The fibrillin microfibril/elastic fibre network: A critical extracellular supramolecular scaffold to balance skin homoeostasis.

Supramolecular networks composed of fibrillins (fibrillin-1 and fibrillin-2) and associated ligands form intricate cellular microenvironments which balance skin homoeostasis and direct remodelling. Fibrillins assemble into microfibrils which are not only indispensable for conferring elasticity to the skin, but also control the bioavailability of growth factors targeted to the extracellular matrix architecture. Fibrillin microfibrils (FMF) represent the core scaffolds for elastic fibre formation, and they also decorate the surface of elastic fibres and form independent networks. In normal dermis, elastic fibres are suspended in a three-dimensional basket-like lattice of FMF intersecting basement membranes at the dermal-epidermal junction and thus conferring pliability to the skin. The importance of FMF for skin homoeostasis is illustrated by the clinical features caused by mutations in the human fibrillin genes (FBN1, FBN2), summarized as "fibrillinopathies." In skin, fibrillin mutations result in phenotypes ranging from thick, stiff and fibrotic skin to thin, lax and hyperextensible skin. The most plausible explanation for this spectrum of phenotypic outcomes is that FMF regulate growth factor signalling essential for proper growth and homoeostasis of the skin. Here, we will give an overview about the current understanding of the underlying pathomechanisms leading to fibrillin-dependent fibrosis as well as forms of cutis laxa caused by mutational inactivation of FMF-associated ligands.

Effective Elimination and Biodegradation of Polycyclic Aromatic Hydrocarbons from Seawater through the Formation of Magnetic Microfibres.

Supramolecular aggregates formed between polycyclic aromatic hydrocarbons and either naphthalene or perylene-derived diimides have been anchored in magnetite magnetic nanoparticles. The high affinity and stability of these aggregates allow them to capture and confine these extremely carcinogenic contaminants in a reduced space. In some cases, the high cohesion of these aggregates leads to the formation of magnetic microfibres of several microns in length, which can be isolated from the solution by the direct action of a magnet. Here we show a practical application of bioremediation aimed at the environmental decontamination of naphthalene, a very profuse contaminant, based on the uptake, sequestration, and acceleration of the biodegradation of the formed supramolecular aggregate, by the direct action of a bacterium of the lineage Roseobacter (biocompatible with nanostructured receptors and very widespread in marine environments) without providing more toxicity to the environment.

The systemic influence of chronic smoking on skin structure and mechanical function.

One of the major functions of human skin is to provide protection from the environment. Although we cannot entirely avoid, for example, sun exposure, it is likely that exposure to other environmental factors could affect cutaneous function. A number of studies have identified smoking as one such factor that leads to both facial wrinkle formation and a decline in skin function. In addition to the direct physical effects of tobacco smoke on skin, its inhalation has additional profound systemic effects for the smoker. The adverse effects on the respiratory and cardiovascular systems from smoking are well known. Central to the pathological changes associated with smoking is the elastic fibre, a key component of the extracellular matrices of lungs. In this study we examined the systemic effect of chronic smoking (>40 cigarettes/day; >5 years) on the histology of the cutaneous elastic fibre system, the nanostructure and mechanics of one of its key components, the fibrillin-rich microfibril, and the micromechanical stiffness of the dermis and epidermis. We show that photoprotected skin of chronic smokers exhibits significant remodelling of the elastic fibre network (both elastin and fibrillin-rich microfibrils) as compared to the skin of age- and sex-matched non-smokers. This remodelling is not associated with increased gelatinase activity (as identified by in situ zymography). Histological remodelling is accompanied by significant ultrastructural changes to extracted fibrillin-rich microfibrils. Finally, using scanning acoustic microscopy, we demonstrated that chronic smoking significantly increases the stiffness of both the dermis and the epidermis. Taken together, these data suggest an unappreciated systemic effect of chronic inhalation of tobacco smoke on the cutaneous elastic fibre network. Such changes may in part underlie the skin wrinkling and loss of skin elasticity associated with smoking. © 2020 The Authors. The Journal of Pathology published by John Wiley & Sons Ltd on behalf of Pathological Society of Great Britain and Ireland.

Interleukin-4 Receptor α Signaling in Myeloid Cells Controls Collagen Fibril Assembly in Skin Repair.

Activation of the immune response during injury is a critical early event that determines whether the outcome of tissue restoration is regeneration or replacement of the damaged tissue with a scar. The mechanisms by which immune signals control these fundamentally different regenerative pathways are largely unknown. We have demonstrated that, during skin repair in mice, interleukin-4 receptor α (IL-4Rα)-dependent macrophage activation controlled collagen fibril assembly and that this process was important for effective repair while having adverse pro-fibrotic effects. We identified Relm-α as one important player in the pathway from IL-4Rα signaling in macrophages to the induction of lysyl hydroxylase 2 (LH2), an enzyme that directs persistent pro-fibrotic collagen cross-links, in fibroblasts. Notably, Relm-ß induced LH2 in human fibroblasts, and expression of both factors was increased in lipodermatosclerosis, a condition of excessive human skin fibrosis. Collectively, our findings provide mechanistic insights into the link between type 2 immunity and initiation of pro-fibrotic pathways.

Binding of MAGP2 to microfibrils is regulated by proprotein convertase cleavage.

MAGP2 is a small extracellular protein with both tumor angiogenesis and cell signaling activity. MAGP2 was originally isolated biochemically from microfibril-rich connective tissue. The localization of MAGP2 to microfibrils has been confirmed by both immunohistochemistry and immunogold electron microscopy. Whether MAGP2 binding to microfibrils is regulated post-translationally is still unclear, however, and a better understanding of this process would be instructive to understanding the angiogenesis and signaling functions ascribed to MAGP2. Here we show via immunofluorescence studies that the T3 cell line, derived from ovarian mouse tumor cells, produces abundant fibrillin-2 microfibrils to which MAGP2 can bind. Co-localization of MAGP2 and fibrillin-2 can be detected either when MAGP2 is overexpressed in, or exogenously introduced to, the cells. As expected, matrix association of MAGP2 required its conserved Matrix Binding Domain. Matrix association was positively regulated by proprotein convertase (PC) cleavage of MAGP2; mutation of the MAGP2 PC consensus site reduced the amount of matrix-associated MAGP2. Deletion analysis of the C-terminal 20-amino acid domain that is defined by the PC cleavage site suggests that this domain also positively modulates matrix localization of MAGP2, in a manner that requires the amino-terminal half of the protein. Together, our data indicate that matrix localization of MAGP2 by its Matrix Binding Domain is promoted by PC cleavage and the presence of its C-terminal 20 amino acids.

Epithelial-mesenchymal status influences how cells deposit fibrillin microfibrils.

Here, we show that epithelial-mesenchymal status influences how cells deposit extracellular matrix. Retinal pigmented epithelial (RPE) cells that expressed high levels of E-cadherin and had cell-cell junctions rich in zona occludens (ZO)-1, ß-catenin and heparan sulfate, required syndecan-4 but not fibronectin or protein kinase C α (PKCα) to assemble extracellular matrix (fibrillin microfibrils and perlecan). In contrast, RPE cells that strongly expressed mesenchymal smooth muscle α-actin but little ZO-1 or E-cadherin, required fibronectin (like fibroblasts) and PKCα, but not syndecan-4. Integrins α5ß1 and/or α8ß1 and actomyosin tension were common requirements for microfibril deposition, as was heparan sulfate biosynthesis. TGFß, which stimulates epithelial-mesenchymal transition, altered gene expression and overcame the dependency on syndecan-4 for microfibril deposition in epithelial RPE cells, whereas blocking cadherin interactions disrupted microfibril deposition. Renal podocytes had a transitional phenotype with pericellular ß-catenin but little ZO-1; they required syndecan-4 and fibronectin for efficient microfibril deposition. Thus, epithelial-mesenchymal status modulates microfibril deposition.

Nonselective assembly of fibrillin 1 and fibrillin 2 in the rodent ocular zonule and in cultured cells: implications for Marfan syndrome.

PURPOSE: Fibrillins are the major constituent of tissue microfibrils, which form the ocular zonule. In Marfan syndrome (MFS), FBN1 mutations lead to ectopia lentis. The goal of this work was to investigate zonule composition and formation in fibrillin-deficient and wild-type mice. METHODS: Immunofluorescence staining of eyes from wild-type, Fbn1-deficient, and Fbn2-deficient mice, as well as other species, was performed using monospecific fibrillin 1 and fibrillin 2 antibodies. The zonule of Fbn1-deficient and Fbn2-deficient mice was studied by electron microscopy. Microfibril formation in vitro was evaluated by immunofluorescence microscopy of cultured nonpigmented ciliary epithelial cells and fibroblasts. RESULTS: A zonule was present in both Fbn1-deficient and Fbn2-deficient mouse eyes. Immunofluorescence demonstrated that the zonule of Fbn1-deficient mice, wild-type mice, rats, and hamsters contained fibrillin 2. The zonule of Fbn2(-/-) mice contained fibrillin 1. Fibrillin 1 and fibrillin 2 colocalized in microfibrils formed in human nonpigmented ciliary epithelium cultures. Like fibrillin 1, fibrillin 2 microfibril assembly was fibronectin dependent and initiated by cell surface punctate deposits that elongated to form microfibrils. CONCLUSIONS: These data suggest that fibrillin 1 assembly and fibrillin 2 assembly share similar mechanisms. Microfibril composition depends substantially on the local levels of fibrillin isoforms and is not highly selective in regard to the isoform. This raises the intriguing possibility that the zonule could be strengthened in MFS by inducing fibrillin 2 expression in ciliary epithelium. The presence of fibrillin 2 in the murine zonule and an intact zonule in Fbn1-knockout mice may limit the utility of rodent models for studying ectopia lentis in MFS.

Versatile gas-phase reactions for surface to bulk esterification of cellulose microfibrils aerogels.

Aqueous suspensions of microfibrillated cellulose obtained by a high pressure homogenization process were freeze-dried after solvent exchange into tert-butanol. The resulting aerogels, which displayed a remarkable open morphology with a surface area reaching 100 m(2)/g, were subjected to a gas-phase esterification with palmitoyl chloride. Under these conditions, variations of the reaction temperature from 100 to 200 °C, of the reaction time from 0.5 to 2 h, and of the initial quantity of reagent, led to the preparation of a library of cellulose palmitates with DS varying from zero to 2.36. These products were characterized by gravimetry, FTIR, and (13)C solid-state NMR spectroscopy. Of special interest were the cellulose palmitate samples of low DS in the range of 0.1-0.4, which corresponded to hydrophobic cellulose microfibrils exclusively esterified at their surface while keeping intact their inner structure.

Pressure applied during surgery alters the biomechanical properties of human saphenous vein graft.

Pressure applied during harvesting of the saphenous vein (SV) graft in coronary artery bypass surgery might change its mechanical properties and thereby decrease the patency. This study was performed to assess the mechanical properties of the SV graft distended manually with different levels of pressure and to determine the pressure level that induces changes in its structure and mechanics. Saphenous vein graft segments, collected from 36 patients undergoing coronary artery bypass surgery, were distended with pressures of either 50-60, 75-100, or 130-150 mmHg. Grafts were tested for the stress-strain relationship; the Young's moduli at the low- and high-strain regions were calculated, and their structures were examined by light and electron microscopy. Pressures of 50-60 mmHg did not influence the mechanics of the vein graft, whereas pressures of 75-100 mmHg elevated the elastic modulus of the vein at the low-strain region while pressures above 130 mmHg increased the elastic moduli at both low- and high-strain regions. There was a prominent loss of microfibrils at all distending pressure levels. The mechanical results suggest that distending pressures above 75 mmHg might play a role in graft failure. Furthermore, the absence of microfibrils surrounding elastin suggests that application of distending pressures, even as low as 50 mmHg, can cause degeneration of the elastic fibers following implantation, increasing the stiffness of the graft and thus impairing the graft's function under its new hemodynamic conditions.

Fibrillary glomerulonephritis: a diagnosis not to be missed'.

Fibrillary glomerulonephritis (Fib GN) is among the newly recognized primary glomerular diseases. This rare cause of end-stage kidney disease has characteristic electron microscopic findings based upon the deposition of randomly distributed (18-22 nm) microfibrills in the mesangium and less frequently in the capillary basement membrane. The main differential diagnosis at the pathological level is amyloidosis; however, the apple green birefringence Congo red positivity of amyloid deposition is not seen in Fib GN. Clinically, the patient usually presents with proteinuria of nephrotic range, and the sine qua non for the diagnosis of Fib GN is the availability of high-magnification electron micrographs. Here is a case report of Fib GN with special emphasis on electron microscopy study and its role in the diagnosis.

The dual role of fibulins in tumorigenesis.

The human fibulin family consists of seven complex extracellular glycoproteins originally characterized as components of elastic fibers in connective tissue. However, beyond its structural role, fibulins are involved in complex biological processes such as cell adhesion, migration or proliferation. Indeed, they have proved to be essential elements in normal physiology, as shown by mouse models lacking these proteins, that evidence several developmental abnormalities and pathological features. Their relevance is also apparent in tumorigenesis, an aspect that has started to be intensely studied. Distinct fibulins are expressed in both tumor and stromal cells and are subjected to multiple expression regulations with either anti or pro-tumor effects. The mechanistic insights that underlie these observations are now commencing to emerge, portraying these proteins as very versatile and active constituents of connective tissue. The aim of this review is to highlight the most relevant connections between fibulins and cancer.

The microfibril-elastin fiber system distribution in left atrioventricular valve of the rat / Distribución del sistema de microfibrillas y fibras de elastina en la valva atrioventricular izquierda de la rata

The microfibril-elastin fiber system, an important constituent of the extracellular matrix, was studied in the rat left atrioventricular valve to investigate the interrelationship of oxytalan, elaunin and elastic fibers in left atrioventricular valve morphology. The elastin fibers forms continuous bundles observed along the length of the valve in atrial and ventricular layers and oriented parallel to endothelium. The elaunin and oxytalan fibers are distributed in the thickest fiber bundles along the length of the valve. The thinner fibers which radiated towards both the atrial and spongiosa layers, either as isolated or arborescent fiber bundles were identified as oxytalan fibers. With transmission electron microscopy elastic fibers were seen mainly in the atrial layer. The spongiosa layer was composed of elaunin and oxytalan fibers and ventricular layer showed elaunin fibers arranged in continuous bundles parallel to the endothelium. Both fibrillin and elastin were seen and identified by immunocytochemistry with colloidal gold in the left atrioventricular valve spongiosa and atrial layers. These observations allow us to suggest that the microfibril-elastin fiber system plays a role in the mechanical protection and maintenance of the integrity of the rat left atrioventricular valve.

Fue estudiado el sistema de fibras microfibrillas-elastina, un componente importante de la matriz extracelular, en la valva atrioventricular izquierda de rata, con la finalidad de investigar la interrelación de oxitalán, elaunin y fibras elásticas en la morfología de dicha valva. Las fibras de elastina forman paquetes continuos a lo largo de la valva en las capas atriales y ventriculares, orientadas paralelamente al endotelio. Las fibras de elaunin y oxitalán se distribuyen en haces de fibras más gruesas a lo largo de la valva. Las fibras más delgadas, las cuales se irradiaban hacia las capas atrial y esponjosa, ya sea como haces de fibras aisladas o arborescentes, fueron identificadas como fibras oxitalán. En la capa atrial a través de microscopía electrónica de transmisión se observaron principalmente fibras elásticas. La capa esponjosa estaba compuesta por fibras de elaunin y oxitalán; la capa ventricular mostró fibras de elaunin dispuestas en haces continuos paralelos al endotelio. Tanto fibrilina y elastina se observaron e identificaron por inmunocitoquímica con oro coloidal en las capas esponjosa y atrial de la valva atrioventricular izquierda. Estas observaciones nos permiten sugerir que el sistema de fibras de elastina-microfibrillas tienen participación en la protección mecánica y la mantención de la integridad de la valva atrioventricular izquierda en la rata.

Development of a chitosan nanofibrillar scaffold for skin repair and regeneration.

The final goal of the present study was the development of a 3-D chitosan dressing that would shorten the healing time of skin wounds by stimulating migration, invasion, and proliferation of the relevant cutaneous resident cells. Three-dimensional chitosan nanofibrillar scaffolds produced by electrospinning were compared with evaporated films and freeze-dried sponges for their biological properties. The nanofibrillar structure strongly improved cell adhesion and proliferation in vitro. When implanted in mice, the nanofibrillar scaffold was colonized by mesenchymal cells and blood vessels. Accumulation of collagen fibrils was also observed. In contrast, sponges induced a foreign body granuloma. When used as a dressing covering full-thickness skin wounds in mice, chitosan nanofibrils induced a faster regeneration of both the epidermis and dermis compartments. Altogether our data illustrate the critical importance of the nanofibrillar structure of chitosan devices for their full biocompatibility and demonstrate the significant beneficial effect of chitosan as a wound-healing biomaterial.

Cellulose microfibrils grafted with PBA via surface-initiated atom transfer radical polymerization for biocomposite reinforcement.

Immobilizing poly(butyl acrylate) (PBA) on cellulose microfibrils (CMFs) by atom transfer radical polymerization (ATRP) of butyl acrylate (BA) on the surface of 2-bromoisobutyryl-functionalized CMF generated highly hydrophobic microfibrils (CMF-PBA) with a hard core and a soft-shell structure. TGA and static water contact angle results suggested that the surfaces of the modified CMF samples were not completely covered by PBA chains until the molecular weight of grafts became sufficiently long. The GPC results indicated that the grafts with low molecular weight showed controlled/"living" characteristics of the surface-initiated ATRP; however, there existed more side reactions with the increase in molecular weights. Biocomposites consisting of polypropylene (PP) and CMF-PBA samples exhibited significantly improved compatibility, interface adhesion, and mechanical properties with the increase in PBA graft length. The findings confirmed that the longer grafts facilitated the better entanglement of PBA grafts with PP macromolecules and thus further improved the mechanical properties.

Mutations in the TGFß binding-protein-like domain 5 of FBN1 are responsible for acromicric and geleophysic dysplasias.

Geleophysic (GD) and acromicric dysplasia (AD) belong to the acromelic dysplasia group and are both characterized by severe short stature, short extremities, and stiff joints. Although AD has an unknown molecular basis, we have previously identified ADAMTSL2 mutations in a subset of GD patients. After exome sequencing in GD and AD cases, we selected fibrillin 1 (FBN1) as a candidate gene, even though mutations in this gene have been described in Marfan syndrome, which is characterized by tall stature and arachnodactyly. We identified 16 heterozygous FBN1 mutations that are all located in exons 41 and 42 and encode TGFß-binding protein-like domain 5 (TB5) of FBN1 in 29 GD and AD cases. Microfibrillar network disorganization and enhanced TGFß signaling were consistent features in GD and AD fibroblasts. Importantly, a direct interaction between ADAMTSL2 and FBN1 was demonstrated, suggesting a disruption of this interaction as the underlying mechanism of GD and AD phenotypes. Although enhanced TGFß signaling caused by FBN1 mutations can trigger either Marfan syndrome or GD and AD, our findings support the fact that TB5 mutations in FBN1 are responsible for short stature phenotypes.

Microfibrillar cardiomyopathy: a rare case.

Microfibrillar cardiomyopathy is a very rare cause of restrictive cardiomyopathy (RCM). The index case was a male patient who presented with shortness of breath and pedal edema. Further clinical investigations favored a clinical diagnosis of RCM. An endomyocardial biopsy revealed subendocardial and interstitial hyaline eosinophilic material resembling amyloid that did not stain with Congo red. An electron microscopic examination showed that this material was composed of twisted linear and bundles of tangled microfibrils. The etiology of the microfibrillar deposition is currently unknown. The pathologists should entertain the diagnosis of microfibrillar cardiomyopathy in suspected cases of amyloidosis that are negative for Congo red.

Low-dose ultraviolet radiation selectively degrades chromophore-rich extracellular matrix components.

Photoageing of human skin due to chronic exposure to ultraviolet radiation (UVR) is characterized histologically by extensive remodelling of the dermal elastic fibre system. Whilst enzymatic pathways are thought to play a major role in mediating extracellular matrix (ECM) degeneration in UV-exposed skin, the substrate specificity of UVR-up-regulated and activated matrix metalloproteinases (MMPs) is low. It is unclear, therefore, how such cell-mediated mechanisms alone could be responsible for the reported selective degradation of elastic fibre components such as fibrillin-1 and fibulin-5 during the early stages of photoageing. Here we use atomic force microscopy (AFM) and scanning transmission electron microscopy (STEM) to demonstrate that physiologically attainable doses (20-100 mJ/cm(2)) of direct UV-B radiation can induce profound, dose-dependent, changes in the structure of, and mass distribution within, isolated fibrillin microfibrils. Furthermore, using reducing and native PAGE in combination with AFM, we show that, whilst exposure to low-dose UV-B radiation significantly alters the macromolecular and quaternary structures of both UV chromophore (Cys, His, Phe, Trp and Tyr)-rich fibrillin microfibrils (fibrillin-1, 21.0%) and fibronectin dimers (fibronectin, 12.9%), similar doses have no detectable effect on UV chromophore-poor type I collagen monomers (2.2%). Analysis of the published primary amino acid sequences of 49 dermal ECM components demonstrates that most elastic fibre-associated proteins, but crucially neither elastin nor members of the collagen family, are rich in UV chromophores. We suggest, therefore, that the amino acid composition of elastic fibre-associated proteins [including the fibrillins, fibulins, latent TGFbeta binding proteins (LTBPs) and the lysyl oxidase family of enzymes (LOK/LOXLs)] may predispose them to direct degradation by UVR. As a consequence, this selective acellular photochemical pathway may play an important role in initiating and/or exacerbating cell-mediated ECM remodelling in UVR-exposed skin.

Acquired cutis laxa type II (Marshall syndrome) in an 18-month-old child: a case report.

Cutis laxa is a rare disorder resulting from degradation and clumping of elastic fibers in dermis. Type II acquired cutis laxa, shows only cutaneous changes without any systemic involvement. We describe an infant with acquired cutis laxa type II following a generalized inflammatory dermatitis.

Characterization of collagenous matrix assembly in a chondrocyte model system.

Collagen is a major component of the newly synthesized pericellular microenvironment of chondrocytes. Collagen types II, IX, and XI are synthesized and assembled into higher ordered complexes by a mechanism in which type XI collagen plays a role in nucleation of new fibrils, and in limiting fibril diameter. This study utilizes a cell line derived from the Swarm rat chondrosarcoma that allows the accumulation and assembly of pericellular matrix. Immunofluorescence and atomic force microscopy were used to assess early intermediates of fibril formation. Results indicate that this cell line synthesizes and secretes chondrocyte-specific pericellular matrix molecules including types II, IX, and XI collagen and is suitable for the study of newly synthesized collagen matrix under the experimental conditions used. AFM data indicate that small fibrils or assemblies of microfibrils are detectable and may represent precursors of the approximately 20 nm thin fibrils reported in cartilage. Treatment with hyaluronidase indicates that the dimensions of the small fibrils may be dependent upon the presence of hyaluronan within the matrix. This study provides information on the composition and organization of the newly synthesized extracellular matrix that plays a role in establishing the material properties and performance of biological materials such as cartilage.

The cytoplasmic domain of the cellulose-synthesizing complex in vascular plants.

The cytoplasmic domain of the rosette terminal complex has been imaged in situ in patches of plasma membrane isolated from tobacco BY-2 protoplasts. By partially extracting the plasma membrane lipids, cellulose microfibrils were observed through the plasma membrane. Rosette terminal complexes were identified on the basis of their association with the ends of these cellulose microfibrils. The cytoplasmic domain of the rosette terminal complex has been shown to be hexagonal in shape and has been measured to be 45-50 nm in diameter and 30-35 nm tall. These findings demonstrate that the terminal complex does indeed have a substantial cytoplasmic component, and that the hexagonal array observed in the lipid bilayer by freeze fracture is actually only a small part of the overall complex. These findings will allow better modeling of the terminal complex and may facilitate predictions of how many proteins are associated with the rosette terminal complex in vivo.