Effective and sustained delivery of hydrophobic retinoids to photoreceptors.
OBJECTIVE
Delivery of hydrophobic compounds to the retina/RPE has been challenging. The purpose of this study was to develop an effective method for the sustained delivery of retinoids to rod and cone photoreceptors of young mice lacking a normal supply of 11-cis retinal.


METHODS
Solubilized basement membrane matrix (Matrigel; BD Biosciences, San Jose, CA) loaded with 9-cis retinal was administered subcutaneously into Rpe65(-/-) mouse pups for assessment of delivery to rods and cones and to Rpe65(-/-)Rho(-/-) mouse pups for assessment of delivery to cones. Intraperitoneal injections of 9-cis retinal were used for comparison. Cone density and opsin localization were evaluated with immunohistochemistry. Cone opsin protein levels were assayed with immunoblots, and cone function was analyzed by electroretinography (ERG) recordings. Retinoid content was determined by high-performance liquid chromatography analysis of retinal extracts. Pigment levels were quantified in homogenized retinas by absorption spectroscopy before and after light exposure.


RESULTS
Single administration of Matrigel loaded with 9-cis retinal to Rpe65(-/-) mice increased cone densities in all analyzed regions of the retina compared with mice treated using intraperitoneal delivery. Cone opsin levels increased to near wild-type levels. Similar treatment in Rpe65(-/-)Rho(-/-) mice increased b-wave ERG amplitudes significantly, indicating the maintenance of cone function. Matrigel was shown to continuously release 9-cis retinal for periods up to 1 week.


CONCLUSIONS
As a method for sustained drug delivery, subcutaneous administration using Matrigel proved more efficacious than intraperitoneal injection for in vivo delivery of retinoids to cone photoreceptors. These experiments are the first to show a sustained delivery of retinoids in mice and suggest a strategy for potential clinical therapeutic development.
Tang
Peter H
PH
Departments of Neuroscience, Medical University of South Carolina, Charleston, South Carolina 29425, USA.
Fan
Jie
J
Goletz
Patrice W
PW
Wheless
Lee
L
Crouch
Rosalie K
RK
D000818:Animals; D015153:Blotting, Western; D002352:Carrier Proteins / Q000235:genetics; D002452:Cell Count; D002851:Chromatography, High Pressure Liquid; D003094:Collagen; D003692:Delayed-Action Preparations / Q000008:administration & dosage; D004224:Diterpenes; D004338:Drug Combinations; D016503:Drug Delivery Systems; D004596:Electroretinography; D005136:Eye Proteins / Q000235:genetics; D019084:Fluorescent Antibody Technique, Indirect; D007274:Injections, Intraperitoneal; D007279:Injections, Subcutaneous; D007797:Laminin; D051379:Mice; D008810:Mice, Inbred C57BL; D018345:Mice, Knockout; D011509:Proteoglycans; D017949:Retinal Cone Photoreceptor Cells / Q000187:drug effects* / Q000378:metabolism; D017948:Retinal Rod Photoreceptor Cells / Q000187:drug effects* / Q000378:metabolism; D012172:Retinaldehyde / Q000008:administration & dosage* / Q000378:metabolism; D012243:Rhodopsin / Q000235:genetics; D019745:cis-trans-Isomerases; D000099178:Retinoid Isomerohydrolase
D002352:Carrier Proteins; D003094:Collagen; D003692:Delayed-Action Preparations; D004224:Diterpenes; D004338:Drug Combinations; D005136:Eye Proteins; D007797:Laminin; D011509:Proteoglycans; D012172:Retinaldehyde; D012243:Rhodopsin; D019745:cis-trans-Isomerases; D000099178:Retinoid Isomerohydrolase; C059485:matrigel; C031390:9-cis-retinal