Abstract
Purpose :
Degenerative changes of retinal ganglion cells (RGCs) are characterized by progressive visual field loss and may lead to blindness in neurodegenerative eye diseases such as glaucoma andischemic retinopathies. Angiopoietin-1 (Ang-1) and -2 (Ang-2) and their receptor Tie2 have previously been shown to have major roles in angiogenesis and inflammation. However, whether Ang-1, Ang-2, and Tie2 are able to influence neuronal survival in the retina has been poorly investigated. The purpose of this work was to determine the expression and regulation of Ang-1, Ang-2 and Tie2 in retinal cells and to investigate possible consequences of the interaction of RGCs with angiopoietins.
Methods :
RT-PCR or immunostaining was used to examine the expression of Ang-1, Ang-2 and Tie2 in primary retinal cells and in R28 cells, a retinal progenitor cell line. R28 cells deprived of growth factors were cultured for 24 hours under normoxia or hypoxia (0.2% O2), stimulated with VEGF-A (100 ng/mL) or PEDF (500 ng/mL), and regulation of Ang-1, Ang-2 and Tie2 was determined by qPCR. The expression levels of the neuroprotective factors PEDF, VEGF-A, IL-6 and BDNF in R28 cells were determined following Ang-1- and Ang-2-stimulation.
Results :
Ang-1, Ang-2 and Tie2 are expressed in RGCs, Müller cells, retinal endothelial cells, RPE cells and R28 cells. Ang-1 and Ang-2 levels in R28 cells and Müller cells were downregulated by VEGF-A and PEDF, whereas neuronal Tie2 expression was not altered. VEGF-A, IL-6 and BDNF were upregulated under hypoxia in R28 cells, while PEDF was downregulated. However, PEDF downregulation was completely reversed by Ang-1 or Ang-2. Ang-1 and -2 stimulation of R28 cells had no effect on the expression of VEGF-A, IL-6 and BDNF, either under normoxia or under hypoxia.
Conclusions :
In the retina, Ang-1 and Ang-2 are produced by several non-vascular cell types. Retinal neurons are susceptible to (auto-/paracrine) stimulation by Ang-1 and -2. Both angiopoietins may be important in maintaining enhanced PEDF levels under hypoxia suggesting that, via PEDF upregulation, Ang-1 and Ang-2 are involved in PEDF-mediated neuroprotection in the retina.
This abstract was presented at the 2023 ARVO Annual Meeting, held in New Orleans, LA, April 23-27, 2023.