Y-79 retinoblastoma cells: isolation and characterization of clonal lineages

In vitro Model Systems for Studies Into Retinal Neuroprotection

Therapy development for neurodegenerative diseases of the retina constitutes a major unmet medical need, and this may be particularly relevant for inherited diseases of the retina, which are largely untreatable to this day. Therapy development necessitates appropriate models to improve the understanding of the underlying degenerative mechanisms, as well as for the testing and evaluation of novel treatment approaches. This review provides an overview of various in vitro model systems used to study retinal neuroprotection. The in vitro methods and technologies discussed range from primary retinal cell cultures and cell lines, to retinal organoids and organotypic retinal explants, to the cultivation of whole eyeballs. The advantages and disadvantages of these methods are compared and evaluated, also in view of the 3R principles (i.e., the refinement, reduction, and replacement of live animal testing), to identify suitable in vitro alternatives for in vivo experimentation. The article further expands on the use of in vitro models to test and evaluate neuroprotective treatments and to aid the development of retinal drug delivery systems. Among the pharmacological agents tested and characterized in vitro are such that interfere with aberrant cyclic guanosine monophosphate (cGMP) -signaling or such that inhibit the activities of poly (ADP-ribose) polymerase (PARP), histone deacetylases (HDAC), calpain-type proteases, as well as unfolded protein response-related stress. We then introduce nanoparticle-based drug delivery systems and discuss how different in vitro systems may be used to assess their efficacy in the treatment of retinal diseases. The summary provides a brief comparison of available in vitro models and relates their advantages and limitations to the various experimental requirements, for instance, for studies into disease mechanisms, novel treatments, or retinal toxicity. In many cases, combinations of different in vitro models may be required to obtain a comprehensive view of the efficacy of a given retinal neuroprotection approach.

Reproducible high efficiency gene transfer into Y79 retinoblastoma cells using adenofection

Several photoreceptor-specific genes are actively transcribed in Y79 retinoblastoma (Rb) cells, making this cell line potentially useful for the study of photoreceptor metabolism. The utility of these cells is limited because commonly used methods of gene transfer into Y79 cells are inefficient and lack reproducibility. In contrast, we found that adenovirus transduction yields high efficiency gene transfer, however, generation of recombinant adenovirus is lengthy and time consuming. Here, we show that adenofection, a method of coupling adenovirus to plasmid DNA for improved gene transfer, is efficient for gene delivery into Y79 cells. Recombinant adenovirus expressing bacterial lacZ was noncovalently complexed to GFP or luciferase reporter plasmids with polyethylenimine. Efficiency of plasmid gene delivery was determined by monitoring GFP fluorescence. For comparison, calcium phosphate-mediated or cationic lipid transfection was performed in Y79 and HEK293 cells using standard protocols. The adenofection protocol yielded significantly higher efficiencies in Y79 cells than that obtained in these cells with calcium phosphate or cationic lipids. This method will facilitate any experiment requiring reproducible high-level gene transfer. Here, we show that adenofection can be used to analyze activity of the rod photoreceptor PDE6A gene promoter.

Intraretinal xenografts of differentiated human retinoblastoma cells integrate with the host retina

We report on the successful use of chemically modified Y79 human retinoblastoma cells for intraretinal xenografting into damaged adult mammalian eyes. Y79 cells were exposed in vitro to retinoic acid/butyrate to induce differentiation. Using a multisite transplantation method, the suspension was injected into the subretinal space of Fischer 344 rats. The survival, integration, and differentiation potential of these cells was studied, following their return to the intraocular milieu from which the progenitor cells originated. The grafted cells survived and differentiated into immature photoreceptor elements in the subretinal and intraretinal locations, as multiple clusters of rosette-forming cells intimately attached to the host neuroretina. The differentiation process included development of synaptic connectivity of the ribbon type with the surrounding neuropil. No signs of renewed cell division were found within grafts performed on 42 rat eyes, and there was no indication of cell-mediated host reaction against the transplants. This study indicates that tumorigenicity can be suppressed in mitotically arrested Y79 cells, and that these cells are capable of undergoing differentiation in vivo. This provides evidence of the remarkable differentiation properties of human retinoblastomas while indicating that Y79 cells may ultimately be able to substitute for fetal cells in experimental retinal transplantation.

Retinoblastoma cell lines Y79, RB355 and WERI-Rb27 are genetically related

Genesis of the childhood ocular tumor retinoblastoma results from the mutational inactivation of a single gene, RB, located on chromosome 13. Cultured cells or cell lines derived from retinoblastomas have been extensively studied for insight into mutational mechanisms of RB inactivation, functional properties of wild-type RB alleles, and pathways of retinal differentiation. Three such cell lines (Y79, RB355 and WERI-Rb27) were previously shown to have similar, heterozygous rearrangements of their RB genes, suggesting a common mutational mechanism affecting a specific region of the gene. This proposal was based on the premise that all three mutations occurred independently. By using molecular analyses of human genetic polymorphisms, we now show that these three cell lines are in fact genetically related, despite their different origins, morphologies, growth characteristics, and karyotypes. Interpretation of these and other published data suggest that both RB355 and WERI-Rb27 are probably sublines of Y79.