Collagen Fibrils and Proteoglycans of Macular Dystrophy Cornea: Ultrastructure and 3D Transmission Electron Tomography

Akhtar, Saeed; Alkatan, Hind M.; Kirat, Omar; Khan, Adnan; Almubrad, Turki

doi:10.1017/s1431927615000483

Cited by 17 publications

(11 citation statements)

References 35 publications

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“…A species difference in the osmotic differential may be due to a higher fixed charge density in pig fibril coating GAGs. It may also be due to a diminished fixed charge density in the human corneas following long-term storage in organ culture caused by the loss of some fibril coating proteoglycans and/or the presence of a third proteoglycan component, which has been purported to exist inside the human corneal collagen fibrils [45]. …”

Section: Discussionmentioning

confidence: 99%

The structural response of the cornea to changes in stromal hydration

Hayes

White

Boote

et al. 2017

J. R. Soc. Interface.

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The primary aim of this study was to quantify the relationship between corneal structure and hydration in humans and pigs. X-ray scattering data were collected from human and porcine corneas equilibrated with polyethylene glycol (PEG) to varying levels of hydration, to obtain measurements of collagen fibril diameter, interfibrillar spacing (IFS) and intermolecular spacing. Both species showed a strong positive linear correlation between hydration and IFS2 and a nonlinear, bi-phasic relationship between hydration and fibril diameter, whereby fibril diameter increased up to approximately physiological hydration, H = 3.0, with little change thereafter. Above H = 3.0, porcine corneas exhibited a larger fibril diameter than human corneas (p < 0.001). Intermolecular spacing also varied with hydration in a bi-phasic manner but reached a maximum value at a lower hydration (H = 1.5) than fibril diameter. Human corneas displayed a higher intermolecular spacing than porcine corneas at all hydrations (p < 0.0001). Human and porcine corneas required a similar PEG concentration to reach physiological hydration, suggesting that the total fixed charge that gives rise to the swelling pressure is the same. The difference in their structural responses to hydration can be explained by variations in molecular cross-linking and intra/interfibrillar water partitioning.

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Section: Discussionmentioning

confidence: 99%

The structural response of the cornea to changes in stromal hydration

Hayes

White

Boote

et al. 2017

J. R. Soc. Interface.

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“…The method for 3D imaging used here was described by Akhtar et al (2014). In total, 120 digital images were taken from −60° to +60° angles to construct individual 3D images by using the software program “Composer-x64, version 3.4.2.0” (Massachusetts Institute of Technology, Cambridge, MA, USA).…”

Section: Methodsmentioning

confidence: 99%

Ultrastructure Features and Three-Dimensional Transmission Electron Tomography of Dhub Lizard (Uromastyx Aegyptia) Cornea and Its Adaptation to a Desert Environment

Akhtar¹,

Alkhalaf²,

Khan³

et al. 2016

Microsc Microanal

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We report ultrastructural features and transmission electron tomography of the dhub lizard (Uromastyx aegyptia) cornea and its adaptation to hot and dry environments. Six corneas of dhub lizards were fixed in 2.5% glutaraldehyde and processed for electron microscopy and tomography. The ultrathin sections were observed with a JEOL 1400 transmission electron microscope. The cornea of the dhub lizard is very thin (~28-30 µm). The epithelium constitutes ~14% of the cornea, whereas the stroma constitutes 80% of the cornea. The middle stromal lamellae are significantly thicker than anterior and posterior stromal lamellae. Collagen fibril (CF) diameters in the anterior stroma are variable in size (25-75 nm). Proteoglycans (PGs) are very large in the middle and posterior stroma, whereas they are small in the anterior stroma. Three-dimensional electron tomography was carried out to understand the structure and arrangement of the PG and CFs. The presence of large PGs in the posterior and middle stroma might help the animal retain a large amount of water to protect it from dryness. The dhub corneal structure is equipped to adapt to the dry and hot desert environment.

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“…Ultrastructural imaging and three-dimensional imaging of corneas with MCD demonstrate a clear organization of proteoglycans around the collagen fibrils. The collagen fibril diameter is significantly smaller than those of the normal cornea [47].…”

Section: Macular Corneal Dystrophy (Mcd)mentioning

confidence: 71%

Corneal Dystrophies and Degenerations

Alkatan¹,

Alkheraiji²,

Alzahem³

2019

Frontiers in Ophthalmology and Ocular Imaging

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The cornea is a complex structure with complex functions aiming to protect the internal ocular tissues and transmit and refract the coming light rays. Corneal dystrophies are a group of relatively infrequent genetic corneal disorders in which an abnormal material accumulates in the cornea causing variable loss of its clarity. On the other hand, corneal degenerations are more common and usually result from physiologic changes related to aging, particular disease, or long-standing environmental insults to the cornea. Ectatic corneal disorders are usually characterized by bilateral loss of corneal biomechanical strength leading to progressive thinning and bulging of the cornea with resultant astigmatism and decreased visual acuity. In this chapter, we will describe the basic embryological, anatomical, histologic, and physiological features of the cornea. Then, we will go over the clinical, histopathologic, medical, and surgical aspects of dystrophic, degenerative, and ectatic corneal disorders.

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Collagen Fibrils and Proteoglycans of Macular Dystrophy Cornea: Ultrastructure and 3D Transmission Electron Tomography

Cited by 17 publications

References 35 publications

The structural response of the cornea to changes in stromal hydration

The structural response of the cornea to changes in stromal hydration

Ultrastructure Features and Three-Dimensional Transmission Electron Tomography of Dhub Lizard (Uromastyx Aegyptia) Cornea and Its Adaptation to a Desert Environment

Corneal Dystrophies and Degenerations

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