Long-term reversal of hypercholesterolemia in low density lipoprotein receptor (LDLR)-deficient mice by adenovirus-mediated LDLR gene transfer combined with CD154 blockade

Restoration of Physiologically Responsive Low-Density Lipoprotein Receptor-Mediated Endocytosis in Genetically Deficient Induced Pluripotent Stem Cells

Acquiring sufficient amounts of high-quality cells remains an impediment to cell-based therapies. Induced pluripotent stem cells (iPSC) may be an unparalleled source, but autologous iPSC likely retain deficiencies requiring correction. We present a strategy for restoring physiological function in genetically deficient iPSC utilizing the low-density lipoprotein receptor (LDLR) deficiency Familial Hypercholesterolemia (FH) as our model. FH fibroblasts were reprogrammed into iPSC using synthetic modified mRNA. FH-iPSC exhibited pluripotency and differentiated toward a hepatic lineage. To restore LDLR endocytosis, FH-iPSC were transfected with a 31 kb plasmid (pEHZ-LDLR-LDLR) containing a wild-type LDLR (FH-iPSC-LDLR) controlled by 10 kb of upstream genomic DNA as well as Epstein-Barr sequences (EBNA1 and oriP) for episomal retention and replication. After six months of selective culture, pEHZ-LDLR-LDLR was recovered from FH-iPSC-LDLR and transfected into Ldlr-deficient CHO-a7 cells, which then exhibited feedback-controlled LDLR-mediated endocytosis. To quantify endocytosis, FH-iPSC ± LDLR were differentiated into mesenchymal cells (MC), pretreated with excess free sterols, Lovastatin, or ethanol (control), and exposed to DiI-LDL. FH-MC-LDLR demonstrated a physiological response, with virtually no DiI-LDL internalization with excess sterols and an ~2-fold increase in DiI-LDL internalization by Lovastatin compared to FH-MC. These findings demonstrate the feasibility of functionalizing genetically deficient iPSC using episomal plasmids to deliver physiologically responsive transgenes.

Cellular unfolded protein response against viruses used in gene therapy

Viruses are excellent vehicles for gene therapy due to their natural ability to infect and deliver the cargo to specific tissues with high efficiency. Although such vectors are usually "gutted" and are replication defective, they are subjected to clearance by the host cells by immune recognition and destruction. Unfolded protein response (UPR) is a naturally evolved cyto-protective signaling pathway which is triggered due to endoplasmic reticulum (ER) stress caused by accumulation of unfolded/misfolded proteins in its lumen. The UPR signaling consists of three signaling pathways, namely PKR-like ER kinase, activating transcription factor 6, and inositol-requiring protein-1. Once activated, UPR triggers the production of ER molecular chaperones and stress response proteins to help reduce the protein load within the ER. This occurs by degradation of the misfolded proteins and ensues in the arrest of protein translation machinery. If the burden of protein load in ER is beyond its processing capacity, UPR can activate pro-apoptotic pathways or autophagy leading to cell death. Viruses are naturally evolved in hijacking the host cellular translation machinery to generate a large amount of proteins. This phenomenon disrupts ER homeostasis and leads to ER stress. Alternatively, in the case of gutted vectors used in gene therapy, the excess load of recombinant vectors administered and encountered by the cell can trigger UPR. Thus, in the context of gene therapy, UPR becomes a major roadblock that can potentially trigger inflammatory responses against the vectors and reduce the efficiency of gene transfer.

Modulation of β-catenin signaling by the inhibitors of MAP kinase, tyrosine kinase, and PI3-kinase pathways

Aberrant activation of β-catenin signaling plays an important role in human tumorigenesis. However, molecular mechanisms behind the β-catenin signaling deregulation are mostly unknown because genetic alterations in this pathway only account for a small fraction of tumors. Here, we investigator if other major pathways can regulate β-catenin signaling activity. By employing a panel of chemical activators and/or inhibitors of several cellular signaling pathways, we assess these modulators' effects on luciferase reporter driven by β-catenin/TCF4-responsive elements. We find that lithium-stimulated β-catenin activity is synergistically enhanced by protein kinase C activator PMA. However, β-catenin-regulated transcriptional (CRT) activity is significantly inhibited by casein kinase II inhibitor DRB, MEK inhibitor PD98059, G-proteins and their receptor uncoupling agent suramin, protein tyrosine kinase inhibitor genistein, and PI-3 kinase inhibitor wortmannin, suggesting that these cellular pathways may participate in regulating β-catenin signaling. Interestingly, the Ca⁺⁺/calmodulin kinase II inhibitor HDBA is shown to activate β-catenin activity at low doses. Furthermore, Wnt3A-stimulated and constitutively activated CRT activities, as well as the intracellular accumulation of β-catenin protein in human colon cancer cells, are effectively suppressed by PD98059, genistein, and wortmannin. We further demonstrate that EGF can activate TCF4/β-catenin activity and induce the tyrosine phosphorylation of β-catenin protein. Thus, our results should provide important insights into the molecular mechanisms underlying Wnt/β-catenin activation. This knowledge should facilitate our efforts to develop efficacious and novel therapeutics by targeting these pathways.

LDLR-Gene therapy for familial hypercholesterolaemia: problems, progress, and perspectives

Coronary artery diseases (CAD) inflict a heavy economical and social burden on most populations and contribute significantly to their morbidity and mortality rates. Low-density lipoprotein receptor (LDLR) associated familial hypercholesterolemia (FH) is the most frequent Mendelian disorder and is a major risk factor for the development of CAD. To date there is no cure for FH. The primary goal of clinical management is to control hypercholesterolaemia in order to decrease the risk of atherosclerosis and to prevent CAD. Permanent phenotypic correction with single administration of a gene therapeutic vector is a goal still needing to be achieved. The first ex vivo clinical trial of gene therapy in FH was conducted nearly 18 years ago. Patients who had inherited LDLR gene mutations were subjected to an aggressive surgical intervention involving partial hepatectomy to obtain the patient's own hepatocytes for ex vivo gene transfer with a replication deficient LDLR-retroviral vector. After successful re-infusion of transduced cells through a catheter placed in the inferior mesenteric vein at the time of liver resection, only low-level expression of the transferred LDLR gene was observed in the five patients enrolled in the trial. In contrast, full reversal of hypercholesterolaemia was later demonstrated in in vivo preclinical studies using LDLR-adenovirus mediated gene transfer. However, the high efficiency of cell division independent gene transfer by adenovirus vectors is limited by their short-term persistence due to episomal maintenance and the cytotoxicity of these highly immunogenic viruses. Novel long-term persisting vectors derived from adeno-associated viruses and lentiviruses, are now available and investigations are underway to determine their safety and efficiency in preparation for clinical application for a variety of diseases. Several novel non-viral based therapies have also been developed recently to lower LDL-C serum levels in FH patients. This article reviews the progress made in the 18 years since the first clinical trial for gene therapy of FH, with emphasis on the development, design, performance and limitations of viral based gene transfer vectors used in studies to ameliorate the effects of LDLR deficiency.

Injection of recombinant human type VII collagen corrects the disease phenotype in a murine model of dystrophic epidermolysis bullosa

Patients with recessive dystrophic epidermolysis bullosa (RDEB) have incurable skin fragility, blistering, and scarring due to mutations in the gene that encodes for type VII collagen (C7) that mediates dermal-epidermal adherence in human skin. We showed previously that intradermal injection of recombinant C7 into transplanted human DEB skin equivalents stably restored C7 expression at the basement membrane zone (BMZ) and reversed the RDEB disease features. In this study, we evaluated the feasibility of protein therapy in a C7 null mouse (Col7a1(-/-)) which recapitulates the features of human RDEB. We intradermally injected purified human C7 into DEB mice and found that the injected human C7 stably incorporated into the mouse BMZ, formed anchoring fibrils, and corrected the DEB murine phenotype, as demonstrated by decreased skin fragility, reduced new blister formation, and markedly prolonged survival. After 4 weeks, treated DEB mice developed circulating anti-human C7 antibodies. Most surprisingly, these anti-C7 antibodies neither bound directly to the mouse's BMZ nor prevented the incorporation of newly injected human C7 into the BMZ. Anti-C7 antibody production was prevented by treating the mice with an anti-CD40L monoclonal antibody, MR1. We conclude that protein therapy may be feasible for the treatment of human patients with RDEB.

Lipid extract of Nostoc commune var. sphaeroides Kutzing, a blue-green alga, inhibits the activation of sterol regulatory element binding proteins in HepG2 cells

Nostoc commune var. sphaeroides Kützing (N. commune), a blue-green alga, has been used as both a food ingredient and in medicine for centuries. To determine the effect of N. commune on cholesterol metabolism, N. commune lipid extract was incubated at increasing concentrations (25-100 mg/L) with HepG2 cells, a human hepatoma cell line. The addition of N. commune lipid extract markedly reduced mRNA abundance of 3-hydroxy-3-methylglutaryl-CoA reductase (HMGR) and LDL receptor (LDLR) (P < 0.05), with a concomitant decrease in their protein expression (P < 0.001). Reduced HMGR activity by 90% with N. commune lipid extract confirmed the inhibitory role of N. commune in cholesterol synthesis (P < 0.006). To elucidate a molecular mechanism underlying the repression of HMGR and LDLR by N. commune lipid extract, expression of sterol regulatory element binding protein 2 (SREBP-2) was assessed. Whereas mRNA for SREBP-2 remained unchanged, SREBP-2 mature protein was reduced by N. commune (P < 0.009). In addition, N. commune lipid extract also decreased SREBP-1 mature protein by approximately 30% (P < 0.002) and reduced the expression of SREBP-1-responsive genes such as fatty acid synthase and stearoyl CoA desaturase 1 (SCD-1) (P < 0.05). Therefore, our results demonstrate that N. commune lipid extract inhibits the maturation process of both SREBP-1 and -2, resulting in a decrease in expression of genes involved in cholesterol and fatty acid metabolism.

Immune response and effect of adenovirus-mediated human BMP-2 gene transfer on the repair of segmental tibial bone defects in goats

BACKGROUND

Tissue-engineered bone may be used for filling bone defects. There are, however, no reports on this technique used in large animals.

METHODS

We evaluated the effectiveness of, and immune response in repairing diaphyseal bone defects by gene transfer using bone morphogenetic proteins (BMPs). We used adenovirus-mediated human BMP-2 (Adv-hBMP-2) gene-transduced bone marrow stromal cells (BMSCs) to repair 2.1-cm segmental tibial bone defects in goats (group I, n = 7). An Adv-ssgal-transduced BMSC group (group II, n = 5), a non-transduced BMSC group (group III, n = 5), and an untreated group (group IV, n = 2) were used as controls. Self-secreted extracellular matrix was used as cellular carrier.

RESULTS

Radiographic and histomorphometric examination demonstrated more callus in the bone defects of group I compared to other groups. Week 24 after implantation, the defect healing rates of groups I, II, III, and IV were 6/7, 1/5, 2/5, and 0/2, respectively. The maximum compressive strength of new tissue in the bone defects of group I was higher than those of groups II and III. Temporary cellular and persistent humoral immune responses against adenovirus were detected after hBMP-2 gene transfer.

INTERPRETATION

We found that Adv-hBMP-2 genetransduced BMSCs had superior osteoinductivity in the repair of tibial bone defects in goats, but it could cause temporary cellular and persistent humoral immune responses against adenovirus.

The ras-binding domain of ral GDS-like protein-2 as a ras inhibitor in smooth muscle cells

This study was undertaken to determine whether the response of smooth muscle cells to mitogens can be inhibited by inactivating ras with the ral GDS like protein-2 ras-binding domain (RGL2-RBD). RGL2 is a member of the ral GDS family of proteins that contains a carboxy terminal ras-binding domain which binds the GTP ligated form of ras and rap and a CDC25 homology domain with the structural features of a guanine nucleotide exchange factor. The effect of ras signaling on the smooth muscle cell growth factor response was studied using rat aortic A10 smooth muscle cells transfected with a plasmid that encoded the RGL2-RBD. RGL2-RBD transfection resulted in a 12-fold reduction in the number of clonal colonies that were obtained after selection, and dramatically slowed cell cycle progression. RGBL2-RBD reduced DNA synthesis and inhibited platelet derived growth factor (PDGF)-mediated activation of the MAPK pathway. These findings indicated that interfering with ras signaling inhibits smooth muscle cell proliferation and raise the possibility that ras signaling inhibition might be used therapeutically to control smooth muscle proliferation after vascular injury.

Suppression of the immune response against exogenous desmoglein 3 in desmoglein 3 knockout mice: an implication for gene therapy

Gene therapies for recessive genetic diseases may provoke unwanted immune responses against the introduced gene product because patients, especially those with null mutation of a certain protein, have no tolerance for the protein of interest. This study used desmoglein 3 knockout (Dsg3-/-) mice as a disease model for a genetic defect in DSG3, to investigate whether nonviral gene therapy induces an immune response against Dsg3 and whether the reaction against Dsg3 can be prevented. When mouse Dsg3 cDNA was injected in the skin of Dsg3-/- mice, 50% of treated Dsg3-/- mice developed anti-Dsg3 IgG, which can bind native Dsg3 in vivo. To prevent this response, we used an anti-CD40L monoclonal antibody, MR1, which blocks the costimulatory interaction between CD40 and CD40L. To evaluate the effect of MR1, we grafted Dsg3+/+skin on Dsg3-/- mice, to mimic stable gene transfer of Dsg3. After skin grafting, all the recipient Dsg3-/- mice were treated with either MR1 (n=8) or control hamster IgG (n=8). All of the control IgG-treated mice developed circulating anti-Dsg3 IgG about 2 wk after grafting, and IgG deposition was observed on the surfaces of keratinocytes in the grafted Dsg3+/+skin. Such anti-Dsg3 IgG production was significantly prevented, however, when the recipient mice were treated with MR1. These findings suggested that gene therapies for recessive diseases may provoke an immune response against the transgene product, and that the CD40-CD40L interaction might be a reasonable target for effective prevention of such undesirable immune responses, leading, in turn, to a successful gene therapy.

Induction of cytokine tolerance in rodent hepatocytes by chylomicron-bound LPS is low-density lipoprotein receptor dependent

We examined the role of lipoprotein receptors in mediating chylomicron-bound lipopolysaccharide (CM-LPS)-induced cytokine tolerance in rodent hepatocytes. We found that 2 h of pretreatment with CM-LPS (5 mg TG/mL) was sufficient to induce cytokine tolerance, as measured by decreased nitric oxide (NO) production by hepatocytes (20% of the Control group, P < 0.03). Tolerance was evident as early as 2 h after pretreatment and disappeared after 40 h. Furthermore, we evaluated the roles of the low-density lipoprotein (LDL) receptor (LDLR) and LDL receptor-related protein (LRP) in the induction of cytokine tolerance in hepatocytes. Biochemical inhibition of the receptors or use of hepatocytes from LDLR-deficient mice revealed that functional LDLR was necessary for the induction of tolerance. However, by increasing the pretreatment time, the LRP compensated for the absence of the LDLR in induction of cytokine tolerance. In conclusion, CM-LPS-mediated induction of cytokine tolerance to proinflammatory cytokines is a time- and dose-dependent process that requires functional lipoprotein receptors. These findings underscore an interrelationship between TG-rich lipoprotein metabolism and innate immunity.

Transient blocking of both B7.1 (CD80) and B7.2 (CD86) in addition to CD40-CD40L interaction fully abrogates the immune response following systemic injection of adenovirus vector

Blockade of the CD40-CD40L and CD80/CD86-CD28 costimulatory pathways represents a strategy to inhibit the immune response against Ad vectors designed for gene therapy applications. Since most previous studies have used a CTLA4-Ig fusion molecule binding to both CD80 and CD86, the respective roles of these B7 molecules remained undefined. We have studied the effect of blocking monoclonal Abs (mAbs) directed against the costimulatory molecules CD40L, CD80 and CD86, alone or in different combinations, on the humoral and cellular immune responses against Ad. Groups of mice were transiently treated with each combination of blocking mAbs upon systemic injection of a first Ad vector. Combinations of anti-CD80 + anti-CD86 or anti-CD40L + anti-CD86 mAbs resulted in strong inhibition of the immune response against Ad. Using either of these mAb pairs, a second vector could be administered 1 month after the first injection but with lower efficiency than in naive animals. Thus, CD86 stands as the pivotal B7 molecule involved in the development of the immune response against Ad. However, only the blockade of both CD80 and CD86 in addition to CD40L fully inhibited the humoral and cellular responses against the Ad vector, such that readministration after 1 month was as efficient as in naive animals. At the time of readministration, treated animals had regained their ability to mount a normal immune response to the second Ad vector, showing that tolerance was not induced.

In vivo treatment of hemophilia A and mucopolysaccharidosis type VII using nonprimate lentiviral vectors

Gene therapy holds great promise for the treatment of a variety of inherited diseases, including hemophilia A and mucopolysaccharidosis type VII (MPS VII). In both these disorders, subnormal levels of replacement protein have therapeutic effects. Thus we hypothesized that transduction of a small proportion of cells by feline immunodeficiency virus (FIV)-based lentiviral vectors might provide sufficient levels of transgene expression for phenotypic correction. We intravenously injected replication-deficient FIV-based vectors encoding either human factor VIII or human beta-glucuronidase into factor VIII-deficient or beta-glucuronidase-deficient mice, respectively. This route of delivery targeted multiple organs, with the liver as the primary transduction site. In the hemophilia A mice, factor VIII expression persisted for the duration of the experiments (approximately 5 months), and recipient mice survived an otherwise lethal bleeding episode (tail-clipping). In mucopolysaccharidosis type VII mice, substantial beta-glucuronidase activity was detected in several tissues and corresponded with marked reduction of lysosomal storage in liver and spleen. These findings indicate that gene transfer with FIV-based lentiviral vectors can permanently introduce transgenes into a sufficient number of hepatocytes for long-term therapeutic effect and suggest potential clinical value of FIV-based lentiviral vectors for treatment of hemophilia A and MPS VII.

Vascular cell adhesion molecule-1 augments adenovirus-mediated gene transfer

We have reported that adenovirus-mediated gene transfer is augmented in the endothelium of atherosclerotic blood vessels. We observed that vascular cell adhesion molecule-1 (VCAM-1) shares some homology with the coxsackievirus and adenovirus receptor. Because VCAM-1 is upregulated on atherosclerotic endothelial cells, we hypothesized that VCAM-1 may act as an auxiliary receptor to augment adenovirus-mediated gene transfer. To test this hypothesis, stable NIH 3T3 cell lines that constitutively express VCAM-1 on the cell surface were generated. Recombinant adenovirus 5 (Ad5), which contains the reporter ss-galactosidase gene, was used to compare Ad5 infection in VCAM-1(+) and parental NIH 3T3 cells. Total ss-galactosidase activity and the number of transgene-positive cells were 6- to 10-fold and 5-fold higher, respectively, in VCAM-1(+) than in VCAM-1(-) cells. Ad5 binding to VCAM-1(+) cells was increased by 3-fold over VCAM-1(-) cells. Soluble VCAM-1 protein, present during infection or viral binding, reduced ss-galactosidase activity in VCAM-1(+) cells in a dose-dependent manner. Taken together, we conclude that VCAM-1 can mediate adenovirus binding and infection. This may explain, in part, the previous finding that adenovirus-mediated gene transfer is augmented in atherosclerotic arteries.

Gene therapy for lipid disorders

Lipid disorders are associated with atherosclerotic vascular disease, and therapy is associated with a substantial reduction in cardiovascular events. Current approaches to the treatment of lipid disorders are ineffective in a substantial number of patients. New therapies for refractory hypercholesterolemia, severe hypertriglyceridemia, and low levels of high-density lipoprotein cholesterol are needed: somatic gene therapy is one viable approach. The molecular etiology and pathophysiology of most of the candidate diseases are well understood. Animal models exist for the diseases and in many cases preclinical proof-of-principle studies have already been performed. There has been progress in the development of vectors that provide long-term gene expression. New clinical gene therapy trials for lipid disorders are likely to be initiated within the next few years.