scholarly journals 3D bioprinting of bicellular liver lobule-mimetic structures via microextrusion of cellulose nanocrystal-incorporated shear-thinning bioink

2020 ◽  
Vol 10 (1) ◽  
Author(s):  
Yun Wu ◽  
Andrew Wenger ◽  
Hossein Golzar ◽  
Xiaowu (Shirley) Tang
Keyword(s):  
Cell Function ◽  
Cell Damage ◽  
Polymer Concentration ◽  
Cell Types ◽  
Shear Thinning ◽  
Biological Tissues ◽  
Cellulose Nanocrystal ◽  
3D Bioprinting ◽  
Liver Lobule ◽  
Nih 3T3

Abstract3D bioprinting of living cellular constructs with heterogeneity in cell types and extra cellular matrices (ECMs) matching those of biological tissues remains challenging. Here, we demonstrate that, through bioink material design, microextrusion-based (ME) bioprinting techniques have the potential to address this challenge. A new bioink employing alginate (1%), cellulose nanocrystal (CNC) (3%), and gelatin methacryloyl (GelMA) (5%) (namely 135ACG hybrid ink) was formulated for the direct printing of cell-laden and acellular architectures. The 135ACG ink displayed excellent shear-thinning behavior and solid-like properties, leading to high printability without cell damage. After crosslinking, the ACG gel can also provide a stiff ECM ideal for stromal cell growth. By controlling the degree of substitution and polymer concentration, a GelMA (4%) bioink was designed to encapsulate hepatoma cells (hepG2), as GelMA gel possesses the desired low mechanical stiffness matching that of human liver tissue. Four different versions of to-scale liver lobule-mimetic constructs were fabricated via ME bioprinting, with precise positioning of two different cell types (NIH/3T3 and hepG2) embedded in matching ECMs (135ACG and GelMA, respectively). The four versions allowed us to exam effects of mechanical cues and intercellular interactions on cell behaviors. Fibroblasts thrived in stiff 135ACG matrix and aligned at the 135ACG/GelMA boundary due to durotaxis, while hepG2 formed spheroids exclusively in the soft GelMA matrix. Elevated albumin production was observed in the bicellular 3D co-culture of hepG2 and NIH/3T3, both with and without direct intercellular contact, indicating that improved hepatic cell function can be attributed to soluble chemical factors. Overall, our results showed that complex constructs with multiple cell types and varying ECMs can be bioprinted and potentially useful for both fundamental biomedical research and translational tissue engineering.

Freeze-substitution of rye grass and ragweed pollen grains

1990 ◽  
Vol 48 (3) ◽  
pp. 686-687
Author(s):  
Liza B. Martinez ◽  
Susan M. Wick
Keyword(s):  
Cell Function ◽  
Pollen Grains ◽  
Freeze Substitution ◽  
Cell Types ◽  
Rapid Freezing ◽  
Rye Grass ◽  
Acrylic Resins ◽  
Allergenic Proteins ◽  
Cold Embedding ◽  
Structural Preservation

Rapid freezing and freeze-substitution have been employed as alternatives to chemical fixation because of the improved structural preservation obtained in various cell types. This has been attributed to biomolecular immobilization derived from the extremely rapid arrest of cell function. These methods allow the elimination of conventionally used fixatives, which may have denaturing or “masking” effects on proteins. Thus, this makes them ideal techniques for immunocytochemistry, in which preservation of both ultrastructure and antigenicity are important. These procedures are also compatible with cold embedding acrylic resins which are known to increase sensitivity in immunolabelling.This study reveals how rapid freezing and freeze-substitution may prove to be useful in the study of the mobile allergenic proteins of rye grass and ragweed. Most studies have relied on the use of osmium tetroxide to achieve the necessary ultrastructural detail in pollen whereas those that omitted it have had to contend with poor overall preservation.

scholarly journals Multiple Roles for Cholinergic Signaling from the Perspective of Stem Cell Function

2021 ◽  
Vol 22 (2) ◽  
pp. 666
Author(s):  
Toshio Takahashi
Keyword(s):  
Stem Cells ◽  
Stem Cell ◽  
Cell Function ◽  
Cell Activity ◽  
Embryonic Stem ◽  
Cholinergic Neurons ◽  
Cell Types ◽  
Proliferative Potential ◽  
True Nature ◽  
Cholinergic Signaling

Stem cells have extensive proliferative potential and the ability to differentiate into one or more mature cell types. The mechanisms by which stem cells accomplish self-renewal provide fundamental insight into the origin and design of multicellular organisms. These pathways allow the repair of damage and extend organismal life beyond that of component cells, and they probably preceded the evolution of complex metazoans. Understanding the true nature of stem cells can only come from discovering how they are regulated. The concept that stem cells are controlled by particular microenvironments, also known as niches, has been widely accepted. Technical advances now allow characterization of the zones that maintain and control stem cell activity in several organs, including the brain, skin, and gut. Cholinergic neurons release acetylcholine (ACh) that mediates chemical transmission via ACh receptors such as nicotinic and muscarinic receptors. Although the cholinergic system is composed of organized nerve cells, the system is also involved in mammalian non-neuronal cells, including stem cells, embryonic stem cells, epithelial cells, and endothelial cells. Thus, cholinergic signaling plays a pivotal role in controlling their behaviors. Studies regarding this signal are beginning to unify our understanding of stem cell regulation at the cellular and molecular levels, and they are expected to advance efforts to control stem cells therapeutically. The present article reviews recent findings about cholinergic signaling that is essential to control stem cell function in a cholinergic niche.

Shear-Thinning and Thermo-Reversible Nanoengineered Inks for 3D Bioprinting

2017 ◽  
Vol 9 (50) ◽  
pp. 43449-43458 ◽  
Author(s):  
Scott A. Wilson ◽  
Lauren M. Cross ◽  
Charles W. Peak ◽  
Akhilesh K. Gaharwar
Keyword(s):  
Shear Thinning ◽  
3D Bioprinting

scholarly journals Post-Transplant Diabetes Mellitus and Prediabetes in Renal Transplant Recipients: An Update

Nephron ◽  
2021 ◽  
pp. 1-13
Author(s):  
Ana Elena Rodríguez-Rodríguez ◽  
Esteban Porrini ◽  
Mads Hornum ◽  
Javier Donate-Correa ◽  
Raúl Morales-Febles ◽  
...  
Keyword(s):  
Diabetes Mellitus ◽  
Renal Transplant ◽  
Cell Function ◽  
Cell Damage ◽  
Current Evidence ◽  
Renal Transplant Recipients ◽  
Transplant Recipients ◽  
Post Transplant ◽  
Β Cell Function

Post-transplant diabetes mellitus (PTDM) is a frequent and relevant complication after renal transplantation: it affects 20–30% of renal transplant recipients and increases the risk for cardiovascular and infectious events. Thus, understanding pathogenesis of PTDM would help limiting its consequences. In this review, we analyse novel aspects of PTDM, based on studies of the last decade, such as the clinical evolution of PTDM, early and late, the reversibility rate, diagnostic criteria, risk factors, including pre-transplant metabolic syndrome and insulin resistance (IR) and the interaction between these factors and immunosuppressive medications. Also, we discuss novel pathogenic factors, in particular the role of β-cell function in an environment of IR and common pathways between pre-existing cell damage and tacrolimus-induced toxicity. The relevant role of prediabetes in the pathogenesis of PTDM and cardiovascular disease is also addressed. Finally, current evidence on PTDM treatment is discussed.

Characterization of Time-Averaged Turbulence Statistics for Shear Thinning Fluid in Horizontal Concentric Annulus Using RANS Based CFD Simulation

2016 ◽  
Author(s):  
Xiao Xiong ◽  
Mohammad Azizur Rahman ◽  
Yan Zhang
Keyword(s):  
Cfd Simulation ◽  
Model Simulation ◽  
Polymer Concentration ◽  
Shear Thinning ◽  
Turbulent Shear ◽  
Wall Region ◽  
Turbulence Statistics ◽  
Concentric Annulus ◽  
Sst Model ◽  
Shear Thinning Fluid

A RANS based shear stress transportation (SST) model was employed in this study to validate experimental results from a recent literature, which investigated the fully developed turbulent flow for a non-Newtonian shear thinning fluid, containing drag reduction polymer additives in a horizontal concentric annulus (inner to outer radio θ = 0.4). The polymer concentration varied from 0.07% V/V to 0.12% V/V and three mass flow rates from 3.92 kg/s to 5.95 kg/s were analyzed. The viscous property of the fluid was modeled by the power-law model. Simulation performed with the commercial code of ANSYS-CFX indicated that the SST model with default model constants overestimated the turbulence statistics of shear thinning flow in the near wall region where y+<60. As an effort to improve simulation accuracy, one of the model constants α1 was tuned in this study for the first time. Simulation results obtained from the modified model showed better agreement with experimental data compared to those from the default one. The present study represents a successful benchmark task for simulating turbulent shear thinning flow in concentric annuli with modified turbulence model constants.

Differential sensitivity of AS-30D rat hepatoma cells and normal hepatocytes to anoxic cell damage

1992 ◽  
Vol 262 (6) ◽  
pp. C1384-C1387 ◽  
Author(s):  
C. E. Kobryn ◽  
G. Fiskum
Keyword(s):  
Tumor Cells ◽  
Cell Damage ◽  
Metabolic Stress ◽  
Metastatic Potential ◽  
Cell Types ◽  
Hepatoma Cells ◽  
Differential Sensitivity ◽  
Trypan Blue Exclusion ◽  
Lactate Dehydrogenase Release

A substantial fraction of cells present within hard tumors experience extremely hypoxic and hypoglycemic conditions that can lead to phenotypic alterations such as increased metastatic potential and chemotherapeutic drug resistance. Little is known regarding the influence of anoxic aglycemia on tumor cell energy metabolism and viability, and no direct comparisons have been made between the effects of this form of metabolic stress on tumor cells and their tissue of origin. In this study, the effects of in vitro aglycemic incubation under N2 (with or without iodoacetate) on trypan blue exclusion, lactate dehydrogenase release, cell surface blebbing, ATP levels, and mitochondrial respiratory capacity of rat AS-30D ascites hepatoma cells and normal hepatocytes were measured. Under anoxic-aglycemic conditions, the period of incubation during which 50% viability was lost was 2 h for hepatocytes and 6-8 h for AS-30D cells. In contrast, the rate of anoxia-induced loss of ATP was comparable for the two cell types, and mitochondrial damage was actually accelerated in the tumor cells. These findings suggest that tumor cells are more resistant to anoxic cell death because of their greater ability to withstand deenergization and subcellular injury.

scholarly journals The Hypoxic Testicle: Physiology and Pathophysiology

2012 ◽  
Vol 2012 ◽  
pp. 1-15 ◽  
Author(s):  
Juan G. Reyes ◽  
Jorge G. Farias ◽  
Sebastián Henríquez-Olavarrieta ◽  
Eva Madrid ◽  
Mario Parraga ◽  
...  
Keyword(s):  
Germ Cell ◽  
Testicular Torsion ◽  
Oxygen Supply ◽  
Cell Function ◽  
Cell Damage ◽  
The Body ◽  
Body Core Temperature ◽  
Seminiferous Tubules ◽  
Low Oxygen ◽  
Complex Biological Process

Mammalian spermatogenesis is a complex biological process occurring in the seminiferous tubules in the testis. This process represents a delicate balance between cell proliferation, differentiation, and apoptosis. In most mammals, the testicles are kept in the scrotum 2 to 7°C below body core temperature, and the spermatogenic process proceeds with a blood and oxygen supply that is fairly independent of changes in other vascular beds in the body. Despite this apparently well-controlled local environment, pathologies such as varicocele or testicular torsion and environmental exposure to low oxygen (hypoxia) can result in changes in blood flow, nutrients, and oxygen supply along with an increased local temperature that may induce adverse effects on Leydig cell function and spermatogenesis. These conditions may lead to male subfertility or infertility. Our literature analyses and our own results suggest that conditions such as germ cell apoptosis and DNA damage are common features in hypoxia and varicocele and testicular torsion. Furthermore, oxidative damage seems to be present in these conditions during the initiation stages of germ cell damage and apoptosis. Other mechanisms like membrane-bound metalloproteinases and phospholipase A2 activation could also be part of the pathophysiological consequences of testicular hypoxia.

scholarly journals Visualization and Analysis of Gene Expression in Stanford Type A Aortic Dissection Tissue Section by Spatial Transcriptomics

2021 ◽  
Vol 12 ◽  
Author(s):  
Yan-Hong Li ◽  
Ying Cao ◽  
Fen Liu ◽  
Qian Zhao ◽  
Dilare Adi ◽  
...  
Keyword(s):  
Gene Expression ◽  
Aortic Dissection ◽  
Cell Structure ◽  
Type A ◽  
Cell Types ◽  
Biological Tissues ◽  
Human Aorta ◽  
Aortic Tissue ◽  
Specific Gene ◽  
Type A Aortic Dissection

Background: Spatial transcriptomics enables gene expression events to be pinpointed to a specific location in biological tissues. We developed a molecular approach for low-cell and high-fiber Stanford type A aortic dissection and preliminarily explored and visualized the heterogeneity of ascending aortic types and mapping cell-type-specific gene expression to specific anatomical domains.Methods: We collected aortic samples from 15 patients with Stanford type A aortic dissection and a case of ascending aorta was randomly selected followed by 10x Genomics and spatial transcriptomics sequencing. In data processing of normalization, component analysis and dimensionality reduction analysis, different algorithms were compared to establish the pipeline suitable for human aortic tissue.Results: We identified 19,879 genes based on the count level of gene expression at different locations and they were divided into seven groups based on gene expression trends. Major cell that the population may contain are indicated, and we can find different main distribution of different cell types, among which the tearing sites were mainly macrophages and stem cells. The gene expression of these different locations and the cell types they may contain are correlated and discussed in terms of their involvement in immunity, regulation of oxygen homeostasis, regulation of cell structure and basic function.Conclusion: This approach provides a spatially resolved transcriptome− and tissue-wide perspective of the adult human aorta and will allow the application of human fibrous aortic tissues without any effect on genes in different layers with low RNA expression levels. Our findings will pave the way toward both a better understanding of Stanford type A aortic dissection pathogenesis and heterogeneity and the implementation of more effective personalized therapeutic approaches.

scholarly journals A New Bioink For Improved 3D Bioprinting Of Bone-Like Constructs

2021 ◽  
Author(s):  
Adam Marsh ◽  
Ehsanul Hoque Apu ◽  
Marcus Bunn ◽  
Christopher H Contag ◽  
Nureddin Ashammakhi ◽  
...  
Keyword(s):  
Bioactive Glass ◽  
Rheological Properties ◽  
Cell Damage ◽  
Three Dimensional ◽  
Bone Substitutes ◽  
Tissue Loss ◽  
Major Advance ◽  
3D Bioprinting ◽  
The Matrix ◽  
Inorganic Components

Bone tissue loss can occur due to disease, trauma or following surgery, in each case treatment involving the use of bone grafts or biomaterials is usually required. Recent development of three-dimensional (3D) bioprinting (3DBP) has enabled the printing of customized bone substitutes. Bioinks used for bone 3DBP employ various particulate phases such as ceramic and bioactive glass particles embedded in the bioink creating a composite. When composite bioinks are used for 3DBP based on extrusion, particles are heterogeneously distributed causing damage to cells due to stresses created during flow in the matrix of the composite. Therefore, the objective of this study was to develop cell-friendly osteopromotive bioink mitigating the risk of cell damage due to the flow of particles. Towards this end, we have linked organic and inorganic components, gelatin methacryloyl (GelMA) and Ag-doped bioactive glass (Ag-BaG), to produce a hybrid material, GelMA-Ag-BaG (GAB). The distribution of the elements present in the Ag-BaG in the resulting hybrid GAB structure was examined. Rheological properties of the resulting hydrogel and its printability, as well as the degree of swelling and degradation over time, were also evaluated. GAB was compared to GelMA alone and GelMA-Ag-BaG nanocomposites. Results showed the superiority of the hybrid GAB bioink in terms of homogenous distribution of the elements in the structure, rheological properties, printability, and degradation profiles. Accordingly, this new bioink represents a major advance for bone 3DBP.

scholarly journals Discovering new 3D bioprinting applications: Analyzing the case of optical tissue phantoms

2018 ◽  
Vol 5 (1) ◽  
Author(s):  
Marisela Rodriguez-Salvador
Keyword(s):  
Optical Properties ◽  
3D Printing ◽  
Clinical Training ◽  
Three Dimensional ◽  
Biological Tissues ◽  
3D Bioprinting ◽  
Technology Intelligence ◽  
Biomedical Device ◽  
Tissue Phantoms ◽  
Scientific Papers

Optical tissue phantoms enable to mimic the optical properties of biological tissues for biomedical device calibration, new equipment validation, and clinical training for the detection, and treatment of diseases. Unfortunately, current methods for their development present some problems, such as a lack of repeatability in their optical properties. Where the use of three-dimensional (3D) printing or 3D bioprinting could address these issues. This paper aims to evaluate the use of this technology in the development of optical tissue phantoms. A competitive technology intelligence methodology was applied by analyzing Scopus, Web of Science, and patents from January 1, 2000, to July 31, 2018. The main trends regarding methods, materials, and uses, as well as predominant countries, institutions, and journals, were determined. The results revealed that, while 3D printing is already employed (in total, 108 scientific papers and 18 patent families were identified), 3D bioprinting is not yet applied for optical tissue phantoms. Nevertheless, it is expected to have significant growth. This research gives biomedical scientists a new window of opportunity for exploring the use of 3D bioprinting in a new area that may support testing of new equipment and development of techniques for the diagnosis and treatment of diseases.

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