RESUMEN
BACKGROUND: Experimental therapeutic approaches to retinal degenerations often require the subretinal injection of a therapeutic agent. The injected volume and the age of the animal can influence the proportion of the retinal surface affected by the subretinal injection. We have investigated the quantitative effect of a single injection in the subretinal space. METHODS: Normal and Royal College of Surgeons rats aged 1 week, 3 weeks or 2 months received subretinal transscleral injections of 1, 3, 5 or 10 microl China ink. After 24 h, animals were killed, injected eyes were enucleated and fixated, and the retinas flattened. An image analyzing program was used to measure the total retinal surface and the retinal surface affected by the dye. RESULTS: The mean retinal surface affected by the injection ranged from 5.24+/-2.76 mm2 to 14.8+/-2.3 mm2, depending on animal age and injected volume. The injection affected 8.79+/-0.89 to 36.9+/-8.13% of total retinal surface. There was no statistically significant difference between normal and Royal College of Surgeons rats. Intravitreal leakage of the dye was more frequent with increasing injection volumes. CONCLUSION: The retinal surface affected by a single subretinal injection increases with the injected volume, but this increase is not proportional. Higher volumes lead to a loss of injected solution, either in the vitreous body or through the sclerotomy. In 2-month-old rats, a 3-microl subretinal injection appears to have the best reproducibility, with 20-30% of retinal surface covered by the injected dye.
Asunto(s)
Carbono , Colorantes/administración & dosificación , Retina/efectos de los fármacos , Animales , Inyecciones , Ratas , Retina/patologíaRESUMEN
We developed an experimental approach with genetically engineered and encapsulated mouse NIH 3T3 fibroblasts to delay the progressive degeneration of photoreceptor cells in dark-eyed Royal College of Surgeons rats. These xenogeneic fibroblasts can survive in 1. 5-mm-long microcapsules made of the biocompatible polymer AN69 for at least 90 days under in vitro and in vivo conditions because of their stable transfection with the gene for the 18-kDa form of the human basic fibroblast growth factor (hFGF-2). Furthermore, when transferred surgically into the vitreous cavity of 21-day-old Royal College of Surgeons rats, the microencapsulated hFGF-2-secreting fibroblasts provoked a local delay of photoreceptor cell degeneration, as seen at 45 days and 90 days after transplantation. This effect was limited to 2.08 mm2 (45 days) and 0.95 mm2 (90 days) of the retinal surface. In both untreated eyes and control globes with encapsulated hFGF-2-deficient fibroblasts, the rescued area (of at most 0.08 mm2) was significantly smaller at both time points. Although, in a few ocular globes, surgical trauma induced a reorganization of the retinal cytoarchitecture, neither microcapsule rejection nor hFGF-2-mediated tumor formation were detected in any treated eyes. These findings indicate that encapsulated fibroblasts secreting hFGF-2 or perhaps other agents can be applied as potential therapeutic tools to treat retinal dystrophies.