ABSTRACT
Purpose: To investigate the expression of angiotensin-converting enzyme 2 (ACE2), the receptor for SARS-CoV-2 in human retina. Methods: Human post-mortem eyes from 13 non-diabetic control cases and 11 diabetic retinopathy cases were analyzed for the expression of ACE2. To compare the vascular ACE2 expression between different organs that involve in diabetes, the expression of ACE2 was investigated in renal specimens from nondiabetic and diabetic nephropathy patients. Expression of TMPRSS2, a cell-surface protease that facilitates SARS-CoV-2 entry, was also investigated in human nondiabetic retinas. Primary human retinal endothelial cells (HRECs) and primary human retinal pericytes (HRPCs) were further used to confirm the vascular ACE2 expression in human retina. Results: We found that ACE2 was expressed in multiple nonvascular neuroretinal cells, including the retinal ganglion cell layer, inner plexiform layer, inner nuclear layer, and photoreceptor outer segments in both nondiabetic and diabetic retinopathy specimens. Strikingly, we observed significantly more ACE2 positive vessels in the diabetic retinopathy specimens. By contrast, in another end-stage organ affected by diabetes, the kidney, ACE2 in nondiabetic and diabetic nephropathy showed apical expression of ACE2 tubular epithelial cells, but no endothelial expression in glomerular or peritubular capillaries. Western blot analysis of protein lysates from HRECs and HRPCs confirmed expression of ACE2. TMPRSS2 expression was present in multiple retinal neuronal cells, vascular and perivascular cells, and Müller glia. Conclusions: Together, these results indicate that retina expresses ACE2 and TMPRSS2. Moreover, there are increased vascular ACE2 expression in diabetic retinopathy retinas.
Subject(s)
Angiotensin-Converting Enzyme 2/metabolism , Diabetic Retinopathy/enzymology , Receptors, Virus/metabolism , Retina/enzymology , SARS-CoV-2/physiology , Adult , Aged , Aged, 80 and over , Binding Sites , Blotting, Western , Cells, Cultured , Diabetic Nephropathies/enzymology , Diabetic Nephropathies/pathology , Diabetic Nephropathies/virology , Diabetic Retinopathy/pathology , Diabetic Retinopathy/virology , Endothelium, Vascular/enzymology , Endothelium, Vascular/virology , Female , Fluorescent Antibody Technique, Indirect , Humans , Immunohistochemistry , Male , Middle Aged , Pericytes/enzymology , Pericytes/virology , Retinal Vessels/enzymology , Retinal Vessels/pathology , Retinal Vessels/virology , Serine Endopeptidases/metabolismABSTRACT
Ophthalmologic nvolvement in SARS-CoV-infected patients is variegated. One of the ophthalmologic pathologies is optic neuritis. Optic neuritis in SARS-CoV-infected patients may precede the classical pulmonary manifestations of COVID-19 and can be unilateral or bilateral. Optic neuritis has been repeatedly reported in COVID-19 patients and may occur with or without affection of other cranial nerves. Since cerebro-spinal fluid parameters can be abnormal in COVID-19 associated optic neuritis, these patients require a spinal tap. Before diagnosing SARS-CoV-2 associated optic neuritis various differentials need to be excluded. Since SARS-CoV-2 causes endothelial damage complicated by thrombus formation and thromboembolism, ophthalmologic vascular complication due to an infection with SARS-CoV-2 such as anterior ischemic optic neuropathy (AION), central retinal artery occlusion (CRAO), and retinal vein occlusion need to be excluded. CRAO may result from arterial hypertension, myocarditis, heart failure, Takotsubo syndrome, atrial fibrillation, or atrial flutter, frequent cardiac complications of COVID-19. Since CRAO can be accompanied by ischemic stroke, patients with SARS-CoV-2 associated optic neuritis need to undergo a cerebral MRI.