Anatomic Closure of the Premature Patent Ductus Arteriosus: The Role of CD14+/CD163+ Mononuclear Cells and Vascular Endothelial Growth Factor (VEGF) in Neointimal Mound Formation

Permanent closure of the newborn ductus arteriosus requires the development of neointimal mounds to completely occlude its lumen. Vascular endothelial growth factor is required for neointimal mound formation. The size of the neointimal mounds (composed of proliferating endothelial and migrating smooth muscle cells) is directly related to the number of VLA4 + mononuclear cells that adhere to the ductus lumen after birth. We hypothesized that VEGF plays a crucial role in attracting CD14 + /CD163 + mononuclear cells (expressing VLA4 + ) to the ductus lumen and that CD14 + /CD163 + cell adhesion to the ductus lumen is important for neointimal growth. We used neutralizing antibodies against VEGF and VLA-4 + to determine their respective roles in remodeling the ductus of premature newborn baboons. Anti-VEGF treatment blocked CD14 + /CD163 + cell adhesion to the ductus lumen and prevented neointimal growth. Anti-VLA-4 treatment blocked CD14 + /CD163 + cell adhesion to the ductus lumen, decreased the expression of PDGF-B (which promotes smooth muscle migration), and blocked smooth muscle influx into the neointimal subendothelial space (despite the presence of increased VEGF in the ductus wall). We conclude that VEGF is necessary for CD14 + /CD163 + cell adhesion to the ductus lumen and CD14 + /CD163 + cell adhesion is essential for VEGF-induced expansion of the neointimal subendothelial zone.