The entire intestinal epithelium is renewed every week due to cell division in the crypts coupled with cell migration towards the villi and loss of cells by apoptosis at the tip of villi. However, the mechanism responsible for the migration of intestinal cells was unclear. Using transgenic animals, ex vivo gut slice cultures, and theoretical modeling, we found that in the crypts, epithelial cells move passively due to the pushing force generated by dividing cells. However, along the villi, cells move actively using actomyosin-rich basal cellular protrusions.
In the second part of the seminar, I will talk about tumor microenvironment in tumor progression. Besides biochemical signals, mechanical forces from the microenvironment also play a role in tumor progression. Cancer-associate fibroblasts (CAFs) have enhanced contractility and capacity to synthesize, deposit, and crosslink ECM, making stroma stiffer. Thus, by accumulating around the tumor, they could provide a physical barrier constraining tumor expansion. However, it has been shown that by exerting mechanical forces on the ECM, CAFs also enhance tumor invasion. These antagonistic roles of forces produced by CAFs in tumor progression will be discussed.
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