Date Published: June 7, 2018
Publisher: Public Library of Science
Author(s): Duy T. Dao, Jacqueline T. Vuong, Lorenzo Anez-Bustillos, Amy Pan, Paul D. Mitchell, Gillian L. Fell, Meredith A. Baker, Diane R. Bielenberg, Mark Puder, Yu Ru Kou.
Vascular endothelial growth factor (VEGF) has previously been demonstrated to accelerate compensatory lung growth (CLG) in mice and may be a useful therapy for pulmonary hypoplasia. Systemic administration of VEGF can result in side effects such as hypotension and edema. The aim of this study was to explore nasal delivery as a route for intrapulmonary VEGF administration. Eight-week-old C57BL/6 male mice underwent left pneumonectomy, followed by daily nasal instillation of VEGF at 0.5 mg/kg or isovolumetric saline. Lung volume measurement, morphometric analysis, and protein expression studies were performed on lung tissues harvested on postoperative day (POD) 4. To understand the mechanism by which VEGF accelerates lung growth, proliferation of human bronchial epithelial cells (HBEC) was assessed in a co-culture model with lung microvascular endothelial cells (HMVEC-L) treated with and without VEGF (10 ng/mL). The assay was then repeated with a heparin-binding EGF-like growth factor (HB-EGF) neutralizing antibody ranging from 0.5–50 μg/mL. Compared to control mice, the VEGF-treated group displayed significantly higher lung volume (P = 0.001) and alveolar count (P = 0.005) on POD 4. VEGF treatment resulted in increased pulmonary expression of HB-EGF (P = 0.02). VEGF-treated HMVEC-L increased HBEC proliferation (P = 0.002) while the addition of an HB-EGF neutralizing antibody at 5 and 50 μg/mL abolished this effect (P = 0.01 and 0.002, respectively). These findings demonstrate that nasal delivery of VEGF enhanced CLG. These effects could be mediated by a paracrine mechanism through upregulation of HB-EGF, an epithelial cell mitogen.
Vascular endothelial growth factor (VEGF) is an endothelial cell mitogen that serves as a key regulator of angiogenesis and neovascularization . It is essential for the normal development and regeneration of human tissues and organs [2–4]. The absence of VEGF signaling has devastating effects on fetal lung development and its neutralization is associated with decreased lung maturation, surfactant production, and capillary and alveolar hypoplasia in animal models [5,6]. In addition, low levels of VEGF have been observed in human and animal models of infantile diseases such as respiratory distress syndrome and pulmonary hypoplasia in congenital diaphragmatic hernia (CDH) [7,8]. Conversely, increased expression of VEGF through gene therapy increases lung angiogenesis and promote alveolar growth in hyperoxia-induced injury in rat lungs . Results from these studies support the hypothesis that there may be a potential role for VEGF in mediating regenerative lung growth.
Previous work from our group demonstrated the effects of systemic VEGF on accelerating CLG after left PNX . In this study, we sought to replicate these results with topical administration of VEGF. Consideration was given to aerosol inhalation, intratracheal instillation, and nasal instillation. Although aerosol inhalation has been shown to result in a more uniform pulmonary distribution, dosage delivery is variable and limited . Intratracheal instillation requires deep sedation and intratracheal intubation, which is traumatic to the animal if performed on a daily basis. Although nasal instillation presents certain limitations, such as heterogenous intrapulmonary distribution and central nervous system absorption , it appeared to be the optimal approach due to the benefits of controlled dosage and light sedation requirement.