Intravital fluorescence microscopy: impact of light-induced phototoxicity on adhesion of fluorescently labeled leukocytes

Peripheral microcirculation alteration as cause of posterosuperior rotator cuff tear: the possible indirect contribution of nailfold capillaroscopy

BACKGROUND

Most of the recent literature regarding rotator cuff tear etiology identifies in peripheral microcirculation disorders the probable main cause of tissue degeneration, and consequently of tendon rupture. Nailfold capillaroscopy is a practical and inexpensive diagnostic technique used to evaluate the health status of peripheral microcirculation, and recently, its use has found other indications in addition to that of diagnosing connective tissue diseases and Raynaud phenomenon. We verified the possible indirect contribution of nailfold capillaroscopy in the identification of peripheral microcirculation disturbances in a group of patients with rotator cuff tear and whether these possible alterations could be related to rotator cuff tear size.

MATERIALS AND METHODS

A case-control study was performed. One hundred patients (56 male, 44 female; mean age ± standard deviation [SD]: 60.46 ± 5.46 years) with different-sized posterosuperior cuff tears and 100 healthy controls (38 male, 62 female; mean age ± SD: 60.40 ± 6.34 years) were submitted to capillaroscopic examination. The following parameters were examined: capillary morphology and density, avascular areas, visibility of the subpapillary venous plexus, enlarged and giant capillaries, ectasias and microaneurysms, neoangiogenesis, hemosiderin deposits, pericapillary edema, and capillary blood flow. Severe exclusion criteria were applied. Statistical analysis was performed.

RESULTS

Visibility of subpapillary venous plexus (P < .001), pericapillary edema (P < .001), capillary blood flow (P < .001), ectasias and microaneurysms (P < .001), and neoangiogenesis (P = .04) were significantly associated with presence of a rotator cuff tear.

CONCLUSIONS

Our results support the hypothesis that microcirculation disorder has a relevant role in the genesis of cuff degeneration and, consequently, of tendon rupture. However, these alterations do not seem to be related to rotator cuff tear size.

Measuring the red blood cell shape in capillary flow using spectrally encoded flow cytometry

Red blood cells in small capillaries exhibit a wide variety of deformations that reflect their true physiological conditions at these important locations. By applying a technique for the high-speed microscopy of flowing cells, termed spectrally encoded flow cytometry (SEFC), we image the light reflected from the red blood cells in human capillaries, and propose an analytical slipper-like model for the cell morphology that can reproduce the experimental in vivo images. The results of this work would be useful for studying the unique flow conditions in these vessels, and for extracting useful clinical parameters that reflect the true physiology of the blood cells in situ.

The Secretive Life of Neutrophils Revealed by Intravital Microscopy

Neutrophils are the most abundant circulating leukocyte within the blood stream and for many years the dogma has been that these cells migrate rapidly into tissues in response to injury or infection, forming the first line of host defense. While it has previously been documented that neutrophils marginate within the vascular beds of the lung and liver and are present in large numbers within the parenchyma of tissues, such as spleen, lymph nodes, and bone marrow (BM), the function of these tissue resident neutrophils under homeostasis, in response to pathogen invasion or injury has only recently been explored, revealing the unexpected role of these cells as immunoregulators or immune helpers and also unraveling their heterogeneity and plasticity. Neutrophils are highly motile cells and the use of intravital microscopy (IVM) to image cells within their environment with little manipulation has dramatically increased our understanding of the function, migratory behavior, and interaction of these short-lived cells with other innate and adaptive immune cells. Contrary to previous dogma, these studies have shown that marginated and tissue resident neutrophils are the first responders to pathogens and injury, critical in limiting the spread of infection and contributing to the orchestration of the subsequent immune response. The interplay of neutrophils, with other neutrophils, leukocytes, and stroma cells can also modulate and tune their early and late response in order to eradicate pathogens, minimize tissue damage, and, in certain circumstances, contribute to tissue repair. In this review, we will follow the extraordinary journey of neutrophils from their origin in the BM to their death, exploring their role as tissue resident cells in the lung, spleen, lymph nodes, and skin and outlining the importance of neutrophil subsets, their functions under homeostasis, and in response to infection. Finally, we will comment on how understanding these processes in greater detail at a molecular level can lead to development of new therapeutics.

High-speed optical coherence tomography angiography for the measurement of stimulus-induced retrograde vasodilation of cerebral pial arteries in awake mice

Significance: Having a clear understanding of functional hyperemia is crucial for functional brain imaging and neurological disease research. Vasodilation induced by sensory stimulus propagates from the arterioles to the upstream pial arteries in a retrograde fashion. As retrograde vasodilation occurs briefly in the early stage of functional hyperemia, an imaging technique with a high temporal resolution is required for its measurement. Aim: We aimed to present an imaging method to measure stimulus-induced retrograde vasodilation in awake animals. Approach: An imaging method based on optical coherence tomography angiography, which enables a high-speed and label-free vessel diameter measurement, was developed and applied for the investigation. Results: The propagation speed of retrograde vasodilation of pial artery was measured in awake mice. Other characteristics of functional hyperemia such as temporal profile and amplitude of the vascular response were also investigated. Conclusions: Our results provide detailed information of stimulus-induced hemodynamic response in the brain of awake mice and suggest the potential utility of our imaging method for the study of functional hyperemia in normal and diseased brain.

Rapid and high-performance adsorptive removal of hazardous acridine orange from aqueous environment using Abelmoschus esculentus seed powder: Single- and multi-parameter optimization studies

In this research, the performance of naturally abundant lignocellulosic by-product, Abelmoschus esculentus, and its processed seed powder referred as AESP, as a potential biosorbent for the removal of acridine orange (AO) from the aqueous environment was examined. The AESP biosorbent was characterized by field emission scanning electron microscopy (FESEM), X-ray diffraction (XRD) analysis, diffuse reflectance spectroscopy (DRS), Fourier transform infrared (FTIR) and pH_ZPC analyses. The average size of the biosorbent according to particle size distribution analysis was found to be ∼132 μm. The batch adsorption experiments were conducted by altering the parameters such as contact time, solution pH, biosorbent dosage, initial dye concentration, stirring speed and temperature. Sorption of cationic AO dye onto AESP was found to be rapid, and the equilibrium condition reached within 30 min. The isotherms (Langmuir, Freundlich, Redlich-Peterson and Sips), kinetic models (pseudo-first order, pseudo-second order, Elovich, intra-particle diffusion, Bangham and modified-Freundlich models) and thermodynamic parameters were also evaluated. High values of determination coefficients (R²) and minimal values of non-linear error functions (i.e. HYBRD, RMSE, MPSD, ARE, APE and χ²) indicated that experimental data were best fitted with Sips isotherm and pseudo-second order kinetic model. Accordingly, the maximum loading capacity of AESP was found to be 259.4, 284.3 and 346.5 mg/g for the temperatures of 15, 30 and 45 °C, respectively. The thermodynamic parameters showed that the adsorption of AO onto the AESP surface was an endothermic and spontaneous process. Besides these, the central composite experimental design (CCD) superimposed with response surface methodology (RSM) modeling was also employed to investigate the effect of four significant parameters (solution pH, contact time, initial AO concentration and AESP dosage) and their interaction-term effects on the adsorption capacity of AESP and to formulate the mathematical model for the experimental data using multi-variate statistical analysis. Maximum dye uptake capacity under the optimum conditions of variables (pH 8.96, contact time 32.06 min, initial dye concentration 867.71 mg/L and AESP dosage 1.89 g/L) was 312.1 mg/g at temperature 30 °C, and it was found to be very close to the experimentally determined values (313.4 ± 0.057 mg/g). The promising reusability potential of AESP using 0.1 M HCl, implied that, the lignocellulosic biosorbent AESP might be helpful for the appropriate designing of the environmental-friendly purification systems.

Acridine orange adsorption by zinc oxide/almond shell activated carbon composite: Operational factors, mechanism and performance optimization using central composite design and surface modeling

Zinc Oxide/Activated Carbon Powder was used for the adsorptive removal of Acridine Orange dye (AO) from aqueous solution. The prepared composite material was characterized using XRD, XPS, SEM, EDS, FTIR, XRF, Raman, BET surface area and TGA/DTA. The adsorption isotherms, kinetics and thermodynamic studies of AO onto the ZnO-AC were thoroughly analyzed. The kinetic modeling data revealed that the adsorption of AO has a good adjustment to the pseudo-second-order model. Langmuir isotherm model is better fitted for adsorption data and the maximum adsorption capacity was found to be 909.1 mg/g at 313 K. The negative values of ΔG showed the spontaneous nature of the AO adsorption onto ZnO-AC. The results indicated the adsorption was pH dependent which is mainly governed by electrostatic attraction, hydrogen bonding and π-π interaction. Reusability test showed a low decrease in the removal performance of ZnO-AC due to the mesopore filling mechanism confirmed by BET analysis after adsorption. Also, thermal regeneration could deposit AO dye on the surface of the composite leading to the efficiency decrease. Finally, the effect of various parameters such as pH, temperature, contact time and initial dye concentration was studied using response surface methodology (RSM). The model predicted a maximum AO removal (99.42 ± 0.57%) under the optimum conditions, which was very close to the experimental value (99.32 ± 0.18%).

Just Look! Intravital Microscopy as the Best Means to Study Kidney Cell Death Dynamics

Kidney cell death plays a key role in the progression of life-threatening renal diseases, such as acute kidney injury and chronic kidney disease. Injured and dying epithelial and endothelial cells take part in complex communication with the innate immune system, which drives the progression of cell death and the decrease in renal function. To improve our understanding of kidney cell death dynamics and its impact on renal disease, a study approach is needed that facilitates the visualization of renal function and morphology in real time. Intravital multiphoton microscopy of the kidney has been used for more than a decade and made substantial contributions to our understanding of kidney physiology and pathophysiology. It is a unique tool that relates renal structure and function in a time- and spatial-dependent manner. Basic renal function, such as microvascular blood flow regulation and glomerular filtration, can be determined in real time and homeostatic alterations, which are linked inevitably to cell death and can be depicted down to the subcellular level. This review provides an overview of the available techniques to study kidney dysfunction and inflammation in terms of cell death in vivo, and addresses how this novel approach can be used to improve our understanding of cell death dynamics in renal disease.

Characterising live cell behaviour: Traditional label-free and quantitative phase imaging approaches

Label-free imaging uses inherent contrast mechanisms within cells to create image contrast without introducing dyes/labels, which may confound results. Quantitative phase imaging is label-free and offers higher content and contrast compared to traditional techniques. High-contrast images facilitate generation of individual cell metrics via more robust segmentation and tracking, enabling formation of a label-free dynamic phenotype describing cell-to-cell heterogeneity and temporal changes. Compared to population-level averages, individual cell-level dynamic phenotypes have greater power to differentiate between cellular responses to treatments, which has clinical relevance e.g. in the treatment of cancer. Furthermore, as the data is obtained label-free, the same cells can be used for further assays or expansion, of potential benefit for the fields of regenerative and personalised medicine.

A Comparison of Exogenous Labels for the Histological Identification of Transplanted Neural Stem Cells

The interpretation of cell transplantation experiments is often dependent on the presence of an exogenous label for the identification of implanted cells. The exogenous labels Hoechst 33342, 5-bromo-2'-deoxyuridine (BrdU), PKH26, and Qtracker were compared for their labeling efficiency, cellular effects, and reliability to identify a human neural stem cell (hNSC) line implanted intracerebrally into the rat brain. Hoechst 33342 (2 mg/ml) exhibited a delayed cytotoxicity that killed all cells within 7 days. This label was hence not progressed to in vivo studies. PKH26 (5 μM), Qtracker (15 nM), and BrdU (0.2 μM) labeled 100% of the cell population at day 1, although BrdU labeling declined by day 7. BrdU and Qtracker exerted effects on proliferation and differentiation. PKH26 reduced viability and proliferation at day 1, but this normalized by day 7. In an in vitro coculture assay, all labels transferred to unlabeled cells. After transplantation, the reliability of exogenous labels was assessed against the gold standard of a human-specific nuclear antigen (HNA) antibody. BrdU, PKH26, and Qtracker resulted in a very small proportion (<2%) of false positives, but a significant amount of false negatives (∼30%), with little change between 1 and 7 days. Exogenous labels can therefore be reliable to identify transplanted cells without exerting major cellular effects, but validation is required. The interpretation of cell transplantation experiments should be presented in the context of the label's limitations.

Win 55212-2, a cannabinoid receptor agonist, attenuates leukocyte/endothelial interactions in an experimental autoimmune encephalomyelitis model

Multiple sclerosis (MS) is the most common of the immune demyelinating disorders of the central nervous system (C NS). Leukocyte/endothelial interactions are important steps in the progression of the disease and substances that interfere with these activities have been evaluated as potential therapeutic agents. C annabinoid receptor agonists have been shown to downregulate immune responses and there is preliminary evidence that they may slow the progress of MS. The purpo se of this investigation was to determine how cannabinoid recepto r agonists interfere with leukocyte rolling and adhesion. This was investigated in an experimental autoimmune encephalo myelitis (EAE) model using six to eight week old C 57BL/6 mice. Mouse myelin oligodendrocyte protein and pertussis toxin were used to induce EAE. WIN 55212-2, C B1 and C B2 antagonist were given. By use of in vivo intravital microscopy, leukocyte/endothelial interactio ns were evaluated via a cranial window implanted two days before. The results demonstrated that EAE increases leukocyte rolling and firm adhesion in the brain, and that this increased leukocyte/endothelial interactio n can be attenuated by administration of WIN 55212-2. Furthermore, use of the selective antagonists for the C B1 recepto r (SR 141716A) and the C B2 receptor (SR144528) in this study demonstrated that the cannabinoid’s inhibitory effects on leukocyte/endothelial interactions can be mediated by activating C B2 receptor.

Enhanced fluorescence emitted by microdroplets containing organic dye emulsions

In this paper, laser beam resonant interaction with pendant microdroplets that are seeded with a laser dye (Rhodamine 6G (Rh6G)) water solution or oily Vitamin A emulsion with Rhodamine 6G solution in water is investigated through fluorescence spectra analysis. The excitation is made with the second harmonic generated beam emitted by a pulsed Nd:YAG laser system at 532 nm. The pendant microdroplets containing emulsion exhibit an enhanced fluorescence signal. This effect can be explained as being due to the scattering of light by the sub-micrometric drops of oily Vitamin A in emulsion and by the spherical geometry of the pendant droplet. The droplet acts as an optical resonator amplifying the fluorescence signal with the possibility of producing lasing effect. Here, we also investigate how Rhodamine 6G concentration, pumping laser beam energies and number of pumping laser pulses influence the fluorescence behavior. The results can be useful in optical imaging, since they can lead to the use of smaller quantities of fluorescent dyes to obtain results with the same quality.

Molecular mechanisms of curcumin on diabetes-induced endothelial dysfunctions: Txnip, ICAM-1, and NOX2 expressions

We aim to investigate the effects of curcumin on preventing diabetes-induced vascular inflammation in association with its actions on Txnip, ICAM-1, and NOX2 enzyme expressions. Male Wistar rats were divided into four groups: control (CON), diabetic (DM; streptozotocin (STZ), i.v. 55 mg/kg BW), control-treated with curcumin (CONCUR; 300 mg/kg BW), and diabetes treated with curcumin (DMCUR; 300 mg/kg BW). 12th week after STZ injection, iris blood perfusion, leukocyte adhesion, Txnip, p47phox, and malondialdehyde (MDA) levels were determined by using laser Doppler, intravital fluorescent confocal microscopy, Western Blot analysis, and TBAR assay, respectively. The iris blood perfusion of DM and DMCUR was decreased significantly compared to CON and CONCUR (P < 0.001). Plasma glucose and HbA1c of DM and DMCUR were increased significantly compared to CON and CONCUR (P < 0.001). Leukocyte adhesion, ICAM-1, p47phox expression, and MDA levels in DM were increased significantly compared to CON, CONCUR, and DMCUR (P < 0.05). Txnip expression in DM and DMCUR was significantly higher than CON and CONCUR (P < 0.05). From Pearson's analysis, the correlation between the plasma MDA level and the endothelial functions was significant. It suggested that curcumin could ameliorate diabetic vascular inflammation by decreasing ROS overproduction, reducing leukocyte-endothelium interaction, and inhibiting ICAM-1 and NOX2 expression.

Comparison of indocyanine green angiography and laser speckle contrast imaging for the assessment of vasculature perfusion

BACKGROUND

Assessment of the vasculature is critical for overall success in cranial vascular neurological surgery procedures. Although several methods of monitoring cortical perfusion intraoperatively are available, not all are appropriate or convenient in a surgical environment. Recently, 2 optical methods of care have emerged that are able to obtain high spatial resolution images with easily implemented instrumentation: indocyanine green (ICG) angiography and laser speckle contrast imaging (LSCI).

OBJECTIVE

To evaluate the usefulness of ICG and LSCI in measuring vessel perfusion.

METHODS

An experimental setup was developed that simultaneously collects measurements of ICG fluorescence and LSCI in a rodent model. A 785-nm laser diode was used for both excitation of the ICG dye and the LSCI illumination. A photothrombotic clot model was used to occlude specific vessels within the field of view to enable comparison of the 2 methods for monitoring vessel perfusion.

RESULTS

The induced blood flow change demonstrated that ICG is an excellent method for visualizing the volume and type of vessel at a single point in time; however, it is not always an accurate representation of blood flow. In contrast, LSCI provides a continuous and accurate measurement of blood flow changes without the need of an external contrast agent.

CONCLUSION

These 2 methods should be used together to obtain a complete understanding of tissue perfusion.

Intravital immunofluorescence for visualizing the microcirculatory and immune microenvironments in the mouse ear dermis

Visualizing the dynamic behaviors of immune cells in living tissue has dramatically increased our understanding of how cells interact with their surroundings, contributing important insights into mechanisms of leukocyte trafficking, tumor cell invasion, and T cell education by dendritic cells, among others. Despite substantial advances with various intravital imaging techniques including two-photon microscopy and the generation of multitudes of reporter mice, there is a growing need to assess cell interactions in the context of specific extracellular matrix composition and microvascular functions, and as well, simpler and more widely accessible methods are needed to image cell behaviors in the context of living tissue physiology. Here we present an antibody-based method for intravital imaging of cell interactions with the blood, lymphatic, and the extracellular matrix compartments of the living dermis while simultaneously assessing capillary permeability and lymphatic drainage function. Using the exposed dorsal ear of the anesthetized mouse and a fluorescence stereomicroscope, such events can be imaged in the context of specific extracellular matrix proteins, or matrix-bound chemokine stores. We developed and optimized the method to minimize tissue damage to the ear, rapidly immunostain for multiple extracellular or cell surface receptors of interest, minimize immunotoxicity with pre-blocking Fcγ receptors and phototoxicity with extracellular antioxidants, and highlight the major dermal tissue structures with basement membrane markers. We demonstrate differential migration behaviors of bone marrow-derived dendritic cells, blood-circulating leukocytes, and dermal dendritic cells, with the latter entering sparse CCL21-positive areas of pre-collecting lymphatic vessels. This new method allows simultaneous imaging of cells and tissue structures, microvascular function, and extracellular microenvironment in multiple skin locations for 12 hours or more, with the flexibility of immunolabeling in addition to genetic-based fluorescent reporters.

Molecular imaging of retinal disease

Imaging of the eye plays an important role in ocular therapeutic discovery and evaluation in preclinical models and patients. Advances in ophthalmic imaging instrumentation have enabled visualization of the retina at an unprecedented resolution. These developments have contributed toward early detection of the disease, monitoring of disease progression, and assessment of the therapeutic response. These powerful technologies are being further harnessed for clinical applications by configuring instrumentation to detect disease biomarkers in the retina. These biomarkers can be detected either by measuring the intrinsic imaging contrast in tissue, or by the engineering of targeted injectable contrast agents for imaging of the retina at the cellular and molecular level. Such approaches have promise in providing a window on dynamic disease processes in the retina such as inflammation and apoptosis, enabling translation of biomarkers identified in preclinical and clinical studies into useful diagnostic targets. We discuss recently reported and emerging imaging strategies for visualizing diverse cell types and molecular mediators of the retina in vivo during health and disease, and the potential for clinical translation of these approaches.

Photothermal confocal spectromicroscopy of multiple cellular chromophores and fluorophores

Confocal fluorescence microscopy is a powerful biological tool providing high-resolution, three-dimensional (3D) imaging of fluorescent molecules. Many cellular components are weakly fluorescent, however, and thus their imaging requires additional labeling. As an alternative, label-free imaging can be performed by photothermal (PT) microscopy (PTM), based on nonradiative relaxation of absorbed energy into heat. Previously, little progress has been made in PT spectral identification of cellular chromophores at the 3D microscopic scale. Here, we introduce PTM integrating confocal thermal-lens scanning schematic, time-resolved detection, PT spectral identification, and nonlinear nanobubble-induced signal amplification with a tunable pulsed nanosecond laser. The capabilities of this confocal PTM were demonstrated for high-resolution 3D imaging and spectral identification of up to four chromophores and fluorophores in live cells and Caenorhabditis elegans. Examples include cytochrome c, green fluorescent protein, Mito-Tracker Red, Alexa-488, and natural drug-enhanced or genetically engineered melanin as a PT contrast agent. PTM was able to guide spectral burning of strong absorption background, which masked weakly absorbing chromophores (e.g., cytochromes in the melanin background). PTM provided label-free monitoring of stress-related changes to cytochrome c distribution, in C. elegans at the single-cell level. In nonlinear mode ultrasharp PT spectra from cyt c and the lateral resolution of 120 nm during calibration with 10-nm gold film were observed, suggesting a potential of PTM to break through the spectral and diffraction limits, respectively. Confocal PT spectromicroscopy could provide a valuable alternative or supplement to fluorescence microscopy for imaging of nonfluorescent chromophores and certain fluorophores.

A quantitative method for measuring phototoxicity of a live cell imaging microscope

Fluorescence-based imaging regimes require exposure of living samples under study to high intensities of focused incident illumination. An often underestimated, overlooked, or simply ignored fact in the design of any experimental imaging protocol is that exposure of the specimen to these excitation light sources must itself always be considered a potential source of phototoxicity. This can be problematic, not just in terms of cell viability, but much more worrisome in its more subtle manifestation where phototoxicity causes anomalous behaviors that risk to be interpreted as significant, whereas they are mere artifacts. This is especially true in the case of microbial pathogenesis, where host-pathogen interactions can prove especially fragile to light exposure in a manner that can obscure the very processes we are trying to observe. For these reasons, it is important to be able to bring the parameter of phototoxicity into the equation that brings us to choose one fluorescent imaging modality, or setup, over another. Further, we need to be able to assess the risk that phototoxicity may occur during any specific imaging experiment. To achieve this, we describe here a methodological approach that allows meaningful measurement, and therefore relative comparison of phototoxicity, in most any variety of different imaging microscopes. In short, we propose a quantitative approach that uses microorganisms themselves to reveal the range over which any given fluorescent imaging microscope will yield valid results, providing a metrology of phototoxic damage, distinct from photobleaching, where a clear threshold for phototoxicity is identified. Our method is widely applicable and we show that it can be adapted to other paradigms, including mammalian cell models.

Techniques to assess tissue oxygenation in the clinical setting

The microcirculation plays an essential role in health and disease. Microvascular perfusion can be assessed directly using laser Doppler flowmetry and various imaging techniques or indirectly using regional capnometry and measurement of indicators of mismatch between oxygen delivery and oxygen consumption or indices of disturbed cellular oxygen utilization. Assessment of microvascular oxygen availability implies measurement of oxygen pressure or measurement of hemoglobin oxygen saturation. Microvascular function is assessed using other methods, including venous plethysmography. In this paper, I review current knowledge concerning assessment of the microcirculation with special emphasis on methods that could be used at the bedside.

Nanotechnology-based molecular photoacoustic and photothermal flow cytometry platform for in-vivo detection and killing of circulating cancer stem cells

In-vivo multicolor photoacoustic (PA) flow cytometry for ultrasensitive molecular detection of the CD44+ circulating tumor cells (CTCs) is demonstrated on a mouse model of human breast cancer. Targeting of CTCs with stem-like phenotype, which are naturally shed from parent tumors, was performed with functionalized gold and magnetic nanoparticles. Results in vivo were verified in vitro with a multifunctional microscope, which integrates PA, photothermal (PT), fluorescent and transmission modules. Magnet-induced clustering of magnetic nanoparticles in individual cells significantly amplified PT and PA signals. The novel noninvasive platform, which integrates multispectral PA detection and PT therapy with a potential for multiplex targeting of many cancer biomarkers using multicolor nanoparticles, may prospectively solve grand challenges in cancer research for diagnosis and purging of undetectable yet tumor-initiating cells in circulation before they form metastasis.

Removal and recovery of acridine orange from solutions by use of magnetic nanoparticles

Here we report a separation of a cationic dye, acridine orange (AO), by use of magnetic nanoparticles (gamma-Fe(2)O(3)). The particles were showed to capture 98% of the dye within the first 20 min of contact time. The maximum sorption capacity of the magnetic nanoparticles (MNPs) for AO was 59mg/g. The sorption isotherms fit well with the Freundlich model. The sorption kinetics fits well the pseudo-second-order rate equation model. 60-90% dye recovery was achieved by rotary evaporating the dye bearing nanoparticles in acetone. The nanoparticles were recycled for additional dye removal.

Intravital microscopy of tumor angiogenesis and regression in the dorsal skin fold chamber: mechanistic insights and preclinical testing of therapeutic strategies

Tumor angiogenesis is a major step in tumor progression to clinically symptomatic cancer and thus a potential target for cancer therapy. It is essential to understand the fundamental mechanisms of the angiogenic processes to provide a rational for testing inhibitory strategies for cancer treatment. The dorsal skin fold chamber provides a suitable (chronic) model for intravital microscopy to monitor the same tumor in time-lapse imaging series and in real-time functional analysis e.g., of blood flow. Adaptation of this model to several rodent species and tumor types has led to numerous physical and drug based therapy options. With modification of implantation techniques, motility and invasion of individual cells can be visualized, in addition to angiogenesis and microcirculation. Modern fluorescent techniques such as ex vivo labelling of specific cell populations and the introduction of stably fluorescent protein expressing cell lines further enhance the suitability of this technique. In addition, laser scanning and multiphoton microscopy in combination with genetically altered mouse strains and cell lines are making the DCSF even more attractive for mechanistic and interventional studies in cancer research. Here we review the preparation as well as the applications of the DCSF in tumor angiogenesis.

In vivo multispectral, multiparameter, photoacoustic lymph flow cytometry with natural cell focusing, label-free detection and multicolor nanoparticle probes

Compared with blood tests, cell assessment in lymphatics is not well-established. The goal of this work was to develop in vivo lymph tests using the principles of flow cytometry. Cells in living animals were counted by laser (420-2,300 nm) generation of photoacoustic (PA) signals in individual cells hydrodynamically focused by lymph valves into a single file flow, and using endogenous absorption as intrinsic cell-specific markers, or gold nanorods, nanoshells, and carbon nanotubes as multicolor probes. PA data were verified by high-speed transmission, photothermal, and fluorescent imaging. Counting of melanoma and immune-related cells in normal, apoptotic, and necrotic states in lymphatics in vivo was demonstrated to have the unprecedented sensitivity as one metastatic cell among millions of white blood cells. The time-resolved PA spectral identification of flowing cells was achieved using multicolor labels and laser pulses of different wavelengths and time delays. Multiparameter, noninvasive, portable flow cytometer can be used for preclinical studies on animals with the potential of translation to humans for in vivo PA mapping of colorless lymph vessels and sentinel nodes with simultaneous single cell detection and metastasis assessment without labeling or use of contrast dyes and/or novel low-toxic multicolor probes with different absorption spectra.

Measurement of blood flow in the rotator cuff using laser Doppler flowmetry

The aim of this study was to define the microcirculation of the normal rotator cuff during arthroscopic surgery and investigate whether it is altered in diseased cuff tissue. Blood flow was measured intra-operatively by laser Doppler flowmetry. We investigated six different zones of each rotator cuff during the arthroscopic examination of 56 consecutive patients undergoing investigation for impingement, cuff tears or instability; there were 336 measurements overall. The mean laser Doppler flowmetry flux was significantly higher at the edges of the tear in torn cuffs (43.1, 95% confidence interval (CI) 37.8 to 48.4) compared with normal cuffs (32.8, 95% CI 27.4 to 38.1; p = 0.0089). It was significantly lower across all anatomical locations in cuffs with impingement (25.4, 95% CI 22.4 to 28.5) compared with normal cuffs (p = 0.0196), and significantly lower in cuffs with impingement compared with torn cuffs (p < 0.0001). Laser Doppler flowmetry analysis of the rotator cuff blood supply indicated a significant difference between the vascularity of the normal and the pathological rotator cuff. We were unable to demonstrate a functional hypoperfusion area or so-called 'critical zone' in the normal cuff. The measured flux decreases with advancing impingement, but there is a substantial increase at the edges of rotator cuff tears. This might reflect an attempt at repair.

Intravital imaging of CD8+ T cell function in cancer

Recent technological advances in photonics are making intravital microscopy (IVM) an increasingly powerful approach for the mechanistic exploration of biological processes in the physiological context of complex native tissue environments. Direct, dynamic and multiparametric visualization of immune cell behavior in living animals at cellular and subcellular resolution has already proved its utility in auditing basic immunological concepts established through conventional approaches and has also generated new hypotheses that can conversely be complemented and refined by traditional experimental methods. The insight that outgrowing tumors must not necessarily have evaded recognition by the adaptive immune system, but can escape rejection by actively inducing a state of immunological tolerance calls for a detailed investigation of the cellular and molecular mechanisms by which the anti-cancer response is subverted. Along with molecular imaging techniques that provide dynamic information at the population level, IVM can be expected to make a critical contribution to this effort by allowing the observation of immune cell behavior in vivo at single cell-resolution. We review here how IVM-based investigation can help to clarify the role of cytotoxic T lymphocytes (CTL) in the immune response against cancer and identify the ways by which their function might be impaired through tolerogenic mechanisms.

Impact of cold preservation on leukocyte adhesion to the transplanted rat lung

Little is known about leukocyte migration in the early phase after ischemia-reperfusion injury. Recently, there has been much focus on in vivo visualization of cell kinetics. Previously, we established a method for the in vivo visualization of leukocyte circulation using a Green Fluorescent Protein transgenic rat. Herein, we developed a simplified rat heterotopic lung transplantation model that can be mastered by beginners within a few weeks. Using this system, we studied the impact of preservation on adhesion of circulating leukocytes to the transplanted lung. The graft of a fresh group was compared with that of a preserved group. Morphological and immunohistochemical analyses were also performed. We successfully visualized few adherent leukocytes in the fresh graft, whereas adherent cells were attached in the preserved graft within a few minutes. In conclusion, the prolonged cold preservation time promotes leukocyte adhesion, resulting in increased microvascular injury after lung transplantation.

Cannabinoid CB(2) receptor activation decreases cerebral infarction in a mouse focal ischemia/reperfusion model

Cannabinoid CB(2) Receptor (CB(2)) activation has been shown to have immunomodulatory properties without psychotropic effects. The hypothesis of this study is that selective CB(2) agonist treatment can attenuate cerebral ischemia/reperfusion injury. Selective CB(2) agonists (O-3853, O-1966) were administered intravenously 1 h before transient middle cerebral artery occlusion (MCAO) or 10 mins after reperfusion in male mice. Leukocyte/endothelial interactions were evaluated before MCAO, 1 h after MCAO, and 24 h after MCAO via a closed cranial window. Cerebral infarct volume and motor function were determined 24 h after MCAO. Administration of the selective CB(2) agonists significantly decreased cerebral infarction (30%) and improved motor function (P<0.05) after 1 h MCAO followed by 23 h reperfusion in mice. Transient ischemia in untreated animals was associated with a significant increase in leukocyte rolling and adhesion on both venules and arterioles (P<0.05), whereas the enhanced rolling and adhesion were attenuated by both selective CB(2) agonists administered either at 1 h before or after MCAO (P<0.05). CB(2) activation is associated with a reduction in white blood cell rolling and adhesion along cerebral vascular endothelial cells, a reduction in infarct size, and improved motor function after transient focal ischemia.

Advances in small animal mesentery models for in vivo flow cytometry, dynamic microscopy, and drug screening

Using animal mesentery with intravital optical microscopy is a well-established experimental model for studying blood and lymph microcirculation in vivo. Recent advances in cell biology and optical techniques provide the basis for extending this model for new applications, which should generate significantly improved experimental data. This review summarizes the achievements in this specific area, including in vivo label-free blood and lymph photothermal flow cytometry, super-sensitive fluorescence image cytometry, light scattering and speckle flow cytometry, microvessel dynamic microscopy, infrared (IR) angiography, and high-speed imaging of individual cells in fast flow. The capabilities of these techniques, using the rat mesentery model, were demonstrated in various studies; e.g., real-time quantitative detection of circulating and migrating individual blood and cancer cells, studies on vascular dynamics with a focus on lymphatics under normal conditions and under different interventions (e.g. lasers, drugs, nicotine), assessment of lymphatic disturbances from experimental lymphedema, monitoring cell traffic between blood and lymph systems, and high-speed imaging of cell transient deformability in flow. In particular, the obtained results demonstrated that individual cell transportation in living organisms depends on cell type (e.g., normal blood or leukemic cells), the cell’s functional state (e.g., live, apoptotic, or necrotic), and the functional status of the organism. Possible future applications, including in vivo early diagnosis and prevention of disease, monitoring immune response and apoptosis, chemo- and radio-sensitivity tests, and drug screening, are also discussed.

Optical and fluorescence detection of neutrophil integrin activation

Neutrophils are among the first cells to respond to acute inflammation through a multistep process initiated by selectin mediated rolling, which transitions to an integrin/intercellular adhesion molecule-dependent arrest and transmigration across endothelium. A conformational shift in the CD11/CD18 adhesion receptor on neutrophils is a critical determinant of the efficiency of recruitment on inflamed endothelium. For instance, beta2-integrin expression level is upregulated up to 10-fold by fusion of cytoplasmic granule pools of CD11b/CD18 (Mac-1). Furthermore, a rapid increase in affinity and membrane clustering of CD11a/CD18 (LFA-1) is necessary for efficient deceleration and arrest in shear flow. We present methods here to quantify the changes in receptor expression and affinity that support neutrophil adhesive phenotypes. Techniques involving real-time fluorescence flow cytometry and parallel plate rheometry coupled with light microscopy are presented.

Prolonged superficial local cryotherapy attenuates microcirculatory impairment, regional inflammation, and muscle necrosis after closed soft tissue injury in rats

BACKGROUND

Closed soft tissue injury induces progressive microvascular dysfunction and regional inflammation. The authors tested the hypothesis that adverse trauma-induced effects can be reduced by local cooling. While superficial cooling reduces swelling, pain, and cellular oxygen demand, the effects of cryotherapy on posttraumatic microcirculation are incompletely understood.

STUDY DESIGN

Controlled laboratory study.

METHODS

After a standardized closed soft tissue injury to the left tibial compartment, male rats were randomly subjected to percutaneous perfusion for 6 hours with 0.9% NaCL (controls; room temperature) or cold NaCL (cryotherapy; 8 degrees C) (n = 7 per group). Uninjured rats served as shams (n = 7). Microcirculatory changes and leukocyte adherence were determined by intravital microscopy. Intramuscular pressure was measured, and invasion of granulocytes and macrophages was assessed by immunohistochemistry. Edema and tissue damage was quantified by gravimetry and decreased desmin staining.

RESULTS

Closed soft tissue injury significantly decreased functional capillary density (240 +/- 12 cm(-1)); increased microvascular permeability (0.75 +/- 0.03), endothelial leukocyte adherence (995 +/- 77/cm(2)), granulocyte (182.0 +/- 25.5/mm(2)) and macrophage infiltration, edema formation, and myonecrosis (ratio: 2.95 +/- 0.45) within the left extensor digitorum longus muscle. Cryotherapy for 6 hours significantly restored diminished functional capillary density (393 +/- 35), markedly decreased elevated intramuscular pressure, reduced the number of adhering (462 +/- 188/cm(2)) and invading granulocytes (119 +/- 28), and attenuated tissue damage (ratio: 1.7 +/- 0.17).

CONCLUSION

The hypothesis that prolonged cooling reduces posttraumatic microvascular dysfunction, inflammation, and structural impairment was confirmed.

CLINICAL RELEVANCE

These results may have therapeutic implications as cryotherapy after closed soft tissue injury is a valuable therapeutic approach to improve nutritive perfusion and attenuate leukocyte-mediated tissue destruction. The risk for evolving compartment syndrome may be reduced, thereby preventing further irreversible aggravation.

Virtual biopsy of the joint tissues using near-infrared, reflectance confocal microscopy. A pilot study

Standard noninvasive imaging techniques applied to joints provide gross morphological features, insufficient for assessing histological detail. On the other hand, biopsying is invasive, time consuming, and may involve unwanted processing artifacts. Near-infrared reflectance confocal microscopy is a technique that allows serial, high-resolution optical sectioning through intact tissues without employing exogenous fluorescent stains. The aim of this work was to evaluate the potential utility of near-infrared reflectance confocal microscopy for providing immediate histological information on meniscus, articular cartilage, epiphyseal plate, bone, muscle, and tendon. Images from near-infrared reflectance confocal microscopy were compared with mirror routine histology sections. Characteristic architectural features were readily visualized in the three dimensions of space. Additionally, the use of experimental contrast agents highlighted the localization of nuclei. Limitations include penetration depth and minor optical artifacts. In conclusion, near-infrared reflectance confocal microscopy is a useful technique for immediate, nondestructive, serial "virtual" sectioning through intact tissues, being thus a potential adjunct to current imaging techniques in orthopedics.

Phototoxicity and fluorotoxicity combine to alter the behavior of neutrophils in fluorescence microscopy based flow adhesion assays

The use of fluorescent probes that allow visualization of leukocyte-endothelial cell (EC) interactions has greatly informed our understanding of leukocyte recruitment. However, effects of these agents on the biological functions of leukocytes are poorly described, leading to concerns about the interpretation of such data. Here we used two flow-based neutrophil adhesion assays to compare the effects of phase contrast illumination (PCI) with high intensity illumination (HII) used for fluorescent microscopy, in the presence or absence of five commonly used fluorochromes. Isolated neutrophils were either (1) perfused across P-selectin to establish a population of rolling cells, which were subsequently activated with fMLP; or (2) perfused across EC activated with TNF-alpha. In the absence of fluorescent dyes, HII did not affect levels of leukocyte adhesion; however, subsequent neutrophil behavior was dramatically altered when compared with cells under PCI, for example, dramatically reducing their migration velocities. In the presence of fluorescent dyes, the effects of HII were exacerbated, although the precise nature of the biological effects of these probes was agent specific. Thus, for the first time, our experiments describe the effects of fluorescent microscopy on the separate stages of the neutrophil recruitment process and reveal a previously unsuspected effect of HII on neutrophil migration.

Local cooling restores microcirculatory hemodynamics after closed soft-tissue trauma in rats

BACKGROUND

Severe closed soft-tissue injury (CSTI) results in progressively developing microvascular dysfunction and local inflammation. Cooling reduces swelling, pain, cellular oxygen demand, and metabolic activity. However, effects of cooling on posttraumatic microcirculation are not yet fully understood. Thus, we assessed effects of local cooling on microcirculation, regional inflammatory response including leukocyte-endothelial cell interaction, and edema formation after CSTI.

METHODS

Standardized CSTI was induced by means of controlled impact injury in the left tibial compartment of 14 male Sprague-Dawley rats. Rats were assigned to four groups (n = 7 per group) as follows: group I, no trauma/no cooling; group II, no trauma/20 minutes of cooling; group III, 1.5 hours posttrauma/no cooling; and group IV, 1.5 hours posttrauma/20 minutes of cooling.

RESULTS

CSTI resulted in a significant decrease in functional capillary density, a marked increase in microvascular permeability, and granulocyte infiltration (HIS48) as revealed by intravital microscopy and immunohistochemistry of the left extensor digitorum longus muscle. After 20 minutes of local cooling, these microvascular derangements were restored to the level of controls (group I). Edema (extensor digitorum longus muscle wet-to-dry weight ratio) was less pronounced compared with noncooling conditions (group III). Immunoreactivity for HIS48 (neutrophilic granulocytes) in injured rats subjected to local cooling (group IV) was markedly decreased compared with noncooling conditions (group III).

CONCLUSION

These results provide in vivo evidence that cooling affords protection of posttraumatic microcirculation through sustained inhibition of microvascular and endothelial dysfunction leading to less granulocyte-dependent inflammation and skeletal muscle edema. Local cooling appears to reduce propagation of acute microvascular injury, preventing leukocyte-dependent tissue destruction and escalation of secondary tissue damage after musculoskeletal soft-tissue trauma.

In vivo imaging of lymphocyte trafficking

Over the past decades, intravital microscopy (IVM), the imaging of cells in living organisms, has become a valuable tool for studying the molecular determinants of lymphocyte trafficking. Recent advances in microscopy now make it possible to image cell migration and cell-cell interactions in vivo deep within intact tissues. Here, we summarize the principal techniques that are currently used in IVM, discuss options and tools for fluorescence-based visualization of lymphocytes in microvessels and tissues, and describe IVM models used to explore lymphoid and non-lymphoid organs. The latter will be introduced according to the physiologic itinerary of developing and differentiating T and B lymphocytes as they traffic through the body, beginning with their development in bone marrow and thymus and continuing with their migration to secondary lymphoid organs and peripheral tissues.

Tissue engineered cartilage integration to live and devitalized cartilage: a study by reflectance mode confocal microscopy and standard histology

This study investigated the in vivo formation of engineering cartilage within living or devitalized cartilage discs using reflectance mode confocal microscopy and conventional light microscopy. Pig articular chondrocytes were suspended in fibrin glue and placed between two cartilage discs. Four experimental groups were prepared: in groups 1 and 2, the cell-hydrogel composite was placed between two live or between two devitalized cartilage discs, respectively; in groups 3 and 4, acellular fibrin glue was placed between two live or between two devitalized cartilage discs, respectively. Samples were implanted in the back of nude mice and analyzed after 2, 5, and 8 weeks. Results showed that engineered cartilage seems to grow more homogenously when the cell-seeded gel was placed between devitalized cartilages than when it was placed between live cartilage matrices. Confocal microscopy provides valuable information on the integration of tissue-engineered cartilage with native tissue and could be useful for nondestructive imaging in vivo.

Paradoxical attenuation of leukocyte rolling in response to ischemia- reperfusion and extracorporeal blood circulation in inflamed tissue

In contrast to acute preparations such as the exteriorized mesentery or the cremaster muscle, chronically instrumented chamber models allow one to study the microcirculation under “physiological” conditions, i.e., in the absence of trauma-induced leukocyte rolling along the venular endothelium. To underscore the importance of studying the naive microcirculation, we implanted titanium dorsal skinfold chambers in hamsters and used intravital fluorescence microscopy to study venular leukocyte rolling in response to ischemia-reperfusion injury or extracorporeal blood circulation. The experiments were performed in chambers that fulfilled all well-established criteria for a physiological microcirculation as well as in chambers that showed various extents of leukocyte rolling due to trauma, hemorrhage, or inflammation. In ideal chambers with a physiological microcirculation (<30 rolling leukocytes/mm vessel circumference in 30 s), ischemia-reperfusion injury and extracorporeal blood circulation significantly stimulated leukocyte rolling along the venular endothelium and, subsequently, firm leukocyte adhesion. In contrast, both stimuli failed to elicit leukocyte rolling in borderline chambers (30–100 leukocytes/mm), and in blatantly inflamed chambers with yet higher numbers of rolling leukocytes at baseline (>100 leukocytes/mm), we observed a paradoxical reduction of leukocyte rolling after ischemia-reperfusion injury or extracorporeal blood circulation. A similar effect was observed when we superfused leukotriene B4 (LTB4) onto the chamber tissue. The initial increase in leukocyte rolling in response to an LTB4 challenge was reversed by a second superfusion 90 min later. These observations underscore 1) the benefit of studying leukocyte-endothelial cell interaction in chronically instrumented chamber models and 2) the necessity to strictly adhere to well-established criteria of a physiological microcirculation.

Pancreatic proteases in serum induce leukocyte-endothelial adhesion and pancreatic microcirculatory failure

BACKGROUND

Neutrophil-mediated tissue injury in acute pancreatitis includes a severe reduction of the functional microcirculation via interaction of adhesion molecules on leukocytes (MAC-1) and endothelium (ICAM-1). The hypothesis of the study was that trypsin and elastase in serum alone lead to the expression of these complementary adhesion molecules and result in increased leukocyte-endothelial interaction (LEI). In addition we evaluated the preventative benefit of protease inhibition on these mechanisms.

MATERIALS AND METHODS

In vitro: Cultured endothelial cells (HUVEC) and human leukocytes (PMN) were stimulated with increasing doses of trypsin and elastase. In addition, pre-treatment of PMN or HUVEC was performed with protease inhibitors (Nafamostat mesilate, FUT and gabexate mesilate, FOY). The expression of ICAM-1 or MAC-1 was evaluated by flow cytometry. In vivo: Severe pancreatitis was induced in rats. Microcirculatory disturbances were evaluated by real-time confocal microscopy at 9 h in controls and acute pancreatitis with or without anti-protease treatment. Additionally, the effect of continuous trypsin and elastase infusion on pancreatic microcirculation and LEI were evaluated by intravital fluorescence videomicroscopy.

RESULTS

Up-regulation of MAC-1 and ICAM-1 expression requires the presence of serum. The maximal increase of MAC-1 and ICAM-1 expression was found at concentrations of trypsin or elastase characteristic for acute pancreatitis. FUT or FOY significantly reduced protease-induced expression of MAC-1 and ICAM-1. Real-time in-vivo microscopy revealed that functional capillary density in acute pancreatitis was significantly reduced (267.1 +/- 2.95/mm2 vs. 91.29 +/- 12.81/mm2) and treatment with FUT significantly reduced this effect (134.6 +/- 4.6/mm2; p < 0.05 vs. untreated pancreatitis). Infusion of trypsin or elastase alone increased LEI in vivo and reduced pancreatic perfusion.

CONCLUSION

Both trypsin and elastase up-regulate the expression of adhesion molecules on leukocytes and endothelial cells in the presence of serum. Increased LEI and reduced perfusion of the pancreas, characteristic of acute pancreatitis, is induced in vivo by infusion of pancreatic proteases and this effect is partially abrogated by their inhibitors. These results support the role of circulating trypsin and elastase in promoting pancreatic microcirculatory failure in experimental acute pancreatitis.

In vivo imaging of leukocyte trafficking in blood vessels and tissues

Selective recruitment of blood-borne leukocytes to tissues and their proper positioning within them is crucial for the many integrated functions of the immune system. Intravital microscopy (IVM) techniques have been employed for more than a century to study these events at the single-cell level in living animals. Conventional video-based IVM allows the visualization of extremely rapid adhesion events at the interface between blood and tissue. Multiphoton IVM is a relatively new tool for imaging the slower dynamics of cell migration and cell-cell interactions in the extravascular space in three dimensions. Fueled by the burgeoning development of sophisticated fluorescent markers and increasingly powerful imaging tools, we are currently witnessing the emergence of a new field in immuno-imaging, in which leukocyte function and cell-cell communication is explored in a truly physiological context.

New model for in vivo investigation after microvascular breakdown in burns: use of intravital fluorescent microscopy

BACKGROUND

The breakdown of skin microcirculation is assumed to play a key role in the pathophysiology after burn injury. The aim of the present study was to develop a burn model, which allows repetitive quantitative in vivo analysis of the microcirculation after a burn injury, focusing on the interaction between leukocytes and the endothelium.

MATERIALS AND METHODS

Experiments were carried out on male hairless mice. Deep partial thickness burns were inflicted with a no-touch-technique to the ears. Intravital fluorescent microscopy in combination with FITC-dextran as a plasma marker was used to assess microcirculatory parameters. Leukocytes were stained with rhodamine 6G. Preburn baseline data was obtained before as well as 1, 3, 7 and 14 days subsequent to the burn injury.

RESULTS

The non-perfused area decreased significantly over the observed period and perfusion was almost completely restored at day 14. The functional vessel density was characterized by reduction of perfused vessels immediately after burn and an increase after 24h. Leukocyte endothelium interaction significantly increased immediately after injury; baseline values were reached 1 day later. The extravasation of the plasma marker into the surrounding tissue increased immediately after burn, decreased at day 1 and remained at this level during the following observation time. The venular as well as the arterial blood flow increased immediately subsequent to the burn injury, decreased after 1 day and reached baseline values at day 3.

CONCLUSION

The presented burn model allows quantitative assessment of the dynamics of microcirculatory disturbances after thermal trauma by high quality visualization of both plasma stained microvessels and leukocyte-endothelium interaction.

Acute effects of N-acetylcysteine on skeletal muscle microcirculation following closed soft tissue trauma in rats

Trauma-induced microcirculatory dysfunction, formation of free radicals and decreased endothelial release of nitric oxide (NO) contribute to evolving tissue damage following skeletal muscle injury. Administration of N-acetylcysteine (NAC) known to scavenge free radicals and generate NO is considered a valuable therapeutic approach. Thus, the objective of this study was to quantitatively analyze the acute effects of NAC on skeletal muscle microcirculation and leukocyte-endothelial cell interaction following severe standardized closed soft tissue injury (CSTI). Severe CSTI was induced in the hindlimbs of 14 male anesthetized Sprague-Dawley rats using the controlled impact injury technique. Rats were randomly assigned (n = 7) to high-dose intravenous infusion of NAC (400 mg/kg body weight) or isovolemic normal saline (NS). Non-injured, sham-operated animals (n = 7) were subjected to the same surgical procedures but did not receive any additional fluid. Creatin kinase (CK) activity was assessed at baseline, 1 h before and 2 h following posttraumatic NAC or NS infusion. Microcirculation of the extensor digitorum longus (EDL) muscle was analyzed using intravital microscopy and Laser-Doppler flowmetry (LDF). Edema index (EI) was calculated by measuring the EDL wet-to-dry weight ratio (EI=injured/contralateral limb). EDL-muscles were analyzed for desmin immunoreactivity and granulocyte infiltration. Microvascular deteriorations observed following NS-infusion were effectively reversed by NAC: Functional capillary density was restored to levels found in sham-operated animals and leukocyte adherence was significantly (p < 0.05) reduced compared to the NS group. NAC significantly (p < 0.05) increased erythrocyte flux determined by Laser-Doppler flowmetry. Posttraumatic serum CK levels and EI were significantly (p < 0.05) decreased by NAC. During the posttraumatic acute phase, single infusion of NAC markedly reduced posttraumatic microvascular dysfunction, attenuated both leukocyte adherence and tissue infiltration. NAC also decreased CSTI-induced edema formation and myonecrosis as reflected by attenuated serum CK levels and attenuated loss of desmin immunoreactivity. NAC may serve as an effective therapeutic strategy by supporting microvascular blood supply and tissue viability in the early posttraumatic period. Additional studies aimed at long-term analysis and investigation of injury severity--or dosage dependency are needed.

Bench-to-bedside review: sepsis is a disease of the microcirculation

Microcirculatory perfusion is disturbed in sepsis. Recent research has shown that maintaining systemic blood pressure is associated with inadequate perfusion of the microcirculation in sepsis. Microcirculatory perfusion is regulated by an intricate interplay of many neuroendocrine and paracrine pathways, which makes blood flow though this microvascular network a heterogeneous process. Owing to an increased microcirculatory resistance, a maldistribution of blood flow occurs with a decreased systemic vascular resistance due to shunting phenomena. Therapy in shock is aimed at the optimization of cardiac function, arterial hemoglobin saturation and tissue perfusion. This will mean the correction of hypovolemia and the restoration of an evenly distributed microcirculatory flow and adequate oxygen transport. A practical clinical score for the definition of shock is proposed and a novel technique for bedside visualization of the capillary network is discussed, including its possible implications for the treatment of septic shock patients with vasodilators to open the microcirculation.