scholarly journals Ultrastructure Organization of Collagen Fibrils and Proteoglycans of Stingray and Shark Corneal Stroma

2015 ◽  
Vol 2015 ◽  
pp. 1-11 ◽  
Author(s):  
Saud A. Alanazi ◽  
Turki Almubrad ◽  
Ahmad I. A. AlIbrahim ◽  
Adnan A. Khan ◽  
Saeed Akhtar
Keyword(s):  
Electron Microscopy ◽  
Chondroitin Sulfate ◽  
Dermatan Sulfate ◽  
Corneal Stroma ◽  
Collagen Fibrils ◽  
Ultrastructural Organization ◽  
The Mean

We report here the ultrastructural organization of collagen fibrils (CF) and proteoglycans (PGs) of the corneal stroma of both the stingray and the shark. Three corneas from three stingrays and three corneas from three sharks were processed for electron microscopy. Tissues were embedded in TAAB 031 resin. The corneal stroma of both the stingray and shark consisted of parallel running lamellae of CFs which were decorated with PGs. In the stingray, the mean area of PGs in the posterior stroma was significantly larger than the PGs of the anterior and middle stroma, whereas, in the shark, the mean area of PGs was similar throughout the stroma. The mean area of PGs of the stingray was significantly larger compared to the PGs, mean area of the shark corneal stroma. The CF diameter of the stingray was significantly smaller compared to the CF diameter in the shark. The ultrastructural features of the corneal stroma of both the stingray and the shark were similar to each other except for the CFs and PGs. The PGs in the stingray and shark might be composed of chondroitin sulfate (CS)/dermatan sulfate (DS) PGs and these PGs with sutures might contribute to the nonswelling properties of the cornea of the stingray and shark.

scholarly journals Extracellular compartments in matrix morphogenesis: collagen fibril, bundle, and lamellar formation by corneal fibroblasts.

1984 ◽  
Vol 99 (6) ◽  
pp. 2024-2033 ◽  
Author(s):  
D E Birk ◽  
R L Trelstad
Keyword(s):  
Electron Microscopy ◽  
Cell Surface ◽  
High Voltage ◽  
Collagen Fibril ◽  
Corneal Stroma ◽  
Collagen Fibrils ◽  
High Voltage Electron Microscopy ◽  
Voltage Electron ◽  
High Voltage Electron ◽  
Corneal Fibroblasts

The regulation of collagen fibril, bundle, and lamella formation by the corneal fibroblasts, as well as the organization of these elements into an orthogonal stroma, was studied by transmission electron microscopy and high voltage electron microscopy. Transmission and high voltage electron microscopy of chick embryo corneas each demonstrated a series of unique extracellular compartments. Collagen fibrillogenesis occurred within small surface recesses. These small recesses usually contained between 5 and 12 collagen fibrils with typically mature diameters and constant intrafibrillar spacing. The lateral fusion of the recesses resulted in larger recesses and consequent formation of prominent cell surface foldings. Within these surface foldings, bundles that contained 50-100 collagen fibrils were formed. The surface foldings continued to fuse and the cell surface retracted, forming large surface-associated compartments in which bundles coalesced to form lamellae. High voltage electron microscopy of 0.5 micron sections cut parallel to the corneal surface revealed that the corneal fibroblasts and their processes had two major axes at approximately right angles to one another. The surface compartments involved in the production of the corneal stroma were aligned along the fibroblast axes and the orthogonality of the cell was in register with that of the extracellular matrix. In this manner, corneal fibroblasts formed collagen fibrils, bundles, and lamellae within a controlled environment and thereby determined the architecture of the corneal stroma by the configuration of the cell and its associated compartments.

Influence of Ionic Concentration on Swelling Behavior and Shear Properties of the Bovine Cornea

2012 ◽  
Author(s):  
Hamed Hatami-Marbini ◽  
Ebitimi Etebu
Keyword(s):  
Extracellular Matrix ◽  
Dermatan Sulfate ◽  
Core Protein ◽  
Incident Light ◽  
Corneal Stroma ◽  
Ionic Concentration ◽  
Collagen Fibers ◽  
Collagen Fibrils ◽  
Knock Out ◽  
Free Ions

The mechanical properties and structure of connective tissues such as the cornea and the cartilage are derived from the functions and properties of their extracellular matrix, a polyelectrolyte gel composed of collagenous fibers embedded in an aqueous matrix. The collagen fibers in the extracellular matrix of the corneal stroma are arranged in regular lattice structures, which is necessary for corneal transparency and transmitting the incident light to the back of the eye. This regular pseudo hexagonal arrangement is attributed to the interaction of collagen fibers with the proteoglycans as these regularities are lost in knock-out mice [i]. Proteoglycans (PGs) are heavily glycosylated glycoproteins. They consist of a core protein to which is glycosaminoglycan chains are covalently attached. The main PG in the corneal stroma is the proteoglycan decorin. Decorin is the simplest small leucine-rich PG and only has a single glycosaminoglycan side chain. It has a horse shape core protein and binds collagen fibrils at regular sites. Chondroitin sulfate (CS), dermatan sulfate (DS), keratan sulfate (KS) are among the prevalent glycosaminoglycans found in the cornea. Under physiological conditions, these linear carbohydrate polymers are ionized and carry negative charges due to the presence of negatively charged carboxylate and sulfate groups. Therefore, a hydrated gel is formed in the empty space between collagen fibrils by attracting water. The interaction of negatively charged glycosaminoglycans with themselves and their interaction with the free ions contribute to the corneal swelling pressure and subsequently to its compressive stiffness. From structural view point, the corneal stroma is a composite polyelectrolyte system in which the observed regular spacings of the collagens are suggested to exist because of the structural interaction of collagens, negatively charged glycosaminoglycans, and the free ions in the interfibrillar space.

The ultrastructural organization of proteoglycans and collagen in human and rabbit scleral matrix

1985 ◽  
Vol 74 (1) ◽  
pp. 95-104
Author(s):  
R.D. Young
Keyword(s):  
Electron Microscopy ◽  
Articular Cartilage ◽  
Collagen Fibrils ◽  
Ultrastructural Organization ◽  
Connective Tissues ◽  
Collagen Organization ◽  
Band Position ◽  
Cuprolinic Blue ◽  
Relationship Of ◽  
Fibril Diameter

The distribution of proteoglycans and their association with collagen fibrils were studied in human and rabbit sclera following fixation of tissue in glutaraldehyde containing Cuprolinic Blue, a specific stain for proteoglycans when used in the presence of critical concentrations of electrolytes. Proteoglycans were visualized by electron microscopy as fine filaments, approximately 54 nm in length and 5 nm in diameter, associated with the d band in the gap zone of the periodic collagen banding pattern. Filaments were present in three orientations: (1) radiating from the d band to associate with corresponding sites on adjacent collagen fibrils; (2) encircling the collagen fibril at the d band position; and (3) lying along the fibril axis, often linking consecutive d bands. No difference was apparent between the proteoglycan-collagen organization in human and rabbit sclera. A similar arrangement of proteoglycan filaments in association with the d band was also evident throughout all levels of the sclera in spite of considerable variations in fibril diameter from inner to outer stroma. Furthermore, the specific relationship of proteoglycans with the collagen fibrils in sclera closely resembled that previously described in tendon and in articular cartilage, lending support to the view that the association of proteoglycans with collagen may be consistent in a majority of connective tissues, irrespective of their diverse functional specializations.

scholarly journals An Overview of in vivo Functions of Chondroitin Sulfate and Dermatan Sulfate Revealed by Their Deficient Mice

2021 ◽  
Vol 9 ◽  
Author(s):  
Shuji Mizumoto ◽  
Shuhei Yamada
Keyword(s):  
Chondroitin Sulfate ◽  
Dermatan Sulfate ◽  
Biological Activities ◽  
Skeletal Development ◽  
Genetic Disorders ◽  
Collagen Fibrils ◽  
Comprehensive Overview ◽  
Core Proteins ◽  
Deficient Mice

Chondroitin sulfate (CS), dermatan sulfate (DS) and heparan sulfate (HS) are covalently attached to specific core proteins to form proteoglycans in their biosynthetic pathways. They are constructed through the stepwise addition of respective monosaccharides by various glycosyltransferases and maturated by epimerases as well as sulfotransferases. Structural diversities of CS/DS and HS are essential for their various biological activities including cell signaling, cell proliferation, tissue morphogenesis, and interactions with a variety of growth factors as well as cytokines. Studies using mice deficient in enzymes responsible for the biosynthesis of the CS/DS and HS chains of proteoglycans have demonstrated their essential functions. Chondroitin synthase 1-deficient mice are viable, but exhibit chondrodysplasia, progression of the bifurcation of digits, delayed endochondral ossification, and reduced bone density. DS-epimerase 1-deficient mice show thicker collagen fibrils in the dermis and hypodermis, and spina bifida. These observations suggest that CS/DS are essential for skeletal development as well as the assembly of collagen fibrils in the skin, and that their respective knockout mice can be utilized as models for human genetic disorders with mutations in chondroitin synthase 1 and DS-epimerase 1. This review provides a comprehensive overview of mice deficient in CS/DS biosyntheses.

Systematic investigation of the skin in Chst14−/− mice: A model for skin fragility in musculocontractural Ehlers–Danlos syndrome caused by CHST14 variants (mcEDS-CHST14)

Glycobiology ◽  
2020 ◽  
Author(s):  
Takuya Hirose ◽  
Shuji Mizumoto ◽  
Ayana Hashimoto ◽  
Yuki Takahashi ◽  
Takahiro Yoshizawa ◽  
...  
Keyword(s):  
Chondroitin Sulfate ◽  
Anion Exchange ◽  
Dermatan Sulfate ◽  
Systematic Investigation ◽  
Exchange Chromatography ◽  
Collagen Fibrils ◽  
Loss Of Function ◽  
Ehlers Danlos Syndrome ◽  
Skin Fragility ◽  
Danlos Syndrome

Abstract Loss-of-function variants in CHST14 cause a dermatan 4-O-sulfotransferase deficiency named musculocontractural Ehlers–Danlos syndrome-CHST14 (mcEDS-CHST14), resulting in complete depletion of the dermatan sulfate moiety of decorin glycosaminoglycan (GAG) chains, which is replaced by chondroitin sulfate. Recently, we uncovered structural alteration of GAG chains in the skin of patients with mcEDS-CHST14. Here, we conducted the first systematic investigation of Chst14 gene-deleted homozygote (Chst14−/−) mice. We used skin samples of wild-type (Chst14+/+) and Chst14−/− mice. Mechanical fragility of the skin was measured with a tensile test. Pathology was observed using light microscopy, decorin immunohistochemistry and electron microscopy (EM) including cupromeronic blue (CB) staining. Quantification of chondroitin sulfate and dermatan sulfate was performed using enzymatic digestion followed by anion-exchange HPLC. In Chst14−/− mice, skin tensile strength was significantly decreased compared with that in Chst14+/+ mice. EM showed that collagen fibrils were oriented in various directions to form disorganized collagen fibers in the reticular layer. Through EM-based CB staining, rod-shaped linear GAG chains were found to be attached at one end to collagen fibrils and protruded outside of the fibrils, in contrast to them being round and wrapping the collagen fibrils in Chst14+/+ mice. A very low level of dermatan sulfate disaccharides was detected in the skin of Chst14−/− mice by anion-exchange chromatography. Chst14−/− mice, exhibiting similar abnormalities in the GAG structure of decorin and collagen networks in the skin, could be a reasonable model for skin fragility of patients with mcEDS-CHST14, shedding light on the role of dermatan sulfate in maintaining skin strength.

scholarly journals Collagen fibrils and proteoglycans of peripheral and central stroma of the keratoconus cornea - Ultrastructure and 3D transmission electron tomography

2019 ◽  
Vol 9 (1) ◽  
Author(s):  
Aljoharah Alkanaan ◽  
Robert Barsotti ◽  
Omar Kirat ◽  
Adnan Khan ◽  
Turki Almubrad ◽  
...  
Keyword(s):  
Electron Tomography ◽  
Three Dimensional ◽  
Corneal Stroma ◽  
Disease Process ◽  
Collagen Fibrils ◽  
Corneal Curvature ◽  
Transmission Electron ◽  
Descemet’S Membrane ◽  
The Mean ◽  
Corneal Disorder

AbstractKeratoconus (KC) is a progressive corneal disorder in which vision gradually deteriorates as a result of continuous conical protrusion and the consequent altered corneal curvature. While the majority of the literature focus on assessing the center of this diseased cornea, there is growing evidence of peripheral involvement in the disease process. Thus, we investigated the organization of collagen fibrils (CFs) and proteoglycans (PGs) in the periphery and center of KC corneal stroma. Three-dimensional transmission electron tomography on four KC corneas showed the degeneration of microfibrils within the CFs and disturbance in the attachment of the PGs. Within the KC corneas, the mean CF diameter of the central-anterior stroma was significantly (p ˂ 0.001) larger than the peripheral-anterior stroma. The interfibrillar distance of CF was significantly (p ˂ 0.001) smaller in the central stroma than in the peripheral stroma. PGs area and the density in the central KC stroma were larger than those in the peripheral stroma. Results of the current study revealed that in the pre- Descemet’s membrane stroma of the periphery, the degenerated CFs and PGs constitute biomechanically weak lamellae which are prone to disorganization and this suggests that the peripheral stroma plays an important role in the pathogenicity of the KC cornea.

Hydration Effects on Tensile Properties of the Corneal Stroma

2013 ◽  
Author(s):  
Abdolrasol Rahimi ◽  
Hamed Hatami-Marbini
Keyword(s):  
Tensile Properties ◽  
Dermatan Sulfate ◽  
Lattice Structure ◽  
Corneal Thickness ◽  
Corneal Stroma ◽  
Swelling Pressure ◽  
Keratan Sulfate ◽  
Empty Space ◽  
Collagen Fibrils ◽  
Healthy Human

The mechanical behavior of the cornea is mainly governed by the microstructure and composition of the stroma. The stroma is a highly ordered extracellular matrix and constitutes about 90% of the corneal thickness. From the mechanics point of view, the corneal stroma can be considered as a polyelectrolyte gel which is composed of collagen fibrils embedded in an aqueous matrix. The collagen fibrils compose about 70% of cornea’s dry mass and are arranged in a regular lattice structure [2]. Previous studies have shown that while the collagen fibrils are primarily located parallel to the surface, they are not distributed uniformly in all directions and their preferred orientation is not same in different species. For example, collagen fibrils are almost equally distributed in the nasal-temporal and inferior-superior directions in healthy human corneas [4] and they are mainly aligned in the inferior-superior direction in bovine corneas[2]. The differences in the orientations of the collagen fibrils have seen to have important implications on the mechanical properties of the cornea. In addition to this observation, the relative distance between the collagen fibrils is expected to play a role in defining the mechanics of the tissue. It is well-documented that the proteoglycans bind collagen fibrils at regular sites and control their relative position. The main proteoglycan in the corneal stroma is decorin. Decorin is the simplest small leucine-rich proteoglycan with a single glycosaminoglycan side chain. Chondroitin sulfate, dermatan sulfate, and keratan sulfate are among the prevalent glycosaminoglycans found in the cornea. Under physiological conditions, these linear carbohydrate polymers are ionized and carry negative charges. Therefore, a hydrated gel is formed in the empty space between collagen fibrils by attracting water. It is known that the interaction of these negatively charged glycosaminoglycans with themselves and with the free ions contribute to the corneal swelling pressure and subsequently to its compressive stiffness. Nevertheless, their possible influence on the corneal tensile properties is yet to be determined. In this work, we experimentally characterized the tensile properties of the bovine corneal stroma in different bathing solutions. Furthermore, a quasi-linear viscoelastic (QLV) model was used to examine the effect of bathing fluids and corneal hydration on mechanical parameter of the cornea.

scholarly journals An immunoelectron microscope study of the organization of proteoglycan monomer, link protein, and collagen in the matrix of articular cartilage.

1982 ◽  
Vol 93 (3) ◽  
pp. 921-937 ◽  
Author(s):  
A R Poole ◽  
I Pidoux ◽  
A Reiner ◽  
L Rosenberg
Keyword(s):  
Electron Microscopy ◽  
Hyaluronic Acid ◽  
Articular Cartilage ◽  
Guanidine Hydrochloride ◽  
Collagen Fibrils ◽  
Ultrastructural Organization ◽  
Deep Zone ◽  
Superficial Zone ◽  
Bovine Articular Cartilage ◽  
Link Protein

Monospecific antibodies to bovine cartilage proteoglycan monomer (PG) and link protein (LP) have been used with immunoperoxidase electron microscopy to study the distribution and organization of these molecules in bovine articular cartilage. The following observations were made: (a) The interterritorial matrix of the deep zone contained discrete interfibrillar particulate staining for PG and LP. This particulate staining, which was linked by faint bands of staining (for PG) or filaments (for LP), was spaced at 75- to 80-nm intervals. On collagen fibrils PG was also detected as particulate staining spaced at regular intervals (72 nm), corresponding to the periodicity of collagen cross-banding. The interfibrillar PG staining was often linked to the fibrillar PG staining by the same bands or filaments. The latter were cleaved by a proteinase-free Streptomyces hyaluronidase with the removal of much of the interfibrillar lattice. Since this enzyme has a specificity for hyaluronic acid, the observations indicate that the lattice contains a backbone of hyaluronic acid (which appeared as banded or filamentous staining) to which is attached LP and PG, the latter collapsing when the tissue is fixed, reacted with antibodies, and prepared for electron microscopy. Thishyaluronic acid is anchored to collagen fibrils at regular intervals where PG is detected on collagen. PG and LP detected by antibody in the interterritorial zones are essentially fully extractible with 4 M guanidine hydrochloride. These observations indicated that interfibrillar PG and LP is aggregated with HA in this zone. (b) The remainder of the cartilage matrix had a completely different organization of PG and LP. There was no evidence of a similar latticework based on hyaluronic acid. Instead, smaller more closely packed particulate staining for PG was seen everywhere irregularly distributed over and close to collagen fibrils. LP was almost undetectable in the territorial matrix of the deep zone, as observed previously. In the middle and superficial zones, stronger semiparticulate staining for LP was distributed over collagen fibrils. (c) In the superficial zone, reaction product for PG was distributed evenly on collagen fibrils as diffuse staining and also irregularly as particulate staining. LP was observed as semiparticulate staining over collagen fibrils. The diffuse staining for PG remained after extraction with 4 M guanidine hydrochloride. (d) In pericellular matrix, most clearly identified in middle and deep zones, the nature and organization of reaction product for PG and LP were similar to those observed in the territorial matrix, except that LP and PG were more strongly stained and amorphous staining for both components was also observed. (e) This study demonstrates striking regional variations of ultrastructural organization of PG and LP in articular cartilage...

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