Abstract
Purpose: :
To investigate tissue stretch in the lateral plane as a factor for retinal cell survival in vitro.
Methods: :
Full-thickness retinal sheets (~12x12mm) were isolated from adult porcine eyes and cultured for 10 days under four conditions: 1) standard procedure with the retinal explant placed on a culture membrane; 2) addition of lateral stretch using a magnet system (ring magnet under the culture membrane with four small magnets on top of the retina fixing it to the membrane); 3) addition of the ring magnet, but no stretch; and 4) free-floating in culture medium. The grafts were analyzed morphologically using hematoxylin and eosin staining and immunohistochemistry.
Results: :
Hematoxylin and eosin (H&E) staining showed that after 10 days group 1 (standard) had degenerated into a pyknotic cell mass with no discernible nuclear layers. Inner (IS) and outer segments (OS) were absent. GFAP labeling showed a strong up-regulation. Group 2 (stretch) displayed a laminated morphology with well-populated nuclear layers and well preserved IS and OS in H&E staining. GFAP labeling displayed weak labeling of the nerve fiber layer (NFL) and vertical fibers terminating in the outer limiting membrane. Group 3 (magnet control) displayed laminar architecture of the retina in H&E staining, however, the sections appeared edematous with widespread cell death and vacuolization in all layers. Some IS, and occasional OS were present. GFAP labeling showed low-level up-regulation in the NFL, as well as weak labeling of vertical fibers. H&E of group 4 (free-floating) showed a complete loss of retinal architecture with only a few remaining cells. GFAP labeling of scattered structures was present. Statistical analysis of rows of rhodopsin and NeuN labeled cells showed that the number of surviving cells in group 2 (stretch) was far greater than in any other group (p<0.001; one-way ANOVA).
Conclusions: :
Biomechanical factors related to cell survival within the retina are yet to be extensively investigated. In vivo, the retina is stretched against the retinal pigment epithelium mechanically through the force of the intraocular pressure. In this study, we have created an in vitro model to explore the biomechanical stretching force, and we here show that it is an important factor for preservation of the retinal laminar structure as well as cell survival.
Keywords: retinal culture • retinal connections, networks, circuitry • retinal degenerations: cell biology