This stunning image may look like a particularly lively Jackson Pollock painting, but it’s actually an example of a new cell imaging technique. The subject? A human retina.
In fluorescence microscopy, tissue is imaged using fluorescent dyes that stain specific proteins. But this technique can only be done with three to five different dyes at once, limiting the detail that can be captured in a single image.
To expand the detail 10 times over, the researchers on the new study took advantage of a new technique called iterative indirect immunofluorescence imaging (4i). The basic principle sounds simple enough – after you’ve snapped an image and made measurements using three dyes, you wash the dyes out of the sample and then stain it with three more. Repeat this over and over, then use a computer to merge all the images into one and voilà – the end result is a single microscope image with dozens of types of proteins marked.
In this case, researchers at ETH Zurich used the 4i technique to create a new cell atlas of the human retina. Over 18 days, a robot snapped images of 18 different batches of stained proteins, eventually creating a colorful microscope image containing 53 different types of proteins.
Rather than retinas taken from people, they grew mini 3D versions of them in the lab from stem cells, which develop in a very similar way to the real thing. Using these retina organoids, the team demonstrated how this kind of imaging could be used to study human development. The researchers performed their process on a series of retina organoids of different ages, all the way through their 39-week development period.
“We can use this time series to show how the organoid tissue slowly builds up, where which cell types proliferate and when, and where the synapses are located,” said Gray Camp, senior author of the study. “The processes are comparable to those of retinal formation during embryonic development.”
Next up, the researchers plan to use this technique on retina organoids with conditions like retinitis pigmentosa, a degenerative disease that can lead to blindness, to study the progression of the disease and look for new insights into how to treat it. Ultimately they hope to also apply the technique to other types of tissues to study development and disease.
The research was published in the journal Nature Biotechnology.
Source: ETH Zurich
