Ivan Fernandez-Bueno

Elastin-like recombinamers as substrates for retinal pigment epithelial cell growth

The aim of this study is to investigate the use of elastin-like recombinamers (ELRs) as a substrate that can maintain the growth, phenotype, and functional characteristics of retinal pigment epithelial (RPE) cells efficiently and as a suitable carrier for the transplantation of autologous RPE cells for treatment of age-related macular degeneration (AMD). ELR films containing a bioactive sequence, RGD (ELR-RGD), and one with no specific sequence (ELR-IK) as control, were obtained by solvent-casting onto glass and subsequent cross-linking. ARPE19 cells were seeded on sterilized ELR films as well as on the control surfaces. Cells were analysed after 4, 24, 72, and 120 h to study cell adhesion, proliferation, cell viability, morphology, and specificity by staining with Trypan blue, DAPI, Rhodamin-Phalloidin and RPE65, ZO-1 antibodies and observing under fluorescence as well as electron microscope. ARPE19 cells seeded on both ELR films and controls were 100% viable and maintained their morphology and set of characteristics at the different time points studied. Cell proliferation on ELR-RGD was significantly higher than that found on ELR-IK at all time points, although it was less than the growth rate on polystyrene. ARPE19 cells grow well on ELR-RGD maintaining their phenotype. These results should be extended to further studies with fresh human RPE cells and in vivo studies to determine whether this ELR-RGD matrix could be used as a Bruchs membrane prosthesis and carrier for transplantation of RPE cells in patients suffering with AMD.

Time course modifications in organotypic culture of human neuroretina

The purpose of this study was to characterize organ culture of human neuroretina and to establish survival and early degeneration patterns of neural and glial cells. Sixteen neuroretina explants were prepared from 2 postmortem eyes of 2 individuals. Four explants were used as fresh retina controls, and 12 were evaluated at 3, 6, and 9 days of culture. Neuroretina explants (5 × 5 mm) were cultured in Transwell(®) dishes with the photoreceptor layer facing the supporting membrane. Culture medium (Neurobasal A-based) was maintained in contact with the membrane beneath the explant. Cryostat and ultrathin sections were prepared for immunohistochemistry and electron microscopy. Neuroretinal modifications were evaluated after toluidine blue staining and after immunostaining for neuronal and glial cell markers. Ultrastructural changes were analyzed by electron microscopy. From 0 to 9 days in culture, there was progressive retinal degeneration, including early pyknosis of photoreceptor nuclei, cellular vacuolization in the ganglion cell layer, decrease of both plexiform layer thicknesses, disruption and truncation of photoreceptor outer segments (OS), and marked reduction in the number of nuclei at both nuclear layers where the cells were less densely packed. At 3 days there was swelling of cone OS with impairment of pedicles, loss of axons and dendrites of horizontal and rod bipolar cells that stained for calbindin (CB) and protein kinase C (PKC-α), respectively. After 9 days, horizontal cells were pyknotic and without terminal tips. There were similar degenerative processes in the outer plexiform layer for rod bipolar cells and loss of axon terminal lateral varicosities in the inner plexiform layer. Glial fibrillary acidic protein (GFAP) staining did not reveal a dramatic increase of gliosis in Müller cells. However, some Müller cells were CB immunoreactive at 6 days of culture. Over 9 days of culture, human neuroretina explants underwent morphological changes in photoreceptors, particularly the OS and axon terminals, and in postsynaptic horizontal and bipolar cells. These early changes, not previously described in cultured human samples, reproduce some celullar modifications after retinal damage. Thus, this model may be suitable to evaluate therapeutic agents during retinal degeneration processes.

ACUTE RETINAL DAMAGE AFTER USING A TOXIC PERFLUORO-OCTANE FOR VITREO-RETINAL SURGERY

Purpose: To describe a series of retinal acute toxicity cases with severe visual loss after intraocular use of a toxic perfluoro-octane (PFO). The clinical presentation is described, and the likely causes are analyzed. New biological methods for testing safety of intraocular medical devices are proposed. Methods: Information regarding a series of eyes suffering acute severe events after intraocular use of a toxic PFO was analyzed. Four types of spectroscopy, nuclear magnetic resonance, and chromatography were used to identify the potential PFO contaminants. Cultures of human retinal pigment epithelial cells (ARPE-19) and porcine neuroretina were used to quantify the toxicity of the suspect PFO lots. Results: Of 117 cases of intraocular toxicity, 96 were considered clearly related to the use of PFO. Fifty-three cases had no light perception, and 97 had no measurable visual acuity. Retinal necrosis (n = 38) and vascular occlusion (n = 33) were the most characteristic findings. Two hydroxyl compounds, perfluorooctanoic acid and dodecafluoro-1-heptanol, and benzene derivatives were identified as the suspected toxic agents. While existing toxicity testing failed, we proposed new tests that demonstrated clear toxicity. Conclusion: Protocols to determine cytotoxicity of intraocular medical devices should be revised to assure safety. Acute toxic events should be reported to health authorities and scientific media.

Flow cytometry assessment of the purity of human retinal pigment epithelial primary cell cultures

Culturing of human retinal pigment epithelial cells (hRPE) is the initial step in cell therapy of some retinal diseases. To transfer these cells into clinical use, it is necessary to guarantee that they are well differentiated and contamination free. Fluorescence microscopy is the easiest method to do this, but it is associated with operator subjectivity, and the results are highly variable. The aim of this study was to demonstrate the practicality of implementing flow cytometry (FC) analysis to determine the purity of human RPE primary cell cultures. An ARPE19 cell line, human skin fibroblasts, hRPE, and human corneal epithelial cells were analysed by FC to determine the percentage of the hRPE population expressing RPE65 and epithelial and fibroblast proteins. The cell viability and DNA content also were determined. FC analysis showed that the hRPE cells were healthy, stable, and expressed RPE65 protein in the study working conditions. The density of RPE65 protein expression decreased during passages 2 to 10, which was confirmed using a Western blot technique. However, the hRPE cells did not express the 112-kDa epithelial and fibroblast proteins in the current working conditions. These findings suggested that FC facilitates a detailed analysis of human RPE primary cell cultures, a necessary step in developing new cell therapies for retinal diseases.

Histology and immunochemistry evaluation of autologous translocation of retinal pigment epithelium‐choroid graft in porcine eyes

Purpose:  To evaluate structure and cellular functionality of retinal pigment epithelium (RPE)‐choroid grafts after autologous translocation in porcine eyes.

Comparison between direct contact and extract exposure methods for PFO cytotoxicity evaluation

A series of recent acute blindness cases following non–complicated retinal detachment surgery caused the release of several health alerts in Spain. The blindness was attributed to certain lots of perfluoro-octane (PFO; a volatile and transient medical device). Similar cases have been reported in other countries. This has raised questions regarding the validity of cytotoxicity test methods currently used to certify the safety of PFO lots. The tests were performed according to the International Organization for Standardization (ISO) norms, using the extract dilution method or the indirect contact method as applied to L929 cells, a line derived from mouse fibroblasts. The limitations of those methods have been resolved in this study by proposing a new cytotoxicity test method for volatile substances. The new method requires direct contact of the tested substance with cells that are similar to those exposed to the substance in the clinical setting. This approach includes a few new technical steps that are crucial for detecting cytotoxicity. Our new method detected toxic PFO lots that corresponded to the lots producing clinical blindness, which previous methods failed to detect. The study suggests applying this new method to avoid occurrence of such cases of blindness.

Mesenchymal stem cell therapy in retinal and optic nerve diseases: An update of clinical trials

Retinal and optic nerve diseases are degenerative ocular pathologies which lead to irreversible visual loss. Since the advanced therapies availability, cell-based therapies offer a new all-encompassing approach. Advances in the knowledge of neuroprotection, immunomodulation and regenerative properties of mesenchymal stem cells (MSCs) have been obtained by several preclinical studies of various neurodegenerative diseases. It has provided the opportunity to perform the translation of this knowledge to prospective treatment approaches for clinical practice. Since 2008, several first steps projecting new treatment approaches, have been taken regarding the use of cell therapy in patients with neurodegenerative pathologies of optic nerve and retina. Most of the clinical trials using MSCs are in I/II phase, recruiting patients or ongoing, and they have as main objective the safety assessment of MSCs using various routes of administration. However, it is important to recognize that, there is still a long way to go to reach clinical trials phase III-IV. Hence, it is necessary to continue preclinical and clinical studies to improve this new therapeutic tool. This paper reviews the latest progress of MSCs in human clinical trials for retinal and optic nerve diseases.

Chitosan feasibility to retain retinal stem cell phenotype and slow proliferation for retinal transplantation

Retinal stem cells (RSCs) are promising in cell replacement strategies for retinal diseases. RSCs can migrate, differentiate, and integrate into retina. However, RSCs transplantation needs an adequate support; chitosan membrane (ChM) could be one, which can carry RSCs with high feasibility to support their integration into retina. RSCs were isolated, evaluated for phenotype, and subsequently grown on sterilized ChM and polystyrene surface for 8 hours, 1, 4, and 11 days for analysing cell adhesion, proliferation, viability, and phenotype. Isolated RSCs expressed GFAP, PKC, isolectin, recoverin, RPE65, PAX-6, cytokeratin 8/18, and nestin proteins. They adhered (28 ± 16%, 8 hours) and proliferated (40 ± 20 cells/field, day 1 and 244 ± 100 cells/field, day 4) significantly low (P < 0.05) on ChM. However, they maintained similar viability (>95%) and phenotype (cytokeratin 8/18, PAX6, and nestin proteins expression, day 11) on both surfaces (ChM and polystyrene). RSCs did not express alpha-SMA protein on both surfaces. RSCs express proteins belonging to epithelial, glial, and neural cells, confirming that they need further stimulus to reach a final destination of differentiation that could be provided in in vivo condition. ChM does not alternate RSCs behaviour and therefore can be used as a cell carrier so that slow proliferating RSCs can migrate and integrate into retina.

Histologic Characterization of Retina Neuroglia Modifications in Diabetic Zucker Diabetic Fatty Rats

Purpose The purpose of this study was to characterize retinal degenerative morphologic modifications in Zucker Diabetic Fatty (ZDF) rats, a genetic model of type 2 diabetes, by histologic and immunohistochemical evaluation. Methods Male lean (?/+; n = 10) and ZDF (fa/fa; n = 20) rats were used. At 24 weeks of age, body weights and blood glucose levels were determined. Eyes were removed and processed for paraffin wax embedding. Sections through the optic disc were stained for hematoxylin and eosin or immunostained for TUNEL, advanced glycation end products (AGEs), glial fibrillary acidic protein (GFAP), glutamate/aspartate transporter (GLAST), isolectin B4, recoverin, retinal pigment epithelium-specific 65-kDa protein, rhodopsin, vimentin, and zonula occludens protein 1. Retinal morphometry, cell counts, glial activation degree and immunoreactivity of AGEs and GLAST were also determined. Results ZDF rats were observed to be diabetic from week 9 and by week 24. These animals showed retinal morphologic degenerative changes, increased neuroretinal thickness, and decreased number of nuclei. Glial cells activation with massive GFAP upregulation was present. Cellular morphologic modifications were also observed. GLAST immunofluorescence was decreased, whereas AGEs were increased in comparison with lean rats. Conclusions Spontaneous development of diabetes in ZDF rats results in neuroglia morphologic degenerative changes at 24 weeks of age. This animal model may be useful to understand the pathogenesis of diabetic retinopathy and to screen neuroprotective drugs in diabetes.

Safety and Biocompatibility of a New High-Density Polyethylene-Based Spherical Integrated Porous Orbital Implant: An Experimental Study in Rabbits.

Purpose. To evaluate clinically and histologically the safety and biocompatibility of a new HDPE-based spherical porous orbital implants in rabbits. Methods. MEDPOR (Porex Surgical, Inc., Fairburn, GA, USA), OCULFIT I, and OCULFIT II (AJL Ophthalmic S.A., Vitoria, Spain) implants were implanted in eviscerated rabbis. Animals were randomly divided into 6 groups (n = 4 each) according to the 3 implant materials tested and 2 follow-up times of 90 or 180 days. Signs of regional pain and presence of eyelid swelling, conjunctival hyperemia, and amount of exudate were semiquantitatively evaluated. After animals sacrifice, the implants and surrounding ocular tissues were processed for histological staining and polarized light evaluation. Statistical study was performed by ANOVA and Kaplan-Meier analysis. Results. No statistically significant differences in regional pain, eyelid swelling, or conjunctival hyperemia were shown between implants and/or time points evaluated. However, amount of exudate differed, with OCULFIT I causing the smallest amount. No remarkable clinical complications were observed. Histological findings were similar in all three types of implants and agree with minor inflammatory response. Conclusions. OCULFIT ophthalmic tolerance and biocompatibility in rabbits were comparable to the clinically used MEDPOR. Clinical studies are needed to determine if OCULFIT is superior to the orbital implants commercially available.