Throughout non-mammilian vertebrates, the regeneration and recovery of hair cells that have sensory implications following damage has been observed; whereas mammalian hair cells tremendously lack this unique capability. Zebrafish, a non-mammalian vertebrate, is inherently capable of regenerating sensory hair cells, which exist within the organism’s ear as well as in its sensory lateral line system. Comprehension of the molecular basis of this unique capability has potential to define therapy for hearing loss in human beings. The focal point of our work and experimentation is the interneuromast chain of the lateral line system of the Zebrafish.
The lateral line is a mechanosensory system comprised of small sensory patches called neuromasts that are linked together by an interneuromast chain. Each sensory neuromast possesses hair cells extending their stereocillia beyond the epidermis where they may be deflected by water from which they can transduce external stimuli. These neuromast cells are directly supported by cells located beneath them called inner support cells as well as additional cells called mantle cells forming a ring around them. The mantle cells are particularly significant in that they may be involved in neuromast regeneration, and can be defined as multipotent progenitor cells of the lateral line system. Interestingly enough, mantle cells of the neuromasts at the tail-end of Zebrafish have been demonstrated to enter the cell cycle in their contribution to regeneration following amputation of the tail.
In the First component of our experimentation, we set out to characterize the regenerative capacity of the interneuromast chain through the implementation of Confocal Microscopy. In the transgenic line of Zebrafish that we are using in this experiment, the interneuromast chain is reported upon by Green fluorescent protein. Being that the interneuromast chain is labeled with Green fluorescent protein, we can visualize it with ease under the Confocal Microscope. In addition to its purposes in effectually visualizing the interneuromast chain, we have been able to utilize the Confocal Microscope to conduct our ablation experiments. We have implemented the DAPI Laser of the Microscope to completely ablate the interneuromast chain; and the DAPI laser is set at a high energy wavelength of 405 nm at a laser power of 75%. Additionally, we allow the laser to annihilate the chain for exactly 60 seconds during each experimental trial.
The controls for our DAPI laser were determined over the course of several different experimental trials in which we previously struggled to optimize our controls. Following our ablations of the interneuromast chain, we have further conducted 24 hour Time Lapse experiments in an effort to capture the events following the interneuromast chain ablation. We have successfully captured 3 separate movies that portray complete interneuromast chain regeneration, and were able to characterize the gaps we created in terms of microns.
Throughout the course of September and into October, we encountered some adversity with regards to the mating behaviors of our Zebrafish in which there was absolutely no breeding. However, our luck turned around this past week and we had successful breeding. We were able to conduct an ablation experiment, and produced what appears to be the most impressive gap in the interneuromast chain created following ablation thus far. We are optimistic and excited to see what our 24 hour time lapse experiment reveals later this week.