Tag Archives: gastrointestinal physiology

Stem Cell Summer Research

Research Project

Throughout our lives we accumulate damage naturally in our day-to-day activities. Thankfully, our bodies have an incredible potential for repair. Damaged tissues might follow a sunny day at the beach without sunscreen or the micro-tears in muscles resulting from a hard workout, are repaired by our bodies via the orchestration of numerous cellular processes. In response to tissue damage, various proteins will signal to specific cells in the damaged tissue that have the potential to differentiate and repopulate damaged tissue, inducing a regenerative response. These specific cells are known as stem cells .

My research this summer focused on a protein complex that has reported roles during aging and in mediating repair in particular tissues: mTORC1. In muscle, mTORC1 has been shown to be crucial to the activation of muscle stem cells, which are normally dormant, so that they may repopulate the damaged muscle by replacing injured cells with new, healthy cells. Although the role of mTORC1 in tissue regeneration is well understood in muscle, its role during repair is unclear within many other organs, particularly the intestine. The inner lining of the intestine, known as the intestinal epithelium, experiences tremendous damage on a daily basis, in part, as a result of the mechanical stress to the intestinal cells from the passage of food. As such, the intestinal epithelium is one of the most proliferative tissues in the human body, having the capacity to turnover every 5-7 days. My research this summer aimed to understand the role mTORC1 in repairing the intestinal epithelium after injury, and also to understand how this role may differ from its activity in an uninjured context, during homeostasis. We hope that the results from this work will help us better understand the intestinal regenerative process in order to someday have the capability to pharmacologically enhance regeneration in injured individuals, or prevent it, in conditions such as cancer where tissue grows excessively quickly.

Realities of Research

One of the aims of my research project was to focus on the role of mTORC1 during homeostasis. I hypothesized that if the activity of mTORC1 was inhibited, stem cell activity in the intestinal epithelium would be impaired. After genetically manipulating mice so that mTORC1 activity was only depleted in the intestine, we saw that mice lost a dramatic amount of weight and became sickly. We also expected a change on the cellular level. For instance, we anticipated changes in the number of cells actively dividing in the intestinal epithelium as well as changes in the architecture of intestinal epithelial cells. In order to better visualize the number of cells actively proliferating within the intestinal epithelium, I used a cell staining technique called Edu staining which allowed me to visualize each cell undergoing division. Once imaged, I could then quantify the exact number of cells undergoing division within a set amount of time and compare the number of proliferating cells in mice in which mTORC1 was depleted, compared to control mice with normal mTORC1 activity . The Edu staining showed a decrease in the number of cells proliferating in mice depleted of mTORC1 activity, further supporting my hypothesis. In order to further characterize the changes that occur after obstruction of mTORC1 activity, I plan to determine whether intestinal stem cell number is affected following genetic mTORC1 depletion. I also plan to analyze the general structure of the epithelial tissue using a staining technique called H&E staining and quantify the number of cells undergoing programed cell death using cleaved caspase 3 staining.

Life of a Scientist

This past summer, I’ve learned a lot about what it means to do research. Primarily, I’ve discovered the necessity of having keen attention to detail. Prior to working in Dr. Samuelson’s lab, I hadn’t realized how many steps need to go correctly in order to obtain data from an experiment. For instance, to complete a Western Blot, which is an experimental technique used to separate and identify a specific protein from a sample containing hundreds or even thousands of proteins, each step in the process must be executed with acute accuracy and precision. First, the mice had to be treated with the proper experimental treatment. Following the harvesting of the tissue, the protein within had to be extracted and quantified extremely accurately. Finally, the Western Blot could be run, which also has potential for error. If even a single step within the entire time intensive process was completed inaccurately or improperly, the Western Blot likely wouldn’t work and the entire process would need to be redone.

As I near the end of my summer in Dr. Samuelson’s lab, one of my biggest takeaways from working in the lab is that a scientist is never done learning. Sitting in on lab meetings with a team of experienced scientists and PhD students has shown me that even experts in certain fields don’t have the answers to every question. During my ten weeks in the lab, each week was entirely different. While there were several core skills that I learned and expanded upon through practice throughout the whole summer, each week also came with new scientific techniques and new ways of thinking and approaching problems. This constant exposure to new information and lifelong learning is what excites me as a scientist.

Yasmine Abushukur is a senior at the University of Michigan studying both French and Bimolecular Science. This summer, she worked in Dr. Linda Samuelson’s lab thanks to funding from the APS Undergraduate Summer Research Fellowship. This upcoming school year, she plans to continue working under Dr. Samuelson’s guidance, studying gastrointestinal physiology. After graduation, she plans pursue a career as a physician-researcher.