The therapeutic potency of exogenous administration of adrenomedullin-2 in ocular neovascular diseases

Abstract

Purpose : Adrenomedullin-2 (AM2) or intermedin, a family peptide of adrenomedullin (AM), is a novel peptide exerting a variety of biological effects, especially regulation of cardiovascular homeostasis. AM and AM2 partially share the receptor system, but functional differentiation is not well understood. Recently, protective effects of endogenous AM2 against various diseases are reported. However, little is known about the pathophysiological roles of AM2 in ocular diseases. In the current study, we analyzed the pathophysiological roles of AM2 in ocular neovascularization by exogenous AM2 administration.

Methods : C57BL/6J mice were subjected to laser-induced choroidal neovascularization (LI-CNV) model and oxygen-induced retinopathy (OIR) model.
In LI-CNV model, 9-12 week-old male mice were treated with intravitreal injection (iv) of 1.5μl PBS, AM (10^-7M) or AM2 (10^-7M) after CNV induction. After 7 days of CNV induction, CNV size was evaluated by perfused fluorescein-labeled dextran, and macrophage infiltration and fibrosis were evaluated by immunostaining of F4/80 and αSMA, respectively.
In OIR model, both genders of mice were subjected to hyperoxia at 75% oxygen for 5 days from postnatal day (P)7 through P12. P12 mice were treated with iv of 1.5μl PBS, AM (10^-7M) or AM2 (10^-7M). At P17, avascular area and neovascular tuft area (NVT) were quantified in retinal flatmounts stained with isolectin B4.
In vitro, cell migration of TR-iBRB, a rat retinal endothelial cell line, was evaluated by scratch assay with PBS, AM (10^-7M) or AM2 (10^-7M). The cell migration distances 12 hours after scratch were evaluated.

Results : In LI-CNV model, CNV size, F4/80-positive cells and αSMA-positive area were significantly reduced by AM or AM2 iv compared to PBS iv(p<0.05).
In OIR model, avascular area was significantly reduced by AM or AM2 iv compared to PBS iv(p<0.01). On the other hand, there was no significant difference in NVT between AM2 iv and PBS iv. NVT was significantly increased by AM iv compared to PBS or AM2 iv(p<0.05).
Addition of AM or AM2 significantly accelerated TR-iBRB cell migration compared to that of PBS(p<0.05).

Conclusions : These results suggest AM2 is expected as a novel therapeutic target of ocular neovascular diseases.

This is a 2020 ARVO Annual Meeting abstract.

 

LI-CNV was improved by AM or AM2 iv compared to PBS iv.

 

OIR model: Avascular area was reduced by AM or AM2 iv compared to PBS iv. NVT was deteriorated by AM iv compared to PBS or AM2 iv.