Part of the book: Glaucoma
The study of extracellular matrix (ECM) in the nervous system has longed been focused on the molecules promoting growth and migration. This is well supported by the work in the developing nervous system. However, the discovery of Nogo and chondroitin sulphate proteoglycans (CSPGs) in the injured nervous system in late 1980s has shifted some of the focus to inhibitory molecules. One of the biggest hurdles in neural regeneration is the formation of glial scar and the highly up-regulated inhibitory molecules present in the area. Apart from Nogo and CSPGs, other myelin-associated inhibitors, tenascins and semaphorins have been found associated with neuronal inhibition. Together with the identification of their receptors, we now have a better understanding on the mechanism of how these molecules control and limit regeneration in the central nervous system (CNS). Recent focus has been put on designing strategies in neutralizing these inhibitions for promoting regeneration after injury, and some are showing promising results. Moreover, latest studies also show that rehabilitation in injured animal models demonstrated drastic remodeling of ECM favoring regeneration. This review shall discuss all these different aspects and the importance of matrix remodeling in the CNS and the implication of ECM in some retinal pathologies.
Part of the book: Composition and Function of the Extracellular Matrix in the Human Body
The cornea is the transparent part of the eye that allows light to enter into the eye and reach the retina, thereby activating the neurons that will send messages to the brain. The sclera is the hard-white part of the eye, and its main function is to provide structure and form to the eye, and to support the retina. Indeed, while the cornea best performs its main functions when transparent and it is capable of adapting its curvature to allow the eye to focus, the sclera must be opaque and hard to function correctly. Both structures are mainly composed of collagen, some elastic fibres and ground substance, all components of the Extracellular Matrix. The disposition of the collagen fibres and the amount of ground substance around the fibres is responsible for the differences in the aspect of both these structures. In this chapter, for the first time we have compared the structure and ultrastructure of the cornea and sclera in humans and the whale adult (18mts) Balaenoptera physalus, the second largest animal on the planet. We will discuss how the differences in their structure may be related to the maintenance of intraocular pressure in their distinct environments, which is of particular clinical interest as increased intraocular pressure is one of the main causes underlying the development of open angle glaucoma.
Part of the book: Extracellular Matrix
The eyes of two whales Balaenoptera physalus and Baleoptera borealis were studied by our group. In this chapter, we present the anatomical, histological, immunohistochemical and ultrastructural studies of the eyes of both types of whales. Based on the results, we can conclude that at least in these two species, the whales are rod monochromat; their resolution is very limited due to the reduced number of retinal ganglion cells, some of which were giant size (more than 100 micrometers in diameter). The excellent representation of melanopsinic positive retinal ganglion cells suggests an adaptation to the dim light as well as involvement in the circadian rhythms. The large cavernous body located in the back of the eye may provide a mechanism that allows them to move the eye forward and backwords; this may facilitate focusing and provide protection from cold deep-sea temperatures.
Part of the book: Marine Mammals