Nuclear stiffness decreases with disruption of the extracellular matrix in living tissues
Reciprocal interactions between the cell nucleus and the extracellular matrix lead to macroscale tissue phenotype changes. The extracellular environment is physically linked to the nuclear envelope and provides cues to maintain nuclear structure and cellular homeostasis regulated in part by mechanotransduction mechanisms. However, little is known about how structure and properties of the extracellular matrix in living tissues impacts nuclear mechanics, and current experimental challenges limit the ability to detect and directly measure nuclear mechanics while cells are within the native tissue environment. Here, we hypothesized that enzymatic disruption of the tissue matrix results in a softer tissue, affecting the stiffness of embedded cell and nuclear structures. We aimed to directly measure nuclear mechanics without perturbing the native tissue structure to better understand nuclear interplay with the cell and tissue microenvironments. To accomplish this, we expanded an atomic force microscopy needle-tip probe technique that probes nuclear stiffness in cultured cells to measure the nuclear envelope and cell membrane stiffness within native tissue. We validated this technique by imaging needle penetration and subsequent repair of the plasma and nuclear membranes of HeLa cells stably expressing the membrane repair protein CHMP4B-GFP. In the native tissue environment ex vivo, we found that while enzymatic degradation of viable cartilage tissues with collagenase 3 (MMP-13) and aggrecanase-1 (ADAMTS-4) decreased tissue matrix stiffness, cell and nuclear membrane stiffness is also decreased. Finally, we demonstrated the capability for cell and nucleus elastography using the AFM needle-tip technique. These results demonstrate disruption of the native tissue environment that propagates to the plasma membrane and interior nuclear envelope structures of viable cells.