Acknowledging that live wild bats make poor research subjects a team from Tokyo University has grown bat organoids that reproduce intestines in vitro. A paper describing their bat organoid growth technique was published recently in the International Journal of Molecular Sciences.
Bats are the natural source of a raft of human pathogens, including Ebola, Marburg, Nipah, Hendra, SARS, MERS, and COVID-19. How bats can live with so many viruses without falling ill remains one of the great mysteries of virology. Yet because bats are wild animals, it is much more difficult to conduct reproducible investigations on bats than on mice for example. As a result, most experiments have had to take place on cell lines taken from bats rather than bats themselves or bat organs. “If this experimental blockage could be overcome, virus-bat relationships could be understood and lead to reduce human illness and death,” said Tsutomu Omatsu, senior author of the paper.
The team grew their organoids from cells from the intestine of a flying fox, the species Rousettus leschenaultia, also known as Rousette bats. They chose Rousette bats because they are thought to be a natural reservoir of the filovirus family of viruses, including the Ebola and Marburg viruses.
The researchers first had to find an optimum medium for the growth of bat intestine cells. They did this by attempting to culture organoids with nine different growth supplements. Three out of the nine achieved significantly higher cell growth and proliferation rates after seven days. In addition, the rousette bat intestinal organoids grown with these three supplements were long-lived, being able to maintain active proliferation for up to ten passages. Organoids that were cryopreserved could also grow normally once thawed.
To confirm that the organoid was mimicking the epithelial tissue of the bat’s intestine, the researchers deployed two techniques. First, they used transmission electron microscopy to investigate the cellular anatomy of the organoids. Second, they used immunofluorescence staining to look for molecular markers that indicate that the tissue under investigation comes from bat intestines. Together, these two techniques told the researchers that the organoids were indeed recreating the typical cellular components of rousette bat intestine tissues.