Investigation of the therapeutic effect of adrenomedullin on central retinal vein occlusion

Abstract

Purpose : Central retinal vein occlusion (CRVO) is an intractable disease that causes visual acuity loss due to retinal hemorrhage and macular edema. Adrenomedullin (AM) is vasoprotective and anti-inflammatory activity peptide. In this study, using a laser-induced CRVO model which we had reported (ARVO 2017 annual meeting), we investigated whether AM can be a therapeutic candidate for CRVO.

Methods : 9 to 12 week-old male AM knockout mice (KO), wild-type mice (WT) and WT mice systemically administered with AM by osmotic pump were used. After general anesthesia, 1 mg of Rose Bengal was intraperitoneally injected, photocoagulation was performed in the central retinal vein, and blood vessels were occluded. Fluorescein angiography (FA) was performed on the photocoagulation day 1, 3 and 7. After that, Fluorescein Isothiocyanate (FITC) was injected into the heart, and retinal flat mount was prepared. The vascular area ratio in FA and FITC-perfusion were measured with Angio tool® and the expression of each gene in the retina was analyzed by real-time PCR.

Results : In FA, vascular area ratio was 26% in WT without CRVO. After CRVO in WT, that was decreased but recovered from day 1 to 7 (day 1: 1.7%, day 3: 9.2%, day 7: 19%). Slightly increased in the AM-administration group (6.2%, 11%, 21 %), and decreased in the KO group (1.3%, 5.9%, 15%). FITC-perfused vascular area ratio was 53% without CRVO, and decreased to 30% after CRVO in WT. That was significantly increased in the AM-administration group and decreased in the KO group (AM-administration 45%, KO 13%, p<0.05 Tukey HSD, n=5−6 in each). CRVO-treatment elevated the expression of coagulation factor PAI-1, oxidative stress marker p67phox and leukocyte adhesion molecule ICAM-1 in both of the WT and KO groups, however it was much more prominent in the KO group (PAI-1: WT 20-fold, KO 157-fold, p67phox: WT 11-fold, KO 32-fold, ICAM-1: WT 18-fold, KO 43-fold). Contrary, elevation of PDGF-B was lower in the KO group (WT 2.9-fold, KO 2.1-fold). Angiopoietin 1/2 ratio was higher in the KO group without CRVO and lower after the treatment (1.6-fold and 0.77-fold, respectively).

Conclusions : AM promoted the reperfusion from CRVO. AM suppressed the expression of coagulation, oxidative stress and leukocyte adhesion-related molecules, whereas AM elevated PDGF-B, and dominated angiopoietin 1. AM is expected as a therapeutic candidate for CRVO through its vasoprotective effects.

This is an abstract that was submitted for the 2018 ARVO Annual Meeting, held in Honolulu, Hawaii, April 29 - May 3, 2018.