Desmin Ensheathment Ratio (DER) as an Indicator of Vessel Stability:: Evidence in Normal Development and in Retionopathy of Prematurity (ROP)

Abstract

Abstract: : Purpose: To develop a new measure of pericyte/endothelial interaction using the intermediate filament desmin as an indicator of pericyte ensheathment. To examine the Desmin Ensheathment Ratio (DER) in normal retinal vascular development and at various stages of kitten ROP. To explore the role of pericytes and smooth muscle cells (SMCs) in the pathogenesis of ROP, in particular Plus disease. Methods: Postnatal day (P)1–P45 kitten retinae were labelled with antibodies against desmin, α–smooth muscle actin (SMA) and Griffonia Simplicifolia lectin. Experimental kittens were exposed at birth to 60–70% oxygen for 4 days then returned to room air for 0–40 days (dRA). The ratio of desmin to lectin labelling on confocal images yielded the DER. Control and ROP tissue were also examined by electron microscopy. Results: During normal development, desmin+ pericytes were found throughout the vascular plexus, whereas differentiating SMA+ SMCs were present on radial vessels only. Immature vascular beds had a DER of 0.3 to 0.6 while in mature, stable capillary plexuses which predominated by P28, the DER was above 0.9. The hyperoxic stage of ROP resulted in the loss of intra–retinal vessels with desmin+ pericytes and SMA+ SMCs ensheathment. During the hypoxic stage, endothelial cells of the neovasculature adopted an abnormal rounded morphology, pericytes were present throughout the neovascular plexus, SMCs were associated with radial vessels and the DER of intraretinal and preretinal vessels ranged between 0.2 and 0.5. In the recovery stage, the DER increased in parallel with regression of pathology, reaching 0.9 by 34 dRA. Conclusions: Using our new measure of pericyte/endothelial interaction we have shown an association between vessel maturation and an increase in DER. Stabilisation of the DER by the fifth postnatal week was temporally coincident with the development of resistance to hyperoxia–induced vessel regression previously reported in the kitten. These observations lead us to suggest that a DER of 0.9 represents a vascular stability threshold and that pericyte desmin coverage of capillaries is a good indicator of vessel stability.

Keywords: retinopathy of prematurity • retinal neovascularization • pathology: experimental