Retinal pericytes (green) are a component of blood vessels (red) that contact endothelial cells (blue).  Pericytes also interact with glial cells such as astrocytes (white), receiving signals that modulate contraction, dilation, and permeability of the vascular wall.  In diseases such as diabetic retinopathy, or retinopathy of prematurity (ROP) the blood vessels of the retina can be severely effected, leading to various degrees of retinal degeneration that may ultimately result in visual impairment.  Understanding how these contractile cells breakdown may be a step towards developing improved therapeutic approaches for diseases and conditions involving the vascular system.