Abstract
Purpose :
During the past decade, more and more evidence has supported the role of ceramide as a mediator of photoreceptor dysfunction or cell death in both ceramide accumulation and deficiency contexts. TLCD3B, a novel ceramide synthase, was identified in addition to the 6 canonical ceramide synthases (CerSs), and the Tlcd3b−/− mouse model exhibited both retinal dysfunction and retinal degeneration. Given that previous canonical CerSs-deficient mouse models failed to display retinal degeneration, how Tlcd3b interacts with other CerSs has not been investigated. In addition, as the profile of the product of each CerS is distinct, whether the overall level or the homeostasis of different ceramide species plays a critical role in photoreceptor degeneration is not clear.
Methods :
Interaction between TLCD3B with CerSs that are expressed in the retina has been examined. Using Tlcd3b−/− mice as an inherited retinal disease animal model, we performed subretinal injection of rAAV8-CerS2, rAAV8-CerS4, and rAAV8-CerS5 at postnatal day 21 (P21) with various dosages and evaluated if compensation of different ceramide subtypes can rescue the retinal degeneration phenotype. Electroretinography (ERG) was applied to assess photoresponses of retinal cells, while histological analyses were performed on retinas to look at the preservation of retinal morphology. Mass spectrometry was performed to assess the ceramide profile change.
Results :
Results: All three rAAV8-CerSs were able to restore retinal functions as indicated by improved ERG responses, but only rAAV8-CerS5 successfully retained retinal morphology in Tlcd3b-/- mice. Additionally, mass spectrometry data suggested that rAAV8-CerS5 best recovered key ceramide species that are largely reduced in Tlcd3b-/- mice (C16:0, C18:0, and C20:0 ceramides) compared to the other 2 viruses, indicating that different ceramide species may play different roles in retinal homeostasis.
Conclusions :
Conclusions: Our results indicate that CerSs and Tlcd3b play partially redundant role. In addition, our data suggest that rather than acting as an integral entity, different ceramide species have different impacts on retinal cells and the maintenance of the overall ceramide profile is critical. Consequently, ceramide is a good target for molecular therapy development for patients with retinal pathologies and TLCD3B mutations.
This abstract was presented at the 2023 ARVO Annual Meeting, held in New Orleans, LA, April 23-27, 2023.