Enhanced potency of cell-based therapy for ischemic tissue repair using an injectable bioactive epitope presenting nanofiber support matrix

The translation of cell-based therapies for ischemic tissue repair remains limited by several factors, including poor cell survival and limited target site retention. Advances in nanotechnology enable the development of specifically designed delivery matrices to address these limitations and thereby improve the efficacy of cell-based therapies. Given the relevance of integrin signaling for cellular homeostasis, we developed an injectable, bioactive peptide-based nanofiber matrix that presents an integrin-binding epitope derived from fibronectin, and evaluated its feasibility as a supportive artificial matrix for bone marrow-derived pro-angiogenic cells (BMPACs) used as a therapy in ischemic tissue repair. Incubation of BMPACs with these peptide nanofibers in vitro significantly attenuated apoptosis while enhancing proliferation and adhesion. Pro-angiogenic function was enhanced, as cells readily formed tubes. These effects were, in part, mediated via p38, and p44/p42 MAP kinases, which are downstream pathways of focal adhesion kinase. In a murine model of hind limb ischemia, an intramuscular injection of BMPACs within this bioactive peptide nanofiber matrix resulted in greater retention of cells, enhanced capillary density, increased limb perfusion, reduced necrosis/amputation, and preserved function of the ischemic limb compared to treatment with cells alone. This self-assembling, bioactive peptide nanofiber matrix presenting an integrin-binding domain of fibronectin improves regenerative efficacy of cell-based strategies in ischemic tissue by enhancing cell survival, retention, and reparative functions.

Effect of rhubarb pre-treatment on intestinal microcirculation in septic rats

The intestine plays a vital role in the pathophysiology of sepsis development. The objective of the present study was to explore the effects of rhubarb on intestinal microcirculation in septic rats. We used moorFLPI laser speckle imaging to detect the blood flow of the intestinal mucosa and wall. Using an ELISA, we assayed the concentration of lactate (L) and pyruvic acid (P) in the intestinal tissue to calculate the ratio of lactate to pyruvic acid (L/P ratio). To observe the intestinal mucosal capillaries, gelatin and ink were perfused into the intestine and subsequently stained with hematoxylin and eosin (HE) to measure the ratio of the vessel area. We then used immunohistochemistry to measure CD31 expression. Using an MTT assay, the effect of the rhubarb extract on the proliferation of human umbilical vein endothelial cells (HUVECs) was analyzed. The blood flow in the intestinal wall and mucosa of the control, sham and rhubarb-treated groups was significantly higher, while the sepsis group had relatively low blood flow. The L/P ratio in the intestinal tissue was larger in the sepsis group than in the other three groups. The microvascular area (MVA) in the sepsis group was smaller than in the control group, sham group or rhubarb group. Positive expression for CD31 was observed in the cytoplasm of vascular endothelial cells. The intestinal mucosal capillaries were reduced in septic rats as compared to the other three groups. HUVEC proliferation was enhanced by the rhubarb extract monomers at 1 μmol/L, but suppressed at higher concentrations of 10 to 100 μmol/L. These results suggest that pre-treatment with rhubarb prior to sepsis induction promotes the expansion of the intestinal mucosal capillaries, protects intestinal mucosal capillary endothelial cells and increases the number of functional intestinal capillaries.

Validation of optimal DCE-MRI perfusion threshold to classify at-risk tumor imaging voxels in heterogeneous cervical cancer for outcome prediction

PURPOSE

To classify tumor imaging voxels at-risk for treatment failure within the heterogeneous cervical cancer using DCE MRI and determine optimal voxel's DCE threshold values at different treatment time points for early prediction of treatment failure.

MATERIAL AND METHOD

DCE-MRI from 102 patients with stage IB2-IVB cervical cancer was obtained at 3 different treatment time points: before (MRI 1) and during treatment (MRI 2 at 2-2.5 weeks and MRI 3 at 4-5 weeks). For each tumor voxel, the plateau signal intensity (SI) was derived from its time-SI curve from the DCE MRI. The optimal SI thresholds to classify the at-risk tumor voxels was determined by the maximal area under the curve using ROC analysis when varies SI value from 1.0 to 3.0 and correlates with treatment outcome.

RESULTS

The optimal SI thresholds for MRI 1, 2 and 3 were 2.2, 2.2 and 2.1 for significant differentiation between local recurrence/control, respectively, and 1.8, 2.1 and 2.2 for death/survival, respectively.

CONCLUSION

Optimal SI thresholds are clinically validated to quantify at-risk tumor voxels which vary with time. A single universal threshold (SI=1.9) was identified for all 3 treatment time points and remained significant for the early prediction of treatment failure.

Exercise training in hypertension: Role of microRNAs

Hypertension is a complex disease that constitutes an important public health problem and demands many studies in order to understand the molecular mechanisms involving his pathophysiology. Therefore, an increasing number of studies have been conducted and new therapies are continually being discovered. In this context, exercise training has emerged as an important non-pharmacological therapy to treat hypertensive patients, minimizing the side effects of pharmacological therapies and frequently contributing to allow pharmacotherapy to be suspended. Several mechanisms have been associated with the pathogenesis of hypertension, such as hyperactivity of the sympathetic nervous system and renin-angiotensin aldosterone system, impaired endothelial nitric oxide production, increased oxygen-reactive species, vascular thickening and stiffening, cardiac hypertrophy, impaired angiogenesis, and sometimes genetic predisposition. With the advent of microRNAs (miRNAs), new insights have been added to the perspectives for the treatment of this disease, and exercise training has been shown to be able to modulate the miRNAs associated with it. Elucidation of the relationship between exercise training and miRNAs in the pathogenesis of hypertension is fundamental in order to understand how exercise modulates the cardiovascular system at genetic level. This can be promising even for the development of new drugs. This article is a review of how exercise training acts on hypertension by means of specific miRNAs in the heart, vascular system, and skeletal muscle.

Long-term effects of an exercise and Mediterranean diet intervention in the vascular function of an older, healthy population

BACKGROUND

Preserving endothelial function and microvascular integrity is suggested to reduce cardiovascular disease risk. It was recently shown that the age-dependent decline in endothelial and microvascular integrity may be reversed when combining exercise with Mediterranean diet (MD) in an 8-week intervention. The present study investigates whether the risk-reduction improvement in microcirculatory and cardiorespiratory functions are sustained in this age-group after a 1-year follow-up.

DESIGN AND METHODS

Twenty sedentary healthy participants (age, 55±4years) from the original study underwent cardiopulmonary exercise tolerance test and were assessed for their upper- and lower-limb vascular endothelial cutaneous vascular conductance (CVC) using laser Doppler fluximetry (LDF) with endothelium-dependent [ACh (acetylcholine chloride)] and endothelium-independent [SNP (sodium nitroprusside)] vasodilation, 1year after completing the intervention.

RESULTS

Both MD and exercise groups appeared to have an improved microvascular responses, in comparison to baseline as far as ACh is concerned. Exploring the interactions between the time point and the original group, however, revealed a stronger improvement in the MD group in comparison to the exercise group, for ACh (p=0.04, d=0.41). In the upper body, the time point and group interaction for ACh, indicated a better improvement for MD, without however statistical significance (p=0.07, d=0.24). Additionally, cardiorespiratory improvement in ventilatory threshold was maintained, 1year after (12.2±3.0 vs. 13.2±3.2ml∙kg(-1)∙min(-1), p<0.05).

CONCLUSIONS

The original improvements from an 8-week exercise and MD intervention were still evident, particularly in the microcirculatory and cardiorespiratory assessments, 1year after the initial study. This suggests that a brief intervention combining MD with exercise in this high-risk group promises long-term health benefits.

Pentoxifylline attenuates leukocyte-endothelial interactions in a two-hit model of shock and sepsis

BACKGROUND

This study investigated the effects of pentoxifylline (PTX) combined with resuscitation fluids on microcirculatory dysfunctions in a two-hit model of shock and sepsis.

MATERIALS AND METHODS

Male Wistar rats (250 g) were submitted to hemorrhagic shock and reperfusion followed by sepsis induced by cecal ligation and puncture. For the initial treatment of shock, rats were randomly divided into: sham, no injury, no treatment; hypertonic saline solution (HS) (7.5%, 4 mL/kg); lactated Ringer's solution (LR, 3 × shed blood volume); HS + PTX (4 mL/Kg + 25 mg/kg PTX); and LR + PTX (3 × shed blood volume + 25 mg/kg PTX). After 48 h of being exposed to the double injury, leukocyte-endothelial interactions were assessed by intravital microscopy of the mesentery. Endothelial expression of P-selectin and intercellular adhesion molecule-1 (ICAM-1) was evaluated by immunohistochemistry, as well as lung neutrophil infiltration by histology.

RESULTS

Lactated Ringer's solution induced marked increases (P < 0.001) in the number of rolling leukocytes per 10 min (two-fold), adherent leukocytes per 100 μm venule length (six-fold), migrated leukocytes per 5000 μm(2) (eight-fold), P-selectin and ICAM-1 expression (four-fold), and lung neutrophil infiltration (three-fold) compared with sham. In contrast, PTX attenuated leukocyte-endothelial interactions, P-selectin and ICAM-1 expression at the mesentery when associated with either LR (P < 0.001) or HS (P < 0.05). Neutrophil migration into the lungs was similarly reduced by PTX (P < 0.05).

CONCLUSIONS

Data presented showed that pentoxifylline attenuates microcirculatory disturbances at the mesenteric bed with significant minimization of lung inflammation after a double-injury model of hemorrhagic shock and reperfusion followed by sepsis.

Effects of glutamine alone on the acute necrotizing pancreatitis in rats

BACKGROUND

The effects of the glutamine on the acute pancreatitis are controversial in the clinical and experimental studies. The aim of this study was to investigate the influence of glutamine alone on acute necrotizing pancreatitis (ANP) induced by glycodeoxycholic acid in rats.

MATERIAL AND METHODS

Fifty-two male Sprague-Dawley rats weighing 300-350 g were used. Rats were divided into four groups as sham + saline, sham + glutamine, ANP + saline and ANP + glutamine. ANP in rats was induced by glycodeoxycholic acid. The extent of acinar cell injury, mortality, systemic cardiorespiratory variables, functional capillary density, renal/hepatic functions, and changes in some enzyme markers for pancreatic and lung tissue were investigated during ANP in rats.

RESULTS

The induction of ANP resulted in a significant increase in the mortality rate, pancreatic necrosis, and serum activity of amylase, alanine aminotransferase, interleukin-6, lactate dehydrogenase in bronchoalveolar lavage fluid, serum concentration of urea, and tissue activity of myeloperoxidase and malondialdehyde in the pancreas and lung, and a significant decrease in concentrations of calcium, blood pressure, urine output, pO2, and functional capillary density. The use of glutamine alone improved these changes.

CONCLUSIONS

Glutamine demonstrated beneficial effect on the course of ANP in rats. Therefore, it may be used by itself in the treatment of acute pancreatitis.

Effects of a hemoglobin-based oxygen carrier (HBOC-201) and derivatives with altered oxygen affinity and viscosity on systemic and microcirculatory variables in a top-load rat model

The effects of a polymerized bovine hemoglobin-based oxygen carrier (HBOC) and two derivatives on arteriolar vasoactivity and tissue oxygen tension were explored by administering HBOC in a dose-response fashion to normovolemic rats. The effect of oxygen affinity (P50) and viscosity was also explored, where the P50 and viscosity of the parent compound (HBOC-201) and its modifications (MP50 and LP50A) were as follows: 40mmHg and 3.0cP (HBOC-20l); 18mmHg and 4.4cP (MP50); and 17mmHg and 12.1cP (LP50A). Anesthetized male Sprague-Dawley rats (N=32) were randomized to receive one of the HBOC solutions, and were administered four infusions that increased in concentration for each dose (2, 22, 230 and 780mg/kg, IV). Data were compared to rats receiving an equivalent volume for each of the four infusions (0.4, 0.4, 3.8, 13.1ml/kg, IV) of iso-oncotic 5.9% human serum albumin (HSA). Increasing doses of either HBOC solutions or HSA were associated with increasing MAP. Doses 3 and 4 of HBOC-201, MP50 and HSA produced significant increases in MAP, whereas similar increases began at a lower dose (Dose 2) with LP50A. There were no significant changes in arteriolar diameters at any dose for any group. Interstitial partial pressure of oxygen (ISF PO2) remained unchanged for HBOC-201, MP50 and HSA, but LP50A caused a significant decrease in ISF PO2 compared to baseline after Doses 3 and 4. In conclusion, there was no evidence that HBOC-201 would perform better with increased oxygen affinity (40 to 18mmHg) or viscosity (3.0 to 4.4cP).

Microcirculatory oxygen transport and utilization

The cardiovascular system (macrocirculation) circulates blood throughout the body, but the microcirculation is responsible for modifying tissue perfusion and adapting it to metabolic demand. Hemodynamic assessment and monitoring of the critically ill patient is typically focused on global measures of oxygen transport and utilization, which do not evaluate the status of the microcirculation. Despite achievement and maintenance of global hemodynamic and oxygenation goals, patients may develop microcirculatory dysfunction with associated organ failure. A thorough understanding of the microcirculatory system under physiologic conditions will assist the clinician in early recognition of microcirculatory dysfunction in impending and actual disease states.

Influence of ISDN, L-NAME and selenium on microcirculation, leukocyte endothelium interaction and angiogenesis after frostbite

BACKGROUND

The body of knowledge regarding the different facets of frostbite injury continues to expand. However, beside the administration of physiological saline, local rewarming, local disinfection and symptomatic medications, today no causal therapy is known which would accelerate angiogenesis and wound healing. The aim of this study was to investigate the influences of dilative acting drugs on microcirculation, angiogenesis and leukocyte behavior.

MATERIALS AND METHODS

Ears of male hairless mice (n=40) were inflicted with full thickness frostbites using a cold air jet. Then the affects of four intraperitoneal injections of isosorbitdinitrate (ISDN, n=10), l-nitroarginine-methyl-ester (l-NAME, n=10), selenium (n=10) or sodium chloride (n=10; each administered to one of four corresponding study groups), on microcirculation, leukocyte-endothelial interaction and angiogenesis were investigated over a 12-day period using intravital fluorescent microscopy.

RESULTS

Angiogenesis was most improved by ISDN (36.8 vs. 54.5% non-perfused area on day 3, 3.9 vs. 17.0% on day 7 compared to selenium, p<0.006). Venular diameter was most significantly dilated in the ISDN-group, l-NAME showed significantly decreased diameter over the complete time of 12 days. ISDN had positive influences on edema formation, which was significantly reduced compared to control (27% lower values compared to control; p=0.007 on day 3). The l-NAME-group showed the significant highest leukocyte-adhesion compared to control on days 7 and 12 (53% resp. 58% higher, p<0.006).

CONCLUSION

Overall, out of all the drugs tested, ISDN improved angiogenesis, dilated venules and decreased edema formation and therefore seems to have the greatest positive impact on these crucial parameters after frostbite injury.

Transcutaneous oxygen tension monitoring in critically ill patients receiving packed red blood cells

PURPOSE

Whether transfusions of packed red blood cells (PRBCs) affect tissue oxygenation in stable critically ill patients is still matter of discussion. The microvascular capacity for tissue oxygenation can be determined noninvasively by measuring transcutaneous oxygen tension (tcpO2). The aim of this study was to assess tissue oxygenation by measuring tcpO2 in stable critically ill patients receiving PRBC transfusions.

METHODS

Nineteen stable critically ill patients, who received 2 units of PRBC, were prospectively included into this pilot study. Transcutaneous oxygen tension was measured continuously during PRBC transfusions using Clark's electrodes. In addition, whole blood viscosity and global hemodynamics were determined.

RESULTS

Reliable measurement signals during continuous tcpO2 monitoring were observed in 17 of 19 included patients. Transcutaneous oxygen tension was related to the global oxygen consumption (r=-0.78; P=.003), the arterio-venous oxygen content difference (r=-0.65; P=.005), and the extraction rate (r=-0.71; P=.02). The transfusion-induced increase of the hemoglobin concentration was paralleled by an increase of the whole blood viscosity (P<.001). Microvascular tissue oxygenation by means of tcpO2 was not affected by PRBC transfusions (P=.46). Packed red blood cell transfusions resulted in an increase of global oxygen delivery (P=.02) and central venous oxygen saturation (P=.01), whereas oxygen consumption remained unchanged (P=.72).

CONCLUSIONS

In stable critically ill patients, microvascular tissue oxygenation can be continuously monitored by Clark's tcpO2 electrodes. According to continuous tcpO2 measurements, the microvascular tissue oxygenation is not affected by PRBC transfusions.

Abnormal amplitude and kinetics of digital postocclusive reactive hyperemia in systemic sclerosis

OBJECTIVES

Postocclusive reactive hyperemia is mediated by two major mediators: sensory nerves and endothelium-derived hyperpolarizing factors. We hypothesized that the skin microvascular response to 5 min ischemia would differ depending upon the hand location in patients with systemic sclerosis (SSc), primary Raynaud's phenomenon (PRP) and healthy controls.

METHODS

Fifteen patients with SSc, 15 sex- and age-matched patients with PRP and healthy controls were enrolled. Their right hands were subjected to 5 min ischemia followed by a postocclusive hyperemia test, with local microcirculation monitoring by laser speckle contrast imaging on the dorsal face of the hand.

RESULTS

Postocclusive reactive hyperemia was abnormal in terms of peak and area under the curve (AUC) on all fingers except the thumb in patients with SSc and PRP compared with controls. In contrast, the kinetics of the response was longer only in SSc patients, with mean (SD) time to peak on the index, middle and ring finger were respectively 72 (58), 73 (51) and 67 (47) s for SSc; 40 (20), 40 (20) and 36 (19) s for PRP; and 34 (30), 34 (30) and 29 (24) s for controls (P=0.009 for interaction).

CONCLUSIONS

We observed decreased distal digital microvascular perfusion following 5 min of ischemia in patients presenting with PRP or SSc, while the kinetics was prolonged only in SSc. A dynamic assessment of digital skin blood flow using laser speckle contrast imaging following 5 min ischemia could be used as a tool to assess microvascular abnormalities in patients with Raynaud's phenomenon secondary to SSc.

Serial assessment of laser Doppler flow during acute pain crises in sickle cell disease

Changes in basal laser Doppler flowmetry (LDF) of skin blood flow in sickle cell disease are reported to have pathophysiologic relevance in pain crisis. This is the first study to strictly control for LDF variability in determining the value of serial, basal (unprovoked) skin LDF as a practical method to assess resolution of acute pain crisis in sickle cell patients. Daily LDF measurements were repeated on the exact same skin areas of the calf and forehead throughout each of 12 hospital admissions for uncomplicated acute pain crisis. A progressive increase in perfusion was observed in the calf throughout hospitalization as pain crisis resolved, but measurement reproducibility in the calf was poor. Reproducibility in the forehead was better, but no significant trend over time in perfusion was seen. There was no significant correlation between perfusion and pain scores over time. There was also no significant pattern of LDF oscillations over time. In conclusion, only perfusion units and not oscillatory patterns of LDF have probable pathophysiological significance in sickle cell disease vaso-occlusion. The reproducibility of basal skin LDF specifically in sickle cell disease needs to be confirmed.

Impact of closed minimal extracorporeal circulation on microvascular tissue perfusion during surgical aortic valve replacement: intravital imaging in a prospective randomized study

OBJECTIVES

Closed minimal extracorporeal circulation (MECC) systems currently do not represent the standard of surgical care for open-heart surgery. Yet, considering the beneficial results reported for coronary artery bypass graft (CABG) surgery, we used an MECC system in aortic valve replacement (AVR) and analysed the effects on intraoperative microvascular perfusion in comparison with conventional open extracorporeal circulation (CECC).

METHODS

In the current study, we analysed alterations in microvascular perfusion at 4 predefined time points (T1-T4) during surgical AVR utilizing orthogonal polarization spectral (OPS) imaging. Twenty patients were randomized for being operated on utilizing either MECC or CECC. Changes in functional capillary density (FCD, cm/cm(2)), mircovascular blood flow velocity (mm/s) and vessel diameter (μm) were analysed by a blinded investigator.

RESULTS

After the start of extracorporeal circulation and aortic cross-clamping (T2), both groups showed a significant drop in FCD, but with a significantly higher FCD in the MECC group (153.1 ± 15.0 cm/cm² in the CECC group vs 160.8 ± 12.2 cm/cm² in the MECC group, P = 0.034). During the late phase of the cardiopulmonary bypass (CPB) (T3), the FCD was still significantly depressed in both treatment groups (153.5 ± 14.6 cm/cm² in the CECC group, P <0.05 vs 'T1'; 159.5 ± 12.4 cm/cm² in the MECC group, P <0.05 versus 'T1'). After termination of CPB (T4), the FCD recovered in both groups to baseline values. Microvascular blood flow velocity tended to remain at a higher level in the MECC group, whereas haemodilution during CPB was significantly reduced in the MECC group.

CONCLUSIONS

The use of MECC in AVR did not affect procedural safety and, resulted in beneficial preservation of microvascular blood flow velocity and significantly reduced haemodilution during CPB. In contrast to CABG surgery, the use of MECC did not improve FCD during surgical AVR. Clinical advantages possibly resulting from attenuated haemodilution and preservation of microvascular blood flow velocity require further validation in larger patient cohorts.

Characterization of nanoparticle delivery in microcirculation using a microfluidic device

This work focuses on the characterization of particle delivery in microcirculation through a microfluidic device. In microvasculature the vessel size is comparable to that of red blood cells (RBCs) and the existence of blood cells largely influences the dispersion and binding distribution of drug loaded particles. The geometry of the microvasculature leads to non-uniform particle distribution and affects the particle binding characteristics. We perform an in vitro study in a microfluidic chip with micro vessel mimicking channels having a rectangular cross section. Various factors that influence particle distribution and delivery such as the vessel geometry, shear rate, blood cells, particle size, particle antibody density are considered in this study. Around 10% higher particle binding density is observed at bifurcation regions of the mimetic microvasculature geometry compared to straight regions. Particle binding density is found to decrease with increased shear rates. RBCs enhance particle binding for both 210 nm and 2 μm particles for shear rates between 200-1600 s(-1) studied. The particle binding density increases about 2-3 times and 6-10 times when flowing in whole blood at 25% RBC concentration compared to the pure particle case, for 210 nm and 2 μm particles respectively. With RBCs, the binding enhancement is more significant for 2 μm particles than that for 210 nm particles, which indicates an enhanced size dependent exclusion of 2 μm particles from the channel centre to the cell free layer (CFL). Increased particle antibody coating density leads to higher particle binding density for both 210 nm and 2 μm particles.

Accumulation of microvascular target organ damage in newly diagnosed hypertensive patients

Early identification of hypertensive target organ damage (TOD) emerges as important for global cardiovascular risk assessment. Retinal vascular alterations, capillary rarefaction, and microalbuminuria represent different forms of microvascular TOD. However, data regarding their concomitant presence in the early stages of hypertension, the association of the number of affected organs with cardiovascular risk, and aldosterone effect on multiple TOD are lacking. We studied naïve, never-treated patients with recent duration of hypertension and healthy volunteers. Innovative software was developed to estimate retinal vascular diameters and capillary density. Biochemical parameters including microalbuminuria and serum aldosterone were derived. Framingham Risk Score was used to determine cardiovascular risk. In total 103 subjects, 66 hypertensives and 37 normotensives, were included. Hypertensive patients exhibited a greater number of affected target organs compared with normotensives (P = .014), with retinopathy and capillary rarefaction (40.9%) representing the most common TOD among hypertensives. The number of affected organs was linearly correlated with increased Framingham score and serum aldosterone, analyzed with univariate (P < .001 and P = .002) and multivariate analysis (P = .025 and P = .004), respectively. Physicians dealing with hypertensive patients should be aware of the possibility of diffuse microvascular impairment and seek multiple TOD even in the early stages of hypertension.

Nail fold capillary diameter changes in acute systemic hypoxia

The present study was undertaken to determine the effect of arterial blood hypoxemia induced by acute systemic hypoxia (pO2=12%) on capillary recruitment and diameter, and red blood cell (RBC) velocity in human nail fold capillaries during rest, arterial post-occlusive reactive hyperemia (PRH), and venous occlusion (VO) using intravital video-capillaroscopy. Capillary recruitment was unchanged in acute systemic hypoxia (H) versus normoxia (N). There was no difference in RBC velocity measurements between normoxia and hypoxia (P<0.63). However, a statistically significant increase in nail fold capillary total width (N, 39.9±9.1 vs. H, 42.7±10.3 μm; P<0.05), apical diameter (N, 15.5±4.3 vs. H, 16.8±4.3 μm; P<0.05), arterial diameter (N, 11.9±3.5 vs. H, 13.9±4.1 μm; P<0.05), and venous diameter (N, 15.5±4.3 vs. H, 17.2±4.8 μm; P<0.05) was observed and continued to be significant most often during post-occlusive reactive hyperemia (PRH) and venous congestion (VO). These data suggest that acute systemic hypoxia does not increase capillary recruitment, but instead increases capillary diameter, resulting in increased capillary blood flow.

Post-resuscitation intestinal microcirculation: its relationship with sublingual microcirculation and the severity of post-resuscitation syndrome

OBJECTIVE

Post-resuscitation syndrome has been recognized as one of the major causes of the poor outcomes of cardiopulmonary resuscitation. The aims of this study were to investigate the intestinal microcirculatory changes following cardiopulmonary resuscitation and relate those changes to sublingual microcirculation and the severity of post-resuscitation syndrome as measured by myocardial function and serum inflammatory cytokine levels.

METHODS

Twenty-five rats were randomized into three groups: (1) short duration of cardiac arrest (n=10): ventricular fibrillation (VF) was untreated for 4 min prior to 6 min of cardiopulmonary resuscitation (CPR); (2) long duration of cardiac arrest (n=10): VF was untreated for 8 min followed by 8 min of CPR; (3) sham control group (n=5): a sham operation was performed without VF induction and CPR. Intestinal and sublingual microcirculatory blood flow was visualized by a sidestream dark-field (SDF) imaging device at baseline and 1, 2, 4, 6, 8 h post-resuscitation. Myocardial function was measured by echocardiography and serum cytokine levels (TNF-α and IL-6) were measured by enzyme-linked immunosorbent assay (ELISA).

RESULTS

Both intestinal and sublingual microcirculatory blood flow decreased significantly with increasing duration of cardiac arrest and resuscitation. The decreases in intestinal microcirculatory blood flow were closely correlated with the reductions of sublingual microcirculatory blood flow (perfused small vessels density: r=0.772, p<0.01; microcirculatory flow index: r=0.821, p<0.01). The decreased microcirculatory blood flow was closely correlated with weakened myocardial function and elevated inflammatory cytokine levels.

CONCLUSIONS

The severity of post-resuscitation intestinal microcirculatory dysfunction is closely correlated with that of myocardial function and inflammatory cytokine levels. The measurement of sublingual microcirculation reflects changes of intestinal microcirculation and may therefore provide a new option for post-resuscitation monitoring.

Repetitive extracorporeal shock wave applications are superior in inducing angiogenesis after full thickness burn compared to single application

OBJECTIVE

Burn wounds remain a challenge due to subsequent wound infection and septicemia, which can be prevented by acceleration of wound healing. The aim of the study was to analyze microcirculation and leukocyte endothelium interaction with particular focus on angiogenesis after full-thickness burn using three different repetitions of low energy shock waves.

METHODS

Full-thickness burns were inflicted to the ears of hairless mice (n=44; area: 1.6±0.05 mm2 (mean±SEM)). Mice were randomized into four groups: the control group received a burn injury but no shock waves; group A received ESWA (0.03 mJ/mm2) on day one after burn injury; group B received shock waves on day one and day three after burn injury; group C ESWA on day one, three and seven after burn injury. Intravital fluorescent microscopy was used to assess microcirculatory parameters, angiogenesis and leukocyte interaction. Values were obtained before burn (baseline value) immediately after and on days 1, 3, 7 and 12 after burn.

RESULTS

Shock-wave treated groups showed significantly accelerated angiogenesis compared to the control group. The non-perfused area (NPA) is regarded as a parameter for angiogenesis and showed the following data on day 12 2.7±0.4% (group A, p=0.001), 1.4±0.5% (group B, p<0.001), 1.0±0.3% (group C, p<0.001), 6.1±0.9% (control group). Edema formation is positively correlated with the number of shock wave applications: day 12: group A: 173.2±9.8%, group B: 184.2±6.6%, group C: 201.1±6.9%, p=0.009 vs. control: 162.3±8.7% (all data: mean±SEM).

CONCLUSION

According to our data shock waves positively impact the wound healing process following burn injury. Angiogenesis showed significantly improved activity after shock wave application. In all three treatment groups angiogenesis was higher compared to the control group. Within the ESWA groups, double applications showed better results than single application and three applications showed better results than single or double applications.

Regional oxygen saturation index (rSO2) in brachioradialis and deltoid muscle. Correlation and prognosis in patients with respiratory sepsis

OBJECTIVE

To compare oxygen saturation index (rSO2) obtained simultaneously in two different brachial muscles.

DESIGN

Prospective and observational study.

SETTING

Intensive care unit.

PATIENTS

Critically ill patients with community-acquired pneumonia.

INTERVENTIONS

Two probes of NIRS device (INVOS 5100) were simultaneously placed on the brachioradialis (BR) and deltoid (D) muscles.

VARIABLES

rSO2 measurements were recorded at baseline (ICU admission) and at 24h. Demographic and clinical variables were registered. Pearson's correlation coefficient was used to assess the association between continuous variables. The consistency of the correlation was assessed using the intraclass correlation coefficient (ICC) and Bland-Altman plot. The predictive value of the rSO2 for mortality was calculated by ROC curve.

RESULTS

Nineteen patients were included with an ICU mortality of 21.1%. The rSO2 values at baseline and at 24h were significantly higher in D than in BR muscle. Values obtained simultaneously in both limbs showed a strong correlation and adequate consistency: BR (r=0.95; p<0.001; ICC=0.94; 95% CI: 0.90-0.96; p<0.001), D (r=0.88; p=0.01; ICC=0.88; 95% CI: 0.80-0.90; p>0.001) but a wide limit of agreement. Non-survivors had rSO2 values significantly lower than survivors at all times of the study. No patient with rSO2 >60% in BR died, and only 17.6% died with an rSO2 value >60% in D. Both muscles showed consistent discriminatory power for mortality.

CONCLUSION

Both BR and D muscles were appropriate for measuring rSO2.

Effects of terlipressin on microcirculation of small bowel mesentery in rats with endotoxic shock

BACKGROUND

Septic shock is still related to unacceptably high morbidity and mortality. Microcirculatory alteration has been demonstrated to be one important reason associated with this evolution. Vasoactive drugs are often used to restore adequate arterial pressure and tissue perfusion in septic shock. To define the roles of different drugs, the effects of terlipressin (TP) on the microcirculation of small bowel mesentery in rats with endotoxic shock were evaluated and compared with those of norepinephrine (NE).

METHODS

Twenty-five adult male Wistar rats were randomized to the control (n = 5), TP (n = 10), and NE (n = 10) groups. After endotoxic shock was induced by intravenous lipopolysaccharide administration for 30 min, rats in the NE and TP groups were infused with saline 5 mL/kg/h and simultaneously given NE 4 μg/kg/min or TP 8 μg/kg/h. The mean arterial pressure, heart rate, blood gas analysis, and microvascular blood flow images of small bowel mesentery were recorded.

RESULTS

After fluid resuscitation and vasopressor infusion, the mean arterial pressure was restored to the baseline values in the NE and TP groups. In the TP group, the heart rate was significantly lower compared with the NE group (P = 0.013). The proportion of perfused vessels and the microvascular flow index (MFI) were significantly increased; furthermore, the heterogeneity index of small vessels was markedly decreased in both the interventional groups with respect to the control group. Compared with the NE group, the MFI was significantly higher (P < 0.05) and the heterogeneity index was significantly lower (P < 0.05) in the TP group.

CONCLUSIONS

Both TP and NE improved hemodynamic and microcirculatory alterations in rats with endotoxic shock. Compared with NE, TP was more effective in promoting MFI and improving the heterogeneity of small bowel mesentery in rats.

Retinal microvascular structure and function in patients with risk factors of atherosclerosis and coronary artery disease

OBJECTIVE

Retinal microvascular signs are markers of cardiovascular disease risk. There are limited data, on relationships between retinal microvascular signs and retinal microvascular endothelial function. We sought to determine the relationship of retinal vascular signs with retinal microvascular endothelial function in patients with or at high risk of coronary artery disease.

METHODS

Participants with atherosclerosis risk factors and coronary disease (n=258; mean age 57±11 years) were recruited to have static and dynamic retinal vascular assessment. Retinal arteriolar dilatation in response to flicker light (FI-RAD) was measured using the Digital Vessel Analyser and expressed as percentage increase over baseline diameter. Static retinal photographs were acquired utilising a digital fundus camera for measurement of central retinal artery and vein equivalent (CRAE and CRVE), arteriovenous nicking (AVN) and focal arteriolar narrowing (FAN).

RESULTS

Intra-class correlation coefficient was 0.82 for flicker-light induced retinal arteriolar dilatation. There were modest associations in retinal vascular measurements between eyes. For each 10 μm decrease in retinal arteriolar diameter, the absolute increase in FI-RAD was 0.28% (95% CI 0.11, 0.45; p=0.002) independent of age, gender and atherosclerosis risk factors. AVN and FAN were associated with attenuated FI-RAD (β=-0.67%; 95% CI -1.20, -0.15; p=0.012) and (β=-0.83%; 95% CI -1.44, -0.23; p=0.007) respectively after adjustment for age and gender.

CONCLUSION

Assessment of retinal microvascular endothelial function is reproducible and correlated with retinal microvascular structure and signs, independent of atherosclerosis risk factors. Assessment of retinal vascular structure and function may provide insights into atherosclerotic disease.

Intratympanic dexamethasone on cochlear blood flow in Guinea pigs

To determine the effect of intratympanically delivered dexamethasone on cochlear blood flow. 29 white Hartly guinea pigs were divided into 2 groups. By laser Doppler flowmeter, baseline data were recorded in the first 15-20 min, followed by 20 min' recording after applying dexamethasone or normal saline, with a record of flow every 5 min in 2 groups. Friedman Test was used to test the change of blood flow in these four timing. There were no significant changes of blood flow after injecting dexamethasone (p = .18 > .05) and normal saline (p = .93 > .05). The effects of dexamethasone on cochlear blood flow were variable and not significant. The following research would be designed under pathological conditions, such as cochlear ischemia, to show the possible mechanism of dexamethasone for specific inner ear disease.

LEVEL OF EVIDENCE

3a (SR of case-control studies).

Microvascular network alterations in the retina of patients with Alzheimer's disease

BACKGROUND

Although cerebral small-vessel disease has been implicated in the development of Alzheimer's disease (AD), the cerebral microcirculation is difficult to visualize directly in vivo. Because the retina provides a noninvasive window to assess the microcirculation, we determined whether quantitatively measured retinal microvascular parameters are associated with AD.

METHODS

We conducted a case-control study (case:control matching ≈ 1:2). Retinal photographs were analyzed using a computer program, and a spectrum of quantitative retinal microvascular parameters (caliber, fractal dimension, tortuosity, and bifurcation) were measured. Logistic regression models were used to compute the odds ratio (OR) and 95% confidence interval for AD adjusting for age, gender, ethnicity, smoking, hypertension, diabetes, hypercholesterolemia, and history of myocardial infarction.

RESULTS

We included 136 demented patients with AD and 290 age-gender-race-matched controls. Persons with narrower venular caliber (OR per standard deviation [SD] decrease, 2.01 [1.27-3.19]), decreased arteriolar and venular fractal dimension (OR per SD decrease 1.35 [1.08-1.68], 1.47 [1.17-1.84], respectively) and increased arteriolar and venular tortuosity (OR per SD increase, 1.84 [1.40-2.31], 1.94 [1.48-2.53], respectively) were more likely to have AD. These associations still persisted when only AD cases without a history of cerebrovascular disease were included.

CONCLUSIONS

Patients with AD have altered microvascular network in the retina (narrower retinal venules and a sparser and more tortuous retinal vessels) compared with matched nondemented controls. These changes in retinal microvasculature may reflect similar pathophysiological processes in cerebral microvasculature in the brains of patients with AD.