My name is Shruti Singh, and I am a rising senior at the University of Texas at Austin. I am majoring in Human Biology with a concentration in immunity and pathogenesis. I was introduced to research through a program called the Freshman Research Initiative, which allows college freshman at the University of Texas at Austin to perform independent research. I started working in Dr. Andrew Ellington’s Aptamer lab, designing aptamers for specific targets. Aptamers are nucleic acids (RNA or DNA) that can bind to proteins, small molecules, or any other target, with applications in therapeutics, diagnostics, and drug delivery.
The target for aptamer selection in my first research project was a protein called transferrin, which is involved in the transport of ferric iron to rapidly proliferating cells of the body. Tumor cells have been shown to express more transferrin receptors than normal cells, making transferrin a great candidate for drug development in cancer research. I planned to select an aptamer against transferrin and use it for cytotoxic drug delivery to cancer cells. After multiple trials, I observed no significant binding between the target and the nucleic acid. Nevertheless, the results from this project will be used to optimize the selection of future aptamers targeted against transferrin.
In my next project, I helped develop an educational kit that can be utilized in high school classrooms to demonstrate important concepts in evolutionary theory. This kit uses biochemistry and molecular biology techniques, including a fluorescence assay for visualization, to allow students to observe the evolution of a catalytically active ribozyme ligase. A ribozyme is an RNA molecule with catalytic activity similar to proteins, and a ribozyme ligase is a ribozyme that can attach itself to another RNA molecule. In this kit, evolutionary pressure is applied to a T500 ribozyme ligase population to select for a catalytically faster ribozyme . For this project, I tested new iterations of the kit and troubleshot problems that I encountered, so the kit could be distributed to classrooms where it could be used as a tool for teaching evolution.
After watching a family member undergo the ordeal of a kidney transplant, I understand the importance of and the necessity for new therapeutic ideas in the field of organ function renewal. That made me very interested in the field of regenerative medicine. As a SENS Summer Scholar, I hope to both learn and contribute to organ regeneration and renewal research.
Regeneration of a part of Pig Thymus ex vivo using Mouse Thymic Epithelial and Bone Marrow Cells
This summer, I am working on a thymus regeneration project in Dr. John Jackson’s lab at the Wake Forest Institute for Regenerative Medicine. The thymus is a specialized organ in the immune system, and it is involved in the maturation of T-cells. T-cells recognize and attack foreign substances, called antigens, thus protecting the body from developing infections. The thymus consists of two lobes, which can further be divided into two regions – a cortex and a medulla. In the cortex, positive selection of a T-cell’s major histocompatibility complex (MHC) takes place. MHCs are cell surface proteins that present antigen to T-cells. A negative selection of T-cells occurs in the medulla, where the T-cells that recognize self-antigens are destroyed, so the T-cells won’t attack the body’s own cells and tissues.
In old age, the thymus starts to lose its functional abilities, rendering the immune system ineffective. One approach to restore the immune system in aged individuals is the regeneration of the thymus. Thymic tissue regeneration and T-cell maturation also have application in the treatment of autoimmune diseases, immunodeficiencies, and transplant rejection. During the summer, I will work on one part of this larger project.
Figure 1. An example of decellularized thymus section1.
The H&E staining of a section of decellularized pig thymus scaffold reveals that the structure is clear of cellular and nuclear material.
I plan to decellularize a small piece of pig thymus (Figure 1), which entails getting rid of all the cells in the thymus, leaving behind the extracellular structure called a scaffold. After decellularizing the thymus, I will reseed the thymus scaffold with thymus epithelial cells and bone marrow cells from mice, providing a 3-D environment to the cells that resembles their natural environment in the body. I will then analyze the proliferation of these cells in the scaffold and look for the production of mature T-cells. The success of this project will be an important step forward towards the overarching goal of whole thymus regeneration.
I plan to return to the Ellington lab in the fall of 2014 and continue my work on the high school evolution demonstration kit. I hope to finish troubleshooting the problems being encountered and successfully replicate the experiment multiple times, so that the kit can be ready for distribution. I plan to graduate from the University of Texas in December 2014, after which I hope to attend medical school. I also hope to continue performing medically relevant research in medical school.
(1) Ryu, S.W., Mondal, A.K., Kim, N., Bullock, D., Lee, S.J., Atala, A., Yoo, J.J., Jackson, J.D. “Characterization of thymus scaffolds for engineering thymus tissue.” Wake Forest Institute for Regenerative Medicine, Winston-Salem, NC.