Increase In Cell Size Research Articles

Mechanical, electrochemical and permeability behaviour of Ti6Al–4V scaffolds fabricated by electron beam powder bed fusion for orthopedic implant applications: The role of cell type and cell size

Ti–6Al–4V scaffolds have attracted much attention for biomedical applications owing to their bone-mimicking mechanical properties and better bone tissue in-growth and additive manufacturing can be employed to fabricate complex geometry scaffolds. The present study aimed to investigate the effects of scaffold architecture on the mechanical, electrochemical, and permeability behaviour of Ti–6Al–4V scaffolds fabricated by electron beam powder bed fusion (EB-PBF). For this, scaffolds with diamond and rhombic dodecahedron cell types, having various cell sizes, were designed and successfully fabricated. Chemical etching minimized the surface defects and improved the geometric fidelity of the scaffolds compared to the original designs. The larger the cell size, the coarser the dual α/β phase microstructure due to the higher heat accumulation in thicker struts. The scaffold architecture proved significant effects on the mechanical properties, where all scaffolds were mechanically comparable with human bone. Short/long-term electrochemical corrosion tests indicated that the corrosion performance significantly improved with an increase in cell size, irrespective of the cell type; this was attributed to the lower exposure of surface area to the electrolyte, coarse microstructure and a higher fraction of β phase. This study recommended that the EB-PBF Ti–6Al–4V scaffolds are promising candidates for orthopaedic implant applications from mechanical and electrochemical points of view.

Salinity-driven changes in Salicornia cell wall nanomechanics and lignin composition

Widespread increases in soil salinization significantly reduce agricultural lands. Nevertheless, salt-tolerant plants, such as Salicornia europaea L., can play a crucial role in the reclamation of these lands. We selected S. europaea for this study due to its potential to mitigate soil salinization and its numerous applications, such as intercropping in agriculture, biocompounds production and bioenergy. This work was designed to determine whether different salinities induce significant biophysical, anatomical, lignin and gene transcript changes in S. europaea. Through atomic force microscopy (AFM), we revealed that salinity stimulated an increase in cell wall elasticity (CWE) as an important physiological mechanism of adaptation known as cell’s turgor conservation effect. Direct values of the cell wall stiffness subjected to salinity were obtained, with Young’s modulus (E) ranging from low and high salinity 0.52 to 0.03 MPa. The softening of the cell wall properly correlated with an increase in cell size, plant cells under strong salinity 1000 mM NaCl, swelled 5.4 times. The best salinity range found for its optimum growth was 200–400 mM NaCl. At higher salinities, we identified increases in the lignified xylem, large calcium oxalate crystals, and in transcript amounts of SeSOS1 and SeNHX1, which has a significant negative correlation with cell wall stiffness (−0.57 and −0.95, respectively). The high syringyl and guaiacyl ratio (S/G) in lignin for 0–400 mM NaCl may have influenced the rigidity and hydrophobicity of the cell walls. A positive S/G ratio and sugar yields are associated with higher bioethanol production, these values may also be useful for agriculture, biorefinery, biocompounds and plant-breeding applications. We conclude that salinity indeed influenced the cell wall traits of S. europaea. This halophyte is capable of markedly softening its cell wall as a way of adapting to the high level of salinity. Our presented insights and correlations not only provide a better understanding of cell wall remodelling but are also considered vital traits of adaptation strategies that this halophyte holds under salinity environment. These inputs can also be applied in future research aiming to produce biomass and biofuel or to improve the salinity tolerance during the cultivation of non-tolerant plants, crops and glycophytes, which is a significant challenge in agriculture, particularly in arid and coastal regions. The unique properties of the S. europaea cell walls could also inspire the development of materials with enhanced nanomechanical elasticity for resistance to osmotic stress.

Caspase-4 has a role in cell division in epithelial cells through actin depolymerization

In addition to its role in pyroptosis and inflammatory cytokine maturation, caspase-4 (CASP4) also contributes to the fusion of phagosomes with lysosomes and cell migration. However, its role in cell division remains elusive. In this study, we demonstrate that CASP4 is indispensable for proper cell division in epithelial cells. Knockout of CASP4 (CASP4 KO) in HepG2 cells led to delayed cell proliferation, increased cell size, and increased multinucleation. In mitosis, CASP4 KO cells showed multipolar spindles, asymmetric spindle positioning, and chromosome segregation errors, ultimately increasing DNA content and chromosome number. We also found that phalloidin, a marker of filamentous actin, increased in CASP4 KO cells owing to suppressed actin depolymerization. Moreover, the levels of actin polymerization-related proteins, including Rho-associated protein kinase1 (ROCK1), LIM kinase1 (LIMK1), and phosphorylated cofilin, significantly increased in CASP4 KO cells. These results suggest that CASP4 contributes to proper cell division through actin depolymerization.

Gigantic animal cells suggest organellar scaling mechanisms across a 50-fold range in cell volume.

The largest cells are orders of magnitude bigger than the smallest cells. Organelle content scales to maintain cell function, with different organelles increasing in volume, length, or number as cells increase in size. Scaling may also reflect functional demands placed on organelles by increased cell size. Amphibians exhibit exceptional diversity in cell size. Using transmission electron microscopy, we analyzed 3 species whose enterocyte cell volumes range from 228 to 10,593 μm3. We show that nuclear volume increases by an increase in radius while mitochondrial volume increases by an increase in total network length; the endoplasmic reticulum and Golgi apparatus, with their complex shapes, are intermediate. Notably, all 4 organelle types increase in total volume proportional to cell volume, despite variation in functional (i.e., metabolic, transport) demands. This pattern suggests that organellar building blocks are incorporated into more or larger organelles following the same rules across species that vary ~50-fold in cell sizes, consistent with a "limited precursor" model for organellar scaling that, in turn, assumes equivalent cytoplasmic concentrations of organellar building block proteins. Taken together, our results lead us to hypothesize that salamanders have evolved increased biosynthetic capacity to maintain functional protein concentrations despite huge cell volumes.

Hsf1 and the molecular chaperone Hsp90 support a 'rewiring stress response' leading to an adaptive cell size increase in chronic stress.

Cells are exposed to a wide variety of internal and external stresses. Although many studies have focused on cellular responses to acute and severe stresses, little is known about how cellular systems adapt to sublethal chronic stresses. Using mammalian cells in culture, we discovered that they adapt to chronic mild stresses of up to two weeks, notably proteotoxic stresses such as heat, by increasing their size and translation, thereby scaling the amount of total protein. These adaptations render them more resilient to persistent and subsequent stresses. We demonstrate that Hsf1, well known for its role in acute stress responses, is required for the cell size increase, and that the molecular chaperone Hsp90 is essential for coupling the cell size increase to augmented translation. We term this translational reprogramming the 'rewiring stress response', and propose that this protective process of chronic stress adaptation contributes to the increase in size as cells get older, and that its failure promotes aging.

Hsf1 and the molecular chaperone Hsp90 support a ‘rewiring stress response’ leading to an adaptive cell size increase in chronic stress

Cells are exposed to a wide variety of internal and external stresses. Although many studies have focused on cellular responses to acute and severe stresses, little is known about how cellular systems adapt to sublethal chronic stresses. Using mammalian cells in culture, we discovered that they adapt to chronic mild stresses of up to two weeks, notably proteotoxic stresses such as heat, by increasing their size and translation, thereby scaling the amount of total protein. These adaptations render them more resilient to persistent and subsequent stresses. We demonstrate that Hsf1, well known for its role in acute stress responses, is required for the cell size increase, and that the molecular chaperone Hsp90 is essential for coupling the cell size increase to augmented translation. We term this translational reprogramming the ‘rewiring stress response’, and propose that this protective process of chronic stress adaptation contributes to the increase in size as cells get older, and that its failure promotes aging.

Nectin-4 regulates cellular senescence-associated enlargement of cell size

Cellular senescence is defined as irreversible growth arrest induced by various stress, such as DNA damage and oxidative stress. Senescent cells exhibit various characteristic morphological changes including enlarged morphology. In our recent study, we identified Nectin-4 to be upregulated in cellular senescence by comparative transcriptomic analysis. However, there are few reports on the relationship between Nectin-4 and senescence. Therefore, we analyzed the function of Nectin-4 in senescence and its biological significance. When overexpressed with Nectin-4, the cells exhibited the enlarged cell morphology closely resembling senescent cells. In addition, the cell size enlargement during DNA damage-induced senescence was suppressed by knockdown of Nectin-4, while there were no significant changes in senescence induction. These results suggest that Nectin-4 is not involved in the regulation of senescence itself but contributes to the senescence-associated cell size increase. Furthermore, the Nectin-4-dependent cell size increase was found to be mediated by Src family kinase (SFK)/PI3 kinase (PI3K)/Rac1 pathway. To explore the functional consequences of cell size enlargement, we analyzed cell survival in Nectin-4-depleted senescent cells. Single-cell tracking experiments revealed that Nectin-4 knockdown induced apoptosis in senescent cells, and there is a strong positive correlation between cell size and survival rate. These results collectively indicate that Nectin-4 plays a causative role in the senescence-associated cell size enlargement via SFK/PI3K/Rac1, which can contribute to survival of senescent cells.

Improvement of the rate capability of the Li4Ti5O12 anode material by modification of the surface composition with lithium polysulfide

Partial substitution of oxygen by sulfur was attempted using a Li/Ti rich conditions for the nominal compositions Li4Ti5O12−xSx x = 0.125–0.375. However, a much lower sulfur substitution, i.e. at dopant level, was achieved as deduced from an almost negligible increase in unit cell size observed from X-ray powder diffraction. The sulfur in the samples is mainly deposited on the surface as sulfate and Li2S2 as deduced from XPS. However, most of the nominal sulfur is lost. Interestingly, for nominal x = 0.125 a considerable improvement in performance is achieved compared to undoped LTO. The sample with x = 0.125 not only shows ∼9% higher capacity at slow cycling at C/20, but also has a remarkably better power rate behavior, with a capacity of 125 mAh g−1 at higher 2 C, compared to 79 mAh g−1 for LTO at the same rate. The significant improvement is explained by the formation of lithium polysulfide in the high-temperature reaction and the concomitant Li+ deficiency to form the spinel, causing the reduction of Ti4+ to Ti3+ and the creation of oxygen vacancies with the formation of an oxygen and lithium deficient spinel Li4−y (Ti4+)5−y (Ti3+)y O12−y. Li2S2, detected in the sample with nominal x = 0.125 by XPS and at higher nominal sulfur contents by CV, may prevent carbonation of the spinel surface while providing ionic conductivity upon reduction to Li2S, justifying its better performance. On the other hand, the contribution to capacity from both mass diffusion and the capacitive charge storage mechanism is unaffected, and therefore LTO and surface-modified LTO-S-0.125 are regarded as typical battery materials.

Too big not to fail: emerging evidence for size-induced senescence.

Cellular senescence refers to a permanent and stable state of cell cycle exit. This process plays an important role in many cellular functions, including tumor suppression. It was first noted that senescence is associated with increased cell size in the early 1960s; however, how this contributes to permanent cell cycle exit was poorly understood until recently. In this review, we discuss new findings that identify increased cell size as not only a consequence but also a cause of permanent cell cycle exit. We highlight recent insights into how increased cell size alters normal cellular physiology and creates homeostatic imbalances that contribute to senescence induction. Finally, we focus on the potential clinical implications of these findings in the context of cell cycle arrest-causing cancer therapeutics and speculate on how tumor cell size changes may impact outcomes in patients treated with these drugs.

Abstract 18022: Multiplexed Generation and Functional Annotation of Hypertrophic Cardiomyopathy-Associated MYH7 Missense Variants in Isogenic Gene-Edited Stem Cell-Derived Cardiomyocytes

Hypertrophic cardiomyopathy (HCM) is an inheritable cardiac condition affecting 1:200-500 people and is characterized by left ventricular hypertrophy that can cause heart failure. Autosomal-dominant, missense mutations in MYH7 (encoding MHC-β) cause 33% of genotype + HCM cases. Despite this, 75% of MYH7 missense variants are of unknown clinical significance (VUS). Human induced pluripotent stem cell-derived cardiomyocytes (hiPSC-CMs) can elucidate the effect(s) of VUS, however, new variant identification by genetic testing outpaces methods to gene edit hiPSCs. Thus, we developed a method called CR ISPR a On- T arget E diting R etrieval (CRaTER) which increased successful gene-editing 25-fold over current methods. We leveraged CRaTER to enrich for edited hiPSCs, generating a library of 113 MYH7 missense variants. As mutations can reduce protein stability and abundance, we flow sorted MYH7 variant hiPSC-CMs into bins based on differing MHC-β protein abundance followed by next generation sequencing to calculate variant abundance scores. This multiplexed assay identified 31 residue substitutions as functionally abnormal, including all tested pathogenic variants and VUS. MHC-β depletion was validated in clonal hiPSC-CMs and by Western blotting of patient myocardium with a MYH7 mutation. Additionally, we found that severe MHC-β depletion is associated with increased cell size, a hallmark pathological phenotype of HCM. Finally, single-cell contractility analyses of hiPSC-CMs with a pathogenic MYH7 variant revealed hyperdynamic physiology relative to isogenic controls, suggesting an association between MHC-β loss and systolic dysfunction. Together, CRaTER enables the generation of isogenic hiPSC variant libraries at unprecedented scale for differentiation to disease-relevant cell types. Functional analyses of MYH7 variant hiPSC-CMs have revealed a novel correlation between MHC-β protein depletion and pathogenicity that accurately predicts MYH7 variant effect and has implications for future MYH7 variant effect interpretations.

STAT5-Feedback Controls Distinct Metabolic States for Dynamic Transitions between Cellular Activation and Quiescence in Acute Lymphoblastic Leukemia

Background and significance: B-cell acute lymphoblastic leukemia (B-ALL) is characterized by dynamic shifts between activation and quiescence. These cycles are predicated by fluctuations in oncogenic signaling, which mimic pre-BCR and cytokine receptor signaling, e.g. IL7 receptor signaling and phosphorylation of STAT5. These fluctuations in cytokine receptor and STAT5 signaling are mitigated by powerful feedback regulators, including CISH and SOCS (suppressors of cytokine signaling) family members. While B-ALL cells depend on oncogenic STAT5 signaling, CISH and SOCS2 negative feedback regulators of STAT5 are highly expressed in aggressive B-ALL and high expression levels are strongly linked to poor clinical outcome, positive MRD and increased likelihood of bone marrow relapse in children (COG P9906) and adults (ECOG E2993). To determine whether high levels of CISH and SOCS2 are biomarkers of high oncogenic STAT5 signaling or mechanistically contribute to clonal fitness and adaptability of B-ALL, we performed genetic experiments in mouse models for B-ALL. Here we examined the mechanisms and consequences of active and inactive states of STAT5 by studying constitutively active (CA) and non-phosphorylatable Y694F (YF) mutations of STAT5. Results: Consistent with a central role of STAT5-feedback control in B-ALL survival, inducible ablation of Cishfl/fl resulted in rapid depletion of B-ALL cells. Socs2-/- B-ALL cells rapidly underwent cellular senescence, lacked colony forming and leukemia-initiating capacity in serial transplantation experiments. Likewise direct interference with STAT5-function, by mutations resulting in constitutive activation (STAT5-CA) or an inactive state (STAT5-YF). Consistent with a requirement of adaptive STAT5-feedback control in B-ALL, both Stat5-CA and Stat5-YF resulted in rapid cell death. Induction of Stat5-CA caused accumulation of biomass indicated by their increased cell size, whereas Stat5-YF caused rapid cell shrinkage ( Figure A). To determine whether the mTOR cell growth pathway was responsible for cell death induced by Stat5-CA, we tested whether the genetic deletion of Mtor or pharmacological inhibition of protein synthesis were sufficient to rescue B-ALL cell death. As expected, B-ALL cells retaining intact Mtor rapidly underwent energy crisis and cell death, while genetic deletion of Mtor reversed the toxic effects of Stat5-CA, suggesting that Stat5-CA is associated with excessive protein synthesis and defective ER turnover. Indeed, Stat5-CA increased protein synthesis rate and ER content compared to EV control, and these effects were opposed by Stat5-YF. To compare the metabolic outcomes of Stat5-CA and Stat5-YF, we performed mass spectrometry-based metabolomic analyses ( Figure B). Consistent with the role of mTOR in promoting glycolysis, Stat5-CA increased the content of glycolytic intermediates in B-ALL cells. In contrast, Stat5-YF increased phospholipid intermediates and phosphatidylethanolamine (PtdEtn). Opposed by Myc, Stat5-YF increased the expression levels of Bcl6 and autophagic genes, suggesting that Bcl6-dependent programs promote PtdEtn-LC3B conjugation, thereby autophagosome formation. As expected, microscopic validation with LC3B-GFP reporter revealed that Stat5-YF increased the number of LC3B-GFP puncta, upon pharmacological inhibition of autophagosome-lysosome fusion ( Figure A). Consistent with STAT5-CA promoting Myc- as opposed to STAT5-YF driving Bcl6-dependent programs, a flow cytometry analysis of Myc-eGFP/Bcl6-mCherry dual reporter expression in murine B-ALL cells demonstrated that changes between glycolytic Myc+ and autophagic Bcl6+ states were the direct consequence of Stat5-CA and Stat5-YF induction, respectively. Conclusions: Our results demonstrate feedback regulators of STAT5, including SOCS2 and CISH are not only biomarkers of increased oncogenic STAT5 activity and a more aggressive course of disease linked to poor overall outcomes. Importantly, negative STAT5 feedback control mechanisms are essential to enable nimble adaptations of B-ALL cells in response to fluctuations of oncogenic signaling strength and availability of nutrients during distinct metabolic states of cellular activation (MYC) and quiescence (BCL6).

CDK4/6 inhibitor-mediated cell overgrowth triggers osmotic and replication stress to promote senescence

Abnormal increases in cell size are associated with senescence and cell cycle exit. The mechanisms by which overgrowth primes cells to withdraw from the cell cycle remain unknown. We address this question using CDK4/6 inhibitors, which arrest cells in G0/G1 and are licensed to treat advanced HR+/HER2- breast cancer. We demonstrate that CDK4/6-inhibited cells overgrow during G0/G1, causing p38/p53/p21-dependent cell cycle withdrawal. Cell cycle withdrawal is triggered by biphasic p21 induction. The first p21 wave is caused by osmotic stress, leading to p38- and size-dependent accumulation of p21. CDK4/6 inhibitor washout results in some cells entering S-phase. Overgrown cells experience replication stress, resulting in a second p21 wave that promotes cell cycle withdrawal from G2 or the subsequent G1. We propose that the levels of p21 integrate signals from overgrowth-triggered stresses to determine cell fate. This model explains how hypertrophy can drive senescence and why CDK4/6 inhibitors have long-lasting effects in patients.

Gli1 marks a sentinel muscle stem cell population for muscle regeneration.

Adult skeletal muscle regeneration is mainly driven by muscle stem cells (MuSCs), which are highly heterogeneous. Although recent studies have started to characterize the heterogeneity of MuSCs, whether a subset of cells with distinct exists within MuSCs remains unanswered. Here, we find that a population of MuSCs, marked by Gli1 expression, is required for muscle regeneration. The Gli1+ MuSC population displays advantages in proliferation and differentiation both in vitro and in vivo. Depletion of this population leads to delayed muscle regeneration, while transplanted Gli1+ MuSCs support muscle regeneration more effectively than Gli1- MuSCs. Further analysis reveals that even in the uninjured muscle, Gli1+ MuSCs have elevated mTOR signaling activity, increased cell size and mitochondrial numbers compared to Gli1- MuSCs, indicating Gli1+ MuSCs are displaying the features of primed MuSCs. Moreover, Gli1+ MuSCs greatly contribute to the formation of GAlert cells after muscle injury. Collectively, our findings demonstrate that Gli1+ MuSCs represents a distinct MuSC population which is more active in the homeostatic muscle and enters the cell cycle shortly after injury. This population functions as the tissue-resident sentinel that rapidly responds to injury and initiates muscle regeneration.

Genome homeostasis defects drive enlarged cells into senescence

Cellular senescence refers to an irreversible state of cell-cycle arrest and plays important roles in aging and cancer biology. Because senescence is associated with increased cell size, we used reversible cell-cycle arrests combined with growth rate modulation to study how excessive growth affects proliferation. We find that enlarged cells upregulate p21, which limits cell-cycle progression. Cells that re-enter the cell cycle encounter replication stress that is well tolerated in physiologically sized cells but causes severe DNA damage in enlarged cells, ultimately resulting in mitotic failure and permanent cell-cycle withdrawal. We demonstrate that enlarged cells fail to recruit 53BP1 and other non-homologous end joining (NHEJ) machinery to DNA damage sites and fail to robustly initiate DNA damage-dependent p53 signaling, rendering them highly sensitive to genotoxic stress. We propose that an impaired DNA damage response primes enlarged cells for persistent replication-acquired damage, ultimately leading to cell division failure and permanent cell-cycle exit.

LOC102549726/miR-760-3p network is involved in the progression of ISO-induced pathological cardiomyocyte hypertrophy via endoplasmic reticulum stress

Pathological cardiac hypertrophy (CH) is featured by myocyte enlargement and cardiac malfunction. Multiple signaling pathways have been implicated in diverse pathological and physiological processes in CH. However, the function of LOC102549726/miR-760-3p network in CH remains unclear. Here, we characterize the functional role of LOC102549726/miR-760-3p network in CH and delineate the underlying mechanism. The expression of LncRNA LOC102549726 and hypertrophic markers was significantly increased compared to the control, while the level of miR-760-3p was decreased. Next, we examined ER stress response in a hypertrophic cardiomyocyte model. The expression of ER stress markers was greatly enhanced after incubation with ISO. The hypertrophic reaction, ER stress response, and increased potassium and calcium ion channels were alleviated by genetic downregulation of LOC102549726. It has been demonstrated that LOC102549726 functions as a competitive endogenous RNA (ceRNA) of miR-760-3p. Overexpression of miR-760-3p decreased cell surface area and substantially mitigated ER stress response; protein levels of potassium and calcium channels were also significantly up-regulated compared to the NC control. In contrast, miR-760-3p inhibition increased cell size, aggravated CH and ER stress responses, and reduced ion channels. Collectively, in this study we demonstrated that the LOC102549726/miR-760-3p network was a crucial regulator of CH development. Ion channels mediate the ER stress response and may be a downstream sensor of the LOC102549726/miR-760-3p network. Therefore, these findings advance our understanding of pathological CH and provide new insights into therapeutic targets for cardiac remodeling.

Failure to repair endogenous DNA damage in β-cells causes adult-onset diabetes in mice.

Age is the greatest risk factor for the development of type 2 diabetes mellitus (T2DM). Age-related decline in organ function is attributed to the accumulation of stochastic damage, including damage to the nuclear genome. Islets of T2DM patients display increased levels of DNA damage. However, whether this is a cause or consequence of the disease has not been elucidated. Here, we asked if spontaneous, endogenous DNA damage in β-cells can drive β-cell dysfunction and diabetes, via deletion of Ercc1, a key DNA repair gene, in β-cells. Mice harboring Ercc1-deficient β-cells developed adult-onset diabetes as demonstrated by increased random and fasted blood glucose levels, impaired glucose tolerance, and reduced insulin secretion. The inability to repair endogenous DNA damage led to an increase in oxidative DNA damage and apoptosis in β-cells and a significant loss of β-cell mass. Using electron microscopy, we identified β-cells in clear distress that showed an increased cell size, enlarged nuclear size, reduced number of mature insulin granules, and decreased number of mitochondria. Some β-cells were more affected than others consistent with the stochastic nature of spontaneous DNA damage. Ercc1-deficiency in β-cells also resulted in loss of β-cell function as glucose-stimulated insulin secretion and mitochondrial function were impaired in islets isolated from mice harboring Ercc1-deficient β-cells. These data reveal that unrepaired endogenous DNA damage is sufficient to drive β-cell dysfunction and provide a mechanism by which age increases the risk of T2DM.

Experimental studies of effects of temperature gradients on performance of pouch type large format NMC/C lithium-ion battery

Cell to pack design concept for energy storage in automotive applications leads to a substantially increased cell size that results in temperature gradients over the surface induced by non-uniform heat transfer linked to the cooling system design, which influences the cell performance. In this paper, temperature gradient effects on life performance of a large-format cell are experimentally investigated, using a developed device that can actively control appropriate gradients in the longitudinal direction and simultaneously measure the heat generation rate (HGR). Performances under uniform and non-uniform temperature conditions (MMM: uniform temperature, LMH: low-mean-high, HLH: high-low-high) are compared and quantified. At beginning of life (BOL), the low-temperature regions in the HLH and LMH conditions dominantly limit the cell capacity, and the HLH condition suppresses the HGR at high C-rates. During aging, the cell experiences a larger capacity fade and HGR increase under the HLH than MMM condition. The analyses of half coin cell, differential capacity (dQdV), dynamic resistance and impedance reveal that the attributing mechanisms are mainly the loss of Cathode active material, potentially the loss of lithium inventory, and the increase of impedances, indicating the electrochemically promoted side reactions and corrosions in the high-temperature regions of the HLH condition.

Quasi-static compressive and cyclic dynamic impact performances of vat photopolymerization 3D printed Al2O3 triply periodic minimal surface scaffolds and Al2O3/Al hybrid structures: Effects of cell size

In this study, Al2O3 triply periodic minimal surface (TPMS) scaffolds with cell sizes of 5 mm, 8.5 mm, and 12 mm were prepared by vat photopolymerization 3D printing, and Al2O3/Al ceramic-metal hybrid structures were subsequently obtained by the metal infiltration of AlSi10Mg. To investigate the influence of cell size on the mechanical properties of vat photopolymerization 3D printed Al2O3 TPMS scaffolds and Al2O3/Al hybrid structures, quasi-static compression and dynamic impact experiments were conducted, and the failure modes during experiments were discussed. It was shown that the quasi-static compression and dynamic impact properties of Al2O3 TPMS scaffolds gradually decreased with the increase in cell size, the compression strength decreased from 15.2 MPa to 8 MPa and the impact strength decreased from 37 MPa to 11 MPa, respectively, which was related to the stress transfer ability of the single cell. In contrast, the effects of cell size on the performance of Al2O3/Al hybrid structures were opposite. When the cell size increased, the quasi-static compression performances of the Al2O3/Al hybrid structure were greatly improved, and the compression strength increased from 175 MPa to 250 MPa. The impact resistances of the Al2O3/Al hybrid structure were further studied. The highest impact strength of the Al2O3/Al hybrid structure was 290.74 MPa. With the increase in cell size, the impact resistance of the Al2O3/Al hybrid structure had a gradual improvement trend. Under the cyclic impact, the Al2O3/Al hybrid structure showed a high impact strength and energy absorption capacity, which was mainly related to the metal phase content around the cell, i.e., the coherence of the metal phase. This study is believed to give help for the structural design of ceramic scaffolds and ceramic-metal hybrid structures.

Curcumin attenuates replicative senescence in human dental follicle cells and restores their osteogenic differentiation

ObjectiveThis study aimed to examine the therapeutic effects of curcumin against replicative senescence in dental follicle cells (DFCs). MethodsHuman DFCs were cultured in Dulbecco's Modified Eagle Medium with growth supplements. Replicative senescence in DFCs at different passages was assessed using β-galactosidase activity assay. Cell proliferation and size of DFCs at different passages were determined by CCK-8 kit and microscopy method, respectively. In addition, curcumin's effect on replicative senescence, cell proliferation, and size of DFCs at different passages was analyzed. Using western-blot analysis and siRNA-mediated gene silencing, we determined the molecular mechanisms involved in curcumin's effect against replicative senescence and osteogenic differentiation in DFCs at different passages. ResultsWe observed decreased proliferation and increased cell size and replicative senescence in cultured human DFCs at higher passages. Intriguingly, despite not showing any effect on cell size, curcumin (50 μM) significantly restored proliferation ability in DFCs and inhibited their replicative senescence. Concerning mechanisms, we found that curcumin inhibits replicative senescence in DFCs via down-regulation of senescence markers (P16 & P21) and restoration of proliferation markers (E2F1 & P53). Additionally, curcumin also rescued the osteogenic differentiation potential in higher-passage DFCs via restoration of osteogenic markers RUNX2 and OPN. ConclusionOur findings reveal for the first time that curcumin could act as a potential anti-senescence therapeutic for DFCs via regulation of proliferation, senescence, and osteogenic differentiation markers.

Cellular Senescence Program is Sensitive to Physical Differences in Polymeric Tissue Scaffolds.

A typical cellular senescence program involves exposing cells to DNA-damaging agents such as ionization radiation or chemotherapeutic drugs, which cause multipronged changes, including increased cell size and volume, the onset of enhanced oxidative stress, and inflammation. In the present study, we examined if the senescence onset decision is sensitive to the design, porosity, and architecture of the substrate. To address this, we generated a library of polymeric scaffolds widely used in tissue engineering of varied stiffness, architecture, and porosity. Using irradiated A549 lung cancer cells, we examined the differences between cellular responses in these 3D scaffold systems and observed that senescence onset is equally diminished. When compared to the two-dimensional (2D) culture formats, there were profound changes in cell size and senescence induction in three-dimensional (3D) scaffolds. We further establish that these observed differences in the senescence state can be attributed to the altered cell spreading and cellular interactions on these substrates. This study elucidates the role of scaffold architecture in the cellular senescence program.