Loss of Inner Retinal Neurons After Retinal Ischemia in Rats

Abstract

PURPOSE. Ischemia is a risk factor for eye diseases like ocular vein occlusion or glaucoma. To investigate effects of ischemia-reperfusion (I/R) a lot of different animal models are used, studying one or two different cell types, which creates heterogeneity of data. The aim of this study was to investigate the function and morphology of the whole retina and different retinal cell types in an I/R model. METHODS. I/R was induced by elevating the intraocular pressure in the right eyes of rats. Twenty-one days after ischemia, electroretinogram measurements were performed. Changes in layer thickness were investigated. Changes of RGC, amacrine-, rod bipolar-, and glia cells as well as presence of apoptosis were analyzed immunohistologically. RESULTS. A-wave-and b-wave amplitudes were decreased; histology showed a reduction of RGC-and inner plexiform layer thickness and a 29% loss of RGCs occurred in ischemic eyes (P ¼ 0.016). An increase of apoptotic cells was detected in the GCL and INL of ischemic retinas (P < 0.05). Also, a loss of cholinergic amacrine cells (control: 11 6 1 cells/mm, I/R: 4 6 1 cells/mm, P < 0.001), but no change in rod bipolar cell numbers was noted. CONCLUSIONS. Our study allowed a comparison of the effects of I/R for different retinal cell types. Cells in the outer retina seemed to be more resistant to ischemic damage compared with cells of the inner retina. We hypothesize that a degenerative process, like a secondary wave of apoptosis, occurs 21 days after I/R, causing progressive damage in the retina.

Neuroprotective Effects of Crocin against Oxidative Stress Induced by Ischemia/Reperfusion Injury in Rat Retina

“…In the present study, the number of cells in the RGC and the thickness of the IRL were decreased after IR injury. In the study by Schmid et al [27], the number of cells in the GCL and the thickness of the inner plexiform layer induced by ischemia had a significant reduction and there was no difference in rod bipolar cell numbers. Our result is consistent with this research.…”

“…The increased level of cleaved caspase-3 in the ischemic eye indicated that apoptosis plays a major role in RGC degeneration. Other studies also investigated the expression of cleaved caspase-3 in an IR model and likewise found a significant increase of cleaved caspase-3 RGCs in ischemic eyes [27]. It is well known that caspases are a family of intracellular proteins involved in the initiation and execution of cell apoptosis.…”

Liefert die OCT-Morphologie Hinweise für die Visusprognose nach Venenverschluss?

“…Die Schichtanalyse konnte zeigen, dass die parafoveoläre Verminderung der Netzhautdicke in erster Linie auf eine Verdünnung der Ganglienzellschicht, der inneren plexiformen sowie der inneren Körnerschicht zurückzuführen war. Dies passt zu Ergebnissen experimenteller Untersuchungen, in denen ischämische Veränderungen in den Bereichen der inneren Netzhaut auch im Tiermodell nachgewiesen werden konnten [8].…”

Interleukin-33 Prevents Retinal Ischemia Reperfusion Injury in Rats by Preventing Apoptosis

“…However, it is known that apoptosis plays an important role (18). One study revealed that cells in the inner retina especially RGCs are more vulnerable to ischemic damage compared to cells of the outer retina (19). Apoptosis, as detected by TUNEL staining, has been observed in the GCL, INL, and outer nuclear layer of the retina (20).…”