title: Xenopus laevis tadpoles can regenerate neural retina lost after physical excision but cannot regenerate photoreceptors lost through targeted ablation.
abstract: OBJECTIVE
  To determine whether the Xenopus laevis retina is capable of regenerating photoreceptor cells lost through apoptotic cell death in an inducible transgenic X. laevis model of retinitis pigmentosa (RP).
  
  
  METHODS
  Acute rod photoreceptor apoptosis was induced in transgenic X. laevis expressing drug-inducible caspase 9. We subsequently monitored the ability of the retina to regenerate lost photoreceptors in the absence of drug, and in combination with physical injury or ectopic supplementation of basic fibroblast growth factor (FGF2).
  
  
  RESULTS
  Direct activation of caspase 9 in rod photoreceptors resulted in the initiation of apoptosis and complete removal of rod photoreceptors within 4 days. Photoreceptors lost by apoptosis were not replaced over a 4-week recovery time frame. In contrast, physical disruption of rod-ablated retina was repaired by the end of a 3-week time frame, but did not result in rod photoreceptor regeneration other than at the site of injury. Furthermore, ectopic supplementation of FGF2 did not stimulate regeneration of photoreceptors lost by apoptosis. However, FGF2 supplementation increased the rate of regeneration of retina (including rod photoreceptors) in eyes from which retinal tissue was surgically removed.
  
  
  CONCLUSIONS
  In the X. laevis retina, rod photoreceptors that undergo drug-induced caspase-9-mediated apoptosis are permanently lost and do not regenerate. In contrast, the neural retina (including rod photoreceptors) can regenerate in injured or retinectomized eyes, and this regeneration is promoted by supplementation with FGF2. However, FGF2 does not promote regeneration of rod photoreceptors that are selectively lost by apoptosis.
authors: Department of Ophthalmology and Visual Sciences and Centre for Macular Research, University of British Columbia, Vancouver, British Columbia, Canada.
authors: Damian C
authors: DC
authors: Lee
authors: Lisa M
authors: LM
authors: Hamm
authors: Orson L
authors: OL
authors: Moritz
mesh_terms: D000818:Animals; D030801:Animals, Genetically Modified; D017209:Apoptosis; D015153:Blotting, Western; D004195:Disease Models, Animal; D007150:Immunohistochemistry; D007814:Larva; D018613:Microscopy, Confocal; D008866:Microsurgery; D012038:Regeneration; D012160:Retina / Q000502:physiology* / Q000601:surgery; D017949:Retinal Cone Photoreceptor Cells / Q000502:physiology*; D017948:Retinal Rod Photoreceptor Cells / Q000502:physiology*; D012174:Retinitis Pigmentosa / Q000235:genetics / Q000473:pathology*; D014982:Xenopus laevis / Q000235:genetics