Hemophilia A ameliorated in mice by CRISPR-based in vivo genome editing of human Factor VIII.

Hemophilia A is a monogenic disease with a blood clotting factor VIII (FVIII) deficiency caused by mutation in the factor VIII (F8) gene. Current and emerging treatments such as FVIII protein injection and gene therapies via AAV-delivered F8 transgene in an episome are costly and nonpermanent. Here, we describe a CRISPR/Cas9-based in vivo genome editing method, combined with non-homologous end joining, enabling permanent chromosomal integration of a modified human B domain deleted-F8 (BDD-F8) at the albumin (Alb) locus in liver cells. To test the approach in mice, C57BL/6 mice received tail vein injections of two vectors, AAV8-SaCas9-gRNA, targeting Alb intron 13, and AAV8-BDD-F8. This resulted in BDD-F8 insertion at the Alb locus and FVIII protein expression in the liver of vector-, but not vehicle-, treated mice. Using this approach in hemophilic mice, BDD-F8 was expressed in liver cells as functional human FVIII, leading to increased plasma levels of FVIII and restoration of blood clotting properties in a dose-dependent manor for at least 7 months, with no detectable liver toxicity or meaningful off-target effects. Based on these findings, our BDD-F8 genome editing approach may offer an efficacious, long-term and safe treatment for patients with hemophilia A.

Modulation of excessive neuronal activity by fibroblasts: potential use in treatment of Parkinson's disease.

PURPOSE: A number of neurological disorders are marked by increased or aberrant frequency of neuronal discharge in specific parts of the brain. Administration of drugs such as antiepileptic compounds results in the depression of neuronal activity in the whole brain, with the potential for serious side-effects. In the search for additional therapies to reduce the unphysiological electrical activity of over-active brain foci, we have examined the effect of fibroblasts transplanted to areas responsible for motor dysfunction in hemi-parkinsonian rats, since bursting synchronous discharges in internal segment of globus pallidus (GPi) are thought to be partially responsible for the movement disorders of PD. Fibroblasts express gap junctions and ion channels, and so, when transplanted to brain tissue, can potentially modulate excessive electrical activity. METHODS: Neonatal cortical neurons were cultured on multi-electrode arrays, and their electrical activity was evaluated before and after fibroblast seeding. Unilateral 6-hydroxydopamine (6-OHDA) lesion was carried out in Fischer rats. Lesioned or control rats were transplanted with either syngeneic dermal fibroblasts, microfine glass beads, ibotenic acid, or physiological saline, in the entopeduncular nucleus (EP). Apomorphine-induced rotational behavior and L-dopa-induced dyskinetic movements were evaluated before transplantation (baseline) and 2, 4, 8, 12, and 24 weeks following transplantation. Following behavioral experiments, rats were perfused with 4% formaldehyde in PBS for immunohistochemical study of the brain. RESULTS: We demonstrate in vitro that the introduction of fibroblasts into a network of neurons does not interfere with overall functional measures of activity, while moderately altering the characteristics of synchronous neuronal discharge. In rats with unilateral 6-hydroxydopamine lesions of the nigro-striatal dopaminergic pathway, apomorphine-induced rotations were reduced by more than 60% following ipsilateral transplantation of fibroblasts to the EP. L-Dopa-induced dyskinesia was also significantly reduced. Transplantation of inert microspheres, or chemical lesion of the same area with ibotenic acid, did not produce beneficial effects on parkinsonian symptomatology. CONCLUSION: Fibroblast transplantation could be an alternative treatment strategy for the parkinsonian patient.

Endothelial cells are activated by angiopoeitin-1 gene transfer and produce coordinated sprouting in vitro and arteriogenesis in vivo.

RATIONAL AND OBJECTIVES: Activation of fully differentiated vascular cells using angiogenic genes can lead to phenotypic changes resulting in formation of new blood vessels. We tested whether Ang-1 gene transfer to endothelial cells (EC) activates these cells. METHODS AND RESULTS: EC and SMC were transduced using retroviral or adenoviral vectors to produce Ang-1 or vascular endothelial growth factor (VEGF). EC Tie-2 receptor was phosphorilated by autologous secretion of Ang-1. Transduced EC and SMC sprouting capacity was tested using collagen embedded spheroids assay and capacity to produce arteriogenesis was tested in a hind limb model of ischemia. EC expressing Ang-1 in the presence of SMC expressing VEGF exhibited high levels of sprouting of the two cell types. Flow and numbers of arteries were increased after transduced cells implantation in vivo. CONCLUSIONS: Autologous secretion of Ang-1 by transduced EC resulted in Tie-2 activation and in the presence of SMC expressing VEGF resulted in coordinated sprouting in vitro and increase in flow and number of arteries in vivo.

Efficient transduction and seeding of human endothelial cells onto metallic stents using bicistronic pseudo-typed retroviral vectors encoding vascular endothelial growth factor.

BACKGROUND: Stents seeded with genetically modified endothelial cells (EC) may provide an attractive therapeutic modality for treating vascular diseases by combining the mechanical properties of the metallic stent with the biologic activity of native or genetically engineered ECs. The clinical feasibility of implanting seeded stents depends on the ability to achieve adequate stent coverage within a clinically applicable time frame. We tested the hypothesis that this goal could be achieved by seeding stents with human ECs overexpressing vascular endothelial growth factor (VEGF) and by using an efficient gene transfer system. METHODS AND RESULTS: Efficiency of gene transfer to human ECs using an amphotropic retroviral vector and a gibbon ape leukemia virus (GALV) pseudo-typed retroviral vector was examined and compared. For assessment of transduction rates, LacZ-encoding vectors were used and beta-galactosidase activity was determined 48 h after gene transfer. The transduction rate of primary human ECs using the amphotropic retroviral vector encoding the LacZ gene was low (2.9+/-2% of cells). Under the same conditions, the GALV pseudo-typed vector encoding LacZ transduced 94+/-2% of cells (P<.001). To test the effect of VEGF gene transfer on stent coverage, we transduced ECs using a bicistronic GALV pseudo-typed retroviral vector encoding either GFP alone or both VEGF and GFP. Since all transduced cells expressed GFP, stent coverage by ECs could be assessed by fluorescent inverted microscopy, which demonstrated that stent coverage by ECs overexpressing VEGF was more rapid and effective than coverage by ECs overexpressing GFP. Progressively increasing quantities of VEGF protein were detected in the conditioned medium of stents seeded with endothelia cells expressing VEGF 2, 3, and 5 days after seeding. CONCLUSIONS: High-rate gene transfer to human primary ECs was observed 48 h after transduction with GALV pseudo-typed retroviral vectors, eliminating the need for the time-consuming process of cell selection. Seeding with ECs overexpressing VEGF improved stent coverage and was associated with continuing secretion of the protein. The findings provide support for the feasibility of implanting genetically engineered biologically active cellular-coated stents.