Migration of retinal cells through a perforated membrane: implications for a high-resolution prosthesis.
OBJECTIVE
One of the critical difficulties in design of a high-resolution retinal implant is the proximity of stimulating electrodes to the target cells. This is a report of a phenomenon of retinal cellular migration into a perforated membrane that may help to address this problem.


METHODS
Mylar membranes with an array of perforations (3-40 microm in diameter) were used as a substrate for in vitro retinal culture (chicken, rats) and were also transplanted into the subretinal space of adult RCS rats. A membrane was also constructed with a seal on one side to restrict the migration.


RESULTS
Retinal tissue in vitro grew within 3 days through perforations of greater than 5 microm in diameter when the membranes were positioned on the photoreceptor side, but no migration occurred if the implant was placed on the inner retinal surface. Histology with light microscopy and transmission electron microscopy (TEM) demonstrated that migrating cells retain neuronal structures for signal transduction. Similar growth of RCS rat retinal cells occurred in vivo within 5 days of implantation. A basal seal kept the migrating tissue within a small membrane compartment.


CONCLUSIONS
Retinal neurons migrate within a few days into perforations (> 5 microm in diameter) of a membrane placed into the subretinal space. This may provide a means of gaining close proximity between electrodes in a retinal prosthetic chip and target cells, and thus allow a greater density of stimulating elements to subserve higher resolution. Further studies are needed to explore the long-term stability of the retinal migration.
Department of Ophthalmology, School of Medicine, Stanford University, CA 94305-4085, USA. palanker@standord.edu
Daniel
D
Palanker
Philip
P
Huie
Alexander
A
Vankov
Robert
R
Aramant
Magdalene
M
Seiler
Harvey
H
Fishman
Michael
M
Marmor
Mark
M
Blumenkranz
D000818:Animals; D000831:Animals, Newborn; D002465:Cell Movement; D002642:Chick Embryo; D066298:In Vitro Techniques; D008567:Membranes, Artificial; D008854:Microscopy, Electron; D009474:Neurons / Q000502:physiology / Q000648:ultrastructure; D019736:Prostheses and Implants; D051381:Rats; D017207:Rats, Sprague-Dawley; D012160:Retina / Q000166:cytology / Q000502:physiology* / Q000601:surgery* / Q000648:ultrastructure; D013997:Time Factors
D008567:Membranes, Artificial