Blood-perfused Model Research Articles

Evaluation of an ex vivo model of the blood-perfused equine uterus

Uterine pathologies are the most common causes of infertility in mares. This study aimed to establish an ex vivo blood-perfused model for equine uteri and investigate the possible effects of different cycle stages (estrus, diestrus and anestrus) on the applicability of the model. Uteri (n = 13) were collected at an abattoir, flushed with preservation solution, transported to the laboratory on ice, and isolated perfused with autologous blood for 6 h (n = 12). For negative control, one uterus was handled as described but left without perfusion for 6 h. The cycle stage was determined by examination of the ovaries for the presence of Graafian follicles or corpora lutea and analysis of plasma progesterone concentration (estrus: n = 4; diestrus: n = 4; anestrus: n = 4). Sonomicrometry crystals were implanted into the myometrium to record spontaneous contractions and the response to 0.5 IU oxytocin after 6 h of perfusion. Analyses of the arterial and venous perfusate were performed every hour to determine glucose consumption, lactate production, pH, lactate dehydrogenase activity (LDH), and potassium concentration (K+). Biopsy samples were obtained directly after slaughter, after transportation, after equilibration, after 4, 5, and 6 h of perfusion, and immediately after removal from the perfusion system. The uteri's glucose consumption and lactate production increased over time (p < 0.05), but no differences among cycle stages were detected. pH (arterial and venous) increased over time (p < 0.05). No changes for LDH were observed. K+ increased after 4 h of perfusion (p < 0.05), but was unaffected by the cycle stage. Spontaneous contractions were present in all perfused uteri, but myometrial activity in the negative control was limited to the 2nd hour of perfusion. No effects of cycle stage on contraction amplitude and duration after oxytocin administration were detected. The cycle stage did not affect frequency (except after 5 h of perfusion), amplitude, duration of contractions, or edema formation. Histology revealed congestion of endometrial capillaries after 4, 5, and 6 h perfusion time. In conclusion, the ex vivo model was capable of supporting the functionality of equine uteri for 6 h. However, viability and histomorphology of the endometrium appeared to be impaired after 4 h of perfusion. Effects of the cycle stage on the applicability of the model were absent.

Towards the Robust and Effective Design of Hyperthermic Devices: Improvement of a Patch Antenna for the Case Study of Abdominal Rhabdomyosarcoma With 3D Perfusion

This work addresses the challenge of deriving a simple but effective multi-physic model useful for the design and simulation of hyperthermia devices for ensuring a high-quality treatment. An existing compact patch antenna working at 434 MHz is re-designed using the proposed methodology. The proposed general approach is used to investigate the specific case of the hyperthermia treatment of abdominal rhabdomyosarcoma. Instead of using patient-specific geometries with discrete vascular tree models, a surface phantom with a continuum 3D blood perfusion model of tumors is used. The geometrical parameters of the antennas are selected to provide a robust design against the variation of the phantom parameters. The effectiveness of the antenna is evaluated simulating the treatment with a recent non-linear multi-physic model, considering the different description of tumor vasculature. A more robust and effective design is obtained, with respect to its previous version. Indeed, the antenna bandwidth is increased with about 7%. The treatment performed using the old version of the antenna lead to unsuccessful results (40 °C after 60 min), whilst the novel robust design could successfully treat the target region. The new version of the patch can withstand a temperature of 42.5 °C for 60 min of treatment. To further enhance the effectiveness of the treatment, the use of a time-modulated power is studied. The proposed model could be extended to different body regions and used to develop an application-oriented design of antennas for hyperthermia treatment.

Cardiac thermal pulse at the neck-skin surface as a measure of stenosis in the carotid artery

In this study, a cardiac thermal pulse evaluation-based carotid artery stenosis detection method is proposed. It is postulated that the presence of stenosis in the carotid artery results in a thermal lag in skin temperature at the neck skin surface that can be quantified to the degree of stenosis. A finite volume method-based transient bioheat transfer study was performed on a carotid artery-jugular vein 3-Dimensional (3D) geometry model encapsulated by the neck tissue. As the transient physiological blood flow in the carotid artery thermally interacts with the blood perfusion in the neck tissue, a thermal fluctuation or cardiac thermal pulse is resulted in the top-neck skin localized surface temperature contours. Two tissue blood perfusion models, constant (temperature-independent) and varying (temperature-dependent), were used to comparatively study the cardiac thermal pulse characterized by their signal noise. For 0% stenosis case, compared to the constant perfusion model, the average instantaneous noise for the varying perfusion model was found to be significantly lower (0.02 ± 0.01 versus 0.05 ± 0.01, p < 0.01). Furthermore, varying degrees of stenosis (25%, 50%, and 75%) were introduced in the carotid artery to study their effect on the cardiac thermal pulse. It was observed that there is a successive shift in the phase of the cardiac thermal pulse with an increase in the degree of stenosis in the carotid artery. This study demonstrates the potential of a cardiac thermal pulse evaluation-based indirect screening tool for carotid artery stenosis.

Finite volume analysis of the temperature distribution during transurethral resection of the prostate

Abstract In prostate surgery the transurethral resection (TURP) represents the gold standard which is based on monopolar (M-TURP) and bipolar techniques (TURis). The investigation of the thermal behavior is one of the most important research topics in this type of surgery procedures. Here monopolar systems have been well investigated. The research on electrical and thermal behavior of bipolar systems was initiated about two decades ago. Previous studies focused on thermal behavior according to Joule heating, but did not gain information about the temperature distribution close to the active electrode of the resectoscope. Therefore, the numerical simulations on the temperature distribution near the active electrode of the resectoscope with a finite volume method are presented in this study, which takes blood perfusion into account. The results have shown that the influence of the blood perfusion process can be ignored for regions which are more than 0.4 mm away from the active electrode. This is based on two different blood perfusion models.

MSPSF: A Multi-Scale Local Intensity Measurement Function for Segmentation of Breast Thermogram

Accurate segmentation of region(s) of abnormality (RoAs) in a grayscale breast thermogram is an essential step in the automated identification of cancer in the breast. However, low contrast, intensity nonuniformity, noise, and complex background pose challenges to this segmentation task. To overcome those challenges, a novel segmentation method that amalgamates the breast blood perfusion (BBP) model, an adaptive triangular histogram-based thresholding (ATHT) method, and a new energy functional-based level set method (LSM) is proposed here. The BBP model improves the contrast between the RoA and normal tissue region in grayscale breast thermogram. The ATHT method is used for robust initialization of the proposed LSM. To deal with the complexity caused by intensity nonuniformity and noise, we have formulated a new multiscale local intensity measurement function, called multiscale spatially weighted pixel-contribution and shape-feature-embedded force (MSPSF), which is then incorporated into a variational level set formulation and minimized using interleaved operations of the level set function to segment the RoAs accurately. Extensive experimentation on two different databases justifies the superiority of our segmentation method over the other widely used state-of-the-art segmentation methods on the basis of different qualitative and quantitative measures. We have also proposed a novel two-stage breast abnormality prediction framework based on the segmented RoA.

A Blood Perfusion Model of a RMS Tumor in a Local Hyperthermia Multi-Physic Scenario: A Preliminary Study

Hyperthermia concerns the heating treatment of cancerous tissues, mostly using a radiator, i.e., an antenna, as a heat source. The main goal of this therapy, primarily used as adjuvant therapy along with radio and chemotherapy, is to reach a suitable temperature inside the neoplastic mass—about 7–8° above the normal body temperature—which can kill the cancerous cells without compromising the healthy tissues. Many factors contribute to this goal, such as the radiation characteristics of the antenna, the thermal profiles of the healthy and cancerous tissues, and the dynamic of the water flux inside the bolus. Moreover, despite being often overlooked, an important role is played by the perfusion characteristics of the tumor. In this work, we present a preliminary multi-physic analysis in a local hyperthermia scenario, considering a simple patch antenna resonating at 434 MHz as a heat source, a water bolus, a bi-layered body phantom, and, most importantly, a specific tumor (rhabdomyosarcoma) placed inside the phantom described employing a realistic space-dependent blood perfusion model. The results of this study show the effectiveness of the hyperthermia treatment using the physiopathology-driven perfusion model, and they may be useful in a real local hyperthermia case.

Extracellular vesicles from human saliva promote hemostasis by delivering coagulant tissue factor to activated platelets

Background Extracellular vesicles (EVs) from human saliva expose coagulant tissue factor (TF). Whether such TF-exposing EVs contribute to hemostasis, however, is unknown. Recently, in a mice model, tumor cell-derived EVs were shown to deliver coagulant TF to activated platelets at a site of vascular injury via interaction between P-selectin glycoprotein ligand-1 (PSGL-1) and P-selectin. Objectives We hypothesized that salivary EVs may deliver coagulant TF to activated platelets via interaction with P-selectin. Methods We investigated the presence of two ligands of P-selectin on salivary EVs, PSGL-1 and CD24. Results Salivary EVs expose CD24 but PSGL-1 was not detected. Immune depletion of CD24-exposing EVs completely abolished the TF-dependent coagulant activity of cell-free saliva, showing that coagulant TF and CD24 co-localize on salivary EVs. In a whole blood perfusion model, salivary EVs accumulated at the surface of activated platelets and promoted fibrin generation, which was abolished by an inhibitory antibody against human CD24. Conclusions A subset of EVs in human saliva expose coagulant TF and CD24, a ligand of P-selectin, suggesting that such EVs may facilitate hemostasis at a site of skin injury where the wound is licked in a reflex action.

A haemocompatible and scalable nanoporous adsorbent monolith synthesised using a novel lignin binder route to augment the adsorption of poorly removed uraemic toxins in haemodialysis

Nanoporous adsorbents are promising materials to augment the efficacy of haemodialysis for the treatment of end stage renal disease where mortality rates remain unacceptably high despite improvements in membrane technology. Complications are linked in part to inefficient removal of protein bound and high molecular weight uraemic toxins including key marker molecules albumin bound indoxyl sulphate (IS) and p-cresyl sulphate (PCS) and large inflammatory cytokines such as IL-6. The following study describes the assessment of a nanoporous activated carbon monolith produced using a novel binder synthesis route for scale up as an in line device to augment haemodialysis through adsorption of these toxins. Small and large monoliths were synthesised using an optimised ratio of lignin binder to porous resin of 1 in 4. Small monoliths showing combined significant IS, p-CS and IL-6 adsorption were used to measure haemocompatibility in an ex vivo healthy donor blood perfusion model, assessing coagulation, platelet, granulocyte, T cells and complement activation, haemolysis, adsorption of electrolytes and plasma proteins. The small monoliths were tested in a naive rat model and showed stable blood gas values, blood pressure, blood biochemistry and the absence of coagulopathies. These monoliths were scaled up to a clinically relevant size and were able to maintain adsorption of protein bound uraemic toxins IS, PCS and high molecular weight cytokines TNF-α and IL-6 over 240 min using a flow rate of 300 ml min−1 without platelet activation. The nanoporous monoliths where haemocompatible and retained adsorptive efficacy on scale up with negligible pressure drop across the system indicating potential for use as an in-line device to improve haemodialysis efficacy by adsorption of otherwise poorly removed uraemic toxins.

Lung xenotransplantation: a review.

This article reviews recent progress in the field of lung xenotransplantation, including mechanisms of xenograft injury, and the influence of mechanism-directed genetic modifications and other interventions that may soon enable therapeutic use of pig lungs in humans. An extensive series of lung xenotransplantation experiments demonstrates that multiple genetic modifications targeting known xenogeneic lung injury mechanisms are associated with incremental improvements in lung survival or function. Addition of human complement (hCD46, hCD55), coagulation (hEPCR, hTBM, hTFPI, hCD39), or anti-inflammatory pathway regulatory genes (HO-1, HLA-E), and GalT and Neu5Gc gene knockout has each demonstrated protective effects on lung survival or function. In addition, drug treatments targeting key inflammatory and clotting pathways have been shown to attenuate residual mechanisms of lung injury. Work with other pig organs in primate models show that regimens based on costimulatory pathway blocking antibodies prolong xenograft function for months to years, suggesting that once initial lung inflammation mechanisms are fully controlled, clinically useful application of pig lung xenografts may soon be feasible. Genetic modification of pigs coupled with drugs targeting complement activation, coagulation, and inflammation have significantly increased duration of pig lung function in ex-vivo human blood perfusion models, and life-supporting lung xenograft survival in vivo.

Measuring different oxygenation levels in a blood perfusion model simulating the human head using NIRS

Abstract The oxygenation, perfusion and metabolism of the brain - segmented in both hemispheres - can be estimated from the oxygenation and hemoglobin levels of the venous blood in the cerebral efferent vessels. We present a phantom based model to simulate the anatomical target region which was connected to hemodynamic perfusion circuit to provide different oxygenation rates inside of the simulated target vessel (measurement cell) reproducible. A triple-wavelength (770, 808 and 850 nm) multi-distance NIRS sensor (6 photodiodes, linearly arranged, separated 6 mm each) was used to detect these different saturation levels. The results illustrate the capability to measure the optical property variation of hemoglobin due to oxygenation and deoxygenation processes in a specific vessel. Based on these first results a series of measurements is introduced to correlate the amount of reflected light to the actual oxygen saturation of the blood.

Quantitative assessment of myocardial perfusion by magnetic resonance imaging in the isolated porcine heart

Background Perfusion imaging visualizes early changes within the ischaemic cascade and has been shown to accurately detect significant coronary artery stenoses. First pass myocardial perfusion CMR yields high spatial resolution and permits quantification of myocardial blood flow. However, perfusion-CMR has only been validated in a small number of previous studies and using relatively early perfusion methods. An isolated blood-perfused MR compatible porcine heart model which can be imaged by identical equipment used for humans has been recently proposed. The model permits full control of regional myocardial blood flow, thus providing a valuable tool for the validation of quantitative perfusion assessment.

An isolated pig heart for the development, validation and translation of novel magnetic resonance techniques

Introduction Novel magnetic resonance (MR) techniques and imaging biomarkers are often validated in small animal models or empirically in patients. The direct translation of small animal cardiac MR imaging protocols to humans is rarely possible, while validation of novel imaging techniques in humans by tracking changes in MR biomarkers in response to externally controlled changes in blood flow, for example, is difficult, or unethical. An isolated bloodperfused pig heart model which closely resembles human physiology, anatomy and size, can be exquisitely controlled in terms of regional blood flow, oxygenation, afterload and workload, and can be imaged by the same equipment used for humans. It would therefore be a valuable tool for the development, validation and translation of novel magnetic resonance techniques.

Heme oxygenase does not contribute to control of basal vascular tone in isolated blood-perfused rat lung

Background Vasoconstriction in pulmonary ischemia–reperfusion injury may involve dysfunction of the physiologic vasodilation of pulmonary arteries. Little is known of the relative importance of heme oxygenase (HO)/carbon monoxide (CO)-dependent vs nitric oxide synthase (NOS)/nitric oxide (NO)-dependent vasodilation of the pulmonary vasculature. We evaluated the significance of HO function on basal pulmonary vascular resistance (PVR) and compared it with the function of NOS. Methods Using an isolated blood-perfusion model, lungs of Lewis rats were assigned to 3 groups ( n = 6/group). After stabilization, either an inhibitor of HO (tin-protoporphyrin-9 [SnPP-9]) or an inhibitor of NOS (NG-nitro- l-arginine methylester [ l-NAME]) was added to the perfusate (50 μmol/liter and 1 mmol/liter as the final concentration, respectively). Lungs receiving saline served as controls. Gas exchange, hemodynamic and respiratory functions and the levels of cyclic 3′,5′-guanosine monophosphate (cGMP) in the perfusate were measured. Results Inhibition of NOS by l-NAME resulted in a significant ( p < 0.01) increase in PVR (ΔPVR: 0.110 ± 0.012 cm H 2O/ml · min) within 5 minutes. In contrast, PVR was minimally affected by SnPP-9 (ΔPVR: 0.005 ± 0.005 cm H 2O/ml · min), which was comparable to control lungs (ΔPVR: 0.012 ± 0.005 cm H 2O/ml · min). The level of cGMP in the perfusate 5 minutes after drug application was markedly, but not significantly, lower in the l-NAME group (1.67 ± 0.74 nmol/liter) when compared with controls (2.69 ± 0.89 nmol/liter) and SnPP-9-treated lungs (2.65 ± 0.66 nmol/liter). Conclusions NOS but not HO contributes to the control of basal vascular tone in the rat lung.

Iloprost ameliorates post-ischemic lung reperfusion injury and maintains an appropriate pulmonary ET-1 balance

Background: Ischemia–reperfusion (I/R) injury of the lung involves increased pulmonary vascular resistance. Prostaglandins are thought to have a beneficial effect in lung transplantation, but their mechanism in I/R injury is unknown. We investigated whether iloprost, a stable prostacyclin analogue, prevents I/R-associated pulmonary vascular dysfunction and whether it affects endothelin-1 (ET-1) balance. Methods: In an isolated blood-perfusion model, we subjected lungs of Lewis rats to 45 minutes of ischemia at 37°C and randomly allocated the lungs to 3 groups ( n = 6 each): iloprost (33.3 nmol/liter) added to the perfusate before ischemia and reperfusion (ILO+IR), iloprost (33.3 nmol/liter) given only before reperfusion (ILO+R), and controls without iloprost treatment (ILO−). Results: Reperfusion induced marked pulmonary edema in non-treated controls (ILO−), which was attenuated in ILO+R lungs and completely prevented in ILO+IR lungs. At 60 minutes reperfusion, arterial oxygen tension was significantly greater in both ILO+R and ILO+IR lungs compared with ILO− controls. Mean pulmonary artery pressure and pulmonary vascular resistance were slightly decreased in the ILO+R and significantly decreased in the ILO+IR group compared with the ILO− controls. Plasma levels of big ET-1, measured in both afferent and efferent blood, showed that I/R results in increased pulmonary venous levels of big ET-1. Interestingly, the increased venoarterial ET-1 gradient in ILO− lungs decreased significantly in the ILO+IR group. Conclusions: We demonstrated in an isolated lung perfusion model that iloprost ameliorates post-ischemic lung reperfusion injury and maintains an appropriate pulmonary ET-1 balance.

Diazoxide amelioration of myocardial injury and mitochondrial damage during cardiac surgery

Background Recently, we have shown that the selective opening of mitochondrial ATP-sensitive potassium channels with diazoxide significantly decreases myocardial injury. The purpose of this study was to determine the effects of diazoxide on apoptosis and the mechanisms modulating apoptosis and myocardial injury in a blood-perfused model of acute myocardial infarction. Methods Pigs (32 to 42 kg) undergoing total cardiopulmonary bypass underwent left anterior descending coronary artery occlusion for 30 minutes. The aorta was cross-clamped and magnesium-supplemented potassium cold-blood cardioplegia (DSA; n = 6) or magnesium-supplemented potassium cardioplegia containing 50 μmol/L diazoxide (DZX; n = 6) was administered, followed by 30 minutes of global ischemia and 120 minutes of reperfusion. Left ventricular tissue samples from DSA and DZX hearts were obtained after reperfusion. Apoptosis was determined by TUNEL, caspase-3 and PARP cleavage, and caspase-3 activity. Bax and bcl-2 levels were determined and tissue morphology was examined by light and transmission electron microscopy. Results Apoptosis, as estimated by TUNEL-positive nuclei/3,000 myocardial cells, was 120.3 ± 48.8 in DSA hearts and was significantly decreased to 21.4 ± 5.3 in DZX hearts ( p < 0.05 vs control). Caspase-3 and poly-ADP-ribose polymerase cleavage and pro-apoptotic bax protein levels were significantly decreased with diazoxide ( p < 0.05 vs DSA). Light and transmission electron microscopy indicated severe disruption of tissue with capillary dilatation, mitochondrial cristae damage, and evidence of increased presence of mitochondrial granules in DSA as compared with DZX hearts. Conclusions The addition of diazoxide (50 μmol/L) to cardioplegia significantly decreases regional myocardial apoptosis and mitochondrial damage, and provides an additional modality for achieving myocardial protection.

Plasma versus Whole Blood Perfusion in a Bioartificial Liver Assist Device

The ramifications of using whole blood or plasma for perfusion off an hepatocyte containing bioartificial liver bioreactor in which the hepatocytes are separated by a membrane or other physical barrier from the perfusate stream on the rate of change of patient blood concentrations are explored through dynamic modeling of whole blood perfusion as a two compartment system (patient tissue and blood compartments), and plasma perfusion as a three compartment system (patient tissue and blood compartments, and a plasma reservoir). The whole blood perfusion model is described by three dimensionless parameters: the Damkohler number, Da, which represents the ratio of the rate of conversion by the bioreactor to the rate of perfusion; kappa, which represents the ratio of the rate of internal reequilibration between the tissue and blood compartments and the rate of perfusion; and Vtb, the tissue/blood volume ratio. The plasma perfusion model has three additional dimensionless parameters: f, the fraction of plasma withdrawn from the blood in a plasma separator; alpha, the ratio of the plasma perfusion rate in the bioreactor to the blood draw rate; and Vbr, the blood/plasma reservoir volume ratio. Within the physiologic range of parameters, the rate of reduction in blood concentration in both the whole blood-perfused and plasma-perfused systems are sensitive to Damkohler number up to Da approximately 2. Neither system is sensitive to variations in kappa, and the plasma perfusion system has little sensitivity to alpha. Given bioreactors of equivalent activity, a greater rate of blood concentration reduction and lower endpoint blood concentration at equivalent perfusion times will be achieved with whole blood perfusion. There are two physical reasons for this. The first is that the plasma perfused system is only processing a fraction, f, of the blood compared with the whole blood perfusion system. The second reason is that, although the blood-perfused system is limited by overall bioreactor performance, the plasma-perfused system is mass transfer limited to the rate of blood concentration dilution into the plasma reservoir rather than limited by the overall bioreactor performance.

Development of an in vivo ischemia-reperfusion model in heterotopically transplanted rat hearts.

Heart transplantation has been extensively used in animal models, including studies on gene therapy for myocardial preservation. We investigated the feasibility of in situ left coronary artery (LCA) ligation as a physiological system for the examination of strategies to modulate myocardial tolerance against ischemia-reperfusion injury, such as gene therapy, using heterotopically transplanted rat hearts. Lewis rat hearts that had been transplanted into syngeneic recipients' abdomens were subjected to 30-min ischemia, by occluding the LCA, and subsequent blood reperfusion by releasing the suture in situ (I/R group). Transplanted hearts in the sham group underwent laparotomy only. At 24 hr of reperfusion, the size of the ischemic region was 40.1+/-3.1% of the total left ventricular mass, and the infarct size was 47.5+/-3.3% of the area at risk in the I/R group. Cardiac function was reduced in the I/R group compared with the sham group, associated with higher myeloperoxidase activity (5.12+/-1.35 vs. 0.97+/-0.33 U/g wt) and higher incidence of apoptosis as defined by TUNEL (29.8+/-3.2 vs. 3.8+/-0.7%) and DNA ladder. In the I/R group, up-regulation of Bax, Bak, and caspase-3 was observed. These data on myocardial damage of transplanted hearts are consistent and equivalent to those of the usual LCA occlusion model, suggesting that this method is useful to investigate strategies for modulating myocardial tolerance against ischemia-reperfusion injury using heterotopically transplanted rat hearts in a more physiological blood-perfused model.

The mechanism of ventricular arrhythmia on a canine isolated blood-perfused Brugada syndrome model

The mechanism of ventricular arrhythmia on a canine isolated blood-perfused Brugada syndrome model

QUICK NUMERICAL ASSESSMENT OF SKIN BURN INJURY WITH SPREADSHEET IN PC

This paper presents a blood-perfused skin model as implemented in a spreadsheet software application for accessing burn injuries resulting from exposure of skin surface to flowing hot fluids or constant heat sources. Finite-difference analysis of heat transfer in skin burns provides an accurate prediction of tissue time–temperature relationships throughout the duration of thermal insult. The Henriques theory of skin burns is used for determining the spatial and temporal extent of tissue damage. The epidermis, dermis, and subcutaneous fat were modeled as uniform elements with distinct thermal properties. Method for implementing finite-difference solution in spreadsheet software has been described. A comparison of the injury threshold computed by this model against Henriques's result has been done and the results are in good agreement.

Acute versus subacute haemorrhagic shock evaluated in an isolated perfused rat lung model

Volume resuscitation of haemorrhagic shock (HS) may lead to delayed apparition of shock lung. We compared acute versus subacute grade IV HS with and without volume resuscitation in an isolated blood-perfused and ventilated lung rat model.