elastin and Glaucoma--Open-Angle

The genetic basis of pseudoexfoliation (PEX) syndrome, the most common identifiable cause of open-angle glaucoma, is steadily being elucidated. This review summarizes the recent advances on genetic risk factors for PEX syndrome/glaucoma and their potential functional implications in PEX pathophysiology.. As of today, seven loci associated with the risk of PEX surpassing genome-wide significance have been identified by well-powered genome-wide association studies and sequencing efforts. LOXL1 (lysyl oxidase-like 1) represents the major genetic effect locus, although the biological role of common risk variants and their reversed effect in different ethnicities remain an unresolved problem. Rare protein-coding variants at LOXL1 and a single noncoding variant downstream of LOXL1 showed no allele effect reversal and suggested potential roles for elastin homeostasis and vitamin A metabolism in PEX pathogenesis. Other PEX-associated genetic variants provided biological insights into additional disease processes and pathways, including ubiquitin-proteasome function, calcium signaling, and lipid biosynthesis. Gene-environment interactions, epigenetic alterations, and integration of multiomics data have further contributed to our knowledge of the complex etiology underlying PEX syndrome and glaucoma.. PEX-associated genes are beginning to reveal relevant biological pathways and processes involved in disease development. To understand the functional consequences and molecular mechanisms of these loci and to translate them into novel therapeutic approaches are the major challenges for the future.

Topics: Amino Acid Oxidoreductases; Elastin; Exfoliation Syndrome; Genetic Predisposition to Disease; Genome-Wide Association Study; Glaucoma, Open-Angle; Humans; Polymorphism, Single Nucleotide; Risk Factors; Vitamin A

Several lines of evidence, such as ultrastructural signs for activated fibrillogenesis and excessive production of elastic microfibrillar components in the anterior segment of the eye and throughout the body, indicate that exfoliation syndrome (XFS) is an elastic microfibrillopathy, leading to the accumulation of an abnormal extracellular fibrillar material (XFM). The upregulation of elastic microfibrillar components is paralleled by the selective upregulation of the cross-linking enzyme lysyl oxidase-like 1 (LOXL1) in the early phase of the disease, suggesting that LOXL1 participates in the stabilization of newly synthesized elastic proteins and finally in the stable accumulation of XFM. Whereas the excessive production of elastic proteins rises from early to late XFS stages, possibly mediated by increasing fibrogenic stimuli in the aqueous humor, LOXL1 is downregulated in late stages of the disease by as yet unknown mechanisms, possibly leading to the well-documented elastotic matrix alterations characteristic of eyes with late stage XFS. Several studies indicate complex changes of the proteolytic balance in the anterior segment of XFS eyes, characterized primarily by decreased matrix metalloproteinase-2 activity, the major aqueous matrix metalloproteinase, potentially leading to a shift from appropriate matrix turnover to progressive matrix accumulation. In contrast, in nearly all tissues of the posterior segment, XFM seems to be absent and differential gene expression is confined to the lamina cribrosa, characterized by a stage-independent, primary, and XFS-specific downregulation of LOXL1 and elastic components in XFS eyes. Concomitant with this deficiency, the laminar elastic fiber network displays prominent ultrastructural alterations, which may lead to increased vulnerability to glaucomatous damage. Various growth factors, stress conditions, or dietary factors have been supposed to potentially influence the manifestation of the disease. However, in spite of increasing knowledge, the pathogenetic factors initiating the abnormal matrix process still remain elusive. Such information would be critical for our understanding of disease progression and would disclose new options for pharmaceutical intervention at the onset of the disease.

Topics: Anterior Eye Segment; Elastin; Exfoliation Syndrome; Extracellular Matrix; Extracellular Matrix Proteins; Glaucoma, Open-Angle; Humans; Microfibrils

Pseudoexfoliation syndrome (PXS) is a systemic condition with eye manifestations. In the eye, pseudoexfoliation material deposits on various structures of the anterior segment. The nature of this material is mostly fibrillar with fibers made up of microfibrils and coated with amorphous material. The composition of these fibrils is diverse and includes basement membrane components as well as enzymes involved in extracellular matrix maintenance. Pseudoexfoliation is the most common cause of secondary open-angle glaucoma (pseudoexfoliation glaucoma, PXG) worldwide. The goal of this review is to summarize our knowledge on the genetics of this systemic disorder and its resultant ocular manifestations. PXS familial aggregation suggests genetic inheritance. PXS has been strongly associated with single nucleotide polymorphisms (SNPs) of the lysyl oxidase-like 1 (LOXL1) gene on chromosome 15q24.1. Two of these SNPs confer a higher than 99% population attributable risk for PXS and PXG in the Nordic population; however, they carry different risks in different populations. The high risk haplotypes also vary among different populations. LOXL1 is one of group of the enzymes involved in the cross-linking of collagen and elastin in the extracellular matrix. Its function in connective tissue maintenance has been confirmed in mice; however, its actual role in PXS remains unclear. Contactin-associated protein-like 2 also has a strong genetic association with PXS in a German cohort and is an attractive candidate molecule. It encodes for a protein involved in potassium channel trafficking. Other candidate genes linked to PXS include lysosomal trafficking regulator, clusterin, adenosine receptors, matrix metalloproteinase-1 (MMP1), and glutathione transferase. These genes may be modifying genes for development of PXS and PXG.

Topics: Amino Acid Oxidoreductases; Chromosomes, Human, Pair 15; Clusterin; Collagen; Elastin; Exfoliation Syndrome; Extracellular Matrix; Eye; Gene-Environment Interaction; Glaucoma, Open-Angle; Glutathione Transferase; Haplotypes; Humans; Matrix Metalloproteinase 1; Polymorphism, Single Nucleotide; Receptor, Adenosine A3

Primary open angle glaucoma (POAG), the most common form of glaucoma, is characterized by irreversible loss of axons from the optic nerve. The site of damage to the axons is at the level of the lamina cribrosa in the optic nerve head. It has been hypothesized that structural and biochemical abnormalities in the extracellular matrix (ECM) of the lamina cribrosa underlie the progressive compressive and remodelling of this connective tissue in glaucoma. In this review, we present evidence of specific changes in collagen and elastic fibers, major ECM components in the lamina cribrosa of glaucomatous eyes.

Topics: Collagen; Elastin; Extracellular Matrix; Fluorescent Antibody Technique; Glaucoma, Open-Angle; Glial Fibrillary Acidic Protein; Humans; Microscopy, Immunoelectron; Optic Disk; Optic Nerve

Abnormal human trabecular meshwork (HTM) cell function and extracellular matrix (ECM) remodeling contribute to HTM stiffening in primary open-angle glaucoma (POAG). Most current cellular HTM model systems do not sufficiently replicate the complex native three dimensional (3D) cell-ECM interface, limiting their use for investigating POAG pathology. Tissue-engineered hydrogels are ideally positioned to overcome shortcomings of current models. Here, we report a novel biomimetic HTM hydrogel and test its utility as a POAG disease model. HTM hydrogels were engineered by mixing normal donor-derived HTM cells with collagen type I, elastin-like polypeptide and hyaluronic acid, each containing photoactive functional groups, followed by UV crosslinking. Glaucomatous conditions were induced with dexamethasone (DEX), and effects of the Rho-associated kinase (ROCK) inhibitor Y27632 on cytoskeletal organization and tissue-level function, contingent on HTM cell-ECM interactions, were assessed. DEX exposure increased HTM hydrogel contractility, f-actin and alpha smooth muscle actin abundance and rearrangement, ECM remodeling, and fibronectin deposition - all contributing to HTM hydrogel condensation and stiffening consistent with glaucomatous HTM tissue behavior. Y27632 treatment produced precisely the opposite effects and attenuated the DEX-induced pathologic changes, resulting in HTM hydrogel relaxation and softening. For model validation, confirmed glaucomatous HTM (GTM) cells were encapsulated; GTM hydrogels showed increased contractility, fibronectin deposition, and stiffening vs. normal HTM hydrogels despite reduced GTM cell proliferation. We have developed a biomimetic HTM hydrogel model for detailed investigation of 3D cell-ECM interactions under normal and simulated glaucomatous conditions. Its bidirectional responsiveness to pharmacological challenge and rescue suggests promising potential to serve as screening platform for new POAG treatments with focus on HTM biomechanics.

Topics: Actins; Aged, 80 and over; Amides; Biomimetic Materials; Cytoskeletal Proteins; Dexamethasone; Elastin; Enzyme Inhibitors; Eye Proteins; Female; Gene Expression Regulation; Glaucoma, Open-Angle; Glucocorticoids; Glycoproteins; Humans; Hydrogels; Immunohistochemistry; Models, Biological; Pyridines; Real-Time Polymerase Chain Reaction; rho-Associated Kinases; Tissue Engineering; Trabecular Meshwork

To test the hypothesis that a primary disturbance in lysyl oxidase-like 1 (LOXL1) and elastin metabolism in the lamina cribrosa of eyes with pseudoexfoliation syndrome constitutes an independent risk factor for glaucoma development and progression.. Observational, consecutive case series.. Posterior segment tissues obtained from 37 donors with early and late stages of pseudoexfoliation syndrome without glaucoma, 37 normal age-matched control subjects, 5 eyes with pseudoexfoliation-associated open-angle glaucoma, and 5 eyes with primary open-angle glaucoma (POAG).. Protein and mRNA expression of major elastic fiber components (elastin, fibrillin-1, fibulin-4), collagens (types I, III, and IV), and lysyl oxidase crosslinking enzymes (LOX, LOXL1, LOXL2) were assessed in situ by quantitative real-time polymerase chain reaction, (immuno)histochemistry, and light and electron microscopy. Lysyl oxidase-dependent elastin fiber assembly was assessed by primary optic nerve head astrocytes in vitro.. Expression levels of elastic proteins, collagens, and lysyl oxidases in the lamina cribrosa.. Lysyl oxidase-like 1 proved to be the major lysyl oxidase isoform in the normal lamina cribrosa in association with a complex elastic fiber network. Compared with normal and POAG specimens, lamina cribrosa tissues obtained from early and late stages of pseudoexfoliation syndrome without and with glaucoma consistently revealed a significant coordinated downregulation of LOXL1 and elastic fiber constituents on mRNA and protein level. In contrast, expression levels of collagens and other lysyl oxidase isoforms were not affected. Dysregulated expression of LOXL1 and elastic proteins was associated with pronounced (ultra)structural alterations of the elastic fiber network in the laminar beams of pseudoexfoliation syndrome eyes. Inhibition of LOXL1 interfered with elastic fiber assembly by optic nerve head astrocytes in vitro.. The findings provide evidence for a pseudoexfoliation-specific elastinopathy of the lamina cribrosa resulting from a primary disturbance in LOXL1 regulation and elastic fiber homeostasis, possibly rendering pseudoexfoliation syndrome eyes more vulnerable to pressure-induced optic nerve damage and glaucoma development and progression.

Topics: Aged; Aged, 80 and over; Amino Acid Oxidoreductases; Aminopropionitrile; Astrocytes; Cells, Cultured; Collagen; Disease Progression; Disease Susceptibility; Elastic Tissue; Elastin; Enzyme Inhibitors; Exfoliation Syndrome; Extracellular Matrix; Extracellular Matrix Proteins; Female; Fibrillin-1; Fibrillins; Fluorescent Antibody Technique, Indirect; Gene Expression Regulation, Enzymologic; Glaucoma, Open-Angle; Humans; Male; Microfilament Proteins; Optic Disk; Real-Time Polymerase Chain Reaction; Risk Factors; Tissue Donors; Transforming Growth Factor beta1

To analyze the vasculature and extracellular matrix changes in the prelaminar region (PreLR) of the optic nerve head (ONH) and in the peripapillary sclera of eyes with primary open-angle glaucoma (POAG) and age-matched control eyes.. In histologic sagittal sections of 46 eyes with POAG and 45 control eyes (donor ages, 20-96 years), the peripapillary sclera and penetrating vessels were investigated ultrastructurally and with antibodies against elastin, podocalyxin, and α-actin. Within the PreLR, the number and density of capillaries and the thickness of their connective tissue sheaths (CTSs) were quantified. The composition of the CTS was analyzed by using antibodies against collagen types I, III, IV, and VI, and elastin. Areas within the PreLR containing capillaries with thick or thin CTSs were determined.. There were no glaucomatous changes in the peripapillary elastic fibers and in the arterial capillaries in the periphery of the PreLR. In the center of the PreLR, the capillaries gained a CTS that was significantly thicker in POAG eyes than in control eyes, and the area containing capillaries with thick CTSs was significantly larger. These data did not correlate with axon counts.. Lack of glaucomatous changes in elastic fibers of the scleral suspension of the ONH seems to prevent occlusion of penetrating vessels. In the PreLR, thickening of the capillary CTS and enlargement of the area containing capillaries with thickened CTS could increase diffusion time and may impair nutrition of the neuronal tissue.

Topics: Actins; Adult; Aged; Aged, 80 and over; Arterioles; Capillaries; Ciliary Arteries; Connective Tissue; Elastic Tissue; Elastin; Extracellular Matrix; Female; Fluorescent Antibody Technique, Indirect; Glaucoma, Open-Angle; Humans; Male; Microscopy, Fluorescence; Middle Aged; Optic Disk; Optic Nerve Diseases; Sclera; Sialoglycoproteins; Young Adult

Exfoliation glaucoma (XFG) is the commonest identifiable cause of secondary open-angle glaucoma worldwide, characterized by the deposition of fibrillar proteins in the anterior segment of the eye. We investigated LOXL1 gene variants previously identified to confer susceptibility to XFG in a Utah Caucasian cohort. After a standard eye examination protocol we genotyped SNPs rs2165241and rs3825942 in 62 XFG or exfoliation syndrome (XFS) patients and 170 normal controls. Genotype frequency distribution, odds ratios (ORs) and population attributable risks were calculated for the risk alleles. The SNP rs2165241 was significantly associated with XFG and XFS (p = 4.13 x 10(-9)) for an additive model, OR(het) = 4.42 (2.30-8.50), OR(hom) = 34.19 (4.48-261.00); T allele: 83.1% in cases versus 52.4% in controls). Significant association was also found for rs3825942: (p = 1.89 x 10(-6)). Our findings confirm genetic association of LOXL1 with XFG and XFS and implicate a potential role of cross linking of elastin in the pathogenesis of XFG. This information will potentially guide glaucoma monitoring efforts by targeting individuals whose genetic profiles put them at higher risk for XFG.

Topics: Amino Acid Oxidoreductases; Cohort Studies; DNA Primers; Elastin; Exfoliation Syndrome; Female; Genetic Predisposition to Disease; Genotype; Glaucoma, Open-Angle; Humans; Male; Odds Ratio; Polymorphism, Single Nucleotide; Utah; White People

Topics: Amino Acid Oxidoreductases; Elastin; Exfoliation Syndrome; Glaucoma, Open-Angle; Humans; Polymorphism, Single Nucleotide

Elastin is a major component of the extracellular matrix (ECM) of the lamina cribrosa in the optic nerve head in humans and nonhuman primates. The lamina cribrosa appears to be the site of damage to the retinal ganglion cell axons in glaucomatous optic neuropathy, characterized in many patients by elevated intraocular pressure (IOP). Type 1B astrocytes are the major cell type in the lamina, synthesize elastic fibers during development, express increased elastin mRNA, and synthesize abnormal elastin in glaucoma. In this study, we determined the effect of elevated hydrostatic pressure on the synthesis of elastin by type 1B astrocytes in culture. Type 1B astrocytes were exposed to gradients of hydrostatic pressure and tested for proliferation, morphology, synthesis, and deposition of elastin. Trichloroacetic acid (TCA) and immunoprecipitation of radiolabeled protein determined total new protein and elastin synthesis. Proteins from the conditioned media were analyzed by Western blot. Levels of elastin mRNA were determined by in situ hybridization. Cell proliferation increased approximately 2-fold after exposure to pressure for one day, approximately 5-fold after 3 and 5 days of exposure to pressure. Confocal and electron microscopic cytochemistry showed a marked increase in intracellular elastin in astrocytes exposed to pressure, as compared with controls. Intracellular elastin was associated with the RER-Golgi region and with the cytoskeleton. Total protein and elastin synthesis increased significantly (P < 0.05) at 3- and 5-day exposure to pressure, as well as the level of elastin mRNA. Elastin protein in the media increased with the level of pressure. These results indicate that hydrostatic pressure stimulates type 1B astrocytes to synthesize and secrete soluble elastin into the media. In glaucoma, type 1B astrocytes may respond to IOP-related stress with increased expression of elastin and formation of elastotic fibers leading to loss of elasticity and tissue remodeling.

Topics: Adolescent; Adult; Astrocytes; Cell Division; Cell Size; Cells, Cultured; Child; Culture Media, Conditioned; Elastin; Extracellular Matrix; Glaucoma, Open-Angle; Glial Fibrillary Acidic Protein; Humans; Hydrostatic Pressure; Middle Aged; Optic Disk; Optic Nerve Diseases; RNA, Messenger; Stress, Mechanical

To understand transforming growth factor-beta(1) (TGF-beta(1)) inducing cultured human trabecular cells (HTCs) to produce elastin and to approach the effect of resistance of aqueous outflow in the pathogenesis and mechanism of primary open angle glaucoma (POAG).. Trabecular meshwork's specimens were collected from twelve normal eyeballs of six human donors under six years of age within 24 hours after death. HTCs were primarily cultured and subcultured. Cultured cells were observed under light and electron microscopes. Laminin (LN) and IV collagen (IV C) in extracellular matrix (ECM) were immunohistochemically stained by S-P method. The third passage confluent cells after two weeks were divided into three groups: control group, TGF-beta(1) group and neutralizing antibody of TGF-beta(1) group. Concentration of neutralizing antibody of TGF-beta(1) was 30 microg/ml. After culturing for two weeks, elastin in the media of three groups was respectively determined by western blotting from sodium dodecylsulfate-polyacrylamide gel electrophoresis using anti-human aortic alpha-elastin rabbit serum, biotin conjugated goat anti-rabbit IgG and anti-biotin conjugated horse radish peroxidase.. Cultured HTCs were identified from cultured cell's growing characteristics, morphological features under light and electron microscopes, and stained peculiarities of LN and IV C in ECM. With western blotting, elastin in the control group was not detected, elastin in TGF-beta(1) group was detected, and elastin in neutralizing antibody of TGF-beta(1) group was not detected.. TGF-beta(1) induces cultured HTCs to produce elastin, which the neutralizing antibody of elastin can antagonize; the increase of the amount of elastin may aggravate its stacking in ECM and increase the resistance of aqueous outflow in trabecular meshwork, leading to the occurrence of glaucoma.

Topics: Cells, Cultured; Child, Preschool; Elastin; Extracellular Matrix; Glaucoma, Open-Angle; Humans; Infant; Infant, Newborn; Trabecular Meshwork; Transforming Growth Factor beta; Transforming Growth Factor beta1

To compare quantitative and qualitative differences in elastin content in the optic nerve heads of glaucomatous and control human eyes.. Transmission electron microscopy and quantitative histomorphometry on ten control and ten glaucomatous eyes.. Elastin fiber complexes in the control lamina cribrosa were smaller and more numerous than in the insertion zone of the sclera immediately surrounding the lamina. Although the density of elastin fibers in the normal lamina was twice that of the insertion zone (P = 0.004), the percent area of the connective tissue matrix occupied by elastin was the same for both zones (P > 0.4). There was no difference between control and glaucomatous eyes in the quantified parameters of elastin content or in the ultrastructure of elastin between control and glaucomatous eyes.. The authors demonstrated for the first time that elastin in the normal lamina consists of fibers of smaller diameter than in the adjacent sclera, although the total amount of elastin is similar in both locations. This may provide maximum viscoelasticity within the limited connective tissue beam area of the lamina. Despite using a large number of specimens, the authors again found no differences between normal and glaucomatous eyes in the number or ultrastructural appearance of elastin fibers.

Topics: Aged; Elastin; Female; Glaucoma, Open-Angle; Humans; Image Processing, Computer-Assisted; Male; Optic Disk; Optic Nerve; Photography; Reproducibility of Results

Pseudoexfoliation syndrome is characterized by the presence of glycoprotein fibers in ocular and extraocular tissues, and often is associated with glaucoma. Pseudoexfoliation material may be associated closely with elastic microfibrillar-associated glycoprotein as well as elastin.. Four optic nerve heads of two patients with pseudoexfoliation syndrome and glaucoma were examined using electron microscopy and immunogold detection of elastin. Optic nerve heads from healthy age-matched individuals and patients with primary open-angle glaucoma were used for comparisons.. In all eyes with pseudoexfoliation and glaucoma, there was marked and widespread elastosis in the connective tissue of the lamina cribrosa. Elastotic fibers appeared as large and irregular aggregates of electron-dense material labeled with anti-elastin antibody. Abundant microfibrils were interspersed in the elastotic aggregates, whereas no typical pseudoexfoliation fibers were observed. In contrast, there were less elastotic fibers in the lamina cribrosa from patients with primary open-angle glaucoma compared with pseudoexfoliation glaucoma. Other changes of extracellular matrix were similar to those observed in primary open-angle glaucoma: decreases in collagen fiber density, presence of basement membranes not associated with cell surfaces, and abundant bundles of microfibrils not labeled with elastin antibody. The elastic fibers appeared normal in other locations within the optic nerves of patients with pseudoexfoliation glaucoma, including in the pial septa and blood vessels of the retrolaminar myelinated optic nerve.. The authors' findings demonstrate marked and site-specific elastosis in the lamina cribrosa of patients with pseudoexfoliation syndrome with glaucoma, suggesting an abnormal regulation of elastin synthesis and/or degradation in the optic nerve of patients with this disease.

Topics: Aged; Connective Tissue; Elastic Tissue; Elastin; Exfoliation Syndrome; Female; Glaucoma; Glaucoma, Open-Angle; Humans; Immunohistochemistry; Male; Microscopy, Immunoelectron; Optic Disk; Sclera

The aim of this study was to determine the location of elastin in the extracellular material and to estimate the influence of porcine pancreatic elastase-1 (PPE) on the elastin in human trabecular tissue. Trabecular tissues obtained from normal post-mortem eyes and trabeculectomy specimens of primary open angle glaucoma (POAG) were used in this study. The tissues were embedded in Lowicryl K4M and sectioned for electron microscopy. First, the sections were subjected to protein A-gold immunohistochemical staining to determine the location of elastin in the tissues. Second, the sections were exposed to PPE, before immunostaining, to evaluate the change of immunolocalization of the gold particles in the tissue. The results were as follows. In POAG specimens, gold particles indicating the presence of elastin were located in the area of fine fibrillar-like material in the subendothelial layers of Schlemm's canal in POAG specimens. In normal eyes, few gold particles were localized in the area. The density of gold particles in the area was reduced by PPE in POAG specimens. These results show that elastin is localized in the area of fine fibrillar-like material in the subendothelial layers of Schlemm's canal of POAG, and that PPE dissolves the elastin in the area.

Topics: Aged; Aged, 80 and over; Animals; Elastin; Glaucoma, Open-Angle; Humans; Immunohistochemistry; Middle Aged; Pancreatic Elastase; Swine; Trabecular Meshwork

Elastin fibers in the lamina cribrosa of glaucoma eyes have a curled appearance when the tissue is fixed at atmospheric pressure. To evaluate the effect of preparation conditions on elastin appearance, we set the eye pressure at one of four levels during tissue fixation in 18 glaucoma and 16 normal eyes. Glaucomatous damage was associated with an abnormal appearance of elastin at each pressure level. The majority of glaucoma eyes (11/18) had curled elastin profiles. In glaucoma eyes with definite nerve damage, elastin was graded moderately or severely abnormal in 47% (7/15), while in normal controls the rate of similar curling was 6% (1/16). The severity of abnormal elastin appearance was lower in glaucoma eyes that were fixed and frozen at higher intraocular pressures, but the difference was not statistically significant.

Topics: Elastin; Extracellular Matrix; Female; Glaucoma, Open-Angle; Humans; Intraocular Pressure; Male; Optic Disk

The extracellular materials (ECMs) in the trabecular meshwork (TM) are thought to play a crucial role in aqueous outflow resistance. Immunohistochemical localization of elastin, one of the major ECMs in the normal and glaucomatous human TM, was examined ultrastructurally.. Eight normal eye bank eyes and 16 trabeculectomy specimens of primary open angle glaucoma (POAG, 11 eyes from 8 cases), congenital glaucoma (2 eyes from 1 case), and juvenile glaucoma (3 eyes from 2 cases) were embedded in Lowicryl K4M at low temperature. The distribution of elastin was studied by the protein A-gold technique.. In normals, the gold particles indicating the antigenic sites for elastin existed mainly in the central amorphous element of the elastic-like fibers, and a few gold particles were observed within the area containing fine granular-like material and fine fibrillar-like material. No labeling was observed in cellular materials or other ECMs. In congenital and juvenile glaucoma, labeling was similar to that observed in normals. In POAG specimens compared to normals, there was an increased amount of elastin-bound immunogold particles along the inner canal endothelium. The increased gold particles, which did not have a fibrillar arrangement and were not enclosed by electron-dense microfibrils, were found within the area containing fine fibrillar-like material. However, labeling within the elastic-like fibers was similar to that observed in normals.. Under electron microscopy, elastin could be localized in the normal and glaucomatous human TM. The results of this investigation suggest that elastin may play an important role in the etiology of POAG.

Topics: Adult; Aged; Aged, 80 and over; Bacterial Proteins; Child, Preschool; Elastin; Glaucoma; Glaucoma, Open-Angle; Gold Colloid; Humans; Immunohistochemistry; Microscopy, Immunoelectron; Middle Aged; Trabecular Meshwork; Trabeculectomy

An electron microscopy study on the distribution of elastin in the trabecular meshwork of normal human eyes and in that of eyes with primary open angle glaucoma (POAG) was done using a protein-A gold immunohistochemical method with antiserum to either alpha-elastin or tropoelastin. Four types of elastic fibers were found to have elastin: (1) elastic-like fibers without the sheath, (2) fibers surrounded with a sheath of periodic structure, (3) fibers surrounded with fine granular-like material, and (4) connecting fibrils. No individual differences were observed in the labeling for these four types of elastic fibers. Antigenic sites against elastin of the elastic fibers were observed mainly in the low electron density amorphous elements. In the subendothelial layer of Schlemm's canal of the eyes with POAG, a marked increase of elastin was noted within the area containing fine fibrillar-like material. This phenomenon did not occur in age-matched normal eyes. The results suggest that elastin plays an important role in the development of POAG.

Topics: Elastin; Glaucoma, Open-Angle; Humans; Immunohistochemistry; Microscopy, Electron; Trabecular Meshwork

The etiology, pathogenesis and mechanism of optic nerve damage in primary open angle glaucoma (POAG) and low tension glaucoma (LTG) were investigated by experimental glaucoma in monkey and by follow-up studies of many patients over 15 years, by pathohistological and immunohistochemical analysis. 1) LTG was proved to be a real glaucoma, showing pressure-dependent optic nerve damage. The pathological entity was a primary weakness of the lamina cribrosa (LC), and therefore even normal pressure could deform the LC. Due to backward distortion of LC the channels were disarranged and twisted, inducing mechanical optic nerve damage. There was no active vascular damage or vascular constriction at the site of the optic nerve damage. The filling defects of the advanced glaucomatous optic disc were not the cause of optic nerve damage, but the result of regressive vascular change after axon bundle loss. Splinter hemorrhage of the optic disc might be the result of the same process. 2) The weakness of LC might be induced by the abnormal metabolism of the extracellular matrix of the LC. 3) To arrest the progressive optic nerve damage in LTG, the intraocular pressure (IOP) should be maintained under 12, or ideally, 10 mmHg. 4) The optic nerve damage in POAG was not only pressure-dependent, but also dependent on the weakness of the LC, as in the case of LTG. In the early stage the IOP should be under 19 mmHg, in the advanced stage under 14 mmHg in order to arrest progression for over 15 years. 5) In advanced experimental glaucoma of monkeys, the LC showed reduction of elastin, fragmentation of collagen, and change of proteoglycans. 6) As in the LC, the trabecular meshwork also showed abnormal metabolism and abnormal deposits on the extracellular matrix in POAG, and LTG as well. 7) POAG and LTG might belong to the same family in which common abnormal metabolism of LC and trabecular meshwork induce various clinical features.

Topics: Adolescent; Adult; Aged; Aged, 80 and over; Animals; Anterior Eye Segment; Child; Child, Preschool; Collagen; Elastin; Glaucoma; Glaucoma, Open-Angle; Humans; Infant; Intraocular Pressure; Macaca; Male; Middle Aged; Optic Nerve; Proteoglycans

The elastic fiber consists of several components: a central core of alpha-elastin and a microfibrillar sheath containing three components: fibrillin, microfibril-associated glycoprotein, and a 35-kD protein with amine oxidase activity. Elastin is a major component of the elastic fibers of the extracellular matrix (ECM) of the lamina cribrosa, and elastic fibers undergo marked changes in primary open-angle glaucoma (POAG). These changes, as demonstrated previously, include loss and fragmentation of elastic fibers at the bottom of the glaucomatous cup and disorganization in the peripheral walls of the cup. The author characterized the changes in elastic fibers with age and in POAG at the ultrastructural level, using colloidal gold immunostaining and anti-human alpha-elastin antibody. In fetal eyes, there was no detectable elastin in the ECM of the lamina cribrosa. In infant eyes, elastin was present in microfibrillar aggregates in the core of the plates. In young adults, thin elastic fibers were present that ran longitudinally in the core of the plates. With age, elastic fibers become thicker, tubular, and surrounded by densely packed collagen fibers. In mild POAG, tubular elastic fibers no longer were identifiable. Fragments of elastic fibers and microfibrillar aggregates stained positively for elastin suggested new synthesis of elastin that was not organized into tubular elastic fibers. In advanced POAG, masses of nonfibrillar elastin-positive material had a spotted appearance. Throughout the cribriform plates, there was a loss of collagen fibers, proliferation of basement membranes, and bundles of elastin-negative microfibrils not associated with collagen or elastic fibers. The progression of marked changes in elastic fibers and the disorganization of the ECM of the lamina cribrosa was associated with the loss of function and continuous remodeling of the optic nerve head in POAG.

Topics: Adolescent; Adult; Aged; Aged, 80 and over; Aging; Child; Child, Preschool; Elastic Tissue; Elastin; Extracellular Matrix; Fetus; Glaucoma, Open-Angle; Humans; Immunohistochemistry; Infant; Infant, Newborn; Microscopy, Immunoelectron; Middle Aged; Optic Disk

Using immunofluorescent staining, we were able to characterize the changes in composition and distribution of the macromolecules making up the extracellular matrix of the lamina cribrosa of the glaucomatous human optic nerve head. In tissue adjacent to the glaucomatous cups, there was marked disorganization and loss of fibers of elastin within the cores of the cribriform plates. Collagen type VI, normally sparse, increased in quantity considerably throughout the lamina cribrosa in glaucomatous eyes with all degrees of damage. Collagen type IV and other basement membrane macromolecules appeared to extend into nerve bundles, presumably filling in spaces previously occupied by nerves. There was no appreciable change in the postlaminar region, which indicates the specificity of the extracellular matrix changes in the lamina cribrosa. Our results indicate that changes in the extracellular matrix play an important role in the progression of the glaucomatous process and may be a causative agent of the disease.

Topics: Aged; Aged, 80 and over; Antibodies, Monoclonal; Basement Membrane; Collagen; Elastin; Extracellular Matrix; Fluorescent Antibody Technique; Glaucoma, Open-Angle; Heparitin Sulfate; Humans; Laminin; Middle Aged; Optic Disk