Degeneration of astrocytes in feline retinopathy of prematurity causes failure of the blood-retinal barrier.

This study addresses the role of astrocytes in the genesis of retinopathy of prematurity, examined in the feline model of this condition. Evidence is presented that the hypoxia of retinopathy of prematurity, in addition to inducing vasoproliferation, damages the retina directly. Retinal neurons survive the hypoxia, but the astrocytes, which are involved in the formation of the glia limitans of the retinal vessels, degenerate. Astrocytes subsequently recolonize the retina after a delay that matches the period of leakiness of the proliferative vasculature (described in the companion article). Given the evidence from other studies that the barrier properties of vessels are induced by their glia limitans, the authors suggest that the initial lack of barrier properties in the new vasculature is caused by the degeneration of astrocytes and that the subsequent formation of those properties is induced by the astrocytes that recolonize the retina some days later. The observation that astrocytes are more sensitive to hypoxia than neurons, at least in developing tissue, was unexpected. The literature reporting on the damage caused to central nervous tissue by hypoxia is consistent in assessing neurons as more sensitive and glial changes as a reaction to neuronal damage. The sensitivity of astrocytes found in this study and earlier in vitro research suggests that degenerated astrocytes can be replaced and their structural and functional relationships reestablished.