1) Understand the advantages of IVM and how it can be used to study dynamic processes in tumor biology and beyond. 2) Get insights into metastatic colonization. 3) Get insights into intestinal stem cell homeostasis.
Purpose: Intravital microscopy can be used to visualize dynamic biological processes in their native environment. By visualizing tissues through an optical window with a two-photon microscope, cell behavior can be studied over weeks. Here, we report the development of an abdominal imaging window (AIW) for mice. We use the AIW to longitudinally follow liver metastases to link cellular behavior to successful colonization. Moreover, we use the AIW to glimpse at the short-term dynamics of intestinal stem cells (SC).
Methods: A titanium AIW was implanted into the abdomen of mice. In our metastasis study we intrasplenically injected fluorescent C26 colorectal cancer cells to generate liver metastases. A splenectomy was performed to prevent outgrowth in the spleen. A daily imaging regimen was used to study liver metastases. In our SC study we used Lgr5eGFP-Ires-CreERT2/R26R-Confetti mice to visualize Lgr5+ intestinal SCs and their progeny daily.
Results: We show that single extravasated tumor cells proliferate to form so called pre-micrometastases in which cells are highly migratory. Once the clones condense into micrometastases, cell migration is diminished. Surprisingly, during the pre-micrometastasis stage migration is positively correlated with proliferation. Blocking of migration during this stage greatly reduced metastatic load, suggesting that cell migration during the pre-micrometastasis stage is a contributing step to colorectal liver metastasis.
During intestinal homeostasis, we show that SCs in the upper part of the niche can be passively displaced out of the niche after division of a near-by SC. Moreover, we found that SCs in the central part of the niche experience a survival advantage over cells in the border. SCs were able to transfer between border and center region in both directions, endowing each SC with long-term self-renewal potential.
Conclusion: We conclude that IVM is an important imaging platform to study complex dynamic processes in vivo.
Ritsma, L,
Spying on Cancer Metastasis Using Intravital Microscopy: Seeing Is Believing. Radiological Society of North America 2014 Scientific Assembly and Annual Meeting, - ,Chicago IL.
http://archive.rsna.org/2014/14004192.html
