition. Cells could degrade the fibrin-derived microbeads and be transferred to seed culture flasks without trypsinization. In a pig skin wound healing model, fibrin-derived microbeads + fibroblasts were transplanted into full thickness punch wounds. This procedure was compared with other treatment modalities, such as the addition of human platelet-derived growth factor BB or fibrin-derived microbeads alone. By the third day after wounding, only the wounds in which fibroblasts on fibrin-derived microbeads were added showed significant formation of granulation tissue. Based on the above, we project many uses of our novel fibrin-derived microbead technology for cell culturing, wound healing and tissue engineering.