There is still controversy over the mechanisms by which normal blood vessels develop. The Lutty lab has demonstrated that retinal blood vessels develop initially from vascular precursor cells (angioblasts) that exist in retina early in development.
Our lab has recently identified a factor that may attract these angioblasts to inner retina and may stimulate their assembly into blood vessels. This assembly of and differentiation or maturation of the precursors is called vasculogenesis.
In Picture 1, the blood vessels and precursors are stained red with a marker that we found for angioblasts called CD39. The individual cells outside of the blood vessels are the angioblasts and the endothelial cells in the formed blood vessels continue to express CD39 through life. Our lab has grown these angioblasts in culture and found that they have the potential to differentiate or change into two different cell types (i.e. angioblasts are multipotent). The two cell types are the components of normal blood vessels: endothelial cells that line the lumen of the blood vessels and pericytes that are the contractile cell on the outside of the blood vessel. We have also discovered that the choroidal vasculature develops by hemovasculogenesis: the formation of blood cells (white blood cells and red blood cells) and blood vessel cells from a common precursor, the hemangioblast.