Recommendations for using artificial intelligence in clinical flow cytometry

Flow cytometry is a key clinical tool in the diagnosis of many hematologic malignancies and traditionally requires close inspection of digital data by hematopathologists with expert domain knowledge. Advances in artificial intelligence (AI) are transferable to flow cytometry and have the potential to improve efficiency and prioritization of cases, reduce errors, and highlight fundamental, previously unrecognized associations with underlying biological processes. As a multidisciplinary group of stakeholders, we review a range of critical considerations for appropriately applying AI to clinical flow cytometry, including use case identification, low and high risk use cases, validation, revalidation, computational considerations, and the present regulatory frameworks surrounding AI in clinical medicine. In particular, we provide practical guidance for the development, implementation, and suggestions for potential regulation of AI-based methods in the clinical flow cytometry laboratory. We expect these recommendations to be a helpful initial framework of reference, which will also require additional updates as the field matures.

Guidelines for the use of flow cytometry and cell sorting in immunological studies (third edition)

The third edition of Flow Cytometry Guidelines provides the key aspects to consider when performing flow cytometry experiments and includes comprehensive sections describing phenotypes and functional assays of all major human and murine immune cell subsets. Notably, the Guidelines contain helpful tables highlighting phenotypes and key differences between human and murine cells. Another useful feature of this edition is the flow cytometry analysis of clinical samples with examples of flow cytometry applications in the context of autoimmune diseases, cancers as well as acute and chronic infectious diseases. Furthermore, there are sections detailing tips, tricks and pitfalls to avoid. All sections are written and peer-reviewed by leading flow cytometry experts and immunologists, making this edition an essential and state-of-the-art handbook for basic and clinical researchers.

Fast RBC loading by fluorescent antibodies and nuclei staining dye and their potential bioanalytical applications

This study was designed to load different antibodies (Abs) and a fluorescent dye onto the red blood cell (RBC) surface. We have used fluorescein isothiocyanate (FITC)-conjugate anti-human Ab, CD22-PE (B-cell marker-phycoerythrin Ab), and 4',6-diamidino-2-phenylindole (DAPI) for insertion over the RBC surface. In a first step, conjugation experiments were performed: in dimethyl sulfoxide (DMSO), RBCs were conserved and modified by succinic anhydride to create an additional -COOH group, and then activated with 3-(3-dimethylaminopropyl)carbodiimide-N-hydroxysuccinimide (EDC-NHS) in 2-(N-morpholino) ethanesulfonic acid hydrate buffer for insertion of labeled Abs or DAPI. In a second step, fluorescence signals were evaluated by microscopy and the mean fluorescence intensities of cell lysates were measured by spectrofluorometry. The results showed clear evidence for adsorption of FITC- and PE-labeled Abs to activated conserved RBCs. DAPI was adsorbed well also to DMSO-conserved RBCs without the need for an activation step. The DMSO conservation step was enough to create reactive RBCs for insertion of specific Abs and fluorescent dyes. The additional modification by succinic anhydride and activation with EDC-NHS resulted in two- to seven-fold increase in fluorescence signals, indicating a much higher RBC loading capacity. These Ab- and fluorescent dye-functionalized RBCs have potentially high application in developing new biomedical diagnostic and in vitro assay techniques.

Three-dimensional imaging technologies: a priority for the advancement of tissue engineering and a challenge for the imaging community

Tissue engineering/regenerative medicine (TERM) is an interdisciplinary field that applies the principle of engineering and life sciences to restore/replace damaged tissues/organs with in vitro artificially-created ones. Research on TERM quickly moves forward. Today newest technologies and discoveries, such as 3D-/bio-printing, allow in vitro fabrication of ex-novo made tissues/organs, opening the door to wide and probably never-ending application possibilities, from organ transplant to drug discovery, high content screening and replacement of laboratory animals. Imaging techniques are fundamental tools for the characterization of tissue engineering (TE) products at any stage, from biomaterial/scaffold to construct/organ analysis. Indeed, tissue engineers need versatile imaging methods capable of monitoring not only morphological but also functional and molecular features, allowing three-dimensional (3D) and time-lapse in vivo analysis, in a non-destructive, quantitative, multidimensional analysis of TE constructs, to analyze their pre-implantation quality assessment and their fate after implantation. This review focuses on the newest developments in imaging technologies and applications in the context of requirements of the different steps of the TERM field, describing strengths and weaknesses of the current imaging approaches.

Trypan blue as an affordable marker for automated live-dead cell analysis in image cytometry

The aim of the present study was to combine image cytometry and trypan blue (TB) exclusion staining for a reproducible high-throughput detection of dead cells, enabling TB as an inexpensive marker, to be affordable for many studies and creating the possibility to combine fluorochromes without or with less spectral overlap. Capillary blood was drawn from a healthy volunteer, red blood cells were lysed and leukocyte cell death was induced. Samples were stained with CD45-FITC, CD14-PE, TB and DAPI, and then analyzed using image cytometry (iCys). TB quenching control tests were performed using DAPI and CD45-FITC. Images were generated in .TIF and .JPEG format using iCys image cytometer. The images were analyzed using CellProfiler (CP) modules to optimize the analysis based on the aims of each phase of this study. CellProfiler Analyst (CPA) was used to classify cells throughout machine learning and to calculate sensibility of the classification. A sensitivity of 0.94 for dead cells and 0.99 for live cells was calculated using CPA. We did not see any quenching effects of the FITC staining. DAPI signal was reduced in the presence of TB. The results of the present study revealed that TB serves as a dead cell marker in an image cytometric analysis, being able to be combined with other fluorescence markers without loss of fluorescence intensity signal or overlapping emission spectrum. SCANNING 38:857-863, 2016. © 2016 Wiley Periodicals, Inc.

Nanoparticle uptake by macrophages in vulnerable plaques for atherosclerosis diagnosis

The composition of atherosclerotic (AS) plaques is crucial concerning rupture, thrombosis and clinical events. Two plaque types are distinguished: stable and vulnerable plaques. Vulnerable plaques are rich in inflammatory cells, mostly only M1 macrophages, and are highly susceptible to rupture. These plaques represent a high risk particularly with the standard invasive diagnosis by coronary angiography. So far there are no non-invasive low-risk clinical approaches available to detect and distinguish AS plaque types in vivo. The perspective review introduces a whole work-flow for a novel approach for non-invasive detection and classification of AS plaques using the diffusion reflection method with gold nanoparticle loaded macrophages in combination with flow and image cytometric analysis for quality assurance. Classical biophotonic methods for AS diagnosis are summarized. Phenotyping of monocytes and macrophages are discussed for specific subset labelling by nanomaterials, as well as existing studies and first experimental proofs of concept for the novel approach are shown. In vitro and in vivo detection of NP loaded macrophages (MΦ). Different ways of MΦ labelling include (1) in vitro labelling in suspension (whole blood or buffy coat) or (2) labelling of short-term MΦ cultures with re-injection of MΦ-NP into the animal to detect migration of the cells in the plaques and (3) in vivo injection of NP into the organism.

The LIFE-Adult-Study: objectives and design of a population-based cohort study with 10,000 deeply phenotyped adults in Germany

Background

The LIFE-Adult-Study is a population-based cohort study, which has recently completed the baseline examination of 10,000 randomly selected participants from Leipzig, a major city with 550,000 inhabitants in the east of Germany. It is the first study of this kind and size in an urban population in the eastern part of Germany. The study is conducted by the Leipzig Research Centre for Civilization Diseases (LIFE). Our objective is to investigate prevalences, early onset markers, genetic predispositions, and the role of lifestyle factors of major civilization diseases, with primary focus on metabolic and vascular diseases, heart function, cognitive impairment, brain function, depression, sleep disorders and vigilance dysregulation, retinal and optic nerve degeneration, and allergies.

Methods/design

The study covers a main age range from 40-79 years with particular deep phenotyping in elderly participants above the age of 60. The baseline examination was conducted from August 2011 to November 2014. All participants underwent an extensive core assessment programme (5-6 h) including structured interviews, questionnaires, physical examinations, and biospecimen collection. Participants over 60 underwent two additional assessment programmes (3-4 h each) on two separate visits including deeper cognitive testing, brain magnetic resonance imaging, diagnostic interviews for depression, and electroencephalography.

Discussion

The participation rate was 33 %. The assessment programme was accepted well and completely passed by almost all participants. Biomarker analyses have already been performed in all participants. Genotype, transcriptome and metabolome analyses have been conducted in subgroups. The first follow-up examination will commence in 2016.

Detection of gold nanorods uptake by macrophages using scattering analyses combined with diffusion reflection measurements as a potential tool for in vivo atherosclerosis tracking

In this study, we report a potential noninvasive technique for the detection of vulnerable plaques using scatter analyses with flow cytometry (FCM) method combined with the diffusion reflection (DR) method. The atherosclerotic plaques are commonly divided into two major categories: stable and vulnerable. The vulnerable plaques are rich with inflammatory cells, mostly macrophages (MΦ), which release enzymes that break down collagen in the cap. The detection method is based on uptake of gold nanorods (GNR) by MΦ. The GNR have unique optical properties that enable their detection using the FCM method, based on their scattering properties, and using the DR method, based on their unique absorption properties. This work demonstrates that after GNR labeling of MΦ, 1) the FCM scatter values increased up to 3.7-fold with arbitrary intensity values increasing from 1,110 to 4,100 and 2) the DR slope changed from an average slope of 0.196 (MΦ only) to an average slope of 0.827 (MΦ labeled with GNR) (P<0.001 for both cases). The combination of FCM and DR measurements provides a potential novel, highly sensitive, and noninvasive method for the identification of atherosclerotic vulnerable plaques, aimed to develop a potential tool for in vivo tracking.

Native extracellular matrix: a new scaffolding platform for repair of damaged muscle

Effective clinical treatments for volumetric muscle loss resulting from traumatic injury or resection of a large amount of muscle mass are not available to date. Tissue engineering may represent an alternative treatment approach. Decellularization of tissues and whole organs is a recently introduced platform technology for creating scaffolding materials for tissue engineering and regenerative medicine. The muscle stem cell niche is composed of a three-dimensional architecture of fibrous proteins, proteoglycans, and glycosaminoglycans, synthesized by the resident cells that form an intricate extracellular matrix (ECM) network in equilibrium with the surrounding cells and growth factors. A consistent body of evidence indicates that ECM proteins regulate stem cell differentiation and renewal and are highly relevant to tissue engineering applications. The ECM also provides a supportive medium for blood or lymphatic vessels and for nerves. Thus, the ECM is the nature's ideal biological scaffold material. ECM-based bioscaffolds can be recellularized to create potentially functional constructs as a regenerative medicine strategy for organ replacement or tissue repopulation. This article reviews current strategies for the repair of damaged muscle using bioscaffolds obtained from animal ECM by decellularization of small intestinal submucosa (SIS), urinary bladder mucosa (UB), and skeletal muscle, and proposes some innovative approaches for the application of such strategies in the clinical setting.

Agonist-induced β2-adrenoceptor desensitization and downregulation enhance pro-inflammatory cytokine release in human bronchial epithelial cells

It is not clear whether increased asthma severity associated with long-term use of β2-adrenoceptor (β2-AR) agonists can be attributed to receptor degradation and increased inflammation. We investigated the cross-talk between β-AR agonist-mediated effects on β2-AR function and expression and cytokine release in human bronchial epithelial cells. In 16HBE14o(-) cells grown in the presence and absence of β-AR agonists and/or antagonists, the β2-AR density was assessed by radioligand binding; the receptor protein and mRNA was determined using laser scanning cytometer and RT-PCR; cAMP generation, the cytokines IL-6 and IL-8 release were determined using AlphaScreen Assay and ELISA, respectively. Isoprenaline (ISO) and salbutamol (Salbu) induced a concentration- and time-dependent significant decrease in β2-AR density. Both Salbu and ISO reduced cAMP generation in a concentration-dependent manner while in same cell culture the IL-6 and IL-8 release was significantly enhanced. These effects were antagonized to a greater extent by ICI 118.551 than by propranolol, but CGP 20712A had no effect. Reduction of the β2-AR protein and mRNA could be seen when cells were treated with ISO for 24 h. Our findings indicate a direct link between cytokine release and altered β2-AR expression and function in airway epithelial cells. β2-AR desensitization and downregulation induced by long-term treatment with β2-AR agonists during asthma may account for adverse reactions also due to enhanced release of pro-inflammatory mediators and should, thus, be considered in asthma therapy.

Role of dendritic cells in the context of acute cellular rejection: comparison between tacrolimus- or cyclosporine A-treated heart transplanted recipients

BACKGROUND

In the last years many studies have been designed to predict risk of acute rejection and to adapt the immunosuppressive therapy. The importance of dendritic cells (DCs) in the immune response, especially their role in tolerance is known. Thus, we investigated the influence of tacrolimus (TAC)-based and of cyclosporine A (CsA)-based immunosuppressive therapies on dendritic cells and the incidence of rejection in heart transplant recipients.

METHODS

Groups consisted of 14 CsA treated and 15 TAC treated patients. At different study time points (0, 3 and 6 months after study begin) peripheral blood from the patients was drawn to analyse (1) blood concentration of CsA or TAC (trough value) and (2) percentages of plasmacytoid and myeloid DC (p and mDC) subsets using flow cytometry. Histological rejection grading was performed of endomyocardial biopsies.

RESULTS

TAC treated patients had significantly higher values of pDCs (CsA group 53.9%±13.0%; TAC group 67.5%±8.4%; p<0.05) and significantly lower values of mDCs than CsA treated patients (CsA group 58%±19.0%; TAC group 45.2%±10.7%; p<0.05). In general, HTx patients with rejection grade of ≥2 had significant lower values of pDCs (55.1%±16.2%) compared to patients without rejection (63.6%±10.5%; p<0.05). TAC-treated patients had significantly less rejections CsA-treated patients (CsA group 0.86±0.95; TAC group 0.2±0.4; p<0.05).

CONCLUSIONS

Our results showed that HTx patients with high pDCs had a lower risk for rejection and that TAC-treated patients had higher pDCs values compared to CsA-treated patients. Future studies need to define individual pDC values to predict acute cellular rejection.

New insights into cell cycle and DNA damage response machineries through high-resolution AMICO quantitative imaging cytometry

OBJECTIVE

Progress in biology and medicine research is being driven by development of new instrumentation and associated methodologies which open analytical capabilities that expand understanding of complexity of biological systems. Application of cytometry, which is now widely used in so many disciplines of biology, is the best example of such a progress.

METHODOLOGY

Recent publications push the envelope in expanding capabilities of cytometry by introducing a high resolution imaging cytometry defined as Automated Microscopy for Image CytOmetry (AMICO). This instrumentation is utilized to further elucidate mechanisms of the cell cycle progression and also the DNA damage response. This approach is going beyond the presently possible analytical technologies regarding throughput and depth of information.

CONCLUSIONS

The possibility of multiparametric analysis combined with the high resolution mapping of individual constituents of cell cycle and DNA damage response machineries provides new tools to probe molecular mechanism of these processes. The capability of analysis of proximity of these constituents to each other offered by AMICO is a novel and potentially important approach that can be used to elucidate mechanisms of other biological processes.

Label-free hybridoma cell culture quality control by a chip-based impedance flow cytometer

Impedance flow cytometry (IFC) was evaluated as a possible alternative to fluorescence-based methods for on-line quality monitoring of hybridoma cells. Hybridoma cells were cultured at different cell densities and viability was estimated by means of IFC and fluorescence-based flow cytometry (FCM). Cell death was determined by measuring the impedance phase value at high frequency in low conductivity buffer. IFC data correlate well with reference FCM measurements using AnnexinV and 7-AAD staining. Hybridoma cells growing at different densities in cell culture revealed a density-dependent subpopulation pattern. Living cells of high density cultures show reduced impedance amplitudes, indicating particular cellular changes. Dead cell subpopulations become evident in cultures with increasing cell densities. In addition, a novel intermediate subpopulation, which most probably represents apoptotic cells, was identified. These results emphasize the extraordinary sensitivity of high frequency impedance measurements and their suitability for hybridoma cell culture quality control.

Changes in neuronal DNA content variation in the human brain during aging

The human brain has been proposed to represent a genetic mosaic, containing a small but constant number of neurons with an amount of DNA exceeding the diploid level that appear to be generated through various chromosome segregation defects initially. While a portion of these cells apparently die during development, neurons with abnormal chromosomal copy number have been identified in the mature brain. This genomic alteration might to lead to chromosomal instability affecting neuronal viability and could thus contribute to age-related mental disorders. Changes in the frequency of neurons with such structural genomic variation in the adult and aging brain, however, are unknown. Here, we quantified the frequency of neurons with a more than diploid DNA content in the cerebral cortex of normal human brain and analyzed its changes between the fourth and ninth decades of life. We applied a protocol of slide-based cytometry optimized for DNA quantification of single identified neurons, which allowed to analyze the DNA content of about 500 000 neurons for each brain. On average, 11.5% of cortical neurons showed DNA content above the diploid level. The frequency of neurons with this genomic alteration was highest at younger age and declined with age. Our results indicate that the genomic variation associated with DNA content exceeding the diploid level might compromise viability of these neurons in the aging brain and might thus contribute to susceptibilities for age-related CNS disorders. Alternatively, a potential selection bias of "healthy aging brains" needs to be considered, assuming that DNA content variation above a certain threshold associates with Alzheimer's disease.

Cellular analysis by open-source software for affordable cytometry

Image cytometry is an important technique in affordable healthcare and cellular research. Some efforts toward establishing a personal, low-cost cytometer have been described in the literature. However, a self-assembled fluorescence microscope requires software for cytometric analysis. There are some open-source image-based software analysis applications available. However, for a quantitative analysis of images, software that can generate data comparable to those of previously evaluated cytometric analyses programs is required. Hence, the aim of this study is to compare results of a commercially available image cytometry program to data obtained using the open-source software CellProfiler (CP). Leukocytes and fluorescent bead images obtained using a Laser Scanning Cytometer were analyzed by CP and the results compared with those of conventional cytometric analyses' programs. Algorithms were developed enabling the analysis of leukocytes and beads by CP. CP provided similar results to those obtained by the cytometer software. Hallmark parameters, including cell count and fluorescence intensity, revealed a high correlation in the analysis of both programs. Therefore, CP is appropriate for cellular analysis on a self-assembled microscope, thereby enabling affordable cytometry.

Differences in the kinetics of gamma-H2AX fluorescence decay after exposure to low and high LET radiation

PURPOSE

In order to obtain more insight into heavy ion tumour therapy, some features of the underlying molecular mechanisms controlling the cellular response to high linear energy transfer (LET) radiation are currently analysed.

MATERIALS AND METHODS

We analysed the decay of the integrated fluorescence intensity of gamma-H2AX (phosphorylated histone H2AX) which is thought to reflect the repair kinetics of radiation-induced DNA double-strand breaks (DSB) using Laser-Scanning-Cytometry. Asynchronous human HeLa cells were irradiated with a single dose of either 1.89 Gy of 55 MeV carbon ions or 5 Gy of 70 kV X-rays.

RESULTS

Measurements of the gamma-H2AX-intensities from 15-60 min resulted in a 16 % decrease for carbon ions and in a 43 % decrease for X-rays. After 21 h, the decrease was 77 % for carbon ions and 85 % for X-rays. The corresponding time-effect relationship was fitted by a bi-exponential function showing a fast and a slow component with identical half-life values for both radiation qualities being 24 +/- 4 min and 13.9 +/- 0.7 h, respectively. Apparent differences in the kinetics following high and low LET irradiation could completely be attributed to quantitative differences in their contributions, with the slow component being responsible for 47 % of the repair after exposure to X-rays as compared to 80 % after carbon ion irradiation.

CONCLUSION

gamma-H2AX loss kinetics follows a bi-exponential decline with two definite decay times independent of LET. The higher contribution of the slow component determined for carbon ion exposure is thought to reflect the increased amount of complex DSB induced by high LET radiation.

Characterization of fibroblasts responsible for cartilage destruction in arthritis

In the pathogenesis of rheumatoid arthritis (RA), synovial fibroblasts (SF) play a key role as they secrete distinct patterns of cytokines and express variable levels of costimulatory and adhesion molecules. The murine fibroblast cell line LS48 has been shown to be invasive in the cartilage destruction models in vivo and in vitro. The purpose of this study was to examine in detail the LS48 phenotype, to obtain a better understanding of the SF-mediated cartilage destruction in RA. The destructive fibroblasts line LS48 and the nondestructive 3T3 cells were cultured and characterized with slide-based and flow cytometry, using antibodies against several adhesion molecules, immunological acting molecules, and marker proteins. The invasive LS48 fibroblasts are characterized by significantly higher expression of adhesion molecules such as CD47 (IAP), CD51 (integrin alpha V), CD61 (GPIIIa), and CD147 (EMMPRIN), and immunological acting molecules such as CD40 (Bp50), CD55 (DAF), and TLR-2. The results from the slide-based and flow cytometry analyses were exactly the same, except for the selected CD147 and TLR-2. This study demonstrated that the destructive fibroblast cell line LS48 has the characteristics of RA SFs. The high expression of specific costimulatory and adhesion molecules underlines the aberrant phenotype of these cells when compared with noninvasive fibroblasts. Furthermore, slide-based and flow cytometry complement each other in fibroblast phenotyping. Overall, this study shows that LS48 is an excellent tool to gain a deeper understanding of SF in RA.

Pharmacodynamic monitoring of the immunosuppressive therapy in patients after heart transplantation: Whole blood flow cytometric analysis of lymphocyte function

Despite therapeutic monitoring and daily measurements of blood concentrations (pharmacokinetics) of immunosuppressive medications, immunosuppressive therapy remains still a challenge after heart transplantation (HTx) due to drug interactions, toxicities and individual responses to drug effects. We established whole blood flow cytometric assays of lymphocyte function to assess the pharmacodynamics of immunosuppressive therapy and investigated both pharmacokinetic and pharmacodynamic approaches after HTx. Our results showed that pharmacodynamic measurements provide a more direct assessment of the functional activity of immunosuppressants on immune cells compared to drug level monitoring alone. The information from both pharmacokinetic and pharmacodynamic monitoring has the potential to increase the efficacy and safety of individual immunosuppressive therapy after HTx.

High, but not moderate frequency and duration of exercise training induces downregulation of the expression of inflammatory and atherogenic adhesion molecules

BACKGROUND

Lifestyle changes which include daily exercise training have been shown to slow the progression of coronary artery disease. We designed a study to examine the effects of a multifactorial intervention on atherogenic adhesion molecules on the surface of monocytes in patients with coronary artery disease.

METHODS

We randomized 39 patients with coronary artery disease to (i) an intervention program which consisted of 4 weeks of daily 6x15 min ergometer training at submaximal intensity in addition to a 1 h/week group exercise session, followed by 5 months of home-based ergometer training of 30 min/day again in addition to a 1 h/week group exercise session or (ii) conventional therapy. All patients received a statin. Monocyte-bound cellular adhesion molecules LFA-1 (CD11a), MAC-1 (CD11b), VLA-4 (CD49d) and L-selectin (CD62L) were assessed by fluorescence activated cell sorting analysis.

RESULTS

After 4 weeks the multifactorial intervention led to a significant improvement of maximal work capacity, lipid profile, body mass index, blood pressure, fasting glucose and hemoglobin A1c. This was associated with a reduced expression of MAC-1 and VLA-4. After 5 months of a home-based intervention the beneficial effects of the cardiovascular risk profile were still apparent, whereas the effects on the expression of adhesion molecules were blunted.

CONCLUSION

In patients treated with statins, 4 weeks of high frequency and long duration exercise training led to a diminished expression of atherogenic adhesion molecules MAC-1 und VLA-4. After 5 months of home-based exercise training of moderate frequency and duration, these effects were blunted. Our data suggest that our patients in cardiac rehabilitation programs might further benefit from the antiatherogenic effects of an even higher amount of exercise training.

Aneuploidy and DNA replication in the normal human brain and Alzheimer's disease

Reactivation of the cell cycle, including DNA replication, might play a major role in Alzheimer's disease (AD). A more than diploid DNA content in differentiated neurons might alternatively result from chromosome mis-segregation during mitosis in neuronal progenitor cells. It was our objective to distinguish between these two mechanisms for aneuploidy and to provide evidence for a functional cell cycle in AD. Using slide-based cytometry, chromogenic in situ hybridization, and PCR amplification of alu-repeats, we quantified the DNA amount of identified cortical neurons in normal human brain and AD and analyzed the link between a tetraploid DNA content and expression of the early mitotic marker cyclin B1. In the normal brain, the number of neurons with a more than diploid content amounts to approximately 10%. Less than 1% of neurons contains a tetraploid DNA content. These neurons do not express cyclin B1, most likely representing constitutional tetraploidy. This population of cyclin B1-negative tetraploid neurons, at a reduced number, is also present in AD. In addition, a population of cyclin B1-positive tetraploid neurons of approximately 2% of all neurons was observed in AD. Our results indicate that at least two different mechanisms need to be distinguished giving rise to a tetraploid DNA content in the adult brain. Constitutional aneuploidy in differentiated neurons might be more frequent than previously thought. It is, however, not elevated in AD. In addition, in AD some neurons have re-entered the cell cycle and entirely passed through a functional interphase with a complete DNA replication.

Pharmacodynamics of T-cell function for monitoring immunosuppression

OBJECTIVES

Recent studies show that measuring pharmacodynamic (PD) effects offers a unique possibility to predict immunosuppression. Thus, in this study we have monitored the PD properties of immunosuppressants on diverse T-cell functions in heart transplant (HTx) recipients.

MATERIALS

PDs and blood concentrations (PK) of three different basis-immunosuppressive drugs were studied: cyclosporin A (CsA); tacrolimus (TRL) and sirolimus (SRL). T-cell function was analysed by expression of proliferating cell nuclear antigen (PCNA) labelling, expression of cytokines (IL-2, IFN-gamma) and surface antigen (for example, CD25) by FACS analysis.

RESULTS

In group I, at time points C0 and C2, increased CsA-PK significantly inhibited expression of IL-2, IFN-gamma, PCNA and CD25 (P < 0.05). Correlations (r(2)) at C2 between inhibition of T-cell functions (PD) with PK and with drug doses were: CsA-PK: 0.71-0.91 and CsA-dose: 0.73-0.87. In group II, increased TRL-PK over time did not further inhibit expression of CD25, but inhibited PCNA expression more on day 3, and IL-2 and IFN-gamma expression was significantly higher on days 2 and 3 compared to PD effects of CsA (P < 0.05). Blood SRL concentrations in C0 group III, increased on day 1 and remained stable at days 3 and 4. Expression of PCNA was not altered in the SRL-PK category, whereas expression of CD25 was higher and expression of cytokines was lower than PD effects of CsA.

CONCLUSIONS

Our results show that PD effects on T-cell function can be used to monitor immunosuppression bringing potential to increase the efficacy and safety of immunosuppressive therapy after HTx.

Circulating endothelial progenitor cells are inversely correlated with the median oxygen tension in the tumor tissue of patients with cervical cancer

Tumor hypoxia leads to adaptive responses in cancer cells, including an induction of vasculogenesis initiated by circulating endothelial progenitor cells (EPCs) and circulating endothelial cells (CECs). The aim of the present study was to correlate the number of EPCs and CECs with the oxygenation of cervical cancer. Blood concentrations of EPCs were detected by FACS analysis with antibodies for CD34 and vascular endothelial growth factor receptor 2 (VEGFR2). CECs were evaluated by double staining for 1,1'-dioctadecyl-3,3,3',3'-tetramethylindocarbocyanine-labeled acetylated low density lipoprotein (Di-LDL) and lectin in a cell culture assay. Ten patients with cervical cancer were compared with ten healthy volunteers. Intratumoral oxygen tension was assessed polarographically with the computerized Eppendorf histography system. Analysis of CEC numbers revealed no difference between patients and controls. However, patients had lower concentrations of CD34-positive hematopoietic stem cells (HSCs) but a significantly higher fraction of EPCs related to the number of HSCs (1.09% versus 0.53%). This fraction was significantly inversely correlated to the median oxygen tension (r = -0.74, p = 0.015). Our study shows for the first time a significant inverse correlation between the fraction of EPCs and intratumoral oxygen tension. We conclude that the fraction of EPCs should be further evaluated as a useful and convenient marker in the prediction of tumor tissue oxygenation.

Mycophenolic Acid Interaction With Cyclosporine and Tacrolimus In Vitro and In Vivo

The effect of mycophenolic acid (MPA) in combination with either cyclosporine (CsA) or tacrolimus (TRL) on whole-blood lymphocyte function was assessed in vitro as well as in vivo. For the in vitro studies, rat whole blood was incubated with different concentrations of MPA together with CsA or TRL. In vivo, rats (n = 6 per group) were orally treated with 2.5 or 5 mg/kg of mycophenolate mofetil (MMF), either alone or in combination with 5 mg/kg CsA or 4 mg/kg TRL. Blood was obtained before and at different times after dosing. For both in vitro and in vivo studies, mitogen-stimulated whole blood was analyzed by flow cytometry to determine inhibition of expression of lymphocyte proliferation (proliferating cell nuclear antigen, PCNA) and T-cell activation (eg, CD25). Plasma MPA concentrations were measured by HPLC, and whole-blood CsA and TRL concentrations were quantified using LC-MS/MS. In vitro, low concentrations of 250 and 500 nM MPA acted additively with CsA and overadditively with TRL to suppress lymphocyte function, whereas higher MPA concentrations (1000 nM) in these combinations did not further increase inhibition compared with monotherapy with CsA or TRL alone. In vivo, the MPA AUC0-24 showed a dose-dependent increase. CsA and TRL AUC0-24 were not influenced by the MMF dose. Combination therapy increased inhibition of lymphocyte function compared with MMF monotherapy with a pronounced effect on PCNA compared with CD25. Significant differences between 2.5 and 5 mg/kg MMF in the combination groups were observed at 2 or 6 hours after dosing because of the maximal inhibitory effect on PCNA and CD25 expression (P < 0.05, ANOVA). However, in combination with TRL no different effects on the inhibition of CD25 expression were found between the 2 MMF doses. These novel data indicate that measurement of pharmacodynamic parameters of lymphocyte function in whole blood may help to monitor drug combination therapy and provide a rationale for drug reduction to minimize toxicity without compromising efficacy.

Diurnal Variation of Soluble E- and P-Selectin, and Intercellular Adhesion Molecule-1 in Patients with and without Coronary Artery Disease

BACKGROUND

The more frequent onset of acute coronary syndromes (ACS) in the morning has been known for a long time. Diurnal changes of fibrinolysis such as lower activity of tissue plasminogen activator and higher activity of plasminogen activator inhibitor-1 (PAI-1) in the morning has been demonstrated previously and correspond with the manifestation of ACS. Less is known about the diurnal variation of soluble adhesion molecules as markers of endothelial or platelet activity in patients with coronary artery disease (CAD).

PATIENTS AND METHODS

80 patients with a history of myocardial infarction and/or chest pain with positive exercise testing admitted for elective coronary angiography were studied. 10 had normal findings on coronary angiography (control group), 70 patients had at least one or more stenoses >/=50% of the diameter of an epicardial vessel. None of the patients suffered from acute inflammation, connective or tumor disease. Blood samples were drawn at 7:00 a.m. and at 7:00 p.m. at rest and plasma concentration of soluble P-selectin (sP-selectin), E-selectin (sE-selectin), intercellular adhesion molecule-1 (sICAM-1) and acute-phase proteins were measured by ELISA.

RESULTS

In both groups, no diurnal variation was found in sE-selectin and sICAM-1. sP-selectin levels were significantly higher in the evening (CAD group: 149.8 +/- 54.5 vs. 172.2 +/- 68.8 ng/ml, p < 0.001; control: 148.7 +/- 75.5 vs. 187.5 +/- 96.3 ng/ml, p = 0.001, Wilcoxon test).

CONCLUSION

We have demonstrated diurnal variation of sP-selectin in patients with CAD. We conclude that high sP-selectin values in the evening represent the shed forms of the morning membrane-bound P-selectin.

Synergistic effects of sirolimus with cyclosporine and tacrolimus: analysis of immunosuppression on lymphocyte proliferation and activation in rat whole blood

BACKGROUND

Whole-blood analysis of lymphocyte function was used to investigate the pharmacodynamic (PD) interaction of sirolimus (SRL) with cyclosporine (CsA) or tacrolimus (TRL) in vitro and to determine the relation between PD and pharmacokinetics (PK) of SRL in an in vivo rat model.

METHODS

In vitro, experiments involved incubation of increasing concentrations (0.25-25 [corrected] nM) of SRL with either CsA or TRL in rat whole blood. For the in vivo study, rats were orally treated with different doses of SRL alone (1, 3, 5, or 8 mg/kg) or with a combination of 3 mg/kg SRL plus 2.5 or 5 mg/kg CsA. Blood was obtained before and at different times after dosing. Inhibition of lymphocyte proliferation (proliferating cell nuclear antigen [PCNA]) and activation (CD25, CD71, CD11a, CD134) in mitogen-stimulated blood was determined using fluorescence-activated cell sorter analysis. SRL and CsA blood concentrations were determined at the same time points by light chromatography tandem mass spectrometry (LC-MS).

RESULTS

In vitro, concentrations of SRL between 0.25-25 [corrected] nM acted synergistically in combination with CsA or TRL at concentrations between 0.25-1.0 [corrected] nM. Higher SRL concentrations did not further increase inhibition of lymphocyte function in these combinations. In vivo, good correlations (r=0.68-0.94) were observed between PD parameters of lymphocyte function and SRL-PK and dose. Increasing SRL doses produced higher blood concentrations, but SRL doses of 8 mg/kg did not further increase inhibition of lymphocyte function. PD effects on lymphocyte function were prolonged, but maximal inhibition was not increased when SRL was applied in combination with CsA as compared to SRL mono therapy.

CONCLUSIONS

The results suggest that analysis of lymphocyte function in whole blood may be useful to optimize dosing of SRL in combination with CsA or TRL and that PD monitoring of immunosuppressive drugs will enhance the value of PK monitoring.

Increase of circulating endothelial progenitor cells in patients with coronary artery disease after exercise-induced ischemia

OBJECTIVE

The concept of neovascularization in response to tissue ischemia has been extended by the finding of postnatal vasculogenesis initiated by endothelial progenitor cells (EPCs). The aim of this study was to analyze whether a maximal stress test in patients with coronary artery disease (CAD) increases the number of circulating EPCs.

METHODS AND RESULTS

Blood concentration of EPCs was analyzed by FACS and cell culture assay in CAD patients with (n=16) or without (n=12) exercise-induced myocardial ischemia and in healthy subjects (n=11) for up to 144 hours after maximal stress test. Plasma concentrations of vascular endothelial growth factor (VEGF), basic fibroblast growth factor, tumor necrosis factor-alpha, and granulocyte macrophage-colony stimulating factor were determined by ELISA. EPCs increased significantly in ischemic patients, with a maximum after 24 to 48 hours (cell culture: 3.3+/-0.5-fold increase; FACS: 3.1+/-0.6-fold increase) and returned to baseline within 72 hour. In nonischemic patients and healthy subjects, no EPC increase was detectable. VEGF levels in ischemic patients increased significantly after 2 to 6 hours (maximum after 2 hours; 4.0+/-1.1-fold increase) and no change was observed in nonischemic patients and healthy subjects; DeltaVEGF and DeltaEPC correlated significantly (r=0.66).

CONCLUSIONS

Patients with symptomatic CAD respond to a single episode of exercise-induced myocardial ischemia with a time-dependent increase in circulating EPCs. This increase may be related to and preceded by an increase in plasma VEGF.