Abstract
Purpose::
The main objective was to utilize microchanneled 3-D surfaces to provide an environment and structural support to promote the maintenance of the photoreceptor (PR) cell’s native elongated shape in cell culture.
Methods::
Poly(dimethylsiloxane) (PDMS) was used to create the microchanneled surface. A patterned relief mold was used to cast PDMS with parallel microchannels (1.5microns wide and 1.5microns deep) separated with 2.5microns wide ridges. The surface was further modified to promote better cell attachment by oxidation with a Tesla coil electrical discharge followed by modification with wheat germ agglutinin (WGA), for selective attachment of rod cells. Dissociated PRs were obtained from isolated retinas of 21-days old Long-Evans rats and seeded on the surfaces for a week. The PR cell’s ability to attach to the surface and the extent of morphological changes were evaluated through immunocytochemistry. A comparison of the number of elongated cells in microchanneled surfaces vs. control surfaces was made by measuring the circularity ratio of each cell on the respective surface. A value of 1 indicated a perfect circular cell, while values closer to 0 indicated an elongated cell. Elongated cells were identified as rod cells by immunolabeling with anti-rhodopsin.
Results::
On microchanneled surfaces, there was 110% and 64% more occurrence of cells with circularity ratios in between 0-0.2 and 0.2-0.4, respectively, than on control surfaces. In the other hand, on control surfaces there was 8.8% and 27% more occurrence of cells with circularity ratios in between 0.6-0.8 and 0.8-1, respectively, than on microchanneled surfaces. In addition, the average circularity ratio on microchanneled surfaces (0.6254 ± 0.0509) was found to be significantly less than in controls (0.7023 ± 0.0722) (p<0.05).
Conclusions::
Given that cells with elongated properties have circularity ratios in between 0.1-0.4 and that cells with circular properties in between 0.6-1, our results suggest that microchannels facilitate rods to retain their in vivo shape and/or elongation.
Keywords: photoreceptors • microscopy: light/fluorescence/immunohistochemistry • retinal culture