Functional Properties of Intravitreous Migrated Cells in Patients With Proliferative Vitreoretinopathy

Abstract

Abstract: : Purpose: The first step in pathogenesis of proliferative vitreoretinopathy (PVR) is thought that some kinds of cells from the subretinal space and the retina migrate into the vitreous. However, their identification and function of cell types have not been well established. Retinal pigment epithelial (RPE) cells are believed as the predomionant cell types in this disease. RPE has unique inward rectifying potassium (Kir) channel, which is functionally specific to RPE. In this study, the functional properties of Kir currents in the intravitreous migrated cells obtained from PVR patients were investigated. Methods:Clinical samples were obtained at the beginning of pars plana vitrectomy from 2 eyes of 2 patients with PVR. Whole cell currents in the intravitreous cells were recorded using the patch clamp technique with 135 mM K₊ and 4 mM ATP in the pipette. Kir currents were measured as the Ba₂₊-sensitive components. To investigate the permeation properties for K₊ and Rb₊, the relative inward conductance (G_Rb/G_K) based on the chord conductance for each cation at -150 mV was measured by replacing 140 mM K₊ in the bath with 140 mM Rb₊. Results:Under the microscope, most of the cells in the vitreous were appeared as round-shaped single cell, and two types of cells were observed. One was pigment cell (PC) (n=6) and the other was non-pigment cell (NPC) (n=7). Initial membrane potentials were -68.2 ±3.35 mV in PC and-66.1 ±4.29 mV in NPC. All cells showed no voltage-dependent sodium currents. All PC exhibited mild Kir currents and G_Rb/G_K was unusually high (6.24±1.38; n=6), which was characteristic of RPE cells. Three of 7 NPC showed the same functional properties of Kir channel as pigment cells, in contrast 4 of 7 exhibited distinct Kir currents but its G_Rb/G_K was low (0.47±0.13; n=4), which was seen in ordinary Kir currents. Conclusion:In this study, there were functionally two types of cells in the vitreous obtained from PVR patient. One was the same as RPE cells and the other was different from RPE, which suggest that the intravitreous cells in PVR were originated from not only RPE cells but other glial cells such as Muller cells or astrocytes. Interestingly, even NPC had the same functional characters of RPE, which suggests some RPE cells in the vitreous lost their pigments .

Keywords: 524 proliferative vitreoretinopathy • 445 ion channels • 342 cell membrane/membrane specializations