Dynamic mechanobiology of cardiac cells and tissues: Current status and future perspective

Cellular Alignment and Matrix Stiffening Induced Changes in Human Induced Pluripotent Stem Cell Derived Cardiomyocytes

Biological processes are inherently dynamic, necessitating biomaterial platforms capable of spatiotemporal control over cellular organization and matrix stiffness for accurate study of tissue development, wound healing, and disease. However, most in vitro platforms remain static. In this study, a dynamic biomaterial platform comprising a stiffening hydrogel is introduced and achieved through a stepwise approach of addition followed by light-mediated crosslinking, integrated with an elastomeric substrate featuring strain-responsive lamellar surface patterns. Employing this platform, the response of human induced pluripotent stem cell-derived cardiomyocytes (hIPSC-CMs) is investigated to dynamic stiffening from healthy to fibrotic tissue stiffness. The results demonstrate that culturing hIPSC-CMs on physiologically relevant healthy stiffness significantly enhances their function, as evidenced by increased sarcomere fraction, wider sarcomere width, significantly higher connexin-43 content, and elevated cell beating frequency compared to cells cultured on fibrotic matrix. Conversely, dynamic matrix stiffening negatively impacts hIPSC-CM function, with earlier stiffening events exerting a more pronounced hindering effect. These findings provide valuable insights into material-based approaches for addressing existing challenges in hIPSC-CM maturation and have broader implications across various tissue models, including muscle, tendon, nerve, and cornea, where both cellular alignment and matrix stiffening play pivotal roles in tissue development and regeneration.

Tunable Viscoelasticity of Alginate Hydrogels via Serial Autoclaving

Alginate hydrogels are widely used as biomaterials for cell culture and tissue engineering due to their biocompatibility and tunable mechanical properties. Reducing alginate molecular weight is an effective strategy for modulating hydrogel viscoelasticity and stress relaxation behavior, which can significantly impact cell spreading and fate. However, current methods like gamma irradiation to produce low molecular weight alginates suffer from high cost and limited accessibility. Here, a facile and cost-effective approach to reduce alginate molecular weight in a highly controlled manner using serial autoclaving is presented. Increasing the number of autoclave cycles results in proportional reductions in intrinsic viscosity, hydrodynamic radius, and molecular weight of the polymer while maintaining its chemical composition. Hydrogels fabricated from mixtures of the autoclaved alginates exhibit tunable mechanical properties, with inclusion of lower molecular weight alginate leading to softer gels with faster stress relaxation behaviors. The method is demonstrated by establishing how viscoelastic relaxation affects the spreading of encapsulated fibroblasts and glioblastoma cells. Results establish repetitive autoclaving as an easily accessible technique to generate alginates with a range of molecular weights and to control the viscoelastic properties of alginate hydrogels, and demonstrate utility across applications in mechanobiology, tissue engineering, and regenerative medicine.

Targeted therapy with polymeric nanoparticles in PBRM1-mutant biliary tract cancers: Harnessing DNA damage repair mechanisms

Biliary tract cancers (BTCs) are aggressive malignancies with a dismal prognosis that require intensive targeted therapy. Approximately 10 % of BTCs have PBRM1 mutations, which impede DNA damage repair pathways and make cancer cells more susceptible to DNA-damaging chemicals. This review focus on development of poly(lactic-co-glycolic acid) (PLGA)-based nanoparticles targeting delivery system to selectively deliver chemotherapy into PBRM1-deficient BTC cells. These nanoparticles improve therapy efficacy by increasing medication targeting and retention at tumour locations. In preclinical studies, pharmacokinetic profile of this nanoparticle was encouraging and supported its ability to achieve extended circulation time with high drug accumulation in tumor. The review also highlights potential of Pou3F3:I54N to expedite bioassays for patient selection in BTC targeted therapies.

Recent advances in cancer detection using dynamic, stimuli-responsive supramolecular chemosensors. a focus review

In current chemistry, supramolecular materials that respond to a wide variety of external stimuli, such as solvents, temperature, light excitation, pH, and mechanical forces (pressure, stress, strain, and tension), have attracted considerable attention; for example, we have developed cyclodextrins, cucurbiturils, pillararenes, calixarenes, crown ether-based chemical sensors, or chemosensors. These supramolecular chemosensors have potential applications in imaging, probing, and cancer detection. Recently, we focused on pressure, particularly solution-state hydrostatic pressure, from the viewpoint of cancer therapy. This Mini Review summarizes (i) why hydrostatic pressure is important, particularly in biology, and (ii) what we can do using hydrostatic pressure stimulation.

Dual color optogenetic tool enables heart arrest, bradycardic, and tachycardic pacing in Drosophila melanogaster

In order to facilitate cardiovascular research to develop non-invasive optical heart pacing methods, we have generated a double-transgenic Drosophila melanogaster (fruit fly) model suitable for optogenetic pacing. We created a fly stock with both excitatory H134R-ChR2 and inhibitory eNpHR2.0 opsin transgenes. Opsins were expressed in the fly heart using the Hand-GAL4 driver. Here we describe Hand > H134R-ChR2; eNpHR2.0 model characterization including bi-directional heart control (activation and inhibition) upon illumination of light with distinct wavelengths. Optical control and real-time visualization of the heart function were achieved non-invasively using an integrated light stimulation and optical coherence microscopy (OCM) system. OCM produced high-speed and high-resolution imaging; simultaneously, the heart function was modulated by blue (470 nm) or red (617 nm) light pulses causing tachycardia, bradycardia and restorable cardiac arrest episodes in the same animal. The irradiance power levels and illumination schedules were optimized to achieve successful non-invasive bi-directional heart pacing in Drosophila larvae and pupae.

Dynamic control of contractile resistance to iPSC-derived micro-heart muscle arrays

Many types of cardiovascular disease are linked to the mechanical forces placed on the heart. However, our understanding of how mechanical forces exactly affect the cellular biology of the heart remains incomplete. In vitro models based on cardiomyocytes derived from human induced pluripotent stem cells (iPSC-CM) enable researchers to develop medium to high-throughput systems to study cardiac mechanobiology at the cellular level. Previous models have been developed to enable the study of mechanical forces, such as cardiac afterload. However, most of these models require exogenous extracellular matrix (ECM) to form cardiac tissues. Recently, a system was developed to simulate changes in afterload by grafting ECM-free micro-heart muscle arrays to elastomeric substrates of discrete stiffnesses. In the present study, we extended this system by combining the elastomer-grafted tissue arrays with a magnetorheological elastomeric substrate. This system allows iPSC-CM based micro-heart muscle arrays to experience dynamic changes in contractile resistance to mimic dynamically altered afterload. Acute changes in substrate stiffness led to acute changes in the calcium dynamics and contractile forces, illustrating the system's ability to dynamically elicit changes in tissue mechanics by dynamically changing contractile resistance.

Engineered tissue geometry and Plakophilin-2 regulate electrophysiology of human iPSC-derived cardiomyocytes

Engineered heart tissues have been created to study cardiac biology and disease in a setting that more closely mimics in vivo heart muscle than 2D monolayer culture. Previously published studies suggest that geometrically anisotropic micro-environments are crucial for inducing "in vivo like" physiology from immature cardiomyocytes. We hypothesized that the degree of cardiomyocyte alignment and prestress within engineered tissues is regulated by tissue geometry and, subsequently, drives electrophysiological development. Thus, we studied the effects of tissue geometry on electrophysiology of micro-heart muscle arrays (μHM) engineered from human induced pluripotent stem cells (iPSCs). Elongated tissue geometries elicited cardiomyocyte shape and electrophysiology changes led to adaptations that yielded increased calcium intake during each contraction cycle. Strikingly, pharmacologic studies revealed that a threshold of prestress and/or cellular alignment is required for sodium channel function, whereas L-type calcium and rapidly rectifying potassium channels were largely insensitive to these changes. Concurrently, tissue elongation upregulated sodium channel (NaV1.5) and gap junction (Connexin 43, Cx43) protein expression. Based on these observations, we leveraged elongated μHM to study the impact of loss-of-function mutation in Plakophilin 2 (PKP2), a desmosome protein implicated in arrhythmogenic disease. Within μHM, PKP2 knockout cardiomyocytes had cellular morphology similar to what was observed in isogenic controls. However, PKP2-/- tissues exhibited lower conduction velocity and no functional sodium current. PKP2 knockout μHM exhibited geometrically linked upregulation of sodium channel but not Cx43, suggesting that post-translational mechanisms, including a lack of ion channel-gap junction communication, may underlie the lower conduction velocity observed in tissues harboring this genetic defect. Altogether, these observations demonstrate that simple, scalable micro-tissue systems can provide the physiologic stresses necessary to induce electrical remodeling of iPS-CM to enable studies on the electrophysiologic consequences of disease-associated genomic variants.

The Impact of Mechanical Cues on the Metabolomic and Transcriptomic Profiles of Human Dermal Fibroblasts Cultured in Ultrashort Self-Assembling Peptide 3D Scaffolds

Cells' interactions with their microenvironment influence their morphological features and regulate crucial cellular functions including proliferation, differentiation, metabolism, and gene expression. Most biological data available are based on in vitro two-dimensional (2D) cellular models, which fail to recapitulate the three-dimensional (3D) in vivo systems. This can be attributed to the lack of cell-matrix interaction and the limitless access to nutrients and oxygen, in contrast to in vivo systems. Despite the emergence of a plethora of 3D matrices to address this challenge, there are few reports offering a proper characterization of these matrices or studying how the cell-matrix interaction influences cellular metabolism in correlation with gene expression. In this study, two tetrameric ultrashort self-assembling peptide sequences, FFIK and FIIK, were used to create in vitro 3D models using well-described human dermal fibroblast cells. The peptide sequences are derived from naturally occurring amino acids that are capable of self-assembling into stable hydrogels without UV or chemical cross-linking. Our results showed that 2D cultured fibroblasts exhibited distinct metabolic and transcriptomic profiles compared to 3D cultured cells. The observed changes in the metabolomic and transcriptomic profiles were closely interconnected and influenced several important metabolic pathways including the TCA cycle, glycolysis, MAPK signaling cascades, and hemostasis. Data provided here may lead to clearer insights into the influence of the surrounding microenvironment on human dermal fibroblast metabolic patterns and molecular mechanisms, underscoring the importance of utilizing efficient 3D in vitro models to study such complex mechanisms.

Toward the Next Generation of Neural Iontronic Interfaces

Neural interfaces are evolving at a rapid pace owing to advances in material science and fabrication, reduced cost of scalable complementary metal oxide semiconductor (CMOS) technologies, and highly interdisciplinary teams of researchers and engineers that span a large range from basic to applied and clinical sciences. This study outlines currently established technologies, defined as instruments and biological study systems that are routinely used in neuroscientific research. After identifying the shortcomings of current technologies, such as a lack of biocompatibility, topological optimization, low bandwidth, and lack of transparency, it maps out promising directions along which progress should be made to achieve the next generation of symbiotic and intelligent neural interfaces. Lastly, it proposes novel applications that can be achieved by these developments, ranging from the understanding and reproduction of synaptic learning to live-long multimodal measurements to monitor and treat various neuronal disorders.

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 [...].