Mechanobiology: A landscape for reinterpreting stem cell heterogeneity and regenerative potential in diseased tissues

DNA-based Precision Tools to Probe and Program Mechanobiology and Organ Engineering

DNA nanotechnology represents an innovative discipline that combines nanotechnology with biotechnology. It exploits the distinctive characteristics of deoxyribonucleic acid (DNA) to create nanoscale structures and devices with remarkable accuracy and functionality. Researchers may create complex nanostructures with precision and specialized functions using DNA's innate stability, adaptability, and capacity to self-assemble through complementary base-pairing interactions. Integrating multiple disciplines, known as nanobiotechnology, allows the production of sophisticated nanodevices with a broad range of applications. These include precise drug delivery systems, extremely sensitive biosensors, and the construction of intricate tissue scaffolds for regenerative medicine. Moreover, combining DNA nanotechnology with mechanobiology provides a new understanding of how small-scale mechanical stresses and molecular interactions affect cellular activity and tissue development. DNA nanotechnology has the potential to revolutionize molecular diagnostics, tissue engineering, and organ regeneration. This could lead to enormous improvements in biomedicine. This review emphasizes the most recent developments in DNA nanotechnology, explicitly highlighting its significant influence on mechanobiology and its growing involvement in organ engineering. It provides an extensive overview of present trends, obstacles, and future prospects in this fast-progressing area.

Mesenchymal stem cell therapy in atherosclerosis: A bibliometric and visual analysis

BACKGROUND

Mesenchymal stem cells (MSCs) are capable of self-renewal and differentiation, and extensive studies have demonstrated their therapeutic potential in atherosclerosis (AS).

AIM

To conduct a bibliometric analysis of studies on the use of MSC therapy for AS over the past two decades, assess key trends and provide insights for future research directions.

METHODS

We systematically searched the Web of Science Core Collection database for articles published between 1999 and 2023, yielding a total of 556 articles. Visual representation and bibliometric analysis of information and trends were facilitated using CiteSpace, the R package 'bibliometrix' and VOSviewer.

RESULTS

The analyzed articles were predominantly from 52 countries/regions, with prominent contributions from China and the United States. A cohort of 3057 authors contributed to these publications, with the works of Libby P distinguished by their influence and citation count. Int J Mol Sci has emerged as the journal with the highest publication volume, prominently disseminating influential papers and identifying citation outbreaks. Furthermore, our analysis identified current research hotspots within the field, focusing on vascular progenitor cells, inflammatory mechanisms, and extracellular vesicles. Emerging research frontiers, such as extracellular vesicles and oxidative stress, have been highlighted as areas of burgeoning interest. Finally, we offer perspectives on the status of research and future directions of MSC therapy in AS.

CONCLUSION

This comprehensive analysis provides valuable insights for advancing scientific research on MSC therapy for AS. By elucidating pivotal trends and research directions, this study aimed to foster innovation and promote the progress of disciplines in this field, thereby contributing to advancing scientific knowledge and clinical practice.

Peeking into the future: inferring mechanics in dynamical tissues

Cells exert forces on each other and their environment, shaping the tissue. The resulting mechanical stresses can be determined experimentally or estimated computationally using stress inference methods. Over the years, mechanical stress inference has become a non-invasive, low-cost computational method for estimating the relative intercellular stresses and intracellular pressures of tissues. This mini-review introduces and compares the static and dynamic modalities of stress inference, considering their advantages and limitations. To date, most software has focused on static inference, which requires only a single microscopy image as input. Although applicable in quasi-equilibrium states, this approach neglects the influence that cell rearrangements might have on the inference. In contrast, dynamic stress inference relies on a time series of microscopy images to estimate stresses and pressures. Here, we discuss both static and dynamic mechanical stress inference in terms of their physical, mathematical, and computational foundations and then outline what we believe are promising avenues for in silico inference of the mechanical states of tissues.

Mesenchymal Stem Cell Plasticity: What Role Do Culture Conditions and Substrates Play in Shaping Biomechanical Signatures?

Cell functionality, driven by remarkable plasticity, is strongly influenced by mechanical forces that regulate mesenchymal stem cell (MSC) fate. This study explores the biomechanical properties of jaw periosteal cells (JPCs) and induced mesenchymal stem cells (iMSCs) under different culture conditions. We cultured both JPCs and iMSCs (n = 3) under normoxic and hypoxic environments, with and without osteogenic differentiation, and on laminin- or gelatin-coated substrates. Using atomic force microscopy, we measured cellular elasticity and Young's modulus of calcium phosphate precipitates (CaPPs) formed under osteogenic conditions. Correlation analyses between cellular stiffness, quantity of CaPP deposition, and stiffness of formed CaPPs were evaluated. The results showed that iMSCs, despite their softer cellular consistency, tended to form CaPPs of higher elastic moduli than osteogenically differentiated JPCs. Particularly under normoxic conditions, JPCs formed stronger CaPPs with lower cellular stiffness profiles. Conversely, iMSCs cultivated under hypoxic conditions on laminin-coated surfaces produced stronger CaPPs while maintaining lower cellular stiffness. We conclude that JPCs and iMSCs display distinct biomechanical responses to culture conditions. While JPCs increase cellular stiffness during osteogenic differentiation, in particular under hypoxic conditions, iMSCs exhibit a decrease in stiffness, indicating a higher resistance to lower oxygen levels. In both cell types, a lower cellular stiffness profile correlates with enhanced mineralization, indicating that this biomechanical fingerprint serves as a critical marker for osteogenic differentiation.

Advances in mechanotransduction and sonobiology: effects of audible acoustic waves and low-vibration stimulations on mammalian cells

In recent decades, research on mechanotransduction has advanced considerably, focusing on the effects of audible acoustic waves (AAWs) and low-vibration stimulation (LVS), which has propelled the field of sonobiology forward. Taken together, the current evidence demonstrates the influence of these biosignals on key cellular processes, such as growth, differentiation and migration in mammalian cells, emphasizing the determining role of specific physical parameters during stimulation, such as frequency, sound pressure level/amplitude and exposure time. These mechanical waves interact with various cellular elements, including ion channels, primary cilia, cell-cell adhesion receptors, cell-matrix and extracellular matrix proteins, and focal adhesion complexes. These components connect with the cytoskeletal fibre network, enabling the transmission of mechanical stimuli towards the nucleus. The nucleus, in turn, linked to the cytoskeleton via the linkers of the nucleoskeleton and cytoskeleton complex, acts as a mechanosensitive centre, not only responding to changes in cytoskeletal stiffness and nuclear tension but also regulating gene expression through the transcriptional co-activator YAP/TAZ and interactions between chromatin and the nuclear envelope. This intricate chain of mechanisms highlights the potential of sonobiology in various fields, including dentistry, regenerative medicine, tissue engineering and cancer research. However, progress in these fields requires the establishment of standardized measurement methodologies and biocompatible experimental setups to ensure the reproducibility of results.

Nanoparticles in Bone Regeneration: A Narrative Review of Current Advances and Future Directions in Tissue Engineering

The rising demand for effective bone regeneration has underscored the limitations of traditional methods like autografts and allografts, including donor site morbidity and insufficient biological signaling. This review examines nanoparticles (NPs) in tissue engineering (TE) to address these challenges, evaluating polymers, metals, ceramics, and composites for their potential to enhance osteogenesis and angiogenesis by mimicking the extracellular matrix (ECM) nanostructure. The methods involved synthesizing and characterizing nanoparticle-based scaffoldsand integrating hydroxyapatite (HAp) with polymers to enhance mechanical properties and osteogenic potential. The results showed that these NPs significantly promote cell growth, differentiation, and bone formation, with carbon-based NPs like graphene and carbon nanotubes showing promise. NPs offer versatile, biocompatible, and customizable scaffolds that enhance drug delivery and support bone repair. Despite promising results, challenges with cytotoxicity, biodistribution, and immune responses remain. Addressing these issues through surface modifications and biocompatible molecules can improve the biocompatibility and efficacy of nanomaterials. Future research should focus on long-term in vivo studies to assess the safety and efficacy of NP-based scaffolds and explore synergistic effects with other bioactive molecules or growth factors. This review underscores the transformative potential of NPs in advancing BTE and calls for further research to optimize these technologies for clinical applications.

Optical-resolution photoacoustic microelastography system for elasticity mapping: Phantom study and practical application

Elastography is a noninvasive technique for characterizing the mechanical properties of biological tissues. Conventional methods have limitations in resolution and sensitivity, hindering disease detection in clinical diagnostics. To address these issues, this study developed an optical-resolution photoacoustic microelastography (OR-PAME) system. Using an agar tissue phantom with varying agar concentrations and contrast agents, PAME evaluated elasticity distribution under compression in both lateral and axial dimensions. It indirectly measured elastic properties by correlating photoacoustic responses, temporal lags, and induced displacement. We also applied the system to the study of the distribution of elastic characteristics of the liver tissue after ablation, which confirmed the potential of OR-PAME in the study of elastic characteristics. Quantitative analysis showed greater lateral displacement in regions with reduced agar concentrations, indicating decreased stiffness. PAME also detected vertical displacement along the axial plane, validating its efficacy in elastographic imaging. By improving resolution and penetration, PAME provides superior visualization of elasticity distribution. Its methodology correlates microstructural alterations with tissue biomechanics, holding potential implications in medical diagnostics.

Rac1 promotes kidney collecting duct repair by mechanically coupling cell morphology to mitotic entry

Prolonged obstruction of the ureter, which leads to injury of the kidney collecting ducts, results in permanent structural damage, while early reversal allows for repair. Cell structure is defined by the actin cytoskeleton, which is dynamically organized by small Rho guanosine triphosphatases (GTPases). In this study, we identified the Rho GTPase, Rac1, as a driver of postobstructive kidney collecting duct repair. After the relief of ureteric obstruction, Rac1 promoted actin cytoskeletal reconstitution, which was required to maintain normal mitotic morphology allowing for successful cell division. Mechanistically, Rac1 restricted excessive actomyosin activity that stabilized the negative mitotic entry kinase Wee1. This mechanism ensured mechanical G2-M checkpoint stability and prevented premature mitotic entry. The repair defects following injury could be rescued by direct myosin inhibition. Thus, Rac1-dependent control of the actin cytoskeleton integrates with the cell cycle to mediate kidney tubular repair by preventing dysmorphic cells from entering cell division.

[Hot Topics and Emerging Trends in Mechanobiology Research]

Mechanobiology focuses on a series of important physiopathological processes, such as how cells perceive different mechanomechanical stimuli, the process of intracellular mechanotransduction, and how mechanical signals determine the behavior and fate of cells. From the initial stage of embryogenesis, to developmental biology and regenerative medicine, or even through the whole life process, mechanical signaling cascades and cellular mechanical responses in mechanobiology are of great significance in biomedical research. In recent years, research in the field of mechanobiology has undergone remarkable development. Several scientific consortia around the world have been analyzing mechanobiological processes from different perspectives, aiming to gain insights into the regulatory mechanisms by which mechanical factors affect cell fate determination. In this article, we summarized and reviewed the topics that have attracted more research interests in recent years in the field of mechanobiology, for example, arterial blood vessels, stem cell, and ion channel. We also discussed the potential trends that may emerge, such as nuclear deformation, fibrous extracellular matrix, tumor mechanobiology, cellular mechanotransduction, and piezo ion channels. In addition, we put forward new ideas concerning the limitations of mechanism research and the importance of big data analysis and mining in this field, thereby providing objective support and a systematic framework for grasping the hot research topics and exploring new research directions in the field of mechanobiology.

Tight Regulation of Mechanotransducer Proteins Distinguishes the Response of Adult Multipotent Mesenchymal Cells on PBCE-Derivative Polymer Films with Different Hydrophilicity and Stiffness

Mechanotransduction is a molecular process by which cells translate physical stimuli exerted by the external environment into biochemical pathways to orchestrate the cellular shape and function. Even with the advancements in the field, the molecular events leading to the signal cascade are still unclear. The current biotechnology of tissue engineering offers the opportunity to study in vitro the effect of the physical stimuli exerted by biomaterial on stem cells and the mechanotransduction pathway involved in the process. Here, we cultured multipotent human mesenchymal/stromal cells (hMSCs) isolated from bone marrow (hBM-MSCs) and adipose tissue (hASCs) on films of poly(butylene 1,4-cyclohexane dicarboxylate) (PBCE) and a PBCE-based copolymer containing 50 mol% of butylene diglycolate co-units (BDG50), to intentionally tune the surface hydrophilicity and the stiffness (PBCE = 560 Mpa; BDG50 = 94 MPa). We demonstrated the activated distinctive mechanotransduction pathways, resulting in the acquisition of an elongated shape in hBM-MSCs on the BDG50 film and in maintaining the canonical morphology on the PBCE film. Notably, hASCs acquired a new, elongated morphology on both the PBCE and BDG50 films. We found that these events were mainly due to the differences in the expression of Cofilin1, Vimentin, Filamin A, and Talin, which established highly sensitive machinery by which, rather than hASCs, hBM-MSCs distinguished PBCE from BDG50 films.

Mechanobiology in Cells and Tissues

This Editorial is a comment on the success of the Special Issue "Mechanobiology in Cells and Tissues" published in the International Journal of Molecular Sciences [...].