This summer I am lucky to return to the Stone Lab at the University of Washington. In the past, each year has brought new puzzles and new responsibilities, this year was no different. These first few days have already been eventful. I’ve visited the University of Washington’s electron microscope for the first time, attended a talk on cellular regeneration, and sat down with Dr. Stone and Dr. Rémy Pujol as they talked about the future direction of the lab and was invited to share my insights too.
Speaking of insights, let’s talk science and about what I’m doing in the lab:
Dr. Stone’s lab works on hair cell regeneration, not the hair cells you are probably thinking of, instead, she studies these guys, which are the inner ear hair cells. Hair cells in the inner ear are sensory receptors. They are responsible for your hearing and balance. After those cells die they don’t grow back in mammals (which means be careful about how much time you spend listening to loud music because the damage you do to those delicate inner ear hair cells won’t heal).
There is one known exception to the inner ear hair cells not growing back however: A few years ago Dr. Stone discovered that some type 2 hair cells grow back in mouse vestibular (balance) organs after damage. While this is a useful discovery, there are still two main problems. First there is still no hair cell regeneration in the cochlea (although I attended a talk on Friday where Dr. Neil talked about a transcription factor cocktail that is allowing him to grow hair cell-like cells from precursor cells). Second these newly regenerated hair cells don’t seem to be doing anything (the post damage mice do not respond to the visual ocular reflex test.)
The question that I have been working on since last summer is: Why is there no restoration of function in these regenerated hair cells? Knowing this, will help us restore function in human hair cells if we can regrow them, which could eventually lead to restoring human hearing.
So far, I started this summer off by re-acquainting myself with imaging programs. I use imaging programs like Huygens and Fiji (see pictures and descriptions below) to try to get an idea of what is happening to these cells after damage. For this I take confocal microscopy images and turn them into 3-d models like this:
(Huygens) Red, orange, and yellow are neurotransmitter from the hair cell, while green is receptor proteins on the nerves, blue is hair cell cytoplasm. Right now I am working on figuring out if the transmitter and receptors overlap (implying a synapse.)
As I work, the Huygens program spits out sheets of data that I am shifting through to find useful information about the position, shape and overlap of the labeled objects so I can find useful information about co-localization and figure out what is happening in the newly regenerated system which will tell me whether or not the nerves are hooking up to the hair cells properly. I am getting some interesting results but my process needs some fine tuning.
And this is another image of a 3d model I made in Fiji:
This is a 3d model of neurofiliment in a section of the vestibular system before damage. Images like this can be beautiful, but also a little daunting because for a while it looked like I might have had to trace out each neuron.
The highlight of the week was getting to spend time with Dr. Pujol on the electron microscope. Dr. Pujol is a brilliant, retired-only-in-France, physiologist who is working at the UW lab over the summer. I had seen images from the electron microscope before, but only as stills. Looking at the specimen under the electron microscope with Dr. Pujol was completely different. As he scrolled though, he showed me how to tell the difference between different types of cells, what certain organelles look like, and shared what he noticed about the physiology of regenerated cells. Shadowing him on the electron microscope gave me a new perspective on the physiology of hair cells, a perspective that I will be using in my imaging analysis. The next couple weeks I will be collaborating with Dr. Pujol to compare our results and try to figure out what is happening with the neuro-transmitter in regenerated hair cells. It will be very interesting to work with him and seeing what we can figure out this summer!