Event Title
Examining the behavior of Myo/Nog cells in epiretinal membrane formation in a mouse model of Proliferative Vitreoretinopathy
Start Date
3-5-2023 1:00 PM
End Date
3-5-2023 4:00 PM
Description
INTRODUCTION: Proliferative Vitreoretinopathy (PVR) is a condition of the eye in which membranes form on the epiretinal or subretinal surface of the retina. Sometimes, fibrotic tissue may also form in the retina. These membranes contain myofibroblasts that produce a tractional force on the retina and may lead to detachment and blindness. We have previously shown that human epiretinal membranes (ERMs) contain a large population of Myo/Nog cells that had differentiated into myofibroblast. In the normal eye, small, subpopulations of Myo/Nog cells reside in the retina, lens, ciliary body and cornea. They increase in number, synthesize muscle proteins and differentiate into contractile myofibroblasts in the lens in response to cataract surgery.
PURPOSE: The aim of this study is to examine the behavior of Myo/Nog cells in ERM formation in a mouse model of PVR.
METHODS: Intravitreal injections of gas followed seven days later by injections of the human cell line ARPE-19 were performed to induce PVR. The eyes were monitored and graded for ERM formation one to four weeks after injection using fundus imaging and optical coherence tomography. The eyes were then collected and prepared for histology. Immunofluorescence was used to quantify Myo/Nog cells, contractile proteins, myofibroblasts and inflammatory cells.
RESULTS: Myo/Nog cells increased in number throughout the eye as PVR progressed. At the highest PVR grades of 3-6, Myo/Nog cells made up the majority of the cells in the ERMs. Besides expressing Noggin and brain angiogenesis inhibitor 1 (BAI1) which specifically identify them, Myo/Nog cells also expressed the muscle proteins alpha smooth muscle actin (α-SMA) and striated muscle myosin II, markers of myofibroblast differentiation. Retinal folds and areas of detachment were overlain by large populations of Myo/Nog cells in the ERMS and the retina itself. Low numbers of cells were labeled with antibodies to the leukocyte markers, CD18, CD45 and CD68 within ERMS and the retina. Small percentages of the Myo/Nog cells expressed these leukocyte markers. Although ARPE-19 cells were found early on in the vitreous, they were rarely seen in the ERMs and most were dying as evidenced by staining with TUNEL reagents. Small populations of pigmented cells were found in some of the ERMS, and some appeared to be migrating from the retinal pigmented epithelium into the retina at higher grades of PVR.
CONCLUSIONS: Myo/Nog cells increase in number and are the source of myofibroblasts in ERMS and the retina in this mouse model of PVR. Injection of human cells did not induce inflammation, and therefore, activation of Myo/Nog cells is likely mediated by the death of ARPE-19 cells, as found in other tissues. Their differentiation into myofibroblasts appears to produce the tractional force that leads to folding in the retina and eventual detachment. PVR is currently treated by surgical removal of ERMs and retinal repair. Using the BAI1 antibody to target and deplete Myo/Nog cells may prevent ERM formation and retinal detachment.
Embargo Period
5-31-2023
Examining the behavior of Myo/Nog cells in epiretinal membrane formation in a mouse model of Proliferative Vitreoretinopathy
INTRODUCTION: Proliferative Vitreoretinopathy (PVR) is a condition of the eye in which membranes form on the epiretinal or subretinal surface of the retina. Sometimes, fibrotic tissue may also form in the retina. These membranes contain myofibroblasts that produce a tractional force on the retina and may lead to detachment and blindness. We have previously shown that human epiretinal membranes (ERMs) contain a large population of Myo/Nog cells that had differentiated into myofibroblast. In the normal eye, small, subpopulations of Myo/Nog cells reside in the retina, lens, ciliary body and cornea. They increase in number, synthesize muscle proteins and differentiate into contractile myofibroblasts in the lens in response to cataract surgery.
PURPOSE: The aim of this study is to examine the behavior of Myo/Nog cells in ERM formation in a mouse model of PVR.
METHODS: Intravitreal injections of gas followed seven days later by injections of the human cell line ARPE-19 were performed to induce PVR. The eyes were monitored and graded for ERM formation one to four weeks after injection using fundus imaging and optical coherence tomography. The eyes were then collected and prepared for histology. Immunofluorescence was used to quantify Myo/Nog cells, contractile proteins, myofibroblasts and inflammatory cells.
RESULTS: Myo/Nog cells increased in number throughout the eye as PVR progressed. At the highest PVR grades of 3-6, Myo/Nog cells made up the majority of the cells in the ERMs. Besides expressing Noggin and brain angiogenesis inhibitor 1 (BAI1) which specifically identify them, Myo/Nog cells also expressed the muscle proteins alpha smooth muscle actin (α-SMA) and striated muscle myosin II, markers of myofibroblast differentiation. Retinal folds and areas of detachment were overlain by large populations of Myo/Nog cells in the ERMS and the retina itself. Low numbers of cells were labeled with antibodies to the leukocyte markers, CD18, CD45 and CD68 within ERMS and the retina. Small percentages of the Myo/Nog cells expressed these leukocyte markers. Although ARPE-19 cells were found early on in the vitreous, they were rarely seen in the ERMs and most were dying as evidenced by staining with TUNEL reagents. Small populations of pigmented cells were found in some of the ERMS, and some appeared to be migrating from the retinal pigmented epithelium into the retina at higher grades of PVR.
CONCLUSIONS: Myo/Nog cells increase in number and are the source of myofibroblasts in ERMS and the retina in this mouse model of PVR. Injection of human cells did not induce inflammation, and therefore, activation of Myo/Nog cells is likely mediated by the death of ARPE-19 cells, as found in other tissues. Their differentiation into myofibroblasts appears to produce the tractional force that leads to folding in the retina and eventual detachment. PVR is currently treated by surgical removal of ERMs and retinal repair. Using the BAI1 antibody to target and deplete Myo/Nog cells may prevent ERM formation and retinal detachment.