Mechanics in the nervous system: From development to disease

IoT-enabled real-time health monitoring system for adolescent physical rehabilitation

This study aims to develop an intelligent system leveraging Internet of Thing (IoT) technology to enhance the precision of youth physical training monitoring and improve training outcomes. A wearable device incorporating Micro Electro Mechanical Systems (MEMS) sensors is integrated to collect real-time motion data. Advanced signal processing and filtering techniques are employed to minimize noise interference and improve data accuracy. A particle swarm optimization support vector machine (PSO-SVM) algorithm is utilized to classify motion patterns. To evaluate the system's performance, experiments were conducted to assess motion pattern recognition accuracy, response time, real-time analysis capabilities, and system stability and capacity. The methods we use and the data we collect are from public datasets, do not involve privacy protection for adolescents, and have been approved by the institutional ethics committee. The system demonstrated a motion pattern recognition accuracy exceeding 95% and a response time consistently below 250 ms under various network conditions. Practical applications revealed the system's effectiveness in health monitoring, leading to improved physical fitness and positive rehabilitation outcomes for adolescent patients. This study offers an innovative digital solution for adolescent physical training and health monitoring. The system's strong application potential and valuable insights contribute to the advancement of related research.

Altered extracellular matrix structure and elevated stiffness in a brain organoid model for disease

The viscoelastic properties of tissues influence their morphology and cellular behavior, yet little is known about changes in these properties during brain malformations. Lissencephaly, a severe cortical malformation caused by LIS1 mutations, results in a smooth cortex. Here, we show that human-derived brain organoids with LIS1 mutation exhibit increased stiffness compared to controls at multiple developmental stages. This stiffening correlates with abnormal extracellular matrix (ECM) expression and organization, as well as elevated water content, measured by diffusion-weighted MRI. Short-term MMP9 treatment reduces both stiffness and water diffusion levels to control values. Additionally, a computational microstructure mechanical model predicts mechanical changes based on ECM organization. These findings suggest that LIS1 plays a critical role in ECM regulation during brain development and that its mutation leads to significant viscoelastic alterations.

Mechanical stress connects cortical folding to fiber organization in the developing brain

During development of the gyrencephalic brain, both the formation of cortical folds and the establishment of axonal tracts require large, coordinated mechanical deformations. Cortical folding enables a high ratio of cortical surface area to brain volume, which is thought to enhance overall processing power. Meanwhile, a complex network of axonal connections facilitates communication between distant brain regions. The mechanisms underlying the formation of brain folds and axon tract organization remain widely debated. However, evidence emerging from measurements of mechanical stress, combined with physical and mathematical models, suggests that constrained cortical expansion generates folds via mechanical instability. In this opinion article, we highlight recent models and experimental data suggesting that mechanical stress induced by cortical folding also mediates axonal growth. We propose a key role for mechanics in establishing brain morphology and the organization of white matter fascicles of the mature brain.

Naturally occurring, rostrally conjoining chicken twins attempt to make a forebrain

Conjoined twinning is a special case of monozygotic, monoamniotic twinning. Human conjoined twinning, and vertebrate conjoined twinning in general, is a very rare phenomenon. It has been suggested that the risk of conjoined twinning increases with some medication and upon assisted reproduction. Survival rates are low. When conjoined twins occur in the chicken, they most often present with fused heads, anatomically unrecognisable brains and two normal bodies. Recent studies suggested that forebrain, midbrain and rostral hindbrain identities are established in the early epiblast before neural induction and independent from caudal hindbrain and spinal cord identities. Therefore, it is unclear whether in conjoined twins, the aberrant brain anatomy is a result of the rostral fusion, or whether the brains failed to develop in the first place. Here, we collected conjoined twins as they spontaneously appeared in eggs incubated for stages HH4 (late primitive steak stage) to HH13 (early pharyngula). The twinned embryos and stage-matched normal embryos were analysed for the expression of the rostral epiblast and forebrain-midbrain marker Otx2 and the ventral forebrain marker Six3. We found normal anatomy and marker gene expression that lasted up to stage HH9. By HH12-13, the brain anatomy had deteriorated, but marker genes remained expressed. This suggests that the fusing embryos attempted to generate a brain including the forebrain. Besides addressing forebrain development, our work for the first time provides a time frame to study the mechanisms underlying the interaction and fusion of conjoined twins, which will pave the way to a better understanding and management of risk factors in humans.

Measurement force, speed, and postmortem time affect the ratio of CNS gray-to-white-matter elasticity

For several decades, many attempts have been made to characterize the mechanical properties of gray and white matter, which constitute the two main compartments of the central nervous system, with various methods and contradictory results. In particular, the ratio of gray-to-white-matter elasticity is sometimes larger than 1 and sometimes smaller; the reason for this apparent discrepancy is currently unknown. Here, we exploited atomic force microscopy-based indentation measurements to systematically investigate how the measurement force, measurement speed, postmortem interval, and temperature affect the measured elasticity of spinal cord tissue and, in particular, the ratio of gray-to-white-matter elasticity (Kg/Kw). Within the explored parameter space, increasing measurement force and speed increased the measured elasticity of both gray and white matter. However, Kg/Kw declined from values as high as ∼5 at low forces and speeds to ∼1 for high forces and speeds. Kg/Kw also strongly depended on the anatomical plane in which the measurements were conducted and was considerably higher in transverse sections compared with longitudinal sections. Furthermore, the postmortem interval impacted both the absolute measured tissue elasticity and Kg/Kw. Gray matter elasticity started decreasing ∼3 h postmortem until reaching a plateau after ∼6 h. In contrast, white matter elasticity started declining from the beginning of the measurements until ∼6 h postmortem, when it also leveled off. As a result, Kg/Kw increased until ∼6 h postmortem before stabilizing. Between 20 and 38°C, both gray and white matter elasticity decreased at a similar rate without affecting Kg/Kw. We have thus identified differences in the response of gray and white matter to varying strains and strain rates, and the postmortem interval, and excluded temperature as a factor affecting Kg/Kw. These differential responses likely contribute to the contradictory results obtained with different methods working in different strain regimes.

Effect of Brief Electrical Stimulation on Cell Biomechanics in Hereditary Sensory Neuropathy

SH-SY5Y neuroblastoma cells are widely used to model neurodegenerative disorders like Alzheimer's, Parkinson's, Huntington's, and Hereditary Sensory Neuropathy type 1A (HSN-1A), a peripheral nerve condition causing axon degeneration and sensory loss. A cell model of HSN-1A is developed by overexpressing wild-type and mutant SPTLC1 genes (C133W, C133Y, V144D). Cells are cultured on plastic and gold substrates, with brief electrical stimulation applied to the gold-grown cells. Atomic force microscopy (AFM) is used to measure Young's modulus, indentation, and energy dissipation. Finite Element Method and non-linear modeling validate the results. In the absence of stimulation, mutant cells show lower stiffness compared to non-transfected cells, indicating a direct biomechanical impact of the mutations. Brief electrical stimulation significantly increases the stiffness of mutant cells, particularly in C133W (99%), C133Y (100%), and V144D (111%) variants, despite the mutations. Energy dissipation of stimulated V144D cells decreases to levels comparable to untreated non-transfected cells. The simulations support the AFM measurements, demonstrating that brief electrical stimulation can partially reverse the biomechanical effects of gene mutations.

The emerging roles of the endoplasmic reticulum in mechanosensing and mechanotransduction

Cells are continuously subjected to physical and chemical cues from the extracellular environment, and sense and respond to mechanical cues via mechanosensation and mechanotransduction. Although the role of the cytoskeleton in these processes is well known, the contribution of intracellular membranes has been long neglected. Recently, it has become evident that various organelles play active roles in both mechanosensing and mechanotransduction. In this Review, we focus on mechanosensitive roles of the endoplasmic reticulum (ER), the functions of which are crucial for maintaining cell homeostasis. We discuss the effects of mechanical stimuli on interactions between the ER, the cytoskeleton and other organelles; the role of the ER in intracellular Ca2+ signalling via mechanosensitive channels; and how the unfolded protein response and lipid homeostasis contribute to mechanosensing. The expansive structure of the ER positions it as a key intracellular communication hub, and we additionally explore how this may be leveraged to transduce mechanical signals around the cell. By synthesising current knowledge, we aim to shed light on the emerging roles of the ER in cellular mechanosensing and mechanotransduction.

Cell-generated mechanical forces play a role in epileptogenesis after injury

Traumatic brain injury (TBI) is associated with a significantly increased risk of epilepsy. One of the consequences of severe TBI is progressive brain atrophy, which is frequently characterized by organized tissue retraction. Retraction is an active process synchronized by mechanical interactions between surviving cells. This results in unbalanced mechanical forces acting on surviving neurons, potentially activating mechanotransduction and leading to hyperexcitability. This novel mechanism of epileptogenesis was examined in organotypic hippocampal cultures, which develop spontaneous seizure-like activity in vitro. Cell-generated forces in this model resulted in contraction of hippocampal tissue. Artificial imbalances in mechanical forces were introduced by placing cultured slices on surfaces with adhesive and non-adhesive regions. This modeled disbalance in mechanical forces that may occur in the brain after trauma. Portions of the slices that were not stabilized by substrate adhesion underwent increased contraction and compaction, revealing the presence of cell-generated forces capable of shaping tissue geometry. Changes in tissue geometry were followed by excitability changes that were specific to hippocampal sub-region and orientation of contractile forces relative to pyramidal cell apical-basal axis. Results of this study suggest that imbalanced cell-generated forces contribute to development of epilepsy, and that force imbalance may represent a novel mechanism of epileptogenesis after trauma.

Stress landscape of folding brain serves as a map for axonal pathfinding

Understanding the mechanics linking cortical folding and brain connectivity is crucial for both healthy and abnormal brain development. Despite the importance of this relationship, existing models fail to explain how growing axon bundles navigate the stress field within a folding brain or how this bidirectional and dynamic interaction shapes the resulting surface morphologies and connectivity patterns. Here, we propose the concept of "axon reorientation" and formulate a mechanical model to uncover the dynamic multiscale mechanics of the linkages between cortical folding and connectivity development. Simulations incorporating axon bundle reorientation and stress-induced growth reveal potential mechanical mechanisms that lead to higher axon bundle density in gyri (ridges) compared to sulci (valleys). In particular, the connectivity patterning resulting from cortical folding exhibits a strong dependence on the growth rate and mechanical properties of the navigating axon bundles. Model predictions are supported by in vivo diffusion tensor imaging of the human brain.

Physiology and pathophysiology of the retinal neuroglia

Neuroglia of the retina are represented by Müller glia, parenchymal astrocytes, microglia and oligodendrocytes mainly associated with the optic nerve. Müller glia are the most numerous glia, endowed with multiple homeostatic functions and indispensable for the retinal morphofunctional organization. Müller cells integrate retinal neurons into individual functional units (known as retinal columns) and act as a living light guide, transmitting photons to photoreceptors. In pathology, retinal neuroglia undergo complex changes, which include upregulation of neuroprotection, reactive gliosis, and functional asthenia. The balance between all these changes defines the progression and outcome of retinal disorders.

Parallelized Mechanical Stimulation of Neuronal Calcium Through Cell-Internal Nanomagnetic Forces Provokes Lasting Shifts in the Network Activity State

Neurons differentiate mechanical stimuli force and rate to elicit unique functional responses, driving the need for further tools to generate various mechanical stimuli. Here, cell-internal nanomagnetic forces (iNMF) are introduced by manipulating internalized magnetic nanoparticles with an external magnetic field across cortical neuron networks in vitro. Under iNMF, cortical neurons exhibit calcium (Ca2+) influx, leading to modulation of activity observed through Ca2+ event rates. Inhibiting particle uptake or altering nanoparticle exposure time reduced the neuronal response to nanomagnetic forces, exposing the requirement of nanoparticle uptake to induce the Ca2+ response. In highly active cortical networks, iNMF robustly modulates synchronous network activity, which is lasting and repeatable. Using pharmacological blockers, it is shown that iNMF activates mechanosensitive ion channels to induce the Ca2+ influx. Then, in contrast to transient mechanically evoked neuronal activity, iNMF activates Ca2+-activated potassium (KCa) channels to stabilize the neuronal membrane potential and induce network activity shifts. The findings reveal the potential of magnetic nanoparticle-mediated mechanical stimulation to modulate neuronal circuit dynamics, providing insights into the biophysics of neuronal computation.

Multimodal Characterization of Cortical Neuron Response to Permanent Magnetic Field Induced Nanomagnetic Force Maps

Nanomagnetic forces deliver precise mechanical cues to biological systems through the remote pulling of magnetic nanoparticles under a permanent magnetic field. Cortical neurons respond to nanomagnetic forces with cytosolic calcium influx and event rate shifts. However, the underlying consequences of nanomagnetic force modulation on cortical neurons remain to be elucidated. Here, we integrate electrophysiological and optical recording modalities with nanomagnetic forces to characterize the in vitro functional response to mechanical cues. Neurons exposed to chitosan functionalized magnetic nanoparticles for 24 h and then exposed to magnetic fields capable of generating forces of 2-160 pN present elevated cytosolic calcium in neurons and a time-dynamic electrophysiological spike rate and magnitude response. Extracellular recordings with microelectrode arrays revealed a 2-8 pN force-specific increase in electrophysiological spiking with a trend in reduced activity following 2 min of continuous force exposure. Nanomagnetic forces in the 16-160 pN range produced increased electrophysiological activity and remained excited for up to 4 h under continuous stimulation before silencing. Furthermore, the neuronal response to nanomagnetic forces at 16-160 pN can be electrophysiologically mediated without calcium influx by altering the magnetic nanoparticle-neuron interactions. These results demonstrate that low pN nanomagnetic forces mediate neuronal function and suggest that magnetic nanoparticle interactions and force magnitudes can be harnessed to provoke different responses in cortical neurons.

Physical modulation and peripheral nerve regeneration: a literature review

Peripheral nerve injury (PNI) usually causes severe motor, sensory and autonomic dysfunction. In addition to direct surgical repair, rehabilitation exercises, and traditional physical stimuli, for example, electrical stimulation, have been applied in promoting the clinical recovery of PNI for a long time but showed low efficiency. Recently, significant progress has been made in new physical modulation to promote peripheral nerve regeneration. We hereby review current progress on the mechanism of peripheral nerve regeneration after injury and summarize the new findings and evidence for the application of physical modulation, including electrical stimulation, light, ultrasound, magnetic stimulation, and mechanical stretching in experimental studies and the clinical treatment of patients with PNI.

Invited Review for 20th Anniversary Special Issue of PLRev "AI for Mechanomedicine"

Mechanomedicine is an interdisciplinary field that combines different areas including biomechanics, mechanobiology, and clinical applications like mechanodiagnosis and mechanotherapy. The emergence of artificial intelligence (AI) has revolutionized mechanomedicine, providing advanced tools to analyze the complex interactions between mechanics and biology. This review explores how AI impacts mechanomedicine across four key aspects, i.e., biomechanics, mechanobiology, mechanodiagnosis, and mechanotherapy. AI improves the accuracy of biomechanical characterizations and models, deepens the understanding of cellular mechanotransduction pathways, and enables early disease detection through mechanodiagnosis. In addition, AI optimizes mechanotherapy that targets biomechanical features and mechanobiological markers by personalizing treatment strategies based on real-time patient data. Even with these advancements, challenges still exist, particularly in data quality and the ethical integration into AI in clinical practice. The integration of AI with mechanomedicine offers transformative potential, enabling more accurate diagnostics and personalized treatments, and discovering novel mechanobiological pathways.

Viscoelastic High-Molecular-Weight Hyaluronic Acid Hydrogels Support Rapid Glioblastoma Cell Invasion with Leader-Follower Dynamics

Hyaluronic acid (HA), the primary component of brain extracellular matrix, is increasingly used to model neuropathological processes, including glioblastoma (GBM) tumor invasion. While elastic hydrogels based on crosslinked low-molecular-weight (LMW) HA are widely exploited for this purpose and have proven valuable for discovery and screening, brain tissue is both viscoelastic and rich in high-MW (HMW) HA, and it remains unclear how these differences influence invasion. To address this question, hydrogels comprised of either HMW (1.5 MDa) or LMW (60 kDa) HA are introduced, characterized, and applied in GBM invasion studies. Unlike LMW HA hydrogels, HMW HA hydrogels relax stresses quickly, to a similar extent as brain tissue, and to a greater extent than many conventional HA-based scaffolds. GBM cells implanted within HMW HA hydrogels invade much more rapidly than in their LMW HA counterparts and exhibit distinct leader-follower dynamics. Leader cells adopt dendritic morphologies similar to invasive GBM cells observed in vivo. Transcriptomic, pharmacologic, and imaging studies suggest that leader cells exploit hyaluronidase, an enzyme strongly enriched in human GBMs, to prime a path for followers. This study offers new insight into how HA viscoelastic properties drive invasion and argues for the use of highly stress-relaxing materials to model GBM.

Cellular signaling pathways in the nervous system activated by various mechanical and electromagnetic stimuli

Mechanical stimuli, such as stretch, shear stress, or compression, activate a range of biomolecular responses through cellular mechanotransduction. In the nervous system, studies on mechanical stress have highlighted key pathophysiological mechanisms underlying traumatic injury and neurodegenerative diseases. However, the biomolecular pathways triggered by mechanical stimuli in the nervous system has not been fully explored, especially compared to other body systems. This gap in knowledge may be due to the wide variety of methods and definitions used in research. Additionally, as mechanical stimulation techniques such as ultrasound and electromagnetic stimulation are increasingly utilized in psychological and neurorehabilitation treatments, it is vital to understand the underlying biological mechanisms in order to develop accurate pathophysiological models and enhance therapeutic interventions. This review aims to summarize the cellular signaling pathways activated by various mechanical and electromagnetic stimuli with a particular focus on the mammalian nervous system. Furthermore, we briefly discuss potential cellular mechanosensors involved in these processes.

Breast Tumor Cell Survival and Morphology in a Brain-like Extracellular Matrix Depends on Matrix Composition and Mechanical Properties

Triple-negative breast cancer (TNBC) is the most invasive type of breast cancer with high risk of brain metastasis. To better understand interactions between breast tumors with the brain extracellular matrix (ECM), a 3D cell culture model is implemented using a thiolated hyaluronic acid (HA-SH) based hydrogel. The latter is used as HA represents a major component of brain ECM. Melt-electrowritten (MEW) scaffolds of box- and triangular-shaped polycaprolactone (PCL) micro-fibers for hydrogel reinforcement are utilized. Two different molecular weight HA-SH materials (230 and 420 kDa) are used with elastic moduli of 148 ± 34 Pa (soft) and 1274 ± 440 Pa (stiff). Both hydrogels demonstrate similar porosities. The different molecular weight of HA-SH, however, significantly changes mechanical properties, e.g., stiffness, nonlinearity, and hysteresis. The breast tumor cell line MDA-MB-231 forms mainly multicellular aggregates in both HA-SH hydrogels but sustains high viability (75%). Supplementation of HA-SH hydrogels with ECM components does not affect gene expression but improves cell viability and impacts cellular distribution and morphology. The presence of other brain cell types further support numerous cell-cell interactions with tumor cells. In summary, the present 3D cell culture model represents a novel tool establishing a disease cell culture model in a systematic way.

Real-time monitoring of intracellular biochemical response in locally stretched single cell by a nanosensor

Mechanotransduction is the essential process that cells convert mechanical force into biochemical responses, and electrochemical sensor stands out from existing techniques by providing quantitative and real-time information about the biochemical signals during cellular mechanotransduction. However, the intracellular biochemical response evoked by mechanical force has been poorly monitored. In this paper, we report a method to apply local stretch on single cell and simultaneously monitor the ensuing intracellular biochemical signals. Specifically, a ferromagnetic micropipette was fabricated to locally stretch a single cell labeled with Fe3O4 nanoparticles under the external magnetic field, and the SiC@Pt nanowire electrode (SiC@Pt NWE) was inserted into the cell to monitor the intracellular hydrogen peroxide (H2O2) production induced by the local stretch. As a proof of concept, this work quantitatively investigated the elevated amount of H2O2 levels in single endothelial cell under different stretching amplitudes. This work puts forward a new research modality to manipulate and monitor the mechanotransduction at the single-cell level.

The Networking Brain: How Extracellular Matrix, Cellular Networks, and Vasculature Shape the In Vivo Mechanical Properties of the Brain

Mechanically, the brain is characterized by both solid and fluid properties. The resulting unique material behavior fosters proliferation, differentiation, and repair of cellular and vascular networks, and optimally protects them from damaging shear forces. Magnetic resonance elastography (MRE) is a noninvasive imaging technique that maps the mechanical properties of the brain in vivo. MRE studies have shown that abnormal processes such as neuronal degeneration, demyelination, inflammation, and vascular leakage lead to tissue softening. In contrast, neuronal proliferation, cellular network formation, and higher vascular pressure result in brain stiffening. In addition, brain viscosity has been reported to change with normal blood perfusion variability and brain maturation as well as disease conditions such as tumor invasion. In this article, the contributions of the neuronal, glial, extracellular, and vascular networks are discussed to the coarse-grained parameters determined by MRE. This reductionist multi-network model of brain mechanics helps to explain many MRE observations in terms of microanatomical changes and suggests that cerebral viscoelasticity is a suitable imaging marker for brain disease.

Cytoskeleton-modulating nanomaterials and their therapeutic potentials

The cytoskeleton, an intricate network of protein fibers within cells, plays a pivotal role in maintaining cell shape, enabling movement, and facilitating intracellular transport. Its involvement in various pathological states, ranging from cancer proliferation and metastasis to the progression of neurodegenerative disorders, underscores its potential as a target for therapeutic intervention. The exploration of nanotechnology in this realm, particularly the use of nanomaterials for cytoskeletal modulation, represents a cutting-edge approach with the promise of novel treatments. Inorganic nanomaterials, including those derived from gold, metal oxides, carbon, and black phosphorus, alongside organic variants such as peptides and proteins, are at the forefront of this research. These materials offer diverse mechanisms of action, either by directly interacting with cytoskeletal components or by influencing cellular signaling pathways that, in turn, modulate the cytoskeleton. Recent advancements have introduced magnetic field-responsive and light-responsive nanomaterials, which allow for targeted and controlled manipulation of the cytoskeleton. Such precision is crucial in minimizing off-target effects and enhancing therapeutic efficacy. This review explores the importance of research into cytoskeleton-targeting nanomaterials for developing therapeutic interventions for a range of diseases. It also addresses the progress made in this field, the challenges encountered, and future directions for using nanomaterials to modulate the cytoskeleton. The continued exploration of nanomaterials for cytoskeleton modulation holds great promise for advancing therapeutic strategies against a broad spectrum of diseases, marking a significant step forward in the intersection of nanotechnology and medicine.

Mechanical and Functional Responses in Astrocytes under Alternating Deformation Modes Using Magneto-Active Substrates

This work introduces NeoMag, a system designed to enhance cell mechanics assays in substrate deformation studies. NeoMag uses multidomain magneto-active materials to mechanically actuate the substrate, transmitting reversible mechanical cues to cells. The system boasts full flexibility in alternating loading substrate deformation modes, seamlessly adapting to both upright and inverted microscopes. The multidomain substrates facilitate mechanobiology assays on 2D and 3D cultures. The integration of the system with nanoindenters allows for precise evaluation of cellular mechanical properties under varying substrate deformation modes. The system is used to study the impact of substrate deformation on astrocytes, simulating mechanical conditions akin to traumatic brain injury and ischemic stroke. The results reveal local heterogeneous changes in astrocyte stiffness, influenced by the orientation of subcellular regions relative to substrate strain. These stiffness variations, exceeding 50% in stiffening and softening, and local deformations significantly alter calcium dynamics. Furthermore, sustained deformations induce actin network reorganization and activate Piezo1 channels, leading to an initial increase followed by a long-term inhibition of calcium events. Conversely, fast and dynamic deformations transiently activate Piezo1 channels and disrupt the actin network, causing long-term cell softening. These findings unveil mechanical and functional alterations in astrocytes during substrate deformation, illustrating the multiple opportunities this technology offers.

Viscoelastic high-molecular-weight hyaluronic acid hydrogels support rapid glioblastoma cell invasion with leader-follower dynamics

Hyaluronic acid (HA), the primary component of brain extracellular matrix, is increasingly used to model neuropathological processes, including glioblastoma (GBM) tumor invasion. While elastic hydrogels based on crosslinked low-molecular-weight (LMW) HA are widely exploited for this purpose and have proven valuable for discovery and screening, brain tissue is both viscoelastic and rich in high-MW (HMW) HA, and it remains unclear how these differences influence invasion. To address this question, hydrogels comprised of either HMW (1.5 MDa) or LMW (60 kDa) HA are introduced, characterized, and applied in GBM invasion studies. Unlike LMW HA hydrogels, HMW HA hydrogels relax stresses quickly, to a similar extent as brain tissue, and to a greater extent than many conventional HA-based scaffolds. GBM cells implanted within HMW HA hydrogels invade much more rapidly than in their LMW HA counterparts and exhibit distinct leader-follower dynamics. Leader cells adopt dendritic morphologies, similar to invasive GBM cells observed in vivo. Transcriptomic, pharmacologic, and imaging studies suggest that leader cells exploit hyaluronidase, an enzyme strongly enriched in human GBMs, to prime a path for followers. This study offers new insight into how HA viscoelastic properties drive invasion and argues for the use of highly stress-relaxing materials to model GBM.