Synaptic plasticity in mammalian photoreceptors prepared as sheets for retinal transplantation.
OBJECTIVE
To investigate systematically the early morphologic changes in axon terminals of adult mammalian rod and cone photoreceptors prepared as a sheet for subretinal transplantation.


METHODS
An in vitro system was designed to maintain adult porcine retinas for up to 48 hours. Photoreceptor sheets, prepared by vibratome sectioning, and full-thickness retinas were cultured at temperatures similar to those in pretransplantation storage (4 degrees C) and after transplantation (37 degrees C). Changes in the outer nuclear and outer plexiform layers were analyzed, using immunohistochemistry, laser scanning confocal microscopy, and image analysis.


RESULTS
Morphologic changes were observed in photoreceptor sheets as early as 10 minutes after incubation. The most significant change was the retraction of photoreceptor axons and terminals toward their cell bodies. Retraction was temperature dependent, being exacerbated at 37 degrees C compared with 4 degrees C, at its maximum by 24 hours of culture, and present in sheets obtained from both superior and inferior retina. The cause of this movement was not preparation techniques associated with vibratome sectioning or gelatin removal. Retraction was also present in full-thickness neural retina incubated at 37 degrees C. Reduction in outer nuclear layer cell counts and thickness were also evident in these preparations, primarily in photoreceptor sheets.


CONCLUSIONS
Adult photoreceptor sheets, a potential graft preparation for retinal transplantation, show a rapid retraction of axon terminals toward the cell bodies during culture. Although retraction may impede synaptic integration after transplantation, this intrinsic plasticity could be redirected to stimulate graft-host interaction.
Department of Neurosciences, Graduate School of Biomedical Sciences, University of Medicine and Dentistry of New Jersey, Newark, New Jersey 07103, USA. khodaimo@umdnj.edu
Mohamad A
MA
Khodair
Marco A
MA
Zarbin
Ellen
E
Townes-Anderson
D000818:Animals; D002469:Cell Separation; D005260:Female; D019084:Fluorescent Antibody Technique, Indirect; D007091:Image Processing, Computer-Assisted; D008297:Male; D008562:Membrane Glycoproteins / Q000378:metabolism; D018613:Microscopy, Confocal; D009419:Nerve Tissue Proteins / Q000378:metabolism; D009473:Neuronal Plasticity / Q000502:physiology*; D009924:Organ Culture Techniques; D020419:Photoreceptor Cells, Vertebrate / Q000166:cytology / Q000502:physiology / Q000637:transplantation*; D017729:Presynaptic Terminals / Q000502:physiology*; D012160:Retina / Q000601:surgery*; D013552:Swine; D016708:Synaptophysin / Q000378:metabolism
D008562:Membrane Glycoproteins; D009419:Nerve Tissue Proteins; C489782:SVP-38 protein, human; C489618:Sv2a protein, rat; D016708:Synaptophysin