Formation Of Extracellular Matrices Research Articles

An Integrated Quorum Quenching Biocatalytic Nanoplatform for Synergistic Chemo-Photothermal Eradication of P. aeruginosa Biofilm Infections.

Decontamination of biofilm-associated infections presents a significant challenge due to the physical and chemical barrier created by the formation of extracellular matrices. This barrier restricts the access of antibiotics to the bacterial communities within the biofilm and provides protection to the persister cells, potentially leading to antibiotic resistance. In this study, we have developed an integrated quorum quenching biocatalytic nanoplatform for the synergistic chemo-photothermal eradication of P. aeruginosa biofilm infections. Ciprofloxacin (Cip), a model antibiotic, was absorbed onto PDA NPs through π-π stacking. Additionally, acylase (AC) was immobilized on PDA NPs through Schiff base reaction and Michael addition, resulting in the formation of the biocatalytic nanoplatform (PDA-Cip-AC NPs). This biocatalytic nanoplatform was able to enzymatically degrade AHL signaling molecules, thus achieving efficient quorum quenching activity to prevent biofilm formation. Furthermore, the NIR light-triggered on-demand Ciprofloxacin release further enhanced the eradication of P. aeruginosa biofilm infections with a synergy of local hyperthermia. We envision that this integrated quorum quenching nanoplatform provides a reliable tool for combating P. aeruginosa biofilm infections. STATEMENT OF SIGNIFICANCE: : An integrated quorum quenching biocatalytic nanoplatform has been developed for the eradication of P. aeruginosa biofilm infections. Quorum-sensing signals play a crucial role in modulating bacterial cell-to-cell communication, biofilm formation, and secretion of virulence factors. This biocatalytic nanoplatform efficiently degrades AHL signaling molecules, thereby blocking cell-to-cell communication and preventing biofilm formation. Additionally, local hyperthermia and on-demand Ciprofloxacin release were achieved through NIR irradiation, working synergistically to eradicate P. aeruginosa biofilm infections.

Ultrastructural evidence for the participation of muscle cells in the formation of extracellular matrices in aporocotylid blood flukes (Digenea)

The muscle cells and extracellular matrices (ECMs) of two teleost-infecting blood flukes belonging to distinct evolutionary lineages of the Aporocotylidae (Digenea) were examined using Transmission Electron Microscopy. Four morphotypes of muscle cells were found in the freshwater species Sanguinicola sp., but were considered to be various developmental stages of a single cisternic type. In the marine species Aporocotyle simplex, three types of muscle cells were apparent, one of which is cisternic. The first ultrastructural evidence is presented for the exocytosis of the moderately dense contents of dilated cisternae of cisternic muscle cells into the extracellular space in both Sanguinicola sp. and A. simplex. The basal matrices of aporocotylids support various types of epithelia. In Sanguinicola sp., beneath the distal tegumental cytoplasm, there is a thin lamina densa, whereas the intestinal epithelium is supported by a lamina reticularis. In A. simplex, both a thin lamina densa and a thick lamina reticularis underlie the distal cytoplasm of the tegument and are present at the periphery of the ovary, but beneath the epithelial lining of the caeca and both genital and excretory ducts there is only a lamina reticularis. Significant variation in the development and amount of the ECM in marine and freshwater aporocotylids is described, since A. simplex has a much better developed ECM than occurs in Sanguinicola sp. Moreover, thin myofilaments of muscle fibres participate in the ECM formation in A. simplex and represent its dominant component. The presence of two mechanisms for ECM formation in A. simplex, as opposed to a single mechanism in Sanguinicola sp., may represent further evidence for the affiliation of these two taxa to divergent evolutionary lineages. The data presented are discussed in relation to available information on these structures in other neodermatan groups.

Advances on Nanomedicines for Diagnosis and Theranostics of Hepatic Fibrosis

Hepatic fibrosis is induced by chronic hepatic injuries before it turns into hepatic cirrhosis/carcinoma. It is characterized by the formation of collagen and other extracellular matrices around damaged hepatic tissues; consequently, the normal architecture of liver would be disrupted and its function impaired. Diagnosis of hepatic fibrosis, especially at the early stage, is crucial because most fibrotic changes are reversible during the hepatic fibrosis stage. However, early and more accurate diagnosis of hepatic fibrosis still remains a great challenge. With their promising structural adjustability and targeting ability, nanomedicines have recently been introduced to improve diagnosis of hepatic fibrosis. By targeting fibrogenic cells, receptors, and extracellular matrix components, these nanomedicines can achieve detection of hepatic tissues with high sensitivity and specificity at the early stage. The use of nanomedicines can also enable theranostics of this chronic hepatic disease. This review aims to present an overview of recent advances of nanomedicines in diagnosis and theranostics of hepatic fibrosis.

Reduction of Fermentation-Associated Stresses by Straw-Based Soluble Saccharides for Enhancing Ethanol Production.

In this study, the effect of soluble polysaccharides (SPs) derived from agricultural waste, rice straw, on fermentation-associated stresses (temperature and concentrations of glucose and ethanol) was investigated to achieve high-performance ethanol production. The increase in temperature and concentrations of glucose and ethanol significantly inhibited Saccharomyces cerevisiae growth and lowered ethanol fermentation efficiency. Flow cytometric assays indicated that SPs could alleviate membrane permeability damage caused by fermentation-associated stresses. Atomic force microscopy and transmission electron microscopy revealed that fermentation-associated stresses induced cell surface shrinkage, causing a decrease in the cell size, whereas SPs stimulated the formation of extracellular matrices (EMs), which made the cell surface smooth and the cell morphology regular. Cells with EMs induced by SPs could efficiently produce ethanol under severe stresses. As a result, the titer of ethanol in the fermentation with SPs was 1.40-fold (from 26.40 to 36.98 g/L) higher than that in the fermentation without SPs, suggesting the stress-alleviating effect of SPs on ethanol production.

Three-Dimensional Multilayered Microstructure Using Needle Array Bioprinting System.

Tissue engineering is an essential component of developing effective regenerative therapies. In this study, we introduce a promising method to create scaffold-free three-dimensional (3D) tissue engineered multilayered microstructures from cultured cells using the "3D tissue fabrication system" (Regenova®; Cyfuse, Tokyo, Japan). This technique utilizes the adhesive nature of cells. When cells are cultured in nonadhesive wells, they tend to aggregate and form a spheroidal structure. The advantage of this approach is that cellular components can be mixed into one spheroid, thereby promoting the formation of extracellular matrices, such as collagen and elastin. This system enables one to create a predesigned 3D structure composed of cultured cells. We found that the advantages of this system to be (1) the length, size, and shape of the structure that were designable and highly reproducible because of the computer controlled robotics system, (2) the graftable structure could be created within a reasonable period (8 days), and (3) the constructed tissue did not contain any foreign material, which may avoid the potential issues of contamination, biotoxicity, and allergy. The utilization of this robotic system enabled the creation of a 3D multilayered microstructure made of cell-based spheres with a satisfactory mechanical properties and abundant extracellular matrix during a short period of time. These results suggest that this new technology will represent a promising, attractive, and practical strategy in the field of tissue engineering. Impact statement The utilization of the "three dimensional tissue fabrication system" enabled the creation of a three-dimensional (3D) multilayered microstructure made of cell-based spheres with a satisfactory mechanical properties and abundant extracellular matrix during a short period of time. These results suggest that this new technology will represent a promising, attractive, and practical strategy in the field of tissue engineering.

Comparative Study of Extracellular Proteolytic, Cellulolytic, and Hemicellulolytic Enzyme Activities and Biotransformation of Palm Kernel Cake Biomass by Lactic Acid Bacteria Isolated from Malaysian Foods.

Biotransformation via solid state fermentation (SSF) mediated by microorganisms is a promising approach to produce useful products from agricultural biomass. Lactic acid bacteria (LAB) that are commonly found in fermented foods have been shown to exhibit extracellular proteolytic, β-glucosidase, β-mannosidase, and β-mannanase activities. Therefore, extracellular proteolytic, cellulolytic, and hemicellulolytic enzyme activities of seven Lactobacillus plantarum strains (a prominent species of LAB) isolated from Malaysian foods were compared in this study. The biotransformation of palm kernel cake (PKC) biomass mediated by selected L. plantarum strains was subsequently conducted. The results obtained in this study exhibited the studied L. plantarum strains produced versatile multi extracellular hydrolytic enzyme activities that were active from acidic to alkaline pH conditions. The highest total score of extracellular hydrolytic enzyme activities were recorded by L. plantarum RI11, L. plantarum RG11, and L. plantarum RG14. Therefore, they were selected for the subsequent biotransformation of PKC biomass via SSF. The hydrolytic enzyme activities of treated PKC extract were compared for each sampling interval. The scanning electron microscopy analyses revealed the formation of extracellular matrices around L. plantarum strains attached to the surface of PKC biomass during SSF, inferring that the investigated L. plantarum strains have the capability to grow on PKC biomass and perform synergistic secretions of various extracellular proteolytic, cellulolytic, and hemicellulolytic enzymes that were essential for the effective biodegradation of PKC. The substantial growth of selected L. plamtraum strains on PKC during SSF revealed the promising application of selected L. plantarum strains as a biotransformation agent for cellulosic biomass.

Effects of Acute and Chronic Exposure to Residual Level Erythromycin on Human Intestinal Epithelium Cell Permeability and Cytotoxicity.

Residual concentrations of erythromycin in food could result in gastrointestinal tract exposure that potentially poses a health-hazard to the consumer, affecting intestinal epithelial permeability, barrier function, microbiota composition, and antimicrobial resistance. We investigated the effects of erythromycin after acute (48 h single treatment with 0.03 μg/mL to 300 μg/mL) or chronic (repeated treatment with 0.3 µg/mL and 300 µg/mL erythromycin for five days) exposures on the permeability of human colonic epithelial cells, a model that mimics a susceptible intestinal surface devoid of commensal microbiota. Transepithelial electrical resistance (TER) measurements indicated that erythromycin above 0.3 µg/mL may compromise the epithelial barrier. Acute exposure increased cytotoxicity, while chronic exposure decreased the cytotoxicity. Quantitative PCR analysis revealed that only ICAM1 (intercellular adhesion molecule 1) was up-regulated during 0.3 μg/mL acute-exposure, while ICAM1, JAM3 (junctional adhesion molecule 3), and ITGA8 (integrin alpha 8), were over-expressed in the 300 μg/mL acute treatment group. However, during chronic exposure, no change in the mRNA expression was observed at 0.3 μg/mL, and only ICAM2 was significantly up-regulated after 300 μg/mL. ICAM1 and ICAM2 are known to be involved in the formation of extracellular matrices. These gene expression changes may be related to the immunoregulatory activity of erythromycin, or a compensatory mechanism of the epithelial cells to overcome the distress caused by erythromycin due to increased permeability.

Saccharides in straw hydrolysate decrease cell membrane damage by phenolics by inducing the formation of extracellular matrix in yeast

The bioconversion of rice straw into ethanol can alleviate the energy crisis and solve problems related to waste treatment. In this study, the effect of soluble polysaccharides (SPs) produced during rice straw saccharification on the formation of extracellular matrices (EMs) by the yeast Saccharomyces cerevisiae was investigated. SPs were characterized by high-performance liquid chromatography (HPLC) and fourier transform infrared spectroscopy (FT-IR). SPs reduced the inhibition of alcohol dehydrogenase activity by phenolic acids (PAs) and regulated the intracellular redox state, resulting in higher ethanol production. The results of flow cytometry, confocal laser scanning microscopy, and atomic force microscopy indicated that PAs changed microbial morphology and caused damage in microbial cell membranes. The protective effect of SPs against cell membrane damage could be attributed to the synthesis of polysaccharide-dependent extracellular matrix, which maintained cellular integrity even under phenolic acid stress. These findings provide new strategies to improve pretreatment and saccharification processes.

Ointment vehicles regulate the wound-healing process by modifying the hyaluronan-rich matrix.

Topical ointment consists of an active ingredient and vehicle, and the vehicle largely comprises the volume of the ointment. During the treatment of chronic wounds, such as pressure ulcers, the vehicle has been considered inactive, only serving as a carrier of the main pharmaceutical. However, recent reports have indicated that the vehicle has distinct clinical effects that depend on its physicochemical properties. Therefore, an understanding of the action mechanism of the ointment vehicle in wound tissue is necessary. In this study, we established a mouse model to analyze tissue reactions induced by the following ointment vehicles, an oil-in-water emulsion (EM) vehicle; a macrogol ointment (MO), which is a water-soluble, hydrophilic vehicle; and a MOs containing sucrose (MS). EM-treated wounds exhibited an inflammatory reaction characterized by tissue edema and thick granulation tissue; however, MO- and MS-treated wounds did not exhibit this reaction. Moreover, EM-treated wounds exhibited infiltration of inflammatory cells unlike MO-treated wounds. In contrast, the formation of collagenous tissue was dominantly observed in MO-treated wounds. Because the vehicle regulates the water environment of the wound, the water-holding extracellular matrix molecules, including hyaluronan (HA) and proteoglycan, were examined using immunohistochemical and biochemical methods. The versican G1 fragment, serum-derived HA-associated protein (SHAP) and HA (the VG1F-SHAP-HA) complex characteristically found in inflammatory conditions of pressure ulcers was found in EM-treated wounds. To histologically analyze the mechanism of action of the vehicle, we evaluated the ointment vehicle-wound tissue interface in an en bloc manner. Formation of the HA-containing complex was observed locally between the vehicle and wound surface. On the basis of these data, ointment vehicles regulate the wound-healing process through the formation of HA-rich extracellular matrices at the ointment-wound interface. This study provides a better understanding of the treatment of deep-pressure ulcers with focus on ointment vehicles.

Effects of collagen-derived bioactive peptides and natural antioxidant compounds on proliferation and matrix protein synthesis by cultured normal human dermal fibroblasts

Nutraceuticals containing collagen peptides, vitamins, minerals and antioxidants are innovative functional food supplements that have been clinically shown to have positive effects on skin hydration and elasticity in vivo. In this study, we investigated the interactions between collagen peptides (0.3–8 kDa) and other constituents present in liquid collagen-based nutraceuticals on normal primary dermal fibroblast function in a novel, physiologically relevant, cell culture model crowded with macromolecular dextran sulphate. Collagen peptides significantly increased fibroblast elastin synthesis, while significantly inhibiting release of MMP-1 and MMP-3 and elastin degradation. The positive effects of the collagen peptides on these responses and on fibroblast proliferation were enhanced in the presence of the antioxidant constituents of the products. These data provide a scientific, cell-based, rationale for the positive effects of these collagen-based nutraceutical supplements on skin properties, suggesting that enhanced formation of stable dermal fibroblast-derived extracellular matrices may follow their oral consumption.

A Biomimetic Silk Fibroin/Sodium Alginate Composite Scaffold for Soft Tissue Engineering.

A cytocompatible porous scaffold mimicking the properties of extracellular matrices (ECMs) has great potential in promoting cellular attachment and proliferation for tissue regeneration. A biomimetic scaffold was prepared using silk fibroin (SF)/sodium alginate (SA) in which regular and uniform pore morphology can be formed through a facile freeze-dried method. The scanning electron microscopy (SEM) studies showed the presence of interconnected pores, mostly spread over the entire scaffold with pore diameter around 54~532 μm and porosity 66~94%. With significantly better water stability and high swelling ratios, the blend scaffolds crosslinked by 1-ethyl-3-(3-dimethylaminopropyl) carbodiimide (EDC) provided sufficient time for the formation of neo-tissue and ECMs during tissue regeneration. Fourier transform infrared spectroscopy (FT-IR), X-ray diffraction (XRD) results confirmed random coil structure and silk I conformation were maintained in the blend scaffolds. What’s more, FI-TR spectra demonstrated crosslinking reactions occurred actually among EDC, SF and SA macromolecules, which kept integrity of the scaffolds under physiological environment. The suitable pore structure and improved equilibrium swelling capacity of this scaffold could imitate biochemical cues of natural skin ECMs for guiding spatial organization and proliferation of cells in vitro, indicating its potential candidate material for soft tissue engineering.

Variation of mechanical behavior of β-TCP/collagen two phase composite scaffold with mesenchymal stem cell in vitro

The primary aim of this study is to characterize the variational behavior of the compressive mechanical property of bioceramic-based scaffolds using stem cells during the cell culture period. β-Tricalcium phosphate (TCP)/collagen two phase composites and β-TCP scaffolds were fabricated using the polyurethane template technique and a subsequent freeze-drying method. Rat bone-marrow mesenchymal stem cells (rMSCs) were then cultured in these scaffolds for up to 28 days. Compression tests of the scaffolds with rMSCs were periodically conducted. Biological properties, such as the cell number, alkaline phosphatase (ALP) activity, and gene expressions of osteogenesis, were evaluated. The microstructural change due to cell growth and the formation of extracellular matrices was examined using a field-emission scanning electron microscope. The compressive property was then correlated with the biological properties and microstructures to understand the mechanism of the variational behavior of the macroscopic mechanical property. The porous collagen structure in the β-TCP scaffold effectively improved the structural stability of the composite scaffold, whereas the β-TCP scaffold exhibited structural instability with the collapse of the porous structure when immersed in a culture medium. The β-TCP/collagen composite scaffold exhibited higher ALP activity and more active generation of osteoblastic markers than the β-TCP scaffold.

Sulfated hyaluronan influences the formation of artificial extracellular matrices and the adhesion of osteogenic cells.

The aim of this study is to compare differentially sulfated hyaluronan (sHA) derivatives and chondroitin sulfate (CS) with respect to their ability to influence the formation of artificial extracellular matrices (aECMs) during in vitro-fibrillogenesis of collagen type I at high- and low-ionic strength. Analysis is performed using turbidity, biochemical assays, atomic force (AFM), and transmission electron microscopy (TEM). In general, high-sulfated glycosaminoglycans (GAGs) associate to a higher amount with collagen than the low-sulfated ones. The addition of GAGs prior to fibrillogenesis at low-ionic strength results in a dose-dependent decrease in fibril diameter. At high-ionic strength these effects are only obtained for the sHA derivatives but not for CS. Likewise, increasing concentrations and degree of GAG sulfation strongly affected the kinetics of fibrillogenesis. The impact of sulfation degree on F-actin location and fiber formation in SaOS-2 cells implies that adhesion-related intracellular signaling is influenced to a variable extent.

Prolyl 4-Hydroxlase Activity Is Essential for Development and Cuticle Formation in the Human Infective Parasitic Nematode Brugia malayi

Collagen prolyl 4-hydroxylases (C-P4H) are required for formation of extracellular matrices in higher eukaryotes. These enzymes convert proline residues within the repeat regions of collagen polypeptides to 4-hydroxyproline, a modification essential for the stability of the final triple helix. C-P4H are most often oligomeric complexes, with enzymatic activity contributed by the α subunits, and the β subunits formed by protein disulfide isomerase (PDI). Here, we characterize this enzyme class in the important human parasitic nematode Brugia malayi. All potential C-P4H subunits were identified by detailed bioinformatic analysis of sequence databases, function was investigated both by RNAi in the parasite and heterologous expression in Caenorhabditis elegans, whereas biochemical activity and complex formation were examined via co-expression in insect cells. Simultaneous RNAi of two B. malayi C-P4H α subunit-like genes resulted in a striking, highly penetrant body morphology phenotype in parasite larvae. This was replicated by single RNAi of a B. malayi C-P4H β subunit-like PDI. Surprisingly, however, the B. malayi proteins were not capable of rescuing a C. elegans α subunit mutant, whereas the human enzymes could. In contrast, the B. malayi PDI did functionally complement the lethal phenotype of a C. elegans β subunit mutant. Comparison of recombinant and parasite derived material indicates that enzymatic activity may be dependent on a non-reducible covalent link, present only in the parasite. We therefore demonstrate that C-P4H activity is essential for development of B. malayi and uncover a novel parasite-specific feature of these collagen biosynthetic enzymes that may be exploited in future parasite control.

Cardiomyocyte Specific Deficiency of Serine Palmitoyltransferase Subunit 2 Reduces Ceramide but Leads to Cardiac Dysfunction

The role of serine palmitoyltransferase (SPT) and de novo ceramide biosynthesis in cardiac ceramide and sphingomyelin metabolism is unclear. To determine whether the de novo synthetic pathways, rather than ceramide uptake from circulating lipoproteins, is important for heart ceramide levels, we created cardiomyocyte-specific deficiency of Sptlc2, a subunit of SPT. Heart-specific Sptlc2-deficient (hSptlc2 KO) mice had a >35% reduction in ceramide, which was limited to C18:0 and very long chain ceramides. Sphingomyelinase expression, and levels of sphingomyelin and diacylglycerol were unchanged. But surprisingly phospholipids and acyl CoAs contained increased saturated long chain fatty acids. hSptlc2 KO mice had decreased fractional shortening and thinning of the cardiac wall. While the genes regulating glucose and fatty acid metabolism were not changed, expression of cardiac failure markers and the genes involved in the formation of extracellular matrices were up-regulated in hSptlc2 KO hearts. In addition, ER-stress markers were up-regulated leading to increased apoptosis. These results suggest that Sptlc2-mediated de novo ceramide synthesis is an essential source of C18:0 and very long chain, but not of shorter chain, ceramides in the heart. Changes in heart lipids other than ceramide levels lead to cardiac toxicity.

Characterization of a biofilm-like extracellular matrix inFLO1-expressingSaccharomyces cerevisiaecells

Like bacteria, fungi growing in biofilms are often embedded in a so-called extracellular matrix (ECM), a complex and species-specific mixture of compounds secreted by cells in the biofilm. The precise physiological role of this ECM and its importance for the stress and drug resistance that is so characteristic of biofilms remain vague. Here, we describe the discovery of an ECM produced by flocculating Saccharomyces cerevisiae cells. Although S. cerevisiae has long been believed not to produce an ECM, our results indicate that flocculating cells secrete a mixture of glucose and mannose polysaccharides that surrounds flocculating cells. This matrix impedes the penetration of large molecules into the floc, but does not seem to play a role in the resistance of flocculating cultures to drugs and ethanol. Together, our results provide a new model system to study the formation and biological role of microbial extracellular matrices.

Nanomechanical properties of alginate-recovered chondrocyte matrices for cartilage regeneration

Tissue-engineered cartilage constructs designed for in-vivo applications intuitively should mimic the mechanical properties of native cartilage. The objective of the present work was to characterize the nanomechanical properties of alginate-recovered chondrocyte matrices as a function of ex-vivo incubation time. Chondrocytes isolated from the articular cartilage of the mature bovine metacarpophalangeal joints were cultured with alginate hydrogel to allow for the formation of extracellular matrices. The recovered chondral constructs after 2, 4, 8, and 12 weeks of ex-vivo incubation were analysed using nanoindentation with atomic force microscopy to determine their mechanical properties. Chondral constructs had average Young's moduli of 123 +/- 22 kPa, 174 +/- 31 kPa, 373 +/- 40 kPa, and 564 +/- 79 kPa after incubation for 2, 4, 8, and 12 weeks respectively, indicating the gradual attainment of mechanical stiffness. This escalating trend of micromechanical properties as a function of increasing ex-vivo incubation time suggests that chondral constructs via a tissue-engineering approach are capable of elaborating extracellular matrices and increase mechanical stiffness. The relationship between Young's modulus and incubation time of the chondral constructs is useful in the design and fabrication of tissue-engineered cartilage constructs.

Phenotypic Convergence Mediated by GGDEF-Domain-Containing Proteins

GGDEF domain-containing proteins have been implicated in bacterial signal transduction and synthesis of the second messenger molecule cyclic-di-GMP. A number of GGDEF proteins are involved in controlling the formation of extracellular matrices. AdrA (Salmonella enterica serovar Typhimurium) and HmsT (Yersinia pestis) contain GGDEF domains and are required for extracellular cellulose production and biofilm formation, respectively. Here we show that hmsT is able to restore cellulose synthesis to a Salmonella serovar Typhimurium adrA mutant and that adrA can replace hmsT in Y. pestis Hms-dependent biofilm formation. Like Y. pestis HmsT overproducers, Y. pestis cells carrying adrA under the control of an arabinose-inducible promoter produced substantial biofilms in the presence of arabinose. Finally, we demonstrate that HmsT is involved in the synthesis of cyclic di-GMP.

Guilty by Association: Some Collagen II Mutants Alter the Formation of ECM as a Result of Atypical Interaction with Fibronectin

Among the structural components of extracellular matrices (ECM) fibrillar collagens play a critical role, and single amino acid substitutions in these proteins lead to pathological changes in tissues in which they are expressed. Employing a biologically relevant experimental model consisting of cells expressing R75C, R519C, R789C, and G853E procollagen II mutants, we found that the R789C mutation causing a decrease in the thermostability of collagen not only alters individual collagen molecules and collagen fibrils, but also has a negative impact on fibronectin. We propose that thermolabile collagen molecules are able to bind to fibronectin, thereby altering intracellular and extracellular processes in which fibronectin takes part, and we postulate that such an atypical interaction could change the architecture of the ECM of affected tissues in patients harboring mutations in genes encoding fibrillar collagens.

Glomerulosclerosis develops in Thy‐1 nephritis under persistent accumulation of macrophages

To clarify the relationship between macrophages and development of glomerulosclerosis, the authors developed a new experimental nephritis model with macrophages persisting in Thy-1 nephritis. Methyl-cellulose was administered intraperitoneally in addition to the intravenous injection of the anti-Thy-1 antibody to Wistar rats. Foamy macrophages influxed into the lytic mesangium and stayed to form nodular aggregates. Mesangial cells proliferated with the formation of extracellular matrices around these nodular aggregates of macrophages. Immunohistochemical analyses revealed that alpha-smooth muscle actin (alpha-SMA) was expressed in the proliferative area around these nodules of foamy macrophages from day 7. Type I collagen and type IV collagen were also expressed around the foamy macrophages in correspondence with alpha-SMA expression from day 7. The electron microscopic study revealed that collagen fibrils were formed around the transformed mesangial cells. The expression of platelet endothelial cell adhesion molecule-1 (PECAM-1, CD31), a marker of glomerular vasculature endothelial cells, was not found in the area occupied by the foamy macrophages, suggesting the impairment of glomerular reconstruction. Macrophages may participate in the progression of glomerulosclerosis in Thy-1 nephritis by enhancing the production of the extracellular matrix through transformed mesangial cells and preventing reconstruction of the capillary network.