Single Cell Geometry Regulates Self-Renewal Factors in Osteosarcoma Cells via WDR5 Dependent Chromatin Methylation

Osteosarcoma (OS) is the most common primary malignant bone tumor in juveniles and young adults. OS cells respond to the complex mechanical cues in the tumor microenvironment to adapt and remodel their phenotype and behaviors. The transformation of cell morphological characteristics is the first visual representation of cell response to mechanical signals. But the biomechanical mechanisms by which cellular geometry leads to the changes in OS cell behaviors remain unclear. Here, we used micropattern printing to generate square, round, and rectangular single-cell geometries of equal area to investigate the effects induced by cellular geometric morphologies of human osteosarcoma U-2 OS cells. We showed that, compared to square-shaped cells, U-2 OS cells confined to round and rectangular micropatterns had increased MLCK expression, which enhanced cytoskeletal contractility through myosin II phosphorylation. Increased cytoskeletal contractility promoted nuclear translocation of WDR5, which increased H3K4me3 and upregulated the expression of the self-renewal markers of Nanog, Oct4, and Sox2. Ultimately, the self-renewal capability of U-2 OS cells enhanced. Our study provides insights into nuclear mechanotransduction of OS cells by demonstrating that spatial confinement induced remodeling of single-cell geometry enhances self-renewal and stemness maintenance of OS cells through WDR5-dependent chromatin methylation, which may provide a new perspective for tumor mechanical medicine.