Acute ocular hypertension in adult pigmented mice: longitudinal functional and morphological studies

Abstract

AbstractPurposeTransient ischemia‐reperfusion (I/R) is a commonly employed method to study acute angle‐closure glaucoma. Here, we assess with functional and histological techniques the effects of various ischemic and reperfusion intervals.MethodsI/R was induced in C57BL/6J mice by inserting a 30G needle in the anterior chamber of the left eye connected to a 500 mL reservoir of 0.9%NaCl elevated over 150 cm, to increase the IOP from 8 to ≈90 mmHg for several intervals of 45', 60', 75' or 90' (n = 4; each group) and 3 days later mice were perfused, their retinas were prepared as flat‐mounts and immunostained with Brn3a antibodies to identify retinal ganglion cells (RGCs). In addition, the effects of 60' I/R were analyzed longitudinally in vivo with full field electroretinogram recordings at 3, 7, 14, and 21 days after injury (n = 12) and ex vivo with immunohistochemical techniques at 3, 7, 14 or 21 days to determine the survival of RGCs, horizontal cells, S‐cone or L/M cone photoreceptors that were identified with Brn3a, calbindin, S‐ or L/M‐Opsin antibodies, respectively.ResultsAt 3 days of 45' of I/R the Brn3a+RGC population remained intact, however, after 60', 75' or 90' the Brn3a+RGC population was reduced to 75, 37.5 and 12.5%, respectively, of its original value. At 7 days after 60' of I/R, Brn3a+RGCs decreased to 50%, and remained unchanged for up to at 21 days. Horizontal cells and S‐cones remained unchanged at every time interval examined. L/M cones diminished significantly at 7 days (≈70%) and further decreased to 58% at 14 days without further changes at 21 days. Functional analysis showed a permanent decrease in all waves studied, from 3 to 21 days after I/R.ConclusionsPigmented mice retina shows a damage threshold between 45' and 60' min of I/R for RGC survival. 60' of I/R leads to a rapid loss of innermost retina from 3 to 7 days, the horizontal cells are not affected, while in the outer retina, L/M cones are affected but S cones are not.CT