J. T. Vuong1,2, D. T. Dao1,2, A. Pan1,2, L. Anez-Bustillos1,2, D. Bielenberg1,2, M. Puder1,2 1Boston Children’s Hospital,Department Of Surgery,Boston, MA, USA 2Boston Children’s Hospital,Vascular Biology Program,Boston, MA, USA
Introduction:
Vascular endothelial growth factor (VEGF) plays a key role in angiogenesis with implications for organ development and regeneration. Our group has previously demonstrated that systemic VEGF administration accelerated compensatory lung growth (CLG) in a murine model of left pneumonectomy. The aims of this study are to determine the mechanism of how VEGF accelerates CLG and to explore nasal delivery as an alternative route for VEGF administration.
Methods:
Eight-week old C57Bl6 male mice underwent left pneumonectomy, followed by daily nasal instillation of VEGF at 0.5 mg/kg (N=10) or isovolumetric saline (N=10). Mice were euthanized on postoperative day (POD) 4, and lungs were harvested for immunohistochemistry and protein expression analysis.
To determine the mechanisms of VEGF-mediated acceleration of lung growth, human lung microvascular endothelial cells (HMVEC-L) were treated with or without VEGF (10 ng/mL) for 24 hours. Conditioned media were then placed on human bronchial epithelial cells (HBEC). Viability of HBEC cells was assessed every 24 hours for 72 hours through a colorimetric assay. Protein contents of HMVEC-L conditioned medium were characterized with an angiogenesis array.
Results:
Compared to saline-treated mice, inhaled VEGF treatment resulted in increased expression of heparin binding EGF-like growth factor (HB-EGF) (P = 0.02) and activation of its main receptor, epidermal growth factor receptor (P = 0.03), which promotes epithelial cell proliferation and differentiation (Figure 1A). However, there was no difference in proHB-EGF expression on immunohistochemistry, indicating that the increase in HB-EGF levels was due to increased shedding of the factor. Mice in the VEGF group displayed a lower Ki-67 proliferation index (P=0.03) on POD 4, reflecting that cellular proliferation was near completion in VEGF-treated mice and that VEGF accelerated compensatory lung growth.
Conditioned medium from VEGF-treated HMVEC-L increased HBEC viability (P=0.046) and contained a 6.5-fold increase in HB-EGF level compared to VEGF-negative conditioned medium (Figure 1B).
Conclusion:
Nasal delivery of VEGF may accelerate compensatory lung growth via increased shedding of heparin binding EGF-like growth factor.
