Anisotropic power-law viscoelasticity of living cells is dominated by cytoskeletal network structure.

During physiological and pathological processes, cells experience significant morphological alterations with the re-arrangement of cytoskeletal filaments, resulting in anisotropic viscoelasticity. Here, a structure-based cell model is proposed to study the anisotropic viscoelastic mechanical behaviors of living cells. We investigate how cell shape affects its creep responses in longitudinal and perpendicular directions. It is shown that cells exhibit power-law rheological behavior in both longitudinal and perpendicular directions under step stress, with a more solid-like behavior along the longitudinal direction. We reveal that the cell volume and cytoskeletal filament orientation, which have been neglected in most existing models, play a critical role in regulating cellular anisotropic viscoelasticity. The stiffness of the cell in both directions increases linearly with increasing its aspect ratio, due to the decrease of cell volume. Moreover, the increase in the cell's aspect ratio produces the aggregation of cytoskeletal filaments along the longitudinal direction, resulting in higher stiffness in this direction. It is also shown that the increase in cell's aspect ratio corresponds to a process of cellular ordering, which can be quantitatively characterized by the orientational entropy of cytoskeletal filaments. In addition, we present a simple yet robust method to establish the relationship between cell's aspect ratio and cell volume, thus providing a theoretical framework to capture the anisotropic viscoelastic behavior of cells. This study suggests that the structure-based cell models may be further developed to investigate cellular rheological responses to external mechanical stimuli and may be extended to the tissue scale. STATEMENT OF SIGNIFICANCE: The viscoelastic behaviors of cells hold significant importance in comprehending the roles of mechanical forces in embryo development, invasion, and metastasis of cancer cells. Here, a structure-based cell model is proposed to study the anisotropic viscoelastic mechanical behaviors of living cells. Our study highlights the crucial role of previously neglected factors, such as cell volume and cytoskeletal filament orientation, in regulating cellular anisotropic viscoelasticity. We further propose an orientational entropy of cytoskeletal filaments to quantitatively characterize the ordering process of cells with increasing aspect ratios. Moreover, we derived the analytical interrelationships between cell aspect ratio, cell stiffness, cell volume, and cytoskeletal fiber orientation. This study provides a theoretical framework to describe the anisotropic viscoelastic mechanical behavior of cells.

Viscoelastic Multiscale Mechanical Indexes for Assessing Liver Fibrosis and Treatment Outcomes.

Understanding liver tissue mechanics, particularly in the context of liver pathologies like fibrosis, cirrhosis, and carcinoma, holds pivotal significance for assessing disease severity and prognosis. Although the static mechanical properties of livers have been gradually studied, the intricacies of their dynamic mechanics remain enigmatic. Here, we characterize the dynamic creep responses of healthy, fibrotic, and mesenchymal stem cells (MSCs)-treated fibrotic lives. Strikingly, we unearth a ubiquitous two-stage power-law rheology of livers across different time scales with the exponents and their distribution profiles highly correlated to liver status. Moreover, our self-similar hierarchical theory effectively captures the delicate changes in the dynamical mechanics of livers. Notably, the viscoelastic multiscale mechanical indexes (i.e., power-law exponents and elastic stiffnesses of different hierarchies) and their distribution characteristics prominently vary with liver fibrosis and MSCs therapy. This study unveils the viscoelastic characteristics of livers and underscores the potential of proposed mechanical criteria for assessing disease evolution and prognosis.

Frequency-dependent transition in power-law rheological behavior of living cells.

Living cells are active viscoelastic materials exhibiting diverse mechanical behaviors at different time scales. However, dynamical rheological characteristics of cells in frequency range spanning many orders of magnitude, especially in high frequencies, remain poorly understood. Here, we show that a self-similar hierarchical model can capture cell's power-law rheological characteristics in different frequency scales. In low-frequency scales, the storage and loss moduli exhibit a weak power-law dependence on frequency with same exponent. In high-frequency scales, the storage modulus becomes a constant, while the loss modulus shows a power-law dependence on frequency with an exponent of 1.0. The transition between low- and high-frequency scales is defined by a transition frequency based on cell's mechanical parameters. The cytoskeletal differences of different cell types or states can be characterized by changes in mechanical parameters in the model. This study provides valuable insights into potentially using mechanics-based markers for cell classification and cancer diagnosis.

Pubertal exposure to acrylamide disrupts spermatogenesis by interfering with meiotic progression in male mice.

Teenagers are a major group likely to love junk foods, such as potato chips and bread items, which contain high levels of acrylamide (AA). The increasing evidence suggests that AA exposure may be associated with decreased reproductive capacity in humans and animals. However, the reproductive toxicity of AA in pubertal males has not been fully elucidated. In this study, we evaluated the effects of pubertal AA exposure on adult spermatogenesis in male mice. Mice were exposed to AA at 0, 5, 10, 20, and 40 mg/kg/day by gavage from postnatal day 28 (PND28) to PND56. Our results showed that pubertal AA exposure increased apoptosis of germ cells in seminiferous tubules, decreased sperm concentration, and caused defects in sperm of adult mice. To explore the possible mechanisms of AA on spermatogenesis, the meiotic process was analyzed. The ratio of leptotene and zygotene spermatocytes increased, while the pachytene and diplotene spermatocytes decreased in AA-treated mice. Further analysis revealed that AA exposure disrupted the pattern of H2AX phosphorylation expansion, synapsis, and the crossover formation during meiotic prophase I (MPI). Taken together, these results indicate that pubertal AA exposure affects the spermatogenesis may be by disrupting the MPI progression of male mice.

A hierarchical cellular structural model to unravel the universal power-law rheological behavior of living cells.

Living cells are a complex soft material with fascinating mechanical properties. A striking feature is that, regardless of their types or states, cells exhibit a universal power-law rheological behavior which to this date still has not been captured by a single theoretical model. Here, we propose a cellular structural model that accounts for the essential mechanical responses of cell membrane, cytoplasm and cytoskeleton. We demonstrate that this model can naturally reproduce the universal power-law characteristics of cell rheology, as well as how its power-law exponent is related to cellular stiffness. More importantly, the power-law exponent can be quantitatively tuned in the range of 0.1 ~ 0.5, as found in most types of cells, by varying the stiffness or architecture of the cytoskeleton. Based on the structural characteristics, we further develop a self-similar hierarchical model that can spontaneously capture the power-law characteristics of creep compliance over time and complex modulus over frequency. The present model suggests that mechanical responses of cells may depend primarily on their generic architectural mechanism, rather than specific molecular properties.

[Atrazine changes meiosis and reduces spermatogenesis in male mice].

OBJECTIVE: To investigate the effects of exposure to atrazine on meiosis and spermatogenesis in adult male mice. METHODS: We divided 16 adult male Institute for Cancer Research (ICR) mice into a solvent control and an atrazine exposure group of an equal number and intraperitoneally injected with solvent dimethylsulfoxide (DMSO) and atrazine at 100 mg/kg/d, respectively. After 4 weeks of treatment, we obtained the body and testis weights of the mice, observed the changes in the testicular histomorphology, examined the cell apoptosis in the testis tissue, and determined the expressions of meiosis-related key genes in the spermatocytes by real-time fluorescence quantitative PCR. RESULTS: Compared with the controls, the mice treated with atrazine showed significantly less increase in the body weight (ï¼»11.2 ± 0.17ï¼½ vs ï¼»8.29 ± 0.51ï¼½ g, P < 0.05) and testis weight (ï¼»0.28 ± 0.01ï¼½ vs ï¼»0.24 ± 0.01ï¼½ g, P < 0.05), loosely arranged and thinned lumens of seminiferous tubules, disordered arrangement and reduced number of spermatogenic cells, decreased sperm concentration (ï¼»2.36 ± 0.14ï¼½ vs ï¼»0.90 ± 0.12ï¼½ ×106/ml, P < 0.01) and increased percentage of morphologically abnormal sperm in the epididymis tail (ï¼»8.60 ± 1.07ï¼½% vs ï¼»18.02 ± 1.71ï¼½%, P < 0.05), elevated apoptosis rate of spermatocytes, and down-regulated the expressions of SCP1, SCP3 and Rad51 mRNA in the spermatocytes (P < 0.05). CONCLUSIONS: Atrazine can reduce spermatogenesis in male mice by damaging testicular morphology, increasing the apoptosis of spermatocytes and down-regulating the expressions of meiosis-related genes in the spermatocytes.

Synthesis of carbonylated heteroaromatic compounds via visible-light-driven intramolecular decarboxylative cyclization of o-alkynylated carboxylic acids.

An efficient strategy for the easy access to carbonylated heteroaromatic compounds has been developed via a visible-light-promoted intramolecular decarboxylative cyclization reaction of o-alkynylated carboxylic acids. This method is characterized by its benign conditions and the tolerance to a wide range of functionalities.

Impact of polymorphisms of the DNA repair gene XRCC1 and their role in the risk of prostate cancer.

OBJECTIVE: We conducted a case-control study to examine the role of XRCC1 codons 194 (Arg>Trp), 280 (Arg>His) and 399 (Arg>Gln) polymorphisms in the risk of prostate cancer. METHODS: This study included 572 consecutive primary prostate cancer patients and 572 controls between January 2011 and January 2014. The polymerase chain reaction-restriction fragment length polymorphism (PCR-RFLP) was performed to detect XRCC1 codons 194 (Arg>Trp), 280 (Arg>His) and 399 (Arg>Gln) polymorphisms. RESULTS: Compared with the control subjects, the prostate cancer cases had a habit of cigarette smoking (χ(2)=18.13, P<0.001) and a family history of cancer (χ(2)=25.23, P<0.001). Conditional logistic regression analysis showed that the subjects carrying Trp/Trp genotype were more likely to greatly increase the prostate cancer when compared with Arg/Arg genotype, and the adjusted OR was 2.04(1.24-3.41). We did not find significant association between XRCC1 194 (Arg>Trp) polymorphism and clinical stage and Gleason score of prostate cancer (P>0.05). CONCLUSION: Our results show an increased risk for prostate cancer in individuals with XRCC1 194 (Arg>Trp) polymorphism, and a significant interaction between XRCC1 194 (Arg>Trp) polymorphism and tobacco smoking, alcohol drinking and family history of cancer.

[Inhibitory effect of inositol hexaphosphate on proliferation of LNCaP cells and its relation to IGFBP 3 expression].

OBJECTIVE: To investigate the effect of inositol hexaphosphate (IP6) on proliferation of human prostate carcinoma LNCaP cells and its relation to insulin-like growth factors binding protein-3 (IGFBP-3) expression. METHODS: The siRNA technology was used to silence the IGFBP-3 gene in LNCaP cells. LNCaP cells and IGFBP-3 gene silenced LNCaP cells were exposed to IP6 for 24 h. Cell viability was measured by MTT assay; cell cycle arrest and cell apoptosis were detected by flow cytometry. The expression levels of IGFBP-3 and Bcl-2 mRNA and protein were analyzed by real-time quantitative RT-PCR and Western blotting, respectively. RESULTS: The proliferation of LNCaP cells was be inhibited by IP6 in a dose dependent manner. After exposure to IP6 for 24 h, the cell viability in LNCaP cells and siRNA-treated LNCaP cells was 53.2%±11.6% and 82.3%±10.9%, respectively (P<0.05). After treatment of 1.5 mmol IP6，the apoptosis rate of LNCAP cells and siRNA-treated LNCAP cells was 40.48%±13.21% and 30.43%±10.65%, respectively (P<0.05). The proportion of G1 and G2 phase in LNCAP cells was 70.58%±8.25% and 5.64%±1.23%，after IP6 treatment the percentage of G1 phase cells decreased to 48.66%±11.23% and G2 phase cells increased to 31.11%±9.68%. However, for siRNA treated LNCAP cells, the proportion of G1 phase cells was 58.25%±12.36% and G2 phase cells was 23.85%±12.45%. Higher expression of IGFBP-3 and lower expression of Bcl-2 in LNCaP cells treated with IP6 were found at both mRNA and protein levels. IP6 treatment enhanced IGFBP-3 mRNA expression by 2.21±0.15 folds. In the contrast, expression of Bcl-2 mRNA decreased by 0.69±0.03 folds. Meanwhile, after IGFBP- gene silence Bcl-2 expression was not decreased. CONCLUSION: IP6 can inhibit the proliferation of LNCaP cells, which may be associated with the changes of IGFBP-3 level through Bcl-2 expression.

Quantitative assessment of the association between miR-196a2 rs11614913 polymorphism and cancer risk: evidence based on 45,816 subjects.

MicroRNAs (miRNAs) are small non-coding RNA molecules, which participate in diverse biological processes and may regulate tumor suppressor genes or oncogenes. Single nucleotide polymorphisms (SNPs) in miRNA may contribute to diverse functional consequences, including cancer development, by altering miRNA expression. Numerous studies have shown the association between miR-196a2 rs11614913 SNPs and cancer risk; however, the results are generally debatable and inconclusive, mainly due to limited statistical power. We carried out a meta-analysis of 46 studies including 20,673 cases and 25,143 controls to assess the association between the miR-196a2 rs11614913 and cancer risk by pooled odds ratios (ORs) and 95 % confidence intervals (CIs). Overall, we found a significant association between the rs11614913 (C > T) polymorphism and cancer susceptibility (recessive model, OR = 0.89, 95 % CI = 0.81-0.98). In the stratified analysis by cancer type, significant association of cancer risk was observed in lung cancer (allelic contrast, OR = 0.89, 95 % CI = 0.82-0.97; homozygote comparison, OR = 0.79, 95 % CI = 0.67-0.94; recessive model, OR = 0.84, 95 % CI = 0.74-0.96) and liver cancer (allelic contrast, OR = 0.88, 95 % CI = 0.79-0.99; homozygote comparison, OR = 0.77, 95 % CI = 0.61-0.98; heterozygote comparison, OR = 0.84, 95 % CI = 0.74-0.95; dominant model, OR = 0.82, 95 % CI = 0.73-0.92). During further stratified analysis by ethnicity, the rs11614913 polymorphism showed statistically significant association with increased risks of cancer in Asians (heterozygote model, OR = 1.15, 95 % CI = 1.01-1.30) but not in Caucasians. This meta-analysis suggests that the miR-196a2 rs11614913 polymorphism may contribute to decreased susceptibility to cancer, especially including liver cancer and lung cancer. However, it may be a risk factor for cancer development in Asians. Larger, better studies of homogeneous cancer patients are needed to further assess the correlation between this polymorphism and cancer risk.

Composition and characteristics of distinct macrophage subpopulations in the mouse thymus.

The aim of the present study was to investigate the composition, morphology, characteristics, distribution and function of distinct macrophage subpopulations in the mouse thymus. Apoptosis of mouse thymocytes was induced by glucocorticoids and three monoclonal antibodies against Mac-2, F4/80 and ED1 were used for immunofluorescence staining and immunohistochemical analysis. The morphology of thymic macrophages was examined by transmission electron microscopy. Four subpopulations of mouse thymic macrophages were identified. Dendritic macrophages were identified using anti-Mac-2 and anti-F4/80 antibodies, and were demonstrated to be distributed in the entire thymus. Phagocytes were also observed. In addition, plate-shaped macrophages, identified using the anti-F4/80 antibody, were distributed under the thymic cortex capsule. Small oval macrophages, identified using the anti-Mac-2 antibody, were distributed in the thymic medulla and corticomedullary region (CMR), while phagocytes were not observed in these types of cell. ED1+ thymic macrophages with irregular forms were distributed in the CMR. All of the four subpopulations of mouse thymic macrophages described above exhibited acid phosphate activity. This study indicated the existence of macrophage subpopulations with different shapes, distribution and functions in the mouse thymus.

[Antitumor effect of polysaccharides from cactus pear fruit in S180-bearing mice].

BACKGROUND & OBJECTIVE: Polysaccharide components of some traditional Chinese medicine have certain antitumor effects and can promote immune responses. Extractions from cactus pear fruit can inhibit the proliferation of cervical cancer, ovary cancer and bladder cancer cells, and suppress the growth of ovarian cancer in mice. This study was to observe the antitumor effect of polysaccharides extracted from cactus pear fruit in S180-bearing mice. METHODS: S180-bearing mice were established and divided into five groups: normal saline (NS) group, cyclophosphamide (CTX) group, high, middle and low dose of polysaccharide groups. Tumor inhibition rates, values of thymus index, spleen index, superoxide dismutase (SOD), maleic dialdehyde (MDA) and nitrogen monoxidum (NO) were recorded. Changes in ultra-structures of tumor cells under transmission electron microscopy were observed. RESULTS: The tumor inhibition rates in CTX group, high, middle and low dose groups were 7.78%, 31.13%%, 49.70%, 61.07%, respectively. The thymus index was significantly higher in middle and high dose groups than in NS group [(2.61+/-0.43) mg x g(-1) and (2.65+/-0.73) mg x g(-1) vs. (2.22+/-0.24) mg x g(-1), P<0.05]. The spleen index of high dose group was higher than that of NS group [(6.45+/-0.97) mg x g(-1) vs. (5.42+/-1.13) mg x g(-1),P<0.05]. SOD of middle and high dose groups [(303.12+/-13.03) U/mL and (310.03+/-18.02) U/mL] were higher than that of NS group [(280.12+/-10.01) U/mL](P<0.05). MDA was lower in low, middle and high dose groups [(6.56+/-0.75) nmol/mL, (6.24+/-1.03) nmol/mL and (5.78+/-0.90) nmol/mL, respectively] than that in NS group [(7.39+/-0.51) nmol/mL] (P<0.05). NO was lower in low, middle and high dose groups [(56.12+/-8.60) micromol/L, (50.12+/-10.05) micromol/L, (48.06+/-8.45) micromol/L respectively] than in NS group [(64.14+/-1.25) micromol/L](P<0.05). Under electron microscopy, polysaccharide or CTX treated tumor cells showed typical morphology of early apoptosis with condensed chromatin at the margins of nuclei, disintegrated nucleolus and vacuoles in the cytoplasm. CONCLUSION: Polysaccharides extracted from cactus pear fruit possess certain antitumor effects, which can induce apoptosis, increase antioxidation and promote immune responses.