An Innate YAP/TAZ Mechanosensing Deficit in Hutchinson-Gilford Progeria Syndrome
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Hutchinson-Gilford Progeria Syndrome (HGPS) is a disease of accelerated aging causing death in the mid-teens from myocardial infarction or stroke. The disease is caused by a point mutation in the gene encoding lamin-A. The mutated scaffolding protein is aberrantly farnesylated inducing a constellation of defects included nuclear abnormalities, genomic damage, and rapid senescence. Therapy targeting the abnormal farnesylation provides a modest extension of life, thus new insights and therapeutic approaches are urgently needed for these children. Consistent with previous morphological observations and new studies implicating YAP/TAZ mechanobiology as an important mechanical pathway for endothelial cell (EC) health under shear stress, we hypothesized that HGPS ECs have an innate mechanical disturbance rendering them unable to respond to external, atheroprotective cues. We used a microfluidic vessel-on-a-chip with channel geometries and fluid flow to precisely model the hemodynamic stimuli present in vasculature as we have previously described. We cultured iPSC-derived HGPS ECs in this system to study mechanoresponse to shear stress and YAP/TAZ signaling. HGPS ECs manifest a rounded, flattened appearance characteristic of senescent ECs, are unable to align in response to flow, and have aberrant YAP/TAZ activity despite unidirectional laminar flow. To explore the physical underpinnings of such biochemical disturbances, we used atomic force microscopy (AFM) to precisely characterize the shape of individual HGPS cells, and their deformation to a controlled force applied by the AFM cantilever. Preliminary measurements confirmed that HGPS cells have a reduced profile and are compositely stiffer (nuclear modulus + cytoskeletal modulus) than cells derived from the unaffected parent of the child. These data provide evidence of altered biophysical properties of senescent cells which we term mechanical aging, which is associated with aberrant signaling in response to hemodynamic stimuli. Further characterization of mechanical aging may lead to new therapeutic approaches for HGPS and other age-related diseases.
