A Piece of the Puzzle: Saving Testes of Endangered Species

Kathryn Storey

It was a typical weekday afternoon at the University of Illinois in Champaign-Urbana until I received an e-mail that altered my career path forever. The message was from one of my mentors, Dr. Tom Jensen, offering me the Reproductive Sciences Summer Fellowship at the San Diego Zoo Institute for Conservation Research for 2017. Months passed with anticipation, and at the end of my junior year, it was finally time to move to California. With some help from my parents (thank you for driving across the country Dad, and for helping me pack Mom!), I landed in San Diego eager to begin this adventure. Being from the Midwest, I quickly realized California has very different ways of life (such as the speed limit only being a suggestion) and I felt like I was on a permanent vacation with beaches only miles away. 

On the first day of the fellowship, my mentors, Dr. Jensen and Patricia Byrne, leaped into action and explained my project. The overall idea was to determine a way to extend the life of testes after an animal has died. Specifically, we wanted to rescue the germline stem cells within the gonads, which are responsible for producing the sperm. 

The goal this summer was to develop a technique to keep post-mortem collected testes alive until the germline stem cells can be isolated and transferred to a host chicken. The host chicken will have chimeric testes that can produce sperm derived from the transferred donor germline stem cells. I worked with testes of both quail and exotic species to determine the conditions necessary to transplant and sustain these tissues within living chicken eggs. 

Essentially, the goal of my research was to find an answer to a small piece of this giant puzzle of saving endangered birds. 

For my project, we determined if the tissue is alive following transplantation by the presence of new blood vessels within the transplanted tissue. The majority of the avian testicular tissue contains very few blood vessels; therefore, I could easily determine if the transplantation was successful by the presence of new vessels arising from the embryonic membranes within the egg at the time of recovery. 

The size of the embryonic membrane of a chicken egg is large enough to transplant tissues onto by days 7 to 8 of incubation. We arranged our experiments around these critical days to maximize the survival of the chicken embryo and the transplanted testicular tissue. We then used various methods to promote angiogenesis, or the development of new blood vessels, within these transplanted tissues. 

Throughout this project, I learned how valuable chicken eggs are as a model for exotic species research projects. The domestic chicken is an abundant species; therefore, no harm comes to the population, also, the chicken embryo is very resilient and can endure the opening and closing of its shell. The immune system of a chicken embryo is not functional until half-way through the 21-day incubation period, making it the perfect host for this study since we transplant the tissue around day 7, and therefore do not need to suppress the immune system to avoid the rejection of “foreign” tissues. 

It is easy to see why creating a viable method for transplanting testes is crucial. The death of an endangered animal is unpredictable and can have a significant impact on the genetic diversity of its species. With the technique I helped to develop, scientists will be able to extract the testes from a deceased animal and maintain the germline stem cells inside an embryonic environment for future use, effectively extending its reproductive lifespan. One day, we could have chickens that produce kiwi sperm or that have gonads from critically endangered species transplanted onto their backs. How amazing is that? 

Science is all about trying something new and furthering our knowledge. That is what my project concentrated on, filling in a small piece of the giant puzzle that is the conservation of endangered species. 

This fellowship has shown me the work I want to devote my career life to. I will be forever thankful I had the opportunity to learn and grow as a future reproductive scientist with the most incredible research team in the world.