A biodegradable scaffold enhances differentiation of embryonic stem cells into a thick sheet of retinal cells.

Retinal degeneration is a leading cause of blindness in developed countries. Stem cells can be differentiated into retinal organoids to study mechanisms of retinal degeneration, develop therapeutic agents, and potentially serve as replacement tissues. The spherical nature of these retinoids limits their utility, because the investigator lacks ready access to both sides of the neo-tissue. For tissue-replacement, spherical retinoids are unable to interact simultaneously with the host retinal pigment epithelium and remaining neurosensory retina. To attempt making a planar retinoid, we developed a biodegradable scaffold that simulates the extracellular matrix of the neurosensory retina. Human embryonic stem cells were seeded on the scaffold. Differentiation into retinal cells was confirmed by quantitative RT-PCR, confocal immunocytochemistry, and immunoblotting. The scaffold favored differentiation into retinal cell types over other anterior forebrain cells, but retinal lamination was rudimentary. The cultures elicited a minimal immune response when implanted into the subretinal space of a mouse model of retinal degeneration. The implants survived for at least 12 weeks, but there was evidence of cytoplasmic transfer rather than implantation into the outer nuclear layer (photoreceptor layer). However, some implanted cells migrated to the inner layers of the retina and established elaborate arbors of neurites.

Combined silicone oil removal with secondary implantation of anterior chamber or sclera-fixed posterior chamber intraocular lenses.

PURPOSE: To compare the outcomes and complication rates of silicone oil removal (SOR) combined with secondary implantation of modern anterior chamber intraocular lenses (AC IOLs) versus scleral-fixated, posterior chamber IOLs (SF IOLs) in patients who lack capsular support.
 METHODS: A prospective, nonrandomized study was performed to compare 2 groups of patients between January 2006 and February 2011. Forty eyes of 40 patients undergoing AC IOL implantation (group 1) and 34 eyes of 34 patients undergoing SF IOL implantation (group 2) were included. The mean follow-up was 22.3 ± 6.3 (range 6-42) months. 
 RESULTS: The mean postoperative corrected distance visual acuity (CDVA) recorded at the last follow-up in groups 1 and 2 was 0.70 ± 0.50 and 0.65 ± 0.55, respectively (p = 0.71). A total of 35 eyes (87.5%) and 29 eyes (85.3%) in groups 1 and 2 had an improved or unchanged CDVA; 5 eyes (12.5%) and 5 eyes (14.7%) had a deteriorated CDVA. The most frequent postoperative complications in the 2 groups were transient corneal edema, elevated intraocular pressure, hypotony, and retinal detachment. The differences in the number of eyes and the total number of complications were not statistically significant for early (p = 0.06) and late (p = 0.13) complications between the 2 groups. 
 CONCLUSIONS: Both secondary AC IOL and SF IOL implantation with simultaneous pars plana approach of SOR are suitable for treating silicone oil-filled, aphakic eyes. No significant difference in visual outcome or major complication rates was found between the 2 groups.

Claudin-19 and the barrier properties of the human retinal pigment epithelium.

PURPOSE: The retinal pigment epithelium (RPE) separates photoreceptors from choroidal capillaries, but in age-related macular degeneration (AMD) capillaries breach the RPE barrier. Little is known about human RPE tight junctions or the effects of serum on the retinal side of the RPE. METHODS: Cultured human fetal RPE (hfRPE) was assessed by the transepithelial electrical resistance (TER) and the transepithelial diffusion of methylated polyethylene glycol (mPEG). Claudins and occludin were monitored by quantitative RT-PCR, immunoblotting, and immunofluorescence. RESULTS: Similar to freshly isolated hfRPE, claudin-19 mRNA was 25 times more abundant than claudin-3. Other detectable claudin mRNAs were found in even lesser amounts, as little as 3000 times less abundant than claudin-19. Claudin-1 and claudin-10b were detected only in subpopulations of cells, whereas others were undetectable. Knockdown of claudin-19 by small interfering RNA (siRNA) eliminated the TER. siRNAs for other claudins had minimal effects. Serum affected tight junctions only when presented to the retinal side of the RPE. The TER increased 2 times, and the conductance of K(+) relative to Na(+) decreased without affecting the permeability of mPEG. These effects correlated with increased steady-state levels of occludin. CONCLUSIONS: Fetal human RPE is a claudin-19-dominant epithelium that has regional variations in claudin-expression. Apical serum decreases RPE permeability, which might be a defense mechanism that would retard the spread of edema due to AMD.

Minimal effects of VEGF and anti-VEGF drugs on the permeability or selectivity of RPE tight junctions.

PURPOSE: Bevacizumab and ranibizumab are currently used to treat age-related macular degeneration by neutralizing vascular endothelial growth factor (VEGF). In this study, the potential side effects on the outer blood-retinal barrier were examined. METHODS: Human fetal RPE (hfRPE) cells were used because they are highly differentiated in culture. The claudin composition of RPE tight junctions was determined by RT-PCR, immunoblot analysis, and immunofluorescence. ELISA assays monitored the secretion and trafficking of VEGF and a fluid-phase marker, methylpolyethylene glycol (mPEG). Tight junction functions were assessed by the conductance of K(+) and Na(+) (derived from the transepithelial electrical resistance, TER) and the flux of NaCl and mPEG. RESULTS: Claudin-3, claudin-10, and claudin-19 were detected in RPE tight junctions. VEGF was secreted in equal amounts across the apical and basolateral membranes, but the apical membrane was more active in endocytosing and degrading VEGF. Exogenous VEGF and mPEG crossed the RPE monolayer by transcytosis, predominantly in the apical-to-basal direction. RPE tight junctions were selective for K(+), but did not discriminate between Na(+) and Cl(-). VEGF, bevacizumab, and ranibizumab had minimal effects on TER, permeation of mPEG, and selectivity for K(+), Na(+), and Cl(-). They had minimal effects on the expression and distribution of the claudins. CONCLUSIONS: RPE has mechanisms for maintaining low concentrations of VEGF in the subretinal space that include endocytosis and degradation and fluid-phase transcytosis in the apical-to-basal direction. RPE tight junctions are selective for K(+) over Na(+) and Cl(-). Permeability and selectivity of the junctions are not affected by VEGF, bevacizumab, or ranibizumab.