Accessory cells in vessels of the paranatal human retina.

Retinas of the paranatal period contain two types of cell clusters that are generally believed to play a role in the developing vasculature. The more posterior cluster consists of angioblastic cells, which undergo lumenization to form the definitive vessels. Anterior to this cluster and separated from it by a distinct boundary are clusters of spindle cells extending a variable distance toward the periphery. These clusters of spindle cells maintain a fixed position relative to the angioblastic masses, without any admixture of the two. The precise function of the spindle cells in the vascularizing process has been a subject of controversy. We found evidence to identify them as glia and to suggest that their role is to provide an energy source for the developing retina as the hyaloid vessels recede and until the retinal vessels take over this function. It further appears that congenital failure of the vessels to develop may result in a persistence of these spindle cells, in the form of hyperplastic glia in the inner layers of the retina. Our study included normal eyes from full-term and premature infants and eyes from patients with retinopathy of prematurity (oxygen-related retinopathy), anencephaly, and other congenital anomalies.