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PloS One 2023Aqueous humor dynamics are commonly assessed by infusing fluid into the eye and measuring intraocular pressure (IOP). From the pressure-flow relationship, conventional...
Aqueous humor dynamics are commonly assessed by infusing fluid into the eye and measuring intraocular pressure (IOP). From the pressure-flow relationship, conventional outflow facility is estimated to study glaucomatous processes that lower facility or identify therapeutics that enhance facility in hopes of restoring healthy IOP levels. The relative merits and limitations of constant flow (CF), gravity-driven constant pressure (CPg), and pump-driven constant pressure (CPp) infusion techniques were explored via simulations of a lumped parameter viscoelastic model of the eye. Model parameter values were based on published perfusion system properties and outflow facility data from rodents. Step increases in pressure or flow were simulated without and with IOP noise recorded from enucleated eyes, anesthetized animals, and conscious animals. Steady-state response levels were determined using published window and ratio criteria. Model simulations show that all perfusion techniques estimate facility accurately and that ocular fluid dynamics set a hard limit on how fast measurements can be taken. This limit can be approached with CPg and CPp systems by increasing their gain but not with CF systems, which invariably take longest to settle. Facility experiment duration is further lengthened by inclusion of IOP noise, and data filtering is needed for steady-state detection with in vivo noise. The ratio criterion was particularly affected because noise in the flow data is amplified by the higher gain of CPg and CPp systems. A recursive regression method is introduced, which can ignore large transient IOP fluctuations that interfere with steady-state detection by fitting incoming data to the viscoelastic eye model. The fitting method greatly speeds up data collection without loss of accuracy, which could enable outflow facility measurements in conscious animals. The model may be generalized to study response dynamics to fluid infusion in other viscoelastic compartments of the body and model insights extended to optimize experiment design.
Topics: Animals; Intraocular Pressure; Glaucoma; Tonometry, Ocular; Aqueous Humor; Perfusion
PubMed: 37988400
DOI: 10.1371/journal.pone.0294607 -
Transplant International : Official... Jun 2015Hypothermic machine perfusion (HMP) of kidneys is a long-established alternative to static cold storage and has been suggested to be a better preservation method. Today,... (Review)
Review
Hypothermic machine perfusion (HMP) of kidneys is a long-established alternative to static cold storage and has been suggested to be a better preservation method. Today, as our deceased donor profile continues to change towards higher-risk kidneys of lower quality, we are confronted with the limits of cold storage. Interest in HMP as a preservation technique is on the rise. Furthermore, HMP also creates a window of opportunity during which to assess the viability and quality of the graft before transplantation. The technology might also provide a platform during which the graft could be actively repaired, making it particularly attractive for higher-risk kidneys. We review the current evidence on HMP in kidney transplantation and provide an outlook for the use of the technology in the years to come.
Topics: Cold Temperature; Donor Selection; Drug Delivery Systems; Genetic Therapy; Graft Survival; Humans; Kidney Transplantation; Organ Preservation; Organ Preservation Solutions; Oxygen; Perfusion; Randomized Controlled Trials as Topic; Stem Cell Transplantation; Tissue Donors; Treatment Outcome
PubMed: 25630347
DOI: 10.1111/tri.12530 -
Kidney International Aug 2021Normothermic machine perfusion (NMP) is emerging as a novel preservation strategy. During NMP, the organ is maintained in a metabolically active state that may not only... (Review)
Review
Normothermic machine perfusion (NMP) is emerging as a novel preservation strategy. During NMP, the organ is maintained in a metabolically active state that may not only provide superior organ preservation, but that also facilitates viability testing before transplantation, and ex situ resuscitation of marginal kidney grafts. Although the prevailing perfusion protocols for renal NMP are refined from initial pioneering studies concerning short periods of NMP, it could be argued that these protocols are not optimally tailored to address the putatively compromised metabolic plasticity of marginal donor grafts (i.e., in the context of viability testing and/or preservation), or to meet the metabolic prerequisites associated with prolonged perfusions and the required anabolic state in the context of organ regeneration. Herein, we provide a theoretical framework for the metabolic requirements for renal NMP. Aspects are discussed along the lines of carbohydrates, fatty acids, amino acids, and micronutrients required for optimal NMP of an isolated kidney. In addition, considerations for monitoring aspects of metabolic status during NMP are discussed.
Topics: Kidney; Kidney Transplantation; Organ Preservation; Perfusion
PubMed: 33857572
DOI: 10.1016/j.kint.2021.04.001 -
Transplantation Jun 2023Deceased donor livers are prone to biliary complications, which may necessitate retransplantation, and we, and others, have suggested that these complications are...
D-dimer Release From Livers During Ex Situ Normothermic Perfusion and After In Situ Normothermic Regional Perfusion: Evidence for Occult Fibrin Burden Associated With Adverse Transplant Outcomes and Cholangiopathy.
BACKGROUND
Deceased donor livers are prone to biliary complications, which may necessitate retransplantation, and we, and others, have suggested that these complications are because of peribiliary vascular fibrin microthrombi. We sought to determine the prevalence and consequence of occult fibrin within deceased donor livers undergoing normothermic ex situ perfusion (NESLiP) and evaluate a role for fibrinolysis.
METHODS
D-dimer concentrations, products of fibrin degradation, were assayed in the perfusate of 163 livers taken after 2 h of NESLiP, including 91 that were transplanted. These were related to posttransplant outcomes. Five different fibrinolytic protocols during NESLiP using alteplase were evaluated, and the transplant outcomes of these alteplase-treated livers were reviewed.
RESULTS
Perfusate D-dimer concentrations were lowest in livers recovered using in situ normothermic regional perfusion and highest in alteplase-treated livers. D-dimer release from donation after brain death livers was significantly correlated with the duration of cold ischemia. In non-alteplase-treated livers, Cox proportional hazards regression analysis showed that D-dimer levels were associated with transplant survival ( P = 0.005). Treatment with alteplase and fresh frozen plasma during NESLiP was associated with significantly more D-dimer release into the perfusate and was not associated with excess bleeding postimplantation; 8 of the 9 treated livers were free of cholangiopathy, whereas the ninth had a proximal duct stricture.
CONCLUSIONS
Fibrin is present in many livers during cold storage and is associated with poor posttransplant outcomes. The amount of D-dimer released after fibrinolytic treatment indicates a significant occult fibrin burden and suggests that fibrinolytic therapy during NESLiP may be a promising therapeutic intervention.
Topics: Humans; Liver Transplantation; Fibrin; Organ Preservation; Liver; Perfusion
PubMed: 36728501
DOI: 10.1097/TP.0000000000004475 -
Transplant International : Official... 2023Considering recent clinical and experimental evidence, expectations for using DCD-derived intestines have increased considerably. However, more knowledge about DCD...
Considering recent clinical and experimental evidence, expectations for using DCD-derived intestines have increased considerably. However, more knowledge about DCD procedure and long-term results after intestinal transplantation (ITx) is needed. We aimed to describe in detail a DCD procedure for ITx using normothermic regional perfusion (NRP) in a preclinical model. Small bowel was obtained from pigs donors after 1 h of NRP and transplanted to the recipients. Graft Intestinal samples were obtained during the procedure and after transplantation. Ischemia-reperfusion injury (Park-Chiu score), graft rejection and transplanted intestines absorptive function were evaluated. Seven of 8 DCD procedures with NRP and ITx were successful (87.5%), with a good graft reperfusion and an excellent recovery of the recipient. The architecture of grafts was well conserved during NRP. After an initial damage of Park-chiu score of 4, all grafts recovered from ischemia-reperfusion, with no or very subtle alterations 2 days after ITx. Most recipients (71.5%) did not show signs of rejection. Only two cases demonstrated histologic signs of mild rejection 7 days after ITx. Interestingly intestinal grafts showed good absorptive capacity. The study's results support the viability of intestinal grafts from DCD using NRP, contributing more evidence for the use of DCD for ITx.
Topics: Animals; Swine; Humans; Perfusion; Reperfusion; Tissue Donors; Graft Rejection; Reperfusion Injury
PubMed: 37745640
DOI: 10.3389/ti.2023.11518 -
Multimedia Manual of Cardiothoracic... Mar 2021Ex vivo lung perfusion is an indispensable tool in the armamentarium of any lung transplant center. It helps to increase an already shrinking donor pool by offering a...
Ex vivo lung perfusion is an indispensable tool in the armamentarium of any lung transplant center. It helps to increase an already shrinking donor pool by offering a chance to assess suboptimal donor lungs in a systematic manner and improve them by treating them with low-molecular-weight perfusate. We offer a stepwise guide to carry out ex vivo lung perfusion on the donor lungs and criteria to accept them for transplants.
Topics: Donor Selection; Extracorporeal Circulation; Humans; Lung; Lung Transplantation; Male; Middle Aged; Organ Preservation; Perfusion; Tissue Donors
PubMed: 33904268
DOI: 10.1510/mmcts.2021.018 -
Methods (San Diego, Calif.) Aug 2015Adipose tissue engineered models are needed to enhance our understanding of disease mechanisms and for soft tissue regenerative strategies. Perfusion systems generate...
Adipose tissue engineered models are needed to enhance our understanding of disease mechanisms and for soft tissue regenerative strategies. Perfusion systems generate more physiologically relevant and sustainable adipose tissue models, however adipocytes have unique properties that make culturing them in a perfusion environment challenging. In this paper we describe the methods involved in the development of two perfusion culture systems (2D and 3D) to test their applicability for long term in vitro adipogenic cultures. It was hypothesized that a silk protein biomaterial scaffold would provide a 3D framework, in combination with perfusion flow, to generate a more physiologically relevant sustainable adipose tissue engineered model than 2D cell culture. Consistent with other studies evaluating 2D and 3D culture systems for adipogenesis we found that both systems successfully model adipogenesis, however 3D culture systems were more robust, providing the mechanical structure required to contain the large, fragile adipocytes that were lost in 2D perfused culture systems. 3D perfusion also stimulated greater lipogenesis and lipolysis and resulted in decreased secretion of LDH compared to 2D perfusion. Regardless of culture configuration (2D or 3D) greater glycerol was secreted with the increased nutritional supply provided by perfusion of fresh media. These results are promising for adipose tissue engineering applications including long term cultures for studying disease mechanisms and regenerative approaches, where both acute (days to weeks) and chronic (weeks to months) cultivation are critical for useful insight.
Topics: Adipocytes; Adipogenesis; Adult Stem Cells; Animals; Biocompatible Materials; Cell Culture Techniques; Humans; Materials Testing; Perfusion; Silk; Tissue Engineering; Tissue Scaffolds
PubMed: 25843606
DOI: 10.1016/j.ymeth.2015.03.022 -
BMC Surgery Aug 2023Real-time quantification of tissue perfusion can improve intraoperative surgical decision making. Here we demonstrate the utility of Laser Speckle Contrast Imaging as an...
BACKGROUND/PURPOSE
Real-time quantification of tissue perfusion can improve intraoperative surgical decision making. Here we demonstrate the utility of Laser Speckle Contrast Imaging as an intra-operative tool that quantifies real-time regional differences in intestinal perfusion and distinguishes ischemic changes resulting from arterial/venous obstruction.
METHODS
Porcine models (n = 3) consisted of selectively devascularized small bowel loops that were used to measure the perfusion responses under conditions of control/no vascular occlusion, arterial inflow occlusion, and venous outflow occlusion using laser speckle imaging and indocyanine green fluoroscopy. Laser Speckle was also used to assess perfusion differences between small bowel antimesenteric-antimesenteric and mesenteric-mesenteric anastomoses. Perfusion quantification was measured in relative perfusion units calculated from the laser speckle perfusion heatmap.
RESULTS
Laser Speckle distinguished between visually identified perfused, watershed, and ischemic intestinal segments with both color heatmap and quantification (p < .00001). It detected a continuous gradient of relative intestinal perfusion as a function of distance from the stapled ischemic bowel edge. Strong positive linear correlation between relative perfusion units and changes in mean arterial pressure resulting from both arterial (R = .96/.79) and venous pressure changes (R = .86/.96) was observed. Furthermore, Laser Speckle showed that the antimesenteric anastomosis had a higher perfusion than mesenteric anastomosis (p < 0.01).
CONCLUSIONS
Laser Speckle Contrast Imaging provides objective, quantifiable tissue perfusion information in both color heatmap and relative numerical units. Laser Speckle can detect spatial/temporal differences in perfusion between antimesenteric and mesenteric borders of a bowel segment and precisely detect perfusion changes induced by progressive arterial/venous occlusions in real-time.
Topics: Swine; Animals; Laser Speckle Contrast Imaging; Perfusion; Intestines; Laparoscopy; Arteries; Vascular Diseases
PubMed: 37649010
DOI: 10.1186/s12893-023-02161-w -
Transplant International : Official... 2022normothermic perfusion (EVNP) is an emerging strategy in kidney preservation that enables resuscitation and viability assessment under pseudo-physiological conditions... (Review)
Review
normothermic perfusion (EVNP) is an emerging strategy in kidney preservation that enables resuscitation and viability assessment under pseudo-physiological conditions prior to transplantation. The optimal perfusate composition and duration, however, remain undefined. A systematic literature search (Embase; Medline; Scopus; and BIOSIS Previews) was conducted. We identified 1,811 unique articles dating from January 1956 to July 2021, from which 24 studies were deemed eligible for qualitative analysis. The perfusate commonly used in clinical practice consisted of leukocyte-depleted, packed red blood cells suspended in Ringer's lactate solution with Mannitol, dexamethasone, heparin, sodium bicarbonate and a specific nutrient solution supplemented with insulin, glucose, multivitamins and vasodilators. There is increasing support in preclinical studies for non-blood cell-based perfusates, including Steen solution, synthetic haem-based oxygen carriers and acellular perfusates with supraphysiological carbogen mixtures that support adequate oxygenation whilst also enabling gradual rewarming. Extended durations of perfusion (up to 24 h) were also feasible in animal models. Direct comparison between studies was not possible due to study heterogeneity. Current evidence demonstrates safety with the aforementioned widely used protocol, however, extracellular base solutions with adequate oxygenation, supplemented with nutrient and metabolic substrates, show promise by providing a suitable environment for prolonged preservation and resuscitation. https://www.crd.york.ac.uk/prospero/display_record.php?ID=CRD42021231381, identifier PROSPERO 2021 CRD42021231381.
Topics: Animals; Extracorporeal Circulation; Humans; Kidney; Kidney Transplantation; Organ Preservation; Perfusion
PubMed: 35634582
DOI: 10.3389/ti.2022.10236 -
Journal of Cellular and Molecular... Dec 2020With the rapid development of single-cell sequencing technology, the Langendorff perfusion system has emerged as a common approach to decompose cardiac tissue and obtain...
With the rapid development of single-cell sequencing technology, the Langendorff perfusion system has emerged as a common approach to decompose cardiac tissue and obtain living cardiomyocytes to study cardiovascular disease with the mechanism of cardiomyocyte biology. However, the traditional Langendorff perfusion system is difficult to master, and further, the viability and purity of cardiomyocytes are frequently unable to meet sequencing requirements due to complicated devices and manipulate processes. Here, we provide an optimized Langendorff perfusion system with a simplified and standardized operating protocol which utilizes gravity as the perfusion pressure, includes a novel method for bubbles removing and standardizes the criteria for termination of digestion. We obtained stable cardiomyocyte with high viability and purity after multiple natural gravity sedimentation. The combination of the optimized Langendorff perfusion system and the multiple natural gravity sedimentation provides a stable system for isolating adult mouse heart, which will provide higher-quality cardiomyocytes for further experiments.
Topics: Animals; Biomarkers; Cell Separation; Flow Cytometry; Immunophenotyping; Mice; Myocytes, Cardiac; Perfusion
PubMed: 33147379
DOI: 10.1111/jcmm.15773