Genetic modification of airway progenitors after lentiviral gene delivery to the amniotic fluid of murine fetuses

Stem cells, cell therapies, and bioengineering in lung biology and diseases. Comprehensive review of the recent literature 2010-2012

A conference, "Stem Cells and Cell Therapies in Lung Biology and Lung Diseases," was held July 25 to 28, 2011 at the University of Vermont to review the current understanding of the role of stem and progenitor cells in lung repair after injury and to review the current status of cell therapy and ex vivo bioengineering approaches for lung diseases. These are rapidly expanding areas of study that provide further insight into and challenge traditional views of mechanisms of lung repair after injury and pathogenesis of several lung diseases. The goals of the conference were to summarize the current state of the field, to discuss and debate current controversies, and to identify future research directions and opportunities for basic and translational research in cell-based therapies for lung diseases. The goal of this article, which accompanies the formal conference report, is to provide a comprehensive review of the published literature in lung regenerative medicine from the last conference report through December 2012.

In utero lung gene transfer using adeno-associated viral and lentiviral vectors in mice

Virus-mediated gene transfer to the fetal lung epithelium holds considerable promise for the therapeutic management of prenatally diagnosed, potentially life-threatening inherited lung diseases. In this study we hypothesized that efficient and life-long lung transduction can be achieved by in utero gene therapy, using viral vectors. To facilitate diffuse entry into the lung, viral vector was injected into the amniotic sac of C57BL/6 mice on embryonic day 16 (term, ∼ 20 days) in a volume of 10 μl. Vectors investigated included those based on adeno-associated virus (AAV) (serotypes 5, 6.2, 9, rh.64R1) and vesicular stomatitis virus G glycoprotein (VSV-G)-pseudotyped HIV-1-based lentivirus (LV). All vectors expressed green fluorescent protein (GFP) under the transcriptional control of various promoters including chicken β-actin (CB) or cytomegalovirus (CMV) for AAV and CMV or MND (myeloproliferative sarcoma virus enhancer, negative control region deleted) for LV. Pulmonary GFP gene expression was detected by fluorescence stereoscopic microscopy and immunohistochemistry for up to 9 months after birth. At equivalent vector doses (mean, 12 × 10(10) genome copies per fetus) three AAV vectors resulted in long-term (up to 9 months) pulmonary epithelium transduction. AAV2/6.2 transduced predominantly cells of the conducting airway epithelium, although transduction decreased 2 months after vector delivery. AAV2/9-transduced cells of the alveolar epithelium with a type 1 pneumocyte phenotype for up to 6 months. Although minimal levels of GFP expression were observed with AAV2/5 up to 9 months, the transduced cells immunostained positive for F480 and were retrievable by bronchoalveolar lavage, confirming an alveolar macrophage phenotype. No GFP expression was observed in lung epithelial cells after AAV2/rh.64R1 and VSV-G-LV vector-mediated gene transfer. We conclude that these experiments demonstrate that prenatal lung gene transfer with AAV vectors engineered to target pulmonary epithelial cells may provide sustained long-term levels of transgene expression, supporting the therapeutic potential of prenatal gene transfer for the treatment of congenital lung diseases.

Gene delivery to the airway

This unit describes generation of and gene transfer to several commonly used airway models. Isolation and transduction of primary airway epithelial cells are first described. Next, the preparation of polarized airway epithelial monolayers is outlined. Transduction of these polarized cells is also described. Methods are presented for generation of tracheal xenografts, as well as both ex vivo and in vivo gene transfer to these xenografts. Finally, a method for in vivo gene delivery to the lungs of rodents is included. Methods for evaluating transgene expression are given in the support protocols.

Jaagsiekte sheep retrovirus pseudotyped lentiviral vector-mediated gene transfer to fetal ovine lung

Viral vector-mediated gene transfer to the postnatal respiratory epithelium has, in general, been of low efficiency due to physical and immunological barriers, non-apical location of cellular receptors critical for viral uptake and limited transduction of resident stem/progenitor cells. These obstacles may be overcome using a prenatal strategy. In this study, HIV-1-based lentiviral vectors (LVs) pseudotyped with the envelope glycoproteins of Jaagsiekte sheep retrovirus (JSRV-LV), baculovirus GP64 (GP64-LV), Ebola Zaire-LV or vesicular stomatitis virus (VSVg-LV) and the adeno-associated virus-2/6.2 (AAV2/6.2) were compared for in utero transfer of a green fluorescent protein (GFP) reporter gene to ovine lung epithelium between days 65 and 78 of gestation. GFP expression was examined on day 85 or 136 of gestation (term is ∼145 days). The percentage of the respiratory epithelial cells expressing GFP in fetal sheep that received the JSRV-LV (3.18 × 10(8)-6.85 × 10(9) viral particles per fetus) was 24.6±0.9% at 3 weeks postinjection (day 85) and 29.9±4.8% at 10 weeks postinjection (day 136). Expression was limited to the surface epithelium lining fetal airways <100 μm internal diameter. Fetal airways were amenable to VSVg-LV transduction, although the percentage of epithelial expression was low (6.6±0.6%) at 1 week postinjection. GP64-LV, Ebola Zaire-LV and AAV2/6.2 failed to transduce the fetal ovine lung under these conditions. These data demonstrate that prenatal lung gene transfer with LV engineered to target apical surface receptors can provide sustained and high levels of transgene expression and support the therapeutic potential of prenatal gene transfer for the treatment of congenital lung diseases.

Stem cells and cell therapies in lung biology and lung diseases

The University of Vermont College of Medicine and the Vermont Lung Center, with support of the National Heart, Lung, and Blood Institute (NHLBI), the Alpha-1 Foundation, the American Thoracic Society, the Emory Center for Respiratory Health,the Lymphangioleiomyomatosis (LAM) Treatment Alliance,and the Pulmonary Fibrosis Foundation, convened a workshop,‘‘Stem Cells and Cell Therapies in Lung Biology and Lung Diseases,’’ held July 26-29, 2009 at the University of Vermont,to review the current understanding of the role of stem and progenitor cells in lung repair after injury and to review the current status of cell therapy approaches for lung diseases. These are rapidly expanding areas of study that provide further insight into and challenge traditional views of the mechanisms of lung repair after injury and pathogenesis of several lung diseases. The goals of the conference were to summarize the current state of the field, discuss and debate current controversies, and identify future research directions and opportunities for both basic and translational research in cell-based therapies for lung diseases.