Article

Inner Limiting Membrane Barriers to AAV-mediated Retinal Transduction From the Vitreous

Department of Chemical Engineering, The University of California at Berkeley, Berkeley, California 94720-3190, USA.
Molecular Therapy (Impact Factor: 6.23). 09/2009; 17(12):2096-102. DOI: 10.1038/mt.2009.181
Source: PubMed

ABSTRACT

Adeno-associated viral gene therapy has shown great promise in treating retinal disorders, with three promising clinical trials in progress. Numerous adeno-associated virus (AAV) serotypes can infect various cells of the retina when administered subretinally, but the retinal detachment accompanying this injection induces changes that negatively impact the microenvironment and survival of retinal neurons. Intravitreal administration could circumvent this problem, but only AAV2 can infect retinal cells from the vitreous, and transduction is limited to the inner retina. We therefore sought to investigate and reduce barriers to transduction from the vitreous. We fluorescently labeled several AAV serotype capsids and followed their retinal distribution after intravitreal injection. AAV2, 8, and 9 accumulate at the vitreoretinal junction. AAV1 and 5 show no accumulation, indicating a lack of appropriate receptors at the inner limiting membrane (ILM). Importantly, mild digestion of the ILM with a nonspecific protease enabled substantially enhanced transduction of multiple retinal cell types from the vitreous, with AAV5 mediating particularly remarkable expression in all retinal layers. This protease treatment has no effect on retinal function as shown by electroretinogram (ERG) and visual cortex cell population responses. These findings may help avoid limitations, risks, and damage associated with subretinal injections currently necessary for clinical gene therapy.

Download full-text

Full-text

Available from: David Vernon Schaffer, Jul 27, 2015
    • "In addition to the above indicated barriers, for the treatment of pathologies associated with the back of the eye, drugs have to diffuse through the vitreous humor, a highly dense matrix formed by collagen fibrils and glycosaminoglycans [11]. Alternatively, drugs applied onto the eye can use the trans-scleral pathway, reach the choroids and then surpass the blood–retinal barrier [12]. "
    [Show abstract] [Hide abstract]
    ABSTRACT: The topical route is the most frequent and preferred way to deliver drugs to the eye. Unfortunately, the very low ocular drug bioavailability (less than 5%) associated with this modality of administration, makes the efficient treatment of several ocular diseases a significant challenge. In the last decades, it has been shown that specific nanocarriers can interact with the ocular mucosa, thereby increasing the retention time of the associated drug onto the eye, as well as its permeability across the corneal and conjunctival epithelium. In this review, we comparatively analyze the mechanism of action and specific potential of the most studied nano-drug delivery carriers. In addition, we present the success achieved until now using a number of nanotherapies for the treatment of the most prevalent ocular pathologies, such as infections, inflammation, dry eye, glaucoma, and retinopathies. Copyright © 2015 Elsevier B.V. All rights reserved.
    No preview · Article · Feb 2015 · European Journal of Pharmaceutics and Biopharmaceutics
    • "Interestingly, degenerative processes and thereby changes in the general retinal architecture and especially in the ILM can facilitate the transduction of photoreceptors and RPE after intravitreal AAV application484950. An enzymatic digestion of the ILM and local laser-induced photocoagulation both result in an enhanced capability to transduce the outer retina after intravitreal injections of different AAV serotypes [51,52]. The discussed cell tropisms of the various serotypes are mainly influenced by the capsids affinity to different cell surface receptors. "
    [Show abstract] [Hide abstract]
    ABSTRACT: Adeno-associated virus (AAV) vectors are the most widely used vehicle systems for neuronal gene transfer. This popularity is based on the non-pathogenic nature of AAVs and their versatility making them a multifunctional vector system for basic research and clinical applications. AAVs are successfully applied in clinical and pre-clinical gene therapy studies for inherited retinal disorders. Their excellent transduction profile and efficiency also boosted the use of AAV vectors in basic research. The AAV vector system can be easily modified and adjusted at multiple levels to allow for optimized and specific gene expression in target cells. Here, we will provide an overview on the AAV vector system and its applications focusing on gene transfer into retinal cells. Furthermore, we will outline and discuss strategies for the optimization of AAV gene transfer by modifications to the AAV vector expression cassette, the AAV capsid or the routes of vector administration. Copyright © 2015. Published by Elsevier B.V.
    No preview · Article · Jan 2015 · European Journal of Pharmaceutics and Biopharmaceutics
  • Source
    • "Cite this article as Cold Spring Harb Perspect Med doi: 10.1101/cshperspect.a017418 curring adeno-associated virus serotypes do not penetrate to the outer retina effectively when injected into the vitreous (Dalkara et al. 2009). "
    [Show abstract] [Hide abstract]
    ABSTRACT: It has been possible to use viral-mediated gene therapy to transform dichromatic (red-green color-blind) primates to trichromatic. Even though the third cone type was added after the end of developmental critical periods, treated animals acquired red-green color vision. What happened in the treated animals may represent a recapitulation of the evolution of trichromacy, which seems to have evolved with the acquisition of a third cone type without the need for subsequent modification to the circuitry. Some transgenic mice in which a third cone type was added also acquired trichromacy. However, compared with treated primates, red-green color vision in mice is poor, indicating large differences between mice and monkeys in their ability to take advantage of the new input. These results have implications for understanding the limits and opportunities for using gene therapy to treat vision disorders caused by defects in cone function.
    Full-text · Article · Aug 2014 · Cold Spring Harbor Perspectives in Medicine
Show more