Gene Transfer to the Pleural Mesothelium as a Strategy to Deliver Proteins to the Lung Parenchyma

Abstract

The pleura covers the lung parenchyma, chest wall, and diaphragm with a single layer of flat cells that are easy to genetically modify with adenovirus (Ad) vectors. Although intrapleural gene therapy has been used to treat intrapleural disorders, we hypothesized that it may also be used to deliver extracellular gene products to the lung parenchyma. In this context, this study is based on the concept that administration of adenovirus gene transfer vectors into the pleural cavity will mediate expression of gene products in mesothelial cells, and that the extracellular products produced by these genetically modified cells will reach the lung parenchyma. To assess this concept, Ad(beta)gal (expressing beta-galactosidase [beta-Gal]) or AdLuc (expressing luciferase) was administered into the right pleural cavity of BALB/c mice, as compared with intravenous injection via the jugular vein or the intratracheal route. Histologic assessment of lungs and pleural surface after intrapleural administration of Ad(beta)gal demonstrated beta-Gal expression limited to the pleural mesothelium and cells adjacent to the pleural surface. Right intrapleural administration of AdLuc showed higher level of luciferase in both the right and left lung (right vs. left, p > 0.8), compared with the intratracheal (p < 0.05) or intravenous routes (p < 0.02), that is, unilateral intrapleural administration is sufficient to transfer genes bilaterally to the pleura. To assess the ability of intrapleural gene transfer to modify lung parenchymal processes, CT26.CL25 tumor cells (3 x 10(5)) were injected via the jugular vein to generate tumor metastases in the lung parenchyma followed 24 hr later by administration to the right pleura of 5 x 10(8) PFU of Adsflt (an Ad "antiangiogenesis" vector expressing a soluble, secreted, extracellular portion of the Flt-1 receptor for vascular endothelial growth factor). Compared with phosphate-buffered saline, or the control vector AdNull (no transgene), mice receiving Adsflt by the intrapleural route had a marked suppression of tumor growth in the parenchyma of both lungs as assessed 12 days after tumor administration (p < 0.005). Treatment of preestablished lung metastases with Adsflt administered by the intrapleural route significantly improved long-term survival as compared with control animals (p < 0.0001). Thus, although intrapleural administration of an Ad vector encoding an intracellular protein mediates gene expression only in mesothelial cells and the local tissues, intrapleural delivery of a vector expressing a secreted protein can be used to modify processes throughout the lung parenchyma. In the context that intravascular gene transfer is an ineffective strategy to deliver gene products to the lung parenchyma, and that intratracheal administration is associated with alveolar inflammation secondary to host defenses against Ad vectors, these findings demonstrate that intrapleural administration represents a strategy that can be used to effectively deliver extracellular gene products to the lung parenchyma...

Inhalation delivery of manganese superoxide dismutase-plasmid/liposomes protects the murine lung from irradiation damage

“…35 The use of gene therapy vectors including adenovirus, adeno-associated virus, and plasmid/liposomes has been evaluated in inhalation models for transgene delivery in several disease categories. [36][37][38][39][40][41][42][43] The availability of ultrasonic nebulizer devices, and successful development of inhalant drug delivery systems for asthma, obstructive pulmonary disease, and pulmonary allergic reactions have provided significant resources with respect to blood dose delivery to primary, secondary, and tertiary bronchi. [41][42][43] A technique by which to transiently elevate pulmonary levels of a transgene protein would not be particularly desirable for therapy of patients with cystic fibrosis treatment; however, such transient and controllable expression could be potentially therapeutic for conditions requiring transient availability of pulmonary transgene proteins such as prior to an anticipated pulmonary toxic inhalation injury, or injury from a toxic agent with potential pulmonary negative sequelae, including intracavitary irradiation.…”

In vivo gene transfer of pigment epithelium-derived factor inhibits tumor growth in syngeneic murine models of thoracic malignancies

“…Vectors were then administered into the right pleural cavity 1 day after the intravenous tumor bolus. 18 Intrapleural administration of dilute (1:5 in PBS) methylene blue dye (1 mL) was initially performed to evaluate whether interpleural communication exists in BALB/c mice. To perform intrapleural gene delivery, mice were anesthetized via intraperitoneal injection with a cocktail of ketamine (100 mg/kg) and xylazine (10 mg/kg).…”

“…Intrapleural gene delivery as a strategy to express proteins in the pulmonary parenchyma is a novel approach that has only recently been described. 18 As gene expression is seen primarily in the periphery of the lung using this technique, penetration of the vector through the visceral pleura represents the most likely mechanism. The observation that instillation of AdPEDF into 1 pleural space results in tumor suppression bilaterally is best explained by the communication between hemithoraces in the BALB/c mouse, 18 which was readily demonstrable with methylene blue dye.…”

Gene Therapy for Alpha-1 Antitrypsin Deficiency Lung Disease

“…An alternative route to overcome the barriers to AAV AAT vector delivery to the lung via the respiratory epithelium is to target the lung pleura (136,137). The pleura presents several structural advantages that make it an attractive site for gene delivery targeting both the lung parenchyma and the systemic circulation, providing a large surface area for gene transfer that is easily accessible.…”