Mechanisms Of Fibrillation Research Articles

“Pharmacological” analysis of atrial fibrillation maintenance mechanism: reentry, wavelets, or focal?

The primary electrophysiological mechanism of atrial fibrillation (AF) maintenance is poorly defined. AF mapping studies readily record focal activations (defining them as focal sources or breakthroughs) and “incomplete reentries” (defining them as reentries or would-be-reentries) but do not or rarely detect complete circular activations. Electrophysiological alterations induced by anti-AF drugs before AF cardioversion may help delineate the mechanism of AF maintenance. Cardioversion of AF by antiarrhythmic drugs is associated with prolongation of the AF cycle length and temporal excitable gap (t-EG), resulting in improvement in AF organization (AF-org), and with or without alterations in the refractory period, conduction velocity and wavelength. Such electrophysiological pattern is conceivable with termination of a single focal source but not a single reentry (Class III agents do not increase reentrant t-EG). Yet, a single focal source and multiple focal sources are plausible as the primary mechanism of AF maintenance prior drug administration. Improvement in AF-org caused by anti-AF agents before AF cardioversion is coherent with simultaneous multiple random reentries and wavelets. However, simultaneous multiple reentries are unlikely to occur regularly (most of the contemporary AF mapping studies report either a single reentry at a time or no reentry at all), and the ability of random wavelets to maintain AF is speculative. The conducted analysis inclines toward the focal source as the primary mechanism of AF maintenance.

Hypermethylation of Hif3a and Ifltd1 is associated with atrial remodeling in pressure-overload murine model

Atrial remodeling is a major pathophysiological mechanism of atrial fibrillation (AF). Atrial remodeling progresses with aging and background diseases, including hypertension, heart failure, and AF itself. However, its mechanism of action and reversibility have not been completely elucidated. In this study, we investigated the involvement of DNA methylation in atrial remodeling. Mice underwent transverse aortic constriction (TAC) to generate a pressure overload model. After 14 days, the TAC-operated mice showed a significant increase in the atrium/body weight ratio and deposition of collagen fibers in the atria. A comprehensive analysis using RNA-sequencing (RNA-Seq) and methyl-CpG-binding domain sequencing (MBD-Seq) in the left atrial tissue identified Hif3a and Ifltd1 as showing increased DNA methylation in their promoter regions and decreased RNA expression. In addition, we created a transient pressure overload model by removing the aortic constriction 3 or 7 days after the initial TAC procedure (R3 or R7 groups). A reduction in RNA expression was achieved at R3 for Hif3a and at R7 for Ifltd1. Heterozygous Dnmt1 gene-targeting mice (Dnmt1mut) showed disappearance of the reduction in RNA expression and an increase in the atrium/body weight ratio. Altogether, DNA methylation contributed to at least part of atrial remodeling in the pressure overload mouse model.

Measuring the biomechanical properties of cell-derived fibronectin fibrils.

Embryonic development, wound healing, and organogenesis all require assembly of the extracellular matrix protein fibronectin (FN) into insoluble, viscoelastic fibrils. FN fibrils mediate cell migration, force generation, angiogenic sprouting, and collagen deposition. While the critical role of FN fibrils has long been appreciated, we still have an extremely poor understanding of their mechanical properties and how these mechanical properties facilitate cellular responses. Here, we demonstrate the development of a system to probe the mechanics of cell-derived FN fibrils and present quantified mechanical properties of these fibrils. We demonstrate that: fibril elasticity can be classified into three phenotypes: linearly elastic, strain-hardening, or nonlinear with a "toe" region; fibrils exhibit pre-conditioning, with nonlinear "toe" fibrils becoming more linear with repeated stretch and strain-hardened fibrils becoming less linear with repeated stretch; fibrils exhibit an average elastic modulus of roughly 8 MPa; and fibrils exhibit a time-dependent viscoelastic behavior, exhibiting a transition from a stress relaxation response to an inverse stress relaxation response. These findings have a potentially significant impact on our understanding of cellular mechanical responses in fibrotic diseases and embryonic development, where FN fibrils play a major role.

Epidemiology, risk factors and mechanism of breast cancer and atrial fibrillation

Epidemiology, risk factors and mechanism of breast cancer and atrial fibrillation

Maintenance mechanism of paroxysmal atrial fibrillation from the activation occurring within the pulmonary vein: analysis using non-contact mapping.

It is unclear how pulmonary veins (PVs) maintain paroxysmal atrial fibrillation (AF). To clarify the PV's arrhythmogenic role, we examined PV activation sequences during paroxysmal AF. Left superior PV (LSPV) endocardial non-contact mapping was performed after a right PV isolation in 13 paroxysmal AF patients. Activation sequences within the LSPV before and during left-sided PVs ablation were analyzed, and those in complex fractionated atrial electrogram (CFAE) areas were compared with those in non-CFAE areas. CFAEs were observed in the LSPV's proximal half (area; 8.8 ± 3.2cm2) occupying 19.9 ± 6.0% of LSPV. The number of pivoting activations, wave breaks, and fusions over CFAE areas were significantly higher than those over non-CFE areas (25.5 ± 9.3 vs. 4.5 ± 4.8 times/s, p < 0.0001; 9.1 ± 5.3 vs. 1.4 ± 1.8 times/s, p < 0.0001; 13.0 ± 4.6 vs. 5.4 ± 4.4 times/s, p < 0.0001). The conduction velocities in CFAE areas were significantly slower than in non-CFAE areas (0.6 ± 0.2 vs. 1.7 ± 0.8m/s, p < 0.001). After delivery of ablation lesions around the left-sided PVs (13.2 ± 7.4 applications), the PV activation became organized with a loss of CFAE areas, and the frequency of the LSPV's pivoting activation, wave break, and fusion significantly decreased compared to that pre-ablation (7.3 ± 10.9 vs. 30.0 ± 11.6 times/s, p < 0.001; 2.1 ± 5.3 vs. 10.5 ± 6.2 times/s, p < 0.002; 6.0 ± 6.6 vs. 18.4 ± 8.2 times/s, p < 0.001). Subsequently, AF terminated before the left-sided PV isolation in all patients. In conclusion, high-frequency random reentry associated with pivoting activation, wave break, and fusion within the LSPV, observed mostly over CFAE areas, maintained AF. Linear ablation lesions around the PV suppressed random reentry, resulting in the loss of CFAEs and AF termination.

Impact of risk factors on atrial fibrillation types via epicardial adipose tissue computed tomography-based radiomics analysis

Impact of risk factors on atrial fibrillation types via epicardial adipose tissue computed tomography-based radiomics analysis

Abstract 4137249: Left atrial functional reserve predicts recurrence of atrial arrhythmia following catheter ablation in patients with persistent atrial fibrillation

Background: Left atrial (LA) functional remodeling plays an essential role in the pathophysiological mechanisms of atrial fibrillation (AF). LA reservoir strain (LARS) measured by speckle-tracking echocardiography (STE) exhibits acceptable predictive value for recurrent atrial arrhythmia in patients with paroxysmal AF, while its performance in persistent AF remains inconclusive. Recently, LA functional reserve, a novel concept of LA mechanics in response to acute-volume overload, is drawing attention. Research Questions: Are LARS and LA functional reserve associated with recurrent atrial arrhythmia after catheter ablation in patients with persistent AF? Methods: Ninety-two patients who underwent first catheter ablation for persistent AF were included in the study. LARS at rest and LA functional reserve were assessed by STE 1-4 days before catheter ablation. LA functional reserve was calculated as change in LARS after passive leg lifting. Recurrence of arrhythmia was defined as atrial arrhythmia of ≥ 30 seconds duration after a 2-month blanking period. Results: The median values of LARS and LA functional reserve were 14.4 % (interquartile range [IQR] 10.9 to 18.2) and 1.0% (IQR -1.2 to 3.6), respectively. During a mean follow-up of 13.2 ± 9.9 months, 29 (31.5%) patients experienced recurrent AF. When we stratified patients into 2 groups according to LARS and LA functional reserve (below vs. above median values), patients with impaired LA functional reserve (&lt; 1.0%) were at higher risk of AF recurrence (log-rank test p value=0.026), but this was not observed for LARS (Figure). In multivariable Cox proportional hazard analysis, impaired LA functional reserve was associated with recurrent atrial arrhythmia independent of AF risk factors, left ventricular ejection fraction and LARS at rest (adjusted hazard ratio 3.99, p=0.004). Conclusions: Evaluation of LA functional reserve may provide valuable information for optimal patient selection as well as follow-up strategy after catheter ablation in patients with persistent AF.

Exploration of the shared gene signatures and comorbidity mechanisms of primary aldosteronism and atrial fibrillation.

Primary aldosteronism (PA) is a prevalent cause of endocrine hypertension characterized by an excess of aldosterone that can induce proinflammatory, prooxidant and profibrotic effects on the heart. Emerging evidence indicates a heightened incidence of atrial fibrillation (AF) in patients with PA, suggesting a significant association between the two conditions. However, the underlying mechanisms remain unclear. The purpose of this study was to investigate the molecular networks associated with the development of both PA and AF. Datasets were obtained from the Gene Expression Omnibus database. Hub genes were identified by enrichment and protein-protein interaction analysis. These hub genes were subsequently validated via two independent external datasets: GSE60042 (PA microarray dataset) and GSE41177 (AF microarray dataset). Following the identification of shared genes, quantitative real-time polymerase chain reaction (qPCR) was employed to verify the reliability of the dataset and to further confirm the presence of shared genes in clinical samples. The results of the common gene analysis revealed that immune and inflammatory responses may be shared features in the pathophysiology of PA and AF. One hub gene, specifically tumor necrosis factor superfamily member 10 (TNFSF10), was identified through various analyses and subsequently validated via qPCR. Compared with that in healthy controls, the expression level of TNFSF10 was lower in PA patients with AF. Our findings indicate that TNFSF10 may play a role in the pathophysiology of AF complications associated with PA conditions, suggesting that it could serve as a potential target for the diagnosis or treatment of PA patients complicated with AF.

Pathophysiological Mechanisms of Psychosis-Induced Atrial Fibrillation: The Links between Mental Disorder and Arrhythmia.

Atrial fibrillation (AF) is a common phenomenon of sustained arrhythmia leading to heart failure or stroke. Patients with mental disorders (MD), particularly schizophrenia and bipolar disorder, are at a high risk of AF triggered by the dysregulation of the autonomic nervous system, atrial stretch, oxidative stress, inflammation, and electrical or structural remodeling. Moreover, pathophysiological mechanisms underlying MD may also contribute to the genesis of AF. An overactivated hypothalamic-pituitary-adrenal axis, aberrant renin-angiotensin-aldosterone system, abnormal serotonin signaling, disturbed sleep, and genetic/epigenetic factors can adversely alter atrial electrophysiology and structural substrates, leading to the development of AF. In this review, we provide an update of our collective knowledge of the pathophysiological and molecular mechanisms that link MD and AF. Targeting the pathogenic mechanisms of MD-specific AF may facilitate the development of therapeutics that mitigate AF and cardiovascular mortality in this patient population.

Electrographic flow mapping of atrial fibrillation.

A low ceiling of efficacy exists for the treatment of persistent atrial fibrillation via pulmonary vein isolation without adjunctive ablations, which is likely because they do not target an individual patient's specific underlying disease mechanisms. Electrographic flow (EGF) mapping is the first system that reliably displays wavefront propagation through the atria. It is a promising tool for localizing sources of atrial fibrillation, guiding targeted ablation, and visualizing conduction through the atrial substrate. We describe EGF mapping with emphasis on contemporary studies examining map reproducibility and use cases in the preclinical and clinical environment. Animal experiments demonstrated that maps were interpretable across increasingly complex rhythms with pacing during spontaneously persistent atrial fibrillation reliably simulating EGF sources. The FLOW-AF randomized controlled trial showed that source ablation improved outcomes and that EGF map properties may be used to phenotype patients based on their atrial fibrillation mechanisms and recurrence likelihoods. Targeted ablation strategies balance the risks of insufficiently ablating atrial fibrillation triggers with exacerbating disease through additional scar formation. EGF mapping leverages spatiotemporal relationships in voltage to localize sources and quantify substrate health. Further research is needed to optimize phenotyping and treatment efforts.

Methylglyoxal alters collagen fibril nanostiffness and surface potential

Collagen fibrils are fundamental to the mechanical strength and function of biological tissues. However, they are susceptible to changes from non-enzymatic glycation, resulting in the formation of advanced glycation end-products (AGEs) that are not reversible. AGEs accumulate with aging and disease and can adversely impact tissue mechanics and cell-ECM interactions. AGE-crosslinks have been related, on the one hand, to dysregulation of collagen fibril stiffness and damage and, on the other hand, to altered collagen net surface charge as well as impaired cell recognition sites. While prior studies using Kelvin probe force microscopy (KPFM) have shown the effect glycation has on collagen fibril surface potential (i.e., net charge), the combined effect on individual and isolated collagen fibril mechanics, hydration, and surface potential has not been documented. Here, we explore how methylglyoxal (MGO) treatment affects the mechanics and surface potential of individual and isolated collagen fibrils by utilizing atomic force microscopy (AFM) nanoindentation and KPFM. Our results reveal that MGO treatment significantly increases nanostiffness, alters surface potential, and modifies hydration characteristics at the collagen fibril level. These findings underscore the critical impact of AGEs on collagen fibril physicochemical properties, offering insights into pathophysiological mechanical and biochemical alterations with implications for cell mechanotransduction during aging and in diabetes. Statement of significanceCollagen fibrils are susceptible to glycation, the irreversible reaction of amino acids with sugars. Glycation affects the mechanical properties and surface chemistry of collagen fibrils with adverse alterations in biological tissue mechanics and cell-ECM interactions. Current research on glycation, at the level of individual collagen fibrils, is sparse and has focused either on collagen fibril mechanics, with contradicting evidence, or surface potential. Here, we utilized a multimodal approach combining Kelvin probe force (KPFM) and atomic force microscopy (AFM) to examine how methylglyoxal glycation induces structural, mechanical, and surface potential changes on the same individual and isolated collagen fibrils. This approach helps inform structure-function relationships at the level of individual collagen fibrils.

Mineral and cross-linking in collagen fibrils: The mechanical behavior of bone tissue at the nano-scale

The mineralized collagen fibril is the main building block of hard tissues and it directly affects the macroscopic mechanics of biological tissues such as bone. The mechanical behavior of the fibril itself is determined by its structure: the content of collagen molecules, minerals, and cross-links, and the mechanical interactions and properties of these components. Advanced glycation end products (AGEs) form cross-links between tropocollagen molecules within the collagen fibril and are one important factor that is believed to have a major influence on the tissue. For instance, it has been shown that brittleness in bone correlates with increased AGEs densities. However, the underlying nano-scale mechanisms within the mineralized collagen fibril remain unknown. Here, we study the effect of mineral and AGEs cross-linking on fibril deformation and fracture behavior by performing destructive tensile tests using coarse-grained molecular dynamics simulations. Our results demonstrate that after exceeding a critical content of mineral, it induces stiffening of the collagen fibril at high strain levels. We show that mineral morphology and location affect collagen fibril mechanics: The mineral content at which this stiffening occurs depends on the mineral’s location and morphology. Further, both, increasing AGEs density and mineral content lead to stiffening and increased peak stresses. At low mineral contents, the mechanical response of the fibril is dominated by the AGEs, while at high mineral contents, the mineral itself determines fibril mechanics.

A Promising Compound for Green Multiresponsive Materials Based on Acyl Carrier Protein.

A gel that exhibits intrinsically multiple-responsive behavior was prepared from an oligopeptide and studied. ACP(65-74) is an active decapeptide fragment of acyl carrier protein. We investigated 3% w/v ACP(65-74)-NH2 self-healing physical gels in water, glycerol carbonate (GC), and their mixtures. The morphology was investigated by optical, birefringence, and confocal laser scanning microscopy, circular dichroism, Fourier transform infrared, and fluorescence spectroscopy experiments. We found that all samples possess pH responsiveness with fully reversible sol-to-gel transitions. The rheological properties depend on the temperature and solvent composition. The temperature dependence of the gels in water shows a peculiar behavior that is similar to that of thermoresponsive polymer solutions. The results reveal the presence of several β-sheet structures and amyloid aggregates, offering valuable insights into the fibrillation mechanism of amyloids in different solvent media.

Sympathetic toggled paroxysmal atrial fibrillation and recurrent premature atrial contractions in ambulatory patients

BackgroundAutonomic nerve activity is important in the mechanisms of paroxysmal atrial fibrillation (PAF). ObjectiveThe purpose of this study was to test the hypothesis that a single burst of skin sympathetic nerve activity (SKNA) can toggle on and off PAF or premature atrial contraction (PAC) clusters. MethodsSimultaneous recording of SKNA and electrocardiogram (neuECG) recording was performed over 7 days in patients with PAF. ResultsIn study 1, 8 patients (7 men and 1 woman; age 62 ± 8 years) had 124 episodes of PAF. An SKNA burst toggled both on and off PAF in 8 episodes (6.5%) (type 1), toggled on but not off in 12 episodes (9.7%) (type 2), and toggled on a PAC cluster followed by PAF in 4 episodes (3.2%) (type 3). The duration of these PAF episodes was <10 minutes. The remaining 100 episodes (80.6%) were associated with active SKNA bursts throughout PAF (type 4) and lasted longer than type 1 (P = .0185) and type 2 (P = .0027) PAF. There were 47 PAC clusters. Among them, 24 (51.1%) were toggled on and off, and 23 (48.9%) were toggled on but not off by an SKNA burst. In study 2, 17 patients (9 men and 8 women; age 58 ± 12 years) had <10 minutes of PAF (4, 8, 0, and 31 of types 1, 2, 3, and 4, respectively). There were significant circadian variations of all types of PAF. ConclusionA single SKNA burst can toggle short-duration PAF and PAC cluster episodes on and off. The absence of continued SKNA after the onset might have affected the maintenance of these arrhythmias.

Amyloid-like Aggregation of Wheat Gluten and Its Components during Cooking: Mechanisms and Structural Characterization.

Amyloid-like aggregation widely occurs during the processing and production of natural proteins, with evidence indicating its presence following the thermal processing of wheat gluten. However, significant gaps remain in understanding the underlying fibrillation mechanisms and structural polymorphisms. In this study, the amyloid-like aggregation behavior of wheat gluten and its components (glutenin and gliadin) during cooking was systematically analyzed through physicochemical assessment and structural characterization. The presence of amyloid-like fibrils (AFs) was confirmed using X-ray diffraction and Congo red staining, while Thioflavin T fluorescence revealed different patterns and rates of AFs growth among wheat gluten, glutenin, and gliadin. AFs in gliadin exhibited linear growth curves, while those in gluten and glutenin showed S-shaped curves, with the shortest lag phase and fastest growth rate (t1/2 = 2.11 min) observed in glutenin. Molecular weight analyses revealed AFs primarily in the 10-15 kDa range, shifting to higher weights over time. Glutenin-derived AFs had the smallest ζ-potential value (-19.5 mV) and the most significant size increase post cooking (approximately 400 nm). AFs in gluten involve interchain reorganization, hydrophobic interactions, and conformational transitions, leading to additional cross β-sheets. Atomic force microscopy depicted varying fibril structures during cooking, notably longer, taller, and stiffer AFs from glutenin.

The Relationship between the Incidence of Atrial Fibrillation and Patients with Type 2 Diabetes Mellitus: A Systematic Review

Objectives: To investigate the prevalence and mechanisms of atrial fibrillation (AF) among type 2 diabetes (T2D) patients. Methods: We conducted a thorough search of PubMed, SCOPUS, Web of Science, Google Scholar, and Science Direct to find pertinent literature. Rayyan QRCI was utilized during the entire process. Results: We included twelve studies with a total of 587,822 T2D patients and 299,957 (51%) were females. The prevalence of AF among T2D patients ranged from 0.2% to 41.63% with a total prevalence of 44936 (7.6%). The reported risk factors for developing AF among T2D patients were impaired glucose tolerance (IGT), men, obesity, elderly patients, those with lower socioeconomic backgrounds, those who currently smoked, people with reduced renal function, long-term BP fluctuation, and microvascular illness. Conclusion: Although the exact relationship between T2D and AF is still unclear, there is a significant correlation. Certain glycemic control studies indicate that therapeutic HbA1c levels in conjunction with well-controlled T2D do not significantly reduce the risk of new-onset AF in T2D patients. Further investigation is needed to fully comprehend the connection between T2D and AF. In the interim, healthcare professionals can treat people with T2D, AF, or possibly both illnesses at the same time according to accepted guidelines.

A Model Study to Assess Fibrillation and Product Stability to Support Peptide Drug Design.

The fibrillation of therapeutic peptides can present significant quality concerns and poses challenges for manufacturing and storage. A fundamental understanding of the mechanisms of fibrillation is critical for the rational design of fibrillation-resistant peptide drugs and can accelerate product development by guiding the selection of solution-stable candidates and formulations. The studies reported here investigated the effects of structural modifications on the fibrillation of a 29-residue peptide (PepA) and two sequence modified variants (PepB, PepC). The C-terminus of PepA was amidated, whereas both PepB and PepC retained the carboxylate, and Ser16 in PepA and PepB was substituted with a helix-stabilizing residue, α-aminoisobutyric acid (Aib), in PepC. In thermal denaturation studies by far-UV CD spectroscopy and fibrillation kinetic studies by fluorescence and turbidity measurements, PepA and PepB showed heat-induced conformational changes and were found to form fibrils, whereas PepC did not fibrillate and showed only minor changes in the CD signal. Pulsed hydrogen-deuterium exchange mass spectrometry (HDX-MS) showed a high degree of protection from HD exchange in mature PepA fibrils and its proteolytic fragments, indicating that most of the sequence had been incorporated into the fibril structure and occurred nearly simultaneously throughout the sequence. The effects of the net peptide charge and formulation pH on fibrillation kinetics were investigated. In real-time stability studies of two formulations of PepA at pH's 7.4 and 8.0, analytical methods detected significant changes in the stability of the formulations at different time points during the study, which were not observed during accelerated studies. Additionally, PepA samples were withdrawn from real-time stability and subjected to additional stress (40 °C, continuous shaking) to induce fibrillation; an approach that successfully amplified oligomers or prefibrillar species previously undetected in a thioflavin T assay. Taken together, these studies present an approach to differentiate and characterize fibrillation risk in structurally related peptides under accelerated and real-time conditions, providing a model for rapid, iterative structural design to optimize the stability of therapeutic peptides.

Controlling Solvent Polarity to Regulate Protein Self-Assembly Morphology and Its Universal Insight for Fibrillation Mechanism.

The mechanism of ethanol-induced fibrillation of β-lactoglobulin (β-lg) in the acidic aqueous solution upon heating was investigated using various techniques, mainly thioflavin T fluorescence, atomic force microscopy, nonreducing electrophoresis, mass spectrometry, Fourier transform infrared spectroscopy, and circular dichroism spectroscopy. The results showed that fibrillation occurred with a heating time increase, but high ethanol content slowed down the process. At a low ethanol volume fraction, peptides existed after heating for 2 h, with long and straight fibrils formed after 4-6 h, while at a high ethanol volume fraction, the proteins aggregated with very few peptides appeared at the early stage of heating, and short and curved fibrils formed after heating for 8 h. Ethanol weakened the hydrophobic interactions between proteins in the aqueous solution; therefore the latter could not completely balance the electrostatic repulsion, and thus suppressing the fibrillation process. It is believed that the fibrillation of β-lg in the acidic solution upon heating is mainly dominated by the polypeptide model; however, ethanol inhibited the hydrolysis of proteins, and the self-assembly mechanism changed to the monomer model.

Producing Cellulose Microfibrils at a High Solid Content with and without Mechanical or Enzymatic Pretreatment.

This study conducted a detailed evaluation of the feasibility of producing cellulose microfibrils (CMF) from a kraft-bleached hardwood pulp at high solid contents with and without pretreatments. CMFs produced by planetary ball milling at solid contents 17 and 28% were compared with those from 1 to 5% under the same milling conditions. Fiber pretreatments using a commercial endoglucanase and mechanical refining using a laboratory PFI mill were also applied before ball milling at a solid content of 28%. Two mechanisms of fiber fibrillation were identified from the results obtained: (i) ball and fiber/fibril interactions─the primary mechanism and (ii) interfiber/fibril frictional and tensional interactions─the secondary mechanism. The secondary mechanism plays an important role only in early-stage fibrillation and became less important as fibrillation proceeded in the later stage toward nanofibrillation. Improving fiber dispersion at lower solid content facilitated fibrillation. Endoglucanase pretreatment substantially shortened fibers to result in a "pulverized-like" CMF with short fibrils at an extended milling time. Mechanical refining of fibers facilitated fibrillation to result in CMFs with a morphology similar to that from runs without any fiber pretreatment but for a much shorter milling time. Both CMF water retention value (WRV) measurements and CMF suspension sedimentation experiments showed results consistent with imaging observations. The insights gained through this study provide relevant information with commercial significance regarding CMF production at high solids, which is not currently available in the literature.

Labile assembly of a tardigrade protein induces biostasis.

Tardigrades are microscopic animals that survive desiccation by inducing biostasis. To survive drying tardigrades rely on intrinsically disordered CAHS proteins, which also function to prevent perturbations induced by drying in vitro and in heterologous systems. CAHS proteins have been shown to form gels both in vitro and in vivo, which has been speculated to be linked to their protective capacity. However, the sequence features and mechanisms underlying gel formation and the necessity of gelation for protection have not been demonstrated. Here we report a mechanism of fibrillization and gelation for CAHS D similar to that of intermediate filament assembly. We show that in vitro, gelation restricts molecular motion, immobilizing and protecting labile material from the harmful effects of drying. In vivo, we observe that CAHS D forms fibrillar networks during osmotic stress. Fibrillar networking of CAHS D improves survival of osmotically shocked cells. We observe two emergent properties associated with fibrillization; (i) prevention of cell volume change and (ii) reduction of metabolic activity during osmotic shock. We find that there is no significant correlation between maintenance of cell volume and survival, while there is a significant correlation between reduced metabolism and survival. Importantly, CAHS D's fibrillar network formation is reversible and metabolic rates return to control levels after CAHS fibers are resolved. This work provides insights into how tardigrades induce reversible biostasis through the self-assembly of labile CAHS gels.