Exosome Subclass Analysis

Dr. Kiyotaka Shiba conducts research focusing on exosome and leads the Protein Engineering Division at the Cancer Institute of the Japanese Foundation for Cancer Research. Along with research scholars at the institute, Dr. Kazuya Iwai and Dr. Satoshi Yamamoto, from the Department of Oral Implantology at the Tokyo Dental College, Dr. Shiba discusses subclass analysis based on exosome density, as well as purification methods and cautions.


On Exosome Research Exosomes are interesting cells once believed existed relatively independently from each other are actually highly connected via exosomes(Fig. 1). There is a constant traffic of substances between cells via exosomes, and it seems that they communicate with each other. Even distinct living organisms exchange nucleic acids and proteins via exosomes, and I find myself seeing the world differently, as if all living things are connected by exosomes.

Chart 5 -Subclass Analysis

Fig. 1 Intercellular communication via exosomes

There's no doubt that a new era in medicine will be here one day, with exosomes at its center. This includes all areas: prevention, diagnosis and treatment.

With regard to the biological significance of exosomes, there has been a number of excellent research findings reported in the last two to three years that utilized clever genetic approaches. However, for the most part there is not yet an answer to this fundamental cell biology/biochemical question? - "What are exosomes?" In fact, there is no consensus on the definition of exosomes among exosome researchers, and confusion persists even at a basic level. Having said that, we are certain that "something entangled with the lipid bilayer" that is secreted by cells enables various biological activities of which we were once unaware.

How we purify exosomes is also related to how we define exosomes, and without establishing solid purification and quantitative methods, we will not be able to determine a good definition. Inherently, defining something as diverse as exosomes becomes baffling when people give serious thought to the matter. Considering that difficulties in scientific endeavors that target diverse groups are also present in cancer research, I believe this is an upcoming challenge in the field of biology. Our team is currently researching exosome purification and quantification methods, and our goal is to establish the basic technology for exosome research. Today we will introduce the exosome purification method we use in our division.