Breakdown of blood-retinal outer barrier in mice following acute high intraocular pressure

Objective

To investigate the breakdown of blood-retinal outer barrier in the ischemia-reperfusion injury mice following acute intraocular hypertension.

Methods

Fifty-seven SPF male C57BL/6J mice were selected and divided into the control group and high-intraocular pressure (IOP) group by using the random number table method.There were 25 mice in the control group and 32 mice in the high-IOP group.After the failure and poor modeling excluded, 20 mice were included in each group, and the left eyes were selected as the experimental eyes.The ischemia-reperfusion injury model of the high-IOP group was established following acute intraocular hypertension by anterior chamber perfusion of 0.9% sodium chloride solution, and the control group only received anterior chamber puncture.Optical coherence tomography was used to detect retinal thickness.Immunofluorescence staining was utilized to identify zonula occludens-1 (ZO-1) protein distribution in retina.Retinal capillary degeneration was identified by trypsin digestion.Inflammatory cell infiltration in retinal sections was observed by hematoxylin and eosin staining.The use and care of the animals complied with the Statement of the Association for Research in Vision and Ophthalmology, and the study protocol was approved by an Ethics Committee of Changsha Aier Eye Hospital (No.2018-KYPJ005).

Results

Compared with the control group, the structure of the retinal pigment epithelium (RPE) layer was irregular with obvious exudation and local neuroepithelial detachment and elevation.The thickness of the full retinal layer of mice in the high-IOP group was (235.8±5.3)μm, which was significantly thicker than (213.3±3.9)μm in the control group (t=3.427, P=0.009). ZO-1 staining results showed that ZO-1 was mainly located in cell membrane and a small part in cytoplasm in the RPE layer of mice.Two days after modeling, ZO-1 in the high-IOP group was significantly internalized with decrease in cell membrane and increase in cytoplasm, and its distribution was irregular.Seven days after modeling, retinal capillary degeneration was observed in the high-IOP group, and the number of degenerated retinal capillaries was 201.0±13.2, which was significantly larger than 11.2±1.7 in the control group (t=14.280, P<0.01). Hematoxylin-eosin staining results showed that inflammatory cell infiltration, mainly neutrophils, could be observed in the mice retina with high IOP, and the infiltrated inflammatory cells were mainly located under the internal limiting membrane.

Conclusions

Acute intraocular hypertension induced retinal ischemia-reperfusion injury in mice destroys the integrity of the outer retinal barriers, and causes granulocyte infiltration in the peripheral circulation, retinal edema as well as retinal capillary degeneration.

Glaucoma; Ocular hypertension, acute; Blood-retinal barrier; Ischemia-reperfusion; Retina; Pathological mechanism; Zonula occludens-1