Retinal Pigment Epithelium Remodeling in Mouse Models of Retinitis Pigmentosa

Int J Mol Sci. 2021 May 20;22(10):5381. doi: 10.3390/ijms22105381.

Abstract

In retinitis pigmentosa (RP), one of many possible genetic mutations causes rod degeneration, followed by cone secondary death leading to blindness. Accumulating evidence indicates that rod death triggers multiple, non-cell-autonomous processes, which include oxidative stress and inflammation/immune responses, all contributing to cone demise. Inflammation relies on local microglia and recruitment of immune cells, reaching the retina through breakdowns of the inner blood retinal barrier (iBRB). Leakage in the inner retina vasculature suggests similarly altered outer BRB, formed by junctions between retinal pigment epithelium (RPE) cells, which are crucial for retinal homeostasis, immune response, and privilege. We investigated the RPE structural integrity in three models of RP (rd9, rd10, and Tvrm4 mice) by immunostaining for zonula occludens-1 (ZO-1), an essential regulatory component of tight junctions. Quantitative image analysis demonstrated discontinuities in ZO-1 profiles in all mutants, despite different degrees of photoreceptor loss. ZO-1 interruption zones corresponded to leakage of in vivo administered, fluorescent dextran through the choroid-RPE interface, demonstrating barrier dysfunction. Dexamethasone, administered to rd10 mice for rescuing cones, also rescued RPE structure. Thus, previously undetected, stereotyped abnormalities occur in the RPE of RP mice; pharmacological targeting of inflammation supports a feedback loop leading to simultaneous protection of cones and the RPE.

Keywords: Tvrm4 mouse; blood retinal barrier; dextranes; immunocytochemistry; rd10 mouse; rd9 mouse; retinal pigment epithelium; retinitis pigmentosa; zonula occludens.

MeSH terms

  • Animals
  • Dexamethasone / pharmacology
  • Disease Models, Animal
  • Evaluation Studies as Topic
  • Inflammation / metabolism
  • Inflammation / physiopathology
  • Mice
  • Mice, Inbred C57BL
  • Retina / drug effects
  • Retina / metabolism
  • Retina / physiopathology*
  • Retinal Cone Photoreceptor Cells / drug effects
  • Retinal Cone Photoreceptor Cells / metabolism
  • Retinal Pigment Epithelium / drug effects
  • Retinal Pigment Epithelium / metabolism
  • Retinal Pigment Epithelium / physiopathology*
  • Retinal Rod Photoreceptor Cells / drug effects
  • Retinal Rod Photoreceptor Cells / metabolism
  • Retinal Vessels / drug effects
  • Retinal Vessels / metabolism
  • Retinitis Pigmentosa / metabolism
  • Retinitis Pigmentosa / physiopathology*
  • Rhodopsin / metabolism
  • Tight Junctions / drug effects
  • Tight Junctions / metabolism
  • Zonula Occludens-1 Protein / metabolism

Substances

  • Zonula Occludens-1 Protein
  • Dexamethasone
  • Rhodopsin