Formation and Regression of the Primary Vitreous and Hyaloid Vascular System

Abstract

Ocular tissues are oxygenated and nourished by transient vessel networks during embryogenesis. In most mammals, these vessel networks undergo timed regression to provide a clear optical path to the retina. The failure of these vessel beds to fully regress results in a myriad of disorders. In this chapter, we describe the developmental timeline of these vessel networks and delve into the signaling mechanisms uncovered in mice that orchestrate the precisely controlled process of hyaloid vascular regression. A major signaling response involves the integration of the Wnt/β-catenin- Angiopoietin pathways to tightly regulate both cell proliferation and apoptosis during vessel regression. An additional mechanism, discovered recently, implicates retinal neurons and a light response pathway in hyaloid regression. This pathway is dependent on the balance of a potent angiogenic factor VEGFA (vascular endothelial growth factor A) and dopamine levels in the eye.