Detailed Image of the Human Retina

What cell types are found in which human tissue, and where? Which genes are active in the individual cells, and which proteins are found there? Answers to these questions and more are to be provided by a specialised atlas – in particular how the different tissues form during embryonic development and what causes diseases. In creating this atlas, researchers aim to map not only tissue directly isolated from humans, but also structures called organoids. These are three-dimensional clumps of tissue that are cultivated in the laboratory and develop in a way similar to human organs, but on a small scale.

“The advantage of organoids is that we can intervene in their development and test active substances on them, which allows us to learn more about healthy tissue as well as diseases,” explains Barbara Treutlein, Professor of Quantitative Developmental Biology at the Department of Biosystems Science and Engineering at ETH Zurich in Basel.

To help produce such an atlas, Treutlein, together with researchers from the Universities of Zurich and Basel, has now developed an approach to gather and compile a great deal of information about organoids and their development. The research team applied this approach to the organoids of the human retina, which they derived from stem cells.

Many proteins visible simultaneously

At the heart of the methods the scientists used for their approach was the 4i technology: iterative indirect immunofluorescence imaging. This new imaging technique can visualise several dozen proteins in a thin tissue section at high resolution using fluorescence microscopy. The 4i technology was developed a few years ago by Lucas Pelkmans, a professor at the University of Zurich and coauthor of the study that has just been published in the scientific journal external pageNature Biotechnology. It is in this study that the researchers applied this method to organoids for the first time.

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