Concurrent Assessment of Deformability and Adhesiveness of Sickle Red Blood Cells by Measuring Perfusion of an Adhesive Artificial Microvascular Network

Biomarker development is a key clinical research need in sickle cell disease (SCD). Hemorheological parameters are excellent candidates as abnormal red blood cell (RBC) rheology plays a critical role in SCD pathophysiology. Here we describe a microfluidic device capable of evaluating RBC deformability and adhesiveness concurrently, by measuring their effect on perfusion of an artificial microvascular network (AMVN) that combines microchannels small enough to require RBC deformation, and laminin (LN) coating on channel walls to model intravascular adhesion. Each AMVN device consists of three identical capillary networks, which can be coated with LN (adhesive) or left uncoated (non-adhesive) independently. The perfusion rate for sickle RBCs in the LN-coated networks (0.18 ± 0.02 nL/s) was significantly slower than in non-adhesive networks (0.20 ± 0.02 nL/s), and both were significantly slower than the perfusion rate for normal RBCs in the LN-coated networks (0.22 ± 0.01 nL/s). Importantly, there was no overlap between the ranges of perfusion rates obtained for sickle and normal RBC samples in the LN-coated networks. Interestingly, treatment with poloxamer 188 decreased the perfusion rate for sickle RBCs in LN-coated networks in a dose-dependent manner, contrary to previous studies with conventional assays, but in agreement with the latest clinical trial which showed no clinical benefit. Overall, these findings suggest the potential utility of the adhesive AMVN device for evaluating the effect of novel curative and palliative therapies on the hemorheological status of SCD patients during clinical trials and in post-market clinical practice.

Numerical study on the effects of blood perfusion and tumor metabolism on tumor temperature for targeted hyperthermia considering a realistic geometrical model of head layers using the finite element method

The main aim of the present work is to determine the temperature distribution in the normal and cancerous tissues to achieve the desired condition of hyperthermia. Hyperthermia can be defined as the mild elevation of the temperature to 40–46 °C, which induces the cancer cell death and enhances the effects of the radiotherapy and chemotherapy. In the present research, the realistic geometry of the human head layers and the tumor are modelled, geometrically, and then simulated similar to the real samples of MRI images with the size of 5990 mm3. The temperature distribution in the tumor and healthy tissues was obtained based on the solution of Penne’s bio-heat transfer equation utilizing the Finite Element scheme. Employing the accurate boundary conditions for the thermal simulation of the problem, two main layers of the human brain, namely, white matter (WM) and gray matter (GM), as well as the cerebrospinal fluid (CSF) and the skull, are considered in the thermal analysis. In order to examine the hyperthermia conditions, the effects of the different blood perfusion rates and tumor metabolism on the tumor temperature are analyzed. The results showed that by reducing the blood perfusion rate from 0.0016 to 0.0005(ml/(ml.s)), the temperature increased by nearly 0.2 ℃ at the center of the tumor implying that the variations of the blood perfusion rate in the tumor have not a significant influence on its temperature. Moreover, it was found that when the tumor metabolism increases five times (equal to 125 × 103 W/m3) than its normal value (equal to 25,000 W/m3), the temperature reaches to the range needed for ablation of the brain tumor (40–46 ℃). The results also indicated that the manipulation of the cancer tissues metabolic rate via thermal simulation could be efficiently employed to estimate the amount of heat needed for the thermal ablation of the tumor.

Analysis of hyperbolic Pennes bioheat equation in perfused homogeneous biological tissue subject to the instantaneous moving heat source

The one-dimensional hyperbolic Pennes bioheat equation under instantaneous moving heat source is solved analytically based on the Eigenvalue method. Comparison with results of in vivo experiments performed earlier by other authors shows the excellent prediction of the presented closed-form solution. We present three examples for calculating the Arrhenius equation to predict the tissue thermal damage analysis with our solution, i.e., characteristics of skin, liver, and kidney are modeled by using their thermophysical properties. Furthermore, the effects of moving velocity and perfusion rate on temperature profiles and thermal tissue damage are investigated. Results illustrate that the perfusion rate plays the cooling role in the heating source moving path. Also, increasing the moving velocity leads to a decrease in absorbed heat and temperature profiles. The closed-form analytical solution could be applied to verify the numerical heating model and optimize surgery planning parameters.

Modeling changes in vascular and extracellular matrix integrity that can occur in decellularized kidneys after implantation

A method was established to identify alterations in vascular patency and extracellular matrix integrity of decellularized porcine kidney scaffolds. These scaffolds were perfused with blood at physiologically normal (500 and 650 ml/min) and abnormal (200 ml/min) rates. Variations in venous outflow were then assessed over 24 hours. Angiographic data confirmed that standard arterial branching patterns and the integrity of the extracellular matrix were considerably disrupted. Scaffolds subjected to normal arterial perfusion rates observed drops in venous outflow across the 24 hours. These reductions rose from roughly 40% after 12 hours to 60% after 24 hours. At the end of the test period, regardless of the underlying damage that occurred, the kidneys appeared intact on the surface, and there were no apparent signs of clotting. In comparison, venous flow rates decreased by 80 to 100% across the 24 hours in acellular scaffolds subjected to a far lower perfusion rate of 200 ml/min. These kidneys also appeared intact after 24 hours of perfusion, but presented several arterial, venous, and ureteral clots. The results of this study provide insight into circumstances that limit scaffold viability and provide a simplified model to analyze other conditions that can better prepare scaffolds for long-term transplantation.

Computational Modelling of Dual-Phase Lag Bioheat Process in Cooling of Cutaneous Tissue Exposed to High Heating for Burn Injury Prediction

Heat transfer in biological systems is critical in analytic and therapeutic burn applications. Timely burn evaluation and appropriate clinical management are critical to ameliorate the treatment outcome of burn patients. To apply appropriate burn treatment, it is necessary to understand the thermal parameters of the skin. The paper aims to model the non-Fourier bioheat process in the human skin using a multi-domain trivariate spectral collocation method to determine skin burn injury with non-ideal properties of tissue, blood perfusion and metabolism. The skin tissue internal water evaporation during direct heating is considered. Parametric studies on the effects of skin tissue properties, initial temperature, blood perfusion rate and heat transfer parameters for the thermal response and exposure time of triple-layer cutaneous tissues are carried out. The study shows that the initial tissue temperature, the thermal conductivity of the epidermis and dermis, relaxation and thermalisation time and convective heat transfer coefficient are critical parameters necessary for skin burn injury baseline examination. The thermal conductivity and blood perfusion rate also exhibit negligible effects on the burn injury threshold of the cutaneous tissue. The present study is aimed to assist burn evaluation for reliable experimentation, design and optimisation of thermal therapy delivery.

Microfluidic capillary networks are more sensitive than ektacytometry to the decline of red blood cell deformability induced by storage

Ektacytometry has been the primary method for evaluating deformability of red blood cells (RBCs) in both research and clinical settings. This study was designed to test the hypothesis that the flow of RBCs through a network of microfluidic capillaries could provide a more sensitive assessment of the progressive impairment of RBC deformability during hypothermic storage than ektacytometry. RBC units (n = 9) were split in half, with one half stored under standard (normoxic) conditions and the other half stored hypoxically, for up to 6 weeks. RBC deformability was measured weekly using two microfluidic devices, an artificial microvascular network (AMVN) and a multiplexed microcapillary network (MMCN), and two commercially available ektacytometers (RheoScan-D and LORRCA). By week 6, the elongation indexes measured with RheoScan-D and LORRCA decreased by 5.8–7.1% (5.4–6.9% for hypoxic storage). Over the same storage duration, the AMVN perfusion rate declined by 27.5% (24.5% for hypoxic) and the MMCN perfusion rate declined by 49.0% (42.4% for hypoxic). Unlike ektacytometry, both AMVN and MMCN measurements showed statistically significant differences between the two conditions after 1 week of storage. RBC morphology deteriorated continuously with the fraction of irreversibly-damaged (spherical) cells increasing significantly faster for normoxic than for hypoxic storage. Consequently, the number of MMCN capillary plugging events and the time MMCN capillaries spent plugged was consistently lower for hypoxic than for normoxic storage. These data suggest that capillary networks are significantly more sensitive to both the overall storage-induced decline of RBC deformability, and to the differences between the two storage conditions, than ektacytometry.

Tissue-Engineered Anterior Segment Eye Cultures Maintain Intraocular Pressure within a Normal Range

Glaucoma is a blinding disease largely caused by increased resistance to drainage of fluid from the eye’s anterior chamber, resulting in elevated intraocular pressure (IOP). A major site of fluid outflow regulation and pathology is the trabecular meshwork (TM) at the entrance of the eye’s drainage system. We aimed to characterize the structural and functional properties of a newly developed tissue-engineered anterior segment eye culture model. We hypothesized that repopulation of a decellularized TM with non-native TM cells could restore aspects of normal TM. The decellularization protocol removed all cells and debris while preserving the ECM. Seeded cells localized to the TM region and progressively infiltrated the meshwork ECM. Cells reached a distribution comparable to control TM after four days of perfusion culture. After a perfusion rate increase challenge, tissue-engineered cultures reestablished normal IOPs (reseeded = 13.7±0.4 mmHg, decellularized = 35.2±2.2 mmHg, p < 0.0001). eGFP expressing CrFK control cells caused a high and unstable IOP (27.0±6.2 mmHg). In conclusion, we describe a readily available, storable, and biocompatible scaffold for anterior segment perfusion culture of non-native cells. Tissue-engineered organs demonstrated similarities to native tissues and may reduce the need for scarce donor globes in outflow research.