Effect of human basic fibroblast growth factor on fibroblast proliferation, cell volume, collagen lattice contraction: in comparison with acidic type

Using different geometries to modulate the cardiac fibroblast phenotype and the biomechanical properties of engineered connective tissues

Tissue engineering with human cardiac fibroblasts (CF) allows identifying novel mechanisms and anti-fibrotic drugs in the context of cardiac fibrosis. However, substantial knowledge on the influences of the used materials and tissue geometries on tissue properties and cell phenotypes is necessary to be able to choose an appropriate model for a specific research question. As there is a clear lack of information on how CF react to the mold architecture in engineered connective tissues (ECT), we first compared the effect of two mold geometries and materials with different hardnesses on the biomechanical properties of ECT. We could show that ECT, which formed around two distant poles (non-uniform model) were less stiff and more strain-resistant than ECT, which formed around a central rod (uniform model), independent of the materials used for poles and rods. Next, we investigated the cell state and could demonstrate that in the uniform versus non-uniform model, the embedded cells have a higher cell cycle activity and display a more pronounced myofibroblast phenotype. Differential gene expression analysis revealed that uniform ECT displayed a fibrosis-associated gene signature similar to the diseased heart. Furthermore, we were able to identify important relationships between cell and tissue characteristics, as well as between biomechanical tissue parameters by implementing cells from normal heart and end-stage heart failure explants from patients with ischemic or dilated cardiomyopathy. Finally, we show that the application of pro- and anti-fibrotic factors in the non-uniform and uniform model, respectively, is not sufficient to mimic the effect of the other geometry. Taken together, we demonstrate that modifying the mold geometry in tissue engineering with CF offers the possibility to compare different cellular phenotypes and biomechanical tissue properties.

The Effect of Pulsed Electric Field on Expression of ECM proteins: Collagen, Elastin, and MMP1 in Human Dermal Fibroblasts

Electrical stimulation of tissues has many uses in pain management, antibacterial treatment, and wound healing. The electric field stimulates epidermal migration and increases fibroblast cell proliferation. Here we show the effects of electrical field (EF) stimulation of human dermal fibroblasts (HDF) on the expression of collagen, elastin, and collagenase (MMP1; matrix metalloproteinase 1). The effects of EF stimulation are evaluated in terms of changes in cell morphology and extracellular matrix (ECM) protein expression, defined as intracellular concentration of collagen, elastin, and MMP1. HDF are stimulated in a bioreactor using square wave voltage pulses for up to 24 h. The pulse voltage (0-10V), pulse bias (0, +), pulse time (10-1000 ms), and rest time (0.1-10 s) were varied. We show that expression of collagen, elastin, and MMP1 increases in response to applied EF. The intracellular concentration of ECM proteins more than doubles depending on stimulation conditions with a threshold of effective stimulation above 3V/cm. The short time voltage pulses used for EF stimulation are more effective, while the rest time between pulses has a small effect on intracellular concentration of collagen, MMP1 and elastin. The previously studied HDF stimulation with chemical factors (i.e. TNF-α, TGF-β) shows negative correlation between concentration of collagen and MMP1. Contrary to that observation, we show that EF stimulation causes increase in the intracellular concentration of both collagen and MMP1. We also demonstrate that the transdermal stimulation of HDF in subcutaneous tissue is possible, thus it might be utilized in the future to improve the wound healing and tissue regeneration process.

The contribution of CMP kinase to the efficiency of DNA repair

Cellular supply of deoxynucleoside triphosphates (dNTPs) is crucial for DNA replication and repair. In this study, we investigated the role of CMP/UMP kinase (CMPK), an enzyme catalyzes CDP formation, in DNA repair. Knockdown of CMPK delays DNA repair during recovery from UV damage in serum-deprived cells but not in the cells without serum deprivation. Exogenous supply of cytidine or deoxycytidine facilitates DNA repair dependent on CMPK in serum-deprived cells, suggesting that the synthesis of dCDP or CDP determines the rate of repair. However, CMPK knockdown does not affect the steady state level of dCTP in serum-deprived cells. We then found the localization of CMPK at DNA damage sites and its complex formation with Tip60 and ribonucleotide reductase. Our analysis demonstrated that the N-terminal 32-amino-acid of CMPK is required for its recruitment to DNA damage sites in a Tip60-dependent manner. Re-expression of wild-type but not N-terminus deleted CMPK restores the efficiency of DNA repair in CMPK knockdown cells. We proposed that site-specific dCDP formation via CMPK provides a means to facilitate DNA repair in serum-deprived cells.

Fibroblast growth factors 1 and 2 inhibit adipogenesis of human bone marrow stromal cells in 3D collagen gels

Multipotent human bone marrow stromal cells (hBMSCs) are the common progenitors of osteoblasts and adipocytes. A shift in hBMSC differentiation in favor of adipogenesis may contribute to the bone loss and marrow fat accumulation observed in aging and osteoporosis. Hence, the identification of factors modulating marrow adipogenesis is of great therapeutic interest. Fibroblast growth factors 1 (FGF1) and 2 (FGF2) play important roles in several cellular processes including differentiation. Their role in adipogenesis is, however, still unclear given the contradictory reports found in the literature. In this work, we investigated the effect of FGF signaling on hBMSC adipogenesis in a 3D collagen gel system to mimic the natural microenvironment. We successfully established adipogenic differentiation of hBMSC embedded in type I collagen gels. We found that exogenous FGF1 and FGF2 exerted an inhibitory effect on lipid droplet accumulation and gene expression of adipogenic markers, which was abolished by pharmacological blocking of FGF receptor (FGFR) signaling. FGF treatment also affected the expression of the matrix metalloproteinase 13 (MMP13) and the tissue inhibitor of metalloproteinases 1 (TIMP1), altering the MMP/TIMP balance, which modulates collagen processing and turnover. FGF1- and FGF2-mediated inhibition of differentiation was, however, not restricted to adipogenesis since FGF1 and FGF2 treatment also resulted in the inhibition of the osteogenic differentiation in collagen gels. We conclude that FGFR signaling inhibits the in vitro adipogenic commitment of hBMSCs, downregulating core differentiation markers and altering ECM composition.

Probing label-free intracellular quantification of free peptide by MALDI-ToF mass spectrometry

Cell-penetrating peptides are promising reagents for gene and drug delivery. They can efficiently traverse the plasma membrane and deliver various cargo materials ranging from genes to nanoparticles. The functional efficiency of cargo often depends on the completeness of intracellular peptide uptake, which can be measured, but its quantification remains largely inconclusive. Existing approaches rely on the use of radioactive and fluorescent labels or tags which allow colorimetric, fluorescent or spectrometric detection, but lack the ability to detect free peptide. Herein we describe a generic label- and tag-free method to measure the concentration of internalised peptide by matrix-assisted laser desorption/ionisation time of flight mass spectrometry. Quantification is preceded by two-dimensional chromatography and is performed at benign temperatures for the lysates of human dermal fibroblasts transfected with cell penetrating peptides in free form. Isotopically labelled peptides of the same structure are used as internal standards to enable accurate determination of concentration of the recovered free peptide. The method offers a minimalistic approach for intracellular quantification, which can be used as a correlative measure for fluorescence-based imaging methods.

A review comparing deoxyribonucleoside triphosphate (dNTP) concentrations in the mitochondrial and cytoplasmic compartments of normal and transformed cells

The deoxyribonucleoside triphosphate (dNTP) pools that support the replication of mitochondrial DNA are physically separated from the rest of the cell by the double membrane of the mitochondria. Perturbed homeostasis of mitochondrial dNTP pools is associated with a set of severe diseases collectively termed mitochondrial DNA depletion syndromes. The degree of interaction of the mitochondrial dNTP pools with the corresponding dNTP pools in the cytoplasm is currently not clear. We reviewed the literature on previously reported simultaneous measurements of mitochondrial and cytoplasmic deoxyribonucleoside triphosphate pools to investigate and quantify the extent of the influence of the cytoplasmic nucleotide metabolism on mitochondrial dNTP pools. We converted the reported measurements to concentrations creating a catalog of paired mitochondrial and cytoplasmic dNTP concentration measurements. Over experiments from multiple laboratories, dNTP concentrations in the mitochondria are highly correlated with dNTP concentrations in the cytoplasm in normal cells in culture (Pearson R = 0.79, p = 3 × 10(-7)) but not in transformed cells. For dTTP and dATP there was a strong linear relationship between the cytoplasmic and mitochondrial concentrations in normal cells. From this linear model we hypothesize that the salvage pathway within the mitochondrion is only capable of forming a concentration of approximately 2 μM of dTTP and dATP, and that higher concentrations require transport of deoxyribonucleotides from the cytoplasm.

Mesenchymal stromal cells, colony-forming unit fibroblasts, from bone marrow of untreated advanced breast and lung cancer patients suppress fibroblast colony formation from healthy marrow

We have shown that bone marrow (BM) from untreated advanced lung and breast cancer patients (LCP and BCP) have a reduced number of colony-forming unit fibroblasts (CFU-Fs) or mesenchymal stem cells (MSCs). Factors that regulate the proliferation and differentiation of CFU-F are produced by the patients' BM microenvironment. We have now examined whether conditioned media (CM) from patients' CFU-F-derived stromal cells also inhibits the colony-forming efficiency (CFE) of CFU-F in primary cultures from healthy volunteers (HV)-BM. Thus the number and proliferation potential of HV-CFU-F were also found to be decreased and similar to colony numbers and colony size of patients' CFU-F. Stromal cells from both of these types of colonies appeared relatively larger and lacked the characteristic spindle morphology typically seen in healthy stromal cells. We developed an arbitrary mesenchymal stromal cell maturational index by taking three measures consisting of stromal cell surface area, longitudinal and horizontal axis. All stromal indices derived from HV-CFU-F grown in patients' CM were similar to those from stromal elements derived from patients' CFU-F. These indices were markedly higher than stromal indices typical of HV-CFU-F cultured in healthy CM or standard medium [alpha-medium plus 20% heat-inactivated fetal bovine serum (FBS)]. Patients' CM had increased concentrations of the CFU-F inhibitor, GM-CSF, and low levels of bFGF and Dkk-1, strong promoters of self-renewal of MSCs, compared to the levels quantified in CM from HV-CFU-F. Moreover, the majority of patients' MSCs were unresponsive in standard medium and healthy CM to give CFU-F, indicating that the majority of mesenchymal stromal cells from patients' CFU-F are locked in maturational arrest. These results show that alterations of GM-CSF, bFGF, and Dkk-1 are associated with deficient cloning and maturation arrest of CFU-F. Defective autocrine and paracrine mechanisms may be involved in the BM microenvironments of LCP and BCP.

Essential role of Tip60-dependent recruitment of ribonucleotide reductase at DNA damage sites in DNA repair during G1 phase

A balanced deoxyribonucleotide (dNTP) supply is essential for DNA repair. Here, we found that ribonucleotide reductase (RNR) subunits RRM1 and RRM2 accumulated very rapidly at damage sites. RRM1 bound physically to Tip60. Chromatin immunoprecipitation analyses of cells with an I-SceI cassette revealed that RRM1 bound to a damage site in a Tip60-dependent manner. Active RRM1 mutants lacking Tip60 binding failed to rescue an impaired DNA repair in RRM1-depleted G1-phase cells. Inhibition of RNR recruitment by an RRM1 C-terminal fragment sensitized cells to DNA damage. We propose that Tip60-dependent recruitment of RNR plays an essential role in dNTP supply for DNA repair.

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

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

Regulation of mammalian ribonucleotide reduction and dNTP pools after DNA damage and in resting cells

Ribonucleotide reductase (RNR) provides the cell with a balanced supply of deoxyribonucleoside triphosphates (dNTP) for DNA synthesis. In budding yeast DNA damage leads to an up-regulation of RNR activity and an increase in dNTP pools, which are essential for survival. Mammalian cells contain three non-identical subunits of RNR; that is, one homodimeric large subunit, R1, carrying the catalytic site and two variants of the homodimeric small subunit, R2 and the p53-inducible p53R2, each containing a tyrosyl free radical essential for catalysis. S-phase-specific DNA replication is supported by an RNR consisting of the R1 and R2 subunits. In contrast, DNA damage induces expression of the R1 and the p53R2 subunits. We now show that neither logarithmically growing nor G(o)/G1-synchronized mammalian cells show any major increase in their dNTP pools after DNA damage. However, non-dividing fibroblasts expressing the p53R2 protein, but not the R2 protein, have reduced dNTP levels if exposed to the RNR-specific inhibitor hydroxyurea, strongly indicating that there is ribonucleotide reduction in resting cells. The slow, 4-fold increase in p53R2 protein expression after DNA damage results in a less than 2-fold increase in the dNTP pools in G(o)/G1 cells, where the pools are about 5% that of the size of the pools in S-phase cells. Our results emphasize the importance of the low constitutive levels of p53R2 in mammalian cells, which together with low levels of R1 protein may be essential for the supply of dNTPs for basal levels of DNA repair and mitochondrial DNA synthesis in G(o)/G1 cells.

Bioactive Thin Film of Acidic Fibroblast Growth Factor Fabricated by Layer-by-Layer Assembly

A new class of bioactive thin films using growth factors as building blocks has been fabricated via layer-by-layer assembly (LBL) technique. Acid fibroblast growth factor (aFGF) in the presence of heparin was used as negatively charged polyelectrolytes, while poly(ethyleneimine) (PEI) was chosen as a positively charged counterpart. The self-deposition process and surface morphology of the resultant multilayers were monitored and detected by UV-vis absorbance spectra, advanced contact angle measurements, and scanning force microscopy (SFM) observations. Cell culture was performed to assess the efficiency of the growth factors. The fibroblasts proliferated faster on the surface assembled with five bilayers of (aFGF/heparin)/PEI with apparent higher cytoviability than on those surfaces modified by one bilayer of (aFGF/heparin)/PEI, five bilayers of aFGF/PEI, or five bilayers of heparin/PEI, and tissue culture polystyrene. Enhanced secretion of collagen type I and interleukin 6 (IL-6) by the fibroblasts seeded on the five bilayers of (aFGF/heparin)/PEI was also verified by immunohistochemical examination. The bioactivity of the (aFGF/heparin)/PEI multilayers could be largely preserved when stored at -20 degrees C.

In vitro characterization of natural and synthetic dermal matrices cultured with human dermal fibroblasts

The ideal dermal matrix should be able to provide the right biological and physical environment to ensure homogenous cell and extracellular matrix (ECM) distribution, as well as the right size and morphology of the neo-tissue required. Four natural and synthetic 3D matrices were evaluated in vitro as dermal matrices, namely (1) equine collagen foam, TissuFleece, (2) acellular dermal replacement, Alloderm, (3) knitted poly(lactic-co-glycolic acid) (10:90)-poly(-caprolactone) (PLGA-PCL) mesh, (4) chitosan scaffold. Human dermal fibroblasts were cultured on the specimens over 3 weeks. Cell morphology, distribution and viability were assessed by electron microscopy, histology and confocal laser microscopy. Metabolic activity and DNA synthesis were analysed via MTS metabolic assay and [(3)H]-thymidine uptake, while ECM protein expression was determined by immunohistochemistry. TissuFleece, Alloderm and PLGA-PCL mesh supported cell attachment, proliferation and neo-tissue formation. However, TissuFleece contracted to 10% of the original size while Alloderm supported cell proliferation predominantly on the surface of the material. PLGA-PCL mesh promoted more homogenous cell distribution and tissue formation. Chitosan scaffolds did not support cell attachment and proliferation. These results demonstrated that physical characteristics including porosity and mechanical stability to withstand cell contraction forces are important in determining the success of a dermal matrix material.

Gene delivery of l-caldesmon protects cytoskeletal cell membrane integrity against adenovirus infection independently of myosin ATPase and actin assembly

The cytoskeleton is critical to the viral life cycle. Agents like cytochalasin inhibit viral infections but cannot be used for antiviral therapy because of their toxicity. We report the efficacy, safety, and mechanisms by which gene delivery of human wild-type low-molecular-weight caldesmon (l-CaD) protects cell membrane integrity from adenovirus infection in a DF-1 cell line, an immortalized avian fibroblast that is null for l-CaD. Transfection with an adenovirus (Ad)-controlled construct mediated a dose-dependent decline in transcellular resistance. In accordance with a computational model of cytoskeletal membrane properties, Ad disturbed cell-cell and cell-matrix adhesion and membrane capacitance. Transfection with the Ad-l-CaD construct attenuated adenovirus-mediated loss in transcellular resistance. Quantitation of vinculin-stained plaques revealed an increase in total focal contact mass in monolayers transfected with the Ad-l-CaD construct. Expression of l-CaD protected transcellular resistance through primary effects on membrane capacitance and independently of actin solubility and effects on prestress, as measured by the decline in isometric tension in response to cytochalasin D. Expression of l-CaD exhibited less Trypan blue cell toxicity than cytochalasin, and, unlike cytochalasin, it did not interfere with wound closure or adversely effect transcellular resistance. These findings demonstrate the gene delivery of wild-type human l-CaD as a potentially efficacious and safe agent that inhibits some of the cytopathic effects of adenovirus.

Growth factor profile of irradiated human dermal fibroblasts using a serum-free method

Radiation therapy for cancer permanently damages tissue in the line of treatment. This study sought to establish a serum-free protocol to evaluate the growth of irradiated fibroblasts and to analyze the levels of basic fibroblast growth factor (bFGF) and transforming growth factor-beta (TGF-beta) compared with normal fibroblasts. One irradiated cell line of human dermal fibroblasts was established from an intraoperative specimen obtained from a patient who had undergone radiation therapy for head and neck cancer. Irradiated and normal fibroblasts were then plated in UltraCULTURE (serum and growth factor free), modified Webber's medium (bFGF 50 ng/ml, insulin-like growth factor 100 ng/ml), and Dulbecco's Modified Eagle Medium with 10% fetal bovine serum (serum with undefined basal growth factors). Irradiated cells were also seeded in UltraCULTURE with 50 and 100 ng/ml of bFGF. Cell counts were performed at 0, 1, 3, 5, and 7 days, and cell supernatants were assayed for bFGF and TGF-beta. Irradiated and normal fibroblasts exhibited stronger growth in modified Webber's medium than in Dulbecco's Modified Eagle Medium with 10% fetal bovine serum. Growth of irradiated fibroblasts under bFGF modulation was similar to their growth in Webber's medium. Furthermore, irradiated fibroblasts remained viable in a serum-free and growth factor-free environment for at least 7 days; however, their growth and autocrine growth factor production was less than that of normal cells. This confirms the results of previous studies suggesting that cells from irradiated tissue undergo cellular changes. This study provides an effective model for the first-line evaluation of agents to improve wound healing, and it helps to establish standard levels of bFGF and TGF-beta production for irradiated fibroblasts.

The effects of basic fibroblast growth factor (bFGF) on the breaking strength of acute incisional wounds

Many researchers have reported the effects of cytokines on ulcers, especially on chronic ulcers. However, the long-term influences of cytokines on acute incisional wounds with respect to breaking strength, quality of the scar etc. have not been elucidated completely. In the present study, the breaking strength of scars produced by full thickness incisional wounds of the skin created on backs of rabbits were compared when the wounds were treated by conventional suturing or with basic fibroblast growth factor (bFGF) in addition to suturing. We administered bFGF to full thickness acute incisional wounds of the skin created on backs of rabbits. The breaking strengths of wounds treated by conventional suturing and those treated with bFGF soon after the operation were compared as were the conditions of the scars after long-term follow up of up to 7 weeks. They were also examined histopathologically. Administration of bFGF at the time of wound closure, especially 1.0 microg in amount per cm, increased the breaking strength significantly compared to the control group from 5 weeks after the operation. Moreover, histopathological examination revealed that there was rich vascularization soon after the operation and an arrangement of collagen fibers which lenticulated horizontally from the 5th week and later after the operation in the bFGF treated groups in a dose dependent manner. This study demonstrates that administration of bFGF at the time of wound closure significantly increased the breaking strength compared to the control group from 5 weeks after the operation. And the administration of bFGF also improved the quality of the scar, the condition of the scar by surface condition by inspection as well as the width of scar at histological evaluations. So we think this cytokine may be highly effective clinically. This may be especially true for patients whose wound healing process tends to be delayed such as aged patients or when high breaking strength is recommended even for patients with normal wound healing potential.

THE PIG AS A MODEL FOR HUMAN WOUND HEALING

The medical literature describes numerous in vitro and in vivo wound-healing models. The selection of an animal model depends on a number of factors including availability, cost, ease of handling, investigator familiarity, and anatomical/functional similarity to humans. Small mammals are frequently used for wound healing studies, however, these mammals differ from humans in a number of anatomical and physiological ways. Anatomically and physiologically, pig skin is more similar to human skin. The many similarities between man and pig would lead one to believe that the pig should make an excellent animal model for human wound healing. The purpose of this paper is to review the existing literature for evidence of this supposition and determine how well the various models correlate to human wound healing. Studies of wound dressings, topical antimicrobials, and growth factors are examined. Over 180 articles were utilized for this comparative review. Our conclusion is that the porcine model is an excellent tool for the evaluation of therapeutic agents destined for use in human wounds.

bFGF induces differentiation and death of olfactory neuroblastoma cells

Olfactory neuroblastoma (ONB) is a highly vascularized and malignant tumor arising in olfactory neuronal precursors from the paranasal sinuses. Previously, we showed that treatment of JFEN cells with transforming growth factor (TGF)-alpha caused them to differentiate and respond to chemical odorants, whereas basic fibroblast growth factor (bFGF) treated cells differentiated and died. In the present study we show that established ONB tumors treated with bFGF upregulate the bFGF receptor (FGFR1) prior to differentiation. This cellular differentiation was evidenced by bFGF-induced expression of the human runt homologue AML1 (PEBP2 alpha B, CBFA-2) that is highly expressed in developing olfactory neuroepithelium and TrkA, a preferred nerve growth factor receptor. Since TrkA is expressed in supporting cells, but not in mature olfactory neurons, we hypothesize that the expression of AML1 and TrkA in bFGF-treated JFEN cells induced supporting cell differentiation. Collectively, these results have implications for the treatment of patients afflicted with ONB.

Effects of a collagen matrix containing basic fibroblast growth factor on wound contraction

We evaluated the effectiveness of basic fibroblast growth factor (bFGF) in inhibiting wound contraction, both alone and in combination with collagen matrix, using a simulated in vivo delayed healing type model. We also studied the mechanisms involved in this inhibition in in vitro experiments using fibroblast populated collagen gels. As a result, we were able to demonstrate that both collagen matrix and bFGF significantly inhibited wound contraction; especially, bFGF acted in a dose-dependent fashion. Interestingly, their combination was much more effective than either collagen matrix or bFGF alone, a finding that was supported by the histopathological data. Wounds treated with collagen matrix, but not control wounds, showed horizontal rearrangement of collagen fibers in dermis as well as evidence of fibroblast proliferation, which was not observed in scar regions surrounded by normal dermis. Using fibroblast-populated collagen gel contraction as an in vitro model, we found that bFGF significantly inhibited contraction. Taking all these results together, it was concluded that collagen matrix is useful not only as a carrier of cytokines such as bFGF, but also for the quick closure of chronic wounds, thereby preventing contracture, which remains one of the most challenging problems in treating this type of wound. Application of bFGF-treated collagen matrix to chronic wounds such as decubitus, and diabetic and leg ulcers may prove to be highly beneficial in clinical practice.

Mast cells and their mediators in cutaneous wound healing--active participants or innocent bystanders?

Mast cells are traditionally viewed as effector cells of immediate type hypersensitivity reactions. There is, however, a growing body of evidence that the cells might play an important role in the maintenance of tissue homeostasis and repair. We here present our own data and those from the literature elucidating the possible role of mast cells during wound healing. Studies on the fate of mast cells in scars of varying ages suggest that these cells degranulate during wounding, with a marked decrease of chymase-positive cells, although the total number of cells does not decrease, based on SCF-receptor staining. Mast cells contain a plethora of preformed mediators like heparin, histamine, tryptase, chymase, VEGF and TNF-alpha which, on release during the initial stages of wound healing, affect bleeding and subsequent coagulation and acute inflammation. Various additional vasoactive and chemotactic, rapidly generated mediators (C3a, C5a, LTB4, LTC4, PAF) will contribute to these processes, whereas mast cell-derived proinflammatory and growth promoting peptide mediators (VEGF, FGF-2, PDGF, TGF-beta, NGF, IL-4, IL-8) contribute to neoangiogenesis, fibrinogenesis or re-epithelization during the repair process. The increasing number of tryptase-positive mast cells in older scars suggest that these cells continue to be exposed to specific chemotactic, growth- and differentiation-promoting factors throughout the process of tissue remodelling. All these data indicate that mast cells contribute in a major way to wound healing. their role as potential initiators of or as contributors to this process, compared to other cell types, will however have to be further elucidated.

Basic fibroblast growth factor induces apoptosis in myofibroblastic cells isolated from rat palatal mucosa

The effect of basic fibroblast growth factor (bFGF) on apoptosis in normal rat palatal fibroblasts and rat palatal scar fibroblasts was examined by the TUNEL method in order to clarify the mechanism of apoptosis induction in myofibroblasts during the scar formation process. A percentage of scar fibroblasts undergoing apoptosis was significantly higher than that of palatal fibroblasts when they were treated with bFGF succeeding to serum starvation. Palatal fibroblasts, phenotypically modulated into myofibroblasts by the pretreatment with transforming growth factor-beta 1 (TGF-beta 1), similarly showed a higher level of apoptosis induction by bFGF-treatment. TGF-beta 1 elevated protein and mRNA level of FGF receptor (FGFR) in palatal fibroblasts. Tyrosine autophosphorylation of FGFR upon stimulation by bFGF was significantly higher in scar fibroblasts than in normal palatal fibroblasts. These findings suggested that bFGF may be a potential stimulator of apoptosis in myofibroblasts during palatal scar formation and that FGFR may be responsible for this process.

Heparin induces fibroblast proliferation, cell-matrix interaction and epidermal growth inhibition

We have examined the effect of heparin on fibroblasts cultivated in monolayer or in a 3-dimensional culture system: the so-called collagen lattices. Thereafter, we have investigated the effect of heparin on the kinetics of epidermal growth on the collagen lattices. In monolayer culture, heparin stimulated the fibroblast growth with an optimal response at 0.01 mg/ml. The volume of treated fibroblasts was smaller than that of untreated controls. In the collagen lattices, heparin stimulated the fibroblast growth with an optimal response at 0.1 mg/ml. The volume of treated fibroblasts was greater than that of untreated controls, the opposite to the result observed in monolayer culture. The beginning of the contraction of the collagen lattices was inhibited by heparin. Heparin inhibited epidermal growth on the immersion as well as on the emersion collagen lattices. These effects of heparin should be the consequences of heparin-induced modifications of cell-matrix interactions.