Filament Core Research Articles

A novel three-component helical auxetic yarn with staple fibers prepared by ring spinning

Auxetic materials with negative Poisson’s ratio have excellent physical and mechanical properties, such as shear resistance, fracture resistance and energy absorption. To expand the application of the helical auxetic yarn, a novel three-component helical auxetic yarn was developed by utilizing modified ring spinning technology. The three-component helical auxetic yarn incorporated staple fiber components into the traditional two-component helical auxetic yarn, using cotton (staple wrap fiber)/polyester (stiffer wrap filaments)/spandex (elastomeric core filaments) as the raw material for spinning. Compared with two-component helical auxetic yarn, the addition of cotton components did not significantly impact Poisson’s ratio, and the three-component helical auxetic yarn maintained a relatively stable negative Poisson’s ratio under prolonged strain. The spinning parameters of helical auxetic yarns have an impact on the yarn’s structure, which subsequently impacts the yarn’s negative Poisson’s ratio. It was found that there were significant differences in Poisson’s ratio of helical auxetic yarn between different twist factors and draft ratio of the filaments. The test results revealed that, the maximum negative Poisson’s ratio of the three-component helical auxetic yarn could reach −4.66 under a twist factor [Formula: see text] of 3.40, an elastomeric core filament draft ratio of 1.02 and a stiffer wrap filament draft ratio of 1.03.

Analysis and comparison of post-translational modifications of α-synuclein filaments in multiple system atrophy and dementia with Lewy bodies

Our previous cryogenic electron microscopy (cryoEM) analysis showed that the core structures of α-synuclein filaments accumulated in brains of patients diagnosed with dementia with Lewy bodies (DLB) and multiple system atrophy (MSA) patients are different. We analyzed the post-translational modifications (PTMs) in these filaments , and examined their relationship with the core filament structures and pathological features. Besides the common PTMs in MSA and DLB filaments, acetylation, methylation, oxidation and phosphorylation were frequently detected in MSA filaments, but not in DLB filaments. Furthermore, in DLB filament cases, the processing occurred at the C-terminal side of Asp at 119 residue and Asn at 122 residue, while in MSA cases, the processing occurred at multiple sites between residues 109–123. We have previously reported that PTMs in tau filaments depend on the filament core structure. This was considered to apply to α-synuclein filaments as well. As an example, PTMs including processing sites detected in α-synuclein filaments in early-onset DLB (an atypical form, now named juvenile-onset α-synucleinopathy) brain also supported this idea. These suggests that PTMs appeared to be closely related to the specific filament core structures.

Coaxial Bioprinting of Enzymatically Crosslinkable Hyaluronic Acid-Tyramine Bioinks for Tissue Regeneration.

Three-dimensional (3D) bioprinting has emerged as an important technique for fabricating tissue constructs with precise structural and compositional control. However, developing suitable bioinks with biocompatible crosslinking mechanisms remains a significant challenge. This study investigates extrusion-based bioprinting (EBB) using uniaxial or coaxial nozzles with enzymatic crosslinking (EC) to produce 3D tissue constructs in vitro. Initially, low-molecular-weight dextran-tyramine and hyaluronic acid-tyramine (LMW Dex-TA/HA-TA) bioink prepolymers were evaluated. Enzymatically pre-crosslinking these prepolymers, achieved by the addition of horseradish peroxidase and hydrogen peroxide, produced viscous polymer solutions. However, this approach resulted in inconsistent bioprinting outcomes (uniaxial) due to inhomogeneous crosslinking, leading to irreproducible properties and suboptimal shear recovery behavior of the hydrogel inks. To address these challenges, we explored a one-step coaxial bioprinting system consisting of enzymatically crosslinkable high-molecular-weight hyaluronic acid-tyramine conjugates (HMW HA-TA) mixed with horseradish peroxidase (HRP) in the inner core and a mixture of Pluronic F127 and hydrogen peroxide in the outer shell. This configuration resulted in nearly instantaneous gelation by diffusion of the hydrogen peroxide into the core. Stable hydrogel fibers with desirable properties, including appropriate swelling ratios and controlled degradation rates, were obtained. The optimized bioink and printing parameters included 1.3% w/v HMW HA-TA and 5.5 U/mL HRP (bioink, inner core), and 27.5% w/v Pluronic F127 and 0.1% H2O2 (sacrificial ink, outer shell). Additionally, optimal pressures for the inner core and outer shell were 45 and 80 kPa, combined with a printing speed of 300 mm/min and a bed temperature of 30 °C. The extruded HMW HA-TA core filaments, containing bovine primary chondrocytes (BPCs) or 3T3 fibroblasts (3T3 Fs), exhibited good cell viabilities and were successfully cultured for up to seven days. This study serves as a proof-of-concept for the one-step generation of core filaments using a rapidly gelling bioink with an enzymatic crosslinking mechanism, and a coaxial bioprinter nozzle system. The results demonstrate significant potential for developing designed, printed, and organized 3D tissue fiber constructs.

New feeding mechanism to enhance the properties of wrapped elastic composite yarn and denim fabrics thereof

In light of the recent technological advancements in composite yarns with multicomponent cores, also known as dual core spun yarns, their utilisation in the textile industry has become widespread. A V-grooved roller is employed to enhance the feeding of multicomponent cores. In this context, diverse composite yarn designs with varying feeding mechanisms can be employed to optimise yarn performance. This study presents an alternative feeding mechanism utilising a W-grooved roller for commercial use in composite yarn production. To achieve this, dual core yarns and wound elastic composite yarns (filament feeding varies with the sheath cotton fibre with elastane in the centre wrapped on the right and left side) were produced using a modified ring spinning system with different parameters. Denim fabrics were then produced using these composite yarns as weft yarns. The results demonstrated that the wrapped elastic composite yarns with left and right filament core positioning exhibited superior yarn properties in terms of strength, elongation at break, evenness and hairiness. Furthermore, denim fabrics made with wrapped elastic composite yarns exhibited superior breaking load and tearing force results on weft basis. These fabrics also exhibited lower growth, defined as the percentage of the fabric returning to its original length after tensile stress removal.

Targeting type I DED interactions at the DED filament serves as a sensitive switch for cell fate decisions.

Activation of procaspase-8 in the death effector domain (DED) filaments of the death-inducing signaling complex (DISC) is a key step in apoptosis. In this study, a rationally designed cell-penetrating peptide, DEDid, was engineered to mimic the h2b helical region of procaspase-8-DED2 containing a highly conservative FL motif. Furthermore, mutations were introduced into the DEDid binding site of the procaspase-8 type I interface. Additionally, our data suggest that DEDid targets other type I DED interactions such as those of FADD. Both approaches of blocking type I DED interactions inhibited CD95L-induced DISC assembly, caspase activation and apoptosis. We showed that inhibition of procaspase-8 type I interactions by mutations not only diminished procaspase-8 recruitment to the DISC but also destabilizedthe FADD core of DED filaments. Taken together, this study offers insights to develop strategies to target DED proteins, which may be considered in diseases associated with cell death and inflammation.

TMEM106B core deposition associates with TDP-43 pathology and is increased in risk SNP carriers for frontotemporal dementia.

Genetic variation at the transmembrane protein 106B gene (TMEM106B) has been linked to risk of frontotemporal lobar degeneration with TDP-43 inclusions (FTLD-TDP) through an unknown mechanism. We found that presence of the TMEM106B rs3173615 protective genotype was associated with longer survival after symptom onset in a postmortem FTLD-TDP cohort, suggesting a slower disease course. The seminal discovery that filaments derived from TMEM106B is a common feature in aging and, across a range of neurodegenerative disorders, suggests that genetic variants in TMEM106B could modulate disease risk and progression through modulating TMEM106B aggregation. To explore this possibility and assess the pathological relevance of TMEM106B accumulation, we generated a new antibody targeting the TMEM106B filament core sequence. Analysis of postmortem samples revealed that the TMEM106B rs3173615 risk allele was associated with higher TMEM106B core accumulation in patients with FTLD-TDP. In contrast, minimal TMEM106B core deposition was detected in carriers of the protective allele. Although the abundance of monomeric full-length TMEM106B was unchanged, carriers of the protective genotype exhibited an increase in dimeric full-length TMEM106B. Increased TMEM106B core deposition was also associated with enhanced TDP-43 dysfunction, and interactome data suggested a role for TMEM106B core filaments in impaired RNA transport, local translation, and endolysosomal function in FTLD-TDP. Overall, these findings suggest that prevention of TMEM106B core accumulation is central to the mechanism by which the TMEM106B protective haplotype reduces disease risk and slows progression.

NIKA2 observations of starless cores in Taurus and Perseus

Dusty starless cores play an important role in regulating the initial phases of the formation of stars and planets. In their interiors, dust grains coagulate and ice mantles form, thereby changing the millimeter emissivities and hence the ability to cool. We mapped four regions with more than a dozen cores in the nearby Galactic filaments of Taurus and Perseus using the NIKA2 camera at the IRAM 30-meter telescope. Combining the 1mm to 2mm flux ratio maps with dust temperature maps from Herschel allowed to create maps of the dust emissivity index β1,2 at resolutions of 2430 and 5600 a.u. in Taurus and Perseus, respectively. Here, we study the variation with total column densities and environment. β1,2 values at the core centers (Av =12 – 19 mag) vary significantly between ~ 1.1 and 2.3. Several cores show a strong rise of β1,2 from the outskirts at ~ 4 mag to the peaks of optical extinctions, consistent with the predictions of grain models and the gradual build-up of ice mantles on coagulated grains in the dense interiors of starless cores.

An Update on Reported Variants in the Skeletal Muscle α‐Actin (ACTA1) Gene

The ACTA1 gene encodes skeletal muscle alpha‐actin, which forms the core of the sarcomeric thin filament in adult skeletal muscle. ACTA1 represents one of six highly conserved actin proteins that have all been associated with human disease. The first 15 pathogenic variants in ACTA1 were reported in 1999, which expanded to 177 in 2009. Here, we update on the now 607 total variants reported in LOVD, HGMD, and ClinVar, which includes 343 reported pathogenic/likely pathogenic (P/LP) variants. We also provide suggested ACTA1‐specific modifications to ACMG variant interpretation guidelines based on our analysis of known variants, gnomAD reports, and pathogenicity in other actin isoforms. Using these criteria, we report a total of 447 P/LP ACTA1 variants. From a clinical perspective, the number of reported ACTA1 disease phenotypes has grown from five to 20, albeit with some overlap. The vast majority (74%) of ACTA1 variants cause nemaline myopathy (NEM), but there are increasing numbers that cause cardiomyopathy and novel phenotypes such as distal myopathy. We highlight challenges associated with identifying genotype–phenotype correlations for ACTA1. Finally, we summarize key animal models and review the current state of preclinical treatments for ACTA1 disease. This update provides important resources and recommendations for the study and interpretation of ACTA1 variants.

NIKA2 observations of dust grain evolution from star-forming filament to T-Tauri disk: Preliminary results from NIKA2 observations of the Taurus B211/B213 filament

To understand the evolution of dust properties in molecular clouds in the course of the star formation process, we constrain the changes in the dust emissivity index from star-forming filaments to prestellar and protostellar cores to T Tauri stars. Using the NIKA2 continuum camera on the IRAM 30 m telescope. we observed the Taurus B211/B2I3 filament at 1.2 mm and 2 mm with unprecedented sensitivity and used the resulting maps to derive the dust emissivity index β. Our sample of 105 objects detected in the β map of the B211/B213 filament indicates that, overal. β decreases from filament and prestellar cores (β ~ 2 ± 0.5) to protostellar cores (β ~ 1.2 ± 0.2) to T-Tauri protoplanetary disk (β < I). The averaged dust emissivity index β across the B211/B2I3 filament exhibits a flat (β ~ 2 ± 0.3) profile. This may imply that dust grain sizes are rather homogeneous in the filament, start to grow significantly in size only after the onset of the gravitational contraction/collapse of prestellar cores to protostars, reaching big sizes in T Tauri protoplanetary disks. This evolution from the parent filament to T-Tauri disks happens on a timescale of about 1-2 Myr.

Cryo-EM structures of tau filaments from the brains of mice transgenic for human mutant P301S Tau

Mice transgenic for human mutant P301S tau are widely used as models for human tauopathies. They develop neurodegeneration and abundant filamentous inclusions made of human mutant four-repeat tau. Here we used electron cryo-microscopy (cryo-EM) to determine the structures of tau filaments from the brains of Tg2541 and PS19 mice. Both lines express human P301S tau (0N4R for Tg2541 and 1N4R for PS19) on mixed genetic backgrounds and downstream of different promoters (murine Thy1 for Tg2541 and murine Prnp for PS19). The structures of tau filaments from Tg2541 and PS19 mice differ from each other and those of wild-type tau filaments from human brains. The structures of tau filaments from the brains of humans with mutations P301L, P301S or P301T in MAPT are not known. Filaments from the brains of Tg2541 and PS19 mice share a substructure at the junction of repeats 2 and 3, which comprises residues I297-V312 of tau and includes the P301S mutation. The filament core from the brainstem of Tg2541 mice consists of residues K274-H329 of tau and two disconnected protein densities. Two non-proteinaceous densities are also in evidence. The filament core from the cerebral cortex of line PS19 extends from residues G271-P364 of tau. One strong non-proteinaceous density is also present. Unlike the tau filaments from human brains, the sequences following repeat 4 are missing from the cores of tau filaments from the brains of Tg2541 and PS19 mice.

Molecular mechanisms of inorganic-phosphate release from the core and barbed end of actin filaments.

The release of inorganic phosphate (Pi) from actin filaments constitutes a key step in their regulated turnover, which is fundamental to many cellular functions. The mechanisms underlying Pi release from the core and barbed end of actin filaments remain unclear. Here, using human and bovine actin isoforms, we combine cryo-EM with molecular-dynamics simulations and in vitro reconstitution to demonstrate how actin releases Pi through a 'molecular backdoor'. While constantly open at the barbed end, the backdoor is predominantly closed in filament-core subunits and opens only transiently through concerted amino acid rearrangements. This explains why Pi escapes rapidly from the filament end but slowly from internal subunits. In a nemaline-myopathy-associated actin variant, the backdoor is predominantly open in filament-core subunits, resulting in accelerated Pi release and filaments with drastically shortened ADP-Pi caps. Our results provide the molecular basis for Pi release from actin and exemplify how a disease-linked mutation distorts the nucleotide-state distribution and atomic structure of the filament.

Effects of the oxygen source configuration on the superconducting properties of internally-oxidized internal-Sn Nb3Sn wires

We successfully manufactured 12-filament rod-in-tube Nb3Sn wires with oxide nanoparticles formed by the internal oxidation method. We employed Nb-7.5 wt%Ta-1 wt%Zr and Nb-7.5 wt%Ta-2 wt% Hf alloys along with oxygen sources (OSs) in two different configurations—in the core of Nb filaments (coreOS) and at the boundary between the filaments and the Cu tube (annularOS)—to assess the influence of the OS layout on the superconducting properties and grain size. The simultaneous presence of the OS and of Hf or Zr reduced the average Nb3Sn grain size to around 50 nm, leading to an enhancement of the layer critical current density (Jc ) up to 3000 A mm−2 at 4.2 K and 16 T for the Hf-annularOS wire. Samples manufactured with an OS show a shift toward higher reduced magnetic fields of the position of the maximum in pinning-force density, this shift being more pronounced when SnO2 is added in the annularOS configuration, and for the Hf-containing samples. This enhanced pinning at higher magnetic field is beneficial for high-field magnet applications. Moreover, we measured a very high upper critical field, reaching 29.3 T at 4.2 K in the Hf-annularOS samples.

Distinct tau folds initiate templated seeding and alter the post-translational modification profile.

Pathological tau accumulates in the brain in tauopathies such as Alzheimer's disease, Pick's disease, progressive supranuclear palsy and corticobasal degeneration, and forms amyloid-like filaments incorporating various post-translational modifications (PTMs). Cryo-electron microscopic (cryo-EM) studies have demonstrated that tau filaments extracted from tauopathy brains are characteristic of the disease and share a common fold(s) in the same disease group. Furthermore, the tau PTM profile changes during tau pathology formation and disease progression, and disease-specific PTMs are detected in and around the filament core. In addition, templated seeding has been suggested to trigger pathological tau amplification and spreading in vitro and in vivo, although the molecular mechanisms are not fully understood. Recently, we reported that the cryo-EM structures of tau protofilaments in SH-SY5Y cells seeded with patient-derived tau filaments show a core structure(s) resembling that of the original seeds. Here, we investigated PTMs of tau filaments accumulated in the seeded cells by liquid chromatography/tandem mass spectrometry and compared them with the PTMs of patient-derived tau filaments. Examination of insoluble tau extracted from SH-SY5Y cells showed that numerous phosphorylation, deamidation and oxidation sites detected in the fuzzy coat in the original seeds were well reproduced in SH-SY5Y cells. Moreover, templated tau filament formation preceded both truncation of the N-/C-terminals of tau and PTMs in and around the filament core, indicating these PTMs may predominantly be introduced after the degradation of the fuzzy coat.

Formation of various cell-aggregated structures in the core of hydrogel filament using a microfluidic device and its application as an in vitro neuromuscular junction model

Microfluidic systems have been widely used in various in vitro tissue engineering models. In this paper, we present a new microfluidic system for manufacturing cell filaments laden with cell aggregates of various shapes (beads, rosaries, and filaments) in the core region. The structures were obtained using the Rayleigh-Plateau instability of the two-phase flow of the injected bioinks (continuous phase of collagen/poly[ethylene glycol] diacrylate [PEGDA] and a dispersed phase of methacrylated gelatin (GelMA)). To demonstrate the potential of the system at the neuromuscular junction in vitro model, we injected a C2C12-laden collagen/PEGDA bioink into the sheath region and GelMA mixed with motor neuron cells (NSC-34) into the core region of the fabricated cell aggregates. The rosary-shaped NSC-34 aggregate in the core exhibited higher cell viability and more developed neurogenic gene expression than the cell aggregates of beads and filaments in the core region, owing to much greater mechanotransduction. Furthermore, when comparing the cell-laden struts (C2C12 in the sheath region and NSC34 in the rosary core region) with normally bioprinted struts with the same cell density, the expressions of myogenesis-, neuromuscular junction (NMJ)-, and neurogenesis-related genes in struts laden with rosary-shaped cell aggregates were significantly upregulated. The results of these experiments demonstrate the potential for the fabrication of new cell-laden core-sheath structures, which could be used for designing various in vitro models.

Different tau fibril types reduce prion level in chronically and de novo infected cells

Neurodegenerative diseases are often characterized by the codeposition of different amyloidogenic proteins, normally defining distinct proteinopathies. An example is represented by prion diseases, where the classical deposition of the aberrant conformational isoform of the prion protein (PrPSc) can be associated with tau insoluble species, which are usually involved in another class of diseases called tauopathies. How this copresence of amyloidogenic proteins can influence the progression of prion diseases is still a matter of debate. Recently, the cellular form of the prion protein, PrPC, has been investigated as a possible receptor of amyloidogenic proteins, since its binding activity with Aβ, tau, and α-synuclein has been reported, and it has been linked to several neurotoxic behaviors exerted by these proteins. We have previously shown that the treatment of chronically prion-infected cells with tau K18 fibrils reduced PrPSc levels. In this work, we further explored this mechanism by using another tau construct that includes the sequence that forms the core of Alzheimer's disease tau filaments invivo to obtain a distinct fibril type. Despite a difference of six amino acids, these two constructs form fibrils characterized by distinct biochemical and biological features. However, their effects on PrPSc reduction were comparable and probably based on the binding to PrPC at the plasma membrane, inhibiting the pathological conversion event. Our results suggest PrPC as receptor for different types of tau fibrils and point out a role of tau amyloid fibrils in preventing the pathological PrPC to PrPSc conformational change.

Mutation ∆K281 in MAPT causes Pick’s disease

Two siblings with deletion mutation ∆K281 in MAPT developed frontotemporal dementia. At autopsy, numerous inclusions of hyperphosphorylated 3R Tau were present in neurons and glial cells of neocortex and some subcortical regions, including hippocampus, caudate/putamen and globus pallidus. The inclusions were argyrophilic with Bodian silver, but not with Gallyas–Braak silver. They were not labelled by an antibody specific for tau phosphorylated at S262 and/or S356. The inclusions were stained by luminescent conjugated oligothiophene HS-84, but not by bTVBT4. Electron cryo-microscopy revealed that the core of tau filaments was made of residues K254-F378 of 3R Tau and was indistinguishable from that of Pick’s disease. We conclude that MAPT mutation ∆K281 causes Pick’s disease.

An unbroken network of interactions connecting flagellin domains is required for motility in viscous environments.

In its simplest form, bacterial flagellar filaments are composed of flagellin proteins with just two helical inner domains, which together comprise the filament core. Although this minimal filament is sufficient to provide motility in many flagellated bacteria, most bacteria produce flagella composed of flagellin proteins with one or more outer domains arranged in a variety of supramolecular architectures radiating from the inner core. Flagellin outer domains are known to be involved in adhesion, proteolysis and immune evasion but have not been thought to be required for motility. Here we show that in the Pseudomonas aeruginosa PAO1 strain, a bacterium that forms a ridged filament with a dimerization of its flagellin outer domains, motility is categorically dependent on these flagellin outer domains. Moreover, a comprehensive network of intermolecular interactions connecting the inner domains to the outer domains, the outer domains to one another, and the outer domains back to the inner domain filament core, is required for motility. This inter-domain connectivity confers PAO1 flagella with increased stability, essential for its motility in viscous environments. Additionally, we find that such ridged flagellar filaments are not unique to Pseudomonas but are, instead, present throughout diverse bacterial phyla.

Three-dimensional orthogonal woven hybrid fabrics in X band frequency region for electromagnetic shielding effectiveness

The three-dimensional fabric structures with metallic yarns and different fibers offer additional opportunities to enhance the electromagnetic shielding potential. This study involves the manufacturing of a Three-Dimensional Orthogonal Woven (3DOW) hybrid conductive fabric to be potentially used in an electromagnetic shielding field. 3DOW fabric consisting of copper filament-based core-sheath hybrid yarn in the weft direction has been manufactured to obtain maximum shielding effect. Hybrid yarns were produced using the DREF-III spinning technique, having copper filament in the core and sheathing by Polyphenylene Sulfide (PPS) staple fibers. The experiment was designed using Box-Behnken method. The orthogonal fabric samples are tested in an electromagnetic frequency region of 8-12 GHz using Free Space Measurement System (FSMS) to estimate absorbance, reflectance, and transmittance. Hybrid yarn parameters such as PPS fiber diameter, copper filament diameter, and yarn linear density considerably affect electromagnetic shielding. 3DOW fabric’s electromagnetic shielding effect increase with the diameter of the copper core filament, as does PPS yarn’s diameter, showing a promising trend towards shielding. The findings of orthogonal structure can be further extended in other Three-Dimensional structures like multi-layer, angle interlock, draperies, and tops for civilians and soldierly applications.

Architecture and function of the meiotic metazoan HORMAD chromatin binding region (CBR).

During early meiotic prophase, the chromosome axis is formed by DNA-binding cohesin proteins, filamentous axis core proteins, and meiotic HORMA domain (HORMAD) proteins. HORMADs are master regulators of meiotic recombination, recruiting Spo11 and associated proteins to create DNA double-strand breaks (DSBs) and promoting their repair as interhomolog crossovers (COs). In earlier work, we discovered a central chromatin binding region (CBR) domain in the S. cerevisiae HORMAD protein Hop1 (SNU, unpublished), and further found that diverse eukaryotes including many plants and metazoans within the opisthokonta family also possess a central CBR with variable architecture. In fungi such as Vanderwaltozyma polyspora and Saccharomyces cerevisiae, Hop1 has an internal CBR domain containing a variant plant homeodomain (PHD) zinc finger domain and a DNA-binding winged helix-turn-helix domain (wHTH), plus a conserved C-terminal extension (HTH-C). Similarly, metazoan HORMAD CBR domains are predicted to contain a canonical PHD domain and a wHTH domain. Here we show two x-ray crystal structures of metazoan HORMAD CBRs from Schistosoma mansoni (blood fluke) and Patiria miniata (starfish). Both structures contain PHD and wHTH domains like the fungal Hop1 CBR, but do not contain a C-terminal extension (HTH-C). The PHD domain contains two beta strands with a conserved pocket that we propose binds a histone tail. We are currently pursuing both biochemical and cell-based approaches to determine the molecular basis for the HORMAD CBR-chromatin interaction and identify any specificity for histone tail modifications. This work will define how the HORMAD CBR modulates chromosome axis architecture and localization in diverse eukaryotes.

Study on the Tensile Behavior of Helical Auxetic Yarns with Finite Element Method

Complex yarns with helical wrapping structure show auxetic effect under axial tension and a wide perspective application. Experimental results suggested that initial helical angle was one of the most important structural parameters. However, the experimental method was limited and could not effectively explain the deformation behavior or auxetic mechanism. A finite element model of the helical auxetic yarn was built and used to analyze the interactive relationship between the two components and the stress distribution mode. The effectiveness and accuracy of the model was first verified by comparing with the experimental results. The simulation results showed that the complex yarn with initial helical angle of 14.5° presented the maximum negative Poisson's ratio of -2.5 under 5.0% axial strain. Both the contact property between the two components and the radial deformability of the elastic core filament were key factors of the auxetic property. When the contact surfaces were completely smooth and the friction coefficient μ was set to 0, the complex yarn presented non-auxetic behavior. When the Poisson's ratio of the core filament was 0, the complex yarn showed greater auxetic effect. During the axial stretching, the tensile stress was mainly distributed in the wrap filament, which led to structural deformation and auxetic behavior. A pair of auxetic yarns showed pore effect and high expansion under axial strain. Thus, it may be necessary to consider new weaving structures and preparation methods to obtain the desired auxetic property and application of auxetic yarns.