Increased contact time improves adenovirus-mediated CFTR gene transfer to nasal epithelium of CF mice

Lipid Nanoparticle-Delivered Chemically Modified mRNA Restores Chloride Secretion in Cystic Fibrosis

The promise of gene therapy for the treatment of cystic fibrosis has yet to be fully clinically realized despite years of effort toward correcting the underlying genetic defect in the cystic fibrosis transmembrane conductance regulator (CFTR). mRNA therapy via nanoparticle delivery represents a powerful technology for the transfer of genetic material to cells with large, widespread populations, such as airway epithelia. We deployed a clinically relevant lipid-based nanoparticle (LNP) for packaging and delivery of large chemically modified CFTR mRNA (cmCFTR) to patient-derived bronchial epithelial cells, resulting in an increase in membrane-localized CFTR and rescue of its primary function as a chloride channel. Furthermore, nasal application of LNP-cmCFTR restored CFTR-mediated chloride secretion to conductive airway epithelia in CFTR knockout mice for at least 14 days. On day 3 post-transfection, CFTR activity peaked, recovering up to 55% of the net chloride efflux characteristic of healthy mice. This magnitude of response is superior to liposomal CFTR DNA delivery and is comparable with outcomes observed in the currently approved drug ivacaftor. LNP-cmRNA-based systems represent a powerful platform technology for correction of cystic fibrosis and other monogenic disorders.

Lentiviral transduction of the murine lung provides efficient pseudotype and developmental stage-dependent cell-specific transgene expression

Gene transfer for cystic fibrosis (CF) airway disease has been hampered by the lung's innate refractivity to pathogen infection. We hypothesized that early intervention with an integrating gene transfer vector capable of transducing the lung via the lumen may be a successful therapeutic approach. An HIV-based lentiviral vector pseudotyped with the baculovirus gp64 envelope was applied to the fetal, neonatal or adult airways. Fetal intra-amniotic administration resulted in transduction of approximately 14% of airway epithelial cells, including both ciliated and non-ciliated epithelia of the upper, mid and lower airways; there was negligible alveolar or nasal transduction. Following neonatal intra-nasal administration we observed significant transduction of the airway epithelium (approximately 11%), although mainly in the distal lung, and substantial alveolar transduction. This expression was still detectable at 1 year after application. In the adult, the majority of transduction was restricted to the alveoli. In contrast, vesicular stomatitis virus glycoprotein pseudotyped virus transduced only alveoli after adult and neonatal application and no transduction was observed after fetal administration. Repeat administration did not increase transduction levels of the conducting airway epithelia. These data demonstrate that application at early developmental stages in conjunction with an appropriately pseudotyped virus provides efficient, high-level transgene expression in the murine lung. This may provide a modality for treatment for lung disease in CF.

Expression of CFTR from a ciliated cell-specific promoter is ineffective at correcting nasal potential difference in CF mice

Successful gene therapy will require that the therapeutic gene be expressed at a sufficient level in the correct cell type(s). To improve the specificity of gene transfer for cystic fibrosis (CF) and other airway diseases, we have begun to develop cell-type specific promoters to target the expression of transgenes to specific airway cell types. Using a FOXJ1 promoter construct previously shown to direct transgene expression specifically to ciliated cells, we have generated transgenic mice expressing human cystic fibrosis transmembrane conductance regulator (CFTR) in the murine tracheal and nasal epithelia. RNA analysis demonstrated levels of CFTR expression is greater than or equal to the level of endogenous mouse CFTR. Immunoprecipitation and western blotting demonstrated the production of human CFTR protein, and immunochemistry confirmed that CFTR was expressed in the apical region of ciliated cells. The transgenic animals were bred to CFTR null mice (Cftr(tm1Unc)) to determine if expression of CFTR from the FOXJ1 promoter is capable of correcting the airway defects in Cl(-) secretion and Na(+) absorption that accompany CF. Isolated trachea from neonatal CF mice expressing the FOXJ1/CFTR transgene demonstrated a correction of forskolin-stimulated Cl(-) secretion. However, expression of human CFTR in ciliated cells of the nasal epithelia failed to significantly change the nasal bioelectrics of the CF mice.

Novel Therapies for the Treatment of Cystic Fibrosis: New Developments in Gene and Stem Cell Therapy

Cystic fibrosis (CF) was one of the first target diseases for lung gene therapy. Studies of lung gene transfer for CF have provided many insights into the necessary components of successful gene therapy for lung diseases. Many advancements have been achieved with promising results in vitro and in small animal models. However, studies in primate models and patients have been discouraging despite a large number of clinical trials. This reflects a number of obstacles to successful, sustained, and repeatable gene transfer in the lung. Cell-based therapy with embryonic stem cells and adult stem cells (bone marrow or cord blood), have been investigated recently and may provide a viable therapeutic approach in the future. In this article, the authors review CF pathophysiology with a focus on specific targets in the lung epithelium for gene transfer and summarize the current status and future directions of gene- and cell-based therapies.

Culture of murine nasal epithelia: model for cystic fibrosis

The ion transport defects reported for human cystic fibrosis (CF) airways are reproduced in nasal epithelia of the CF mouse. Although this tissue has been studied in vivo using the nasal potential difference technique and as a native tissue mounted in the Ussing chamber, little information is available on cultured murine nasal epithelia. We have developed a polarized cell culture model of primary murine nasal epithelia in which the CF tissue exhibits not only a defect in cAMP-mediated Cl- secretion but also the Na+ hyperabsorption and upregulation of the Ca2+-activated Cl- conductance observed in human airways. Both the wild-type and CF cultures were constituted predominantly of undifferentiated cuboidal columnar cells, with most cultures exhibiting a small number of ciliated cells. Although no goblet cells were observed, RT-PCR demonstrated the expression of Muc5ac RNA after approximately 22 days in culture. The CF tissue exhibited an adherent layer of mucus similar to the mucus plaques reported in the distal airways of human CF patients. Furthermore, we found that treatment of CF preparations with a Na+ channel blocker for 7 days prevented formation of mucus adherent to epithelial surfaces. The cultured murine nasal epithelial preparation should be an excellent model tissue for gene transfer studies and pharmacological studies of Na+ channel blockers and mucolytic agents as well as for further characterization of CF ion transport defects. Culture of nasal epithelia from DeltaF508 mice will be particularly useful in testing drugs that allow DeltaF508 CFTR to traffic to the membrane.

CFTR involvement in nasal potential differences in mice and pigs studied using a thiazolidinone CFTR inhibitor

Nasal potential difference (PD) measurements have been used to demonstrate defective CFTR function in cystic fibrosis (CF) and to evaluate potential CF therapies. We used the selective thiazolidinone CFTR inhibitor CFTR(inh)-172 to define the involvement of CFTR in nasal PD changes in mice and pigs. In normal mice infused intranasally with a physiological saline solution containing amiloride, nasal PD was -4.7 +/- 0.7 mV, hyperpolarizing by 15 +/- 1 mV after a low-Cl- solution, and a further 3.9 +/- 0.5 mV after forskolin. CFTR(inh)-172 produced 1.1 +/- 0.9- and 4.3 +/- 0.7-mV depolarizations when added after low Cl- and forskolin, respectively. Systemically administered CFTR(inh)-172 reduced the forskolin-induced hyperpolarization from 4.7 +/- 0.4 to 0.9 +/- 0.1 mV but did not reduce the low Cl(-)-induced hyperpolarization. Nasal PD was -12 +/- 1 mV in CF mice after amiloride, changing by <0.5 mV after low Cl- or forskolin. In pigs, nasal PD was -14 +/- 3 mV after amiloride, hyperpolarizing by 13 +/- 2 mV after low Cl- and a further 9 +/- 1 mV after forskolin. CFTR(inh)-172 and glibenclamide did not affect nasal PD in pigs. Our results suggest that cAMP-dependent nasal PDs in mice primarily involve CFTR-mediated Cl- conductance, whereas cAMP-independent PDs are produced by a different, but CFTR-dependent, Cl- channel. In pigs, CFTR may not be responsible for Cl- channel-dependent nasal PDs. These results have important implications for interpreting nasal PDs in terms of CFTR function in animal models of CFTR activation and inhibition.

In vivo microdialysis for determination of nasal liquid ion composition

Airway surface liquid (ASL) contains substances important in mucociliary clearance and airway defense. Little is known about substance concentrations in ASL because of its small volume and sampling difficulties. We used in vivo microdialysis (IVMD) to sample liquid lining the nasal cavity without net volume removal and incorporated into IVMD a potential difference (PD) electrode to assess airway integrity. The cystic fibrosis (CF) mouse nasal epithelia exhibit ion transport defects identical to those in CF human airways and, thus, are a good model for CF disease. We determined that nasal liquid [Na+] (107 +/- 4 mM normal; 111 +/- 9 mM CF) and [Cl-] (120 +/- 6 mM normal; 122 +/- 4 mM CF) did not differ between genotypes. The nasal liquid [K+] (8.7 +/- 0.4 mM) was significantly less in normal than in CF mice (16.6 +/- 4 mM). IVMD accurately samples nasal liquid for ionic composition. The ionic composition of nasal liquid in the normal and CF mice is similar.

The temporal course of adenovirus-mediated gene transfer in the rat larynx

OBJECTIVE

Polypeptide growth factors have important influences on wound-healing and scar tissue formation. Specific growth factors or their inhibitors may potentially decrease scar tissue formation and prevent subglottic stenosis. Gene transfer using recombinant adenovirus may be an ideal method to mediate endogenous production of growth factors to inhibit fibrosis.

STUDY DESIGN

The study incorporated adenovirus-mediated transduction of normal and stenotic rat larynges and histologic analysis of the sequential expression of a beta-galactosidase marker gene over time.

SETTING

The study was conducted at the animal care facility of an academic children's hospital.

RESULTS

We report successful transduction in normal and injured rat larynx with peak expression of beta-galactosidase at 2 days after transduction and almost complete disappearance by 7 days. There appeared to be an early inflammatory response to the viral injection, but at 7 and 14 days after injection (transduction) the uninjured rat larynges resumed a normal histologic appearance. All distant sites stained negative for beta-galactosidase.

CONCLUSION

Recombinant adenovirus-mediated gene transfer is feasible in the rat larynx with transient duration and limited toxicity.

SIGNIFICANCE

Adenovirus-mediated gene transfer has the potential to deliver growth factors that modulate wound healing and inflammation in the larynx by inhibiting fibrosis.

Partial correction of defective Cl(-) secretion in cystic fibrosis epithelial cells by an analog of squalamine

Defective cystic fibrosis (CF) transmembrane conductance regulator (CFTR)-mediated Cl(-) transport across the apical membrane of airway epithelial cells is implicated in the pathophysiology of CF lungs. A strategy to compensate for this loss is to augment Cl(-) transport through alternative pathways. We report here that partial correction of this defect could be attained through the incorporation of artificial anion channels into the CF cells. Introduction of GL-172, a synthetic analog of squalamine, into CFT1 cells increased cell membrane halide permeability. Furthermore, when a Cl(-) gradient was generated across polarized monolayers of primary human airway or Fischer rat thyroid cells in an Ussing chamber, addition of GL-172 caused an increase in the equivalent short-circuit current. The magnitude of this change in short-circuit current was ~30% of that attained when CFTR was maximally stimulated with cAMP agonists. Patch-clamp studies showed that addition of GL-172 to CFT1 cells also increased whole cell Cl(-) currents. These currents displayed a linear current-voltage relationship and no time dependence. Additionally, administration of GL-172 to the nasal epithelium of transgenic CF mice induced a hyperpolarization response to perfusion with a low-Cl(-) solution, indicating restoration of Cl(-) secretion. Together, these results demonstrate that in CF airway epithelial cells, administration of GL-172 is capable of partially correcting the defective Cl(-) secretion.

EGTA enhancement of adenovirus-mediated gene transfer to mouse tracheal epithelium in vivo

Administration of recombinant adenoviral (AdV) vectors to animals can lead to inflammatory and immune responses. For therapeutic indications in which repeated treatment is necessary, such as cystic fibrosis (CF), these responses can limit the therapeutic usefulness of the vector. In principle, the utility of the vector can be improved by increasing its therapeutic index, that is, by either increasing its efficacy or decreasing its toxicity. A strategy that would enhance the efficacy of an adenoviral approach would allow the use of fewer virus particles to achieve a given level of transgene expression, and thereby also reduce unwanted effects such as immune responses. Following up on our observation that treating polarized normal human bronchial epithelial cells with calcium (Ca(2+))-free medium or the calcium chelator ethylene glycol-bis(beta-aminoethyl ether)-N,N,N',N'-tetraacetic acid (EGTA) significantly enhanced the subsequent transfection of these cells with cationic lipid:pDNA complexes, we have now asked whether such a treatment protocol might also improve the ability of AdV to infect these cells. Treating polarized airway epithelial cells with EGTA led to a dramatic increase in AdV-mediated transduction, as demonstrated by an approximately 50-fold increase in transgene expression. This strategy was also tested in vivo and resulted in substantial increases (up to 50-fold) in the ability of AdV vectors to infect mouse tracheal epithelium. Transfection of mouse trachea with an AdV aerosol was also significantly increased by pretreatment with EGTA. The enhancing effects of EGTA could not be duplicated with hypo- or hyperosmotic treatments. Light microscopy of mouse trachea that had been EGTA treated and then infected with AdV demonstrated an EGTA-mediated AdV infection of airway epithelial cells. The apparent enhanced potency of AdV for airway cells resulting from this strategy provides a significant increase in the therapeutic index of this gene delivery vector, and may increase the likelihood that it can be used for clinical indications requiring chronic administration of the vector.

Cationic liposome-mediated gene transfer to rat salivary epithelial cells in vitro and in vivo

BACKGROUND

Previously we have shown that gene transfer to salivary gland epithelial cells readily occurs via recombinant adenoviruses, although the response is short-lived and results in a potent host immune response. The aim of the present study was to assess the feasibility of using cationic liposomes to mediate gene transfer to rat salivary cells in vitro and in vivo.

METHODS

Initially, for transfection in vitro, we used two cationic liposome formulations (GAP-DLRIE/DOPE and DOSPA/DOPE) complexed with plasmid encoding human growth hormone (hGH) as a reporter gene. Thereafter, using GAP-DLRIE/DOPE, plasmids were transferred to rat salivary glands in vivo, and hGH levels measured in saliva, serum and gland extracts.

RESULTS

Under optimal conditions, transfection of rat submandibular glands (SMGs) was consistently observed. Approximately 95% of the cells transfected with a plasmid encoding beta-galactosidase were acinar cells. Maximal hGH expression was obtained during the first 48 h post-transfection using a plasmid encoding the hGH cDNA and complexed with GAP-DLRIE/DOPE. hGH was detected in gland extracts and saliva, and occasionally in serum. No systemic or local gland pathology was consistently or significantly observed.

CONCLUSIONS

The levels of the reporter gene product, hGH, obtained after GAP-DLRIE/DOPE-mediated gene transfer are considerably lower (<0.5%) than those achieved with adenoviral vectors (10(8) PFU). Nonetheless, cationic liposome-mediated gene transfer to salivary glands may be useful for potential therapeutic applications.

Airway gene transfer in mouse nasal-airways: importance of identification of epithelial type for assessment of gene transfer

Mouse nasal airways are often used for the assessment of both reporter and cystic fibrosis transmembrane conductance regulator (CFTR) gene transfer to respiratory epithelia. However, the mouse nasal cavity is lined by both olfactory (OE) and respiratory epithelium (RE). Previous gene transfer studies have suggested that OE may be more efficiently transduced by adenoviral vectors than RE. However, to provide data pertinent to CFTR gene transfer in humans, measurements of CFTR function in mice by transepithelial potential difference (TPD) should be directed towards respiratory rather than olfactory epithelium. We report a new technique to mark the position of the TPD sensing cannula tip in the mouse nasal cavity that permitted us to correlate TPD measurements with epithelial cell type. Using this technique, we found TPD values did not discriminate between respiratory and olfactory epithelia. We next assessed relationships between anatomic regions accessed by the TPD cannula and epithelial type. The frequently used insertion depth of approximately 5 mm from the nose tip predominantly recorded the TPD from anterior dorsal olfactory epithelium. Measurement of the TPD of respiratory epithelium in our study was maximized by insertion of the TPD cannula probe to 2.5 mm depth. Because TPD measurements are not sensitive to epithelial type, adequate control of position and TPD catheter insertion depth are required to ensure accurate estimation of CFTR gene transfer into the target RE in the mouse nasal cavity.

A murine tracheal culture system to investigate parameters affecting gene therapy for cystic fibrosis

Cystic fibrosis (CF) is a life-threatening condition caused by mutations in the cystic fibrosis transmembrane conductance regulator gene (CFTR). Delivery of the CFTR gene to the airways offers a potential treatment for CF but requires improvement in efficiency to obtain clinical benefit. We have developed a murine tracheal culture system that maintains tissue integrity as judged by normal histological appearance, high transepithelial resistance and electrophysiological responses similar to fresh tissue. This ex vivo system allows precise control of gene delivery parameters to a structure that retains the in vivo cellular architecture. We have demonstrated correction of CFTR-dependent Cl- secretion following ex vivo delivery of the CFTR gene to tracheas from CF null mice. We have used this system to examine parameters affecting liposome-mediated gene delivery to the upper airway such as plasmid dose. We have also found that a contact time of 1 min for the transfection mixture is sufficient to achieve significant DNA binding and maximal reporter gene expression.

Restoration of cyclic adenosine monophosphate-stimulated chloride channel activity in human cystic fibrosis tracheobronchial submucosal gland cells by adenovirus-mediated and cationic lipid-mediated gene transfer

In human airways, the cystic fibrosis (CF) transmembrane conductance regulator (CFTR) is predominantly expressed in serous cells of the tracheobronchial glands. Despite considerable evidence that submucosal glands are important contributors to the pathophysiology of CF lung disease, most attempts at CFTR gene transfer have primarily targeted airway surface epithelial cells. In this study, we systematically evaluated CFTR gene transfer into cultures of immortalized CF human tracheobronchial submucosal gland (6CFSMEO) cells using adenovirus and cationic lipid vectors. We found that the efficiency of adenovirus-mediated gene transfer was comparable in 6CFSMEO and CFT1 cells (a surface airway epithelial cell line isolated from a subject with CF). So was the ranking order of adenovirus vectors containing different enhancers/promoters (CMV >> E1a approximately phosphoglycerokinase), as determined by both X-Gal staining and quantitative measurement of beta-galactosidase activity. Further, we provide the first demonstration that cationic lipids mediate efficient gene transfer into 6CFSMEO cells in vitro. The transfection efficiency at optimal conditions was higher in 6CFSMEO than in CFT1 cells. Finally, either infection with adenoviral vectors or transfection with cationic lipid:plasmid DNA complexes encoding CFTR significantly increased chloride (Cl-) permeability, as assessed using the 6-methoxy-N-(3-sulfopropyl)-quinolinium (SPQ) fluorescence assay, indicating restoration of functional CFTR Cl- channel activity. These data show that although the mechanisms of transfection may be different between the two cell types, 6CFSMEO cells are as susceptible as CFT1 cells to transfection by adenoviral and cationic-lipid gene transfer vectors.

Enhanced in vivo airway gene transfer via transient modification of host barrier properties with a surface-active agent

Effective adenoviral gene therapy requires efficient viral vector entry into epithelial cells. Injured airway epithelia display enhanced gene transfer, reflecting in part increased vector access to protected cell populations and/or protected basolateral membranes. We tested whether adenoviral gene transfer is enhanced by modification of the epithelial barrier in mouse nasal airways with a nonionic detergent (polidocanol, PDOC). In C57BL/6 mice, 1.6 x 10(9) PFU of Ad5CMV LacZ (AdLacZ) instilled into the right nostril produced negligible gene transfer to the nasal epithelium 2 days after dosing, but significant, dose-dependent increases in gene transfer were achieved by pretreatment with PDOC. Permeation of the electron-dense tracer lanthanum into the intercellular junctions of PDOC (0.1%)-treated murine nasal epithelium, but not into intercellular junctions of vehicle controls, is consistent with PDOC-mediated increases in tight junctional permeability. In CF(-/-) mice, significant gene expression was not detectable after exposure to Ad5CBCFTR alone (1.4 x 10(9) PFU in 20 microl; AdCFTR), but PDOC pretreatment prior to AdCFTR instillation produced functional expression of CFTR (measured as deltaPD) 5 days after instillation. Because the development and testing of lung gene therapy will principally occur in children and adults with airway disease, AdLacZ gene transfer with and without PDOC pretreatment was examined in infected nasal airways. Gene expression was significantly reduced in infected as compared with uninfected airways. We conclude that the use of adjuvant surface-active and/or membrane-perturbing agents, synthetic or naturally derived, may provide a novel approach to enhancing the efficiency of adenoviral gene transfer.

Adenovirus-mediated persistent cystic fibrosis transmembrane conductance regulator expression in mouse airway epithelium

Replication-defective adenovirus (Ad) vectors have been used for gene transfer to the respiratory epithelium of experimental animals and individuals with cystic fibrosis. Studies from several laboratories have suggested that administration of first-generation Ad vectors results only in transient gene expression in the lung, due at least in part to destruction of vector-transduced cells by host cellular immune responses directed against viral proteins and/or immunogenic transgene products. We have constructed new Ad2-based, E1-deleted vectors encoding a weakly immunogenic transgene, the human cystic fibrosis transmembrane conductance regulator (hCFTR) under the control of the cytomegalovirus enhancer-promoter. These vectors contain wild-type E2 and E4 regions. These new Ad/CFTR vectors were instilled into the lungs of immunocompetent C57BL/6, BALB/c, and C3H mice. In vitro cytotoxic T lymphocyte (CTL) analysis indicated the presence of Ad-specific CTLs in treated mice. However, we were not able to demonstrate a CTL response specific for hCFTR. Reverse transcriptase PCR analysis demonstrated that hCFTR mRNA expression continued in all three strains of mice for at least 70 days, the last time point analyzed. The E3 region did not play a significant role in persistence of the Ad/CFTR vectors in the mouse lung. Functional hCFTR expression was also observed in the nasal epithelia of CF mutant mice. These results suggest that long-term expression of hCFTR is possible in the airway epithelia of immunocompetent mice without radical modification of Ad vector and in spite of the presence of CTLs.

Efficiency of cationic lipid-mediated transfection of polarized and differentiated airway epithelial cells in vitro and in vivo

Systematic analysis of a large number of different cationic lipids has led to the identification of novel structures (GL-67) and formulations of cationic lipid:plasmid DNA (pDNA) complexes that facilitate high levels of gene expression in lungs of mice. However, despite significant improvement in gene transfer activity, we show here that the efficiency of GL-67-mediated gene transduction of intact airway epithelia is still relatively low. Administration of GL-67:pCF1-CFTR (encoding the cystic fibrosis transmembrane conductance regulator) complexes into the nasal epithelium of cystic fibrosis (CF) transgenic mice resulted only in marginal correction of the ion transport defects. Measurements of nasal potential differences (PD) showed no correction of the sodium (Na+) transport defect, and only partial restitution of the chloride (Cl-) transport defect was achieved in a small proportion of the animals after perfusion of the nasal epithelium with the complexes. Furthermore, in contrast to results obtained following instillation of GL-67:pDNA complexes into the lungs of mice, perfusion of GL-67:pDNA into the nasal epithelium resulted only in a moderate enhancement of gene transduction activity relative to that attained with naked pDNA alone. To determine the basis for this low efficiency of transfection, a series of studies was conducted to identify some of the barriers governing cationic lipid-mediated gene transfer to the airway epithelium. We show here that the transfection activity of GL-67 was affected by the polarization, differentiation, and proliferative state of the cells. Diminished transfection activity was observed with nonmitotic, highly polarized and differentiated airway epithelial cells. This observed reduction in gene expression with nonmitotic cells was determined to be due in part to inefficient nuclear translocation of the pDNA from the cytoplasm. Together these data indicate that much improvement in the ability of cationic lipids to transfect polarized and differentiated airway epithelial cells is a necessary prerequisite for effective cationic lipid-mediated gene therapy of airway diseases such as CF.