Characterization, isolation, and culture of spermatogonial stem cells in Macaca fascicularis

Spermatogonial stem cells (SSCs) have great applications in both reproductive and regenerative medicine. Primates including monkeys are very similar to humans with regard to physiology and pathology. Nevertheless, little is known about the isolation, the characteristics, and the culture of primate SSCs. This study was designed to identify, isolate, and culture monkey SSCs. Immunocytochemistry was used to identify markers for monkey SSCs. Glial cell line-derived neurotrophic factor family receptor alpha-1 (GFRA1)-enriched spermatogonia were isolated from monkeys, namely Macaca fascicularis (M. fascicularis), by two-step enzymatic digestion and magnetic-activated cell sorting, and they were cultured on precoated plates in the conditioned medium. Reverse transcription-polymerase chain reaction (RT-PCR), immunocytochemistry, and RNA sequencing were used to compare phenotype and transcriptomes in GFRA1-enriched spermatogonia between 0 day and 14 days of culture, and xenotransplantation was performed to evaluate the function of GFRA1-enriched spermatogonia. SSCs shared some phenotypes with rodent and human SSCs. GFRA1-enriched spermatogonia with high purity and viability were isolated from M. fascicularis testes. The freshly isolated cells expressed numerous markers for rodent SSCs, and they were cultured for 14 days. The expression of numerous SSC markers was maintained during the cultivation of GFRA1-enriched spermatogonia. RNA sequencing reflected a 97.3% similarity in global gene profiles between 0 day and 14 days of culture. The xenotransplantation assay indicated that the GFRA1-enriched spermatogonia formed colonies and proliferated in vivo in the recipient c-KitW/W (W) mutant mice. Collectively, GFRA1-enriched spermatogonia are monkey SSCs phenotypically both in vitro and in vivo. This study suggests that monkey might provide an alternative to human SSCs for basic research and application in human diseases.

Nonspecific probe binding and automatic gating in flow cytometry and fluorescence activated cell sorting (FACS)

Flow cytometry is extensively used in cell biology to differentiate cells of interest (mutants) from control cells (wild-types). For mutant cells characterized by expression of a distinct membrane surface structure, fluorescent marker probes can be designed to bind specifically to these structures while the cells are in suspension, resulting in a sufficiently high fluorescence intensity measurement by the cytometer to identify a mutant cell. However, cell membranes may have relatively weak, nonspecific binding affinity to the probes, resulting in false positive results. Furthermore, the same effect would be present on mutant cells, allowing both specific and nonspecific binding to a single cell. We derive and analyze a kinetic model of fluorescent probe binding dynamics by tracking populations of mutant and wild-type cells with differing numbers of probes bound specifically and nonspecifically. By assuming the suspension is in chemical equilibrium prior to cytometry, we use a two-species Langmuir adsorption model to analyze the confounding effects of non-specific binding on the assay. Furthermore, we analytically derive an expectation maximization method to infer an appropriate estimate of the total number of mutant cells as an alternative to existing, heuristic methods. Lastly, using our model, we propose a new method to infer physical and experimental parameters from existing protocols. Our results provide improved ways to quantitatively analyze flow cytometry data.

Rmax: A systematic approach to evaluate instrument sort performance using center stream catch

Sorting performance can be evaluated with regard to Purity, Yield and/or Recovery of the sorted fraction. Purity is a check on the quality of the sample and the sort decisions made by the instrument. Recovery and Yield definitions vary with some authors regarding both as how efficient the instrument is at sorting the target particles from the original sample, others distinguishing Recovery from Yield, where the former is used to describe the accuracy of the instrument's sort count. Yield and Recovery are often neglected, mostly due to difficulties in their measurement. Purity of the sort product is often cited alone but is not sufficient to evaluate sorting performance. All of these three performance metrics require re-sampling of the sorted fraction. But, unlike Purity, calculating Yield and/or Recovery calls for the absolute counting of particles in the sorted fraction, which may not be feasible, particularly when dealing with rare populations and precious samples. In addition, the counting process itself involves large errors. Here we describe a new metric for evaluating instrument sort Recovery, defined as the number of particles sorted relative to the number of original particles to be sorted. This calculation requires only measuring the ratios of target and non-target populations in the original pre-sort sample and in the waste stream or center stream catch (CSC), avoiding re-sampling the sorted fraction and absolute counting. We called this new metric Rmax, since it corresponds to the maximum expected Recovery for a particular set of instrument parameters. Rmax is ideal to evaluate and troubleshoot the optimum drop-charge delay of the sorter, or any instrument related failures that will affect sort performance. It can be used as a daily quality control check but can be particularly useful to assess instrument performance before single-cell sorting experiments. Because we do not perturb the sort fraction we can calculate Rmax during the sort process, being especially valuable to check instrument performance during rare population sorts.

Filtration parameters influencing circulating tumor cell enrichment from whole blood

Filtration can achieve circulating tumor cell (CTC) enrichment from blood. Key parameters such as flow-rate, applied pressure, and fixation, vary largely between assays and their influence is not well understood. Here, we used a filtration system, to monitor these parameters and determine their relationships. Whole blood, or its components, with and without spiked tumor cells were filtered through track-etched filters. We characterize cells passing through filter pores by their apparent viscosity; the viscosity of a fluid that would pass with the same flow. We measured a ratio of 5·10(4)∶10(2)∶1 for the apparent viscosities of 15 µm diameter MDA-231 cells, 10 µm white cells and 90 fl red cells passing through a 5 µm pore. Fixation increases the pressure needed to pass cells through 8 µm pores 25-fold and halves the recovery of spiked tumor cells. Filtration should be performed on unfixed samples at a pressure of ∼10 mbar for a 1 cm(2) track-etched filter with 5 µm pores. At this pressure MDA-231 cells move through the filter in 1 hour. If fixation is needed for sample preservation, a gentle fixative should be selected. The difference in apparent viscosity between CTC and blood cells is key in optimizing recovery of CTC.

Diffraction Phase Cytometry: blood on a CD-ROM

We demonstrate Diffraction Phase Cytometry (DPC) as a single shot, full-field, high throughput quantitative phase imaging modality, dedicated to analyzing whole blood smears. Utilizing a commercial CD as a sample substrate, along with dynamic spatial filtering via a liquid crystal spatial light modulator, we have developed a compact instrument capable of making quantitative, physiologically relevant measurements. To illustrate the ability of the system to function as a highly sensitive cytometer we imaged a large number (N=1,537) of live human erythrocytes in whole blood without preparation. We retrieved a comprehensive set of geometrical parameters including cell volume and surface area, which are not directly available using existing cytometers. Furthermore, we retrieved the minimum cylindrical diameter, through which red blood cells can pass, and deliver oxygen. These initial results prove the concept for an inexpensive lab-on-a-chip blood screening device.

Effects of magnetic-activated cell sorting on sperm motility and cryosurvival rates

OBJECTIVE

To evaluate the effect of magnetic-activated cell sorting in cryopreservation-thawing protocols on sperm motility and cryosurvival rate.

DESIGN

Prospective-controlled study.

SETTING

Andrology department at a university-based medical institution.

PATIENT(S)

Ten healthy volunteer sperm donors.

INTERVENTION(S)

Sperm populations were separated using annexin-V magnetic-activated cell sorting before and after the cryopreservation-thawing process.

MAIN OUTCOME MEASURE(S)

Sperm motility and cryosurvival rate.

RESULT(S)

Annexin-negative sperm separated by magnetic-activated cell sorting had statistically significantly higher motility following cryopreservation-thawing than sperm that were not separated. Similarly, annexin-negative spermatozoa also had higher cryosurvival rate than sperm cryopreserved without magnetic-activated cell sorting and sperm that were annexin-positive.

CONCLUSION(S)

Superparamagnetic annexin V-conjugated microbeads can separate spermatozoa with externalized phosphatidylserine, which is considered one of the early features of late apoptosis. The separation of a distinctive population of nonapoptotic spermatozoa with intact membranes may optimize the cryopreservation-thawing outcome. Magnetic-activated cell sorting using annexin-V microbeads enhances sperm motility and cryosurvival rates following cryopreservation.

Quantification of immunosuppression by flow cytometry in stable renal transplant recipients

The current standard of monitoring transplant patients by drug levels is not optimal because it does not take into account the different and individual effects of immunosuppressive drugs on each patient. In this study, the authors tested immune function assays for monitoring transplant patients. Blood was collected from stable renal transplant patients treated with cyclosporin, mycophenolate mofetil, and prednisone (n = 8), and from healthy volunteers (n = 12). Lymphocyte proliferation, expression of T-cell surface activation antigens (CD25, CD71, CD11a, CD95, CD154), production of intracellular cytokines (IL-2, INFgamma, TNFalpha), and lymphocyte subsets (CD4, CD8, CD16, CD20) were assessed by flow cytometry. Lymphocyte proliferation, expression of T-cell surface activation antigens, and production of intracellular cytokines were significantly decreased in transplant recipients compared with healthy control volunteers. The combined effects of several immunosuppressive drugs in renal transplant recipients can be quantitated with immune function assays in whole blood. This new method may be helpful to achieve an optimal level of immunosuppression for each patient.

Limited efficacy of universal leucodepletion in reducing the incidence of febrile nonhaemolytic reactions in red cell transfusions

This article demonstrates a 62% reduction in the number of febrile nonhaemolytic transfusion reactions (FNHTRs) and 50% reduction in febrile reaction rate associated with red cell transfusions following graded introduction of universal leucodepletion. Though this is a statistically significant reduction (P = 0.009), it shows limited efficacy in abrogating this complication. We also found a reduction in the proportion of cases of FNHTRs with lymphocytotoxic antibodies over the period studied from 54% in 1998, 28% in 1999 to 23% in 2000. This corresponds to a relative increase in the number of febrile reactions without human leucocyte antigen (HLA) antibodies following full implementation of universal leucodepletion, as the total number of reported reactions actually fell considerably during the period. The increase in the number of cases without HLA antibodies was directly proportional to the increase in the number of leucodepleted units used.

Improved methods for the isolation and purification of porcine islets

Recent progress in human islet transplantation demonstrates the feasibility of using purified human islets for treatment of type 1 diabetes mellitus; however, a shortage of human pancreata remains a major obstacle. This report describes methods to isolate porcine islets using a modification of the automated chamber method. The pancreata from 2-year-old sows were trimmed and injected intraductally with Sevac, Sigma, or Liberase PI collagenase. The pancreata was placed in the chamber, shaken, and recirculated at 70 ml/min until an adequate number of islets were liberated. The digest was centrifuged and the pellets pooled with University of Wisconsin Solution + 10% horse serum and incubated at 4 degrees C for 1 h. The islets were purified using a continuous gradient of Hypaque Euroficoll on a refrigerated COBE 2991. The islets were collected in fractions, assessed for purity, sized, and then suspended in Medium 199. Collagenase preparations obtained from Sevac (2919 islet equivalents [IE]/g), Sigma (2543 IE/g), and Liberase PI (2901 IE/g) gave similar results with 94%-95% purity. In summary, we report a successful method for efficient isolation and purification of porcine islets, yielding nearly 3000 IE/gm, with different collagenase products.

Simultaneous differentiation and quantitation of erythroblasts and white blood cells on a high throughput clinical haematology analyser

After the neonatal period, the presence of nucleated red blood cells (NRBC) in peripheral blood is indicative of pathology. Despite the clinical utility of such measurements, automated NRBC counting has hitherto not been available on routine automated blood cell counting analysers. To address this, an automated method for the analysis of NRBC was developed and incorporated into the Abbott Cell Dyn 4000 (CD4000) haematology analyser. The system white blood cell (WBC) reagent was specifically formulated to preserve concomitantly white blood cell (WBC) morphology, rapidly lyse red blood cell and NRBC membranes, and subsequently stain NRBC nuclei with a nucleotide specific fluorochrome dye (Kim et al. 1996a). The fluorochrome itself does not permeabilize the membrane of intact viable white blood cells. The sample is processed by flow cytometry and the signals generated from an argon-ion laser light source are analysed. Axial light loss (AxLL), intermediate angle light scatter (IAS) and red fluorescence (FL3) are used to discriminate between particles of various types. By using these discriminators in a three-dimensional approach, NRBC from a discrete cluster which can easily be separated from leucocytes and enumerated as a distinct cell population during the optical WBC differential analysis. Consequently, accurate absolute WBC counts and differentials can be obtained even in the presence of NRBC. Background 'noise' (both fluorescent and non-fluorescent) from platelets. Howell-Jolly bodies, basophilic stippling, RNA from lysed reticulocytes, and DNA from leucocyte and megakaryocytic fragments are essentially eliminated (Kim et al. 1996b). While the membranes of intact and viable leucocytes remain impermeable to the passage of the fluorochrome stain, leucocytes with damaged membranes are permeable to the dye and generate FL3+ signals. Such cells, which are commonly seen as a consequence of sample ageing as well as in some distinctive pathologies, are identified by the algorithm (using their AxLL signal size) and are labelled as non-viable. Moreover, because non-viable leucocytes are retained in the WBC count and differential analyses, the CD4000 is further able to provide both numerical and graphical data regarding the relative frequency of viable and non-viable components. This additional information can serve as valuable 'decision-drivers' in the laboratory data review process.

Theoretical basis for sampling statistics useful for detecting and isolating rare cells using flow cytometry and cell sorting

This paper describes new approaches to calculating the number of cells that need to be processed using flow cytometry (FCM) techniques and the subsequent time required in order to isolate a specific number of cells having selected characteristics. The methods proposed use probabilistic assumptions about the contents of the sample to be sorted, logarithmic/exponential transformations to avert the computer "underflow" and "overflow" limitations of brute force calculations for the parameters of the binomial distribution imposed by existing computer hardware, and an established mathematical procedure for calculating error bounds for the normal approximation to the binomial distribution. Estimates are derived for the total number of cells in the FCM sample volume that must be available for processing and, for given FCM cell sorting decision speeds, the total elapsed times necessary to conduct particular experiments. The proposed approach obviates the need to resort to calculation expediencies such as the theoretically limited Poisson approximation for what can be considered a Bernoulli process mathematically characterized by the binomial distribution. Tables and graphs illustrate the projected times required to complete FCM experiments as a function of "effective" cell sorting decision speeds. Results from this paper also demonstrate that, as the "effective" cell sorting decision speed increases, there may not be a corresponding linear decrease in the time required to sort a given number of cells with selected statistical properties. The focus of this paper is on the use of innovative mathematical techniques for the design of experiments involving rare cell sorting. However, these same computational approaches may also prove useful for the high-speed enrichment sorting of non-rare cell subpopulations.

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.

Improvement of separation efficiency and concentrate purity of the Fresenius cell separator AS 104: results of a multicenter study. Haemapheresis Scientific Workshop Group of DGTI

The aim of this multicenter study, initiated by the Haemapheresis Scientific Workshop Group of the DGTI was to evaluate separation protocols for the cell separator AS 104, marketed by Fresenius, using modified software and parameters which were believed to allow a more effective platelet collection with a significantly lower leukocyte contamination of the concentrates. Plateletpheresis data from 950 runs in ten hemapheresis centers, using virtually the same equipment, identical pheresis protocols, and cell counting methods were registered and statistically analyzed for each center and machine-related differences. Additionally, the counting methods of the centers were controlled by bi-weekly external cell count trials, and the plateletpheresis data were corrected using the results of these cell count trials, to obtain a comparison of the two versions of the protocol independent of the center effect. For protocol (or software version) 4.1, 610 runs were registered. The results of cell countings (chamber) are (given as means+/-standard deviations) 3.452x10 11+/-1.009x10 11 for the platelet yield (or thrombocyte yield), 9x10 6+/-23x10 8 for leukocyte contamination, and 17x10 6+/-70x10 6 for the erythrocyte contamination, and 53%+/-13.5% for the extraction efficiency, respectively. For software version 4.4 with 340 runs, the results are 3.642x10 11+/-0.974x10 11 for the platelet yield, 15x10 6+/-74x10 8 for leukocyte contamination, 20x10 6+/-44x10 6 for erythrocyte contamination, and 59%+/-12.4% for the extraction efficiency, respectively. For the leukocyte and erythrocyte contaminations, the means and standard deviations must be interpreted carefully since the statistical distribution showed a considerable skewing of the data. From the automatic counts, marginally smaller means were found. The data were corrected by the values from the ring study; and for these mathematically corrected data, statistical tests showed a significant improvement in the extraction efficiency from software version 4.1 to 4.4. At the same time, the leukocyte contamination was significantly lower with version 4.4.