Abstract
Purpose :
Semaphorin 6A (Sema6A), an axon-guidance molecule, has been shown to play a critical role in the regulation of endothelial survival and vascular development. We have previously demonstrated that neuronal Sema6A impeded vascular regeneration in oxygen-induced retinopathy (OIR), which was modulated by Nrf2. The objective of this study was to gain insights into Sema6A function in endothelial cells in OIR.
Methods :
For OIR studies, mice were subjected to hyperoxia from postnatal day 7 (P7) to 12, followed by return to room air. The expression of Sema6A and its receptor, plexinA2, were analyzed in retinal cryosections by fluorescence staining at OIR P17. Avascular retinal area and neovascularization were measured in retinal flatmounts at P12 and P17. Cell-specific knockouts of Sema6A were used to dissect the specific role of Sema6A in endothelial cells. Blood-retinal barrier function was assessed by measuring retinal levels of the systemically administered tracer, [3H] mannitol. VEGF protein concentration was assessed using Mouse VEGF DuoSet ELISA kit. Scotopic electroretinographs were obtained at P40. mRNA levels were assessed by quantitative real-time PCR.
Results :
Sema6A and plexinA2 were highly expressed in retinal blood vessels in OIR. Deletion of endothelial Sema6A led to a slight increase in retinal vaso-obliteration at OIR P12, but significantly increased avascular retina and pathologic retinal neovascularization at P17 compared to wild-type. Marked increase in retinal vascular leakage and reduction of inner-retinal scotopic b-wave response were observed in mice deficient of endothelial Sema6A. VEGF protein levels were not affected by loss of Sema6A in endothelial cells. Deletion of endothelial Sema6A did not change the retinal mRNA level of Sema3A, Sema3E or Sema3F at OIR P17.
Conclusions :
These studies suggest that endothelial Sema6A plays a direct role in promoting revascularization of avascular retina in oxygen-induced retinopathy.
This is an abstract that was submitted for the 2018 ARVO Annual Meeting, held in Honolulu, Hawaii, April 29 - May 3, 2018.