Different patterns of intestinal response to injury after arterial, venous or arteriovenous occlusion in rats

Real-time quantification of intestinal perfusion and arterial versus venous occlusion using laser speckle contrast imaging in porcine model

PURPOSE

Real-time intraoperative perfusion assessment may reduce anastomotic leaks. Laser speckle contrast imaging (LSCI) provides dye-free visualization of perfusion by capturing coherent laser light scatter from red blood cells and displays perfusion as a colormap. Herein, we report a novel method to precisely quantify intestinal perfusion using LSCI.

METHODS

ActivSight™ is an FDA-cleared multi-modal visualization system that can detect and display perfusion via both indocyanine green imaging (ICG) and LSCI in minimally invasive surgery. An experimental prototype LSCI perfusion quantification algorithm was evaluated in porcine models. Porcine small bowel was selectively devascularized to create regions of perfused/watershed/ischemic bowel, and progressive aortic inflow/portal vein outflow clamping was performed to study arterial vs. venous ischemia. Continuous arterial pressure was monitored via femoral line.

RESULTS

LSCI perfusion colormaps and quantification distinguished between perfused, watershed, and ischemic bowel in all vascular control settings: no vascular occlusion (p < 0.001), aortic occlusion (p < 0.001), and portal venous occlusion (p < 0.001). LSCI quantification demonstrated similar levels of ischemia induced both by states of arterial inflow and venous outflow occlusion. LSCI-quantified perfusion values correlated positively with higher mean arterial pressure and with increasing distance from ischemic bowel.

CONCLUSION

LSCI relative perfusion quantification may provide more objective real-time assessment of intestinal perfusion compared to conventional naked eye assessment by quantifying currently subjective gradients of bowel ischemia and identifying both arterial/venous etiologies of ischemia.

Prediction factors for ischemia of closed-loop small intestinal obstruction

A closed-loop type of intestinal obstruction leads to ischemic necrosis. There have been indicators that may predict ischemia and its severity, such as biomarkers and computed tomography scans. In addition to the usual inflammation markers, such as white blood count-neutrophil count and c-reactive protein (CRP), the most accurate predictors that have been proposed are the CRP-to-albumin ratio, the neutrophil/lymphocyte ratio and the platelet/lymphocyte ratio. Endothelin 1 is another promising biomarker of ischemia that must be assessed in daily clinical practice. Advanced age and frailty status were assessed as predictors of mortality. A timely operative procedure without any delay ensures a better outcome.

Impacts of arterial ischemia or venous occlusion on vascularized groin lymph nodes in a rat model

BACKGROUND

Reported ischemia time of vascularized lymph nodes was 5 hours. This study investigated the effects of arterial ischemia and venous occlusion on vascularized lymph node function in rats.

METHODS

Bilateral pedicled groin lymph node flaps were raised in 27 Lewis rats. Femoral artery and vein were separated and clamped for 1, 3, 4, or 5 hour(s). Lymph node flap perfusion and drainage were assessed by laser Doppler flowmetry and indocyanine green lymphography. Histologic changes were assessed using hematoxylin and eosin stain, terminal deoxynucleotidyl transferase-mediated dUTP nick end-labeling (TUNEL), and glutathione assays.

RESULTS

Perfusion units of 2.84 ± 1.41, 2.46 ± 0.64, 2.42 ± 0.37, and 2.01 ± 0.90 were measured in arterial ischemia groups, and 1.71 ± 0.45, 2.20 ± 0.98, 1.49 ± 0.35, and 0.81 ± 0.20 in venous occlusion groups after 1, 3, 4, and 5 hours of clamping, respectively. Lymphatic drainage showed mean latency periods of 5.33 ± 0.88, 9.00 ± 3.21, 10.00 ± 2.08, and 24.50 ± 11.50 seconds in arterial clamping groups, and 25.00 ± 3.61, 26.00 ± 3.06, 23.33 ± 4.41, and 152.00 ± 0 seconds in venous clamping groups, respectively. Severe medullary and cortical congestion and hemorrhage on histology and cell damage by glutathione levels and TUNEL assay were found after 4 hours of venous clamping.

CONCLUSIONS

Arterial ischemia and venous occlusion impact the function and viability of vascularized lymph node flaps differently. The critical venous occlusion time was 4 hours.

Discrimination between arterial and venous bowel ischemia by computer-assisted analysis of the fluorescent signal

BACKGROUND

Arterial blood supply deficiency and venous congestion both play a role in anastomotic complications. Our aim was to evaluate a software-based analysis of the fluorescence signal to recognize the patterns of bowel ischemia.

METHODS

In 18 pigs, two clips were applied on the inferior mesenteric artery (group A: n = 6) or vein (group V: n = 6) or on both (group A-V: n = 6). Three regions of interest (ROIs) were identified on the sigmoid: P = proximal to the first clip; C = central, between the two clips; and D = distal to the second clip. Indocyanine Green was injected intravenously. The fluorescence signal was captured by means of a near-infrared laparoscope. The time-to-peak (seconds) and the maximum fluorescence intensity were recorded using software. A normalized fluorescence intensity unit (NFIU: 0-to-1) was attributed, using a reference card. The NFIU's over-time variations were computed every 10 min for 50 min. Capillary lactates were measured on the sigmoid at the 3 ROIs. Various machine learning algorithms were applied for ischemia patterns recognition.

RESULTS

The time-to-peak at the ischemic ROI C was significantly longer in group A versus V (20.1 ± 13 vs. 8.43 ± 3.7; p = 0.04) and in group A-V versus V (20.71 ± 11.6 vs. 8.43 ± 3.7; p = 0.03). The maximal NIFU at ROI C, was higher in the V group (1.01 ± 0.21) when compared to A (0.61 ± 0.11; p = 0.002) and A-V (0.41 ± 0.2; p = 0.0005). Capillary lactates at ROI C were lower in V (1.3 ± 0.6) than in A (1.9 ± 0.5; p = 0.0071), and A-V (2.6 ± 1.5; p = 0.034). The K nearest neighbor and the Linear SVM algorithms provided both an accuracy of 75% in discriminating between A versus V and 85% in discriminating A versus A-V. The accuracy dropped to 70% when the ML had to identify the ROI and the type of ischemia simultaneously.

CONCLUSIONS

The computer-assisted dynamic analysis of the fluorescence signal enables the discrimination between different bowel ischemia models.

Pentoxifylline associated to hypertonic saline solution attenuates inflammatory process and apoptosis after intestinal ischemia/reperfusion in rats

PURPOSE

To evaluate intestinal inflammatory and apoptotic processes after intestinal ischemia/reperfusion injury, modulated by pentoxifylline and hypertonic saline.

METHODS

It was allocated into four groups (n=6), 24 male Wistar rats (200 to 250 g) and submitted to intestinal ischemia for 40 min and reperfusion for 80 min: IR (did not receive any treatment); HS group (Hypertonic Saline, 4 ml/kg-IV); PTX group (Pentoxifylline, 30 mg/kg-IV); HS+PTX group (Hypertonic Saline and Pentoxifylline). All animals were heparinized (100 U/kg). At the end of reperfusion, ileal fragments were removed and stained on hematoxylin-eosin and histochemical studies for COX-2, Bcl-2 and cleaved caspase-3.

RESULTS

The values of sO2 were higher on treated groups at 40 minutes of reperfusion (p=0.0081) and 80 minutes of reperfusion (p=0.0072). Serum lactate values were lower on treated groups after 40 minutes of reperfusion (p=0.0003) and 80 minutes of reperfusion (p=0.0098). Morphologic tissue injuries showed higher grades on IR group versus other groups: HS (p=0.0006), PTX (p=0.0433) and HS+PTX (p=0.0040). The histochemical study showed lesser expression of COX-2 (p=0.0015) and Bcl-2 (p=0.0012) on HS+PTX group. A lower expression of cleaved caspase-3 was demonstrated in PTX (p=0.0090; PTXvsIR).

CONCLUSION

The combined use of pentoxifylline and hypertonic saline offers best results on inflammatory and apoptotic inhibitory aspects after intestinal ischemia/reperfusion.

Bacterial translocation and endotoxemia after pringle maneuver in cirrhotic rats

BACKGROUND

Pringle maneuver (Pm) is advocated for the reduction of blood loss during liver surgery, while postoperative infections continue to be a frequent complication after hepatic resection and liver transplantation.

AIM

To investigate the effect of the Pringle maneuver on systemic bacterial translocation and endotoxemia in cirrhotic rats and cirrhotic rats with selective intestinal decontamination.

METHODS

A total of 100 male Sprague-Dawley cirrhotic rats were randomly divided into five equal groups: sham operation, Pm of 10 min, Pm of 20 min, Pm of 30 min, and pretreatment. Tissue samples from mesenteric lymph nodes, liver, lungs, portal, and vena cava vein blood were obtained for culture after 30 min and 24 h of the operation. Endotoxin levels were measured in portal vein and vena cava blood.

RESULTS

Portal vein and vena cava blood endotoxin concentrations increased significantly after 30 min, especially 24 h of operation in the Pm of 20 min and Pm of 30 min groups. A significant increase in contaminated mesenteric lymph nodes, liver, portal, and vena cava blood was noted 24 h later. The incidence of gut bacterial translocation increased with the duration extension of Pm. Escherichia coli was the most common bacteria isolated from the tissues. There was a significant decrease of portal vein and vena cava blood endotoxin concentrations and the incidence of bacterial translocation by selective intestinal decontamination.

CONCLUSIONS

There is endotoxemia immediately after Pringle maneuver and gut bacteria translocation 24 h later. The incidence of gut bacterial translocation increases with the duration extension of Pm. Selective intestinal decontamination can decrease bacteria translocation and endotoxemia.

Novel biomarkers of arterial and venous ischemia in microvascular flaps

The field of reconstructive microsurgery is experiencing tremendous growth, as evidenced by recent advances in face and hand transplantation, lower limb salvage after trauma, and breast reconstruction. Common to all of these procedures is the creation of a nutrient vascular supply by microsurgical anastomosis between a single artery and vein. Complications related to occluded arterial inflow and obstructed venous outflow are not uncommon, and can result in irreversible tissue injury, necrosis, and flap loss. At times, these complications are challenging to clinically determine. Since early intervention with return to the operating room to re-establish arterial inflow or venous outflow is key to flap salvage, the accurate diagnosis of early stage complications is essential. To date, there are no biochemical markers or serum assays that can predict these complications. In this study, we utilized a rat model of flap ischemia in order to identify the transcriptional signatures of venous congestion and arterial ischemia. We found that the critical ischemia time for the superficial inferior epigastric fasciocutaneus flap was four hours and therefore performed detailed analyses at this time point. Histolgical analysis confirmed significant differences between arterial and venous ischemia. The transcriptome of ischemic, congested, and control flap tissues was deciphered by performing Affymetrix microarray analysis and verified by qRT-PCR. Principal component analysis revealed that arterial ischemia and venous congestion were characterized by distinct transcriptomes. Arterial ischemia and venous congestion was characterized by 408 and 1536>2-fold differentially expressed genes, respectively. qRT-PCR was used to identify five candidate genes Prol1, Muc1, Fcnb, Il1b, and Vcsa1 to serve as biomarkers for flap failure in both arterial ischemia and venous congestion. Our data suggests that Prol1 and Vcsa1 may be specific indicators of venous congestion and allow clinicians to both diagnose and successfully treat microvascular complications before irreversible tissue damage and flap loss occurs.

Hepatoprotective effect of commercial herbal extracts on carbon tetrachloride-induced liver damage in Wistar rats

Background:

Various hepatoprotective herbal products from plants are available in Mexico, where up to 85% of patients with liver disease use some form of complementary and alternative medicine. However, only few studies have reported on the biological evaluation of these products.

Objective:

Using a model of carbon tetrachloride (CCl₄)-induced hepatotoxicity in rats, we evaluated the effects of commercial herbal extracts used most commonly in the metropolitan area of Monterrey, Mexico.

Materials and Methods:

The commercial products were identified through surveys in public areas. The effect of these products given with or without CCl₄ in rats was evaluated by measuring the serum concentrations of aspartate amino transferase (AST) and alanine amino transferase (ALT), and histopathological analysis. Legalon^® was used as the standard drug.

Results:

The most commonly used herbal products were Hepatisan^® capsules, Boldo capsules, Hepavida^® capsules, Boldo infusion, and milk thistle herbal supplement (80% silymarin). None of the products tested was hepatotoxic according to transaminase and histological analyses. AST and ALT activities were significantly lower in the Hepavida+CCl₄-treated group as compared with the CCl₄-only group. AST and ALT activities in the silymarin, Hepatisan, and Boldo tea groups were similar to those in the CCl₄ group. The CCl₄ group displayed submassive confluent necrosis and mixed inflammatory infiltration. Both the Hepatisan+CCl₄ and Boldo tea+CCl₄ groups exhibited ballooning degeneration, inflammatory infiltration, and lytic necrosis. The silymarin+CCl₄ group exhibited microvesicular steatosis. The Hepavida+CCl₄- and Legalon+CCL₄-treated groups had lower percentages of necrotic cells as compared with the CCl₄-treated group; this treatment was hepatoprotective against necrosis.

Conclusion:

Only Hepavida had a hepatoprotective effect.

Temporal relationship of serum markers and tissue damage during acute intestinal ischemia/reperfusion

OBJECTIVE

It is essential to identify a serological marker of injury in order to study the pathophysiology of intestinal ischemia reperfusion. In this work, we studied the evolution of several serological markers after intestinal ischemia reperfusion injury in rats. The markers of non-specific cell damage were aspartate aminotransferase, alanine aminotransaminase, and lactic dehydrogenase, the markers of inflammation were tumor necrosis factor alpha, interleukin-6, and interleukin-1 beta, and the markers of intestinal mucosal damage were intestinal fatty acid binding protein and D-lactate. We used Chiús classification to grade the histopathological damage.

METHODS

We studied 35 Wistar rats divided into groups according to reperfusion time. The superior mesenteric artery was clamped for 30 minutes, and blood and biopsies were collected at 1, 3, 6, 12, 24, and 48 hours after reperfusion. We plotted the mean ± standard deviation and compared the baseline and maximum values for each marker using Student's t-test.

RESULTS

The maximum values of interleukin-1 beta and lactic dehydrogenase were present before the maximal histopathological damage. The maximum tumor necrosis factor alpha and D-lactate expressions coincided with histopathological damage. Alanine aminotransaminase and aspartate aminotransferase had a maximum expression level that increased following the histopathological damage. The maximum expressions of interluken-6 and intestinal fatty acid binding protein were not significantly different from the Sham treated group.

CONCLUSION

For the evaluation of injury secondary to acute intestinal ischemia reperfusion with a 30 minute ischemia period, we recommend performing histopathological grading, quantification of D-lactate, which is synthesized by intestinal bacteria and is considered an indicator of mucosal injury, and quantification of tumor necrosis factor alpha as indicators of acute inflammation three hours after reperfusion.

Intestinal injury can be reduced by intra-arterial postischemic perfusion with hypertonic saline

AIM: To investigate the effect of local intestinal perfusion with hypertonic saline (HTS) on intestinal ischemia-reperfusion injury (IRI) in both ex vivo and in vivo rat models.

METHODS: All experiments were performed on male Wistar rats anesthetized with pentobarbital sodium given intraperitoneally at a dose of 60 mg/kg. Ex vivo vascularly perfused rat intestine was subjected to 60-min ischemia and either 30-min reperfusion with isotonic buffer (controls), or 5 min with HTS of 365 or 415 mOsm/L osmolarity (HTS^365mOsm or HTS^415mOsm, respectively) followed by 25-min reperfusion with isotonic buffer. The vascular intestinal perfusate flow (IPF) rate was determined by collection of the effluent from the portal vein in a calibrated tube. Spontaneous intestinal contraction rate was monitored throughout. Irreversible intestinal injury or area of necrosis (AN) was evaluated histochemically using 2.3.5-triphenyltetrazolium chloride staining. In vivo, 30-min ischemia was followed by either 30-min blood perfusion or 5-min reperfusion with HTS^365mOsm through the superior mesenteric artery (SMA) followed by 25-min blood perfusion. Arterial blood pressure (BP) was measured in the common carotid artery using a miniature pressure transducer. Histological injury was evaluated in both preparations using the Chui score.

RESULTS: Ex vivo, intestinal IRI resulted in a reduction in the IPF rate during reperfusion (P < 0.05 vs sham). The postischemic recovery of the IPF rate did not differ between the controls and the HTS^365mOsm group. In the HTS^415mOsm group, postischemic IPF rates were lower than in the controls and the HTS^365mOsm group (P < 0.05). The intestinal contraction rate was similar at baseline in all groups. An increase in this parameter was observed during the first 10 min of reperfusion in the control group as compared to the sham-treated group, but no such increase was seen in the HTS^365mOsm group. In controls, AN averaged 14.8% ± 5.07% of the total tissue volume. Administration of HTS^365mOsm for 5 min after 60-min ischemia resulted in decrease in AN (5.1% ± 1.20% vs controls, P < 0.01). However, perfusion of the intestine with the HTS of greater osmolarity (HTS^415mOsm) failed to protect the intestine from irreversible injury. The Chiu score was lower in the HTS^365mOsm group in comparison with controls (2.4 ± 0.54 vs 3.2 ± 0.44, P = 0.042), while intestinal perfusion with HTS^415mOsm failed to improve the Chiu score. Intestinal reperfusion with HTS^365mOsm in the in vivo series secured rapid recovery of BP after its transient fall, whereas in the controls no recovery was seen. The Chiu score was lower in the HTS^365mOsm group vs controls (3.1 ± 0.26 and 3.8 ± 0.22, P = 0.0079 respectively,), although the magnitude of the effect was lower than in the ex vivo series.

CONCLUSION: Brief intestinal postischemic perfusion with HTS^365mOsm through the SMA followed by blood flow restoration is a protective procedure that could be used for the prevention of intestinal IRI.

Increased endothelin-1 vasoconstriction in mesenteric resistance arteries after superior mesenteric ischaemia-reperfusion

BACKGROUND AND PURPOSE

Endothelin-1 (ET-1) plays an important role in the maintenance of vascular tone. We aimed to evaluate the influence of superior mesenteric artery (SMA) ischaemia-reperfusion (I/R) on mesenteric resistance artery vasomotor function and the mechanism involved in the changes in vascular responses to ET-1.

EXPERIMENTAL APPROACH

SMA from male Sprague-Dawley rats was occluded (90 min) and following reperfusion (24h), mesenteric resistance arteries were dissected. Vascular reactivity was studied using wire myography. Protein and mRNA expression, superoxide anion (O(2) (•-) ) production and ET-1 plasma concentration were evaluated by immunofluorescence, real-time quantitative PCR, ethidium fluorescence and elisa, respectively.

KEY RESULTS

I/R increased ET-1 plasma concentration, ET-1-mediated vasoconstriction and ET(B) mRNA expression, and down-regulated ET(A) mRNA expression. Immunofluorescence confirmed mRNA results and revealed an increase in ET(B) receptors in the mesenteric resistance artery media layer after I/R. Therefore, the ET(B) receptor agonist sarafotoxin-6 induced a contraction that was inhibited by the ET(B) receptor antagonist BQ788 only in vessels, with and without endothelium, from I/R rats. Furthermore, BQ788 potentiated ET-1 vasoconstriction only in sham rats. Endothelium removal in rings from I/R rats unmasked the inhibition of ET-1 vasoconstriction by BQ788. Endothelium removal, N(ω) -nitro-L-arginine methyl ester and superoxide dismutase abolished the differences in ET-1 vasoconstriction between sham and I/R rats. We also found that I/R down-regulates endothelial NOS mRNA expression and concomitantly enhanced O(2) (•-) production by increasing NADPH oxidase 1 (NOX-1) and p(47phox) mRNA.

CONCLUSIONS AND IMPLICATIONS

Mesenteric I/R potentiated the ET-1-mediated vasoconstriction by a mechanism that involves up-regulation of muscular ET(B) receptors and decrease in NO bioavailability.

The effect of bevacizumab on colon anastomotic healing in rats

PURPOSE

The aim of the study was to investigate the effect of angiogenesis inhibition by bevacizumab, a monoclonal anti-vascular endothelial growth factor (VEGF) antibody, on the healing process of colonic anastomoses in rats, assessing some specific involved factors. This new agent is used mainly in metastatic colorectal cancer. The angiogenesis plays an important role in both wound healing and metastatic invasion and spread of malignant cells. There has not been any evidence assessing the optimal time for its safe use in operated patients.

MATERIALS AND METHODS

Forty Wistar rats were randomly allocated into four equal groups. A colonic anastomosis was performed in all rats. Half of them received intraoperatively a single dose of bevacizumab 5 mg/body weight and the rest received placebo. The animals were sacrificed on the 7th (Avastin 7th, placebo 7th) and 14th (Avastin 14th, placebo 14th) postoperative day. The anastomosis was resected and sent for histological study and for tissue biochemical assays (VEGF, endothelin-1 (ET-1), C-reactive protein (CRP), pro-oxidant-antioxidant balance (PAB), carbonylated proteins, hydroxyproline) using specific enzyme-linked immunosorbent assay kits. For statistical analysis, the Mann-Whitney U test was used (of statistical significance when P < 0.05).

RESULTS

No complication or anastomotic dehiscence was observed. Histology did not reveal statistically significant differences between groups concerning degree of inflammation, fibroblasts, collagen, and fibrosis. Likewise, hydroxyproline levels did not differ. However, some statistically significant differences were found in VEGF, CRP and carbonyl proteins (Avastin 7th vs placebo 7th, placebo 14th vs placebo 7th), ET-1, and PAB (Avastin 14th vs Avastin 7th), which did not finally affect the collagen synthesis marker hydroxyproline, nor did the anastomotic strength.

CONCLUSIONS

Bevacizumab, when administered intraoperatively, has no significant effect on colon anastomotic healing in rats despite a transient mild ischemia.