For years David Unnersjö-Jess dreamed of being a rock star. As he got older his passion for music and guitar waned, so when it came time for university he decided to study engineering physics at KTH Royal Institute of Technology in Stockholm. The Bachelor’s led to a Master’s and then a PhD. Before he was offered the PhD position, it wasn’t something he had really thought of pursuing. “But since my master’s dissertation in biological physics was so fun and exciting I figured why not work on this full-time,” says David. “I have always been curious about finding out how things work and that’s exactly what you get to do when you do research.” He is currently putting his curiosity to good use as a PhD student in cellular biophysics, where his research is mostly focused on the kidney.
David develops new techniques to prepare kidney tissue for microscopy. He is focused on optimizing kidney tissue samples so they are easier to image using light microscopy. One of the biggest problems with looking at kidney tissue under a light microscope is that the refractive index is different throughout the tissue. This means that light rays will be distorted as they pass through the tissue, blurring the image under a microscope. David’s lab has applied and optimized a preparation technique to make the refractive index more consistent throughout the kidney by making kidney “transparent”.
To do this, they first remove the lipids from the tissue. They put the sample in a hydrogel so that it will stay together once the lipids are removed. All the biomolecules, such as proteins and DNA, get attached to the hydrogel but the lipids don’t making it possible to remove them with a strong detergent. Then they immerse the sample in a high-refractive index mounting solution leaving them with an almost completely transparent piece of tissue. David and his coworkers have used this technique successfully in mouse, rat, and human kidney tissue. The majority of their experiments use mouse and rat tissue simply because they are more accessible.
Once the kidney tissue is transparent, David and his colleagues use a super high-resolution STED microscope to view teeny, tiny, nanometer-scale structures in the kidney that researchers have never observed before. On its own the STED microscope, while 10 times more powerful than a traditional light microscope, isn’t powerful enough to see the smallest parts of the kidney. But once the tissue is transparent, it’s easier to image. “The novel thing about our research is the combination of optical clearing (making tissue transparent) with super-resolution STED microscopy to be able to view things in the kidney that have never been observed before,” says David.
Now that David and his colleagues have developed a technique to view the smallest structures of the kidney, they are collaborating with kidney experts to try to answer questions about kidney disease. Through studying the localization of proteins in the kidney they can learn which ones are essential for normal organ function. It’s possible for them to introduce a mutation that alters the localization of a certain protein and study what impact it has on kidney function. They can also delete a protein and study how this affects the localizations of other proteins in the kidney. Sometimes they use mice as a model for human kidney disease in these experiments because their genomes can easily be modified to induce kidney disease. Using their transparency and STED microscopy technique, David and his colleagues can see what effect these protein deletions have on the smallest elements of the kidney. David hopes that these methods can improve the accuracy of diagnosing kidney disease by giving pathologists another diagnosis tool and in the long run offer insights into how to treat and prevent kidney disease.