Dr. Suleiman is using a Nobel-prize winning microscopy technique to look at the kidney cells injured in FSGS.
In 2014, the Nobel Prize for Chemistry went to a group of scientists who’ve created a new technique to change the scale at which we are able to see cell structures. In the same year, NephCure awarded a Young Investigator Award to Hani Suleiman, MD, PhD, an instructor at the Washington University School of Medicine, to use this new microscopy approach to look at kidney podocyte cells.
Recently, we spoke with Dr. Suleiman to hear about his work using this new microscopy approach, and how it might be used in the future to diagnose and potentially change how we approach creating new treatments for FSGS, Minimal Change Disease, and other diseases that cause Nephrotic Syndrome.
NKI: You received the Young Investigator Award from NephCure in 2014. Could you give us an overview on what you’ve been studying since receiving this grant?
Dr. Hani Suleiman: Glomerular diseases like Minimal Change Disease (MCD) and Focal Segmental Glomerulosclerosis (FSGS) are diseases of the podocyte, an important component of the kidney’s glomerular filtration barrier. Studying podocytes in living tissue has been limited due to the types of microscopy techniques that we use. The problem with seeing and understanding the podocyte and its changes is in its scale: important structures in the podocyte range from 200-300 nanometers. This resolution is below the limit of conventional microscopy techniques. Thus, we have been hindered from studying in detail the molecular changes that accompany podocyte injury and proteinuria.
Until the invention of super-resolution microscopy, the only way to view changes in podocytes after injury was to use electron microscopy techniques [electron microscopy was invented in the 1930s]. However, electron microscopy only allows us to see the structural changes in the podocyte. There is another technique that is capable, to some extent, to view the molecular patterns in podocyte structures after injury, but this technique has its own limitations. This is where super-resolution microscopy, a revolutionary new technique, comes in. We were the first people to adapt this technique to the kidney field.
In kidney diseases such as FSGS and MCD, podocytes go though a massive change in their shape as they lose their foot processes and form what is called foot process effacement. This is when the finger-like protrusions that you see in a normal podocyte change and basically disappear. This usually accompanies a leaky glomerular filtration barrier, as the patient starts spilling protein in the urine (proteinuria). Proteinuria, by itself, is an important indicator that the kidney is not functioning correctly as a filter.
Foot process effacement is a phenomenon that we see in almost all podocyte injuries, no matter how the injury starts: whether it’s immune-related, MCD or FSGS. All these diseases have foot process effacement and are accompanied with a loss of the glomerular filter.
In the paper that we just got accepted in the Journal of Clinical Investigation-Insight, we studied the molecular changes that accompany foot process effacement using super-resolution microscopy to try to understand the enigmatic phenomenon of foot process effacement and how foot process effacement is related to the cause of the injury. I think that, by mapping the earlier molecular changes in the injured podocytes, we can potentially intervene and stop this massive change and maintain the foot processes and the barrier.
This effort may be a good first step towards actually interfering with the pathways that we think interplay with this phenomenon [i.e., a first step towards treating proteinuria at a molecular level]. And for that, super-resolution will be an instrumental technique, since we are able to see the molecular changes of the cell on a nanoscale.
NKI: So podocyte foot process effacement is basically the fingerlike protrusions of the podocytes pulling up and away and leaving the podocyte with just the cell membrane. And without the fingerlike protrusions there, there’s nothing preventing the protein from leaking through the kidney?
Dr. Suleiman: As a response to injury, we think that foot process effacement is a survival mechanism for the podocytes. Podocyte number, like neurons, is a fixed number, and they must survive throughout life as they don’t reproduce. We can speculate that podocytes sense the dangers around them and respond by changing their shape in order to hold on to the basement membrane tightly as a precaution, in order to not fall into the urine. As I mentioned earlier, foot process effacement is usually accompanied with proteinuria, indicating that the retracted podocytes are unable to cover the whole basement membrane and prevent the protein leakage.
My work is to try to understand the earlier changes that cause the podocytes to go through this tremendous morphological change (i.e., foot process effacement), and how foot process effacement is related to the cause of the injury. I think that, by mapping the earlier molecular changes in the injured podocytes, we can potentially interfere and stop this massive change and maintain the foot processes and the barrier.
NKI: Are you mostly looking at mouse models right now?
Dr. Suleiman: In our recently accepted paper, we studied podocyte injury in three different mouse models. We included a small group of human tissue samples of FSGS, MCD and diabetic nephropathy in the study. We found that, similar to our mouse injury models, injured human podocytes show molecular changes that involve the motor molecules, myosin IIA.
As these results are in their early stages, I recently received a NEPTUNE (Nephrotic Syndrome Study Network) grant to study the biological significance of myosin IIA changes in human tissue samples. This study might allow us to find better diagnostic or prognostic tests for diseases such as MCD, FSGS and diabetic nephropathy.
NKI: So what you’re saying is that you think one day we might be able to use the super-resolution microscopy technique to diagnose patients?
Dr. Suleiman: Yes, I can see that the super-resolution microscopy will be instrumental in the future to diagnose and predict the outcome of diseases like glomerular diseases. The whole problem with imaging the podocyte in the past was the scale. Super-resolution, and the recently developed near super-resolution microscopy techniques, has the right scale to view the molecular changes in the podocytes.
NKI: Did the NKI Young Investigator Award have a big impact on what you have been able to do? Where were you at in your research when you received it?
Dr. Suleiman: Oh sure! That was my first grant ever. So for the last two years I have been relying on this grant to do my research. Of course, my previous mentor, Dr. Andrey Shaw, was highly supportive; I was still in his lab when I received the NKI award. This award has helped me publicize my work, refine my hypothesis and maintain my focus on the podocyte biology. It helped a lot. Thank you so much.
We were thrilled to learn more about Dr. Suleiman’s research. Check back at www.NephCure.org to stay updated on his work and other advances in the field. You can also view his most recent article on the super-resolution technique here. Thank you for your passion and commitment to learning about glomerular diseases, Dr. Suleiman!
Hani Suleiman, MD, PhD, is an Instructor in the Nephrology Division at the Washington University School of Medicine in St. Louis. Upon establishing the use of super-resolution microscopy, STORM in the kidney field, Dr. Suleiman has been focused on utilizing this technique to study various kidney diseases such as diabetic nephropathy, focal segmental glomerulosclerosis, and minimal change disease. In 2017, he received the Nephrotic Syndrome Study Network (NEPTUNE) Career Development Fellowship.
Dr. Suleiman has developed new ways to image the podocyte’s actin cytoskeleton in both animal models and human. These methods will allow us to ask new questions regarding how podocytes regulate their unique shape and maintain their function throughout life.