Dr. Elizabeth DiRenzo is an Associate Professor of Otolaryngology – Head & Neck Surgery at the Stanford University School of Medicine. She has a clinical degree in speech-language pathology, a PhD in laryngeal physiology from Purdue University, in addition to post-doctoral training from University of Wisconsin-Madison. She is currently a practicing speech-language pathologist in the Stanford Voice and Swallowing Center. Dr. DiRenzo’s research lab is most likely the only one in the world that specializes in laryngeal disease resulting from injury post cigarette and e-cigarette exposure.
To answer this question, I must start with the larynx. The larynx is a vital organ that is situated in between the upper and the lower respiratory tract. Unfortunately, it’s an often forgotten part of the airway, but it’s critical for breathing, coughing, swallowing and of course, in humans, producing your voice. Therefore, as you can imagine, issues with the larynx can have significant and major impacts on quality of life. In fact, issues with the larynx are not uncommon and affect millions of people in the United States and around the world annually.
Overall, my lab is interested in improving the prevention as well as management of all sorts of different types of diseases of the larynx. We are specifically interested in the role of the environment in the development of laryngeal diseases. Everything that we inhale passes through the larynx. Because of interesting flow dynamics, there is significant inhaled particle deposition in the larynx. Particles deposition patterns in the larynx are unique as compared to other parts of the airway.
We focus mostly on exposure to inhalation agents like cigarette smoke and e-cigarette vapor. We know cigarette smoke causes benign and malignant laryngeal disease. Consequently, cigarette smoke inhalation provides an elegant model that we can, in a very systematic way, study laryngeal disease progression. Specifically, we investigate what cellular and molecular switches occur to induce laryngeal tissue remodeling, then eventually disease development.
In terms of e-cigarettes, we still don’t fully understand how e-cigarettes impact the larynx and if use of these products contributes to disease development. If you look at the landscape of e-cigarette research, there has probably been about five papers published on e-cigarettes in the larynx while there have been hundreds of articles published on e-cigarettes and other parts of the airways. We have been working to develop models of laryngeal exposure that we can use to study the pathophysiological changes that occur in the larynx of e-cigarette users.
In general, we are one of the only labs in the world that study inhalation-based exposures and their role in the development of laryngeal injury and disease. This is truly an understudied area. The work we do is complementary to labs that research inhalation exposures in the lower airways and other parts of the upper airway. But the larynx is highly unique in terms of structure and function, and requires its own line of investigation.
Millions of people in the in the world have laryngeal diseases which impact critical functions such as breathing, coughing, swallowing and of course, voice production. What we’re trying to do is understand how these very common inhalation challenges cause disease. If we’re able to answer these questions, we may be able to better both prevent and reverse laryngeal injury and disease.
We purchased our first system in 2016. One of the best parts about SCIREQ is the reproducibility of your experiments. This has been a major issue with past research, at least in the larynx. When we are using SCIREQ, we know exactly what we’re getting in terms of puff timing, volume, etc. There are numerous quality control checks that we do to ensure that our exposures look similar from day-to-day, from week-to-week, and from experiment-to-experiment. We are confident our data is reliable and our results publishable because we’re able document how we’re doing experiments consistently.
Our initial inExpose experiments were about creating our models of cigarette smoke and e-cigarette-induced injury in the larynx. We started by doing a multiple experiments that varied in terms of how many weeks of exposure and how many hours per day.
We wanted to create a timeline of laryngeal injury that we see from acute through chronic inhalation exposures. One of the most prominent and early changes that we saw in response to cigarette smoke inhalation was hyperplasia or an increase in the number of basal cells in the vocal fold epithelum. These are the cells that replicate and turn over, to create the tissue. We are now using the inExpose to systematically explore the role of these specific cells in laryngeal regeneration, injury, and disease development. This work is funded by an R01 grant from the National Institutes of Health. We are hopeful these studies will lead to significant advances in terms of understanding the regenerative capacity of the laryngeal epithelium.
The software itself is incredibly useful in terms of how it launches an exposure profile, interfaces with the actual equipment, and provides monitoring it in real time. I also like that the profiles are easy to modify based on our experimental needs.
We primarily use a mouse experimental model. The mouse larynx, structurally, is actually very similar to the human larynx, despite being significantly smaller. Mice also vocalize. It’s a different type of vocalization than what humans do, but it does increase relevance.
In terms of doing inhalation-based challenges, mice are also established as a common model system. With the inExpose, we are able to expose 16 to 32 animals at one time which makes it flexible for us, especially given that many of our experiments last several month. This makes the best use of our time and increases productivity.
There can be a steep learning curve if you have not done this type of research before. But I would recommend reaching out to other laboratories that are doing this type of research, especially if you’re going to be using the SCIREQ equipment. When establishing our model, I personally contacted Dr. Crotty-Alexander’s group who’s been working with this equipment for a long time. They were able to provide great insights into these types of exposures and how they perform experiments and troubleshoot in their lab.
Also, I recommend using the tech support that is provided by SCIREQ! I have found that your team is truly here to help. Out of any companies I have worked with, SCIREQ provides some of the most amazing Technical Support that I’ve ever encountered. So, if you have questions, ask them. I also would say that from a practical standpoint, you have to take impeccable care of this equipment. Appropriately cleaning and servicing the equipment makes a huge difference in the longevity and the success of your experiments.
We are looking forward to starting some cell based experiments using the expoCube in vitro system. We’re also busy in the realm of e-cigarettes. We are seeing dramatic changes in the laryngeal mucosa in response to e-cigarette exposure. So, we’re really looking forward to exploring this avenue more and studying how e-cigarettes affect laryngeal disease development.
Electronic Cigarettes Activate The Heat Shock Response In Vascular Smooth Muscle In Atherosclerosis. Damiani, I., et al. (2022). Arteriosclerosis, Thrombosis, and Vascular Biology. 2022;42:A319
Effects of Electronic (E)-cigarette Vapor and Cigarette Smoke in Cultured Vocal Fold Fibroblasts. (2022). Martinez, J., et al. Laryngoscope, 133(1): 139-146
Modulation of mouse laryngeal inflammatory and immune cell responses by low and high doses of mainstream cigarette smoke. (2022). Easwaran, M., et al. Scientific Reports: 18667
Mainstream Cigarette Smoke Impacts the Mouse Vocal Fold Epithelium and Mucus Barrier. (2021). Erickson-DiRenzo, et al. Laryngoscope, 131(11): 2530-2539
