Biophysical regulation of histone acetylation in mesenchymal stem cells.

Histone deacetylation and acetylation are catalyzed by histone deacetylase (HDAC) and histone acetyltransferase, respectively, which play important roles in the regulation of chromatin remodeling, gene expression, and cell functions. However, whether and how biophysical cues modulate HDAC activity and histone acetylation is not well understood. Here, we tested the hypothesis that microtopographic patterning and mechanical strain on the substrate regulate nuclear shape, HDAC activity, and histone acetylation. Bone marrow mesenchymal stem cells (MSCs) were cultured on elastic membranes patterned with parallel microgrooves 10 μm wide that kept MSCs aligned along the axis of the grooves. Compared with MSCs on an unpatterned substrate, MSCs on microgrooves had elongated nuclear shape, a decrease in HDAC activity, and an increase of histone acetylation. To investigate anisotropic mechanical sensing by MSCs, cells on the elastic micropatterned membranes were subjected to static uniaxial mechanical compression or stretch in the direction parallel or perpendicular to the microgrooves. Among the four types of loads, compression or stretch perpendicular to the microgrooves caused a decrease in HDAC activity, accompanied by the increase in histone acetylation and slight changes of nuclear shape. Knocking down nuclear matrix protein lamin A/C abolished mechanical strain-induced changes in HDAC activity. These results demonstrate that micropattern and mechanical strain on the substrate can modulate nuclear shape, HDAC activity, and histone acetylation in an anisotropic manner and that nuclear matrix mediates mechanotransduction. These findings reveal a new mechanism, to our knowledge, by which extracellular biophysical signals are translated into biochemical signaling events in the nucleus, and they will have significant impact in the area of mechanobiology and mechanotransduction.