Intravitreal Triamcinolone Acetonide Inhibits Breakdown of the Blood-Retinal Barrier Through Differential Regulation of VEGF-A and Its Receptors in Early Diabetic Rat Retinas

  1. Mark C. Gillies1
  1. 1Retinal Therapeutic Research Group, Save Sight Institute, Department of Clinical Ophthalmology, University of Sydney, Sydney, Australia;
  2. 2Beijing Institute of Ophthalmology, Beijing Tongren Eye Center, Beijing Tongren Hospital, Capital Medical University, Beijing, China;
  3. 3Department of Pathology, University of Sydney, Sydney, Australia;
  4. 4Molecular Biology Facility, Bosch Institute, University of Sydney, Sydney, Australia.
  1. Address correspondence and reprint requests to Dr. Xinyuan Zhang, Save Sight Institute, Department of Clinical Ophthalmology, Level 2, South Block, Sydney Eye Hospital, Macquarie St, Sydney NSW 2000, Australia. E-mail: xzhang{at}eye.usyd.edu.au.

Abstract

OBJECTIVE To elucidate the mechanism of the unique beneficial effect of intravitreal steroid therapy on diabetic macular edema, we investigated the effect of locally administered triamcinolone acetonide (TA) on the expression of vascular endothelial growth factor (VEGF)-A and its receptors in retinas of rats with streptozotocin (STZ)-induced diabetes. We then correlated the expression of these proteins with breakdown of the blood-retinal barrier (BRB).

RESEARCH DESIGN AND METHODS Thirty-two eyes of 16 diabetic and nondiabetic rats were divided into four groups. TA was injected into the vitreous of the right eye, and saline was injected into the left eye (control) 3.5 weeks after induction of diabetes. Retinas were harvested 48 h following treatment. mRNA and protein expression of VEGF-A, VEGF-A receptor 1 (fms-like tyrosine kinase [FLT]-1), and VEGF-A receptor 2 (fetal liver kinase [FLK]-1) were determined by real-time RT-PCR and immunohistochemistry. BRB permeability was quantitated by measuring extravasated endogenous albumin and retinal thickness.

RESULTS Diabetes-induced retinal thickness and albumin extravasation were significantly reduced in TA-treated diabetic retinas to a level similar to that in sham-treated nondiabetic eyes. A close correlation between albumin leakage and increased expression of both Vegf-a and Flk-1 was noted in the diabetic retinas. TA downregulated the expression of Vegf-a and Flk-1 but upregulated the expression of Flt-1. TA did not alter the expression of these genes in nondiabetic retinas.

CONCLUSIONS Intravitreal injection of TA stabilizes the BRB in association with regulation of Vegf-a, Flk-1, and Flt-1 expression in retinas in the early stages of diabetes.

Footnotes

  • M.C.G. is included as an inventor on patents relating to the formulation of triamcinolone for ocular use and its use for the treatment of retinal neovascularization, but not macular edema. M.C.G. is an advisor and receives research support from Allergan (Posurdex).

  • The costs of publication of this article were defrayed in part by the payment of page charges. This article must therefore be hereby marked “advertisement” in accordance with 18 U.S.C. Section 1734 solely to indicate this fact.

  • AMD
    age-related macular degeneration
    AEC
    3-amino-9-ethylcarbazole chromogen
    BRB
    blood-retinal barrier
    DAB
    diaminobenzidine
    DR
    diabetic retinopathy
    FLK
    fetal liver kinase
    FLT
    fms-like tyrosine kinase
    IAU
    image arbitrary unit
    IPP
    Image-Pro Plus
    IVTA
    intravitreal injection of triamcinolone acetonide
    PFA
    paraformaldehyde
    qPCR
    quantitative polymerase chain reaction
    REST
    relative expression software tool
    STZ
    streptozotocin
    TA
    triamcinolone acetonide
    TBS
    Tris-buffered saline
    UDG
    uracil-DNA glycosylase
    VEGF
    vascular endothelial growth factor.

  • Received July 16, 2007.
  • Accepted December 19, 2007.
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  1. Diabetes vol. 57 no. 4 1026-1033
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