title: Ultrastructural analysis of the pigment dispersion syndrome in DBA/2J mice.
abstract: OBJECTIVE
  To characterise ocular pigment abnormalities associated with iris atrophy in DBA/2J mice as a model for human pigment dispersion syndrome.
  
  
  METHODS
  Immunohistochemistry, electron and light microscopy were performed to examine the eyes of DBA/2J mice ranging in age from 2.5 to 18 months old. The focus of our study was the description of the ultrastructural modifications in the irides of DBA/2J mice.
  
  
  RESULTS
  The DBA/2J mice presented modifications in the melanosomes in all the pigmented parts of the eye, including the retinal pigment epithelial cells and choroidal melanocytes of the ciliary pigment epithelium. The extracellular matrix of the iris stroma disappeared with ageing. Pigmented cells detached from the iris and migrated into the trabecular meshwork exclusively on the anterior iris surface. These cells were identified as macrophages by immunohistochemistry and electron microscopy. There was no evidence that melanocytes or iris pigment epithelial cells migrated into the trabecular meshwork, but they became more and more depigmented. The aqueous outflow was blocked by pigment-laden cells, but not by cellular debris or melanosomes. No substantial amount of extracellular melanosomes was observed.
  
  
  CONCLUSIONS
  The morphology of melanosomes is aberrant in all pigment cells in the eyes of DBA/2J mice. We conclude that the disease process begins with the transfer of both immature melanosomes from the iris pigment epithelium (IPE) and melanocytes to macrophages, which subsequently migrate into the trabecular meshwork. Accumulating macrophages cause a blockade of the chamber angle. As the disease progresses, the IPE, melanocytes and iris stroma, including blood vessels, disappear, leading to iris atrophy. It is speculated that the loss of these pigment cells is partly caused by reduction of the iris stroma.
authors.affiliation: Section of Experimental Vitreoretinal Surgery, Centre for Ophthalmology, Institute for Ophthalmic Research, Tübingen, Germany.
authors.forename: Mareike
authors.initials: M
authors.lastname: Schraermeyer
authors.forename: Sven
authors.initials: S
authors.lastname: Schnichels
authors.forename: Sylvie
authors.initials: S
authors.lastname: Julien
authors.forename: Peter
authors.initials: P
authors.lastname: Heiduschka
authors.forename: Karl-Ulrich
authors.initials: KU
authors.lastname: Bartz-Schmidt
authors.forename: Ulrich
authors.initials: U
authors.lastname: Schraermeyer
mesh_terms: D000375:Aging; D000818:Animals; D001284:Atrophy; D002465:Cell Movement; D002924:Ciliary Body / Q000648:ultrastructure; D004195:Disease Models, Animal; D017889:Exfoliation Syndrome / Q000473:pathology*; D005109:Extracellular Matrix / Q000648:ultrastructure; D017496:Hypopigmentation / Q000473:pathology; D007498:Iris / Q000473:pathology*; D008264:Macrophages / Q000648:ultrastructure*; D020460:Melanosomes / Q000648:ultrastructure*; D051379:Mice; D008810:Mice, Inbred C57BL; D008811:Mice, Inbred DBA; D010857:Pigment Epithelium of Eye / Q000648:ultrastructure*; D014129:Trabecular Meshwork / Q000648:ultrastructure