The role of IP-10 in RPE degeneration during AMD progression

Abstract

Purpose : Interferon gamma-induced protein 10 (IP-10/CXCL10) is a pro-inflammatory cytokine that is upregulated in the retinal pigment epithelium (RPE) during progression of age-related macular degeneration (AMD). Previous data suggest significantly enhanced expression of IP-10 after RPE treatment with double-stranded RNA (dsRNA) which is also increased in eyes with AMD. In this study, we set out to determine whether this cytokine is critical to dsRNA mediated RPE degeneration in a mouse model of Ip10 deficiency as well as phenotypic features and cytokine expression in the aged mouse.

Methods : Ip10 deficient mice (Jackson Labs, C57BL/6J background, young (4-8 weeks) and aged (12-18 months) were compared to age-matched Wild type C57BL/6J mice (N=6-8). Intravitreous injections (PBS, poly I:C or Alu RNA; both 1μg) were performed in Wild-type and Ip10-/- mice (N=4-6, 4-6 weeks) and analyzed at day 7. Fundus photography and autofluorescence were obtained using Topcon TRC-50IX; electroretinograms (ERG; Espion) were obtained under scotopic conditions. RPE/choroid flatmounts were prepared and immuno-stained for the tight junction protein, zona occludens-1 (ZO-1). RPE levels of inflammatory cytokines in the aging model were analyzed via multiplex bead arrays (Luminex, N=3). The Ip10-/- mouse strain was sequenced for spontaneous rd8 mutations (N=3).

Results : Ip10-/- mice are not protected from dsRNA induced RPE degeneration. Funduscopy, autofluorescent imaging, and posterior segment OCT revealed widespread moderate retinal degeneration in the aged Ip10-/- mice compared to age-matched controls. Protein studies revealed significantly decreased levels of multiple pro-inflammatory cytokines in the RPE of aged Ip10-/- mice. Sequencing for rd8 mutations was positive.

Conclusions : A mouse model of Ip10 deficiency was not protected from dsRNA induced RPE degeneration suggesting that this cytokine is not critical during AMD progression. Aged Ip10-/- mice developed spontaneous retinal degeneration compared to age matched Wild-type BLC57/6J mice. We discovered that this strain harbors a previously unreported rd8 mutation which may account for this abnormal retinal phenotype.

This is an abstract that was submitted for the 2016 ARVO Annual Meeting, held in Seattle, Wash., May 1-5, 2016.