- Email: [email protected]
Presence of matrix vesicles in the trabecular meshwork of glaucomatous eyes
348
Surv Ophthalmol
27(5) March-April
1983
CURRENT
OPHTHALMOLOGY
Presence of Matrix Vesicles in the Trabecular Meshwork of Glaucomatous Eyes, by J. W. Rowan. Albrecht van Graefes Arch Clin Exp Ophthalmol 218: 17 l-l 76, 1982 The presence and development of matrix vesicles within the connective tissue have been studied with increasing interest by many investigators since it became evident that these vesicles may play an essential role in the pathogenesis of a great number of connective tissue diseases. A number of workers have demonstrated that matrix vesicles can develop in the vessel wall in the cases of renal hypertension, arteriosclerosis or varices in experimental situations in which vessels are subjected to non-physiological stresses. Matrix vesicles are small extracellular bodies which either derive from intracellular lysosomes or from the cytoplasm itself. The lysosomal vesicle may still contain lysosomal enzymes such as acid phosphatases, while the nonlysosomal vesicles do not contain such enzymes and may represent isolated cytoplasmic processes. The trabecular meshwork can at least in part be considered a specialized vessel wall. It contains many cells resembling fibroblasts or macrophages which are capable of phagocytizing particles or macromolecules. It might therefore be expected in the trabecular meshwork under pathological conditions, such as chronic simple glaucoma, that vesicles may also be found which in fact proved in this study to be true. Chronic simple glaucoma eyes were found to have a trabecular meshwork with characteristic changes in the fine structure, particularly in the cribiform region. It is therefore possible that a relatively great number of vesicles found in the cases of chronic simple glaucoma are the result of cell degeneration. This situation may be in some ways comparable to the degenerative changes that occur in the peripheral blood vessels in various disease states. Further studies are needed however to substantiate this. (Abstract by C. Hoyt)
Comment In the last few years, matrix vesicles have been found in the vessel wall in various diseases and are considered to be related to pathological changes of the extracellular fibers of the connective tissue. Attention has been directed to the trabecular meshwork in this regard, since at least the cribiform region may be looked upon as part of a vessel wall. Rowan, in his present study, has documented matrix vesicles in the extracellular space that contains acid phosphatase activity in the trabecular meshwork. This hydrolytic enzyme in this area has led Rowan to conclude that these are lysosomal vesicles. Our own laboratory has described cell death in this area of trabecular meshwork as part of the aging process. Rowan therefore has concluded that the vesicles in the trabecular meshwork of glaucomatous eyes represent the loss and death of normal cells. He further proposes that matrix vesicles may be responsible for the alterations of the connective tissues in this area that contributes to increased resistance to outflow. It is noteworthy that in our own studies we have found more of such vesicles in parts of the meshwork other than in the cribiform plate region. This therefore raises the question whether the vesicles play a primary role in increased resistance to outflow. Nevertheless, these vesicles almost certainly represent cell remnants and are evidence of cellular death in these eyes. Further studies are needed to delineate this problem further, but Rowan’s observations add an important dimension to our understanding of the pathophysiology of the changes within the trabecular meshwork with aging and the glaucomatous process. JORGE ALVARADO SAN FRANCISCO, CALIFORNIA
Congenital Tumors of the Anterior Visual System With Dysplasia of the Optic Discs, by D. Taylor. Br J Ophthalmol 66:455-463, 1982 An optic disc may be considered to be dysplastic when it is congenitally abnormal owing to a developmental abnormality. Gross anomalies include colobomata and pits, and the optic disc may be of abnormal size and unusual shape or have an abnormal vascular arrangement. Minor development anomalies include unusual or hypoplastic discs may be pigmentation or abnormalities of the peripapillary retina. Small dysplastic difficult to diagnose since there are no absolute criteria and no readily available clinical techniques for measurement. Clinical judgment can be enhanced by evaluation of the ratio between the apparent size of the disc and the retinal arterials, or the size of the disc relative to the size of the fundus in a standard fundus photograph, but even with these techniques, the vagaries of observation leave the diagnosis to the clinician alone.
Surv Ophthalmol
27(5) March-April
1983
CURRENT
OPHTHALMOLOGY
Presence of Matrix Vesicles in the Trabecular Meshwork of Glaucomatous Eyes, by J. W. Rowan. Albrecht van Graefes Arch Clin Exp Ophthalmol 218: 17 l-l 76, 1982 The presence and development of matrix vesicles within the connective tissue have been studied with increasing interest by many investigators since it became evident that these vesicles may play an essential role in the pathogenesis of a great number of connective tissue diseases. A number of workers have demonstrated that matrix vesicles can develop in the vessel wall in the cases of renal hypertension, arteriosclerosis or varices in experimental situations in which vessels are subjected to non-physiological stresses. Matrix vesicles are small extracellular bodies which either derive from intracellular lysosomes or from the cytoplasm itself. The lysosomal vesicle may still contain lysosomal enzymes such as acid phosphatases, while the nonlysosomal vesicles do not contain such enzymes and may represent isolated cytoplasmic processes. The trabecular meshwork can at least in part be considered a specialized vessel wall. It contains many cells resembling fibroblasts or macrophages which are capable of phagocytizing particles or macromolecules. It might therefore be expected in the trabecular meshwork under pathological conditions, such as chronic simple glaucoma, that vesicles may also be found which in fact proved in this study to be true. Chronic simple glaucoma eyes were found to have a trabecular meshwork with characteristic changes in the fine structure, particularly in the cribiform region. It is therefore possible that a relatively great number of vesicles found in the cases of chronic simple glaucoma are the result of cell degeneration. This situation may be in some ways comparable to the degenerative changes that occur in the peripheral blood vessels in various disease states. Further studies are needed however to substantiate this. (Abstract by C. Hoyt)
Comment In the last few years, matrix vesicles have been found in the vessel wall in various diseases and are considered to be related to pathological changes of the extracellular fibers of the connective tissue. Attention has been directed to the trabecular meshwork in this regard, since at least the cribiform region may be looked upon as part of a vessel wall. Rowan, in his present study, has documented matrix vesicles in the extracellular space that contains acid phosphatase activity in the trabecular meshwork. This hydrolytic enzyme in this area has led Rowan to conclude that these are lysosomal vesicles. Our own laboratory has described cell death in this area of trabecular meshwork as part of the aging process. Rowan therefore has concluded that the vesicles in the trabecular meshwork of glaucomatous eyes represent the loss and death of normal cells. He further proposes that matrix vesicles may be responsible for the alterations of the connective tissues in this area that contributes to increased resistance to outflow. It is noteworthy that in our own studies we have found more of such vesicles in parts of the meshwork other than in the cribiform plate region. This therefore raises the question whether the vesicles play a primary role in increased resistance to outflow. Nevertheless, these vesicles almost certainly represent cell remnants and are evidence of cellular death in these eyes. Further studies are needed to delineate this problem further, but Rowan’s observations add an important dimension to our understanding of the pathophysiology of the changes within the trabecular meshwork with aging and the glaucomatous process. JORGE ALVARADO SAN FRANCISCO, CALIFORNIA
Congenital Tumors of the Anterior Visual System With Dysplasia of the Optic Discs, by D. Taylor. Br J Ophthalmol 66:455-463, 1982 An optic disc may be considered to be dysplastic when it is congenitally abnormal owing to a developmental abnormality. Gross anomalies include colobomata and pits, and the optic disc may be of abnormal size and unusual shape or have an abnormal vascular arrangement. Minor development anomalies include unusual or hypoplastic discs may be pigmentation or abnormalities of the peripapillary retina. Small dysplastic difficult to diagnose since there are no absolute criteria and no readily available clinical techniques for measurement. Clinical judgment can be enhanced by evaluation of the ratio between the apparent size of the disc and the retinal arterials, or the size of the disc relative to the size of the fundus in a standard fundus photograph, but even with these techniques, the vagaries of observation leave the diagnosis to the clinician alone.