Xu P

Enhanced transduction and improved photoreceptor survival of retinal degeneration by the combinatorial use of rAAV2 with a lower dose of adenovirus

Recombinant adeno-associated virus (rAAV) is widely used in retinal gene therapy. Enhanced rAAV transduction may be important for better therapeutic effects in some retinal gene therapies. In this study, we examined the effects of adenovirus 5 (Ad5) on retina transduction mediated by rAAV2. Our results provide the first evidence that low levels of either replication-incompetent or conditional replication-competent Ad5 significantly enhance and accelerate transgene expression in human and rat retinal cells. This effect occurs principally at the transcriptional level, rather than through enhanced viral entry or DNA replication. In in vivo analyses with the SD rat, the Balb/c mouse, and the RCS rat, strong enhancement and acceleration of transgene expression, as well as therapeutic effects, were confirmed. Low levels of Ad5 may enhance the utility of rAAV2-mediated transduction strategies in future clinical investigations.

Enhancement of rAAV2-Mediated Transgene Expression in Retina Cells In Vitro and In Vivo by Coadministration of Low-Dose Chemotherapeutic Drugs

PURPOSE Recombinant adeno-associated viral vector serotype 2 (rAAV2) has been used with success to deliver retina-targeted gene therapeutics in retinal degeneration. However, one of the major limitations of this approach is the vectors low transduction efficiency. This study is designed to increase AAV2 transduction efficiency in vitro and in vivo. METHODS Green fluorescence protein (GFP) or luciferase reporter gene-carried rAAV2 vectors were applied to cultured human RPE cells (ARPE-19) or animal eyes with or without chemotherapeutic agents. GFP transduction efficiency was evaluated by image, flow cytometry analysis, and Western blot. The ciliary neurotrophic factor (rAAV2-CNTF)-carried AAV2 vector was coinjected to subretinal space with or without chemotherapeutic agent. The therapeutic efficacy was evaluated by counting numbers of remaining photoreceptors in retina sections of treated or untreated eyes. RESULTS Coadministration of 0.1 μg/mL doxorubicin (DXR), 0.14 μg/mL cytarabine (Ara-C), 1 μg/mL etoposide (VP-16), or 20 μg/mL cisplatin (DDP) significantly increased rAAV2-mediated GFP and/or luciferase expression in cultured hRPE cells without any detectable toxicity. Pretreatment with DXR for 24 h prior to infection was most effective in enhancing rAAV2 transgene expression in hRPE cells. In addition, subretinal coinjection of rAAV2-CMV-ciliary neurotrophic factor (rAAV2-CNTF) and DXR into the eyes of rats with inherited retinal degeneration resulted in an approximately 2-fold increase in photoreceptor layer thickness and cellular density of the outer nuclear layer (ONL) compared to rAAV2-CNTF alone, reflecting a pronounced protection effect mediated by the enhanced expression of CNTF. CONCLUSIONS The method described here to improve rAAV2-based gene delivery is simple and feasible without any detectable toxicity. This strategy might be therapeutically exploited in the gene therapy of degenerative retinal diseases.

Enhanced Pancreatic Cancer Gene Therapy by Combination of Adenoviral Vector Expressing c-erb-B2 (Her-2/neu)-Targeted Immunotoxin with a Replication-Competent Adenovirus or Etoposide

Pancreatic cancer is the fourth leading cause of cancer-related death in the United States, and even under optimal therapy these patients face a poor prognosis. Here we report a novel gene therapy-based strategy to battle this disease. We show that the majority of pancreatic tumors overexpress c-erb-B2, which therefore might serve as a target for novel therapies. On the basis of these findings, we developed an adenoviral vector [Ad-e23(scFv)-PE40] encoding a c-erb-B2 (Her-2/neu)-targeted immunotoxin. To improve viral gene delivery we coinfected the therapeutic adenovirus with a replication-competent adenovirus (RCAd) at low doses that enhanced the transduction efficiency of the former virus. In addition, we show that target gene expression can be enhanced by adding etoposide (VP16) at nontherapeutic doses. To investigate the therapeutic efficacy of our approach we established a mouse model for advanced pancreatic cancer disease by intraperitoneal injection of pancreatic cancer cell lines, resulting in multifocal peritoneal xenograft tumors. Administration of Ad-e23(scFv)-PE40 in combination with RCAd and VP16 significantly inhibited tumor growth in mice, with no apparent systemic toxicity. In this study we show that c-erb-B2 might be an effective molecular target in the treatment of pancreatic tumors and that coadministration of a therapeutic c-erb-B2-targeted, non-replication-competent adenovirus with an RCAd and VP16 could be a powerful approach to effectively deliver therapeutic genes to tumors. As demonstrated, this strategy can be employed to effectively treat pancreatic cancer in particular, but may be modified to treat other types of cancer as well.

A Novel Conditionally Replicating “Armed” Adenovirus Selectively Targeting Gastrointestinal Tumors with Aberrant wnt Signaling

Using conditionally replicating adenoviral vectors (CRAds) is a promising strategy in the treatment of solid tumors. The prospective of this study was to design a novel CRAd for the treatment of gastrointestinal cancer and show its efficacy in vitro, as well as in vivo. To determine if aberrant wnt signaling in tumor cells can be used to selectively drive viral replication, we analyzed six colorectal and hepatocellular cell lines, as well as 13 colorectal tumors and 17 gastric tumors, for β-catenin mutation status or aberrant wnt signaling, both of which were found frequently. Based on these findings, a novel CRAd (Ad5F11.wnt-E1A-hIL24) containing an E1A expression cassette driven by an artificial wnt promoter and delivering an apoptosis-inducing gene, interleukin-24 (IL24), was engineered. To enhance infection efficiency, the virus was pseudotyped by replacing adenovirus serotype 5 (Ad5) with Ad11 fiber. Ad5F11.wnt-E1A-hIL24 virus exhibited high selectivity toward cells with aberrant wnt signaling both in vitro and in mouse xenograft tumors. Transduction efficiency was significantly improved compared with that of nonpseudotyped control viruses. The proliferation of tumor cell lines, as well as tumor growth, in mouse xenografts could be profoundly inhibited by viral infection with Ad5F11.wnt-E1A-hIL24. The therapeutic effect was associated with increased apoptosis through caspase-3 activation. In addition, Ad5F11b vector exhibited a more favorable biodistribution, blood clearance, and transgene expression compared with conventional Ad5 vector after systemic or intratumoral injection in human gastrointestinal cancer xenografts. We think that our approach is a promising strategy in the treatment of gastrointestinal cancer, warranting further clinical investigation.

Quercetin Declines Apoptosis, Ameliorates Mitochondrial Function and Improves Retinal Ganglion Cell Survival and Function in In Vivo Model of Glaucoma in Rat and Retinal Ganglion Cell Culture In Vitro

Glaucoma is a progressive neuropathy characterized by the loss of retinal ganglion cells (RGCs). Strategies that delay or halt RGC loss have been recognized as potentially beneficial for rescuing vision in glaucoma patients. Quercetin (Qcn) is a natural and important dietary flavonoid compound, widely distributed in fruits and vegetables. Mounting evidence suggests that Qcn has numerous neuroprotective effects. However, whether Qcn exerts neuroprotective effects on RGC in glaucoma is poorly understood. In this study, we investigated the protective effect of Qcn against RGC damage in a rat chronic ocular hypertension (COHT) model in vivo and hypoxia-induced primary cultured RGC damage in vitro, and we further explored the underlying neuroprotective mechanisms. We found that Qcn not only improved RGC survival and function from a very early stage of COHT in vivo, it promoted the survival of hypoxia-treated primary cultured RGCs in vitro via ameliorating mitochondrial function and preventing mitochondria-mediated apoptosis. Our findings suggest that Qcn has direct protective effects on RGCs that are independent of lowering the intraocular pressure (IOP). Qcn may be a promising therapeutic agent for improving RGC survival and function in glaucomatous neurodegeneration.

High Pressure-Induced mtDNA Alterations in Retinal Ganglion Cells and Subsequent Apoptosis

Purpose: Our previous study indicated that mitochondrial DNA (mtDNA) damage and mutations are crucial to the progressive loss of retinal ganglion cells (RGCs) in a glaucomatous rat model. In this study, we examined whether high pressure could directly cause mtDNA alterations and whether the latter could lead to mitochondrial dysfunction and RGC death. Methods: Primary cultured rat RGCs were exposed to 30 mm Hg of hydrostatic pressure (HP) for 12, 24, 48, 72, 96 and 120 h. mtDNA alterations and mtDNA repair/replication enzymes OGG1, MYH and polymerase gamma (POLG) expressions were also analyzed. The RGCs were then infected with a lentiviral small hairpin RNA (shRNA) expression vector targeting POLG (POLG-shRNA), and mtDNA alterations as well as mitochondrial function, including complex I/III activities and ATP production were subsequently studied at appropriate times. Finally, RGC apoptosis and the mitochondrial-apoptosis pathway-related protein cleaved caspase-3 were detected using a Terminal deoxynucleotidyl transferase dUTP nick end-labeling (TUNEL) assay and western blotting, respectively. Results: mtDNA damage was observed as early as 48 h after the exposure of RGCs to HP. At 120 h after HP, mtDNA damage and mutations significantly increased, reaching >40% and 4.8 ± 0.3-fold, respectively, compared with the control values. Twelve hours after HP, the expressions of OGG1, MYH and POLG mRNA in the RGCs were obviously increased 5.02 ± 0.6-fold (p < 0.01), 4.3 ± 0.2-fold (p < 0.05), and 0.8 ± 0.09-fold (p < 0.05). Western blot analysis showed that the protein levels of the three enzymes decreased at 72 and 120 h after HP (p < 0.05). After interference with POLG-shRNA, the mtDNA damage and mutations were significantly increased (p < 0.01), while complex I/III activities gradually decreased (p < 0.05). Corresponding decreases in membrane potential and ATP production appeared at 5 and 6 days after POLG-shRNA transfection respectively (p < 0.05). Increases in the apoptosis of RGCs and cleaved caspase-3 protein expression were observed after mtDNA damage and mutations. Conclusions: High pressures could directly cause mtDNA alterations, leading to mitochondrial dysfunction and RGC death.

Asiatic Acid Prevents Retinal Ganglion Cell Apoptosis in a Rat Model of Glaucoma

Asiatic acid (AA), a pentacyclic triterpene derived from the tropical medicinal plant Centella asiatica, has been widely used as an antioxidant and anti-inflammatory agent. Evidence regarding the neuroprotective properties of AA is emerging. However, the protective effects of AA and its mechanism in glaucoma are poorly understood. In the current study, we investigate the neuroprotective effect and mechanism of AA on retinal ganglion cells (RGCs) in a rat model of glaucoma. Elevated intraocular pressure (IOP) was induced in adult rats by injecting microspheres into the anterior chamber. AA was intravitreally injected into glaucomatous rats. RGC densities were analyzed by evaluating surviving RGC number of the retinal flatmounts and retinal sections, and the apoptotic cell number were evaluated by analyzing retinal sections. RGC function was assessed by measuring the photopic negative response (PhNR). Retinal Bcl-2, Bax, and cleaved caspase-3 expression were determined using a Simple Western System, real-time PCR and immunofluorescence staining. AA reduced the loss of RGCs and decreased the apoptotic RGC number. AA exerted neuroprotective effects and ameliorated retinal dysfunction in impaired RGCs in a rat model of glaucoma. AA protected RGCs by upregulating the expression of the antiapoptotic protein Bcl-2 and downregulating the expression of the pro-apoptotic proteins Bax and caspase-3. This study has provided important evidence indicating that AA may be a potential therapeutic agent for glaucoma.

Comparative analysis of retinal ganglion cell damage in three glaucomatous rat models

ABSTRACT Progressive retinal ganglion cell (RGC) death is the major cause of retinal nerve fiber layer thinning and visual field defects in glaucoma. The purpose of this study was to compare RGC damage in three commonly used glaucomatous rat models. These models were generated by (i) injection of paramagnetic microbeads into the anterior chamber; (ii) cauterization of three episcleral veins of the eye (EVC); and (iii) intravitreal injection of N‐Methyl‐D‐Aspartate (NMDA). Intraocular pressure (IOP) was measured with a rebound tonometer at 6, 12, and 18h; 1, 3, and 5 days; and 1, 2, 3, 4, 6, and 8 weeks. We measured the RGC density of the three glaucomatous models in the flat‐mounted retina by immunofluorescence. Subsequently, the thicknesses of both retinal ganglion cell layer (GCL) and inner retinal layer (IRL) were analyzed by hematoxylin and eosin staining of retinal sections. The visual functional deterioration was evaluated by measurement of the photopic negative response (PhNR) of different models. The IOP averages during three weeks were 22.35±1.23mmHg (mean±SD), 20.91±1.97mmHg, and 9.67±0.42mmHg, with 50.2%, 44.00% and 66.76% RGC loss by 8 weeks, respectively, in the microbead group, EVC group and NMDA group. Decreased thickness in the GCL was observed in all three groups, while the thickness of IRL and ONL was decreased in the EVC and NMDA groups. Significant positive correlation of RGC loss rate with &Dgr;IOP integral were demonstrated in both microbead and EVC models. Moreover, we found that the PhNR amplitudes declined early by the first day in the NMDA group, 5 days later in the EVC group and by 7 days in the microbead group. Each glaucomatous rat model has its strength and weakness. Our study provides detailed data for choosing suitable animal models to advance glaucoma research. HIGHLIGHTSGlaucomatous models were established by microbead; NMDA injection and EVC.Changes of IOP; RGC count and retinal thickness were analyzed in three models.Visual function impairment measured by PhNR differed in glaucomatous models.