Effect of sex and milk replacer with or without supplemental carnitine and arginine on growth characteristics, carcass, and meat quality of artificially reared low-birth weight pigs

This study compared milk replacer either remaining unsupplemented (CON) or supplemented with 0.5 g l-carnitine plus 16.7 g l-arginine/kg (CarArg) and fed to 48 L-BtW artificially reared piglets (24 per group) from day 7 to 28 days of age. Eight farrowing series were needed to complete the study. On day 28, the lightest piglets were slaughtered, and the heaviest pigs were weaned. The heaviest pigs were weaned on day 28 and offered free access to a starter (weaning to 25 kg body weight (BW)), grower (25-60 kg BW), and finisher diet (60 kg to 96 kg BW on day 170 of age). After euthanization on day 28 and day 170, blood was sampled for assessment of serum metabolite and hormone concentrations, and the semitendinosus muscle (STM) was weighed, and later subjected to enzyme activity analysis and assessment of myofiber characteristics. In the 170-day old pigs carcass and meat quality traits were assessed. Growth data were analyzed as a two-way ANOVA, with dietary treatment and farrowing series as fixed effects, while remaining data were analyzed with dietary treatment, sex, their interaction, and farrowing series as main factors. Dietary treatments affected (P ≤ 0.049) muscle enzyme activity at both day 28, with greater CS and LDH activities and lower HAD:CS ratio in STM light portion, and lower LDH:CS ratio in STM dark portion, and 170 of age with lower HAD:CS ratio. In the starter period, CarArg pigs had greater average daily gain (P = 0.021) and average daily feed intake (P = 0.010). At slaughter, these pigs had lower (P = 0.013) glucose and greater (P = 0.022) urea serum concentrations. However, supplementing the milk replacer with carnitine and arginine had no long-term effects on growth performance, carcass composition, and meat quality of L-BtW pigs. In addition, muscle morphology and its myofiber-related properties remained unaffected by the supplementation.

Sustainable pig diets: partial grain replacement with former food products and its impact on meat quality

This study investigated the effects of salty and sugary former foodstuff products (FFPs) on the quality traits and meat composition of 36 male castrated pigs (Swiss Large White breed) as well as sensory characteristics of the loins. The animals were fed three different diets for both the growing (G) and finishing (F) phases: (1) a standard diet (ST), 0% FFPs; (2) a diet with 30% of sugary FFPs (e.g., chocolate, biscuits, cakes) as a replacement for traditional ingredients (SU); and (3) a diet with 30% of salty FFPs (e.g., bread, pasta, and breadsticks) as a replacement for traditional ingredients (SA). For a comprehensive assessment of meat quality, protein and fat content in the LD were analyzed. AA and FA profile were determined both in the LD and backfat. Meat quality traits such as pH and temperature, thawing, cooking and drip losses, and shear force have been evaluated. Then, pork loins have been assessed for sensory attributes by a trained sensory panel. The SA diet decreased 20:5 n-3 levels (P < 0.001) in the muscle and 22:5 n-3 levels (P < 0.05) in both muscle and backfat but increased (P < 0.05) the ratio of mono-unsaturated to saturated fatty acids compared to the ST group. Both the SU and SA diets elevated (P < 0.001) the n-6:n-3 fatty acids ratio compared to the ST diet. Dietary treatments did not affect other meat quality traits. Regarding sensory attributes, the loin from pigs fed with SU and SA diets were sweeter (P < 0.001). Loins of SA pigs were more tender (P < 0.001), had a more intense pork aroma (P < 0.001) and had more flavor (P < 0.01) compared to ST loins. Overall, the use of FFPs affected the fatty acid profile of pork while improving the sensory quality of the loins, with no negative effects observed on the technological and nutritional quality of the meat.

Review: Harmonised in vitro digestion and the Ussing chamber for investigating the effects of polyphenols on intestinal physiology in monogastrics and ruminants

Because of the relevant effects of plant-derived polyphenols (PPs) on monogastrics and ruminants' nutrition, emissions and performance, an increasing number of in vivo and in vitro studies are being performed to better understand the mechanisms of action of polyphenols at both the ruminal and intestinal levels. The biological properties of these phenolic compounds strongly depend on their degradation, absorption and metabolism. The harmonised in vitro digestion method (INFOGEST) is one of the most reliable in vitro methods used to assess the bioaccessibility and or antioxidant activity of PP contained in different matrixes, as well as the interactions of PP and their degradation products with other feed ingredients. The effects of PP released from their matrix after in vitro digestion on different intestinal physiological parameters, such as epithelium integrity, can be further evaluated by the use of ex vivo models such as the Ussing chamber. This review aims to describe the combination of the INFOGEST method, coupled with the Ussing chamber as a valuable model for the digestion and subsequent effects and absorption of phenolic compounds in monogastrics and potentially in ruminants. The advances, challenges and limits of this approach are also discussed.

Accumulation and decontamination kinetics of PCBs and PCDD/Fs from grass silage and soil in a transgenerational cow-calf setting

Polychlorinated biphenyls (PCBs) and dibenzo-p-dioxins/dibenzofurans (PCDD/Fs) are bioaccumulative pollutants that endanger bovine food safety. Bioaccumulation depends, among others, on the physiological dynamics of the cow's reproductive cycle. However, recent studies have focused only on near steady-state situations. Thus, the effects of animal physiology on PCB + PCDD/F transfer from grass silage and soil to cows' blood, adipose tissue, and milk and subsequently to suckling calves during gestation and lactation were investigated. In the exposed group, nine cows ate a grass silage/contaminated soil mixture (6.6 ± 0.8 μg iPCBs and 2.6 ± 0.4 ng dlPCB + PCDD/F TEQ kg_DM^-1) for 109 days prepartum until 288 days in milk (DIM). Four of these cows underwent decontamination after DIM164, receiving the same clean grass silage as the four control cows during the experiment. Calves were fed the milk of their respective mothers. In the exposed group, transgenerational bioaccumulation occurred until DIM164, with calf blood and adipose tissue PCB + PCDD/F concentrations reaching levels twice as high as those in their respective mothers. Transfer rates from oral intake to milk ranged from 0.1 up to 42%, depending on pollutant congener, dietary treatment, and reproductive parity of the cow. Congener and parity also influenced the decontamination half-lives of milk. In decontaminated calves, declines in adipose tissue PCB + PCDD/F concentrations coincided with increases in body fat mass. Therefore, it is essential to know the physiological characteristics of cattle, exposure dose and duration, and physicochemical compound properties to perform reliable transfer assessments.

Effect of dietary L-carnitine supplementation to sows during gestation and/or lactation on sow productivity, muscle maturation and lifetime growth in progeny from large litters

Genetic selection for increased sow prolificacy has resulted in decreased mean piglet birth-weight. This study aimed to investigate the effect of L-carnitine (CAR) supplementation to sows during gestation and/or lactation on sow productivity, semitendinosus muscle (STM) maturity, and lifetime growth in progeny. Sixty-four sows were randomly assigned to one of four dietary treatments at breeding until weaning; CONTROL (0mg CAR/d), GEST (125mg CAR/d during gestation), LACT (250mg CAR/d during lactation), and BOTH (125mg CAR/d during gestation & 250mg CAR/d during lactation). The total number of piglets born per litter was greater for sows supplemented with CAR during gestation (17.3 v 15.8 ± 0.52; P<0.05). Piglet birth-weight (total and live) was unaffected by sow treatment (P>0.05). Total myofibre number (P=0.08) and the expression level of selected myosin heavy chain genes in the STM (P<0.05) was greater in piglets of sows supplemented with CAR during gestation. Pigs from sows supplemented with CAR during gestation had lighter carcasses at slaughter than pigs from non-supplemented sows during gestation (83.8 v 86.7 ± 0.86kg; P<0.05). In conclusion, CAR supplementation during gestation increased litter size at birth without compromising piglet birth-weight. Results also showed that the STM of piglets born to sows supplemented with CAR during gestation was more developed at birth. However, carcass weight at slaughter was reduced in progeny of sows supplemented with CAR during gestation. The CAR supplementation strategy applied during gestation in this study could be utilized by commercial pork producers to increase sow litter size and improve offspring muscle development.

Effect of Supplementing Hydrolysable Tannins to a Grower-Finisher Diet Containing Divergent PUFA Levels on Growth Performance, Boar Taint Levels in Back Fat and Intestinal Microbiota of Entire Males

A retrospective data analysis suggested that the levels of boar taint compounds depend on the polyunsaturated fatty acid (PUFA) level of the adipose tissue (AT) being significantly greater in the unsaturated AT. In addition, we recently reported that hydrolysable tannins (HTs) offered to entire males (EMs) reduce skatole and, to a greater extent, indole levels in the AT. Thus, the objective of the study was to determine the impact of HTs and a high dietary level of PUFA on growth performance and board taint compounds in EMs. In addition, the interaction between PUFA and HTs on gut microbiota and its link to intestinal skatole and indole production was investigated. At 25 kg BW, 44 EM originating from 11 litters were randomly assigned within litter to four dietary treatments. Two basal grower (25-60 kg BW) and finisher (60-105 kg BW) diets containing either 2% soy oil (H = high PUFA level) or 2% tallow (L = low PUFA level) were formulated. The H and L diets were either supplemented (H+/L+) or not (H-/L-) with 3% chestnut extract containing 50% HTs. The pigs had ad libitum access to the diets and were slaughtered at 170 days of age. The microbiota composition was investigated through the 16S rRNA gene sequences obtained by next-generation sequencing (Illumia MiSeq platform, San Diego, CA, USA) and analyzed with a specific packages in R, version 3.5.0. Regardless of the PUFA content, the EMs fed the H+ diets were 2% (p < 0.01) less feed efficient overall. This was due to the slower (p = 0.01) growth in the finisher period despite similar feed intake. Carcass characteristics were not affected by the diets. Regardless of HT feeding, the PUFA level in the AT of the H pigs was 10% greater (p = 0.05) than in the L pigs. The indole level tended (p = 0.08) to be 50% lower in the H+ group. Surprisingly, the pigs that were fed diet H- had greater skatole levels than those fed diet L-, with intermediate skatole levels in the H+ and L+. Independent of the PUFA level, the HTs decreased bacteria abundance and qualitatively affected the microbiota composition. In conclusion, these data do not confirm that boar taint compound levels were related to PUFA levels in the AT. However, HTs can be considered to be a promising alternative to conventional antibacterial additives, with no detrimental effects on pig gut health and with appealing properties for reducing the synthesis of the main components of boar taint.

Punicalagin increases glutamate absorption in differentiated Caco-2 cells by a mechanism involving gene expression regulation of an EAAT3 transporter

This study investigates, for the first time, the ability of punicalagin to modulate intestinal glutamate uptake by upregulation of the expression of one of its transporters present on the enterocyte membrane. The use of an Ussing chamber revealed an increase in glutamate transport in differentiated Caco-2 cells after punicalagin treatment for 24 h. This cell line constitutively expresses two glutamate transporters: EAAT1 and EAAT3. In response to punicalagin, the expression of EAAT3 was increased, at both mRNA and protein levels, but not that of EAAT1. Transfection with EAAT3-targeting siRNA specifically altered basal and induced EAAT3 gene expression, decreasing the positive effect of punicalagin on glutamate uptake. These data confirmed the involvement of EAAT3 in increasing glutamate uptake by enterocytes after punicalagin treatment.

Meat and carcass quality of Dexter cattle compared with that of suckler, Charolais-cross calves: a preliminary study

Tenderness, flavour and colour are the most important quality traits of beef that are influenced by breed and age. Suckler calves (SC) produce very tender, high-quality meat. Extensively growing, small-framed breeds are known for high-quality beef, but information about the particularly small Dexter cattle (D) is yet unavailable. Eight D and seven Charolais-crossbreed SC were kept for 11 weeks on alpine pastures to be able to compare their meat quality. The SC were kept with their dams. The animals of the two breeds were slaughtered at different ages (D: 15 months and SC: 7 months) consistent with their respective production system conventions. Although this meant that age and breed effects were confounded, slaughter took place at the same carcass fatness score, thereby avoiding a confounding effect on meat quality. Quality of the carcass and of two muscles (M. biceps femoris, M. longissimus thoracis) was analysed. Despite being older, D had lower body and carcass weights, dressing percentage and bodyweight gains than SC. Dexter meat was darker than SC meat. Shear force did not differ between D and SC in the M. longissimus thoracis but was higher in the M. biceps femoris from D than from SC. Sensory analysis by a trained panel demonstrated an overall preference for D meat, associated with more favourable flavour and juiciness. Tenderness was not rated differently. Despite the unfavourable darker colour of D compared with SC meat, its characteristic flavour might attract consumers in a high-price niche market. For a more comprehensive characterisation, sensory evaluation of additional muscles is required. Additional measurements on a larger number of animals and muscles are required.

An improved DNA method to unambiguously detect small hive beetle Aethina tumida, an invasive pest of honeybee colonies

The scavenger and invasive species Aethina tumida threatening the honey bee has been recently introduced in Europe. We present a new, reliable and rapid multiplex real-time PCR for efficient diagnostics enabling surveillance programs. © 2018 The Authors. Pest Management Science published by John Wiley & Sons Ltd on behalf of Society of Chemical Industry.

Tissue Factor Activity Is Upregulated in Human Endothelial Cells Exposed to Oscillatory Shear Stress

Hemodynamic forces play a critical role in the pathogenesis of atherosclerosis as evidenced by the focal nature of the disease. Oscillatory shear stress characterizes the hemodynamic environment of plaque-prone areas as opposed to unidirectional shear stress typical of plaque-free areas. These particular flow conditions modulate atherosclerosis-related genes. Tissue factor (TF) initiates blood coagulation, contributes to vascular remodeling, and is therefore a potential contributor in the development/progression of atherosclerosis. We investigated the effect of oscillatory and unidirectional flows on TF using an in vitro perfusion system. Human endothelial cells exposed for 24 h to oscillatory shear stress, significantly increased TF mRNA, and TF protein expression (1.5-and 1.75-fold, respectively, p <0.01), and surface TF activity (twofolds-increase). Expression of TF inhibitor (TFPI), mRNA and protein, remained unchanged as compared to static conditions. Conversely, cells exposed to unidirectional shear, showed a decrease in TF activity with a significant increase in TFPI mRNA and protein expression (1.5-and 1.8-fold, respectively, p <0.01). These results show for the first time that pulsatile oscillatory shear stress induces a procoagulant phenotype of endothelial cells which may favor formation/progression of atherothrombotic lesions.

Influence of l-carnitine and l-arginine on protein synthesis and maturation of the semitendinosus muscle of lightweight piglets

Lightweight (LW) piglets from large litters display impaired growth performance compared with heavier littermates. This study investigated the growth performance and muscle development of early-weaned LW piglets (birthweight <1.2 kg) from large litters (17.3 ± 3.0 total born per litter), fed ad libitum a milk replacer supplemented with either l-carnitine (CAR) or l-arginine (ARG) from day 7 to day 28 of age. In total, 36 female and entire male Swiss Large White piglets, weaned on day 7 of age, were artificially reared in pairs in rescue decks. They were allocated to one of three dietary treatments: unsupplemented control (CON), 0.48 g l-carnitine·piglet^-1 ·day^-1 (CAR) or 1.20 g l-arginine·kg body weight^-1 ·day^-1 (ARG). Milk replacer was prepared daily in a 1:4 powder-to-water ratio and fed ad libitum. Piglets were weighed at birth and on days 7, 14, 21 and 28. Feed intake was assessed daily. Piglets were euthanized on day 28. The entire semitendinosus muscle (STM) was collected, and organs were weighed. Subsequently, the STM was divided into the light (STM_l ) and dark (STM_d ) portion, and contractile and metabolic traits were analysed by ATP histochemistry, enzyme activities and gene expression. No differences in growth performance, organ and STM weight and on contractile traits were found between groups. A tendency (p < .10) for an elevated lipid oxidation enzyme activity in the STM_l and STM_d and greater (p < .05) phosphorylation of the mammalian target of rapamycin pathway in the STM_l of CAR compared with CON piglets was found. Despite these metabolic responses, the lack of effect of CAR and ARG supplementation on growth performance suggests that providing the milk replacer ad libitum in combination with added CAR and ARG is insufficient for eliciting faster growth of LW piglets.

Effect of nursing or mentoring by adult cows on physical activity, performance and meat quality of fattening beef calves kept on alpine pastures

BACKGROUND

Compared with weaned calves, nursed calves benefit from access to milk as nutrient-dense feed and mentoring by their dams. Both may be decisive for growth under difficult conditions such as grazing on alpine pastures, where experience could play an essential role. These factors were investigated separately by comparing nursed calves with calves weaned at 3 months of age and grazing with or without a mentor cow (n = 8 calves).

RESULTS

Weaned calves with mentor cows spent less time lying and walked more than nursed calves. Irrespective of whether they had a mentor cow or not, the weaned calves grew slower than the nursed calves (357, 428 and 1324 g day^-1 respectively). This also adversely affected slaughter weight, dressing percentage, conformation and fat cover at slaughter. In general, mentoring had no effect. Meat quality did not differ whether weaned calves were mentored or not. Nursed calves were superior in intramuscular fat content, tenderness and water-holding capacity.

CONCLUSION

The availability of milk appeared to be much more important to the calves under demanding grazing conditions than did mentoring. The differences in growth rate were accompanied by unexpectedly large differences in meat quality, showing that early weaning was not suitable for this system.© 2016 Society of Chemical Industry.

Forage legumes rich in condensed tannins may increase n-3 fatty acid levels and sensory quality of lamb meat

BACKGROUND

Tannins intensively interact with rumen microbes, which is expected to have consequences for meat quality.

RESULTS

Silages prepared from birdsfoot trefoil (BT), sainfoin (SF), alfalfa (AF) or red clover (RC) were fed alone to 48 lambs. The SF contained five times more condensed tannins than BT, the other tanniferous plant. Growth and carcass performance, but not general meat quality, was reduced with BT and SF compared to AF and RC. Lambs fed SF had half the skatole levels in the perirenal fat than AF-fed lambs. The longissimus thoracis et lumborum muscle of the SF-fed lambs, compared to RC and BT, had a lower intensity for 'livery' and 'sheepy' flavors but a stronger 'grassy' flavor. The intramuscular fat of BT- and SF-fed lambs contained less saturated and more polyunsaturated fatty acids, especially 20:4n-6, 20:3n-6, 20:5n-3 and 22:5n-3, with SF being more efficient than BT.

CONCLUSION

The SF was most promising to increase beneficial fatty acids and to reduce skatole content in lamb meat.

Microfluidic chip for monitoring Ca2+transport through a confluent layer of intestinal cells

Microfluidic-based Caco-2 culture model provides a useful tool for investigating of metabolites transport and nutrikinetics studies.

Image thresholding techniques for localization of sub-resolution fluorescent biomarkers

In this article, we explore adaptive global and local segmentation techniques for a lab-on-chip nutrition monitoring system (NutriChip). The experimental setup consists of Caco-2 intestinal cells that can be artificially stimulated to trigger an immune response. The eventual response is optically monitored using immunofluoresence techniques targeting toll-like receptor 2 (TLR2). Two problems of interest need to be addressed by means of image processing. First, a new cell sample must be properly classified as stimulated or not. Second, the location of the stained TLR2 must be recovered in case the sample has been stimulated. The algorithmic approach to solving these problems is based on the ability of a segmentation technique to properly segment fluorescent spots. The sample classification is based on the amount and intensity of the segmented pixels, while the various segmenting blobs provide an approximate localization of TLR2. A novel local thresholding algorithm and three well-known spot segmentation techniques are compared in this study. Quantitative assessment of these techniques based on real and synthesized data demonstrates the improved segmentation capabilities of the proposed algorithm.

NutriChip: nutrition analysis meets microfluidics

This focus article introduces the concept of NutriChip, an integrated microfluidic platform for investigating the potential of the immuno-modulatory function of dairy food. The core component of the NutriChip is a miniaturized artificial human gastrointestinal tract (GIT), which consists of a confluent layer of epithelial cells separated from a co-culture of immune cells by a permeable membrane. This setting creates conditions mimicking the human GIT and allows studying processes that characterize the passage of nutrients though the human GIT, including the activation of immune cells in response to the transfer of nutrients across the epithelial layer. The NutriChip project started by developing a biologically active in vitro cellular system in a commercial Transwell co-culture system. This Transwell system serves as a reference for the micro-scale device which is being developed. The microfluidic setup of NutriChip allows monitoring of the response of immune cells to pro-inflammatory stimuli, such as lipid polysaccharide (LPS), and to the application of potentially anti-inflammatory dairy food. This differential response will be quantified by measuring the variation in expression of pro-inflammatory cytokines, including interleukin 1 (IL-1) and interleukin 6 (IL-6), secreted by the immune cells, and this is achieved by using a dedicated optical imager. A series of dairy products will be screened for their anti-inflammatory properties using the NutriChip system and, finally, the outcome of the NutriChip will be validated by a human nutrition trial. Therefore, the NutriChip platform offers a new option to evaluate the influence of food quality on health, by monitoring the expression of relevant immune cell biomarkers.

Autonomous effects of shear stress and cyclic circumferential stretch regarding endothelial dysfunction and oxidative stress: an ex vivo arterial model

Cyclic circumferential stretch and shear stress caused by pulsatile blood flow work in concert, yet are very different stimuli capable of independently mediating endothelial function by modulating eNOS expression, oxidative stress (via production of superoxide anion) and NO bioavailability. Porcine carotid arteries were perfused using an ex vivo arterial support system for 72 h. Groups we created by combining normal (5%) and reduced (1%) stretch with high shear (6 +/- 3 dynes/cm(2)) and oscillatory shear (0.3 +/- 3 dynes/cm(2)) stress while maintaining a pulse pressure of 80 +/- 10 mm Hg. Oscillatory flow and reduced stretch both proved detrimental to endothelial function, whereas oscillatory flow alone dominated total endogenous vascular wall superoxide anion production. Yet, when superoxide anion production was analyzed in just the endothelial region, we observed that it was modulated more significantly by reduced cyclic stretch than by oscillatory shear, emphasizing an important distinction between shear- and stretch-mediated effects to the vascular wall. Western blotting analysis of eNOS and nitrotyrosine proved that they too are more significantly negatively modulated by oscillatory flow than by reduced stretch. These findings point out how shear and stretch stimulate regions of the vascular wall differently, affecting NO bioavailability and contributing to vascular disease.

Arterial biomechanics after destruction of cytoskeleton by Cytochalasin D

Vascular smooth muscle is a major structural element of the arterial wall. We examined the effects of cytoskeleton destruction, after administration of Cytochalasin D, on the biomechanical properties of porcine common carotids. Compared to untreated, maximally dilated controls, Cytochalasin D-treated arteries have shown a marked increase in compliance in the elastin-dominated pressure range. After weakening the VSM stress-bearing cytoskeleton by Cytochalasin D the artery would expand, reaching a new equilibrium state. This study brings further evidence that VSM is under tension, even when it is under zero load and at maximal vasodilation. This residual tension was released upon partial destruction of the cytoskeleton with Cytochalasin D. From a biomechanical standpoint, this means that the zero stress states of the in-series and parallel elastic components are substantially different.

Shear Stress and Cyclic Circumferential Stretch, But Not Pressure, Alter Connexin43 Expression in Endothelial Cells

Hemodynamic forces play a critical role in atherogenesis, as evidenced by the focal pattern of development of atherosclerotic lesions. Whereas disturbed flow in the branches and curved regions of large arteries is proatherogenic, laminar flow in the straight parts of vessels is atheroprotective. In addition, hypertension and age-related changes in arterial stiffness are important risk factors of the disease. Hemodynamic forces induce various changes in the structure and function of vascular endothelium, many of which reflect alterations in gene expression. Endothelial cells are linked by gap junctions, which facilitate the propagation of electrical and chemical signals along the vascular wall. Using an in vitro perfusion system, we investigated the effects of pulsed unidirectional and oscillatory flows in combination with different levels of hydrostatic pressure and circumferential stretch on the expression of Cx43 in endothelial cells. Our results show that shear stress and circumferential stretch, but not pressure, modulate the expression of Cx43. In view of the distribution of this protein along the vascular tree, our findings provide new insights into the role of mechanical forces on gap junctional communication in regions prone to the development of atherosclerosis.

Transcriptional and post-transcriptional regulation of preproendothelin-1 by plaque-prone hemodynamics

OBJECTIVE

Plaque-prone areas are exposed to a particular hemodynamic environment characterized by a low mean shear stress value and a cyclic reversal flow. This mechanical environment, also termed oscillatory shear stress (OSS), induces the expression of several pro-atherogenic genes in the endothelial cells including the preproendothelin-1 (ppET-1) gene. The present paper investigates the molecular mechanisms of this induction.

METHODS AND RESULTS

Several deletional mutants of ppET-1 gene promoter were cloned upstream of a luciferase gene and transiently transfected in bovine arterial endothelial cells that were further exposed to plaque-prone hemodynamics. After 24h of flow exposure, analysis of the transfected cells showed that a proximal promoter of 156 base pairs length retained OSS responsiveness. Mutation of an activator protein-1 (AP-1) binding site present in this minimal promoter completely abolished its activation by OSS. Consistently, electrophoresis mobility shift assay revealed a sustained activation of AP-1 transcription factor in endothelial cells exposed to OSS. In addition to the transcriptional activation, we demonstrated that OSS also induces a stabilization of ppET-1mRNA through the 3'-untranslated region (3'-UTR) of this gene. Fluvastatin, a drug known to improve endothelial function, was shown to prevent OSS up-regulation of the ppET-1 gene expression. Under this flow condition, fluvastatin affects ppET-1 gene expression via inhibition of its promoter activity without affecting ppET-1mRNA stability.

CONCLUSIONS

The present study demonstrate that plaque-prone hemodynamic induces ppET-1 gene expression by both transcriptional and post-transcriptional mechanisms via an activation of AP-1 transcriptional factor and stabilization of mRNA. The transcriptional up-regulation of ppET-1 was shown to be fluvastatin sensitive.

RGD—Functionalized polymer brushes as substrates for the integrin specific adhesion of human umbilical vein endothelial cells

This report demonstrates the feasibility of surface-initiated atom transfer radical polymerization to prepare thin polymer layers ("brushes") that can be functionalized with short peptide ligands and which may be of use as coatings to promote endothelialization of blood-contacting biomaterials. The brushes are composed of poly(2-hydroxyethyl methacrylate) (PHEMA) or poly(poly(ethylene glycol) methacrylate) (PPEGMA), which do not only suppress non-specific adhesion of proteins and cells but also contain hydroxyl groups that can be used to introduce small peptide ligands. A protocol has been developed that allows functionalization of the brushes with RGD containing peptide ligands resulting in surface concentrations ranging from approximately 0.5-12 pmol/cm(2). At peptide surface concentrations >1-5.3 pmol/cm(2), human umbilical vascular endothelial cells (HUVECs) were found to adhere and spread rapidly. A difference in size and morphology of focal adhesions between HUVECs immobilized on PHEMA and PPEGMA brushes was observed. It is proposed that this is due to the increased ethylene glycol spacer length and hydrophilicity of the PPEGMA brushes, which may lead to increased ligand mobility and reduced ligand-integrin affinity. HUVECs immobilized on the polymer brushes were also found to be able to retain homeostasis when exposed to shear stresses that simulated arterial blood flow.

Oscillatory shear stress and reduced compliance impair vascular functions

Shear stress has been shown to influence endothelial cell gene expression and morphology. In particular, low and bi-directional shear stress, mimicking conditions at plaque-prone areas, down-regulates the expression of several atheroprotective genes, and up-regulates that of other genes considered as pro-inflammatory. Another mechanical situation thought to have a negative influence on vascular functions is arterial stiffness. Loss of arterial compliance occurs during ageing, in diabetic as well as in hypertensive patients. In this work we investigated the effects of these two particular hemodynamic environments (bi-directional shear stress and reduced compliance), using a recently developed perfusion system allowing to expose native arteries in vitro to complex hemodynamic environments. We were able to show that both plaque-prone shear stress and reduced compliance trigger endothelial dysfunction, but via different mechanisms. Only reduced compliance affected vascular contractility, inducing a dedifferentiation of smooth muscle cells and a consequent loss of norepinephrine sensitivity.

Plaque-prone hemodynamics impair endothelial function in pig carotid arteries

Hemodynamic forces play an active role in vascular pathologies, particularly in relation to the localization of atherosclerotic lesions. It has been established that low shear stress combined with cyclic reversal of flow direction (oscillatory shear stress) affects the endothelial cells and may lead to an initiation of plaque development. The aim of the study was to analyze the effect of hemodynamic conditions in arterial segments perfused in vitro in the absence of other stimuli. Left common porcine carotid segments were mounted into an ex vivo arterial support system and perfused for 3 days under unidirectional high and low shear stress (6 ± 3 and 0.3 ± 0.1 dyn/cm2) and oscillatory shear stress (0.3 ± 3 dyn/cm2). Bradykinin-induced vasorelaxation was drastically decreased in arteries exposed to oscillatory shear stress compared with unidirectional shear stress. Impaired nitric oxide-mediated vasodilation was correlated to changes in both endothelial nitric oxide synthase (eNOS) gene expression and activation in response to bradykinin treatment. This study determined the flow-mediated effects on native tissue perfused with physiologically relevant flows and supports the hypothesis that oscillatory shear stress is a determinant factor in early stages of atherosclerosis. Indeed, oscillatory shear stress induces an endothelial dysfunction, whereas unidirectional shear stress preserves the function of endothelial cells. Endothelial dysfunction is directly mediated by a downregulation of eNOS gene expression and activation; consequently, a decrease of nitric oxide production and/or bioavailability occurs.

Arterial Wall Response to ex vivo Exposure to Oscillatory Shear Stress

BACKGROUND

The aim of this study was to analyze the arterial wall response to plaque-prone hemodynamic environments, known to occur mainly in areas of arterial trees such as bifurcations and branching points. In these areas, the vasculature is exposed to cyclically reversing flow that induces an endothelial dysfunction predisposing thus arteries to local development of atherosclerotic plaques.

METHODS

We used an ex vivo perfusion system that allows culturing arterial segments under different hemodynamic conditions. Porcine carotid arteries were exposed for 3 days to unidirectional high and low shear stress (6 +/- 3 and 0.3 +/- 0.1 dyn/cm(2)) as well as to oscillatory shear stress (0.3 +/- 3 dyn/cm(2)). This latter condition mimics the hemodynamics present at plaque-prone areas. At the end of the perfusion, the influence of different flow patterns on arterial metabolism was assessed in terms of matrix turnover as well as of smooth muscle cell function, differentiation and migration.

RESULTS

Our results show that after 3 days of perfusion none of the applied conditions influence smooth muscle cell phenotype retaining their full contraction capacity. However, an increase in the expression level of matrix metalloproteinase-2 and -9, as well as a decrease in plasminogen activator inhibitor-1 expression were observed in arteries exposed to oscillatory shear stress when compared to arteries exposed to unidirectional shear stress.

CONCLUSION

These observations suggest that plaque-prone hemodynamic environment triggers a vascular wall remodelling process and promotes changes in arterial wall metabolism, with important implication in atherogenesis.

Biomechanical proprieties of decellularized porcine common carotid arteries

To analyze the effects of decellularization on the biomechanical properties of porcine common carotid arteries, decellularization was performed by a detergent-enzymatic procedure that preserves extracellular matrix scaffold. Internal diameter, external diameter, and wall thickness were measured by optical microscopy on neighboring histological sections before and after decellularization. Rupture tests were conducted. Inner diameter and wall thickness were measured by echo tracking during pressure inflation from 10 to 145 mmHg. Distensibility and incremental elastic modulus were computed. At 10 mmHg, mean diameter of decellularized arteries was 5.38 mm, substantially higher than controls (4.1 mm), whereas decellularized and control arteries reached the same internal diameter (6.7 mm) at 145 mmHg. Wall thickness decreased 16% for decellularized and 32% for normal arteries after pressure was increased from 10 to 145 mmHg. Decellularized arteries withstood pressure >2,200 mmHg before rupture. At 145 mmHg, decellularization reduced compliance by 66% and increased incremental elastic modulus by 54%. Removal of cellular elements from media led to changes in arterial dimensions. Collagen fibers engaged more rapidly during inflation, yielding a stiffer vessel. Distensibility was therefore significantly lower (by a factor of 3) in decellularized than in normal vessels: reduced in the physiological range of pressures. In conclusion, decellularization yields vessels that can withstand high inflation pressures with, however, markedly different geometrical and biomechanical properties. This may mean that the potential use of a decellularized artery as a scaffold for the creation of xenografts may be compromised because of geometrical and compliance mismatch.

Gelsolin superfamily proteins: key regulators of cellular functions

Cytoskeletal rearrangement occurs in a variety of cellular processes and involves a wide spectrum of proteins. Among these, the gelsolin superfamily proteins control actin organization by severing filaments, capping filament ends and nucleating actin assembly [1]. Gelsolin is the founding member of this family, which now contains at least another six members: villin, adseverin, capG, advillin, supervillin and flightless I. In addition to their respective role in actin filament remodeling, these proteins have some specific and apparently non-overlapping particular roles in several cellular processes, including cell motility, control of apoptosis and regulation of phagocytosis (summarized in table 1). Evidence suggests that proteins belonging to the gelsolin superfamily may be involved in other processes, including gene expression regulation. This review will focus on some of the known functions of the gelsolin superfamily proteins, thus providing a basis for reflection on other possible and as yet incompletely understood roles for these proteins.

Functional, mechanical and geometrical adaptation of the arterial wall of a non-axisymmetric artery in vitro

OBJECTIVE

Vascular remodeling is an adaptive response to variations in the hemodynamic environment acting on the arterial wall. Remodeling translates into changes of structure, geometry and mechanical properties of the artery. Our aim was to study the remodeling response of pig right common carotid arteries in vitro.

METHODS

In vivo right carotid arteries are exposed to a non-uniform hemodynamic environment and exhibit a strong wall asymmetry in the circumferential direction that allows the study of two regions separately, as the artery remodels under in vitro perfusion. Porcine right common carotid arteries were cultured during 1 day (n = 6), 3 days (n = 6) or 8 days (n = 6) in an in vitro organ culture system, at a constant perfusion pressure of 100 mmHg. Geometrical, histological, biomechanical and biological analysis of the perfused segments was performed at the end of each study.

RESULTS

Smooth muscle cell nuclei density and wall thickness remain constant along the culture periods. Elastin and collagen are significantly redistributed to equilibrate their relative content along the vessel circumference. The distensibility profile is significantly different at day 8. Matrix metalloproteinase-2 expression and activity increase significantly at days 3 and 8.

CONCLUSION

The non-axisymmetric arterial wall adapts to a uniform hemodynamic environment by redistributing the structural components of the extracellular matrix. The changes of collagen and elastin density may result from a vascular remodeling process involving matrix metalloproteinase-2 up-regulation and enzymatic activity. The remodeling response results in a new vascular wall configuration that is more distensible at physiological pressures (30-120 mmHg) and stiffer at higher pressures.

Cap G, a gelsolin family protein modulating protective effects of unidirectional shear stress

Atherosclerosis is a progressive and complex pathophysiological process occurring in large arteries. Although it is of multifactorial origin, the disease develops at preferential sites along the vasculature in regions experiencing specific hemodynamic conditions that are predisposed to endothelial dysfunction. The exact mechanisms allowing endothelial cells to discriminate between plaque-free and plaque-prone flows remain to be explored. To investigate such mechanisms, we performed a proteomic analysis on endothelial cells exposed in vitro to these two-flow patterns. A few spots on the two-dimensional gel had an intensity that was differentially regulated by plaque-free versus plaque-prone flows. One of them was further investigated and identified as macrophage-capping protein (Cap G), a member of the gelsolin protein superfamily. A 2-fold increase of Cap G protein and a 5-fold increase of Cap G mRNA were observed in cells exposed to a plaque-free flow as compared with static cultures. This increase was not observed in cells exposed to plaque-prone flow. Plaque-free flow induced a corresponding increase in nuclear and cytoskeletal-associated Cap G. Finally, overexpression of Cap G in transfection assays increased the motility potential of endothelial cells. These observations together with the known functions of Cap G suggest that Cap G may contribute to the protective effect exerted by plaque-free flow on endothelial cells. On the contrary, in cells exposed to a plaque-prone flow, no induction of Cap G expression could be observed.

ET-1 and NOS III gene expression regulation by plaque-free and plaque-prone hemodynamic conditions

Both plaque-free and plaque-prone hemodynamic environments induce an increase in the oxidative state of endothelial cells (ECs), whereas differential gene expression regulation was described in cells exposed to these conditions. In order to investigate the role of the increased oxidative state in flow-regulation of gene expression, we first exposed EC to non-pulsed unidirectional shear stress. These conditions only slightly increases ECs oxidative state and endothelin-1 (ET-1) mRNA expression, whereas endothelial nitric oxide synthase (NOS III) mRNA level were significantly up-regulated. On the contrary, both ET-1 and NOS III gene expression were significantly induced in EC exposed to pulsed-unidirectional flow (plaque-free). Only ET-1 gene expression was up-regulated by oscillatory flow (plaque-prone). Moreover, use of an antioxidant only partially inhibited NOS III gene up-regulation by unidirectional flow, whereas it completely abrogated ET-1 gene up-regulation by unidirectional and oscillatory flows. Thus suggesting that mechanical forces regulate gene expression in ECs both via oxidative stress-dependent and -independent mechanisms.

Tissue factor activity is upregulated in human endothelial cells exposed to oscillatory shear stress

Hemodynamic forces play a critical role in the pathogenesis of atherosclerosis as evidenced by the focal nature of the disease. Oscillatory shear stress characterizes the hemodynamic environment of plaque-prone areas as opposed to unidirectional shear stress typical of plaque-free areas. These particular flow conditions modulate atherosclerosis-related genes. Tissue factor (TF) initiates blood coagulation, contributes to vascular remodeling, and is therefore a potential contributor in the development/progression of atherosclerosis. We investigated the effect of oscillatory and unidirectional flows on TF using an in vitro perfusion system. Human endothelial cells exposed for 24 h to oscillatory shear stress, significantly increased TF mRNA, and TF protein expression (1.5- and 1.75-fold, respectively, p < 0.01), and surface TF activity (twofolds-increase). Expression of TF inhibitor (TFPI), mRNA and protein, remained unchanged as compared to static conditions. Conversely, cells exposed to unidirectional shear, showed a decrease in TF activity with a significant increase in TFPI mRNA and protein expression (1.5- and 1.8-fold, respectively, p < 0.01). These results show for the first time that pulsatile oscillatory shear stress induces a pro-coagulant phenotype of endothelial cells which may favor formation/progression of atherothrombotic lesions.

Low-pressure environment and remodelling of the forearm vein in Brescia-Cimino haemodialysis access

BACKGROUND

The aim of the study was to determine which, and to what extent, haemodynamic parameters contribute to the remodelling of the venous limb of the Brescia-Cimino haemodialysis access.

METHODS

The dimensions of the radial artery and the venous limb of the haemodialysis access were measured by an echo-tracking technique. In six ESRD patients undergoing primary arteriovenous fistula (AVF) formation, vessel diameter, wall thickness, blood pressure and blood flow were measured after the operation, and at 1 and 3 months follow-up. The contralateral forearm vessels in their native position served as baseline values for comparison.

RESULTS

The diameter of the proximal antecubital vein progressively increased over the study period without reaching significant differences (4430, 5041 and 6620 microm at weeks 1, 4 and 12 respectively), whereas the intima-media thickness remained unchanged. The venous dilatation was associated with a reduction of the mean shear stress that culminated after the operation and progressively returned to normal venous values at 3 months (24.5 vs 10.4 dyne/cm(2), P<0.043). Thus the venous limb of the AVF undergoes eccentric hypertrophy as demonstrated by the increase in wall cross-sectional area (4.42 vs 6.32 mm(2) at week 1 vs week 12, P<0.028). At the time of the operation, the blood pressure in the AVF was 151+/-14/92.4+/-11 mmHg vs 49+/-19/24.5+/-6 mmHg (means+/-SEM) for the radial artery and the venous limb of the vascular access, respectively. One year after the operation the blood pressure in the venous limb had not changed: 42+/-14/25.3+/-7 mmHg (means+/-SEM). Under these conditions, the systolo-diastolic diameter changes observed in the radial artery and the antecubital vein were within a similar range at all time points: 56+/-17 vs 90+/-26 microm (means+/-SEM) at week 12.

CONCLUSIONS

The increased circumferential stress resulting from the flow-mediated dilatation rather than the elevation of blood pressure appears to represent the main contributing factor to the eccentric hypertrophy of the venous limb of Brescia-Cimino haemodialysis access.

Flow pulsatility is a critical determinant of oxidative stress in endothelial cells

Atherosclerotic plaques are found in regions exposed to disturbed flow, suggesting the active participation of the hemodynamic environment in atherogenesis. Indeed, unidirectional and oscillatory flow patterns (ie, bidirectional) have been shown to induce contrasting effects on endothelial function. The purpose of the present study was to evaluate the effect of these 2 flow patterns characterizing plaque-free and plaque-prone regions, respectively, on the oxidative stress of endothelial cells. NADH-dependent oxidase activity was shown to be equally induced (2- to 3-fold) in endothelial cells exposed to pulsatile unidirectional or oscillatory flow patterns. Under these flow conditions, an increase in endothelial cell oxidative state compared with static cultures was observed. Pulsatility of flow, but not cyclic stretch, was a critical determinant of flow-induced superoxide anion production. P22phox mRNA level increased in cells exposed to both unidirectional and oscillatory shear stress, suggesting that p22phox gene expression upregulation contributes to flow-induced increase in superoxide anion production in endothelial cells. In conclusion, we demonstrate a flow-induced increase in oxidative stress in endothelial cells. This chronic increase is dependent on the pulsatile nature of flow and is mediated in part by upregulation of an NADH-dependent oxidase expression.

Unidirectional and oscillatory shear stress differentially modulate NOS III gene expression

Atherosclerotic plaques preferentially develop in regions exposed to a low mean shear stress and cyclic reversal of flow direction (oscillatory flow). This contrasts with plaque-free zones where endothelial cells are exposed to unidirectional flow. Previous works from our laboratory using a unique experimental flow system demonstrated the existence of a differential regulation of endothelial nitric oxide synthase (NOS III) gene expression by unidirectional and oscillatory flow patterns. We further studied the possible mechanisms responsible for selective unresponsiveness of NOS III gene regulation to oscillatory flow. The results obtained demonstrate that (i) induction of the activity of the 1600-base-pair NOS III gene promoter by unidirectional and oscillatory shear stress is modulated by similar mechanisms that involve NF-kappaB activation, but do not involve Ras-dependent MAP kinase activation, and (ii) the lack of induction of NOS III gene regulation by oscillatory shear stress can be attributed to the activation of a yet unidentified negative cis-acting element present in the NOS III gene.

Nitric oxide synthase expression in endothelial cells exposed to mechanical forces

Nitric oxide (NO) has been demonstrated to play a central role in vascular biology and pathobiology. The expression of endothelial NO synthase (eNOS) is regulated in part by blood flow-induced mechanical factors. The purpose of this study was to evaluate how the expression of eNOS mRNA correlates with the activation of its promoter in both arterial and venous endothelial cells (ECs) exposed to mechanical forces, ie, shear stress and cyclic circumferential stretch. Bovine aortic ECs (BAECs) and EA hy.926, a cell line derived from human umbilical vein ECs, were grown on the inside of elastic tubes and subjected to combinations of pressure, pulsatile shear stress, and cyclic circumferential stretch for 24 hours. Two patterns of shear stress were used: unidirectional (mean of 6, ranging from 3 to 9 dyne/cm2) and oscillatory (mean of 0.3, ranging from -3 to +3 dyne/cm2). The expression of eNOS mRNA was quantified by Northern blot analysis. Activation of the promoter was assessed by luciferase activity after the cells were transiently transfected before the flow experiments with a plasmid construct containing the fully functional eNOS promoter coupled to a luciferase reporter gene. Expression of eNOS mRNA was increased and promoter activity was enhanced by unidirectional shear stress compared with static control. Oscillatory shear slightly upregulated eNOS mRNA in BAECs, whereas it downregulated eNOS mRNA in EA hy.926. In both BAECs and EA hy.926, there was a good correlation between the increase in eNOS mRNA expression and promoter activation by unidirectional shear stress. In contrast, in both BAECs and EA hy.926 cells exposed to shear stress, cyclic stretch did not change eNOS mRNA expression, but the activation of eNOS promoter was significantly lower. Moreover, when ECs were exposed to oscillatory shear stress, there was a dramatic activation of the eNOS promoter. These results demonstrate that unidirectional shear stress increases eNOS mRNA expression via a transcriptional mechanism. However, oscillatory shear stress and cyclic stretch appear to control eNOS expression through posttranscriptional regulatory events.

Interleukin (IL)-6 and its soluble receptor induce TIMP-1 expression in synoviocytes and chondrocytes, and block IL-1-induced collagenolytic activity

To define the potential role of interleukin-6 (IL-6) and its soluble receptor alpha in cartilage metabolism, we analyzed their effects on tissue inhibitor of metalloproteases (TIMP) synthesis by synoviocytes and chondrocytes. TIMP-1 production by isolated human articular synovial fibroblasts and chondrocytes, stimulated by IL-6 and/or its soluble receptor, was first assayed by specific enzyme-linked immunosorbent assay; the slight stimulatory effect of IL-6 on TIMP-1 production by both types of cells was markedly amplified by the addition of soluble receptor, the maximal secretion being observed only at 96 h. TIMP-1 mRNA expression, determined by ribonuclease protection assay, was induced by IL-6 together with its soluble receptor, but TIMP-2 and -3 mRNAs were not affected by these factors. A specific neutralizing antibody abolished the effects of the soluble receptor. Finally, supernatant from synoviocytes stimulated by IL-6 plus its soluble receptor blocked almost completely the collagenolytic activity of supernatant from IL-1-induced synoviocytes. These observations indicate that IL-6 and its soluble receptor have a protective role in the metabolism of cartilage. Given the high levels of soluble receptor in synovial fluid and the marked induction of IL-6 by IL-1 or TNF-alpha, it is likely that IL-6 and its soluble receptor are critical in controlling the catabolic effects of pro-inflammatory cytokines.

Endothelin-1 and endothelin-converting enzyme-1 gene regulation by shear stress and flow-induced pressure

Hemodynamic forces have been shown to modulate the expression of endothelin (ET-1) and endothelin-converting enzyme (ECE-1) in endothelial cells. We have subjected E.A. hy 926 cells in culture to steady fluid shear stress with and without flow-induced pressure. The effect of combining these two mechanical forces on the expression of genes in the ET system was studied and the changes were compared to the mRNA levels in static culture. Analysis of total RNA by Northern blot analysis and RNAse protection showed that steady shear stress induced ET-1 gene expression three- to fourfold in this system. The same condition had little to no effect on altering expression of ECE-1 isoforms. A range of flow-induced pressure (80-160 mm Hg) was not able to further augment ET-1 or ECE-1 gene expression. Overall, with the mechanical environment studied, we have been able to detect a predominant contribution of shear stress to altering the ET-1 gene in our system. Furthermore, this induction was independent of an alteration of ECE-1 gene levels, suggesting that these two genes have a different pattern of regulation by the same stimuli in this cell type.