Pharmacological Perturbation of Mechanical Contractility Enables Robust Transdifferentiation of Human Fibroblasts into Neurons.

Direct cell reprogramming, also called transdifferentiation, is valuable for cell fate studies and regenerative medicine. Current approaches to transdifferentiation are usually achieved by directly targeting the nuclear functions, such as manipulating the lineage-specific transcriptional factors, microRNAs, and epigenetic modifications. Here, a robust method to convert fibroblasts to neurons through targeting the cytoskeleton followed by exposure to lineage-specification surroundings is reported. Treatment of human foreskin fibroblasts with a single molecule inhibitor of the actomyosin contraction, can disrupt the cytoskeleton, promote cell softening and nuclear export of YAP/TAZ, and induce a neuron-like state. These neuron-like cells can be further converted into mature neurons, while single-cell RNA-seq shows the homogeneity of these cells during the induction process. Finally, transcriptomic analysis shows that cytoskeletal disruption collapses the original lineage expression profile and evokes an intermediate state. These findings shed a light on the underestimated role of the cytoskeleton in maintaining cell identity and provide a paradigm for lineage conversion through the regulation of mechanical properties.

Pharmacological regulation of tissue fibrosis by targeting the mechanical contraction of myofibroblasts.

Fibrosis can occur in almost all tissues and organs and affects normal physiological function, which may have serious consequences, such as organ failure. However, there are currently no effective, broad-spectrum drugs suitable for clinical application. Revealing the process of fibrosis is an important prerequisite for the development of new therapeutic targets and drugs. Studies have shown that the limiting of myofibroblast activation or the promoting of their elimination can ameliorate fibrosis. However, it has not been reported whether a direct decrease in cell contraction can inhibit fibrosis in vivo. Here, we have shown that (-)-blebbistatin (Ble), a non-muscle myosin Ⅱ inhibitor, displayed significant inhibition of liver fibrosis in different chronic injury mouse models in vivo. We found that Ble reduced the stiffness of fibrotic tissues from the early stage, which reduced the extent of myofibroblast activation induced by a stiffer extracellular matrix (ECM). Moreover, Ble also reduced the activation of myofibroblasts induced by TGF-ß1, which is the most potent pro-fibrotic cytokine. Mechanistically, Ble reduced mechanical contraction, which inhibited the assembly of stress fibers, decreased the F/G-actin ratio, and led to the exnucleation of YAP1 and MRTF-A. Finally, we verified its broad-spectrum antifibrotic effect in multiple models of organ fibrosis. Our results highlighted the important role of mechanical contraction in myofibroblast activation and maintenance, rather than just a characteristic of activation, suggesting that it may be a potential target to explore broad-spectrum drugs for the treatment of fibrotic diseases.