Efficient cochlear gene transfection in guinea-pigs with adeno-associated viral vectors by partial digestion of round window membrane

Abstract

The auditory portion of the inner ear, the cochlea, is an ideal organ for local gene transfection owing to its relative isolation. Various carriers have been tested for cochlear gene transfection. To date, viral vectors appear to have much higher transfection efficacy than non-viral mechanisms. Among these vectors, recombinant adeno-associated virus (rAAV) vectors have several advantages such as being non-pathogenic and the ability to produce prolonged gene expression in various cell types. However, rAAV vectors cannot pass through the intact round window membrane (RWM), otherwise a very attractive approach to access the human inner ear. In this study, performed in guinea-pigs, we describe a method to increase the permeability of RWM to rAAV vectors by partial digestion with collagenase solution. Elevated delivery of rAAV across the partially digested RWM increased transfection efficacy to a satisfactory level, even though it was still lower than that achieved by direct cochleostomy injection. Functional tests (auditory brainstem responses) showed that this enzymatic manipulation did not cause permanent hearing loss if applied appropriately. Morphological observations suggested that the damage to RWM caused by partial digestion healed within four weeks. Taken together, these findings suggest that partial digestion of the RWM is a safe and effective method for increasing the transfection of cochlear sensory cells with rAAV.

Cochlear gene therapy with ancestral AAV in adult mice: complete transduction of inner hair cells without cochlear dysfunction

“…Others have injected GFP-expressing AAV vectors into the normal adult ear, as in the present study, to evaluate the effectiveness of different delivery routes or viral serotypes in either mice16172024, rat25 or guinea pig38. Although the most successful of these prior studies reports near 100% transfection of IHCs in the base of the cochlea after round window injection20, most report significantly less than that, e.g.…”

“…Although the most successful of these prior studies reports near 100% transfection of IHCs in the base of the cochlea after round window injection20, most report significantly less than that, e.g. ~30%17 and ~80%38, and all report only 0–20% transduction in the cochlear apex172038. Similarly, although four prior studies have looked at virus delivery via a posterior canal route22232425, none convincingly demonstrated a high targeting efficiency for hair cells throughout the cochlear spiral.…”

“…Several delivery strategies have been developed that access the cochlear fluids directly from that portion of the cochlear basal turn facing the middle-ear space. These approaches include: (1) a cochleostomy into either scala tympani or scala media1718224142, (2) injection through the round window membrane5172043, (3) or injection onto the surface of the round window, with or without manipulations to increase penetration38444546. The approach to the posterior canal differs in that the access is not through the middle ear22232425.…”

Thérapie génique des surdités humaines

“…Des avancées significatives ont été obtenues concernant la voie d'administration dans la cochlée. L'expression du transgène a été détectée lorsqu'on applique une éponge de gélatine résorbable imbibée de la préparation virale sur la membrane de la fenêtre ronde partiellement perméabilisée par la collagénase [22]. Une autre étude a montré que le traitement de la membrane de la fenêtre ronde par l'acide hyaluronique augmente la proportion des cellules ciliées transfectées [23].…”

Polybrene: Observations on cochlear hair cell necrosis and minimal lentiviral transduction of cochlear hair cells

“…Over the past decade, gene delivery to the cochlea has progressed rapidly in terms of the development of both viral and nonviral vectors [9,17,19]. However, the transduction efficiency of cochlear cells, especially hair cells (HCs), remains low.…”