Person:

Young, Michael

Biodegradable scaffolds play an important adjunct role in transplantation of retinal progenitor cells (RPCs) to the subretinal space. Poly((\epsilon)-Caprolactone) (PCL) scaffolds with different modifications were subretinally implanted in 28 porcine eyes and evaluated by multifocal electroretinography (mfERG) and histology after 6 weeks of observation. PCL Short Nanowire, PCL Electrospun, and PCL Smooth scaffolds were well tolerated in the subretinal space in pigs and caused no inflammation and limited tissue disruption. PCL Short Nanowire had an average rate of preserved overlying outer retina 17% higher than PCL Electrospun and 25% higher than PCL Smooth. Furthermore, PCL Short Nanowire was found to have the most suitable degree of stiffness for surgical delivery to the subretinal space. The membrane-induced photoreceptor damage could be shown on mfERG, but the reductions in P1 amplitude were only significant for the PCL Smooth. We conclude that of the tested scaffolds, PCL Short Nanowire is the best candidate for subretinal implantation.

To determine the effect of membrane brightness on multifocal electroretinograms (mfERGs), we implanted poly lactic-co-glycolic acid (PLGA) membranes in the subretinal space of 11 porcine eyes. We compared membranes with their native shiny white color with membranes that were stained with a blue dye (Brilliant Blue). Histological and electrophysiological evaluation of the overlying retina was carried out 6 weeks after implantation. Histologically, both white and blue membranes degraded in a spongiform manner leaving a disrupted outer retina with no preserved photoreceptor segments. Multifocal ERG revealed the white membranes to have a significantly higher P1-amplitude ratio than the blue (P = 0.027), and a correlation between brightness ratio and P1-amplitude ratio was found (r = 0.762). Based on our findings, we conclude that bright subretinal objects can produce normal mfERG amplitude ratios even when the adjacent photoreceptors are missing. Functional assessment with mfERG in scaffold implant studies should therefore be evaluated with care.

Purpose. Proliferative vitreoretinopathy (PVR) is a complication of retinal detachment characterized by redetachment of the retina as a result of membrane formation and contraction. A variety of retinal cells, including retinal pigment epithelial (RPE) and Müller glia, and growth factors may be responsible. Platelet-derived growth factor receptor alpha (PDGFRα) is found in large quantities in PVR membranes, and is intrinsic to the development of PVR in rabbit models. This study explores the expression of PDGFR in cocultures of RPE and Müller cells over time to examine how these two cell types may collaborate in the development of PVR. We also examine how changes in PDGFRα expression alter Müller cell pathogenicity. Methods. Human MIO-M1 Müller progenitor (MPC) and ARPE19 cells were studied in a transmembrane coculture system. Immunocytochemistry and Western blot were used to look at PDGFRα, PDGFRβ, and GFAP expression. A transfected MPC line cell line expressing the PDGFRα (MIO-M1α) was generated, and tested in a rabbit model for its ability to induce PVR. Results:. The expression of PDGFRα and PDGFRβ was upregulated in MIO-M1 MPCs cocultured with ARPE19 cells; GFAP was slightly decreased. Increased expression of PDGFRα in the MIO-M1 cell line resulted in increased pathogenicity and enhanced ability to induce PVR in a rabbit model. Conclusions:. Müller and RPE cell interaction can lead to upregulation of PDGFRα and increased Müller cell pathogenicity. Müller cells may play a more active role than previously thought in the development of PVR membranes, particularly when stimulated by an RPE-cell-rich environment. Additional studies of human samples and in animal models are warranted.

Purpose The purpose of this study is to evaluate the functional and morphological changes in subretinal xenografts of human retinal progenitor cells (hRPCs) in B6 mice treated with Cyclosporin A (CsA; 210 mg/l in drinking water). Methods: The hRPCs from human fetal eyes were isolated and expanded for transplantation. These cells, with green fluorescent protein (GFP) at 11 passages, were transplanted into the subretinal space in B6 mice. A combination of invasive and noninvasive approaches was used to analyze the structural and functional consequences of the subretinal injection of the hRPCs. The process of change was monitored using spectral domain optical coherence tomography (SDOCT), histology, and electroretinography (ERG) at 3 days, 1 week, and 3 weeks after transplantation. Cell counts were used to evaluate the survival rate with a confocal microscope. ERGs were performed to evaluate the physiologic changes, and the structural changes were evaluated using SDOCT and histological examination. Results: The results of the histological examination showed that the hRPCs gained a better survival rate in the mice treated with CsA. The SDOCT showed that the bleb size of the retinal detachment was significantly decreased, and the retinal reattachment was nearly complete by 3 weeks. The ERG response amplitudes in the CsA group were less decreased after the injection, when compared with the control group, in the dark-adapted and light-adapted conditions. However, the cone-mediated function in both groups was less affected by the transplantation after 3 weeks than the rod-mediated function. Conclusions: Although significant functional and structural recovery was observed after the subretinal injection of the hRPCs, the effectiveness of CsA in xenotransplantation may be a novel and potential approach for increasing retinal progenitor cell survival.