Pulmonary arterial hypertension (PAH) is a potentially fatal disease characterized by obliterative remodeling of distal pulmonary arteries, commonly associated with bone morphogenetic receptor type 2 (BMPR2) gene mutations. In patients with PAH, sotatercept, an activin signaling inhibitor, improves hemodynamics and outcomes, but clinical responses vary and sometimes occur within weeks, suggesting additional mechanisms beyond its anti-proliferative, pro-apoptotic and anti-remodeling effects. Using patient-specific induced pluripotent stem cell-derived smooth muscle cells (iSMCs) with BMPR2 extracellular- or kinase-domain mutations, we were able to reproduce Activin A-driven PAH traits, including hyperproliferation, reduced apoptosis, enhanced contraction and excessive matrix production. We identified smooth muscle cell-to-myofibroblast transition as a previously unknown contributor to pulmonary vascular remodeling and demonstrate that it is blocked by sotatercept. Beyond its established effects, sotatercept rapidly reduced contractility, collagen-integrin mechanotransduction and TGF-beta receptor expression, disrupting a pathological positive feedback loop, reflected by lower levels of circulating TGF-beta 1 in patients on sotatercept. Taken together, our patient-derived iSMC platform links mutation-dependent mechanisms of pulmonary vascular remodeling to variable drug responsiveness and reveals previously unrecognized, potentially rapid-acting modes of sotatercept in PAH. ### Competing Interest Statement The authors have declared no competing interest. German Center for Lung Research, 82DZL002C1 German Research Foundation OL, 653/2-1 Lower Saxony (Nachhaltigkeitsfinanzierung Exzellenzcluster REBIRTH), ZN3440 German Research Foundation DFG KFO311, MA 2331/18-1, MA 2331/18-2
Cardiomyocyte mechanotransduction has traditionally focused on the sarcomere and cytoskeleton, yet emerging evidence highlights the nucleus as an active mechanical responder. To adapt to the dynamic mechanical environment, the nucleus forms nuclear invaginations (NIs), double-membrane folds that provide structural support to chromatin and incorporate nuclear pore complexes to facilitate nucleo-cytoplasmic transport, including Ca2+ transport. However, how these structures are formed is not yet understood. We leveraged advances in high-resolution microscopy, mechanical stimulation, rat models and human samples, to study the formation, function and remodelling of cardiac NIs in Heart Failure (HF). Here, we demonstrate that the formation of NI in cardiomyocytes is regulated by both, cytoskeleton such as actin and detyrosinated microtubules as well as intranuclear nucleolar interactions with NI disruption resulting in elevated baseline nuclear Ca2+. In a 16-week post-Myocardial Infarction (MI) end-stage HF rat model, as well as in human Dilated Cardiomyopathy samples, a marked reduction in NIs is observed. Importantly, NI loss is already evident at 8 weeks post-MI, preceding detectable cytoskeletal stiffening. At this earlier stage, we observe increased DNA damage in the peri-nucleolar region, accompanied by nucleolar remodelling and a shift in nucleolar biomechanical properties. In conclusion, nucleolar maintenance emerges as a potential target for intervention. ### Competing Interest Statement The authors have declared no competing interest. The authors would like to acknowledge the Cellular Mechanosensing and Functional Microscopy Centre at Imperial College London for access to equipment. British Heart Foundation Imperial Centre of Research Excellence Award, RE/18/4/34215 EU-METAHEART Cost Action CA22169 British Heart Foundation, PG/20/6/34835; SP/F/23/150045 Austrian Science Fund, 10.55776/PAT9036624 and 10.55776/STA194 Molecular Medicine PhD Program at the Medical University of Graz UKRI Engineering and Physical Sciences Research Council, EP/X036049/1 Add-on Fellowship of the Joachim Herz Foundation
Natural Killer(NK) cells eliminate target cells through antibody-dependent cell-mediated cytotoxicity(ADCC), initiated by CD16a(FcΞ³RIIIa) recognizing the Fc region of antibodies bound to the target cell surface. While the recognition is considered to be driven by CD16a-Fc binding avidity, it fails to explain why Fc multimers inhibit ADCC rather than trigger it. Here, we reveal that CD16a transduces piconewton forces, and acts as a mechanosensor to facilitate NK activation. We demonstrate that CD16a force and the actin foci formation associated with it are essential for the phosphorylation of mechanosensitive adaptor Cas-L and signaling adaptor LAT, reshaping NK cell cytoskeletal dynamics and signaling. Our findings show that NK activation is an intricate process that integrates both biochemical and biophysical information, and provides new mechanistic insight for immunoengineering. ### Competing Interest Statement The authors have declared no competing interest.
Rxiv mechanobio