Optimized vascular network by stereolithography for tissue engineered skin

This paper demonstrates the essential and efficient methods to design, and fabricate optimal vascular network for tissue engineering structures based on their physiological conditions. Comprehensive physiological requirements in both micro and macro scales were considered in developing the optimisation design for complex vascular vessels. The optimised design was then manufactured by stereolithography process using materials that are biocompatible, elastic and surface bio-coatable. The materials are self-developed photocurable resin consist of BPA-ethoxylated-diacrylate, lauryl acrylate and isobornylacrylate with Irgacure® 184, the photoinitiator. The optimised vascular vessel offers many advantages: 1) it provides the maximum nutrient supply; 2) it minimises the recirculation areas and 3) it allows the wall shear stress on the vessel in a healthy range. The stereolithography manufactured vascular vessels were then embedded in the hydrogel seeded with cells. The results of in vitro studies show that the optimised vascular network has the lowest cell death rate compared with a pure hydrogel scaffold and a hydrogel scaffold embedded within a single tube in day seven. Consequently, these design and manufacture routes were shown to be viable for exploring and developing a high range complex and specialised artificial vascular networks.

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Fibrin Hydrogels for Endothelialized Liver Tissue Engineering with a Predesigned Vascular Network

Polymers ◽

10.3390/polym10101048 ◽

2018 ◽

Vol 10 (10) ◽

pp. 1048 ◽

Cited By ~ 12

Author(s):

Xiaohong Wang ◽

Chang Liu

Keyword(s):

Liver Tissue ◽

Vascular Network ◽

Adipose Derived Stem Cells ◽

Liver Tissue Engineering ◽

Heterogeneous Tissue ◽

Design And Manufacture ◽

Permeability Evaluation ◽

First Time ◽

Complex Organ

The design and manufacture of a branched vascular network is essential for bioartificial organ implantation, which provides nutrients and removes metabolites for multi-cellular tissues. In the present study, we present a technology to manufacture endothelialized liver tissues using a fibrin hydrogel and a rotational combined mold. Both hepatocytes and adipose-derived stem cells (ADSCs) encapsulated in a fibrin hydrogel were assembled into a spindle construct with a predesigned multi-branched vascular network. An external overcoat of poly(dl-lactic-co-glycolic acid) was used to increase the mechanical properties of the construct as well as to act as an impervious and isolating membrane around the construct. Cell survivability reached 100% in the construct after 6 days of in vitro culture. ADSCs in the spindle construct were engaged into endothelial cells/tissues using a cocktail growth factor engagement approach. Mechanical property comparison and permeability evaluation tests all indicated that this was a viable complex organ containing more than two heterogeneous tissue types and a functional vascular network. It is, therefore, the first time an implantable bioartificial liver, i.e., endothelialized liver tissue, along with a hierarchical vascular network, has been created.

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Pathways of assembly of nucleohistone complexes formed in vitro under physiological conditions. Implications for the structure of the nucleosome.

Journal of Biological Chemistry ◽

10.1016/s0021-9258(17)44119-6 ◽

1983 ◽

Vol 258 (21) ◽

pp. 13321-13327 ◽

Cited By ~ 2

Author(s):

M J Ellison ◽

D E Pulleyblank

Keyword(s):

Physiological Conditions

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Regulation of Mitochondria-Associated Membranes (MAMs) by NO/sGC/PKG Participates in the Control of Hepatic Insulin Response

Cells ◽

10.3390/cells8111319 ◽

2019 ◽

Vol 8 (11) ◽

pp. 1319 ◽

Cited By ~ 5

Author(s):

Arthur Bassot ◽

Marie-Agnès Chauvin ◽

Nadia Bendridi ◽

Jingwei Ji-Cao ◽

Guillaume Vial ◽

...

Keyword(s):

Insulin Sensitivity ◽

Insulin Signaling ◽

Soluble Guanylate Cyclase ◽

Insulin Response ◽

Cyclophilin D ◽

Hepatic Insulin Sensitivity ◽

Physiological Conditions ◽

Huh7 Cells ◽

The Impact

Under physiological conditions, nitric oxide (NO) produced by the endothelial NO synthase (eNOS) upregulates hepatic insulin sensitivity. Recently, contact sites between the endoplasmic reticulum and mitochondria named mitochondria-associated membranes (MAMs) emerged as a crucial hub for insulin signaling in the liver. As mitochondria are targets of NO, we explored whether NO regulates hepatic insulin sensitivity by targeting MAMs. In Huh7 cells, primary rat hepatocytes and mouse livers, enhancing NO concentration increased MAMs, whereas inhibiting eNOS decreased them. In vitro, those effects were prevented by inhibiting protein kinase G (PKG) and mimicked by activating soluble guanylate cyclase (sGC) and PKG. In agreement with the regulation of MAMs, increasing NO concentration improved insulin signaling, both in vitro and in vivo, while eNOS inhibition disrupted this response. Finally, inhibition of insulin signaling by wortmannin did not affect the impact of NO on MAMs, while experimental MAM disruption, using either targeted silencing of cyclophilin D or the overexpression of the organelle spacer fetal and adult testis-expressed 1 (FATE-1), significantly blunted the effects of NO on both MAMs and insulin response. Therefore, under physiological conditions, NO participates to the regulation of MAM integrity through the sGC/PKG pathway and concomitantly improves hepatic insulin sensitivity. Altogether, our data suggest that the induction of MAMs participate in the impact of NO on hepatocyte insulin response.

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Reversible ATP-induced inactivation of branched-chain 2-oxo acid dehydrogenase

Biochemical Journal ◽

10.1042/bj1920155 ◽

1980 ◽

Vol 192 (1) ◽

pp. 155-163 ◽

Cited By ~ 45

Author(s):

R Odessey

Keyword(s):

Skeletal Muscle ◽

Liver Mitochondria ◽

Initial Activity ◽

Rat Skeletal Muscle ◽

Kidney Mitochondria ◽

Physiological Conditions ◽

Acid Dehydrogenase ◽

Skeletal Muscle Mitochondria ◽

Branched Chain

The branched chain 2-oxo acid dehydrogenase from rat skeletal muscle, heart, kidney and liver mitochondria can undergo a reversible activation-inactivation cycle in vitro. Similar results were obtained with the enzyme from kidney mitochondria of pig and cow. The dehydrogenase is markedly inhibited by ATP and the inhibition is not reversed by removing the nucleotide. The non-metabolizable ATP analogue adenosine 5′-[beta gamma-imido] triphosphate can block the effect of ATP when added with the nucleotide, but has no effect by itself, nor can it reverse the inhibition in mitochondria preincubated with ATP. These findings suggest that the branched chain 2-oxo acid dehydrogenase undergoes a stable modification that requires the splitting of the ATP gamma-phosphate group. In skeletal muscle mitochondria the rate of inhibition by ATP is decreased by oxo acid substrates and enhanced by NADH. The dehydrogenase can be reactivated 10-20 fold by incubation at pH 7.8 in a buffer containing Mg2+ and cofactors. Reactivation is blocked by NaF (25 mM). The initial activity of dehydrogenase extracted from various tissues of fed rats varies considerably. Activity is near maximal in kidney and liver whereas the dehydrogenase in heart and skeletal muscle is almost completely inactivated. These studies emphasize that comparisons of branched chain 2-oxo acid dehydrogenase activity under various physiological conditions or in different tissues must take into account its state of activation. Thus the possibility exists that the branched chain 2-oxo acid dehydrogenase may be physiologically regulated via a covalent mechanism.

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Selective recruitment of arrestin-3 to clathrin coated pits upon stimulation of G protein-coupled receptors

Journal of Cell Science ◽

10.1242/jcs.113.13.2463 ◽

2000 ◽

Vol 113 (13) ◽

pp. 2463-2470 ◽

Cited By ~ 1

Author(s):

F. Santini ◽

R.B. Penn ◽

A.W. Gagnon ◽

J.L. Benovic ◽

J.H. Keen

Keyword(s):

G Protein ◽

G Protein Coupled Receptors ◽

Coated Pits ◽

Over Expression ◽

Physiological Conditions ◽

A Cell ◽

G Protein Coupled ◽

Comparable Magnitude

Non-visual arrestins (arrestin-2 and arrestin-3) play critical roles in the desensitization and internalization of many G protein-coupled receptors. In vitro experiments have shown that both non-visual arrestins bind with high and approximately comparable affinities to activated, phosphorylated forms of receptors. They also exhibit high affinity binding, again of comparable magnitude, to clathrin. Further, agonist-promoted internalization of many receptors has been found to be stimulated by exogenous over-expression of either arrestin2 or arrestin3. The existence of multiple arrestins raises the question whether stimulated receptors are selective for a specific endogenous arrestin under more physiological conditions. Here we address this question in RBL-2H3 cells, a cell line that expresses comparable levels of endogenous arrestin-2 and arrestin-3. When (beta)(2)-adrenergic receptors are stably expressed in these cells the receptors internalize efficiently following agonist stimulation. However, by immunofluorescence microscopy we determine that only arrestin-3, but not arrestin-2, is rapidly recruited to clathrin coated pits upon receptor stimulation. Similarly, in RBL-2H3 cells that stably express physiological levels of m1AChR, the addition of carbachol selectively induces the localization of arrestin-3, but not arrestin-2, to coated pits. Thus, this work demonstrates coupling of G protein-coupled receptors to a specific non-visual arrestin in an in vivo setting.

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Absorption of beta-casomorphins from autoperfused lamb and piglet small intestine

AJP Gastrointestinal and Liver Physiology ◽

10.1152/ajpgi.1990.259.3.g443 ◽

1990 ◽

Vol 259 (3) ◽

pp. G443-G452 ◽

Cited By ~ 3

Author(s):

L. C. Read ◽

A. P. Lord ◽

V. Brantl ◽

G. Koch

Keyword(s):

Small Intestine ◽

Intestinal Lumen ◽

Physiological Conditions ◽

Naturally Occurring ◽

Gut Epithelium ◽

Measured Absorption ◽

Beta Casein ◽

Kinetics Of

beta-Casomorphins (beta-CMs) derived from milk beta-casein may exert various opiate activities in milk-fed infants. To assess the physiological significance of beta-CMs as a source of circulating opioids in infants, we measured absorption rates of several beta-CMs under near-physiological conditions using in situ autoperfused lamb intestine. The naturally occurring beta-CMs, beta-CM-7 and beta-CM-4-amide, were absorbed readily into blood with no transfer into lymph. Uptake peaked within several minutes of the luminal infusion of peptide but then declined sharply and stopped within a further 10-15 min. The recovery in blood, intestinal contents, and tissue at the end of the 30-min experiment was less than 1% of the infused dose. The low recovery was due to rapid proteolysis based on in vitro studies that demonstrated half-lives of less than 5 min in lamb blood, luminal contents, and lymph. The synthetic dipeptidyl peptidase IV-resistant analogue beta-[D-Ala2]CM- 4-amide was stable during incubation in blood, lymph, or luminal contents and was absorbed into blood at rates that were maximal within several minutes and remained steady for the 30-min period. We conclude that although natural beta-CMs are transferred across the lamb small intestine, rapid degradation within the intestinal lumen, gut epithelium, and blood would prevent entry into the circulation under normal conditions. Val-beta-CM-7, a putative stable precursor, had similar stability and kinetics of absorption to beta-CM-7, results that exclude Val-beta-CM-7 as a stable precursor for delivery of beta-CMs to the circulation. Essentially identical results to those in lambs were obtained in 7-day-old piglets.

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Osmotic equilibria in fibroblasts in tissue culture measured by immersion refractometry

Proceedings of the Royal Society of London Series B Biological Sciences ◽

10.1098/rspb.1958.0057 ◽

1958 ◽

Vol 149 (934) ◽

pp. 130-143 ◽

Cited By ~ 5

Keyword(s):

Water Content ◽

Osmotic Pressure ◽

Regression Line ◽

Fluid Medium ◽

Physiological Conditions ◽

Chick Heart ◽

Osmotic Behaviour ◽

Osmotic Properties ◽

Saline Medium

Volume-osmotic pressure relationships at equilibrium have been obtained in chick heart fibroblasts grown in slide-coverslip cultures in a fluid medium consisting of heparinized plasma and embryo extract. The refractive index of the fibroblast gives a direct measure of its solid concentration, and the volume is estimated as the reciprocal of concentration. The volume is found to be linearly related to the reciprocal of the osmotic pressure over a range from 130 to 587 m-osm, provided the measurements are carried out rapidly at 38°C. The isotonic water content of the cells derived from the gradient of the regression line on the basis of the simple Boyle-van’t Hoff Law was found to be less than actual water content obtained by direct refractometry, i. e. the value of Ponder’s ℛ was 0⋅94 (s. d. 0⋅04). In cultures grown in a simple saline medium and measured at 22°C the volume was related linearly to the reciprocal of the osmotic pressure only between the limits of 330 and 191 m-osm. Outside these limits the volume was greater than expected and this was attributed to alterations in the semi-permeable properties of the cell membrane. The value of Ponder’s ℛ in these cultures was 1⋅15. The importance of the quantity, ℛ, as applied to cells other than the erythrocyte, is indicated. The value, 0⋅94 (s. d. 0⋅04), obtained in fibroblasts under physiological conditions is not explicable on the basis of the probable osmotic properties in vitro of the cell proteins. The discrepancy is within the experimental error, but it may also be due to abnormal osmotic behaviour of the cell proteins resulting from some form of intermolecular structure in the cytoplasm.

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In Vitro Experimental Testing of a Cervical Implanted Unit

Key Engineering Materials ◽

10.4028/www.scientific.net/kem.399.205 ◽

2008 ◽

Vol 399 ◽

pp. 205-210

Author(s):

Dan Ioan Stoia ◽

Nicolae Faur ◽

Mirela Toth-Taşcău ◽

Laurenţiu Culea

Keyword(s):

Experimental Testing ◽

Metal Structure ◽

Anatomical Structure ◽

Loading Conditions ◽

Physiological Conditions ◽

Biomechanical Behavior ◽

Physiological Loading ◽

Extreme Load ◽

Symmetrical Loading

The paper describes the biomechanical behavior of a cervical implanted unit (CIU) in two conditions: during the physiological and extreme loading. In order to reveal these behaviors, the anatomical structure composed by the C2 and C3 cervical vertebras was implanted using a plate-screws metal structure. The implant was design to perform dynamical, by allowing longitudinal, transversal and rotational movements. The physiological conditions were simulated by the pulsatory negative loading, while the extreme loading was simulated by the alternant symmetrical loading. The tests reveal two behaviors: the durability of the CIU in the physiological loading conditions and the failure of the structure under extreme load.

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Estimating oxygen consumption rates of arteriolar walls under physiological conditions in rat skeletal muscle

AJP Heart and Circulatory Physiology ◽

10.1152/ajpheart.00830.2004 ◽

2005 ◽

Vol 289 (1) ◽

pp. H295-H300 ◽

Cited By ~ 37

Author(s):

Masahiro Shibata ◽

Shigeru Ichioka ◽

Akira Kamiya

Keyword(s):

Vascular Tone ◽

Consumption Rate ◽

Vascular Wall ◽

Surrounding Tissue ◽

Phosphorescence Quenching ◽

Physiological Conditions ◽

First Order ◽

Vascular Walls ◽

Consumption Rates

To examine the effects of vascular tone reduction on O2 consumption of the vascular wall, we determined the O2 consumption rates of arteriolar walls under normal conditions and during vasodilation induced by topical application of papaverine. A phosphorescence quenching technique was used to quantify intra- and perivascular Po2 in rat cremaster arterioles with different branching orders. Then, the measured radial Po2 gradients and a theoretical model were used to estimate the O2 consumption rates of the arteriolar walls. The vascular O2 consumption rates of functional arterioles were >100 times greater than those observed in in vitro experiments. The vascular O2 consumption rate was highest in first-order (1A) arterioles, which are located upstream, and sequentially decreased downstream in 2A and 3A arterioles under normal conditions. During papaverine-induced vasodilation, on the other hand, the O2 consumption rates of the vascular walls decreased to similar levels, suggesting that the high O2 consumption rates of 1A arterioles under normal conditions depend in part on the workload of the vascular smooth muscle. These results strongly support the hypothesis that arteriolar walls consume a significant amount of O2 compared with the surrounding tissue. Furthermore, the reduction of vascular tone of arteriolar walls may facilitate an efficient supply of O2 to the surrounding tissue.

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