Virtual journey through the “caterpillar of research”

Video: © Fraunhofer IME, Dr. Anton Windfelder

The inside of a special model animal used in medical research can now be explored interactively and with 3D glasses: Using CT scan data, German scientists have developed a virtual representation of the anatomy of the tobacco hornworm caterpillar. This has already led to new discoveries in the digestive tract of the larvae. The system can now benefit research into human intestinal diseases such as Crohn’s disease, as well as being used in university teaching, say the scientists.

Scrolling through the body interactively on the screen or with 3D glasses: thanks to virtual reality technology, this is already possible in the case of the human body. The particularly catchy visualization of anatomical structures can provide physicians and researchers with important information. So far, however, such a representation has not been possible in the case of a special model organism: the caterpillars of the tobacco hornworm (Manduca sexta), which can be up to eight centimeters long, are used primarily in research into human intestinal diseases such as Crohn’s disease. “The intestines of mammals and insects are comparable in many areas. This is especially true for the innate immune system. If we understand chronic inflammatory bowel diseases in tobacco hornworms, this can provide important information for human medicine,” explains first author Anton Windfelder from the Justus Liebig University in Giessen.

From CT scans to 3D models

For this purpose, the anatomy of the digestive tract of the model animal should of course be known in as much detail as possible. In order to provide more insights, Windfelder and his colleagues first obtained imaging data from inside the caterpillars using micro-computed tomography technology. A clinical contrast medium was used, which enabled a high-resolution analysis of the structures. The interdisciplinary research team was then able to use the information to develop a three-dimensional model of the internal anatomy of the larvae. In addition, the research data could be processed for interactive visualization in virtual reality.

As it turned out, the effort was worth it: the team used the results to discover previously unknown anatomical structures in the intestines of the insect larvae. This involves a goiter structure, several appendixes and other special features. “We are surprised by the complex hexagonal fold pattern – it runs through the entire midgut and hindgut and may be related to water absorption in the hindgut. With traditional light microscopy, this was not possible until now,” says co-author Andreas Vilcinskas from the Fraunhofer Institute for Molecular Biology and Applied Ecology in Giessen. Based on the data, it was also possible for the first time to precisely calculate the intestinal volume of the tobacco hornworm caterpillars. In these very large insect larvae, it is around 1.4 milliliters, which roughly corresponds to the intestinal volume of a mouse.

Potential for biology, medicine and teaching

This result, in turn, is important for medical research on the caterpillars, because the scientists say the dosages of certain substances can be better adjusted with the information. “We can, for example, research new drugs for chronic intestinal diseases such as Crohn’s disease,” says co-author Gabriele Krombach from the Clinic for Diagnostic and Interventional Radiology in Giessen.

Virtual journey through the “caterpillar of research”
The interior of the tobacco hornworm larva can now be explored in three dimensions using virtual reality glasses. © Fraunhofer IME / Kim Weigand

In order to investigate the effectiveness on the model animal, inflammations in the intestinal wall can be made visible using contrast media and then recorded using computed tomography. The researchers explain that the new insights and technical possibilities can now help to better plan such studies and evaluate the results.

Finally, the team emphasizes that the new methodology can also benefit students: As part of his courses for medical studies, Windfelder now uses 3D glasses to send the participants on a journey through the interior of the caterpillar. “Virtual reality is a game changer and will revolutionize teaching,” the scientist is convinced. For anyone else interested, there are now also various animated ones 3D videos from the body of the tobacco hornworm caterpillar available online.

Source: Justus Liebig University Giessen, specialist article: iScience, doi: 10.1016/j.isci.2023.106801

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