Biomedical Engineering Pre-Grad Intern George Malik
For my IE Pre Grad Internship this semester, I had the privilege of working with graduate student Ryan Nagao as well as many other students in Dr. Christine Schmidt's biomedical engineering laboratory. This lab group works mainly in the tissue engineering arena where over the past decade or so, tremendous growth has occurred. What makes this area of research so fascinating is that it mainly deals with the artificial development of different forms of tissues that could potentially act as an alternative to organ transplantation.
Other lab groups around the world have been seeking the holy grail of tissue engineering which is to grow blood vessels to use in artificial tissues. This is a monumental task because so far, artificial growth of vasculature has utilized angiogenic growth factors that lead to leaky, hemorrhagic blood vessels. Without being able to growth healthy blood vessels for the created tissue, the artificial tissue constructs will be limited to mimicking tissue that does not need very much blood flow. Developing sufficient vasculature for the tissue construct is essential to the success because blood is responsible for the exchange of nutrients and waste. So if the blood flow in insufficient, areas of the tissue could form necrotic cores which are essentially dead tissue.
At the beginning of the semester, I had worked in this lab for just over a year and a half. But I had only worked with stem cells for about 3 or 4 months. So back in September, I was learning to master the techniques of cell culturing to better achieve our overall project goals. The stem cell portion of our project deals with differentiating Mesenchymal stem cells (MSCs) into endothelial cells (ECs). Endothelial cells are cells that form the tight lining inside of blood vessels. The use of MSCs is also significant because they can be taken from any future patient and used to create ECs specifically compatible with that patient. This will allow our tissue construct to be a personalized therapy for individual patients. MSCs are is important from a social context as well because they are stem cells that can be isolated from adults which makes them much more practical. These cells can then be injected into a decellularized tissue construct that we have developed in previous semesters. The cells repopulate the construct and allow the hollow vasculature from the native tissue to be utilized and adapted to the patient's own body.
In terms of initiating the differentiation of the MSCs into ECs, Dr. Laura Suggs' lab (also with the Biomedical Engineering department) has shown that culturing the MSCs in a polyethylene glycol gel fosters this transformation. The first step of this process was to unfreeze MSCs and culture them until we had enough cells to examine. I then combined these MSCs into a gel composed of thrombin, fibrinogen, and polyethylene glycol. The thrombin and fibrinogen are significant in the creation of the gel because all of these components are relatively liquids. The thrombin and fibrinogen, well known for their wound healing properties in the body in blood clotting, cause the solidification of the gel trapping in the MSCs. The polyethylene glycol is added to allow for some porosity and spacing within the gels. The MSCs culture in these gels for roughly one week.
After one week, I dissolve the gels and extract the differentiated cells. These cells, which resemble ECs are then plated and cultured for another week and imaged using fluorescence microscopy. The differentiated cells were first imaged using bright field microscopy to analyze the morphology of the former MSCs to see if they resembled ECs. After this hurdle was cleared, I stained the cells for Von Willebrand factor and CD31 which are both receptors that are commonly associated with ECs. All of these imaging techniques showed a significant correlation between the differentiated MSCs and ECs.
Within the last few weeks, our lab group has also started utilizing gold nanoparticles which are quickly becoming well-known for their use in cancer therapies. In our experiments, the nanoparticles are being used to essentially mark the differentiated MSCs so that when we inject them into the tissue scaffold, we can see how they move and whether they penetrate the tissue to a needed depth to make the construct a success. These nanoparticles are imaged real-time in the construct using photo acoustic imaging which is basically ultrasound imaging. This modality is important because it allows us to track the cells without having to slice up the construct and stain for them on individual slides. In the future, we will be analyzing the degree of perfusion flow used to enhance cellular attachment within the construct. It has been shown that the actin filaments of the cells better align when there is an applied flow that is similar to that of blood.
As I progressed through the semester, I was given more and more responsibilities. At the beginning, I was still working closely with Ryan to fine-tune my cell culturing skills and develop a better understanding of what we are investigating through our experiments. Then gradually, I would come into lab and complete tasks on my own and now I am at the point where I am teaching younger undergraduate students how to perform cell culturing and showing them the tricks that I have discovered.
More and more each day as a result of the IE Pre Grad Internship, I feel like my mindset becomes closer to that of a graduate student versus that of an undergraduate student. I no longer think in a "yes man" manner in lab but I am constantly thinking through experiments and trying to find new ways to make things more efficient or think of new ways to teach the other undergrads how tasks should be completed. I am thinking about the entire lab group instead of simply the tasks that I need to complete. The creativity that is needed as a graduate student in biomedical engineering is really starting to come out in my work and I have been very fortunate to be able to work in a lab that has been so conducive to my learning.
From my numerous experiences in lab, I have been able to see what the life of a graduate student is like on a day to day basis. It is a life very different from that of an undergraduate student required very different time management skills. In undergrad, you take many classes and assignments are given out to you. As a graduate student, you are almost giving yourself assignments because at this point, you become your own boss in a way. Learning about proposal and grant writing procedures has also been extremely helpful this semester and having the opportunity to learn how much administrative work must be completed for everyday lab experiments. Most importantly, I learned not to get frustrated when experiments do not turn out like you had hoped. There is always something to be learned from every experiment and one must adapt and progress next time. I will take all of these lessons with me into my pursuit of a graduate education in the medical sciences and biomedical engineering and hopefully begin my career with a leg up in terms of experience.