Novel missense mutations affecting the structure of the conserved fibrinogen Bß C-terminal domain cause congenital hypofibrinogenemia.

This study describes the identification of two new mutations of the fibrinogen beta-chain in patients with inherited fibrinogen deficiency. Modelling of the impact of the mutations predict that these single amino acid substitutions are sufficient to abolish secretion of the mutant chains into the circulation, resulting in low fibrinogen levels in the patients. In addition, whole exome sequencing identified genetic modifiers for both patients which could contribute to the patients' global hemostatic function. Our results yield clinically relevant information for the personalised management of patients and eventually precision medicine for fibrinogen disorders.

Chemical Modulators of Fibrinogen Production and Their Impact on Venous Thrombosis.

Thrombosis is a leading cause of morbidity and mortality. Fibrinogen, the soluble substrate for fibrin-based clotting, has a central role in haemostasis and thrombosis and its plasma concentration correlates with cardiovascular disease event risk and a prothrombotic state in experimental models. We aimed to identify chemical entities capable of changing fibrinogen production and test their impact on experimental thrombosis. A total of 1,280 bioactive compounds were screened for their ability to alter fibrinogen production by hepatocyte-derived cancer cells and a selected panel was tested in zebrafish larvae. Anthralin and all-trans retinoic acid (RA) were identified as fibrinogen-lowering and fibrinogen-increasing moieties, respectively. In zebrafish larvae, anthralin prolonged laser-induced venous- occlusion times and reduced thrombocyte accumulation at injury sites. RA had opposite effects. Treatment with RA, a nuclear receptor ligand, increased fibrinogen mRNA levels. Using an antisense morpholino oligonucleotide to deplete zebrafish fibrinogen, we correlated a shortening of laser-induced venous thrombosis times with RA treatment and fibrinogen protein levels. Anthralin had little effect on fibrinogen mRNA in zebrafish larvae, despite leading to lower detectable fibrinogen. Therefore, we made a proteomic scan of anthralin-treated cells and larvae. A reduced representation of proteins linked to the canonical secretory pathway was detected, suggesting that anthralin affects protein secretion. In summary, we found that chemical modulation of fibrinogen levels correlates with measured effects on experimental venous thrombosis and could be investigated as a therapeutic avenue for thrombosis prevention.

Afibrinogenemia caused by a novel homozygous missense mutation, FGB p.Cys241Tyr, in a male patient with recurrent intracranial bleeding: case report and review of literature.

INTRODUCTION: Congenital afibrinogenemia is a severe bleeding disorder, sometimes manifesting as thrombosis and/or pregnancy complications. Intracranial haemorrhage (ICH) constitutes the major cause of death in this disease. METHODS: We present the case of a male patient with congenital afibrinogenemia, who presented with recurrent intracranial hemorrhages, despite prophylactic fibrinogen substitution. We also review the literature for the risk of intracranial hemorrhages in afibrinogenemia. RESULT: Molecular analysis revealed a novel homozygous missense mutation in FGB exon 5, p.Cys241 Tyr, that was named "Fibrinogen Krakow V". DISCUSSION AND CONCLUSION: Intracranial hemorrhage is a severe manifestation of afibrinogenemia, also in children. The clinical presentation of afibrinogenemia is variable. Fibrinogen substitution carries a risk of thrombotic complications.

Fibrin clot properties to assess the bleeding phenotype in unrelated patients with hypodysfibrinogenemia due to novel fibrinogen mutations.

Congenital hypodysfibrinogenemia is a rare fibrinogen disorder, defined by decreased levels of a dysfunctional fibrinogen. We present the functional and structural characterization of two new fibrinogen variants. A duplication of 32 bases in FGA exon 5, p.Ser382GlyfsTer50 was identified in a patient (P1) with history of hemoptysis and traumatic cerebral bleeding. A missense mutation in FGG exon 8, p.Ala353Ser was identified in two siblings (P2 and P3) with tendency to bruising and menorrhagia. Fibrin polymerization was studied in plasma and in purified fibrinogen by turbidimetry. Fibrin structure was studied by a permeability assay, laser scanning confocal microscopy (LSCM) and scanning electron microscopy (SEM). In both plasma and purified fibrinogen samples, all patients had an abnormal polymerization characterized by a decreased maximal absorption compared to controls. The permeation constant (Ks) was markedly increased in all patients: 31 ± 9 × 10-9 cm2 in P1, and 20 ± 0.1 × 10-9 cm2 in P2 and P3, compared to 6 ± 2 × 10-9 cm2 in the control (p < 0.05). The presence of very large pores that accounts for the increased Ks was confirmed by LSCM and SEM patients' clots images. By SEM, the patients' fibrin fibers diameters were thicker: 90 ± 25 nm in P1, 162 ± 64 nm in P2 and 132 ± 46 nm in P3 compared to 74 ± 25 nm in control (p < 0.0001). In conclusion, both new causative fibrinogen mutations altered clot structure by forming thick fibers, diminishing fiber branching, and increasing pore filling space. These structural changes to clots explain the patients' bleeding phenotypes.

A Novel Nonsense Mutation in FGB (c.1421G>A; p.Trp474Ter) in the Beta Chain of Fibrinogen Causing Hypofibrinogenemia with Bleeding Phenotype.

Congenital hypofibrinogenemia is a rare bleeding disorder characterized by a proportional decrease of functional and antigenic fibrinogen levels. Hypofibrinogenemia can be considered the phenotypic expression of heterozygous loss of function mutations occurring within one of the three fibrinogen genes (FGA, FGB, and FGG). Clinical manifestations are highly variable; most patients are usually asymptomatic, but may appear with mild to severe bleeding or thrombotic complications. We have sequenced all exons of the FGA, FGB, and FGG genes using the DNA isolated from the peripheral blood in two unrelated probands with mild hypofibrinogenemia. Coagulation screening, global hemostasis, and functional analysis tests were performed. Molecular modeling was used to predict the defect of synthesis and structural changes of the identified mutation. DNA sequencing revealed a novel heterozygous variant c.1421G>A in exon 8 of the FGB gene encoding a Bß chain (p.Trp474Ter) in both patients. Clinical data from patients showed bleeding episodes. Protein modelling confirmed changes in the secondary structure of the molecule, with the loss of three ß sheet arrangements. As expected by the low fibrinogen levels, turbidity analyses showed a reduced fibrin polymerisation and imaging difference in thickness fibrin fibers. We have to emphasize that our patients have a quantitative fibrinogen disorder; therefore, the reduced function is due to the reduced concentration of fibrinogen, since the Bß chains carrying the mutation predicted to be retained inside the cell. The study of fibrinogen molecules using protein modelling may help us to understand causality and effect of novel genetic mutations.

A genetic modifier of venous thrombosis in zebrafish reveals a functional role for fibrinogen AαE in early hemostasis.

Plasma fibrinogen molecules comprise 2 copies of Aα, Bß, and γ chains folded into a hexameric protein. A minor fibrinogen isoform with an extended Aα chain (AαE) is more abundant in newborn human blood than in adults. Larval zebrafish produce predominantly AαE-containing fibrinogen, but its functional significance is unclear. In 3-day-old zebrafish, when hemostasis is reliant on fibrinogen and erythrocyte-rich clotting but is largely thrombocyte-independent, we measured the time to occlusion (TTO) in a laser-induced venous thrombosis assay in 3 zebrafish strains (AB, TU, and AB × TL hybrids). AB larvae showed delayed TTO compared with the TU and AB × TL strains. Mating AB with TU or TL produced larvae with a TU-like TTO. In contrast to TU, AB larvae failed to produce fibrinogen AαE, due to a mutation in the AαE-specific coding region of fibrinogen α-chain gene (fga). We investigated whether the lack of AαE explained the delayed AB TTO. Transgenic expression of AαE, but not Aα, shortened the AB TTO to that of TU. AαE rescued venous occlusion in fibrinogen mutants or larvae with morpholino-targeted fibrinogen α-chain messenger RNA, but Aα was less effective. In 5-day-old larvae, circulating thrombocytes contribute to hemostasis, as visualized in Tg(itga2b:EGFP) transgenics. Laser-induced venous thrombocyte adhesion and aggregation is reduced in fibrinogen mutants, but transgenic expression of Aα or AαE restored similar thrombocyte accumulation at the injury site. Our data demonstrate a genetic modifier of venous thrombosis and a role for fibrinogen AαE in early developmental blood coagulation, and suggest a link between differentially expressed fibrinogen isoforms and the cell types available for clotting.

Fibrin(ogen) in human disease: both friend and foe.

Fibrinogen is an abundant protein synthesized in the liver, present in human blood plasma at concentrations ranging from 1.5-4 g/L in healthy individuals with a normal half-life of 3-5 days. With fibrin, produced by thrombin-mediated cleavage, fibrinogen plays important roles in many physiological processes. Indeed, the formation of a stable blood clot, containing polymerized and cross-linked fibrin, is crucial to prevent blood loss and drive wound healing upon vascular injury. A balance between clotting, notably the conversion of fibrinogen to fibrin, and fibrinolysis, the proteolytic degradation of the fibrin mesh, is essential. Disruption of this equilibrium can cause disease in distinct manners. While some pathological conditions are the consequence of altered levels of fibrinogen, others are related to structural properties of the molecule. The source of fibrinogen expression and the localization of fibrin(ogen) protein also have clinical implications. Low levels of fibrinogen expression have been detected in extra-hepatic tissues, including carcinomas, potentially contributing to disease. Fibrin(ogen) deposits at aberrant sites including the central nervous system or kidney, can also be pathological. In this review, we discuss disorders in which fibrinogen and fibrin are implicated, highlighting mechanisms that may contribute to disease.

Influence of Femtosecond Laser Surface Nanotexturing on the Friction Behavior of Silicon Sliding Against PTFE.

The aim of the present work was to investigate the influence of laser-induced periodic surface structures (LIPSS) produced by femtosecond laser on the friction behavior of silicon sliding on polytetrafluoroethylene (PTFE) in unlubricated conditions. Tribological tests were performed on polished and textured samples in air using a ball-on-flat nanotribometer, in order to evaluate the friction coefficient of polished and textured silicon samples, parallel and perpendicularly to the LIPSS orientation. In the polished specimens, the friction coefficient decreases with testing time at 5 mN, while it increases slightly at 25 mN. It also decreases with increasing applied load. For the textured specimens, the friction coefficient tends to decrease with testing time in both sliding directions studied. In the parallel sliding direction, the friction coefficient decreases with increasing load, attaining values similar to those measured for the polished specimen, while it is independent of the applied load in the perpendicular sliding direction, exhibiting values lower than in the two other cases. These results can be explained by variations in the main contributions to friction and in the wear mechanisms. The influence of the temperature increase at the interface and the consequent changes in the crystalline phases of PTFE are also considered.

Structural modifications induced in dentin by femtosecond laser.

The structural and chemical modifications induced in dentin by ultrafast laser ablation were studied. The laser experiments were performed with a Yb:KYW chirped-pulse-regenerative amplification laser system (560-fs pulse duration, 1030-nm radiation wavelength), fluences in the range 2 to 14 ?? J / cm 2 , 1-kHz pulse repetition rate, and 5 - mm / s scanning speed. The ablation surfaces were characterized by scanning electron microscopy and Fourier transform infrared spectroscopy. The ablation surfaces produced with 2 ?? J / cm 2 presented an irregular morphology with exposed dentinal tubules and no evidence of thermal effects. For 7 and 14 ?? J / cm 2 , the ablation surfaces were covered by a layer of redeposited ablation debris, consisting mainly of amorphous calcium phosphate. This layer is weakly adherent to the underlying tissue and can be easily removed by ultrasonication, revealing a surface with a morphology similar to the one obtained with 2 ?? J / cm 2 . The constitution of the dentin ablation surfaces is similar to the constitution of pristine dentin, showing that, within this fluence range, the laser treatment does not significantly modify the structure and constitution of dentin. The results achieved suggest an ablation mechanism where collagen is preferentially decomposed by the laser radiation, reducing the tissue cohesive strength and leading, ultimately, to its ablation.

Femtosecond laser ablation of enamel.

The surface topographical, compositional, and structural modifications induced in human enamel by femtosecond laser ablation is studied. The laser treatments were performed using a Yb:KYW chirped-pulse-regenerative amplification laser system (560 fs and 1030 nm) and fluences up to 14 J/cm2. The ablation surfaces were studied by scanning electron microscopy, grazing incidence x-ray diffraction, and micro-Raman spectroscopy. Regardless of the fluence, the ablation surfaces were covered by a layer of resolidified material, indicating that ablation is accompanied by melting of hydroxyapatite. This layer presented pores and exploded gas bubbles, created by the release of gaseous decomposition products of hydroxyapatite (CO2 and H2O) within the liquid phase. In the specimen treated with 1-kHz repetition frequency and 14 J/cm2, thickness of the resolidified material is in the range of 300 to 900 nm. The micro-Raman analysis revealed that the resolidified material contains amorphous calcium phosphate, while grazing incidence x-ray diffraction analysis allowed detecting traces of a calcium phosphate other than hydroxyapatite, probably ß-tricalcium phosphate Ca3(PO4)2, at the surface of this specimen. The present results show that the ablation of enamel involves melting of enamel's hydroxyapatite, but the thickness of the altered layer is very small and thermal damage of the remaining material is negligible.

Human mesenchymal stem cell behavior on femtosecond laser-textured Ti-6Al-4V surfaces.

AIM: The aim of the present work was to investigate ultrafast laser surface texturing as a surface treatment of Ti-6Al-4V alloy dental and orthopedic implants to improve osteoblastic commitment of human mesenchymal stem cells (hMSCs). MATERIALS & METHODS: Surface texturing was carried out by direct writing with an Yb:KYW chirped-pulse regenerative amplification laser system with a central wavelength of 1030 nm and a pulse duration of 500 fs. The surface topography and chemical composition were investigated by scanning electron microscopy and x-ray photoelectron spectroscopy, respectively. Three types of surface textures with potential interest to improve implant osseointegration can be produced by this method: laser-induced periodic surface structures (LIPSSs); nanopillars (NPs); and microcolumns covered with LIPSSs, forming a bimodal roughness distribution. The potential of the laser treatment in improving hMSC differentiation was assessed by in vitro study of hMSCs spreading, adhesion, elongation and differentiation using epifluorescence microscopy at different times after cell seeding, after specific stainings and immunostainings. RESULTS: Cell area and focal adhesion area were lower on the laser-textured surfaces than on a polished reference surface. Obviously, the laser-textured surfaces have an impact on cell shape. Osteoblastic commitment was observed independently of the surface topography after 2 weeks of cell seeding. When the cells were cultured (after 4 weeks of seeding) in osteogenic medium, LIPSS- and NP- textured surfaces enhanced matrix mineralization and bone-like nodule formation as compared with polished and microcolumn-textured surfaces. CONCLUSION: The present work shows that surface nanotextures consisting of LIPSSs and NPs can, potentially, improve hMSC differentiation into an osteoblastic lineage.

Transformations induced in bulk amorphous silica by ultrafast laser direct writing.

A transmission electron microscopy study of nanogratings formed in bulk amorphous silica by direct writing with an ultrafast pulsed laser with a radiation wavelength of 1030 nm and pulse duration of 560 fs is presented. The results achieved show that the nanogratings are composed of planar nanostructures with an average periodicity of 250 nm and typical thickness of about 30 nm, consisting of alternating layers of heavily damaged material and layers of material where a dense precipitation of nanocrystals occurred. The crystallization of silica to form these nanocrystals can be explained by the large pressures and temperatures reached in these regions as a result of nanoplasma formation and recombination.

Femtosecond laser ablation of bovine cortical bone.

We study the surface topographical, structural, and compositional modifications induced in bovine cortical bone by femtosecond laser ablation. The tests are performed in air, with a Yb:KYW chirped-pulse-regenerative amplification laser system (500 fs, 1030 nm) at fluences ranging from 0.55 to 2.24 J/cm2. The ablation process is monitored by acoustic emission measurements. The topography of the laser-treated surfaces is studied by scanning electron microscopy, and their constitution is characterized by glancing incidence x-ray diffraction, x-ray photoelectron spectroscopy, Fourier transform infrared spectroscopy, and micro-Raman spectroscopy. The results show that femtosecond laser ablation allows removing bone without melting, carbonization, or cracking. The structure and composition of the remaining tissue are essentially preserved, the only constitutional changes observed being a reduction of the organic material content and a partial recrystallization of hydroxyapatite in the most superficial region of samples. The results suggest that, within this fluence range, ablation occurs by a combination of thermal and electrostatic mechanisms, with the first type of mechanism predominating at lower fluences. The associated thermal effects explain the constitutional changes observed. We show that femtosecond lasers are a promising tool for delicate orthopaedic surgeries, where small amounts of bone must be cut with negligible damage, thus minimizing surgical trauma.

Colorimeter and scanning electron microscopy analysis of teeth submitted to internal bleaching.

INTRODUCTION: This in vitro study compared the tooth color and the ultrastructure of internal dental tissues before and after internal bleaching. METHODS: Sodium perborate was placed in the pulp chamber of endodontically treated molars and sealed with intermediate restorative material. The test samples were stored in a physiologic solution, and the bleaching agent was replaced every 7 days. A control group was used. After 1 month, the colors of the test and control samples were measured with a colorimeter, and the internal surfaces were observed under field emission scanning electron microscopy (FESEM). RESULTS: Statistically significant differences were found between the test and control sample colors. The FESEM ultrastructure analysis of the internal enamel and dentin surfaces did not show any changes after the internal bleaching. CONCLUSIONS: The results of the present study show that sodium perborate is effective in bleaching nonvital teeth and does not produce ultrastructural changes in the dental tissues.

Bond strength of an etch-and-rinse adhesive to KrF excimer laser-treated dentin.

OBJECTIVE: The aim of this work was to evaluate the effect of KrF excimer laser treatment on the bond strength between dentin and an etch-and-rinse adhesive system. MATERIALS AND METHODS: Polished dentin surfaces were subjected to the following treatments: (1) 35% phosphoric acid etching for 15 s; (2) laser surface treatment using KrF excimer laser radiation (1 J/cm(2)); and (3) laser treatment under the same conditions followed by acid etching. After treating the dentin, an etch-and-rinse adhesive (Adper Scotchbond 1 XT, 3M ESPE) was applied and composite (Esthet-X, Dentsply Caulk, Konstanz, Germany) build-ups were incrementally constructed. After 24 h of water storage at 37 degrees C, 1 mm(2) beams were longitudinally cut from the samples. Microtensile sticks were loaded in tension at a crosshead speed of 0.5 mm/min. Bond strength data were analyzed with one-way ANOVA and the Student-Newman-Keuls test (p < 0.05). The dentin surfaces resulting from each surface treatment and the fracture surfaces originated by the bond-strength tests were observed under a scanning electron microscope. RESULTS: Laser-treated surfaces exhibited a cone-shaped topography with a frank occlusion of dentinal tubules, while acid etching produced a smoother surface with open tubules. Application of 35% phosphoric acid on laser-treated dentin surfaces resulted in the partial dissolution of the surface cones. Mean microtensile bond strengths for acid-etched dentin was significantly higher (33.7 +/- 8.7 MPa) than for laser-treated (13.8 +/- 5.1 MPa) and laser-treated and etched surfaces (19.7 +/- 6.9 MPa). A higher percentage of cohesive failures at the base of the cones occurred in the laser-treated group, whereas mixed failures were predominant on acid-etched samples. CONCLUSION: The cone-shaped texture produced by treating dentin with KrF laser radiation does not improve the bond strength of the tested etch-and rinse adhesive system when compared to the traditional acid-etching technique.

On the structural diversity of sialoliths.

Sialoliths from parotid and submaxillar glands have been characterized. Fractured and polished surfaces revealed an intrinsic structural diversity across the calculi sections. In general, the calculi presented highly mineralized amorphous-looking cores surrounded by concentric alternating mineralized and organic layers. The thickness of these layers decreased from the outer regions toward the center of the sialolith, illustrating a sequence of growth stages. Nevertheless, a significant variability could be detected among the specimens. In some cases, the calculi displayed multiple cores and lacked concentric laminated structures. In other instances, the specimens exhibited extensive regions of globular structures. In these cases, the globule diameter decreased across the radius toward the center of the sialoliths, and the globular structures tended to reorganize, forming bright and dark laminated layers surrounding the core. The participation of globular structures in the layer formation process points to morphogenetic mechanisms not previously described.

[Synovial fluid crystal identification by electron microscopy]. / Identificação de cristais no líquido sinovial por microscopia electrónica.

BACKGROUND: In clinical practice crystal identification in synovial fluid is made by polarized light microscopy and with some specific stainings. Nevertheless, sometimes we are unable to identify crystals by these means, either because they are too small or because they are widespread on the fluid. AIMS: To compare the identification of crystals in synovial fluid from patients with non-infectious monoarthritis but no history of local trauma or articular disease, using polarized light and electronic microscopy. METHODS: We analized synovial fluid samples from patients with non-infectious monoarthritis and no history of local trauma or articular disease. First we used a polarized light microscope and alizarin red staining. Later we used conventional transmission electron microscopy and energy dispersive spectroscopy, in order to identify and characterize crystals. RESULTS: Fourty-five samples from 23 synovial fluids were analyzed. Under polarized light microscopy we identified crystals on 11 samples: 3 with calcium pyrophosphate crystals, 6 with calcium basic phosphate crystals and 2 with sodium monourate crystals. On the remaining 12 samples we were unable to identify crystals. Samples were then analyzed by conventional transmission electron microscopy and energy dispersive spectroscopy confirming the presence of the previously identified crystals. On the remainig 12 samples we were able to identify calcium basic phosphate crystals. DISCUSSION: Microcrystals seem to be an universal finding in synovial fluid of patients with osteoarthritis. The prevention of their deposition in joints might contribute to stop joint damage in this disease.

Characterisation of dentin surfaces processed with KrF excimer laser radiation.

In the present work, the surface microtexture and chemical changes induced in human dentin by laser processing with KrF excimer laser radiation using fluences ranging from 0.5 to 20 J/cm2 were studied by SEM, XPS and FTIR. Two distinct behaviours were observed in the evolution of surface topography. In some samples, the laser-treated surface remained flat, independently of the fluence used. It was covered by a layer formed of redeposited ablation particles, which occluded the dentinal apertures. In other samples the surface topography depended on radiation fluence. When the fluence was lower than 1 J/cm2, preferential removal of intertubular dentin occurs, producing a columnar structure in which the columns are essentially formed of peritubular material. If the fluence exceeded 1 J/cm2 the processed surface was flat and covered with resolidified material. Despite these topographic changes, the dentin was not significantly affected by the laser treatment. The observed behaviour can be explained by differences in the constitution of dentin.