Positive selection of autologous peripheral blood stem cells

The development of monoclonal antibodies against differentiation antigens on human haematopoietic cells has led to a new concept in stem cell purification: the positive selection. In terms of autologous PBSC transplantation, the immature stem cells are identified by their expression of a specific antigen, the CD34. The CD34 antigen is expressed on early lymphohaematopoietic stem cells and progenitor cells, but not on mature blood cells or on tumour cells of several diseases. CD34+ cells are found in low numbers in bone marrow (<2%) and in even lower numbers in steady state blood (<0.01%) but may increase from 1 to 5% after mobilization using chemotherapy and/or growth factors. Several techniques have been set up to enrich PBSC grafts in CD34+ stem cells. The quality of each system is here analysed in terms of CD34 purity of the selected cell fraction, the CD34 cell recovery, the tumour cell depletion efficiency and the functional capacity ex vivo and in vivo of the selected cells. The final CD34+ cell purity of the selected fractions is correlated to the concentration of CD34+ cells before selection. The optimal recoveries and the highest purities were generally obtained when the initial CD34 content was roughly over 1%. Below this figure, the final purity seems to be less predictable. Besides the better tolerance resulting from the reduction in the number of autologous cells, and consequently the total volume of DMSO reinfused to the patient, the selective enrichment of the CD34 cell population offers a new approach to tumour purging. The procedure by itself results in elimination of about 99% in the total number of initial cells, thus allowing reduction of the overall tumour cell number in the final autograft. However, its major interest is that, in diseases where tumour cells do not express the CD34 antigen, it is theoretically able to completely eliminate the tumour contamination of the graft. Based on previous data showing that lymphoma, myeloma, neuroblastoma and breast cancer cells are not CD34+, pilot clinical trials for the separation and transplantation of CD34+ cells selected from PBSC of patients with these diseases have recently been conducted. The efficacy of CD34 selection in reducing the tumour load of the PBSC of patients with these diseases has been reported. However, the efficacy of purging may greatly differ between individual patients, and complete eradication of contaminating cells from PBSC grafts was not always reached. There is now evidence that purified CD34+ cells are capable of supporting haematopoietic reconstitution in autologous transplantation. However, until now no study has demonstrated clear evidence that the reduction of tumour cells from PBSC of patients by CD34+ cell selection resulted in a lower relapse rate post-transplant, as compared to unselected PBSC infusion.

T-cell depletion of allogeneic peripheral blood stem cells

The high content of immunocompetent T-cells in apheresis products may expose recipients of allogeneic peripheral blood stem cells (PBSC) to an elevated risk of acute and chronic graft-versus-host disease (GvHD). Thus, the use of an appropriate T-cell reduction or depletion technique might reduce this risk. The hazards of rejection and of a higher relapse rate should be avoided by maintaining a portion of the T-cells in the graft or by increasing the number of transplanted stem cells. The positive selection of CD34+ cells from peripheral blood preparations simultaneously provides an approximately 1,000-fold reduction of T-cells. Purified CD34+ cells containing committed and pluripotent stem cells are suitable for allogeneic transplantation. In transplantation from HLA-mismatched or three HLA-loci different family donors the amount of stem cells can be increased for reducing the incidence of rejection without increasing the T-cell number. In cases of poor marrow graft function a 'boost' with stem cells from the same family donor can be given. The risk of GvHD in transplantation from volunteer-matched unrelated donors might be reduced by T-cell depletion. If T-cells are used for enhancing the graft-versus-leukaemia effect, CD34+ enriched cells can be given for haematopoietic engraftment.

Rapid isolation of choriocapillary endothelial cells by Lycopersicon esculentum-coated Dynabeads

In vitro studies of choroidal endothelial cells may be critical for understanding the pathogenesis of neovascularization in age-related macular degeneration, since endothelial cells from different sites are highly heterogeneous in their morphology and behavior. Isolation of choroidal endothelial cells is complicated and labor intensive because of the small size of the choroid and the difficulty of excluding contaminating cells. We describe a rapid, simplified method for the isolation of bovine choroidal endothelial cells using microdissection followed by the use of superparamagnetic beads (Dynabeads) coated with the endothelial cell-specific lectin Lycopersicon esculentum, which selectively binds to fucose residues on the endothelial cell surface. Cells bound to beads are isolated using a magnetic particle concentrator. Isolated cells grew to confluence in a monolayer with a cobblestone morphology and were shown to be endothelial cells by their greater than 95% immunoreactivity to von Willebrand factor and phagocytosis of dil-acetylated LDL. Isolated cells grew as tubes in three-dimensional cultures. This method markedly reduces the time needed for pure culture of cells and makes the in vitro study of choroidal endothelial cells practical and reproducible.

Comparison of COBE white cell-reduction and standard plateletpheresis protocols in the same donors

BACKGROUND

It is necessary to protect patients from white cell (WBC)-caused side effects of platelet transfusion by reducing the WBC contamination in single-donor platelets.

STUDY DESIGN AND METHODS

A new COBE Spectra WBC (leuko)-reduction system (LRS) was compared to the COBE standard plateletpheresis (standard) procedure. Each of 62 donors underwent plateletpheresis under the two protocols (LRS and standard). The collection efficiency and WBC contamination in the components collected using the techniques were compared. Platelets were counted in a cell counter and WBCs were counted using two full grids of a Nageotte chamber.

RESULTS

The preseparation and postseparation numbers for red cells, WBCs, and platelets as well as the number of collected platelets were not different in the two techniques. Collection efficiency in the LRS procedures was 96.2 +/- 13.0 percent of that in the standard procedures. Median WBC contamination in the platelet components was 10,160 per LRS procedure and 56,500 per standard procedure. The purity of the LRS components was significantly improved (p = 0.001), as seen in a comparison of the WBC numbers in components per procedure after log10 transformation (LRS: 0.096 +/- 0.195 x 10(6); standard: 0.390 +/- 1.075 x 10(6)).

CONCLUSION

These data suggest that the LRS procedure produces platelet concentrates with a collection efficiency that is comparable to that obtained with the standard technique and with a residual WBC content that satisfies even the most stringent criteria for filtered platelets. As this purity can be achieved without platelet loss or alteration, conventional fiber filtration no longer seems necessary or useful in this type of single-donor platelet component.

Basic strategies for valid cytometry using image analysis

The present review provides a starting point for setting up an image analysis system for quantitative densitometry and absorbance or fluorescence measurements in cell preparations, tissue sections or gels. Guidelines for instrumental settings that are essential for the valid application of image analysis in cytophotometry and cytofluorometry are described. The general principles of the working mechanism of CCD cameras in combination with general methods to improve the behaviour of the cameras are presented. Optimization of illumination of microscopical and macroscopical objects receives special attention because of its importance for valid cytometry. Sources of errors in quantitative measurements are listed and step-by-step charts for tuning the CCD camera, frame grabber and illumination for the optimal use of the systems are described. Suggestions are given for improvement of image arithmetic in difficult imaging situations, such as low fluorescence signals and high absorbance signals.

The influence of flow cytometric gating strategy on the standardization of CD34+ cell quantitation: an Australian multicenter study. Australasian BMT Scientists Study Group

The Australian Multi-centre study on CD34+ cell quantitation by flow cytometry documented, first, the extent of variation of CD34+ cell enumeration and, second, the influence of flow cytometric gating on CD34+ cell measurement. A PBSC harvest analyzed by 20 participating centers showed results ranging from 0.64% to 2.80%, with a median of 1.54% CD34+ cells. Of 20 centers, 9 obtained results within +/-10% of the median (the criteria for reproducibility suggested by the ISHAGE Guidelines). The flow cytometric gating strategy was identified as one of the major variables among the methods used. In stage 2, list mode data from two samples were analyzed by 24 Australian and overseas centers, including the authors of three published guidelines. Significantly different CD34+ results were obtained when different gating strategies were used (p < 0.006). When all the centers used the same gating strategy, the measurement of CD34+ cells fell within a narrow range, with 0-7% of results outside +/-10% of the median. However, when different gating strategies were used, the results were more widely scattered, with 17% of centers outside +/-10% of the median. This study demonstrated the potential impact of flow cytometric gating strategy on the reproducibility of CD34+ cell enumeration.

Flow cytometric characterization of isolated porcine hepatocyte suspensions for liver support

The high yield hepatocyte isolation necessary for hybrid liver assist devices (LAD) unavoidably increases contamination by nonparenchymal cells and depresses hepatocyte viability and functions. We have developed a flow cytometric procedure that improves quality control of the isolations. Cells present in these preparations were labeled by immunofluorescent antibody staining against cytokeratin 8, 18 as well as vimentin to identify hepatocytes, fibroblasts, and endothelial cells. Antibody staining against albumin and carbamoylphosphate synthetase allowed assessment of levels of albumin and carbamoylphosphate synthetase based on the hepatocyte relative fluorescence intensity. Hepatocyte P450 enzyme activity was measured by its ability to convert 5,6-methoxycarbonylfluorescein, a nonfluorescent substrate, to an intracellular fluorescent product. Flow cytometric methods of cell type identification and cell function assessment are fast and accurate and can be applied to commercial cell production. They may also provide an avenue for the enrichment of otherwise heterogeneous hepatocyte suspensions with cells presenting the specific functions desired for an hybrid liver assist devices.

[Effect of the composition of liver perfusion media on functional properties of isolated hepatocytes and effectiveness of the isolation method]

Yield, viability and respiratory activity of hepatocytes isolated from rat after liver perfusion by media with various composition have been studied. Collagenase, EDTA or citrate were used as disaggregative agents, as well as sucrose or NaCl as a main osmotic component. The yield of intact cells after perfusion by different media decreased in the following order, collagenase -NaCl-->EDTA-sucrose-->citrate-sucrose-->EDTA-NaCl. The rate of endogenous respiration in hepatocytes isolated by non-enzymatic methods with EDTA did not depend on the nature of main osmotic component and was by 40% lower than in the cells isolated by the enzymatic method, however uncoupler-stimulated respiration changed significantly less. Replacement of EDTA by citrate increased the rate of endogenous respiration and particularly the uncoupler-stimulated respiration. The results show that the nature of disaggregative agent and main osmotic component has the influence on efficiency of cell isolation method as well as metabolic state of isolated hepatocytes. Sucrose leads to the cell shrinkage and have additional to Ca(2+)-chelator desaggregative effect, citrate plays two functions both as Ca(2+)-chelator and as mitochondrial substrate.

Performance evaluation of the FACSCount System: a dedicated system for clinical cellular analysis

Flow cytometers are instruments that can determine multiparameter data simultaneously and have a great potential in providing unique information about cells. The FACSCount System is designed as the first dedicated flow cytometer for the clinical laboratory. Its current configuration provides CD4, CD8, and CD3 absolute counts from 100 microliters of whole blood. Adapting the FACSCount System to the clinical setting are minimal sample handling, lysis free cell preparation, automated fluorescence gating, built-in calibrated reference beads, and appropriate error code reporting. Quality control checks ensure that reported CD4 counts, important for clinical follow-up and patient management, are accurate, precise, and reproducible across instruments over time.

Cell surface-bound urokinase-type plasminogen activator facilitates infiltration of freshly isolated granulocytes into fibrin matrix

Human cell lines of myelo/monocytic origin express the cellular receptor for urokinase-type plasminogen activator (uPA-R). The receptor localizes urokinase-type plasminogen activator (uPA) to the surface of the cell, where it can convert plasminogen to the active serine proteinase plasmin. Plasmin may subsequently account for proteolysis of pericellular proteins. We demonstrated the expression of the uPA-R by freshly isolated neutrophilic granulocytes by using a specific mAb. In freshly isolated granulocytes we detected only a weak occupation of the uPA-R; further uPA binding by granulocytes was saturable and proceeded in a dose-dependent manner. Receptor-bound uPA retained its enzymatic activity. Saturation of isolated granulocytes with exogenous uPA enhanced cellular infiltration into a fibrin matrix in vitro. uPA-dependent infiltration was inhibited by an anti-catalytic monoclonal anti-uPA antibody. The findings show that circulating neutrophilic granulocytes express the cell surface uPA-R and suggest that surface-binding of uPA may facilitate the infiltration of granulocytes into a fibrin clot, a process that might add to thrombolysis in vivo.

Preparation and storage in Plasma-Lyte A of platelets collected with the cell separator CS3000 Plus equipped with the PLT30-separation and TNX6 collection chambers

The last five years have been characterized by the presentation of new cell separators the main task of which is the collection of high yield-high quality platelets. The CS3000 is an old apparatus which has undergone rejuvenation to sustain the assault of its new competitors. The CS3000 Plus Omnix system is the latest version to be offered along with a combination of TNX-6 separation/PLT30 collection chambers for optimal platelet collection. In this paper we present our results with this apparatus and configuration after its adaptation to the collection and storage of platelets in a non-plasma medium, the Baxter Plasma-Lyte A. After separation the platelet product (PC) was left in the collection chamber and resuspended with 200 ml of Plasma-Lyte A instead of being resuspended in autologous plasma as usual. Plasma was collected in a separate bag (400-450 ml) for transfusion or fractionation purposes. PC quality was assessed by evaluating the platelet yield (4.17 +/- 1.8 x 10(11), and the WBC contamination (4.8 +/- 2.6 x 10(5)). The presence of platelet aggregates (platelet count after aggregate fixation with formalin/platelet count after disaggregation in EDTA), the aggregation induced by ADP, collagen and ristocetin, the hypotonic shock response and the stability of membrane glycoproteins (CD 62 - 62 - 63 - 36- 42b - 51) were measured in the preapheresis samples and in the PC immediately after, 24 and 72 hours after collection. These results were totally satisfactory as was the post-transfusion survival measured as corrected count increment in 10 transfusions to non refractory patients.(ABSTRACT TRUNCATED AT 250 WORDS)

Quality of washed salvaged red blood cells during total hip replacement: a comparison between the use of heparin and citrate as anticoagulants

A randomized, prospective study comparing heparin with citrate (ACD) as anticoagulant during red blood cell saving was performed in 10 ASA grade I-II patients undergoing primary total hip replacement. Blood samples were taken before and after surgery and at several steps during cell saving. In the heparin group, salvaged red cells showed normal values, with the exception of decreased filtrability and moderate hemolysis. More differences in red cell quality were found in the ACD group. Mean corpuscular volume was higher (110 vs 95 x 10(-12) mL), red cell distribution was increased (17% vs 13%), osmotic resistance was lower (0.54 vs 0.43 g NaCl/L at 50% hemolysis), antioxidative reserve capacity was lower (1.9 vs 4.6 U glutathione reductase per gram of hemoglobin) and there was more hemolysis (15% vs 11%). Despite the small volume of autologous blood retransfused (388 +/- 92 mL), the differences in vitro produced significantly higher free hemoglobin levels in the patients' plasma at the end of the operation (58 vs 23 mg/dL). We conclude that heparin is preferable to citrate as an anticoagulant during autotransfusion with cell washing and immediate retransfusion.

The correlation between donor characteristics and the success of human islet isolation

Clinical islet allotransplantation is dependent on the ability to achieve a high yield and purity of islets isolated from human cadaver pancreas donors. The aim of this study was to determine the factors influencing the pancreas prior to islet isolation that may alter yield and purity. The results of 50 consecutive islet isolations from cadaver donor human pancreati at the University of Chicago Medical Center from December 1991 to April 1993 were analyzed. All pancreati were first offered for whole pancreas transplantation before being considered for islet isolation. Human pancreatic islet isolation was accomplished by a modified automated method. Some islet isolations resulted in a high islet yield but low islet purity. Other resulted in well-purified islets, but a low yield. Arbitrarily, successful islet isolation is defined as that yielding over 250,000 islet equivalents (EQN) with a purity of at least 80%. The success rate of human pancreatic islet isolation was 70%. The mean final islet yield obtained from these 50 pancreati was 300,000 +/- 131,000 islet EQN. The mean purity of the final preparation was 73% +/- 25%. By univariate analysis, five factors were found to affect significantly the yield, purity, or overall success rate of islet isolation: organ cold ischemic time, donor age, donor plasma glucose levels, donor body weight, and cause of donor death. Even when islet isolation was successful, the function of islets from hyperglycemic and older donors appear to be impaired both in vitro and in vivo. These results suggest that islet yield and purity are affected by multiple donor-related factors. Even when adequate yield and purity are obtained, islet function is also dependent on donor variables.

Comparison of plateletpheresis with a standard and an improved collection device

A blood cell separator with a specialized separation chamber ([TNX-6]CS-3000 Plus) was developed for the collection of platelet concentrates with higher platelet yields and lower white cell contamination than obtained with the standard blood cell separator (CS-3000). To compare these devices, normal donors were scheduled for paired plateletpheresis procedures spaced 4 weeks apart, with one procedure using the CS-3000 Plus and the other using the CS-3000. Overall, the platelet yield per unit (mean +/- SEM) was 4.3 +/- 0.1 x 10(11) with the CS-3000 Plus versus 3.7 +/- 0.1 x 10(11) with the CS-3000 (p < 0.001), and the white cell contamination per unit (mean +/- SEM) with the former was 2.4 +/- 0.7 x 10(6) versus 84.1 +/- 21.1 x 10(6) with the latter (p < 0.001). The sequence of procedures (i.e., the order in which the devices were paired) was selected randomly, and similar results were found regardless of sequence. When donors with predonation platelet counts of > or = 200 x 10(9) per L (n = 21) were studied separately, 76 percent of the collections by the CS-3000 Plus contained > or = 4 x 10(11) platelets versus 34 percent of those by the CS-3000 (p < 0.01), and 93 percent of the collections by the former contained < 5 x 10(6) white cells (69% contained < 1 x 10(6)) versus 0 percent of those by the latter (p < 0.01). Thus, platelet collections with the TNX-6 chamber consistently demonstrated high platelet yields and strikingly low white cell contamination--qualities that justify converting standard devices to devices with a TNX-6 chamber.

Validation of an acrosomal stain for equine sperm that differentiates between living and dead sperm

An acrosomal staining technique that can differentiate between living and dead sperm was developed for equine sperm. The fluoresceinated lectin Pisum sativum agglutinin (FITC-PSA) was used to identify the presence or absence of acrosomal contents, while the supravital nuclear dye Hoechst 33258 (H258) was used to assess viability. The accuracy of the FITC-PSA acrosomal stain was tested by comparing the percentage of sperm that had lost their acrosomal contents, detected by the staining method, with that detected by transmission electron microscopy (TEM). Following capacitation in vitro, the acrosomal status of sperm induced to acrosome react with A23187 and of control sperm were very similar with the staining technique and TEM, confirming the accuracy of the FITC-PSA acrosomal stain. We investigated the relationship between viability as measured by exclusion of H258 and motility as measured by three methods: one subjective and two objective. Although there was a good correlation between viability and motility as measured by all three methods (r = 0.88, 0.85, 0.75), there was always a proportion of viable sperm that were nonmotile. The physiology of the viable, nonmotile sperm was further investigated by comparing for individual sperm the viability as measured by exclusion of H258 with the mitochondrial function as measured by rhodamine 123. A good correlation (r = 0.99) was found to exist between viability and mitochondrial function, indicating that viable, nonmotile sperm possess functional mitochondria and confirming the ability of supravital staining to distinguish between living and dead sperm. We determined that 29-81% of the sperm in semen that had lost their acrosomal contents were in fact dead. Thus, this acrosomal staining technique can provide more relevant endpoints for future investigations of capacitation, the acrosome reaction, and sperm handling techniques in the horse.

Multicenter study of standardization of cell counting. Haemapheresis Scientific Workshop Group of DGTI

Multicenter studies on cell separators give valid data (which can be compared between the different centers) only if the cell counting methods are uniform. This has to be demonstrated by ring studies or multicenter counting studies. Twelve apheresis centers involved in a multicenter study for the evaluation of the Fresenius AS 104 cell separator participated in such a ring study from July 1990 to July 1991. The twelve participating centers split into three significantly different groups according to the platelet counts in the platelet concentrates and a calculated pseudo extraction efficiency. No differences could be found in the white and red blood cell counts. No mailing effect--or time effect--and no personal effect could be found in the reference center.

Fetal cells in the maternal circulation

The analysis of fetal cells from the maternal circulation would be the least invasive method of prenatal diagnosis. Potential fetal cell types to enter the maternal circulation are lymphocytes, trophoblast cells and nucleated erythrocytes. With conventional methods, such as cytology and interphase or metaphase cytogenetics, the ratio of fetal to maternal cells was overestimated in the past. Currently most groups use polymerase chain reaction-based Y-sequence analysis for the detection of fetal cells in pregnancies with male fetuses, either with or without prior enrichment of fetal cells. For fetal cell separation, fluorescence-activated cell sorting and immunomagnetic beads have been applied, and recently our group has used discontinuous density gradient centrifugation for this purpose. We have shown that the transferrin receptor antigen alone is not sufficient for enrichment of fetal nucleated erythrocytes. Despite some initial promising results with fluorescence in situ hybridization, the reproducibility and reliability of the techniques are still limited, mainly due to the lack of very specific cell markers and the very low and variable concentrations of fetal cells among numerous maternal cells.