Over the last few decades, physical principles have been proposed to explain some biological processes and functions. However, biological principles remain elusive. A biological principle is a governing rule that guides the structure and functions of cells. Biological principles are built upon the laws of physics and chemistry, but they go beyond these laws and are unique to living matter. Here, we discuss what differentiates a biological principle from a physical principle and discuss candidates for biological principles. We review evidence from literature that regulation of cytoskeletal prestress (endogenous cytoskeletal pre-existing tensile stress) is essential for governing biological structures and functions of living cells. We propose that, in addition to the biological principles of Central Dogma and metabolism, cytoskeletal prestress homeostasis is a biological principle of a living cell across all domains of life. We propose that living cells regulate their stress and modulus to limit maximum strain on the cells. Homeostasis of endogenous energy-dependent, stress-supported systems that use cytoskeletal (CSK) prestress (the force of life) to stabilize structure represents a biological principle of a living cell that is not observed in inorganic systems, whereas other basic principles (e.g., self-assembly) are required for living systems but are also found in simpler nonliving systems. Leveraging biological principles of cells may have far-reaching implications in understanding the essence of cell life and designing effective interventions for therapeutics to advance medicine and enhance human health.

Solid tumours show substantial mechanical heterogeneity, yet how such cues influence the susceptibility of cancer cells to T cell-based therapies remains unclear. Here we discover that cancer cells grown on soft matrices are less sensitive to chimeric antigen receptor T cell cytotoxicity and exhibit elevated extracellular adenosine triphosphate and sustained calcium activity. To understand the mechanisms underlying this reduced killing, we sought to identify the cells that respond to mechanical softness. We engineered a doxycycline-gated calcium-activated transcriptional mechano-recorder that integrates softness-induced calcium activity over a defined recording window and converts this prior signalling history into a stable fluorescent output that persists for days. Unlike real-time calcium indicators, which report instantaneous calcium activity only at the moment of imaging, this recorder preserves a sortable transcriptional mark, enabling selective labelling and profiling of cells according to their past mechanosensing activity. Transcriptomic analyses showed that recorder-positive cells adopt a stem-like programme, including epithelial-mesenchymal transition, hypoxia responses, oncogenic signalling and elevated stemness markers, across cancer cell lines and patient-derived samples. To render these resistant cells targetable, we rewired the mechano-recorder into a mechano-reprogrammer by replacing the fluorescent output with the clinically validated antigen CD19, enabling softness-responsive cells to be recognized by CD19-directed T cells. This rewired system improved elimination of stem-like cancer cells in culture and animal models, converting mechanobiological resistance into therapeutic vulnerability.

[This corrects the article DOI: 10.1016/j.bioactmat.2024.11.018.].

Integrating mechanobiological principles into disease pathogenesis, therapeutic development, and tissue engineering is reshaping our understanding of biological systems and accelerating the advancement of mechanotherapy and mechanohealth. This field reveals how mechanical cues regulate cellular behavior, such as force transmission along integrin-nucleus pathways and collective cell migration, and tissue functions. In doing so, mechanobiology connects fundamental research with clinical applications, from limiting cancer metastasis and fibrosis to promoting bone regeneration and maintaining vascular homeostasis. Building on discussion from the Inaugural International Conference on Mechanobiology (ICM) 2025, integrating mechanobiological research with clinical strategies offers new opportunities to address unmet needs, including personalized anti-fibrotic interventions or precision bone regenerative therapies. At the same time, it supports the broader concept of mechanohealth -- a paradigm focused on preserving the physiological mechanical balance within tissues.

Background Synovial sarcoma is a malignant tumor of mesenchymal origin, which is characterized by the simultaneous expression of epithelia and mesenchyme. Tumor microenvironment plays an important role in the development of synovial sarcoma. Exon microarray showed that there were significant differences in cell adhesion-related genes of tumor microenvironment between epithelial cells and mesenchymal cells of synovial sarcoma. In this study, we measured the expression of focal adhesion kinase (FAK) and epithelial-mesenchymal transition (EMT) related proteins in biphasic synovial sarcoma and preliminarily explored the tumorigenic mechanism of FAK in synovial sarcoma. Methods FAK expression in sarcoma and normal mesenchymal tissues was analyzed using online databases. Laser capture microdissection and tissue microarray were employed to isolate epithelial and spindle cell components from synovial sarcoma specimens. Immunohistochemistry and quantitative real-time PCR (qRT-PCR) were performed to detect the expression of FAK and EMT-related molecules in the epithelial and mesenchymal components of synovial sarcoma tissues. In cellular functional experiments, FAK-overexpressing HS-SY-II cells were established using lentiviral transduction, and cell proliferation, migration, and invasion were assessed by CCK-8, colony formation, and Transwell assays. Immunofluorescence staining was performed to evaluate EMT marker expression. For in vivo validation, an experimental lung metastasis model was established via tail vein injection in nude mice. Finally, RNA-seq was used to detect transcriptomic alterations following FAK inhibition by TAE226, and expression of EMT-related factors was validated by Western blot and qRT-PCR. Results Multiple online databases revealed high FAK expression in sarcoma. In synovial sarcoma tissues, both protein and mRNA expression levels of FAK were higher in the spindle cell area than in the epithelial area. FAK expression was negatively correlated with E-cadherin and positively correlated with N-cadherin and Snail. High FAK expression was significantly associated with poor prognostic factors including recurrence, metastasis, FNCLCC grade III, and TNM stage IV. Functional assays demonstrated that FAK overexpression significantly enhanced proliferation, migration, and invasion of HS-SY-II cells. Immunofluorescence staining showed that FAK upregulation induced EMT, as evidenced by decreased E-cadherin and increased N-cadherin and Vimentin expression. In vivo, FAK overexpression increased lung metastasis incidence (3/5 vs. 0/5 in controls). Conversely, inhibition of FAK by TAE226 in SW982 cells significantly decreased cell motility, migration, and proliferation. RNA-seq analysis revealed significant alterations in EMT-related pathways following FAK inhibition, which was confirmed by Western blot and qRT-PCR showing decreased mesenchymal markers and increased epithelial markers. Conclusion Our data demonstrate that FAK induces EMT and is associated with poor prognosis in synovial sarcoma. FAK regulates the expression of EMT-related factors and the EMT process, leading to changes in tumor cell invasion, migration, proliferation, and metastasis. These findings suggest that FAK could be a promising therapeutic target for synovial sarcoma.

How forces and mechanics influence and regulate living cells remains elusive. Mechanomemory, the response to a mechanical perturbation that persists after the perturbation is removed, is believed to be a key to understanding the impact of forces and mechanics on cell functions. Recently, our lab has demonstrated the presence of mechanomemory that lasts for ∼30 min after applying external stress via integrins. Herein, we test the hypothesis that applications of short intermittent episodes of stress exert long-term effects on mechanomemory via the process of mechanotransduction. An Arginine-Glycine-Aspartic acid (RGD)-peptides-coated 4-μm magnetic bead was bound to the integrin receptors to apply stresses to the surface of a Chinese Hamster Ovary cell. At the same stress magnitude and frequency (15 Pa at 0.3 Hz), multiple cycles of externally applied intermittent 2 or 10 min stresses with 15 min intervals, 10 min stresses with 10 min intervals, or a 30 min stress plus a 30 min load-free interval increased nuclear translocation of YAP (Yes-Associated Protein) and Ctgf gene expression, like that by a 60 min continuous stress, but a 30 min continuous stress did not. Short durations of intermittent stresses increased F-actin in the cytoplasm, which coincided with the elevated YAP translocation. Inhibiting F-actin or actomyosin but not microtubules blocked stress-induced YAP translocation to the nucleus. Cells on soft substrates translocate more YAP than on stiff substrates after external load release. These results highlight the impact of multiple intermittent stresses-induced cytoplasmic mechanomemory on cell biological functions via YAP translocation.

Two recent conferences on mechanotransduction in biology and medicine showcased remarkable progress in this field and the potential for bringing mechanobiology into the clinic. In this Perspective, we discuss recent advances, the conceptual frameworks needed to develop clinical tools based on mechanobiology, and prospects for the future.

Endogenous forces generated by living cells are essential for biological processes and physiological functions of cells and tissues. Over the last several decades, numerous methods for detecting traction forces have been developed. Here we review these methods and discuss their respective strengths and limitations. Being able to reliably quantify tractions in living cells and tissues are critical in understanding how forces drive and regulate cell and tissue functions in physiology and diseases.

Increasing evidence suggests that the mechanics of chromatin and nucleoplasm regulate gene transcription and nuclear function. However, how the chromatin and nucleoplasm sense and respond to forces remains elusive. Here, we employed a strategy of applying forces directly to the chromatin of a cell via a microinjected 200-nm anti-H2B-antibody-coated ferromagnetic nanoparticle (FMNP) and an anti-immunoglobulin G (IgG)antibody-coated or an uncoated FMNP. The chromatin behaved as a viscoelastic gel-like structure and the nucleoplasm was a softer viscoelastic structure at loading frequencies of 0.1-5 Hz. Protein diffusivity of the chromatin, nucleoplasm, and RNA polymerase II (RNA Pol II) and RNA Pol II activity were upregulated in a chromatin-stretching-dependent manner and stayed upregulated for tens of minutes after force cessation. Chromatin stiffness increased, but the mechanomemory duration of chromatin diffusivity decreased, with substrate stiffness. These findings may provide a mechanomemory mechanism of transcription upregulation and have implications on cell and nuclear functions.

There is increasing evidence that force impacts almost every aspect of cells and tissues in physiology and disease including gene regulation. However, the molecular pathway of force transmission from the nu-clear lamina to the chromatin remain largely elusive. Here we employ two different approaches of a local stress on cell apical surface via an RGD (Arg-Gly-Asp)-coated magnetic bead and whole cell deformation at cell basal surface via uniaxial or biaxial deformation of a fibronectin-coated flexible polydimethyl-siloxane substrate. We find that nuclear protein LAP2 beta mediates force transmission from the nuclear lamina to the chromatin. Knocking down LAP2 beta increases spontaneous movements of the chromatin by reducing tethering of the chromatin and substantially inhibits the magnetic bead-stress or the substrate -deformation induced chromatin domain stretching and the ensuing dihydrofolate reductase (DHFR) gene upregulation. Analysis of DHFR gene-containing chromatin domain alignments along or perpendicular to the direction of the stretching/compressing reveals that the chromatin domain must be stretched and not compressed in order for the gene to be rapidly upregulated. Together these results suggest that external -load induced rapid transcription upregulation originates from chromatin domain stretching but not com-pressing and depends on the molecular force transmission pathway of LAP2 beta. Statement of significanceHow force regulates gene expression has been elusive. Here we show that the orientation of the chro-matin domain relative to the stress direction is crucial in determining if the chromatin domain will be stretched or compressed in response to a cell surface loading. We also show that nuclear protein Lap2b is a critical molecule that mediates force transmission from the nuclear laminar to the chromatin to reg-ulate gene transcription. This study reveals the molecular force transmission pathway for force-induced gene regulation.(c) 2021 Acta Materialia Inc. Published by Elsevier Ltd. All rights reserved.

It is known that external mechanical forces can regulate structures and functions of living cells and tissues in physiology and diseases. However, after cessation of the force, how structures are altered in response to the dynamics of the chromatin and molecules in the nucleoplasm remains elusive. Here, using single-molecule imaging approaches, we show that exogenous local forces via integrins applied for 2 to 10 min decondensed the chromatin and increased chromatin and nucleoplasm protein mobility inside the nucleus, leading to elevated diffusivity of single protein molecules in the nucleoplasm, tens of minutes after the cessation of force. Diffusion experiments with fluorescence correlation spectroscopy in live single cells show that the mechanomemory in chromatin and nucleoplasm protein diffusivity was regulated by nuclear pore complexes. Protein molecular dynamics simulation recapitulated the experimental findings in live cells and showed that nucleoplasm protein diffusivity was regulated by the number of nuclear pore complexes. The mechanomemory in elevated protein diffusivity of the nucleoplasm after force cessation represents a physical process that reverses protein-protein condensation in phase separation via unjamming of the chromatin. Our findings of mechanomemory in chromatin and nucleoplasm protein diffusivity suggest that the effect of force on the nucleus remains tens of minutes after force cessation and thus is more far-reaching than previously anticipated.

Supplementary Figure S6. TRCs lost PCK1 expression in conventional rigid dish and inhibition of PCK1 enzymatic activity resulted in the decrease of bulk tumor cell number.

Supplementary Figure S1. The silence efficiency of siRNA against G9a, SUV39h1 or PCK1 and identification of constructs.

Figure S1 related to figure 1; figure S2 related to figure 2; figure S3 related to figure 3; figure S4 related to figure 4; figure S5 related to figure 5; figure S6 related to figure 6 and supplementary experimental procedures

Legends for Supplementary Figures S1-S8.

Supplementary Figure S7. High methylation in promoter region of PCK1 gene. B16 TRCs and control cells were used for DNA isolation.

Supplementary Methods. Description of additional methods and procedures used in the study.

Supplementary Figure S3. Fructose-1,6-bisphosphatase (FBP1) and glucose-6- phosphatase (G6Pase) were not expressed in B16 TRCs and PCK1 knockdown had no effect on glucose transporter 1 (GLUT1) expression and membrane localization.

Supplementary Table S1. List of RT-PCR primers used.

Supplementary Figure S2. The expression of PCK1 in CD133+ B16 cells, human primary melanoma TRCs and melanoma tissues.