Abstract
Purpose::
The goal of this study is to understand the parameters of retinal regeneration following axotomy in the African clawed frog, Xenopus laevis. Unlike mammalian retina, many amphibians can regenerate retina, at least prior to metamorphosis. Retina can regenerate from at least three different sources, including the ciliary marginal zone (CMZ), the pigmented epithelium, and the retinal Mueller glial cells. Evidence from many studies indicates that the type of injury may dictate the source of retinal regeneration.
Methods::
Tadpoles were obtained from Xenopus Express and grown in Holtfreter’s pond water. Tadpoles from Nieuwkoop and Faber stages 53 and 57 were axotomized by removing a small portion of the optic nerve to prevent re-growth of the axons. Generation of cell type-specific markers was analyzed using indirect immunofluorescence.
Results::
Tadpoles axotomized at stage 53 (pre- metamorphosis) and 57 (post-metamorphosis) were analyzed using cell type-specific markers and histological stains. Axotomized tadpoles were compared to sham-operated and un-operated controls 1, 2, 4, 7, 14, and 30 days post-axotomy. At stage 53, the fundus of the retinae began to degenerate by day 2 axotomized tadpoles. Degeneration appeared to encompass only the fundus of the retina, while peripheral regions appeared to remain intact. Regenerating retina was visible by day 4 and appeared to be complete by 7 days post axotomy. Retinae were also able to regenerate following axotomy at stage 57, and did so in a time-frame similar to those axotomized at stage 53. However, two differences were apparent between the stage 53 and 57 axotomized retinae; 1) the entire stage 57 retinae degenerated, and 2) regenerated stage 57 retinae were smaller. No differences were noted between sham-operated and un-operated controls.
Conclusions::
Both pre- and post-metamorphic retinae are capable of regeneration in Xenopus laevis.
Keywords: regeneration • retina • retinal degenerations: cell biology