A high-titer lentiviral production system mediates efficient transduction of differentiated cells including beating cardiac myocytes

Lentivirus-mediated inhibition of Med19 suppresses growth of breast cancer cells in vitro

PURPOSE

The mediator is a large multiprotein complex vital for transcription regulation. Human Med19 is a critical subunit of the mediator complex and plays an important role in stabilizing the whole mediator. To understand the role and mechanism of Med19 in breast cancer, we carried out studies on the impacts of lentivirus-mediated inhibition of Med19 on breast cancer cells in vitro.

METHOD

The expression of Med19 in breast cancer tissue was detected using immunohistochemical analysis. The impacts of lentivirus-mediated inhibition of Med19 on breast cancer cells were detected using flow cytometric, cell proliferation, BrdU incorporation, and colony formation assays.

RESULTS

The upregulated expression of Med19 was found in breast cancer tissues. Med19 expression was significantly associated with tumor grade (p = 0.026). The expression of Med19 was strongly suppressed in human breast cancer MDA-MB-231 and MCF-7 cells infected with lentiviruses delivering small hairpin RNA (shRNA) against Med19. The inhibition of Med19 elicited augmentation of G0/G1 phase proportion and significantly attenuated the growth of MDA-MB-231 and MCF-7 cells in vitro.

CONCLUSION

Med19 plays an important role in the proliferation of human breast cancer cells, which suggested that the lentiviruses delivering shRNA against Med19 could be a promising tool for breast cancer therapy.

Effective in vivo and ex vivo gene transfer to intestinal mucosa by VSV-G-pseudotyped lentiviral vectors

Background

Gene transfer to the gastrointestinal (GI) mucosa is a therapeutic strategy which could prove particularly advantageous for treatment of various hereditary and acquired intestinal disorders, including inflammatory bowel disease (IBD), GI infections, and cancer.

Methods

We evaluated vesicular stomatitis virus glycoprotein envelope (VSV-G)-pseudotyped lentiviral vectors (LV) for efficacy of gene transfer to both murine rectosigmoid colon in vivo and human colon explants ex vivo. LV encoding beta-galactosidase (LV-β-Gal) or firefly-luciferase (LV-fLuc) reporter genes were administered by intrarectal instillation in mice, or applied topically for ex vivo transduction of human colorectal explant tissues from normal individuals. Macroscopic and histological evaluations were performed to assess any tissue damage or inflammation. Transduction efficiency and systemic biodistribution were evaluated by real-time quantitative PCR. LV-fLuc expression was evaluated by ex vivo bioluminescence imaging. LV-β-Gal expression and identity of transduced cell types were examined by histochemical and immunofluorescence staining.

Results

Imaging studies showed positive fLuc signals in murine distal colon; β-Gal-positive cells were found in both murine and human intestinal tissue. In the murine model, β-Gal-positive epithelial and lamina propria cells were found to express cytokeratin, CD45, and CD4. LV-transduced β-Gal-positive cells were also seen in human colorectal explants, consisting mainly of CD45, CD4, and CD11c-positive cells confined to the LP.

Conclusions

We have demonstrated the feasibility of LV-mediated gene transfer into colonic mucosa. We also identified differential patterns of mucosal gene transfer dependent on whether murine or human tissue was used. Within the limitations of the study, the LV did not appear to induce mucosal damage and were not distributed beyond the distal colon.

Development of a scalable process for high-yield lentiviral vector production by transient transfection of HEK293 suspension cultures

BACKGROUND

Lentiviral vectors (LV) offer several advantages over other gene delivery vectors. Their potential for the integration and long-term expression of therapeutic genes renders them an interesting tool for gene and cell therapy interventions. However, large-scale LV production remains an important challenge for the translation of LV-based therapeutic strategies to the clinic. The development of robust processes for mass production of LV is needed.

METHODS

A suspension-grown HEK293 cell line was exploited for the production of green fluorescent protein-expressing LV by transient polyethylenimine (PEI)-based transfection with LV-encoding plasmid constructs. Using third-generation packaging plasmids (Gag/Pol, Rev), a vesicular stomatitis virus G envelope and a self-inactivating transfer vector, we employed strategies to increase volumetric and specific productivity. Functional LV titers were determined using a flow cytometry-based gene transfer assay.

RESULTS

A combination of the most promising conditions (increase in cell density, medium selection, reduction of PEI-DNA complexes per cell, addition of sodium butyrate) resulted in significantly increased LV titers of more than 150-fold compared to non-optimized small-scale conditions, reaching infectious titers of approximately 10(8) transducing units/ml. These conditions are readily scalable and were validated in 3-liter scale perfusion cultures.

CONCLUSIONS

Our process produces LV in suspension cultures and is consequently easily scalable, industrially viable and generated more than 10(11) total functional LV particles in a single bioreactor run. This process will allow the production of LV by transient transfection in sufficiently large quantities for phase I clinical trials at the 10-20-liter bioreactor scale.

Perspectives — biological pacing, a clinical reality?

Bradyarrhythmias are common and may be caused by sinus node dysfunction or conduction block. Many of these conditions can be treated by the implantation of electronic cardiac pacemakers that reduce mortality and morbidity in carefully selected patient groups. Implantable electronic pacemakers are small, sophisticated and reliable but not without complication and limitation. Efforts have been made to create a de novo sinus node using gene therapy, the so-called biopacemaker. This approach has potential as permanent cure for bradyarrythmias with greater physiological responsiveness than that provided by rate-responsive electronic pacemakers. This article reviews the current approaches to the problem and gives a perspective on the challenges remaining to bring the therapy to clinical practice.

Herpesvirus-mediated delivery of a genetically encoded fluorescent Ca(2+) sensor to canine cardiomyocytes

We report the development and application of a pseudorabies virus-based system for delivery of troponeon, a fluorescent Ca²⁺ sensor to adult canine cardiomyocytes. The efficacy of transduction was assessed by calculating the ratio of fluorescently labelled and nonlabelled cells in cell culture. Interaction of the virus vector with electrophysiological properties of cardiomyocytes was evaluated by the analysis of transient outward current (I_to), kinetics of the intracellular Ca²⁺ transients, and cell shortening. Functionality of transferred troponeon was verified by FRET analysis. We demonstrated that the transfer efficiency of troponeon to cultured adult cardiac myocytes was virtually 100%. We showed that even after four days neither the amplitude nor the kinetics of the I_to current was significantly changed and no major shifts occurred in parameters of [Ca²⁺]_i transients. Furthermore, we demonstrated that infection of cardiomyocytes with the virus did not affect the morphology, viability, and physiological attributes of cells.

NHERF3 (PDZK1) contributes to basal and calcium inhibition of NHE3 activity in Caco-2BBe cells

Elevated intracellular Ca(2+) ([Ca(2+)](i)) inhibition of NHE3 is reconstituted by NHERF2, but not NHERF1, by a mechanism involving the formation of multiprotein signaling complexes. To further evaluate the specificity of the NHERF family in calcium regulation of NHE3 activity, the current study determined whether NHERF3 reconstitutes elevated [Ca(2+)](i) regulation of NHE3. In vitro, NHERF3 bound the NHE3 C terminus between amino acids 588 and 667. In vivo, NHE3 and NHERF3 associate under basal conditions as indicated by co-immunoprecipitation, confocal microscopy, and fluorescence resonance energy transfer. Treatment of PS120/NHE3/NHERF3 cells, but not PS120/NHE3 cells, with the Ca(2+) ionophore, 4-bromo-A23187 (0.5 mum): 1) inhibited NHE3 V(max) activity; 2) decreased NHE3 surface amount; 3) dissociated NHE3 and NHERF3 at the plasma membrane by confocal immunofluorescence and fluorescence resonance energy transfer. Similarly, in Caco-2BBe cells, NHERF3 and NHE3 colocalized in the BB under basal conditions but after elevation of [Ca(2+)](i) by carbachol, this overlap was abolished. NHERF3 short hairpin RNA knockdown (>50%) in Caco-2BBe cells significantly reduced basal NHE3 activity by decreasing BB NHE3 amount. Also, carbachol-mediated inhibition of NHE3 activity was abolished in Caco-2BBe cells in which NHERF3 protein expression was significantly reduced. In summary: 1) NHERF3 colocalizes and directly binds NHE3 at the plasma membrane under basal conditions; 2) NHERF3 reconstitutes [Ca(2+)](i) inhibition of NHE3 activity and dissociates from NHE3 in fibroblasts and polarized intestinal epithelial cells with elevated [Ca(2+)](i); 3) NHERF3 short hairpin RNA significantly reduced NHE3 basal activity and brush border expression in Caco-2BBe cells. These results demonstrate that NHERF3 reconstitutes calcium inhibition of NHE3 activity by anchoring NHE3 basally and releasing it with elevated Ca(2+).

Inhibition of latent transforming growth factor-beta1 activation by lentivirus-mediated short hairpin RNA targeting the CD36 gene in NR8383 cells

CD36, a cell surface receptor for thrombospondin-1 (TSP-1), is believed to interact with latent transforming growth factor-beta1 (L-TGF-beta1) thereby activating its fibrogenic bioactivity. In this study, a lentiviral vector expressing a short hairpin RNA (shRNA) targeting the rat CD36 gene (Lv-shCD36) is developed and tested. To observe the inhibitory effect of Lv-shCD36 on the activation of L-TGF-beta1, a rat alveolar macrophage cell line (NR8383), infected with either Lv-shCD36 or Lv-shCD36-NC (non-silenced control lentivirus), was treated with 0.1 microg/ml bleomycin, which is known to stimulate alveolar macrophages to release increasing amounts of TGF-beta1. The results show that Lv-shCD36 can suppress expression of CD36 mRNA and protein in bleomycin-treated NR8383 cells. By quantifying active and total TGF-beta1 in the supernatant, it was discovered that the quantity of total TGF-beta1 is not significantly different between the three groups, while the quantity and percent of active TGF-beta1 in the Lv-shCD36 group was significantly lower than in either the bleomycin-treated group or the Lv-shCD36-NC group, respectively (P < 0.05). These results suggest that Lv-shCD36 can inhibit activation of L-TGF-beta1 secreted in bleomycin-treated NR8383 cells by decreasing the expression of CD36 on the cell membrane, thereby reducing binding of CD36 to TSP-1.

Modulation of cardiomyocyte electrical properties using regulated bone morphogenetic protein-2 expression

Because cardiomyocytes lose their ability to divide after birth, any subsequent cell loss or dysfunction results in pathologic cardiac rhythm initiation or impulse conduction. Strategies to restore and control the electrophysiological activity of the heart may, therefore, greatly affect the regeneration of cardiac tissue functionality. Using lentivirus-derived particles to regulate the bone morphogenetic protein-2 (BMP-2) gene expression in a pristinamycin- or gaseous acetaldehyde-inducible manner, we demonstrated the adjustment of cardiomyocyte electrophysiological characteristics. Complementary metal oxide semiconductor-based high-density microelectrode arrays (HD-MEAs) were used to monitor the electrophysiological activity of neonatal rat cardiomyocytes (NRCs) cultured as monolayers (NRCml) or as microtissues (NRCmt). NRCmt more closely resembled heart tissue physiology than did NRCml and could be conveniently monitored using HD-MEAs because of their ability to detect low-signal events and to sub-select the region of interest, namely, areas where the microtissues were placed. Cardiomyocyte-forming microtissues, transduced using lentiviral vectors encoding BMP-2, were capable of restoring myocardial microtissue electrical activity. We also engineered NRCmt to functionally couple within a cardiomyocyte monolayer, thus showing pacemaker-like activity upon local regulation of transgenic BMP-2 expression. The controlled expression of therapeutic transgenes represents a crucial advance for clinical interventions and gene-function analysis.

Macropinocytosis in Shiga toxin 1 uptake by human intestinal epithelial cells and transcellular transcytosis

Shiga toxin 1 and 2 production is a cardinal virulence trait of enterohemorrhagic Escherichia coli infection that causes a spectrum of intestinal and systemic pathology. However, intestinal sites of enterohemorrhagic E. coli colonization during the human infection and how the Shiga toxins are taken up and cross the globotriaosylceramide (Gb3) receptor-negative intestinal epithelial cells remain largely uncharacterized. We used samples of human intestinal tissue from patients with E. coli O157:H7 infection to detect the intestinal sites of bacterial colonization and characterize the distribution of Shiga toxins. We further used a model of largely Gb3-negative T84 intestinal epithelial monolayers treated with B-subunit of Shiga toxin 1 to determine the mechanisms of non-receptor-mediated toxin uptake. We now report that E. coli O157:H7 were found at the apical surface of epithelial cells only in the ileocecal valve area and that both toxins were present in large amounts inside surface and crypt epithelial cells in all tested intestinal samples. Our in vitro data suggest that macropinocytosis mediated through Src activation significantly increases toxin endocytosis by intestinal epithelial cells and also stimulates toxin transcellular transcytosis. We conclude that Shiga toxin is taken up by human intestinal epithelial cells during E. coli O157:H7 infection regardless of the presence of bacterial colonies. Macropinocytosis might be responsible for toxin uptake by Gb3-free intestinal epithelial cells and transcytosis. These observations provide new insights into the understanding of Shiga toxin contribution to enterohemorrhagic E. coli-related intestinal and systemic diseases.

Designing heart performance by gene transfer

The birth of molecular cardiology can be traced to the development and implementation of high-fidelity genetic approaches for manipulating the heart. Recombinant viral vector-based technology offers a highly effective approach to genetically engineer cardiac muscle in vitro and in vivo. This review highlights discoveries made in cardiac muscle physiology through the use of targeted viral-mediated genetic modification. Here the history of cardiac gene transfer technology and the strengths and limitations of viral and nonviral vectors for gene delivery are reviewed. A comprehensive account is given of the application of gene transfer technology for studying key cardiac muscle targets including Ca(2+) handling, the sarcomere, the cytoskeleton, and signaling molecules and their posttranslational modifications. The primary objective of this review is to provide a thorough analysis of gene transfer studies for understanding cardiac physiology in health and disease. By comparing results obtained from gene transfer with those obtained from transgenesis and biophysical and biochemical methodologies, this review provides a global view of cardiac structure-function with an eye towards future areas of research. The data presented here serve as a basis for discovery of new therapeutic targets for remediation of acquired and inherited cardiac diseases.

An optimized lentivirus-mediated RNAi screen reveals kinase modulators of kinesin-5 inhibitor sensitivity

Abstract: Induction of RNA interference (RNAi) in human cells has enabled comprehensive functional annotation of the human genome via reverse genetic screens. Here we describe an optimized semiautomated method to produce, titrate, and screen large collections of short hairpin RNA (shRNA)-containing lentiviral vectors. We also present results from a pilot lentiviral RNAi screen for kinases whose silencing modulates sensitivity to a mitotic spindle protein kinesin-5 inhibitor (kinesin-5i). Our screen identified three distinct serine/threonine kinase 6 shRNA vectors within our library as enhancers of kinesin-5i-mediated HT29 cell growth inhibition. In contrast, three distinct shRNAs targeting cell division cycle 2/cyclin-dependent kinase 1 resulted in kinesin-5i resistance. These results demonstrate the feasibility of screening with large collections of lentiviral vectors to identify drug enhancers and suppressors.

Oxidative stress induces GLUT4 translocation by activation of PI3-K/Akt and dual AMPK kinase in cardiac myocytes

In response to metabolic stress, GLUT4, the most abundant glucose transporter, translocates from intracellular vesicles to the plasma membrane. This appears to play an important role in protecting cardiac myocytes from ischemic injury. To investigate the precise mechanisms of GLUT4 translocation in cardiomyocytes, we have established a method for quantifying the relative proportion of sarcolemmal GLUT4 to total GLUT4 in these cells. Stimulation with H2O2 resulted in a concentration-dependent increase in GLUT4 translocation, which peaked at 15 min after stimulation. The dominant-negative form (DN) of AMP-activated protein kinase (AMPK) alpha2 inhibited the H2O2-induced translocation of GLUT4. We further examined the role of two known AMPK kinases (AMPKKs), calmodulin-dependent protein kinase kinase (CaMKK)beta and LKB1. The DN of CaMKKbeta or LKB1 alone inhibited H2O2-induced GLUT4 translocation only partially compared to the inhibition produced by the DN of AMPKalpha2. However, the combination of DN-LKB1 and DN-CaMKKbeta inhibited translocation to an extent similar to with DN-AMPKalpha2. Stimulation with H2O2 also activated Akt and the inhibition of PI3-K/Akt prevented GLUT4 translocation to the same extent as with AMPK inhibition. When the DN of AMPKalpha2 was applied with DN-PI3-K, there was a complete reduction in the GLUT4 membrane level similar to that seen at the 0 time-point. These results demonstrate that AMPK and PI3-K/Akt have an additive effect on oxidative stress-mediated GLUT4 translocation.

Optimized production and concentration of lentiviral vectors containing large inserts

Generation of high titer lentiviral stocks and efficient virus concentration are central to maximize the utility of lentiviral technology. Here we evaluate published protocols for lentivirus production on a range of transfer vectors differing in size (7.5-13.2 kb). We present a modified virus production protocol robustly yielding useful titers (up to 10(7)/ml) for a range of different transfer vectors containing packaging inserts up to 7.5 kb. Moreover, we find that virus recovery after concentration by ultracentrifugation depends on the size of the packaged inserts, heavily decreasing for large packaged inserts. We describe a fast (4 h) centrifugation protocol at reduced speed allowing high virus recovery even for large and fragile lentivirus vectors. The protocols outlined in the current report should be useful for many labs interested in producing and concentrating high titer lentiviral stocks.

Permanent, lowered HLA class I expression using lentivirus vectors with shRNA constructs: Averting cytotoxicity by alloreactive T lymphocytes

Transplantation of many tissues requires histocompatibility matching of human leukocyte antigens (HLA) to prevent graft rejection, to reduce the level of immunosuppression needed to maintain graft survival, and to minimize the risk of graft-versus-host disease, particularly in the case of bone marrow transplantation. However, recent advances in fields of gene delivery and genetic regulation technologies have opened the possibility of engineering grafts that display reduced levels of HLA expression. Suppression of HLA expression could help to overcome the limitations imposed by extensive HLA polymorphisms that restrict the availability of suitable donors, necessitate the maintenance of large donor registries, and complicate the logistics of procuring and delivering matched tissues and organs to the recipient. Accordingly, we investigated whether knockdown of HLA by RNA interference (RNAi), a ubiquitous regulatory system that can efficiently and selectively inhibit the expression of specific gene products, would enable allogeneic cells to evade immune recognition. For efficient and stable delivery of short hairpin-type RNAi constructs (shRNA), we employed lentivirus-based gene transfer vectors, which provide a delivery system that can achieve integration into genomic DNA, thereby permanently modifying transduced graft cells. Our results show that lentivirus-mediated delivery of shRNA targeting pan-Class I and allele-specific HLA can achieve efficient and dose-dependent reduction in surface expression of HLA in human cells, associated with enhanced resistance to alloreactive T lymphocyte-mediated cytotoxicity, while avoiding MHC-non-restricted killing. We hypothesize that RNAi-induced silencing of HLA expression has the potential to create histocompatibility-enhanced, and, eventually, perhaps "universally" compatible cellular grafts.

Lentiviral vector-mediated gene transfer to endotherial cells compared with adenoviral and retroviral vectors

Human immunodeficiency virus (HIV, lentivirus) vector has attractive features for gene therapy, including the ability to transduce non-dividing cells and long-term transgene expression. We have already reported that lentivirus vector can transduce well-differentiated rat cardiac myocytes. Endothelial cells (EC) are an attractive target for gene therapy, both for the treatment of cardiovascular disease and for the systemic delivery of recombinant gene products directly into the circulation. There are several reports regarding application of adenovirus and retrovirus based vectors to EC. However, there have been few reports which show the effect to lentivirus-mediated gene transfer efficiency, compared with adenovirus and retrovirus. In this study, bovine aortic endothelial cells (BAECs) were infected, in vitro, with these virus vectors. Transduction efficiency (TE) of beta-Gal gene transfer in BAECs by adenovirus, lentivirus, or retrovirus at MOI10 (Multiplicity of infection) (determined on Hela cells) is 69+/-11, 33+/-8, or 22+/-6% respectively. In adenovirus and lentivirus, almost 100% of BAECs were transduced at MOI 50. However, in retrovirus, TE showed only 48+/-6% at MOI 50 and no increase at MOI 100. The percentage of beta-Gal positive cells was decreased rapidly at longer passage of cells after being transduced by adenovirus. However, lentivirus and retrovirus showed sustained higher percentage of positive cells. Furthermore, transduction by lentiviral vectors had no significant effect on viability of BAECs. Our results indicate that lentivirus showed high-level and long term gene expression in BAECs. Lentivirus can be an effective vector for the ex vivo, genetically modified EC implantation and in vivo gene therapy.

Retroviral vector production using suspension-adapted 293GPG cells in a 3L acoustic filter-based perfusion bioreactor

Recombinant retroviruses are now an established tool for gene delivery. Presently they are mainly produced using adherent cells. However, due to the restrictive nature of adherent cell culture, this mode of production is hampered by low cell-specific productivity and small production units. The large-scale production of retroviral vectors could benefit from the adaptation of retrovirus packaging cell lines to suspension culture. Here, we describe the ability of a 293 packaging cell line to produce retroviral vectors in suspension culture at high titer. Adherent 293GPG cells, producing a Moloney Murine Leukemia Virus (MoMLV) retrovirus vector pseudotyped with the vesicular stomatitis virus G (VSVG) envelope protein and expressing a TK-GFP fusion protein, were adapted to suspension culture in calcium-free DMEM. At a cell density similar to adherent cell culture, the suspension culture produced retroviral vector consistently in the range of 1 x 10(7) infectious viral particles/mL (IVP/mL), with a specific productivity threefold higher than adherent culture. Furthermore, at the same medium replacement frequency, the suspension producer cells could be cultured at higher density than their adherent counterparts, which resulted in virus titer of 3-4 x 10(7) IVP/mL at 11.0 x 10(6) cells/mL. This corresponds to a 10-fold increase in viral concentration compared to adherent cells. The capacity to up scale the retroviral vector production was also demonstrated by performing a 2 VVD perfusion culture for 9 days in a 3L Chemap bioreactor. The combination of suspension and perfusion led to a 20-fold increase in maximum virus productivity compared to the adherent culture.

Inhibition of histone deacetylation in 293GPG packaging cell line improves the production of self-inactivating MLV-derived retroviral vectors

Background

Self-inactivating retroviral vectors (SIN) are often associated with very low titers. Promoter elements embedded within SIN designs may suppress transcription of packageable retroviral RNA which in turn results in titer reduction. We tested whether this dominant-negative effect involves histone acetylation state. We designed an MLV-derived SIN vector using the cytomegalovirus immediate early enhancer-promoter (CMVIE) as an embedded internal promoter (SINCMV) and transfected the pantropic 293GPG packaging cell line.

Results

The SINCMV retroviral producer had uniformly very low titers (~10,000 infectious retroparticles per ml). Northern blot showed low levels of expression of retroviral mRNA in producer cells in particular that of packageable RNA transcript. Treatment of the producers with the histone deacetylase (HDAC) inhibitors sodium butyrate and trichostatin A reversed transcriptional suppression and resulted in an average 106.3 ± 4.6 – fold (P = 0.002) and 15.5 ± 1.3 – fold increase in titer (P = 0.008), respectively. A histone gel assay confirmed increased histone acetylation in treated producer cells.

Conclusion

These results show that SIN retrovectors incorporating strong internal promoters such as CMVIE, are susceptible to transcriptional silencing and that treatment of the producer cells with HDAC inhibitors can overcome this blockade suggesting that histone deacetylation is implicated in the mechanism of transcriptional suppression.

Leucine 135 of Tropomodulin-1 Regulates Its Association with Tropomyosin, Its Cellular Localization, and the Integrity of Sarcomeres

Tropomodulin-1 (Tmod-1) is a well defined actin-capping protein that interacts with tropomyosin (TM) at the pointed end of actin filaments. Previous studies by others have mapped its TM-binding domain to the amino terminus from amino acid 39 to 138. In this study, we have identified several amino acid residues on Tmod-1 that are important for its interaction with TM5 (a nonmuscle TM isoform). Glutathione S-transferase affinity chromatography and immunoprecipitation assays reveal that Tmod sense mutations of either amino acid 134, 135, or 136 causes various degrees of loss of function of Tmod TM-binding ability. The reduction of TM-binding ability was relatively mild (reduced approximately 20-40%) from the G136A Tmod mutant but more substantially (reduced approximately 50-100%) from the I134D, L135E, and L135V Tmod mutants. In addition, mutation at any of these three sites dramatically alters the subcellular location of Tmod-1 when introduced into mammalian cells. Further analysis of these three mutants uncovered a previously unknown nuclear trafficking function of Tmod-1, and residues 134, 135, and 136 are located within a nuclear export signal motif. As a result, mutation on either residue 134 or residue 135 not only will cause a significant reduction of the Tmod-1 ability to bind to TM5 but also lead to predominant nuclear localization of Tmod-1 by crippling its nuclear export mechanism. The failure of the Tmod mutations to fully associate with TM5 when introduced into neonatal rat cardiomyocytes was also associated with an accelerated and severe fragmentation of sarcomeric structures compared with overexpression of wild type Tmod-1. The multiple losses of function of Tmod engendered by these missense mutations are most severe with the single substitution of residue 135.

Overview of recent advances in molecular cardiology

Molecular cardiology is a new and fast-growing area of cardiovascular medicine that aims to apply molecular biology techniques for the mechanistic investigation, diagnosis, prevention and treatment of cardiovascular disease. As an emerging discipline, it has changed conceptual thinking of cardiovascular development, disease etiology and pathophysiology. Although molecular cardiology is still at a very early stage, it has opened a promising avenue for understanding and controlling cardiovascular disease. With the rapid development and application of molecular biology techniques, scientists and clinicians are closer to curing heart diseases that were thought to be incurable 20 years ago. There clearly is a need for a more thorough understanding of the molecular mechanisms of cardiovascular diseases to promote the advancement of stem cell therapy and gene therapy for heart diseases. The present paper briefly reviews the state-of-the-art techniques in the following areas of molecular cardiology: gene analysis in the diseased heart; transgenic techniques in cardiac research; gene transfer and gene therapy for cardiovascular disease; and stem cell therapy for cardiovascular disease.

Optimisation of a multipartite human immunodeficiency virus based vector system; control of virus infectivity and large-scale production

BACKGROUND

We have previously described a five-plasmid HIV-1 vector system that utilises a codon-optimised gagpol gene. While this system was shown to be safer than systems using proviral type helpers, the titre of virus produced was relatively low. Therefore, a process of optimising all aspects of virus production was initiated.

METHODS

A systematic approach was taken to the optimisation of virus production by transient expression using a five-plasmid packaging system. Codon-manipulation was used to reduce homology between helper and vector constructs. Ultrafiltration and ultracentrifugation were used for large-scale virus production.

RESULTS

We describe codon-optimised reading frames for Tat and Rev and the optimisation of virus production. The optimisation process resulted in an increase in virus titre of 7- to 8-fold. Several other approaches to increasing viral titre described by others proved ineffective in our system after it had been optimised. In addition, we show that by varying the ratio of the GagPol helper construct to vector, the infectivity of the virus could be controlled. The use of a novel codon-optimised HIV-1 GagPol expression construct with reduced homology to vector sequences significantly reduced transfer of gagpol sequences to transduced cells. Virus could be collected in serum-free medium without a significant loss of titre, which facilitated subsequent processing. Processing using a combination of ultrafiltration and ultracentrifugation allowed efficient and rapid processing of litre volumes of virus supernatant.

CONCLUSIONS

By taking a systematic approach to optimising all aspects of our five-plasmid lentiviral vector system we improved titre, safety, large-scale production, and demonstrated that infectivity could be specifically controlled.

Shuttle of lentiviral vectors via transplanted cells in vivo

Lentiviral vectors have turned out to be an efficient method for stable gene transfer in vitro and in vivo. Not only do fields of application include cell marking and tracing following transplantation in vivo, but also the stable delivery of biological active proteins for gene therapy. A variety of cells, however, need immediate transplantation after preparation, for example, to prevent cell death, differentiation or de-differentiation. Although these cells are usually washed several times following lentiviral transduction, there may be the risk of viral vector shuttle via transplanted cells resulting in undesired in vivo transduction of recipient cells. We investigated whether infectious lentiviral particles are transmitted via ex vivo lentivirally transduced cells. To this end, we explored potential viral shuttle via ex vivo lentivirally transduced cardiomyocytes in vitro and following transplantation into the brain and peripheral muscle. We demonstrate that, even after extensive washing, infectious viral vector particles can be detected in cell suspensions. Those lentiviral vector particles were able to transduce target cells in transwell experiments. Moreover, transmitted vector particles stably transduced resident cells of the recipient central nervous system and muscle in vivo. Our results of lentiviral vector shuttle via transduced cardiomyocytes are significant for both ex vivo gene therapy and for lentiviral cell tracing, in particular for investigation of stem cell differentiation in transplantation models and co-cultivation systems.

Intradermal injection of lentiviral vectors corrects regenerated human dystrophic epidermolysis bullosa skin tissue in vivo

Dystrophic epidermolysis bullosa (DEB) is a family of inherited mechanobullous disorders caused by mutations in the gene, COL7A1, that codes for type VII, (anchoring fibril), collagen, which is critical for epidermal-dermal adherence. Most gene therapy approaches have been ex vivo, involving cell culture and culture graft transplantation, which is logistically difficult. To develop a more simplified approach, we engineered a self-inactivating lentiviral vector expressing human type VII collagen and injected this vector intradermally into hairless, immunodeficient mice and into a human DEB composite skin equivalent grafted onto immunodeficient mice. In both situations, the vector transduced dermal cells, which in turn synthesized and exported type VII collagen into the extracellular space. Remarkably, the type VII collagen selectively adhered to and incorporated into the basement membrane zone (BMZ) between the dermis and the epidermis, where it formed anchoring fibril structures. In the case of the DEB skin equivalent, the newly expressed type VII collagen reversed the DEB phenotype characterized by poor epidermal-dermal adherence and anchoring fibril defects. A single lentiviral vector injection provided stable type VII collagen at the BMZ for at least 3 months. These data demonstrate efficient and long-term type VII collagen gene transfer in vivo using direct intradermal injection of an engineered lentiviral vector.

Optimized large-scale production of high titer lentivirus vector pseudotypes

The goal of the present study was to develop an efficient transient transfection method for large-scale production of high titer lentivirus vector stocks of eight different pseudotypes. The envelope genes used for this purpose were those from VSV-G, Mokola, Rabies, MLV-Ampho, MLV-10A1, LCMV-WE, and LCMV-Arm53b. All envelopes were cloned into phCMV, which yielded lentivirus vector titers one, two, or three orders of magnitude higher than the original plasmids for the Rabies, MLV-10A1, and MLV-Ampho envelopes, respectively. When these newly constructed envelope expression plasmids were used for packaging, treatment with sodium butyrate resulted in almost five-fold increase in titers for some of the pseudotypes, had no effect for others (VSV-G and Rabies), and negatively impacted titers for the LCMV-derived pseudotypes. Production of vectors in serum-free media yielded titers only slightly lower than those obtained in the presence of serum. The efficiency of concentrating vector supernatants by ultracentrifugation or ultrafiltration was compared, with higher recovery efficiencies for the latter method, but the highest titers for most pseudotypes were obtained by ultracentrifugation. The best conditions for each individual pseudotype yielded lentivirus vector stocks with titers above 1 x 10(9) tu/mL for most pseudotypes, and higher than 1 x 10(10) tu/mL for VSV-G.

Potential of gene therapy for myocardial ischemia

PURPOSE OF REVIEW

Gene therapy-based treatment for myocardial ischemia is envisioned to involve multiple approaches.

RECENT FINDINGS

We discuss the various approaches and viral vectors available for this emerging field of cardioprotection by gene-based therapy. The prevention of arterial occlusion by the inhibition of clot formation or even atherosclerotic disease process is one approach. Another is the treatment of ischemia with genes that limit cardiac injury due to hypoxia. The molecular pathways that lead to cell damage and death are not yet fully understood. Thus, strides in the understanding of the disease process must be made.

SUMMARY

In spite of the lack of precise knowledge, delivery of certain genes has shown promise, and the development of various gene delivery techniques to the heart has shown progress.

Cytoplasmic Nuclear Transfer of the Actin-capping Protein Tropomodulin

Tropomodulin (Tmod) is a cytoskeletal actin-capping protein that interacts with tropomyosin at the pointed end of actin filaments. E-Tmod is an isoform that expresses predominantly in cardiac cells and slow skeletal muscle fibers. We unexpectedly discovered significant levels of Tmod in nuclei and then defined peptide domains in Tmod responsible for nuclear import and export. These domains resemble, and function as, a nuclear export signal (NES) and a pattern 4 nuclear localization signal (NLS). Both motifs are conserved in other Tmod isoforms and across species. Comparisons of wild-type Tmod and Tmod carrying mutations in these peptide domains revealed that Tmod normally traffics through the nucleus. These observations logically presuppose that Tmod functions may include a nuclear role. Indeed, increasing Tmod in the nucleus severely hampered myogenic differentiation and selectively suppressed muscle-specific gene expression (endogenous p21, myosin heavy chain, myogenin, and Tmod) but did not affect endogenous glyceraldehyde-3-phosphate dehydrogenase or expression from a transfected E-GFP vector. These results suggest that, at least in myogenic cells, nuclear Tmod may be involved in the differentiation process.

Transduction of terminally differentiated neurons by avian sarcoma virus

Recent studies have demonstrated that avian sarcoma virus (ASV) can transduce cycle-arrested cells. Here, we have assessed quantitatively the transduction efficiency of an ASV vector in naturally arrested mouse hippocampal neurons. This efficiency was determined by comparing the number of transduced cells after infection of differentiated neurons versus dividing progenitor cells. The results indicate that ASV is able to transduce these differentiated neurons efficiently and that this activity is not the result of infection of residual dividing cells. The transduction efficiency of the ASV vector was found to be intermediate between the relatively high and low efficiencies obtained with human immunodeficiency virus type 1 and murine leukemia virus vectors, respectively.

Comparison of transfection conditions for a lentivirus vector produced in large volumes

A number of different transfection reagents have been used for lentiviral vector production. We directly compared transfection buffers, DNA purification methods, chemical facilitators, and DNA concentrations to optimize production. The use of N,N-bis (2-hydroxyethyl)-2-aminoethanesulfonic acid (BES), sodium butyrate, and one fourth the total amount of DNA used in standard transient transfection protocols were the best conditions for virus production. These reagents were combined into a single protocol and scaled-up to produce liter quantities of virus in a multitray tissue culture vessel.

Retroviral vectors for human gene delivery

The potential for gene therapy to cure a wide range of diseases has lead to high expectations and a great increase in research efforts in this area. At present, viral vectors are the most efficient means of delivering a corrective gene into human cells. While a number of different viral vectors are under development, retroviral vectors are currently the most common type used in clinical trials today. However, the production of retroviral vectors for gene therapy applications faces a number of challenges. Of primary concern is the low titre of vector stocks produced by packaging cells in culture and the inherent instability of retroviral vector activity. The problems facing large-scale retroviral vector production are outlined in this review and the research efforts by a number of groups who have attempted to optimise production methods are presented.

Identification and biochemical characterization of a Werner's syndrome protein complex with Ku70/80 and poly(ADP-ribose) polymerase-1

Werner's syndrome (WS) is an inherited disease characterized by genomic instability and premature aging. The WS gene encodes a protein (WRN) with helicase and exonuclease activities. We have previously reported that WRN interacts with Ku70/80 and this interaction strongly stimulates WRN exonuclease activity. To gain further insight on the function of WRN and its relationship with the Ku heterodimer, we established a cell line expressing tagged WRN(H), a WRN point mutant lacking helicase activity, and used affinity purification, immunoblot analysis and mass spectroscopy to identify WRN-associated proteins. To this end, we identified three proteins that are stably associated with WRN in nuclear extracts. Two of these proteins, Ku70 and Ku80, were identified by immunoblot analysis. The third polypeptide, which was identified by mass spectrometry analysis, is identical to poly(ADP-ribose) polymerase-1(PARP-1), a 113-kDa enzyme that functions as a sensor of DNA damage. Biochemical fractionation studies and immunoprecipitation assays and studies confirmed that endogenous WRN is associated with subpopulations of PARP-1 and Ku70/80 in the cell. Protein interaction assays with purified proteins further indicated that PARP-1 binds directly to WRN and assembles in a complex with WRN and Ku70/80. In the presence of DNA and NAD(+), PARP-1 poly(ADP-ribosyl)ates itself and Ku70/80 but not WRN, and gel-shift assays showed that poly-(ADP-ribosyl)ation of Ku70/80 decreases the DNA-binding affinity of this factor. Significantly, (ADP-ribosyl)ation of Ku70/80 reduces the ability of this factor to stimulate WRN exonuclease, suggesting that covalent modification of Ku70/80 by PARP-1 may play a role in the regulation of the exonucleolytic activity of WRN.

Normal and Gene-Corrected Dystrophic Epidermolysis Bullosa Fibroblasts Alone Can Produce Type VII Collagen at the Basement Membrane Zone

Type VII collagen is synthesized and secreted by both human keratinocytes and fibroblasts. Although both cell types can secrete type VII collagen, it is thought that keratinocytes account for type VII collagen at the dermal-epidermal junction (DEJ). In this study, we examined if type VII collagen secreted solely by dermal fibroblasts could be transported to the DEJ. We established organotypic, skin-equivalent cultures composed of keratinocytes from patients with recessive dystrophic epidermolysis bullosa (RDEB) and normal dermal fibroblasts. Immuno-labeling of skin equivalent sections with the anti-type VII collagen antibody revealed tight linear staining at the DEJ. RDEB fibroblasts, were gene-corrected to make type VII collagen and used to regenerate human skin on immune-deficient mice. The human skin generated by gene-corrected RDEB fibroblasts or normal human fibroblasts combined with RDEB keratinocytes restored type VII collagen expression at the DEJ in vivo. Further, intradermal injection of normal human or gene-corrected RDEB fibroblasts into mouse skin resulted in the stable expression of human type VII collagen at the mouse DEJ. These data demonstrate that human dermal fibroblasts alone are capable of producing type VII collagen at the DEJ, and it is possible to restore type VII collagen gene expression in RDEB skin in vivo by direct intradermal injection of fibroblasts.

Gene therapy for muscular dystrophy - a review of promising progress

This review considers the most significant progress in developing genetic therapeutic interventions for Duchenne muscular dystrophy (DMD), in order to illustrate the challenges facing gene therapy of all the muscular dystrophies (MDs). While in vivo repair of genetic mutations affecting muscle remains inefficient, the most promising interventions focus on supplementation of minimally sized transgenes encoding the abnormal muscle proteins. Intramuscular injection of recombinant viral vectors carrying therapeutic transgenes has yielded the most impressive amelioration of dystrophic muscle pathology in animal models, although achieving lasting, body-wide transgene delivery in the absence of a significant immunological reaction remains unrealised. Ex vivo correction and engraftment of muscle precursor and stem cell populations remains a potential (albeit presently less efficient) alternative to in vivo interventions. Recent advances provide encouraging evidence for the feasibility of genetic therapy of the MDs, but further evaluation of interventions in larger animal models and ultimately human trials is necessary to identify the most promising techniques for development.

Reprogramming cells for transplantation

The field of tissue engineering, involving the reprogramming of stem cells or rejuvenation of specific differentiated cells, is emerging as a promising strategy to repair the damaged myocardium. The eventual goal is to be able to take a patient's own cells, expand them ex vivo, genetically engineer them to enhance specific properties, and then reintroduce them into the patient's heart to create a replacement tissue. Our review paper describes data that supports the potential of this strategy. This clinically relevant, combined strategy of genetic and tissue engineering could be of importance in treating elderly patients with massive myocardial damage, patients whose normal myogenic or angiogenic cells have been depleted or are inadequate in their growth potential, to prevent LV deterioration and heart failure.

Characterization and detection of artificial replication-competent lentivirus of altered host range

Replication-competent lentivirus (RCL) may be generated during the production phase or subsequently after introduction of a lentiviral vector into target cells, potentially by homologous or nonhomologous recombination. Because most gene transfer of HIV-based vectors involves the use of high-titer vesicular stomatitis virus (VSV) G-pseudotyped particles, one particular concern would be the generation of an RCL of altered host range, i.e., one that has incorporated the VSV G envelope in cis configuration. We report here on the artificial generation and properties of such a virus, including its detection after biological amplification. Viral spread, beginning with a very low inoculum, takes several weeks in culture and is characterized by "autoinfection," resulting in multiple proviral copies per cell, higher levels of viral gene expression, and eventual cell death. After this initial amplification step, the RCL is easily detectable by standard p24 assay or by "marker-rescue" assay. For the latter, a 293T-based cell line that has an integrated replication-defective provirus encoding alkaline phosphatase (AP) was used and mobilization of AP-containing virus was detected by transduction of naïve cells. Replication-defective virus was not amplified nor detected, demonstrating assay specificity. These results suggest that these artificial RCLs of broad host range have slightly different biological properties compared to wild-type HIV but still spread and are readily detectable.

Cell cycle regulation to repair the infarcted myocardium

Lower vertebrates such as newt and zebrafish are able to reactivate high levels of cardiomyocyte cell cycle activity in response to experimental injury resulting in apparent regeneration. In contrast, damaged myocardium is replaced by fibrotic scar tissue in higher vertebrates. This process compromises the contractile function of the surviving myocardium, ultimately leading to heart failure. Various strategies are being pursued to augment myocyte number in the diseased hearts. One approach entails the reactivation of cell cycle in surviving cardiomyocytes. Here, we provide a summary of methods to monitor cell cycle activity, and interventions demonstrating positive cell cycle effects in cardiomyocytes as well as discuss the potential utility of cell cycle regulation to augment myocyte number in diseased hearts.

Gene therapy for the treatment of heart failure--calcium signaling

The knowledge of molecular mechanisms indicated in cardiac dysfunction has increased dramatically over the last decade and yields considerable potential for new treatment options in heart failure. Alterations in intracellular calcium signaling play a crucial role in the pathophysiology of heart failure, and in recent years, somatic gene transfer has been identified as an important tool to help understand the relative contribution of specific calcium-handling proteins in heart failure. This article reviews recent advances in gene delivery techniques aimed at global myocardial transfection and discusses molecular therapeutic targets identified within intracellular calcium signaling pathways in heart failure.

Oxidative stress and heart disease: cardiac dysfunction, nutrition, and gene therapy

Oxidative stress is defined as the imbalance between the generation of reactive oxygen species and antioxidant defense mechanisms. The cardiovascular system is a major target for reactive oxygen species. Cardiomyocytes and the vasculature of the heart can be severely damaged as a result of oxidative stress. In this paper, we discuss recent findings with respect to the role of oxidative stress in heart disease. The efficacies of treatments with vitamins and wine-derived compounds, as well as innovative gene therapeutic experiments that may potentially alleviate oxidative stress-induced disease, are also discussed.

Multiply attenuated, self-inactivating lentiviral vectors efficiently deliver and express genes for extended periods of time in adult rat cardiomyocytes in vivo

BACKGROUND

Among retroviral vectors, lentiviral vectors are unique in that they transduce genes into both dividing and nondividing cells. However, their ability to provide sustained myocardial transgene expression has not been evaluated.

METHODS AND RESULTS

Multiply attenuated, self-inactivating lentivectors based on human immunodeficiency virus-1 contained the enhanced green fluorescent protein (EGFP) gene under the transcriptional control of either the cytomegalovirus (CMV) immediate-early enhancer/promoter, the elongation factor-1alpha (EF-1alpha) promoter, or the phosphoglycerate-kinase (PGK) promoter. Lentivectors transduced adult rat cardiomyocytes in a dose-dependent manner (transduction rates, >90%; multiplicity of infection, approximately 5). The CMV promoter achieved higher EGFP expression levels than the EF-1alpha and PGK promoters. Insertion of the central polypurine tract pol sequence improved gene transfer efficiency by approximately 2-fold. In vivo gene transfer kinetics was studied by measuring the copy number of integrated lentivirus DNA and EGFP concentrations in cardiac extracts by real-time polymerase chain reaction and ELISA, respectively. With CMV promoter-containing lentivectors, vector DNA peaked at day 3, declined by approximately 4-fold at day 14, but then remained stable up to week 10. Similarly, EGFP expression peaked at day 7, decreased by approximately 7-fold at day 14, but was essentially stable thereafter. In contrast, vector DNA and EGFP expression declined rapidly with EF-1alpha promoter-containing lentivectors. Peak EGFP expression with titer-matched adenovectors was approximately 35% higher than with CMV lentivectors but was lost rapidly over time.

CONCLUSIONS

Lentivectors efficiently transduce and express genes for extended periods of time in cardiomyocytes in vivo. Lentivectors provide a useful tool for studying myocardial biology and a potential system for gene heart therapy.

'Advanced' generation lentiviruses as efficient vectors for cardiomyocyte gene transduction in vitro and in vivo

Efficient gene transduction in cardiomyocytes is a task that can be accomplished only by viral vectors. Up to now, the most commonly used vectors for this purpose have been adenoviral-derived ones. Recently, it has been demonstrated that lentiviral vectors can transduce growth-arrested cells, such as hematopoietic stem cells. Moreover, a modified form of lentiviral vector (the 'advanced' generation), containing an mRNA-stabilizer sequence and a nuclear import sequence, has been shown to significantly improve gene transduction in growth-arrested cells as compared to the third-generation vector. Therefore, we tested whether the 'advanced' generation lentivirus is capable of infecting and transducing cardiomyocytes both in vitro and in vivo, comparing efficacy in vitro against the third-generation of the same vector. Here we report that 'advanced' generation lentiviral vectors infected most (>80%) cardiomyocytes in culture, as demonstrated by immunofluorescence and FACS analyses: in contrast the percentage of cardiomyocytes infected by third-generation lentivirus was three- to four-fold lower. Moreover, 'advanced' generation lentivirus was also capable of infecting and inducing stable gene expression in adult myocardium in vivo. Thus, 'advanced' generation lentiviral vectors can be used for both in vitro and in vivo gene expression studies in the cardiomyocyte.

An efficient gene transduction system for studying gene function in primary human dermal fibroblasts and epidermal keratinocytes

One of the critical challenges for cellular genetic studies in primary human skin cells is lack of a gene delivery system that provides efficient transduction and sustained expression of the transgenes. Due to the limited time of survival in culture, the processes of drug selection and clonal expansion for establishing gene stably expressing cell lines are not a realistic option for primary skin cells. We have examined various gene transduction techniques in primary dermal fibroblasts and epidermal keratinocytes of human skin. We report here that vectors based on the human immunodeficiency virus (HIV, lentivirus) offer more than 90% gene transduction efficiency and sustained expression of transgenes in both human skin cell types. In contrast, most of the commonly used techniques have at best 30% transduction efficiency in these cells. Using two previously reported migration control genes, protein kinase Cdelta and p38alpha-MAPK, as examples, we provide evidence that the unprecedented efficiency of the lentiviral system enables a clear detection of the genes' dominant negative effects, which are otherwise greatly compromised by ordinary transfection techniques. We believe that a wide application of this gene transduction system will greatly benefit studies of gene function in human skin cells.

Restoration of type VII collagen expression and function in dystrophic epidermolysis bullosa

Dystrophic epidermolysis bullosa (DEB) is a family of inherited mechano-bullous disorders caused by mutations in the human type VII collagen gene (COL7A1). Individuals with DEB lack type VII collagen and anchoring fibrils, structures that attach epidermis and dermis. The current lack of treatment for DEB is an impetus to develop gene therapy strategies that efficiently transfer and stably express genes delivered to skin cells in vivo. In this study, we delivered and expressed full-length type VII collagen using a self-inactivating minimal lentivirus-based vector. Transduction of lentiviral vectors containing the COL7A1 transgene into recessive DEB (RDEB) keratinocytes and fibroblasts (in which type VII collagen was absent) resulted in persistent synthesis and secretion of type VII collagen. Unlike RDEB parent cells, the gene-corrected cells had normal morphology, proliferative potential, matrix attachment and motility. We used these gene-corrected cells to regenerate human skin on immune-deficient mice. Human skin regenerated by gene-corrected RDEB cells had restored expression of type VII collagen and formation of anchoring fibrils at the dermal-epidermal junction in vivo. These studies demonstrate that it is possible to restore type VII collagen gene expression in RDEB skin in vivo.

Targeted gene therapy for the treatment of cardiac dysfunction

Congestive heart failure (CHF), one of the leading cardiovascular disorders in developed countries, remains a significant therapeutic challenge. Efficacious therapies are few, and the incidence of CHF and associated death rates continue to rise. An interest in the novel therapeutic approach of gene therapy for the treatment of CHF has emerged. Essential elements of successful gene therapy include an appropriate vector for delivering and expressing the gene within the target cell, an optimal protocol for delivery of the gene, and the identification of relevant pathways and molecular targets. Interest in gene therapy for CHF has been directed towards improving cardiomyocyte function through optimization of calcium homeostasis and beta-adrenoreceptor function, and preclinical studies have shown encouraging results. This review will discuss the vectors and mechanisms of gene delivery as well as potential molecular targets for the treatment of CHF.

An important role for protein kinase C-delta in human keratinocyte migration on dermal collagen

Migration of human keratinocytes plays a critical role in the re-epithelialization of human skin wounds, the process by which the wound bed is resurfaced and closed by keratinocytes as it forms a new epidermis. While the importance of ECM components and serum factors in the regulation of keratinocytes motility is well established, the intracellular signaling mechanisms remain fragmentary. In this study, we investigated the role of protein kinase Cdelta (PKCdelta) signaling in the promotion of human keratinocyte migration by a collagen matrix and bovine pituitary extract. We found that pharmacological inhibition of the PKCdelta pathway completely blocks migration. Using a lentivirus-based vector system, which offers more than 90% gene transduction efficiency to human keratinocytes, we show that the kinase-defective mutant of PKCdelta (K376R) dramatically inhibits human keratinocyte migration. Furthermore, PKCdelta is activated in migrating human keratinocytes. These observations indicate for the first time that the PKCdelta pathway plays an important role in the control of human keratinocyte migration.

Lentiviral gene transduction of kidney

Gene transfer into kidney holds great potential as a novel therapeutic approach. We have studied the transduction of kidney in vivo after delivery of lentiviral vectors by various routes of administration. A lentiviral vector expressing the bacterial lacZ gene from the cytomegalovirus early promoter was used. The lentiviral vector was delivered into the kidneys of BALB/c mice by retrograde infusion into the ureter, by injection into the renal vein or artery, or by direct injection into the renal parenchyma. Expression of the reporter gene was achieved independently of the route of administration, although it appeared more efficient after parenchymal or ureteral administration. After parenchymal or ureteral infusion, expression of the transgene was localized to the outer medulla and corticomedullary junction. In the case of parenchymal injection, expression of the reporter gene extended to the cortex. Detection of the transgene in the renal proximal tubules was confirmed by in situ polymerase chain reaction after parenchymal or ureteral infusion. On delivery of the lentiviral vector through the renal artery or vein, expression of the reporter gene was markedly lower than was observed with parenchymal or ureteral infusion and was limited to the inner medullary collecting ducts. No apparent histological abnormality was observed after virus administration and transgene expression was stable for at least 3 months. These results provide the first evidence that lentiviral vectors can stably transduce renal cells in vivo and may be effective vehicles for gene delivery to the kidney.

In vivo gene transfer to kidney by lentiviral vector

BACKGROUND

The growing understanding of the molecular basis of renal diseases makes the development of gene therapy for kidney disorders a potential treatment alternative. Work aimed at determining the feasibility and the efficiency of gene transfer to the kidney using different viral and nonviral transduction systems is a necessary component to understanding the full potential. Lentiviral vectors have been shown to transduce stably different tissues and cell types that are refractory to other gene transfer approaches. To date, the potential of lentiviral vectors to transfer genes in kidney has not been investigated. The scope of this work was to analyze the efficiencies of in vivo transduction of kidney by a lentiviral vector.

METHODS

A pseudotyped lentiviral vector carrying the gene for the enhanced green fluorescent protein (EGFP) was delivered into one kidney of experimental mice by retrograde infusion through the ureter. The presence of the virus and the expression of the reporter protein were monitored over time.

RESULTS

Both viral DNA and EGFP expression were measurable in the kidney infused with the lentiviral vector but not in the contralateral kidney. Protein expression was detected by immunostaining, as EGFP fluorescence was masked by the high background fluorescence of the kidney. Expression of EGFP persisted for the entire two-month duration of the experiments.

CONCLUSIONS

Lentiviral vectors can effectively deliver exogenous genes to the kidney in vivo, resulting in persistent expression of the introduced gene.

Vesicular stomatitis virus G-pseudotyped lentivirus vectors mediate efficient apical transduction of polarized quiescent primary alveolar epithelial cells

We investigated the use of lentivirus vectors for gene transfer to quiescent alveolar epithelial cells. Primary rat alveolar epithelial cells (AEC) grown on plastic or as polarized monolayers on tissue culture-treated polycarbonate semipermeable supports were transduced with a replication-defective human immunodeficiency virus-based lentivirus vector pseudotyped with the vesicular stomatitis virus G (VSV-G) protein and encoding an enhanced green fluorescent protein reporter gene. Transduction efficiency, evaluated by confocal microscopy and quantified by fluorescence-activated cell sorting, was dependent on the dose of vector, ranging from 4% at a multiplicity of infection (MOI) of 0.1 to 99% at an MOI of 50 for AEC grown on plastic. At a comparable titer and MOI, transduction of these cells by a similarly pseudotyped murine leukemia virus vector was approximately 30-fold less than by the lentivirus vector. Importantly, comparison of lentivirus-mediated gene transfer from the apical or basolateral surface of confluent AEC monolayers (R(t) > 2 kOmega. cm(2); MOI = 10) revealed efficient transduction only when VSV-G-pseudotyped lentivirus was applied apically. Furthermore, treatment with EGTA to increase access to the basolateral surface did not increase transduction of apically applied virus, indicating that transduction was primarily via the apical membrane domain. In contrast, differentiated tracheal epithelial cells were transduced by apically applied lentivirus only in the presence of EGTA and at a much lower overall efficiency (approximately 15-fold) than was observed for AEC. Efficient transduction of AEC from the apical cell surface supports the feasibility of using VSV-G-pseudotyped lentivirus vectors for gene transfer to the alveolar epithelium and suggests that differences exist between upper and lower airways in the polarity of available receptors for the VSV-G protein.

Development of lentiviral vectors for antiangiogenic gene delivery

Growth and metastasis of malignant tumors requires angiogenesis. Inhibition of tumor-induced angiogenesis may represent an effective cytostatic strategy. We have constructed recombinant self-inactivating lentiviral vectors expressing angiostatin and endostatin, and have tested their antiangiogenic activities. As VSV-G-pseudotyped lentiviral vectors showed low relative transduction titers on bovine aortic and human umbilical vein endothelial cells, it was difficult to achieve significant inhibition of endothelial cell growth by lentivirus-mediated antiangiogenic gene transfer directly to endothelial cells without concomitant vector-associated cytotoxicity. However, lentivirus vectors could efficiently and stably transduce T24 human bladder cancer cells that are relatively resistant to adenovirus infection due to loss of coxsackievirus-adenovirus receptor expression. Long-term expression and secretion of angiostatin and endostatin from lentivirus-transduced T24 cells resulted in significant inhibition of cellular proliferation on coculture with endothelial cells. This report represents the first use of lentivirus-based vectors to deliver the antiangiogenic factors, angiostatin and endostatin, and suggests the potential utility of antiangiogenic gene therapy with lentiviral vectors for the treatment of cancer.

Human NKT cells mediate antitumor cytotoxicity directly by recognizing target cell CD1d with bound ligand or indirectly by producing IL-2 to activate NK cells

alpha-Galactosylceramide (alphaGalCer) stimulates NKT cells and has antitumor activity in mice. Murine NKT cells may directly kill tumor cells and induce NK cell cytotoxicity, but the mechanisms are not well defined. Newly developed human CD1d/alphaGalCer tetrameric complexes were used to obtain highly purified human alphaGalCer-reactive NKT cell lines (>99%), and the mechanisms of NKT cell cytotoxicity and activation of NK cells were investigated. Human NKT cells were cytotoxic against CD1d(-) neuroblastoma cells only when they were rendered CD1d(+) by transfection and pulsed with alphaGalCer. Four other CD1d(-) tumor cell lines of diverse origin were resistant to NKT cells, whereas Jurkat and U937 leukemia cell lines, which are constitutively CD1d(+), were killed. Killing of the latter was greatly augmented in the presence of alphaGalCer. Upon human CD1d/alphaGalCer recognition, NKT cells induced potent cytotoxicity of NK cells against CD1d(-) neuroblastoma cell lines that were not killed directly by NKT cells. NK cell activation depended upon NKT cell production of IL-2, and was enhanced by secretion of IFN-gamma. These data demonstrate that cytotoxicity of human NKT cells can be CD1d and ligand dependent, and that TCR-stimulated NKT cells produce IL-2 that is required to induce NK cell cytotoxicity. Thus, NKT cells can mediate potent antitumor activity both directly by targeting CD1d and indirectly by activating NK cells.

How to optimize in vivo gene transfer to cardiac myocytes: mechanical or pharmacological procedures?

An efficient gene delivery system is a prerequisite for myocardial gene therapy. Among the various procedures studied so far, catheter-based percutaneous gene delivery to the myocardium through the coronary vessels seems the most relevant to routine clinical practice; however, the optimal conditions remain to be determined. We selectively infused adenoviral vectors encoding luciferase (1 x 10(9) PFU) or beta-galactosidase (1 x 10(10) PFU) into coronary arteries of adult rabbits in various experimental conditions. Coronary artery occlusion for 30 sec, during and after adenovirus delivery, was required to observe luciferase activity in the target area of the circumflex artery (4.0 +/- 1.0 x 10(5) vs. 1.1 +/- 0.2 x 10(4) RLU/mg with and without coronary occlusion, respectively, p < 0.01, and 1.0 +/- 0.1 x 10(3) RLU/mg using nonselective infusion). When adenoviruses were delivered using high-pressure infusion (82 +/- 12 vs. 415 +/- 25 mmHg before and during infusion, respectively, p < 0.01), luciferase activity increased to 8.5 +/- 2.5 x 10(5) RLU/mg (p < 0.05 vs coronary occlusion alone). Coronary venous sinus occlusion with saline buffer retroinfusion starting before and during anterograde adenovirus delivery resulted in a further 4.7-fold increase in luciferase activity (4.4 +/- 0.8 x 10(6) RLU/mg, p < 0.01) with 5-25% blue-stained myocytes in the target area, compared with 0-5% with the other procedures. Histamine or VEGF-A(165) pretreatment, used to increase vascular permeability, slightly increased gene transfer efficiency (8.5 +/- 2.0 x 10(5) and 9.0 +/- 2.5 x 10(5) RLU/mg respectively, p < 0.05 vs. coronary occlusion alone). We conclude that catheter-mediated adenoviral gene transfer to cardiac myocytes through coronary vessels can be a very efficient procedure for myocardial gene therapy, particularly when the vector residence time and perfusion pressure in the vessels are increased.