XIAP Therapy Increases Survival of Transplanted Rod Precursors in a Degenerating Host Retina
ABSTRACT To assess the survival of rod precursor cells transplanted into the Rd9 mouse, a model of X-linked retinal degeneration, and the effect of antiapoptotic therapy with X-linked inhibitor of apoptosis (XIAP) on preventing cell loss.
Dissociated retinal cells from P4 Nrlp-GFP mice were transplanted into the subretinal space of 2-, 5-, and 8-month-old Rd9 mice. Histology, immunohistochemistry, and quantification of integrated cells were performed every month for up to 3 months after transplantation. XIAP delivery to donor cells was accomplished by transfection with adenoassociated virus (AAV-XIAP). Intraretinal activation of immune modulators was assessed using a quantitative real-time polymerase chain reaction-based immune response array.
GFP-positive rod precursors were able to integrate into the outer nuclear layer (ONL) of the Rd9 retina. Transplanted cells underwent morphologic differentiation with the formation of inner and outer segments and synaptic projections to bipolar cells. Integration of donor cells into the ONL increased as a function of host age at the time of transplantation. The number of integrated cells was maximal at 1 month after transplantation and then decreased with time. Survival of integrated cells was significantly increased when donor cells were pretreated with AAV-XIAP. We did not detect any donor cell-specific activation of inflammation within the host retina.
Survival of integrated cells decreases with time after transplantation but can be significantly increased with XIAP antiapoptotic therapy. Preventing programmed cell death through XIAP therapy may be an important component of future therapeutic retinal cell transplantation strategies.
Full-textDOI: · Available from: Kecia L Feathers, May 29, 2015
Human Gene Therapy 08/2014; 25(8):671-678. DOI:10.1089/hum.2014.2530 · 3.62 Impact Factor
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ABSTRACT: Vertebrate species possess two retinal guanylate cyclases (retGC1 and retGC2) and at least two guanylate cyclase activating proteins (GCAPs), GCAP1 and GCAP2. GCAPs function as Ca(2+) sensors that regulate the activity of guanylate cyclases. Together, these proteins regulate cGMP and Ca(2+) levels within the outer segments of rod and cone photoreceptors. Mutations in GUCY2D, the gene that encodes retGC1, are a leading cause of the most severe form of early onset retinal dystrophy, Leber congenital amaurosis (LCA1). These mutations, which reduce or abolish the ability of retGC1 to replenish cGMP in photoreceptors, are thought to lead to the biochemical equivalent of chronic light exposure in these cells. In spite of this, the majority of LCA1 patients retain normal photoreceptor laminar architecture aside from foveal cone outer segment abnormalities, suggesting they may be good candidates for gene replacement therapy. Work began in the 1980s to characterize multiple animal models of retGC1 deficiency. 34 years later, all models have been used in proof of concept gene replacement studies toward the goal of developing a therapy to treat GUCY2D-LCA1. Here we use the results of these studies as well as those of recent clinical studies to address specific questions relating to clinical application of a gene therapy for treatment of LCA1.Frontiers in Molecular Neuroscience 05/2014; 7:43. DOI:10.3389/fnmol.2014.00043
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ABSTRACT: Leber congenital amaurosis (LCA) is a clinically and genetically heterogeneous group of diseases that account for the most severe form of early-onset retinal dystrophy. Mutations in retinal guanylate cyclase-1 (GUCY2D) are associated with LCA1, a prevalent form. GUCY2D encodes guanylate cyclase-1 (GC1), a protein expressed in rod and cone photoreceptors that regulates cGMP and Ca(2+) levels within these cells. LCA1 patients present with severely impaired vision, reduced, or ablated electroretinogram and nystagmus. Despite a high degree of visual disturbance, LCA1 patients retain normal photoreceptor laminar architecture, except for foveal cone outer segment abnormalities and, in some patients, foveal cone loss. This article will summarize clinical characterization of patients and proof of concept gene replacement studies in several animal models of GC1 deficiency, both of which have laid the groundwork for clinical application of a gene therapy for treatment of LCA1.Cold Spring Harbor Perspectives in Medicine 09/2014; 5(1). DOI:10.1101/cshperspect.a017350 · 7.56 Impact Factor