Creating organoids to understand hormones and tumors – PhD defense Adriana Martinez Silgado

Organoids are miniature organs that can be cultured in the lab. Scientists can grow them from stem cells: cells that are present in most tissues in our bodies and that have the potential to form the specialized cells a tissue needs. Researchers from the Clevers group first succeeded in growing intestinal organoids in 2009, and since then organoids from almost every organ in the human body have been produced. They provide a way to study the function of human organs in a lab dish, both in health and disease. During her PhD, Adriana used organoids to study hormone production in the gut and two types of tumors.

Intestinal hormones

She first worked on growing organoids of the human small intestine that allowed her to study a specific subtype of gut cell: the enteroendocrine cell (EEC). These cells, which are quite rare in the gut, can detect the content of the intestine and produce hormones that regulate digestion and metabolism. Together with her colleagues, Adriana produced organoids enriched for EECs by stimulating intestinal organoids to produce these cells. “We did this by using the signals that normally also induce specialization into EECs in the body,” says Adriana. “Using these organoids, we were then able to study exactly which hormones the EECs produce.”

Rare but relevant

This opens up new research opportunities. “Studying these cells was quite difficult before, because EECs are rare in the human gut and there were no lab models to investigate them,” Adriana explains. “Due to this, we still don’t know the function of several hormones produced by EECs. But they have real medical relevance. For example, millions of people are treated with drugs called GLP-1 agonists. They are used for diabetes and obesity, and mimic hormones that are produced by gut EECs.”

Making tumor organoids

Adriana and her colleagues then turned to modelling two specific tumor types: neuroendocrine neoplasms of the gut and lung, and squamous-cell carcinoma of the lung. They did this by using healthy human gut and lung organoids, in which they introduced mutations – changes in the DNA code – that are associated with tumor formation. “We used a variant of the CRISPR method, which uses protein complexes called base editors to make mutations. This allows us to very precisely steer which letters in the DNA code we want to change,” Adriana explains. “We showed that introducing just a few specific mutations into the organoids was enough to recreate some of the key features of the tumors.”

Creating to understand

Scientists can use the tumor organoids to learn more about the causes of cancer. “Understanding how these tumors first arise is crucial for detecting, treating, and ultimately preventing them,” says Adriana. In this context she cites theoretical physicist Richard Feynman: “He said ‘What I cannot create, I do not understand.’ In this case, CRISPR and organoids bring us closer to understanding where these tumors come from.”

Solving the riddle

According to Adriana, doing a PhD is a test in perseverance, hard work and teamwork. “You need to be able to accept that most experiments will not lead to publishable results,” she says. Working with organoids also takes quite some dedication. “They are very needy. You need to take care of them constantly, even on holidays.” The highlights of Adriana’s PhD were the moments when her perseverance paid off. “There is a rush you feel when something you have been working on for years finally works. Or when after reading a lot of literature a mechanism clicks. It is like solving a riddle that took years to crack,” she concludes.