Fluorometric study for the noninvasive determination of cellular viability in perfused rat liver

Flow Cytometry Sorting Protocol of Bacillus Spore Using Ultraviolet Laser and Autofluorescence as Main Sorting Criterion

The ultraviolet (UV) Fluorescent Aerodynamic Particle Sizer (FLAPS), a flow cytometer-like apparatus was developed by the Canadian Department of National Defence for real-time detection of autofluorescence of biological aerosol particles such as bacterial spores. The direct relation between autofluorescence intensity and viability has recently been reported and viable spore are more autofluorescent in UV (Laflamme, Frontiers in Bioscience). The goal of this manuscript is to describe a flow cytometry sorting protocol based on UV-induced autofluorescence. An EPICS ELITE ESP flow cytometer equipped with a UV laser and cell sorter was used to mimic the optical properties of FLAPS and to study the two extremes of a spore population according to its autofluorescence (lower level of autofluorescence (LLA) and higher level of autofluorescence (HLA) spores). Bacillus subtilis var niger was used as a surrogate for Bacillus anthracis spores and sorted using autofluorescence intensity as the main criterion. The protocol developed in our laboratory to sort Bacillus spores according to their autofluorescence properties is described. Purity of each sorted population was greater than 95%. Using autofluorescence as the main criterion, we demonstrate that it is possible to separate two distinct spore populations.

Spectroscopic imaging for detection of ischemic injury in rat kidneys by use of changes in intrinsic optical properties

It is currently impossible to consistently predict kidney graft viability and function before and after transplantation. We explored optical spectroscopy to assess the degree of ischemic damage in kidney tissue. Tunable UV laser excitation was used to record autofluorescence images, at different spectral ranges, of injured and contralateral control rat kidneys to reveal the excitation conditions that offered optimal contrast. Autofluorescence and near-infrared cross-polarized light-scattering imaging were both used to monitor changes in intensity and spectral characteristics, as a function of exposure time to ischemic injury. These two modalities provided different temporal behaviors, arguably arising from two different mechanisms providing direct correlation of intrinsic optical signatures to ischemic injury time.

Pretransplantation assessment of renal viability with NADH fluorimetry

BACKGROUND

A pathophysiologic feature possibly involved in ischemic injury in transplant kidneys is mitochondrial dysfunction caused by disintegration of oxidative metabolic pathways. Because the ability to synthesize ATP by respiratory activity determines the organ's capacity to recover from ischemic injury, an assessment of respiratory activity may provide information related to graft viability.

METHODS

NADH fluorimetry can be used to monitor kidney cortex metabolism noninvasively. During perfusion with (an)-aerobic perfusate, NADH fluorescence images were recorded. We evaluated the NADH oxidation kinetics of 20 rat kidneys, which were divided over four experimental groups. For six minimally damaged kidneys and six kidneys that had been stored for one hour at 37 degrees C, perfusion was followed by transplantation. We related the kinetic parameters of these kidneys with their post-transplantation function and histology. The transplant function was monitored by serum creatinine and urea levels.

RESULTS

Storage of transplant kidneys for one hour at 37 degrees C significantly reduced the post-transplantation function. Isolated perfusion of grafts, however, was not detrimental for renal function. The rate of NADH oxidation decreased with decreasing graft quality, and a good correlation between NADH oxidation kinetics and post-transplantation function was found.

CONCLUSIONS

A reduction of NADH oxidation rates as a consequence of warm ischemia supports the view that mitochondrial respiratory activity is impaired by ischemic injury. The correlation between NADH oxidation kinetics in perfused grafts and their post-transplantation function indicates that NADH fluorimetry may be useful in predicting the viability of preserved grafts prior to transplantation.

Real time monitoring of rat liver energy state during ischemia

Hepatic failure is one of the major problems developed during the posttransplantation period. A possible cause of hepatic failure is the prolonged ischemia induced during the implantation procedure. Hepatic ischemia leads to a reduction in oxygen supply, ATP level decline, liver metabolism impairment, and finally organ failure. The purpose of this study was to estimate the functional state of the liver by monitoring liver blood flow and the mitochondrial NADH redox state simultaneously and continuously during in situ liver ischemia followed by reperfusion. Measurements were performed using the multiprobe developed in our laboratory consisting of fibers for the measurement of relative liver blood flow (laser Doppler flowmetry) and mitochondrial redox state (NADH fluorescence). The experimental procedure included the temporary interruption of blood flow to the liver using three types of ischemia, hepatic artery occlusion, portal vein occlusion, and simultaneous occlusion of hepatic artery and portal vein, followed by a reperfusion period. These preliminary experiments showed a significant decrease in liver blood flow, following the three types of liver ischemia, and a significant increase in NADH levels. The probe used in this study incorporates the advantage of monitoring NADH and liver blood flow simultaneously and continuously from the same area on the surface of the liver. Since each of these two parameters is not calibrated in absolute units, the simultaneous monitoring decreases possible artifacts. Also, it will allow us to determine of the coupling between tissue blood flow and oxidative phosphorylation. It is believed that the measurements of respiratory chain dysfunction might predict organ viability in clinical organ transplantation situations. Using this probe may also help to decrease the variability in liver blood flow monitoring since liver blood flow monitoring is supported simultaneously with the mitochondrial redox state, which supplies the information on liver metabolic and functional state.

Microscopic analysis of NADH fluorescence during aerobic and anaerobic liver preservation conditions: A noninvasive technique for assessment of hepatic metabolism

Gaseous insufflation of oxygen via the venous vascular system is thought to be an useful tool for preventing anoxic tissue injury during extended time periods of ischemic preservation and for allowing for an improved recovery of organ function after transplantation. The present study aimed at the application of a noninvasive technique for monitoring effectiveness and homogeneity of gaseous areation by using an epiillumination microscopic technique for assessment of tissue nicotinamide adenine dinucleotide (NADH) fluorescence. Rat livers were flushed with and stored in University of Wisconsin solution at 4 degrees C for 48 h (n = 20). In half of the experiments (n = 10) gaseous oxygen was applied subsequent to organ harvest. Using ultraviolet-excitation high-resolution microscopy and computer-assisted image analysis liver surfaces were scanned for NADH intensity and spatial heterogeneity at 1, 24, and 48 h preservation time. Livers simply stored without aeration served as controls (n = 10). NADH intensity data were compared with corresponding data of tissue adenosine triphosphate (ATP) concentrations determined enzymatically. NADH fluorescence already differed at 1 h preservation between the two groups with significantly lower values in the aerobically stored livers. NADH fluorescence further decreased between 1 and 24 h preservation and remained low until 48 h, whereas in the anaerobically stored livers NADH fluorescence was found to be constantly high over the entire observation period. Aerobic storage resulted in rather homogeneous tissue oxygenation with an intrahepatic variation of NADH fluorescence <20%. In parallel, oxygen persufflation appropriately restored tissue ATP content within 1 to 24 h of preservation, while the simply stored livers exhibited pronounced depletion of ATP. We demonstrate for the first time that by means of retrograde gaseous oxygenation, ischemic livers can be readily and effectively oxygenated. Our study further indicates that the noninvasive microscopic analysis of tissue NADH fluorescence may be an useful tool for estimating efficiency of strategies in organ preservation.

Measurements of tissue viability in transplantation

Near-infrared spectroscopy has primarily been used in monitoring changes in cerebral haemoglobin oxygenation and haemodynamics. However its use as a method for the assessment of tissue viability following transplantation has recently been explored experimentally in our laboratory. The ability to measure changes in oxygenation and perfusion during harvesting and following transplantation of organs or transfer of free and pedicled flaps potentially important in reconstructive surgery. We have found that near-infrared spectroscopy is extremely useful in detecting vaso-occlusive events and can accurately and reliably distinguish between arterial, venous or total occlusions. Venous congestion indicated by raised levels of deoxygenated haemoglobin with a concomitant increase in blood volume and the presence and magnitude of reactive hyperaemia are both easily recognizable features by near-infrared spectroscopy. We have shown that near-infrared spectroscopy measurements of venous congestion in kidneys (and other tissues) following prolonged storage correlate with medullary vascular congestion confirmed by angiographical and histological analysis of intrarenal perfusion. Clinically we have shown that flap perfusion can be improved by altering fluid replacement regimes and the addition of ionotropes. Cerebral near-infrared spectroscopy measurements in a liver transplant model showed statistically significant differences within minutes after the anhepatic phase in cerebral perfusion and oxygenation, between animals transplanted with ischaemically damaged livers compared to those isografted with minimally stored livers. Similarly we have found that near-infrared spectroscopy can be used as a monitor to assess the adequacy of fluid or blood replacement in haemorrhagic and hypovolaemic models. We believe that near-infrared spectroscopy provides a sensitive and reliable postoperative method for the assessment of tissue viability following the transfer of free and pedicled flaps and organs.

Non-invasive measurement of respiratory chain dysfunction following hypothermic renal storage and transplantation

Ischemia/reperfusion (IR) damage is a major cause of dysfunction in transplanted organs. The objective of the present study was to correlate in vivo measurements of respiratory chain (RC) function with histological and physiological parameters. Non-invasive in situ (surface fluorescence) measurements of mitochondrial NADH and near infrared spectroscopic measurements of cyt aa3 were made in unstored (Group 1) and 72 hour stored (1 to 2 degrees C) (Group 2) autografted rabbit kidneys. The effect of sodium pentobarbitone on NADH levels was investigated. In Group 1, there was a significant change in the redox state of cyt aa3 in all (N = 6) kidneys on reperfusion which correlated with organ viability and increased NADH oxidation and minimal edema on histological examination. In Group 2 there was no significant change in cyt aa3 compared to baseline, and this correlated with poor long term organ viability, slower NADH oxidation, and severe cortical edema. Pentobarbitone inhibition of the RC resulted in rapid and complete reduction of NAD+ in Group 1, but none or only a slight reduction in Group 2. The results demonstrate that it might be possible in future to predict organ viability and histological changes by non-invasive measurements of RC dysfunction in the clinical transplant situation.

Rapid fluorometric assay for mitochondrial proton adenosine triphosphatase activity for assessment of viability of liver graft tissue

We developed an improved determination method of mitochondrial proton adenosine triphosphatase (ATPase) activity in the liver. The activity was measured fluorometrically with a 3,3'-dipropylthiodicarbocyanine iodide (diS-C3(5)), which is excited at 625 nm and emits fluorescence at 670 nm. This dye transmits the electric potential across the inner mitochondrial membrane. The fluorescence intensity of diS-C3(5) with mitochondria (100 microliters, 4-16 mg/ml protein) in a 2 ml potassium buffer (pH 7.4) was regarded as a standard electric potential. After confirming the activity of the mitochondrial electron transport chain by succinic acid (9 mumol), we inhibited the chain by antimycin A (1.25 micrograms). Fluorescence intensity decreased by adenosine 5'-triphosphate (ATP) (2 mumol) and oligomycin (25 micrograms) inhibited this depression. The value of mitochondrial proton ATPase activity was calculated as a percentage of the fluorescence intensity change by ATP per the standard electric potential. The activity of mitochondrial proton ATPase in the normal fresh rat livers was 50.3 +/- 2.2%. Good correlation (r2 = 0.807) between two methods for mitochondrial proton ATPase activity, our newly developed method and a conventional colorimetric method, was obtained in the rat livers with various conditions. This method has advantages that the proton ATPase activity can be measured in intact mitochondria, and all procedures can be completed within 40 min. It is suitable for the determination of mitochondrial viability of liver graft in the hepatic resections and transplantations.

Protective effect of a prostaglandin oligomer on liver mitochondria in situ: time-shared measurements of fluorescence and reflectance in the cold-preserved rat liver

The protective effect of a new oligomeric derivative of prostaglandin B2, known as OC-5186, was evaluated using time-sharing spectrofluorometry in the cold-preserved rat liver. Experiments were divided into three groups: in group A, a 5000 ng dose of OC-5186 was administered via the peripheral vein, 1000 ng via the portal vein, and 200 ng/ml in University of Wisconsin (UW) solution; in group B, the OC-5186 dosage was ten times greater than that in group A; in group C (control group), liver procurement and storage were performed without OC-5186. At 0, 12, and 24 h after cold preservation at 4 degrees C, the liver was perfused for 30 min at 12 degrees C with oxygenized Krebs-Henseleit solution, after which the perfusate was switched to deoxygenized Krebs-Henseleit solution. Time sharing spectrofluorometry was used to follow NADH fluorescence at 450 nm with a 360-nm excitation wavelength, as well as the reflectance of cytochrome aa3 with 605 minus 620 nm from oxidation to reduction. Rate constants of NADH fluorescence and cytochrome aa3 reflectance were used as indices of integrity of the mitochondrial respiratory chain. In group C, the rate constant of NADH fluorescence decreased significantly (P < 0.05) from the control value of 8.31 +/- 0.21 x 10(-3) (sec-1) to 4.97 +/- 0.15 x 10(-3) and 5.58 +/- 0.16 x 10(-3) (mean +/- SEM) at 12 and 24 h after cold preservation, respectively.(ABSTRACT TRUNCATED AT 250 WORDS)

Low-temperature fluorometric technique for evaluating the viability of rat liver grafts after simple cold storage

Time-dependent changes in the viability of rat liver graft during cold preservation with Euro-Collins solution were evaluated with NADH fluorometry. Correlation between the fluorometric analysis, 1-week survival rate after liver transplantation, and mitochondrial ATP synthesis activity in the early phase after transplantation was studied. Fluorometric study: Rat livers were preserved at 0 degree-4 degrees C for 0-48 h in Euro-Collins solution and then reperfused for 15 min with oxygenated Krebs-Henseleit solution at 4 degrees C. The amplitude (R x A) between the oxidized and the reduced steady-state NADH fluorometric trace and the velocity (R x V) of the trace were determined to evaluate the mitochondrial respiratory chain. The R x A and R x V remained at levels higher than 90% of control after 6-h preservation, while the R x A of the 9-h preservation group and the R x V of the 12-h preservation group decreased significantly compared with those of the control and the 6-h preservation group. Survival study: a 100% survival rate after transplantation was achieved in the 6-h preservation group, whereas the rates were 18.8% and 0% in the 9- and 12-h preservation groups respectively. These survival rates correlated closely with the time-dependent decrease of the fluorometric parameters. Study of mitochondrial phosphorylative activity and energy charge 3 h after transplantation: With fresh grafts, the decrease in hepatic energy charge after transplantation was reduced to 0.79 from the control value of 0.86 by a 30% increase in mitochondrial ATP synthesis ability.(ABSTRACT TRUNCATED AT 250 WORDS)

The role of enhanced mitochondrial phosphorylation in rat liver transplantation

The effects of organ preservation on mitochondrial oxidative phosphorylation activity, adenylate hepatic energy charge, cytochrome content, and redox state of NAD+/NADH couple in rat liver transplantation were compared between a nonpreservation group and a preservation group with grafts preserved for 12 hr in Euro-Collin's solution. At 3 hr after transplantation, the energy charge in the preservation group decreased to 0.60 +/- 0.02 from the control value of 0.86 +/- 0.01, accompanied by a reduction of intramitochondrial redox state of NAD+/NADH couple. In contrast, in the nonpreservation group, the decrease in energy charge was minimally decreased to 0.79 +/- 0.04 due to the compensatory enhancement of mitochondrial oxidative phosphorylation activity. These results suggest that an enhanced mitochondrial ATP synthesis and a reduced intramitochondrial redox state are important factors affecting survival following rat liver transplantation.

Changes in blood ketone body ratio with reference to graft viability after liver transplantation in rats

Arterial blood ketone body ratio (acetoacetate/3-hydroxybutyrate; KBR), which reflects hepatic mitochondrial redox potential, was measured during a 2-week period after orthotopic liver transplantation in three groups of rats: group 1, the isogenic combination of LEW (RT1l) graft to LEW recipient as control; group 2, the allogenic combination of ACI (RT1a) graft to LEW recipient without immunosuppressive treatment: and group 3, the allogenic combination of ACI to LEW with immunosuppressive treatment using cyclosoporin (CyA). Isogenic recipients survived indefinitely. Allogenic recipients in group 2 had severe rejection with a mean survival of 10.3 +/- 0.54 days, while 77.8% of the allogenic recipients in group 3 survived more than 30 days. KBR of rats surviving more than 2 weeks in groups 1 and 3 gradually increased post-transplantation and was maintained at a high level. By contrast, though KBR in group 2 was restored at 3 days, it gradually fell and remained at a significantly low level (P less than 0.001). It is suggested that KBR provides an accurate indicator for evaluating metabolic viability of the critically deteriorating liver graft accompanied by sever rejection.

Ubiquitous formation of catalase compound II in hemoglobin-free perfused rat liver and detection of novel spectral species

Spectral examinations of hemoglobin-free perfused rat livers with a high-sensitivity reflectance spectrophotometer have revealed an accumulation of catalase Compound II to an amount comparable to that of Compound I under the aerobic steady state. This finding is in contrast to a recent proposal that NADPH associated with catalase both prevents and reverses the accumulation of Compound II (Kirkman, H. N., Galiano, S., and Gaetani, G.F. (1987) J. Biol. Chem. 262, 660-666). Furthermore, spectral species with a broad peak extending from 550 to 600 nm were observed in a time range between the methanol-induced decays of Compound I and Compound II. When rats were treated with 3-amino-1,2,4-triazole, catalase Compound I was not detected but spectral species with peaks at 570, 556 and 530 nm were observed. These novel spectral profiles suggest contributions from "peroxy" and "ferryl" forms of cytochrome oxidase.