Investigation of Colonic Regeneration via Precise Damage Application Using Femtosecond Laser-Based Nanosurgery.

Organoids represent the cellular composition of natural tissue. So called colonoids, organoids derived from colon tissue, are a good model for understanding regeneration. However, next to the cellular composition, the surrounding matrix, the cell-cell interactions, and environmental factors have to be considered. This requires new approaches for the manipulation of a colonoid. Of key interest is the precise application of localized damage and the following cellular reaction. We have established multiphoton imaging in combination with femtosecond laser-based cellular nanosurgery in colonoids to ablate single cells in the colonoids' crypts, the proliferative zones, and the differentiated zones. We observed that half of the colonoids recovered within six hours after manipulation. An invagination of the damaged cell and closing of the structure was observed. In about a third of the cases of targeted crypt damage, it caused a stop in crypt proliferation. In the majority of colonoids ablated in the crypt, the damage led to an increase in signalling, indicated via a fluorescent lentiviral biosensor. qRT-PCR analysis showed increased expression of various proliferation and -associated genes in response to damage. Our new model of probing colonoid regeneration paves the way to better understand organoid dynamics on a single cell level.