Modeling Study Incorporating Depth-Dependent Transverse Reinforcement due to Variation in Collagen Lamellae Interweaving in Corneal Tissue

2012 ◽  
Author(s):  
Kimberly A. Ziegler ◽  
Thao D. Nguyen
Keyword(s):  
Visual Acuity ◽  
Type I Collagen ◽  
Corneal Thickness ◽  
Corneal Stroma ◽  
Transverse Reinforcement ◽  
Type I ◽  
Corneal Tissue ◽  
Central Cornea ◽  
Strength And Stiffness ◽  
Adverse Affects

The cornea is crucial for maintaining refraction and focusing ability of the eye. Small alterations in mechanical behavior of the tissue can cause changes in curvature and structure of the cornea, having adverse affects on visual acuity. Since the corneal stroma makes up 90% of corneal thickness and contains a majority of the tissue’s collagen content, it is considered the dominant contributor to the tissue’s mechanical strength and stiffness, which originates from a complex fiber-reinforced structure [1]. It has been shown that collagen lamellae (comprised of type I collagen fibrils) within a dense, proteoglycan-rich matrix, are highly interwoven in the anterior third of the cornea and the degree of interweaving decreases significantly through the thickness with relatively no interweaving observed in the posterior third [1]. The interwoven structure also varies within the plane of the tissue, gradually increasing from a planar arrangement in the central cornea to a highly interwoven arrangement near the limbus [2].

Collagen fibrillogenesis in vitro: interaction of types I and V collagen

1986 ◽  
Vol 44 ◽  
pp. 210-211
Author(s):  
Arthur J. Wasserman ◽  
Kathy C. Kloos ◽  
David E. Birk
Keyword(s):  
Type I Collagen ◽  
Corneal Stroma ◽  
Minor Component ◽  
Homogeneous Distribution ◽  
Type I ◽  
Type V Collagen ◽  
Fibril Morphology ◽  
Type V ◽  
In Vitro Interaction

Type I collagen is the predominant collagen in the cornea with type V collagen being a quantitatively minor component. However, the content of type V collagen (10-20%) in the cornea is high when compared to other tissues containing predominantly type I collagen. The corneal stroma has a homogeneous distribution of these two collagens, however, immunochemical localization of type V collagen requires the disruption of type I collagen structure. This indicates that these collagens may be arranged as heterpolymeric fibrils. This arrangement may be responsible for the control of fibril diameter necessary for corneal transparency. The purpose of this work is to study the in vitro assembly of collagen type V and to determine whether the interactions of these collagens influence fibril morphology.

scholarly journals Relative rates of biosynthesis of collagen type I, type V and type VI in calf cornea

1991 ◽  
Vol 274 (2) ◽  
pp. 615-617 ◽  
Author(s):  
P Kern ◽  
M Menasche ◽  
L Robert
Keyword(s):  
Type I Collagen ◽  
Collagen Type ◽  
Corneal Stroma ◽  
Collagen Type I ◽  
Type I ◽  
Type Vi Collagen ◽  
Sds Page ◽  
Proline Incorporation ◽  
Type V

The biosynthesis of type I, type V and type VI collagens was studied by incubation of calf corneas in vitro with [3H]proline as a marker. Pepsin-solubilized collagen types were isolated by salt fractionation and quantified by SDS/PAGE. Expressed as proportions of the total hydroxyproline solubilized, corneal stroma comprised 75% type I, 8% type V and 17% type VI collagen. The rates of [3H]proline incorporation, linear up to 24 h for each collagen type, were highest for type VI collagen and lowest for type I collagen. From pulse-chase experiments, the calculated apparent half-lives for types I, V and VI collagens were 36 h, 10 h and 6 h respectively.

‘Small’-proteoglycan: collagen interactions: Keratan sulphate proteoglycan associates with rabbit corneal collagen fibrils at the ‘a’ and ‘c’ bands

1985 ◽  
Vol 5 (9) ◽  
pp. 765-774 ◽  
Author(s):  
J. E. Scott ◽  
M. Haigh
Keyword(s):  
Binding Sites ◽  
Type I Collagen ◽  
Specific Binding ◽  
Corneal Stroma ◽  
Collagen Fibrils ◽  
Type I ◽  
Keratan Sulphate ◽  
Protein Rich ◽  
Small Proteoglycan ◽  
Corneal Collagen

l. Proteoglycans (PGs) in rabbit corneal stroma and mouse sclera have been stained for electron microscopy with Cupromeronic blue in a critical electrolyte concentration (CEC) mode, with and without prior digestion of the tissue by keratanase or chondroitinase ABC to remove the keratan sulphate (KS) or chondroitin-dermatan sulphates (CS or DS) respectively.2. Two classes of PGs, located orthogonally to the corneal collagen fibrils at either the ‘step’ (band ‘a’ or ‘c’) or gap zone (band ‘d’ or ‘e’) are shown to be KS-PGs or DS-PGs respectively. Four separate and specific PG binding sites on Type I collagen fibrils have thus been identified.3. Rabbit corneal KS and DS PGs each contain two kinds of PG (Gregory JD, Coster L & Damle SP (1982) J. Biol. Chem.257, 6965–6970). We propose that each ‘small’ protein-rich PG is associated with a specific binding site on the collagen fibril.

Surface Modified Poly(vinyl alcohol) Nanofiber for the Artificial Corneal Stroma

2007 ◽  
Vol 342-343 ◽  
pp. 209-212 ◽  
Author(s):  
Hisatoshi Kobayashi
Keyword(s):  
Corneal Epithelium ◽  
Vinyl Alcohol ◽  
Type I Collagen ◽  
Corneal Stroma ◽  
Light Transmittance ◽  
Poly Vinyl Alcohol ◽  
Type I ◽  
Nanofiber Sheets

Previously we have found that the immobilization of Type I collagen on the poly(vinyl alcohol)(PVA) hydrogel disc was effective in supporting adhesion and growth of the corneal epithelium and stromal cell in vitro. But the durability of the produced corneal epithelium layer in vivo has some problem. We hypothesized the cell construction force is much stronger than the force of the cell adhesion on the flat modified PVA surfaces. Therefore the improvement of mechanical anchoring force between the substrate and formed corneal cell layer maybe become one of the solving methods. In this study, we prepared the PVA nanofiber mat by using the electrospinning method and the surface modification of the PVA nanofiber was studied to improve the durability of the corneal epithelium layer. The collagen-immobilized PVA nanofiber sheets could support the adhesion and proliferation of rabbit corneal epithelial cells. And the stratified corneal epithelium structure was observed on the PVA nanofiber sheets when the epithelium was co-cultured with rabbit corneal stromal cells. It means that the corneal epithelium was well differentiated on the collagen immobilized PVA nanofiber sheet. The stability of the corneal epithelium layer on the PVA was dramatically improved; the stratified epithelium layer was kept for two weeks after the differentiation introduction, totally after one month. A light transmittance of these materials is not yet enough. Further study to improve the transmission of light, is required.

scholarly journals PCL Scaffold Combined with Rat Tail Collagen Type I to Reduce Keratocyte Differentiation and Prevent Corneal Stroma Fibrosis after Injury.

2021 ◽  
Author(s):  
Wenhan Xu ◽  
Bin Kong ◽  
Huatao Xie ◽  
Weijian Liu ◽  
Sheng Liu ◽  
...  
Keyword(s):  
Composite Material ◽  
Collagen Type ◽  
Corneal Stroma ◽  
Collagen Type I ◽  
Type I ◽  
Corneal Tissue ◽  
Self Healing ◽  
Corneal Injury ◽  
3D Composite ◽  
Rat Tail

Abstract The cornea is one of the major refractive eye components with significant functions, and its transparency is essential for clear vision. With regard to corneal injury, the corneal epithelium has a strong self-healing ability, while the corneal stroma is not capable of total self-repair. Therefore, preventing fibrosis and reducing keratocyte differentiation after injury have always been a challenge. The severe shortage of donor corneas for transplantation and transplant rejection prompted the development of corneal tissue engineering. In this study, we fabricated a poly(ε-caprolactone) (PCL) microfibrous scaffold and infused the scaffold with rat tail collagen type I to obtain a 3D composite material. The PCL/collagen scaffold was designed to fabricate an optimal construct that simulates the stromal structure with properties that are most similar to the native cornea. The PCL scaffold has good mechanical properties, and infusion with rat tail collagen type I improved its biocompatibility. The results demonstrate that 3D composite material could reduce keratocyte differentiation, help achieve regular collagen distribution, and promote corneal repair.

scholarly journals A Mouse Model of Brittle Cornea Syndrome caused by mutation in Zfp469

2021 ◽  
Author(s):  
Chloe M. Stanton ◽  
Amy S. Findlay ◽  
Camilla Drake ◽  
Mohammad Z. Mustafa ◽  
Philippe Gautier ◽  
...  
Keyword(s):  
Type I Collagen ◽  
Corneal Stroma ◽  
Therapeutic Benefit ◽  
Type I ◽  
Loss Of Function ◽  
Brittle Cornea Syndrome ◽  
Vitro Model ◽  
Biomechanical Strength ◽  
Corneal Thinning

Brittle Cornea Syndrome (BCS) is a rare recessive condition characterised by extreme thinning of the cornea and sclera. BCS results from loss-of-function mutations in the poorly understood genes ZNF469 or PRDM5. In order to determine the function of ZNF469 and to elucidate pathogenic mechanisms, we used genome editing to recapitulate a human ZNF469 BCS mutation in the orthologous mouse gene, Zfp469. Ophthalmic phenotyping showed that homozygous Zfp469 mutation causes significant central and peripheral corneal thinning arising from reduced stromal thickness. Expression of key components of the corneal stroma in primary keratocytes from Zfp469BCS/BCS mice is affected, including decreased Col1a1 and Col1a2 expression. This alters the type I:type V collagen ratio and results in collagen fibrils with smaller diameter and increased fibril density in homozygous mutant corneas, correlating with decreased biomechanical strength in the cornea. Cell-derived matrices generated by primary keratocytes show reduced deposition of type I collagen offering an in vitro model for stromal dysfunction. Work remains to determine whether modulating ZNF469 activity will have therapeutic benefit in BCS or in conditions such as keratoconus where the cornea thins progressively.

scholarly journals Embryonic avian cornea contains layers of collagen with greater than average stability.

1986 ◽  
Vol 103 (4) ◽  
pp. 1587-1593 ◽  
Author(s):  
T F Linsenmayer ◽  
E Gibney ◽  
J M Fitch
Keyword(s):  
Thermal Stability ◽  
Type I Collagen ◽  
Collagen Fibrils ◽  
Collagen Molecule ◽  
Type I ◽  
Corneal Tissue ◽  
Tissue Sections ◽  
Triple Helical Domain ◽  
Thermal Stability Of

A unique morphological feature of the embryonic avian cornea is the uniformity of its complement of striated collagen fibrils, each of which has a diameter of 25 nm. We have asked whether this apparent morphological uniformity also reflects an inherent uniformity of the structural and physical properties of these fibrils. For this we have examined the in situ thermal stability of the type I collagen within these fibrils. Corneal tissue sections were reacted at progressively higher temperatures with conformation-dependent monoclonal antibodies directed against the triple-helical domain of the type I collagen molecule. These studies show that the cornea contains layers of collagen fibrils with greater than average stability. The two most prominent of these extend uninterrupted across the entire width of the cornea, and then appear to insert into thick bundles of scleral collagen, which in turn appear to insert into the scleral ossicles, a ring of bony plates which circumscribe the sclera of the avian eye. Once formed, the bands may act to stabilize the shape of the cornea or, conversely, to alter it during accommodation.

scholarly journals A Mouse Model of Brittle Cornea Syndrome caused by mutation in Zfp469.

2021 ◽  
Author(s):  
Chloe M. Stanton ◽  
Amy S. Findlay ◽  
Camilla Drake ◽  
Mohammad Z. Mustafa ◽  
Philippe Gautier ◽  
...  
Keyword(s):  
Type I Collagen ◽  
Corneal Stroma ◽  
Therapeutic Benefit ◽  
Type I ◽  
Loss Of Function ◽  
Brittle Cornea Syndrome ◽  
Vitro Model ◽  
Biomechanical Strength ◽  
Corneal Thinning

Brittle Cornea Syndrome (BCS) is a rare recessive condition characterised by extreme thinning of the cornea and sclera. BCS results from loss-of-function mutations in the poorly understood genes ZNF469 or PRDM5. In order to determine the function of ZNF469 and to elucidate pathogenic mechanisms, we used genome editing to recapitulate a human ZNF469 BCS mutation in the orthologous mouse gene, Zfp469. Ophthalmic phenotyping showed that homozygous Zfp469 mutation causes significant central and peripheral corneal thinning arising from reduced stromal thickness. Expression of key components of the corneal stroma in primary keratocytes from Zfp469BCS/BCS mice is affected, including decreased Col1a1 and Col1a2 expression. This alters the type I:type V collagen ratio and results in collagen fibrils with smaller diameter and increased fibril density in homozygous mutant corneas, correlating with decreased biomechanical strength in the cornea. Cell-derived matrices generated by primary keratocytes show reduced deposition of type I collagen offering an in vitro model for stromal dysfunction. Work remains to determine whether modulating ZNF469 activity will have therapeutic benefit in BCS or in conditions such as keratoconus where the cornea thins progressively.

Ocular manifestations of Marfan syndrome in children and adolescents

2018 ◽  
Vol 29 (1) ◽  
pp. 38-43 ◽  
Author(s):  
Daniel J Salchow ◽  
Petra Gehle
Keyword(s):  
Visual Acuity ◽  
Children And Adolescents ◽  
Marfan Syndrome ◽  
Corneal Thickness ◽  
Spherical Equivalent ◽  
Ectopia Lentis ◽  
Central Cornea ◽  
Ocular Manifestations ◽  
University Medicine ◽  
Comparative Cohort Study

Purpose: To study ocular manifestations of Marfan syndrome in children and adolescents. Methods: Retrospective comparative cohort study on consecutive patients up to age 17 years, presenting to the interdisciplinary Marfan clinic of Charité-University Medicine Berlin over a period of 4 years. Results: A total of 52 Marfan syndrome patients and 73 controls were enrolled. In Marfan syndrome eyes, the cornea was flatter (mean keratometry, 40.86 ± 2.13 vs 42.55 ± 1.55 diopters in control eyes, p < .001) and corneal astigmatism was greater (1.50 ± 1.22 vs 0.88 ± 0.49 diopters in control eyes, p < .001). The central cornea was thinner in Marfan syndrome eyes (537.35 ± 40.64 vs 552.95 ± 38.57 μm, p = 0.007) and Marfan syndrome eyes were more myopic than control eyes (spherical equivalent, –2.77 ± 4.77 vs −0.64 ± 1.92 diopters, p < .001). Visual acuity was reduced (logMAR 0.11 ± 0.17 vs 0.04 ± 0.26, p = 0.014) and intraocular pressure was lower in Marfan syndrome eyes. Iris transillumination defects were more common in Marfan syndrome eyes (19.6% vs 4.3% in control eyes, odds ratio for Marfan syndrome in the presence of iris transillumination defects = 7.2). Ectopia lentis was only found in Marfan syndrome eyes (25 Marfan syndrome patients, 49% with available data, bilateral in 68%). Conclusion: Iris transillumination defects and ectopia lentis are characteristic ocular findings in children and adolescents with Marfan syndrome. Myopia is more common and corneal curvature, central corneal thickness, and visual acuity are reduced in Marfan syndrome eyes. Children with Marfan syndrome need regular comprehensive eye examinations to identify potential complications.

948: Clinical Safety, Histologic Findings and Surgical Methods in Complex Phalloplasty Using Type I Collagen

2007 ◽  
Vol 177 (4S) ◽  
pp. 314-314 ◽  
Author(s):  
Joon-Yang Kim ◽  
Hoon Seog Jean ◽  
Beom Joon Kim ◽  
Kye Yong Song
Keyword(s):  
Type I Collagen ◽  
Type I ◽  
Clinical Safety ◽  
Surgical Methods
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