title: Functional principal component analysis reveals discriminating categories of retinal pigment epithelial morphology in mice.
abstract: OBJECTIVE
  To determine whether multivariate, functional principal component analysis of the size and shape of retinal pigment epithelial (RPE) cell morphology allows discrimination of mouse RPE genotypes and age.
  
  
  METHODS
  Flatmounts of RPE sheets obtained from C57BL/6J (n = 50) and rd10 (n = 61) mice at postnatal days 30 to 720 were stained for zonula occludens-1 (ZO-1) and imaged with confocal microscopy. A total of 111 flatmounts were prepared. Twenty-one morphometric measurements were made on tiled, composite images of complete flatmounts, including cell location, area, and eccentricity, using automated image analysis software for quantitatively measuring cell phenotypes.
  
  
  RESULTS
  In young (≤61-day-old) C57BL/6J mice, the RPE morphology resembled a regular hexagonal array of cells of uniform size throughout the retina, except near the ciliary body, where the shapes of RPE resembled a soft network. Old (≥180-day-old) C57BL/6J eyes had a subpopulation of large cells. A clear disruption of the regular cell size and shape appeared in rd10 mutants. Aspect ratio and cell area gave rise to principal components that predictively classified mouse age and genotype.
  
  
  CONCLUSIONS
  Quantitative differences in the RPE sheet morphology allowed discrimination of rd10 from C57BL/6J strains despite the confounding effect of aging. This has implications for RPE sheet morphology as a potential early biomarker for diagnosis of eye disease and prognosis of the eye at early stages when disease is subtle. We conclude that an RPE cell's area and aspect ratio are very early quantitative indicators that predict progression to advanced RPE disease as manifested in rd10.
authors.affiliation: Department of Mathematics and Statistics, Georgia State University, Atlanta, Georgia.
authors.forename: Yi
authors.initials: Y
authors.lastname: Jiang
authors.forename: Xin
authors.initials: X
authors.lastname: Qi
authors.forename: Micah A
authors.initials: MA
authors.lastname: Chrenek
authors.forename: Christopher
authors.initials: C
authors.lastname: Gardner
authors.forename: Jeffrey H
authors.initials: JH
authors.lastname: Boatright
authors.forename: Hans E
authors.initials: HE
authors.lastname: Grossniklaus
authors.forename: John M
authors.initials: JM
authors.lastname: Nickerson
mesh_terms: D000375:Aging / Q000502:physiology; D000818:Animals; D005838:Genotype; D051379:Mice; D008810:Mice, Inbred C57BL; D018613:Microscopy, Confocal; D015999:Multivariate Analysis; D025341:Principal Component Analysis / Q000379:methods*; D055213:Retinal Pigment Epithelium / Q000033:anatomy & histology*
keywords: RPE; image analysis; retinal degeneration