Improved Functionality of Grafted Eyes on Blind Tadpoles

Meghan Bialt-DeCelie – ’19

Caption: Researchers demonstrate the improvement of innervation between the central nervous system and a grafted eye on the tails of tadpoles with Zolmitriptan.

Caption: Researchers demonstrate the improvement of innervation between the central nervous system and a grafted eye on the tails of tadpoles with Zolmitriptan.

The major flaw faced by research in tissue regeneration is proper development of a nervous system as well as its functionality in the new host. Researchers led by Douglas J. Blackiston, Ph.D from Tufts University attempted to improve communication between a graft and the central nervous system of a host.

The researchers used the tadpoles of Xenopus laevis to observe the connection between sensory organs, like eyes and the central nervous system. In previous studies, they have shown that blind tadpoles with ectopic eyes growing on their tails could respond to visual stimuli; however, it was not a frequent accomplishment. In this study, they expose tadpoles with grafted eyes on their tails to 5-HT1B/D antagonist and show that it can more reliably induce innervation occurring between the ectopic structure with the nervous system.

The researchers grafted eyes on the tails of tadpoles using the eye primordia graft method when the tadpoles were embryos. Some of the embryos had grafts with tdTomato mRNA in order to visualize afferent neurons with fluorescence. They then exposed grafted tadpoles with 50µ Zolmitriptan which activates 5-HT1B/D. 40% of the treated individuals had innervation indicated by the fluorescent markers.

Showing innervation may suggest communication with grafted tissues, but it did not assess their functionality. Therefore, the researchers built an arena that had quadrants of red and blue light. A camera tracked the position of the tadpoles so if they entered a red quadrant, they would be shocked with a 1.2mA current. If blind tadpoles with innervated eyes on their tails showed preference for blue quadrants, it can suggest that the eye is able to function and the tadpole can distinguish between red and blue. Tadpoles of all testing groups were trained with this apparatus. It was then found that grafted, blind tadpoles exposed to 5-HT1B/D (29%) were significantly better at learning than blind and grafted tadpoles that were not exposed to 5-HT1B/D (11%).

Tissue regeneration has a promising future with a more reliable connection with the central nervous system. With the use of Zolmitriptan, the test used for functionality of grafted eyes was effective as a qualitative assay for the tadpole system and could be applied for related studies involving sensory tissue regeneration.

 

References:

  1. D. Blackiston, et. al., Serotonergic stimulation induces nerve growth and promotes visual learning via posterior eye grafts in a vertebrate model of induced sensory plasticity. Regenerative Medicine 2, (2017). doi:10.1038/s41536-017-0012-5
  2. Image retrieved from: https://commons.wikimedia.org/wiki/File:RanaTemporariaLarva2.jpg
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