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Zengping Liu, Na Yu, Frank Holz, Fang Yang, Boris Stanzel; Engineering a biocompatible cell carrier with nanofeatured topography for retinal pigment epithelium transplantation. Invest. Ophthalmol. Vis. Sci. 2013;54(15):1386.
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An optimal carrier is crucial for retinal pigment epithelium (RPE) tissue engineering. We investigated the influence of fibrillar vs. smooth topography on RPE behavior and subretinal biocompatibility using biodegradable & biostable polymers.
Poly L-lactide/ε-caprolactone (PLCL) or poly ethylene terephthalate (PETP) fibrillar and smooth substrates were prepared by electrospinning or a heating-press method, respectively. Topography was characterized by scanning electron microscopy. Fetal hRPE growth curves were established from substrates seeded at 1×10E4 cells/cm2, while for differentiation cells were seeded at 6×10E4 cells/cm2. Morphology was monitored by phase contrast microscopy. Cultures were stained for tight junctions (ZO-1) at 6 weeks. Commercial membranes (Transwell®, Corning) coated with 200nm diameter PLCL or PETP fibers were implanted into the rabbit subretinal space. Repetitive in vivo images of the implants by SD-OCT and fundus photography were obtained after 4, 7 and 14days, followed by perfusion-fixed histology.
Uniform PLCL fibers were achieved in 209±33, 568±187 & 1132±299nm diameter ranges, while PETP fibers were in wider ranges (175±86 & 993±596nm). RPE attached on all substrates at comparable densities (8958±2495 cells/cm2) at 24 hours. Cell amount on 200nm PLCL was 13.3% higher than on smooth, while increasing fiber diameters decreased cell counts at day 5. Cells on 200nm PETP showed decreased cell amount (33.6%) compared to smooth. In long term cultures, RPE monolayers partially/entirely detached from PLCL (13/15) and PETP (9/15) smooth films. Cell layers were maintained on all fibrillar scaffolds. 200nm PLCL fibers induced superior RPE pigmentation and uniformly hexagonal ZO-1 staining compared to other PLCL fibrillar or smooth surfaces. Intraoperative handling of all implants was safe. The retina overlying PET/PETP or PLCL subretinal implants appeared attached and transparent on ophthalmoscopy, with largely preserved and continuous layering on SD-OCT. On histology, outer nuclear layer thickness was reduced by half and photoreceptors inner segments were preserved in some regions above both implants.
RPE cells showed material and topography-depended proliferation behavior. Scaffolds created by 200nm fiber diameter topography induced superior RPE differentiation. Both substrates were well tolerated in subretinal space.
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