Fibronectin in disease

Fibronectin and Fibrinogen in the Plasma and Dialysate of Patients on CAPD

Plasma and dialysate fluid from 18 patients treated with continuous ambulatory peritoneal dialysis (CAPD) while peritonitis -free, were analysed for fibronectin (FN), fibrinogen (FG), albumin (ALB) and total protein (TP). Mean plasma FG (6.24 g/l) was higher than for normal controls (4.23 g/1; p < 0.001) whereas FN (0.31 g/l) was lower than for normal (0.36 g/l; p < 0.02). Twenty-four hour losses of proteins into the dialysate were as follows: TP = 10.9 g, ALB = 5.2 g, FN = 15.6 mg and FG = 221 mg. Mean dialysate concentration for FN was 2.09 mg/1 and FG 31.1 mg/l. Dialysate FN and FG correlated with dialysate ALB (r = 0.92; p < 0.001, r = 0.60; p < 0.01 respectively) suggesting an ultrafiltrate rather than synthesis within the peritoneum.

Ligamental compartments and their relation to the passing spinal nerves are detectable with MRI inside the lumbar neural foramina

PURPOSE

Intraforaminal ligaments (IFL) in lumbar neural foramina (NF) and their relation to the lumbar spinal nerves (SN) are addressed.

METHOD

Giemsa- and PAS-stained plastinated body slices of 15 lumbar spines were made and compared to MRI and CT data acquired of the same fresh specimens. We dissected one fixed lumbar spine to discuss our results with previous literature. Macroscopic pathophysiological changes and operational interventions at these lumbar spines were excluded.

RESULTS

In the NF, thin medial IFL touch the SN. As a second compartment, intermedial vertical IFL are seen. A third lateral horizontal compartment of IFL is formed by thick cranial and caudal ligaments. Ligaments of the second and third compartments have no direct contact with the SN. From medial to lateral, the IFL thicken. All compartments are 3D reconstructed. If compartments of the IFL have no direct contact with the SN seen in the slices, a connection was noticed after dissection.

CONCLUSION

Manual dissection seems to be inappropriate for a detailed study of the IFL. The lateral and intermedial compartments being free of the SN may transmit power and protect the SN, while the thin medial IFL may lead the SN passing the NF under physiological conditions. We conclude from the close topographical relation that the IFL may be relevant in foraminal stenosis. Any herniation in the NF presses IFL to the SN. Therefore, we think the IFL themselves could cause neurogenic claudication in case of their non-physiological turnover. Visualisation of IFL seems to be possible by using MRI. These slides can be retrieved under Electronic Supplementary Material.

Fibronectin Mechanobiology Regulates Tumorigenesis

Fibronectin (Fn) is an essential extracellular matrix (ECM) glycoprotein involved in both physiological and pathological processes. The structure–function relationship of Fn has been and is still being studied, as changes in its molecular structure are integral in regulating (or dysregulating) its biological activities via its cell, matrix component, and growth factor binding sites. Fn comprises three types of repeating modules; among them, FnIII modules are mechanically unstable domains that may be extended/unfolded upon cell traction and either uncover cryptic binding sites or disrupt otherwise exposed binding sites. Cells assemble Fn into a fibrillar network; its conformational flexibility implicates Fn as a critical mechanoregulator of the ECM. Fn has been shown to contribute to altered stroma remodeling during tumorigenesis. This review will discuss (i) the significance of the structure–function relationship of Fn at both the molecular and the matrix scales, (ii) the role of Fn mechanobiology in the regulation of tumorigenesis, and (iii) Fn-related advances in cancer therapy development.

Fibrotic remodeling of the extracellular matrix through a novel (engineered, dual-function) antibody reactive to a cryptic epitope on the N-terminal 30 kDa fragment of fibronectin

Fibrosis is characterized by excessive accumulation of scar tissue as a result of exaggerated deposition of extracellular matrix (ECM), leading to tissue contraction and impaired function of the organ. Fibronectin (Fn) is an essential component of the ECM, and plays an important role in fibrosis. One such fibrotic pathology is that of proliferative vitreoretinopathy (PVR), a sight-threatening complication which develops as a consequence of failure of surgical repair of retinal detachment. Such patients often require repeated surgeries for retinal re-attachment; therefore, a preventive measure for PVR is of utmost importance. The contractile membranes formed in PVR, are composed of various cell types including the retinal pigment epithelial cells (RPE); fibronectin is an important constituent of the ECM surrounding these cells. Together with the vitreous, fibronectin creates microenvironments in which RPE cells proliferate. We have successfully developed a dual-action, fully human, fibronectin-specific single chain variable fragment antibody (scFv) termed Fn52RGDS, which acts in two ways: i) binds to cryptic sites in fibronectin, and thereby prevents its self polymerization/fibrillogenesis, and ii) interacts with the cell surface receptors, ie., integrins (through an attached “RGD” sequence tag), and thereby blocks the downstream cell signaling events. We demonstrate the ability of this antibody to effectively reduce some of the hallmark features of fibrosis - migration, adhesion, fibronectin polymerization, matrix metalloprotease (MMP) expression, as well as reduction of collagen gel contraction (a model of fibrotic tissue remodeling). The data suggests that the antibody can be used as a rational, novel anti-fibrotic candidate.

Prognosis of Non–Small Cell Lung Cancer Patients by Detecting Circulating Cancer Cells in the Peripheral Blood with Multiple Marker Genes

Purpose: Current lung cancer staging and prognosis methods are based on imaging methods, which may not be sensitive enough for early and accurate detection of metastasis. This study aims to validate the use of a panel of markers for circulating cancer cell detection to improve the accuracy of cancer staging, prognosis, and as a rapid assessment of therapeutic response.

Experimental Design: We analyzed the National Cancer Institute-Cancer Genome Anatomy Project database to identify potential marker genes for the detection of circulating cancer cells in peripheral blood. Nested real-time quantitative PCR and a scoring method using cancer cell load Lc were employed to correlate the amount of circulating cancer cells with clinical outcomes in 54 non–small cell lung cancer (NSCLC) patients. The Kaplan-Meier method was employed for analysis of prognostic variables.

Results: A panel of four marker genes was identified and experimentally validated. With these marker genes, we achieved an overall positive detection rate of 72% for circulating cancer cells in the peripheral blood of NSCLC patients. Patients who had higher Lc values had worse outcomes and shorter survival times. Patients with poor therapeutic response were revealed by positive detection of circulating cancer cells after therapy. The results correlated well with the patients' survival time.

Conclusion: Circulating cancer cell detection by a panel of markers and the Lc scoring method can supplement the current tumor, node, metastasis staging method for improved prognosis and for rapid assessment of therapeutic response. Together, they may facilitate the design of better therapeutic strategies for the treatment of NSCLC patients.

Strong intracellular and negative peripheral expression of fibronectin in tumor cells contribute to invasion and metastasis in papillary thyroid carcinoma

The intracellular and stromal expression of fibronectin (FN) in invading and central parts of papillary thyroid carcinomas with/without lymph node (LN) metastasis (54 metastasizing cases, 52 non-metastasizing cases) were examined immunohistochemically. The intracellular expression of FN in tumor cells in invading parts was stronger than that in central parts in most cases (79/106 cases, 74.5%). In invading parts, negative stromal FN was frequently found at the periphery of the tumor in cases with extracapsular soft tissue invasion (26/37 cases). Tumor cells in invading parts in metastatic cases were significantly more likely to be negative for stromal FN at the periphery of the tumor than those in non-metastatic cases (P < 0.0001). The strong intracellular and negative stromal FN at the periphery of the tumor in invading parts were associated with invasion and metastasis in papillary thyroid carcinoma. These results suggest that these distinctive characteristics of FN may be useful for understanding invasion and metastasis in vivo.

Retention of intracellular fibronectin expression in primary and metastatic thyroid carcinoma: an immunohistochemical study

We previously showed that thyroid carcinoma distinctively expresses intracellular fibronectin (FN) compared to other carcinomas. To determine the persistency of such FN accumulation in metastasis, we immunohistochemically examined the accumulation of intracellular FN in 92 cases of different carcinomas originating from the thyroid gland, lung and kidney, 44 of which showed metastasis to other organs. In all of the cases, normal epithelial cells adjacent to carcinomas did not show intracellular FN. Almost all of the cases (31/32) of thyroid carcinoma with/without metastasis to the lung and/or kidney showed intracellular FN in both the primary and metastatic lesions. Few cases (2/38) of lung carcinoma and none of the 22 cases of kidney carcinoma showed intracellular FN in the primary and metastatic lesions. In conclusion, the intracellular accumulation of FN acquired after carcinogenic transformation is not a common phenomenon in carcinomas, but rather is distinctive for thyroid carcinoma, even when it metastasizes to other organs. The immunohistochemical detection of intracellular FN may be useful for diagnosing thyroid carcinoma, even in metastatic lesions.

Deposition of extracellular matrix on silicone intraocular lens implants in rabbits

PURPOSE

To examine the deposition of extracellular matrix on silicone intraocular lenses (IOLs) implanted experimentally into rabbit eyes by electron microscopy and to determine the immunolocalization of extracellular matrix components, including collagen types and cellular fibronectin, on these IOLs.

METHODS

We performed phacoemulsification and aspiration of the crystalline lens and implanted a foldable silicone IOL in the capsular bag of one eye of each of 26 adult albino rabbits under general anesthesia. After 8 weeks the animals were killed and the eyes were enucleated. The silicone IOLs were processed for electron microscopy and for immunohistochemical detection of collagen types I, III, and IV and cellular fibronectin.

RESULTS

Electron microscopy revealed deposition of a presumed cell matrix complex on the optic portion of all silicone IOLs, as well as the adhesion of presumed macrophages and foreign-body giant cells. Cellular deposits showed immunoreactivity for cellular fibronectin. Fibrous or membranous deposits exhibited immunoreactivity for cellular fibronectin and collagen types I and III. A few type IV collagen-immunoreactive deposits were also seen.

CONCLUSION

Deposits of extracellular matrix components were observed on silicone IOLs. These deposits may form the scaffolding for the adhesion and proliferation of cells. These matrix components appeared to be the products of cells adhering to the surfaces of IOLs, including lens epithelial cells, macrophages and foreign-body giant cells, indicating that the process of granulation was incomplete.

Deposition of extracellular matrix on intraocular lenses in rabbits: an immunohistochemical and transmission electron microscopic study

BACKGROUND

We examined by transmission electron microscopy the accumulation of extracellular matrix on intraocular lenses (IOLs) implanted experimentally into rabbit eyes, and evaluated the immunolocalization of such extracellular matrix components as collagen types I, III, and IV, and cellular fibronectin on these IOLs.

METHODS

Phacoemulsification and aspiration of the crystalline lens were performed and an IOL was implanted into the capsular bag of each eye of each of 16 adult albino rabbits under general anesthesia. After up to 12 weeks, the animals were killed and the IOLs were removed. Specimens were processed for transmission electron microscopy or for immunohistochemical detection collagen types I, III, and IV, and cellular fibronectin.

RESULTS

Transmission electron microscopy revealed an accumulation of extracellular matrix between the residual anterior lens capsule and the surface of an IOL explanted 4 weeks after surgery. Collagen types I and III and cellular fibronectin were detected immunohistochemically on each IOL in association with cellular deposits. Type IV collagen-immunoreactive matrix was not seen on the optic portion, but was detected on the haptic portion of one of six IOLs examined.

CONCLUSION

Each component of the extracellular matrix that is deposited on the IOL supplies scaffolding for the adhesion and proliferation of cells. These components are considered to be produced by cells such as lens epithelial cells and macrophages that adhere to the IOL surface.

Extracellular matrix on intraocular lenses

We examined the distribution of extracellular matrix components in the proteinaceous matrix on explanted IOLs using immunohistochemistry to clarify the nature of proteinaceous deposits on the surfaces of IOLs. We examined 15 polymethylmethacrylate (PMMA) IOLs and one silicone IOL explanted from patients. The IOLs were immunostained for cellular fibronectin, types I and IV collagen, and vitronectin. Various amounts of fibronectin, types I and IV collagen, and vitronectin were detected in the extracellular matrix on all IOLs with cellular deposits. Types I and IV collagen and cellular fibronectin were present in the extracellular matrix and were probably the products of cells adhering to the IOLs. Vitronectin in the fibrous extracellular matrix appeared to represent an adsorption material derived from the aqueous humor. These proteinaceous deposits associated with cellular deposits indicate unsuccessful formation of granulation tissue and could influence IOL biocompatibility.

A new protocol for the propagation of dendritic cells from rat bone marrow using recombinant GM-CSF, and their quantification using the mAb OX-62

Bone marrow (BM)-derived dendritic cells (DC) are the most potent known antigen (Ag) presenting cell in vivo and in vitro. Detailed analysis of their properties and mechanisms of action requires an ability to produce large numbers of DC. Although DC have been isolated from several rat tissues, including BM, the yield is uniformly low. We describe a simple method for the propagation of large numbers of DC from rat BM and document cell yield with the rat DC marker, OX-62. After depletion of plastic-adherent and Fc+ cells by panning on dishes coated with normal serum, residual BM cells were cultured in gelatin coated flasks using murine rGM-CSF supplemented medium. Prior to analysis, non-adherent cells were re-depleted of contaminating Fc+ cells. Propagation of DC was monitored by double staining for FACS analysis (major histocompatibility complex (MHC) class II+/OX-62+, OX-19-). Functional assay, morphological analysis and evaluation of homing patterns of cultured cells revealed typical DC characteristics. MHC class II and OX-62 antigen expression increased with time in culture and correlated with allostimulatory ability. DC yield increased until day 7, when 3.3 x 10(6) DC were obtained from an initial 3 x 10(8) unfractionated BM cells. Significant numbers of DC can be generated from rat BM using these simple methods. This should permit analysis and manipulation of rat DC functions in vivo and in vitro.

Basement membrane and extracellular interstitial matrix components in bladder neoplasia--evidence of angiogenesis

Immunohistochemical studies to localise collagen IV, laminin, fibronectin and tenascin were undertaken in 59 bladder biopsies. These were non-neoplastic or contained foci of flat dysplasia or of transitional cell neoplasia. Collagen IV and laminin were reliably demonstrated in basement membranes but focal loss of reactivity for collagen IV was found in the urothelial basement membrane in some cases of inflammation, dysplasia, and non-invasive papillary transitional cell tumour. Basement membranes were rarely demonstrated around invasive transitional cell carcinomas. Fibronectin and tenascin were found in the sub-urothelial lamina propria and in some urothelial basement membranes. The stroma of invasive tumours reacted strongly for both. Increased numbers of sub-urothelial capillaries were present in association with some cases of cystitis, flat dysplasia or non-invasive transitional cell neoplasia suggesting an angiogenic stimulus in these circumstances. Immunohistochemical staining of basement membrane components is unlikely to be of value in the routine histopathological assessment of transitional cell neoplasms of the bladder.

Recent advances in bovine vaccine technology

A description of new commercial and experimental vaccines for viral and bacterial diseases of cattle can be broadly divided into those used for both beef and dairy cows and those used predominantly in dairy cattle. For both types of cattle, newer and experimental vaccines are directed against several of the important viral (e.g., bovine herpesvirus 1, bovine viral diarrhea virus, bovine respiratory syncytial virus, parainfluenza type 3, and foot-and-mouth disease virus) and bacterial pathogens (e.g., Pasteurella spp., Haemophilus somnus). The viral vaccines include gene-deleted, modified live, subunit, and peptide antigens. Newer bacterial vaccines, particularly those for Pasteurella spp., are composed of either modified-live vaccines or bacterins supplemented with toxoid or surface antigens. Haemophilus somnus vaccine research has concentrated mainly on defining unique surface antigens. Novel dairy cow vaccines would include the lipopolysaccharide-core (J5) antigen approach, which has been used for successful immunization against coliform mastitis. Core antigen vaccines also have reduced calf mortality from Gram-negative pathogens. Staphylococcal mastitis vaccines that contain capsular antigens, toxoids, or the staphylococcal fibronectin receptor are of active research interest. Vaccines against mastitis induced by Streptococcus agalactiae and Streptococcus uberis also are areas of intensive research. Delivery of multiple subunit antigens with optimal immune response induction has led to the investigation of attenuated heterologous viral and bacterial expression vectors such as bovine herpesvirus 1, vaccinia, and Salmonella spp. This discussion also demonstrates that molecular biology is being used to advance bovine vaccine technology.

Origin of fibronectin in epiretinal membranes of proliferative vitreoretinopathy and proliferative diabetic retinopathy

Fibronectins, high molecular multifunctional glycoproteins of the extracellular matrix and plasma, have been a popular area of research in the pathogenesis of proliferative disorders of the retina. Several immunohistochemical studies have revealed that fibronectin is a major constituent of epiretinal membranes and that the cell types involved in proliferative intraocular disorders may synthesise it. However, owing to the fact that plasma and cellular fibronectin are similar in their overall structure, the origin of fibronectin in epiretinal membranes has not yet been clearly defined. In this study, we used two monoclonal antibodies: FN-3, which recognises an extra domain present in the cellular but not plasma form of fibronectin; and FN-4, which reacts with an antigenic site on both plasma and cellular fibronectin. In 37 epiretinal membranes obtained from eyes with proliferative vitreoretinopathy and proliferative diabetic retinopathy, we demonstrated the presence of cellular fibronectin, thus indicating local production. The significantly stronger and positive immunostain with FN-4 in the same specimens suggests the colocalisation of plasma fibronectin, that may be derived from the breakdown of the blood-retinal barrier and trapped in membranes during their formation. In pathological vitreous we demonstrated both types of fibronectin by western blot analysis.

The extracellular matrix of reparative tissue in the vitreous: fibronectin production in proliferative diabetic retinopathy membranes

In a preliminary investigation into the origins of the extracellular matrix glycoprotein fibronectin in proliferative diabetic retinopathy (PDR) membranes, four globes containing PDR membranes were subjected to in situ hybridisation and immunohistochemical studies. Fibronectin mRNA was found in PDR membrane cells in two of the four globes. The fibronectin-producing cells exhibited fibroblast-like or macrophage-like morphology. Occasional intraretinal macrophage-like cells which contained fibronectin mRNA were also observed in three of the eyes. Variable fibronectin immunoreactivity was observed in all the PDR membranes, while the fibronectin staining pattern in the underlying retina was similar to that reported for albumin in eyes with breakdown of the blood-retina barrier. The findings suggest that fibronectin in PDR membranes originates from both plasma-derived fibronectin and the membrane cells, and support the concept that extracellular matrix components play an important role in PDR membrane progression.

Fibronectin synthesis in subretinal membranes of proliferative vitreoretinopathy

In situ hybridisation and immunohistochemical studies were conducted on six surgically excised subretinal membranes of proliferative vitreoretinopathy to investigate whether displacement of retinal pigment epithelial and glial cells to subretinal membranes was associated with fibronectin production by the subretinal membrane cells. Fibronectin messenger RNA (mRNA) and fibronectin immunoreactivity were observed in some cells in all of the subretinal membranes studied and up to 30% of the cells in individual specimens showed intense labelling for fibronectin mRNA. The results support the concept that the cells in subretinal membranes produce fibronectin. Locally produced fibronectin may play a role in subretinal membrane cohesion, and displacement of retinal pigment epithelial and glial cells from their normal location may induce the cells to manufacture fibronectin. Fibronectin production may be more prominent in migrating subretinal cells.

Use of biospecific interactions of collagen, fibronectin and their fragments in affinity chromatography

Various aspects of the application of fibronectin-collagen biospecific interactions in affinity chromatography are described. A new biospecific method for one-stage isolation of collagen peptides containing fibronectin-binding sites is proposed. The alpha 1 CB7-peptide of type-I collagen cyanogen bromide cleavage was isolated by means of affinity chromatography on adsorbents containing an immobilized gelatin-binding domain (45,000 relative molecular mass) of fibronectin. The method gives highly purified preparations of alpha 1 CB7-peptide. This peptide, as well as some other collagen molecular fragments (alpha-chains, beta-components, alpha 1 CB8-peptide), were immobilized on Sepharose, and the properties of such affinity adsorbents obtained were studied. Adsorbents with immobilized alpha-chains and alpha 1 CB7-peptide had a fibronectin-binding capacity 1.5-2.0 times higher than commercial gelatin-Sepharose. Large-scale production of highly purified fibronectin from human plasma, using affinity chromatography on immobilized individual alpha-chains of collagen, was developed.

Vitronectin in liver disorders: biochemical and immunohistochemical studies

The concentration of plasma vitronectin was determined and compared with various parameters of liver function including the blood coagulation system in patients with liver diseases. The severity of cirrhosis was graded according to Child's criteria and compared with the plasma vitronectin level. Furthermore, the distribution of vitronectin in the liver of patients with liver diseases was studied by light and electron microscopy using the indirect immunoperoxidase method. The plasma vitronectin level was low in all liver disease groups as compared with the healthy controls. The difference from the controls was significant in patients with hepatocellular carcinoma and decompensated cirrhosis. Moreover, the plasma vitronectin level was positively correlated with the levels of serum cholinesterase, albumin, plasma alpha 2 plasmin inhibitor-plasmin complex and the prothrombin time and results of the hepatoplastin test. Plasma vitronectin decreased with increasing severity of cirrhosis according to Child's criteria. These results suggest that the plasma vitronectin level is a useful parameter of hepatic synthetic function in patients with liver diseases; it may also reflect the severity of cirrhosis. Light microscopy revealed vitronectin in the area of focal necrosis and the portal tracts in the liver of patients with acute viral hepatitis, in the area of piecemeal necrosis in the liver of patients with chronic hepatitis and along the area of fiber deposition in the liver of patients with cirrhosis. Immunoelectron microscopy showed vitronectin in the rough endoplasmic reticulum of hepatocytes. Moreover, vitronectin was seen around inflammatory cells, endothelial cells, Ito cells and hepatocytes in the perisinusoidal area near focal necrosis and piecemeal necrosis and on collagen fibers.(ABSTRACT TRUNCATED AT 250 WORDS)

Local production of fibronectin by ectopic human retinal cells

The distribution of fibronectin mRNA and fibronectin in adult human retina and epiretinal membranes was investigated by in situ hybridisation and immunohistochemical techniques. The cells in normal adult retina contained little or no fibronectin mRNA and the retina only showed fibronectin immunoreactivity in retinal vessels. The cells in detached neuroretina did not contain fibronectin message but the vitreoretinal interface of the detached retina exhibited variable fibronectin immunoreactivity. Retinal glia, retinal pigment epithelium and fibroblast-like cells in membranes at the vitreoretinal juncture (epiretinal membranes) showed variable labelling with the fibronectin mRNA probe and all the membranes immunostained for fibronectin. No difference could be detected between membrane cell types in the intensity of labelling with the mRNA probe or for fibronectin immunoreactivity. The results indicate that cells in situ in attached and detached adult human retina do not produce fibronectin. Although fibronectin at the vitreoretinal juncture in retinal detachment is probably partly derived from plasma fibronectin resulting from breakdown of the blood-retinal barrier, ectopic retinal cells produce fibronectin and contribute to the glycoprotein epiretinal membranes.

Acute phase reactants in leprosy

Serum levels of C-reactive protein (CRP) and plasma levels of fibronectin (Fn) were studied in 74 untreated leprosy patients. CRP was detected by latex agglutination in 25.6% of the patients. A significant increase in Fn levels was seen in all the groups of leprosy patients, as compared to the controls.

Time-resolved immunofluorometric assays with measurement of a europium chelate in solution: application for sensitive determination of fibronectin

A novel detection principle applicable for sensitive measurement of molecules of biological interest by time-resolved fluorescence spectrophotometry is described. Our method is based on the quantification of the Eu3+ chelator 4,7-bis(chlorosulfophenyl)-1,10-phenanthroline-2,9-dicarboxylic acid (BCPDA) in solution in presence of an excess of Eu3+ ions. BCPDA-labeled solid phase complexes obtained by conventional immunoassay procedures are transferred into solution using urea/SDS/Eu3+ as dissociating and fluorescent lanthanide ion reagent. Two 'sandwich-type' assay variants based on the above methodology were realized for the determination of small amounts of fibronectin (FN) in biological fluids. FN is captured from solution by solid phase coated gelatin or a monoclonal antibody, respectively. Rabbit anti-FN antiserum used as second antibody is detected with a biotinylated anti-rabbit IgG antibody. Fluoresence is measured after incubation with streptavidin-BCPDA and dissociation of solid phase complexes as described. Both assays have a detection limit (blank + 3 x SD) of less than 0.5 ng/ml FN, a dynamic range of up to 300 ng/ml, and intraserial coefficients of variation of 4.4 and 6.3%, respectively. Median FN concentrations in saliva of healthy individuals were 104 (gelatin) and 36 ng/ml (double antibody), respectively.

Biochemical markers of hepatic fibrosis

Most liver diseases lead to a pathobiochemical reaction termed liver fibrosis. This is a dynamic process implying different rates of progression or regression. Thus, histological examination of a liver biopsy is essential for a diagnosis but biochemical tests are necessary for assessing the activity of the process and monitoring its evolution. We review the most important constituents of liver connective tissue and the biochemical tests developed for evaluating liver fibrosis. The aminopeptide of type III procollagen is the most widely used parameter: two different radioimmunoassays have been developed with different affinities for the two circulating forms of the molecule. The determination of serum P3P reveals an elevation of blood levels both in acute and chronic liver diseases. In the first, serum P3P is an index of hepatic necrosis and inflammation which correlates with other biochemical parameters. In the second it is an index of active fibrogenesis. Moreover, in primary biliary cirrhosis this parameter is an independent prognostic variable and an important predictor of survival. Other immunoassays exist for different collagen cleavage products, but their clinical value is not established. Laminin and fibronectin are the principal structural glycoproteins in liver. Fibronectin determination does not seem to be of clinical value in liver disease. In contrast, serum laminin correlates with the severity of portal venous pressure in advanced liver disease. Its concentration parallels the severity of varices and may indicate the risk of bleeding. Hyaluronate is a high molecular weight polysaccharide, raised serum concentrations reflect both its increased synthesis by activated fibroblasts and its impaired catabolism by the liver. Thus, it may be useful for evaluating and monitoring the progression of chronic liver disease. The measurement of the activity of prolyl 4-hydroxylase as well as that of lysine oxidase and other enzymes has been proposed, but their clinical value is not sufficiently demonstrated. A panel of tests (e.g., laminin, hyaluronate and the aminopeptide of type III procollagen) seems to be recommended for a biochemical assessment of liver fibrosis in clinical practice.

Variation in epiretinal membrane components with clinical duration of the proliferative tissue

Immunohistochemical investigations were conducted on surgically excised epiretinal membranes to determine how cellular and extracellular components of proliferative vitreoretinopathy membranes change with time. Specimens of less than four months' duration contained a significantly higher proportion of retinal pigment epithelial cells than later membranes. No association was found between membrane duration and the content of collagen subtypes I to IV and laminin, but 'early' specimens contained significantly more fibronectin than did 'late' membranes. Fibronectin and collagens I, III, and IV showed a variable relationship with glial cells and were most consistently associated with retinal pigment epithelial and fibroblast-like cells. These observations may explain some of the surgical features of epiretinal membranes.

Modulatory effects of fibronectin on in vitro lymphocyte responses

In rat studies, fibronectin (Fn), a ubiquitous glycoprotein, is a T-cell mitogen and stimulates the production of interleukin 1 by peritoneal exudate macrophages. In contrast, Fn has no mitogenic activity for human lymphocytes and does not stimulate interleukin 1 release by human peripheral blood mononuclear cells. Fn increases in vitro peripheral blood mononuclear cell phytohemagglutinin responses in normals and patients with active, but not inactive, rheumatoid arthritis. Fn may alter local immunoregulation and play an active role in the rheumatoid synovial lesion.

Distribution of fibronectin and laminin in human thymoma

The distribution of fibronectin and laminin, two extracellular matrix and basement membrane components, was studied in 55 cases of thymoma using immunohistochemistry. The results were compared according to histologic type or clinical stage of the tumor. In addition, electron microscopic observation was done to clarify the extracellular structure of thymoma. Two staining patterns were seen. First, a diffusely or partially intricate network of fibers that contained fibronectin and laminin surrounded tumor cells in 21 out of 55 cases. Most of these cases were spindle cell thymomas and showed low invasive tumors. Second, fibers that contained fibronectin and laminin were restricted only to the septa, blood vessels, and perivascular spaces that did not show a network in the remaining 34 cases. Polygonal cell thymomas showed the latter staining pattern and these were more invasive tumors. We conclude that this network is a characteristic structure of spindle cell thymomas and is related to the invasiveness of the tumor.

Distribution of fibronectin in adenocarcinoma of the lung: classification and prognostic significance

Fibronectin (FN) was investigated in 75 stroma from lung adenocarcinoma patients. Distribution of FN was classified into three patterns based on immunohistochemical evidence: dense, moderate, and sparse distribution. The incidence of the sparse pattern in both stage I and stage III disease was significantly greater in the infiltrating than in the noninfiltrating areas. The patients were divided into two groups, long-term survivors and short-term survivors. In the group with stage I disease, the incidence of the sparse pattern was significantly greater in the infiltrating than in the non-infiltrating areas. In both areas, the incidence of sparse pattern was greater in the short-term than in the long-term survivors. These data suggest that the disappearance of FN reflects the aggressiveness of the tumor and presumably plays an important role in the prognosis of adenocarcinoma of the lung.

Fibronectin in meningococcal sepsis. Correlation with antithrombin III and protein C

Plasma fibronectin was measured with Laurell's immunoelectroassay in 44 patients with meningococcal sepsis. The average value (15.0 +/- 7.9 mg/dl) was lower than that in normal children (27.4 +/- 8.7 mg/dl) (p less than 0.001). Fibronectin in patients correlated positively with antithrombin III (AT-III) values (p less than 0.02), but not with protein C (0.05 less than p less than 0.1). The decrease of fibronectin had no prognostic value. The fibronectin levels were lower in patients with disseminated intravascular coagulation (DIC+), than in those without DIC (DIC-) (p less than 0.02), but were lower in both groups than in a normal control group. A negative correlation between fibronectin and protein C was only present in DIC- patients (r: -0.773 = p less than 0.01). Fibronectin varied independent of AT-III and protein C in DIC+ patients. The study was repeated in 11 patients 24 hours after admission when fibronectin had decreased in 7/11 cases (mean decrease: -2.7 +/- 8.7 mg/dl). This variation correlated in a negative way with AT-III (r: -0.659 = p less than 0.05). In meningococcal sepsis fibronectin decreases very early, even in DIC- patients and its relationship to AT-III and protein C is different, depending on the presence of DIC and on the stage of evolution of the disease.

Secretion of fibronectin by mineral dust-derived alveolar macrophages and activated peritoneal macrophages

The in vitro secretion of fibronectin by rat alveolar macrophages recovered following the intratracheal instillation of various mineral dusts was examined using a competitive enzyme-linked immunoassay (CELIA) method. Cells derived with the fibrogenic dusts DQ12 quartz and UICC crocidolite asbestos had elevated rates of fibronectin secretion when compared ith those derived from titanium dioxide or saline. The in vitro culture of alveolar macrophages with dusts did not lead to elevated rates of fibronectin secretion, suggesting that mechanisms other than the direct interaction between dusts and macrophages may be responsible for elevated rates of fibronectin secretion by cells exposed to fibrogenic dusts. This suggests that fibronectin deposition seen in pneumoconiotic lesions in immunohistochemical studies may in part have been derived from macrophages. Thioglycollate-induced activated mouse peritoneal macrophages secreted significantly less fibronectin than resident peritoneal macrophages, a finding contrasting with those of Tsukamoto et al. [7].

Paucity of fibronectin in invasive lobular carcinoma of breast

Fifty-four cases of invasive carcinoma of breast were immunostained for fibronectin and laminin. They included 36 cases of invasive ductal carcinoma and 18 cases of invasive lobular carcinoma. Although there was some heterogeneity within tumours, it was found that whilst the majority of ductal carcinomas (31/36) had abundant fibronectin at cell/stroma boundaries or diffusely throughout stroma, a substantial proportion of lobular carcinomas (12/18) had very little (P less than 0.001). This difference could not be related to differences in laminin immunoreactivity, which was most commonly scanty or absent in both tumour types. It is postulated that the characteristic infiltration pattern of lobular carcinoma may be attributed in part to paucity of stromal fibronectin.

Elevation of plasma fibronectin and serum amyloid P in autoimmune NZB, B/W, and MRL/1pr mice

The acute-phase proteins, fibronectin (Fn) and serum amyloid P (SAP), are opsonins which by virtue of their adhesive properties may be involved in the glomerular nephritis associated with splenic lupus erythematosus (SLE). Because of their possible involvement in the pathophysiology of lupus, plasma Fn and SAP levels from three strains of autoimmune mice were measured over time to determine if Fn and SAP rose as the mice sickened and renal function degenerated. Baseline levels of Fn and SAP were measured when the mice were between 1.5 and 3 months of age. The characteristic rapid onset of autoimmune disease in MRL/1pr mice was accompanied by a two- to threefold increase in plasma Fn and SAP by Day 100. The B/W mice, which develop autoimmune disease more slowly, did not have a significant increase in plasma Fn and SAP until Day 240. The NZB mice, with the most delayed onset of disease, exhibited a modest but significant elevation of plasma Fn and SAP by Day 360. Histologic examination of the kidneys of B/W and NZB mice indicated that pathological abnormality of the glomeruli and tubules coincided with the elevation of plasma Fn and SAP levels. In contrast, blood samples taken over time from normal BALB/c mice did not possess abnormal levels of Fn or SAP. It appears that elevation of plasma Fn and SAP in the MRL/1 pr, B/W, and NZB mice is related to the onset and severity of autoimmune disease and the subsequent loss of renal function.

The role of inflammation in the development of epiretinal membranes

Single or multiple (3) injections of "Shigella" endotoxin were administered into the rabbit vitreous body to investigate the development of epiretinal membranes following intraocular inflammation. The evaluation included clinical assessment of the resulting traction retinal detachments, together with histological, autoradiographic, immunohistochemical and ultrastructural studies. Traction retinal detachments were found beneath fibroglial epiretinal membranes (being more extensive in eyes which had received 3 endotoxin injections) in the vicinity of the medullary rays, while purely glial membranes occurred over attached peripheral retina. The primary change at the vitreoretinal interface was an elevation of the inner limiting lamina of the retina followed by the extension of glial cells onto the retinal surface. It is postulated that glial cells breach the inner limiting lamina as a sequel to inflammation involving the vitreoretinal interface and form a scaffold upon which fibroblast-like cells migrate.

Proteins of the extracellular matrix in vitreoretinal membranes

Epiretinal and vitreous membranes of different etiology, e.g., in diabetic retinopathy, following retinal detachment, trauma or inflammatory processes, show a similar morphology. The exact composition of the extracellular matrix and the pathogenesis of these membranes remain uncertain. The presence of collagens, type I-IV, laminin, and fibronectin can be shown by means of immunofluorescence with affinity-purified antibodies. Collagen type V was revealed by SDS-polyacrylamide-gel electrophoresis. These proteins of the extracellular matrix have diverse properties and functions in the membranes, as is discussed. Despite great similarities in morphology, there are some differences in the matrix, seemingly dependent upon the etiology of the membrane.

Butyrate effects on growth, morphology, and fibronectin production in PC-3 prostatic carcinoma cells

Sodium butyrate (NaBT) induces differentiation in several transformed cell lines. The present paper describes the effects of NaBT on some transformation-associated parameters in PC-3, a human prostatic carcinoma cell line. NaBT produces a reversible inhibition of cell proliferation, but anchorage-independent growth is more sensitive than monolayer growth. Soft agarose colonies are reduced by over 50% at 0.1 mM, a concentration that hardly affects growth on solid substrata. Monolayer cells respond to NaBT by spreading and flattening, as demonstrated by a combined light and electron microscopic, morphometric technique. After 4 days' exposure to 2 mM NaBT, the average cell covers an area of substratum that is approximately double that covered by control cells. The average cell volume, however, remains unchanged. This flattening is paralleled by an increase in the number of stress fibers, as seen by fluorescence microscopy. Only minor changes are observed in the microtubule and intermediate filament patterns. While control cells contain very little antifibronectin reactive material, substantial amounts of such material appear upon NaBT treatment. The amount of fibronectin increases up to 100-fold in cells exposed to NaBT. The changes observed correspond to a suppression of properties that are generally associated with the malignant phenotype.

Differential expression of fibronectin in a rat histiocytoma: possible role of fibronectin in tumor cell adhesion

The specific role of fibronectin in tumor cells has been investigated using the transplantable histiocytic tumor line AK-5 [A. Khar (1986) J. Natl. Cancer Inst. 76, 871]. These cells, capable of growth as both ascites and solid tumors in rats, can be separated into four subpopulations by buoyant density centrifugation on Percoll. These subpopulations are shown to contain different amounts of fibronectin on the cell surface when studied by immunofluorescent staining followed by cytofluorometric analysis. Cells which contain high amounts of fibronectin can grow both as ascites and as solid tumors while those cells which contain low amounts of fibronectin cannot grow as solid tumors but can grow as ascitic tumors. Pretreatment of high-fibronectin-containing cells with anti-fibronectin antibody abolished their capacity to grow as solid tumors; however, the cells retained their capacity to grow as ascitic tumors. These results have been discussed with reference to the specific role of fibronectin in tumor-forming cells.

Plasma fibronectin concentrations in healthy newborns and in children

Plasma fibronectin (FN) concentrations were measured by an immunonephelometric method in cord blood from 76 healthy newborns (45 full term and 31 preterm), in 181 healthy children, from 1 month-15 years old, divided by age into seven groups and in 81 control adults. FN levels in newborns were 35% of those of adults. There was no difference between plasma FN in term and preterm (gestational age greater than 30 weeks) infants. Preterm newborns below the gestational age of 30 weeks showed particularly low FN levels. No clear correlation was seen with birth weight. In the child population, a strong increase in FN values was noted in the first 6 months of life, rising to 65% of the normal adult values. No further increase occurred until puberty.

Glial fibrillary acidic protein, vimentin and fibronectin in primary cultures of human glioma and fetal brain

The expression of glial fibrillary acidic protein (GFAP), vimentin and fibronectin (Fn) was studied in cells cultured from human glioma and fetal brain by indirect immunofluorescence (IIF) microscopy and multiple labelling experiments. In the primary cultures a major part (20%-70%) of the cells usually displayed both GFAP and vimentin and the rest of the cells only vimentin. A prominent variation in GFAP and vimentin fluorescence intensity sometimes made interpretation of double IIF stainings difficult. However, occasional GFAP-positive cells appeared vimentin negative in primary glioma cultures, whereas in fetal brain primary cultures cells that were preferentially GFAP positive also showed at least a weak vimentin immunoreactivity. Only a fraction of the cells, roughly corresponding to the GFAP-negative cells, were Fn positive in the primary cultures. As judged by double IIF, the GFAP-positive cells were usually Fn negative, while the Fn-positive cells were vimentin positive. This could also be demonstrated in triple IIF experiments. During serial subcultivation the amount of cells expressing GFAP decreased, while the number of Fn-positive cells increased. By the third to fourth passage GFAP positivity was usually lost, all cells expressed vimentin and most cells also Fn. The results of the present study demonstrate a general coexpression of GFAP and vimentin in cultured astroglial cells, in addition to cells expressing only vimentin. Interestingly, occasional glioma cells seem to contain GFAP as the only intermediate filament protein as detected by immunocytochemistry.(ABSTRACT TRUNCATED AT 250 WORDS)

Plasma fibronectin levels in normal pregnancy and pre-eclampsia: a preliminary report

Fibronectin, a major component of the extracellular matrix and basement membranes throughout the body, is thought to maintain the integrity of both the reticulo-endothelial system and microvasculature. In this study, plasma fibronectin levels were assayed by nephelometry in nine pre-eclamptic gravid women, nine normotensive gravid women and ten non-gravid women. The mean plasma fibronectin level (+/-S.E.M.) in pre-eclamptic gravidas (1687 +/- 101 micrograms/ml) is significantly higher than that of either normotensive gravidae (1129 +/- 99 micrograms/ml) or non-gravid women (897 +/- 60 micrograms/ml). Although the mechanism for elevated levels of plasma fibronectin in patients with pre-eclampsia is not clear, it may serve as an early biochemical marker for this disorder.

An immunohistochemical study of fibronectin in human osteoarthritic and disease free articular cartilage

Fibronectin is a minor component of cartilage connective tissue matrix, which is reported to accumulate in increased amounts in osteoarthritis. The presence of raised levels of fibronectin in human osteoarthritic cartilage by immunoperoxidase localisation is confirmed. Residual femoral head articular cartilage from 17 patients with osteoarthritis contained variable but substantial amounts of fibronectin. This was localised mainly in a band within the matrix of the surface zone. No significant deposits of fibronectin were found in this or any other area of the normal specimens. Intracellular fibronectin was identified in some cells of the surface zone, indicating that it was, in part, synthesised locally. The presence and distribution of locally produced fibronectin in osteoarthritic cartilage suggest that its synthesis is a response by chondrocytes to changes in the cartilage matrix.

Fibronectin in human hepatocellular carcinoma (HCC) and HCC cell lines

The localization of fibronectin (FN) in human hepatocellular carcinoma (HCC) was studied in thirty-six HCC tumors (19 autopsy and 17 surgical specimens), two xenografted tumors of HCC to BALB/c mice and three HCC cell lines. The synthesis of FN was also examined in three HCC cell lines. FN was demonstrated on the endothelial surface of the blood spaces of cancerous tissue. Cytoplasmic and intercellular localization of FN was also observed. But there was no correlation between the localization pattern of FN and metastasis. In the two xenografted HCC tumors, FN was found in association with the blood vessels of the tumor tissue and between the HCC tumor cells. In all 3 HCC cell lines, FN was localized on the surface and in the cytoplasm of some HCC cells. FN was detected in the serum-free culture media of three HCC cell lines by immunoelectroblotting. The electrophoretic pattern of FN synthesized by these cell lines was different from that of plasma-FN and resembled that of cellular-FN synthesized by normal liver fibroblasts.

Plasma fibronectin and microvascular damage in essential mixed cryoglobulinaemia

Plasma fibronectin (FN) was measured in 17 patients with essential mixed cryoglobulinaemia (EMC) and in 17 normal subjects by single radial immunodiffusion (RID) and enzyme-linked immunosorbent assay (ELISA). In 9 patients the presence of FN in the cryoprecipitates was also assessed by immunoblotting. In the EMC group, plasma FN levels were significantly lower than in control subjects, using both methods, and FN was constantly demonstrated in EMC cryoprecipitates. Capillaroscopic observation of the capillary bed in skin and bulbar conjunctiva, performed in all cases, showed severe alterations of microcirculation in EMC patients. A negative correlation between plasma FN and capillaroscopic abnormalities of skin capillaries was observed. These data support the hypothesis that plasma fibronectin plays a role in the pathogenesis of systemic vasculitis in EMC.

Laminin and fibronectin in adenoid cystic carcinoma

The distribution of fibronectin and laminin was examined by immunohistochemistry in 11 adenoid cystic breast carcinomas, six adenoid cystic carcinomas of mouth and salivary gland, and six cribriform ductal breast carcinomas. Both proteins were present lining cystic lumina and around tumour islands in all the adenoid cystic breast carcinomas and in five of six salivary gland tumours. Abundant laminin and fibronectin were dispersed among adenoid cystic tumour cells arranged in sheets. One adenoid cystic carcinoma from buccal mucosa showed a transition from a cribriform tumour positive for both fibronectin and laminin to a cribriform tumour negative for fibronectin and laminin to undifferentiated carcinoma. Fibronectin and laminin seemed to disappear simultaneously from tumour cell surfaces. Another adenoid cystic carcinoma from buccal mucosa was negative for fibronectin and laminin from the time of initial biopsy. This was the only tumour that gave rise to disseminated metastases, resulting in the death of the patient within two years of surgery. In cribriform invasive ductal breast carcinomas the linings of cystic lumina were always negative for fibronectin and laminin. Varying quantities were present at the tumour boundaries. We suggest that staining for fibronectin and laminin may be a valuable aid to the diagnosis of adenoid cystic carcinomas and that the absence of these proteins may have important prognostic implications.

The effect of proteolytic degradation of plasma fibronectin on the responses of functional and immunometric assays for intact fibronectin

Numerous studies have been made into the nature and importance of altered levels of plasma fibronectin seen in a range of clinical disorders. However, fibronectin is highly sensitive to the proteolytic degradation which may accompany some of these conditions. The influence of such degradation on the assays used is frequently unknown. We have investigated the effects of controlled protease degradation on the responses of an electroimmuno and a functional assay, using purified fibronectin. Tryptic digestion influenced the assays more than thrombin, in relation to the degree of breakdown. Both enzymes reduced the functional (gelatin-binding) activity whilst tryptic cleavage increased the apparent concentration by electroimmunoassay. The findings demonstrate that certain assays may be inappropriate for those clinical conditions where levels of intact fibronectin are of most interest. It is also necessary, then, to determine the degree of fibronectin breakdown when measuring pathological levels.