Exploring The Role of Mechanical Forces During Human Embryonic Stem Cell Differentiation

Yoel Goldstein ^1,2 Danny Kitsberg ^1,2 Elishai Ezra ^1,2 Ronit Malka ³ Danny Bavli ^1,2 Merav Cohen ^1,2 Assaf Zemel ⁴ Amnon Buxboim ^1,2 Yaakov Nahmias ^1,2

¹Department of Cell and Developmental Biology, Silberman Institute of Life Sciences, Hebrew University of Jerusalem, 1
²2. Grass Center for Bioengineering, School of Computer Science and Engineering, Hebrew University of Jerusalem, 2
³School of Engineering and Applied Sciences, Harvard University, 3
⁴Institute of Dental Sciences, Hebrew University of Jerusalem, 4

Early embryogenesis is associated with tissue deformation, culminating post-implantation with the establishment of the embryonic disc and the separation of epiblast from the primitive endoderm. While chemical factors have been extensively studied, the role of mechanical forces in this process remains unclear. Here we demonstrate that mimicking post-implantation mechanical environment is sufficient to establish layers of mesendodermal and primitive endoderm-like cells. We modeled the mechanical forces occurring during human embryonic implantation and mimicking the physical microenvironment using a 2D in vitro model system for culturing hES cells on micro-patterned adhesive islands of controlled curvature. Human embryonic stem cells cultured on curved patterns showed SOX17+ positive endoderm cells emerging in regions of high stress, while OCT4+/Brach+/EOMES+ mesendodermal cells segregated to low-stress regions. This pattern is abolished by inhibition of Myosin-II activity. Our results suggest that mechanical forces play a role in early germ layer specification.