Dynamic microenvironment and multiple damaged tissue regeneration in a de novo and synchronized manner

Regenerative medicine has rapidly developed over the past decade and created new opportunities to repair or replace tissue or organ function lost because of congenital defects, age, diseases, or serious damage （Cheng et al., 2016a; Cheng et al., 2016b）. Regenerative medicine strategies in- clude the transplantation of bioactive factors, stem cells, or biomaterials, even the induced regeneration in a de novo, depending on the application （Fu, 2014a; Huang and Fu, 2014）. However, there are several limitations to the use of regenerative medicine in the clinic with respect to using stem cells and biomaterials.

Selenium deficiency-induced multiple tissue damage with dysregulation of immune and redox homeostasis in broiler chicks under heat stress

Broiler chicks are fast-growing and susceptible to dietary selenium(Se) deficiency. This study sought to reveal the underlying mechanisms of how Se deficiency induces key organ dysfunctions in broilers. Day-old male chicks(n=6 cages/diet, 6 chicks/cage) were fed with a Se-deficient diet(Se-Def, 0.047 mg Se/kg) or the Se-Def+0.3 mg Se/kg(Control, 0.345 mg Se/kg) for 6weeks. The serum, liver, pancreas, spleen, heart, and pectoral muscle of the broilers were collected at week 6 to assay for Se concentration, histopathology, serum metabolome, and tissue transcriptome. Compared with the Control group, Se deficiency induced growth retardation and histopathological lesions and reduced Se concentration in the five organs. Integrated transcriptomics and metabolomics analysis revealed that dysregulation of immune and redox homeostasis related biological processes and pathways contributed to Se deficiency-induced multiple tissue damage in the broilers. Meanwhile, four metabolites in the serum, daidzein, epinephrine, L-aspartic acid and 5-hydroxyindoleacetic acid, interacted with differentially expressed genes with antioxidative effects and immunity among all the five organs, which contributed to the metabolic diseases induced by Se deficiency. Overall, this study systematically elucidated the underlying molecular mechanisms in the pathogenesis of Se deficiency-related diseases, which provides a better understanding of the significance of Se-mediated heath in animals.

Mechanisms of multiple organ damages in acute necrotizing pancreatitis

Abstract:Objective To determine the role of systemic inflammatory response syndrome (SIRS) and multiple organ dysfunction syndrome (MODS), and evaluate the progress from SIRS to MODS and the therapeutic strategies for acute necrotizing pancreatitis (ANP).Methods Rat ANP models were made by retrograde injection of 3.5% sodium taurocholate 2.5?ml/kg into the pancreatic duct. Serum interleukin-8 (IL-8), interleukin-6 (IL-6), interleukin-10 (IL-10), tumor necrosis factor-α (TNFα), amylase, endotoxin, and albumin were examined. The morphology and pathology of the pancreas, liver, lung, kidney and heart after ANP were observed. Finally, TNFα mRNA in the liver, lung, kidney and heart after ANP were observed by reverse transcriptase-polymerase chain reactions, and the efficiency of somatostatin and growth hormone were also observed in this experiment.Results ANP led to remarkable elevation of the inflammatory mediators which were positively correlated with the development of ANP and MODS. Somatostatin and growth hormone inhibited inflammatory mediators and TNFα mRNA overexpressions, reduced the risk of MODS, corrected hypoalbuminemia, reversed negative nitrogen balance, and controlled the reduction of cell groups with functions and reasonably intervened SIRS caused by ANP.Conclusion TNFα mRNA plays an important role in ANP progression. The amelioration of ANP by combination treatment with somatostatin and growth hormone leads to the reduction of complications and marked increase in survival.

Study of methods for evaluating the probability of multiple site damage occurrences

Two methods currently available for evaluating the probability of Multiple Site Damage(MSD)occurrence were studied in this paper.One of the methods is a probabilistic analysis approach based on the statistical theory and fatigue characteristics of each structural detail,and the other is an approach which defines the initial damage scenario by means of Monte-Carlo simulation,and multiple initial crack scenarios are randomly generated.A modified method based on the Monte-Carlo simulation was proposed in this paper,in which the random fluctuation of the stress was considered to give more accurate evaluation results.In the presented method,the probability of MSD occurrence in a structural element containing multiple details was calculated based on the Monte-Carlo simulation and the p-S-N curve of a single structural detail.Fatigue tests were accomplished using specimens containing 21-similar-details to obtain the fatigue life corresponding to MSD occurrence.Tests on single-detail specimens and static calibration tests were also conducted to get the basic fatigue properties of the material and the degree of stress fluctuation.The aforementioned three methods were compared and validated via the test results.The influence of the stress random fluctuation degree on the probability of MSD occurrence and influence of the distribution types on evaluating the MSD occurrence probability were discussed.

Investigating fatigue behavior of gear components with the acoustic emission technique

A novel method is presented to evaluate the complicated fatigue behavior of gears made of20Cr2Ni4 A.Fatigue tests are conducted in a high-frequency push-pull fatigue tester,and acoustic emission（AE）technique is used to acquire metal fatigue signals.After analyzing large number of AE frequency spectrum,we find that：the crack extension can be expressed as the energy of specific frequency band,which is abbreviated as F-energy.To further validate the fatigue behavior,some correlation analysis is applied between F-energy and some AE parameters.Experimental results show that there is significant correlation among the Fenergy,root mean square（RMS）,relative energy,and hits.The findings can be used to validate the effectiveness of the F-energy in predicting fatigue crack propagation and remaining life for parts in-service.F-energy,as a new AE parameter,is first put forward in the area of fatigue crack growth.

A fatigue damage-cumulative model in peridynamics

While the present structural integrity evaluation method is based on the philosophy of assumed similitude, Fatigue and Damage Tolerance(F&DT) evaluations for next generation of air-vehicles require high-fidelity physical models within cyberspace. To serve the needs of F&DT evaluation in digital twin paradigm, a fatigue damage-cumulative model within peridynamic framework is proposed in this paper. Based on the concept of fatigue element block and damage accumulation law in form of Coffin-Manson relationship, the proposed model applies to both fatigue crack initiation and fatigue crack growth;fatigue crack growth rates under constant-amplitude and simple variable-amplitude block loading cases can be well predicted for three common structural materials without inputs of Paris law parameters. Additionally, the proposed model can also be easily extended to a probabilistic version;for verification, multiple-site-damage problems are simulated and the statistic nature of fatigue process in experiments can be well captured. In the end, main features of the proposed model are summarized, and distinctions from the other models are discussed. There may be a potential for the peridynamic damage-cumulative model proposed in this work to numerically predict fatigue problems in digital twin paradigm for future generations of aerospace vehicles.