Modeling the Mechanical Parameters of Glaucoma

Beneficial and Detrimental Pressure-Related Effects on Inner Neurons in the Adult Porcine In Vitro Retina

Purpose

To explore pressure-related effects in the adult porcine retina in vitro.

Methods

Retinal explants were subjected to 0, 10, 30, or 60 mmHg of pressure for 24 or 48 hours in culture. Overall tissue damage in sections was assessed by lactate dehydrogenase media levels, hematoxylin and eosin staining, and TUNEL staining. Inner retinal neurons were evaluated by protein kinase C alpha (rod bipolar cells), CHX10 (overall bipolar cell population), parvalbumin (amacrine cells), and RBPMS (ganglion cells) immunohistochemistry.

Results

All retinas kept in culture displayed increased pyknosis and apoptosis compared with directly fixed controls. The 10-mmHg explants displayed attenuation of overall tissue damage compared with the 0-, 30-, and 60-mmHg counterparts. No difference in the number of rod bipolar cells was seen in the 10-mmHg explants compared with directly fixed controls, whereas significantly fewer cells were detected in the remaining pressure groups. No difference in the number of ganglion cells in the 0-, 10-, and 60-mmHg groups was seen compared with directly fixed controls after 24 hours, whereas a lower number was found in the 30-mmHg counterpart. A decline of ganglion cells was found in the 0-, 10-, and 60-mmHg group after 48 hours, but no further decrease was seen in the 30-mmHg group. No differences were detected in overall bipolar and amacrine cells in the pressure groups after 24 hours compared with directly fixed controls.

Conclusions

A moderate amount of pressure attenuates culture-related retinal neurodegeneration. Rod bipolar cells are specifically vulnerable to excessive pressure.

Translational Relevance

These findings are relevant for glaucoma-related research.

Sodium Hyaluronate-Induced Ocular Hypertension in Rats Damages the Direction-Selective Circuit and Inner/Outer Retinal Plexiform Layers

Purpose

To assess the changes in retinal morphology in a rat model of chronic glaucoma induced by ocular hypertension.

Methods

Intraocular pressure (IOP) was surgically increased through weekly injections of sodium hyaluronate (HYA) in the anterior eye chamber of the left eye of male Wistar rats, whereas the right eyes were sham operated (salt solution). During the 10-week experimental period, IOP was measured weekly with a rebound tonometer. Retinal cryosections were prepared for histological/immunohistochemical analysis and morphometry.

Results

IOP was higher in HYA-treated eyes than in sham-operated eyes along the 10-week period, which was significant from the fourth to the nineth week. Ocular hypertension in HYA-treated eyes was associated with morphologic and morphometric changes in bipolar cells, ON-OFF direction-selective ganglion cells, ON/OFF starburst amacrine cells, and inner plexiform layer sublamina.

Conclusions

Serial HYA treatment in the rat anterior eye chamber results in mild-to-moderate elevated and sustained IOP and ganglion cell death, which mimics most human open-angle glaucoma hallmarks. The reduced number of direction-selective ganglion cells and starburst amacrine cells accompanied by a deteriorated ON/OFF plexus in this glaucoma model could lend insight to the abnormalities in motion perception observed in patients with glaucoma.