Direct volumetric flow cytometric quantitation of CD34+ stem and progenitor cells

True volumetric counting of CD34+ cells using flow cytometry

While the single-platform flow cytometric CD34+ cell counting method is the preferred choice to predict the yield of mobilized peripheral blood stem cells, most flow cytometers lack the ability of hematology counter analyzers to perform volumetric counting. However, one of the problems using reference microbeads is the vanishing counting bead phenomenon. This phenomenon results in a drop in microbeads concentration and reduces the total and relative number of beads in calibration procedures. In the last years, flow cytometers including a volumetric system to quantify cells have been developed and may represent a promising alternative to enumerate CD34+ cells avoiding the use of beads. In this study we have used a direct true volumetric counting of CD34+ cells under continuous flow pump to overcome potential drawbacks with impact in rare cell analysis. To confirm this hypothesis, we have compared the results of CD34+ cell enumeration using non-volumetric vs. volumetric systems with FC500 (Beckman Coulter) and Attune NxT (ThermoFisher) flow cytometers, respectively, in mobilized peripheral blood samples. No statistically significant differences were observed between measurements of CD34+ cells using beads, when the FC500 and Attune NxT absolute counting values were compared, or when CD34+ counts were compared on the Attune NxT, either using or not using beads. Linear regressions to study the relationship between volumetric and non-volumetric CD34+ counts confirmed the accuracy of each method. Bland-Altman test showed agreement between both methods. Our data showed that CD34+ cell enumeration using a volumetric system is comparable with current counting systems. This method represents an alternative with the advantage of the simplification of sample preparation and the reduction of the analysis subjectivity.

Validation of the single-platform ISHAGE protocol for enumeration of CD34+ hematopoietic stem cells in umbilical cord blood in a Brazilian center

Background

This study aims to validate the single-platform method for enumeration of CD34+ cells, by comparing the performance of two different commercial kits, as well as to evaluate the efficiency of the Accuri^TM C6 cytometer in providing direct counts of absolute cell numbers.

Method

We evaluated 20 samples from umbilical cord blood (UCB), comparing the two different methodologies for enumeration of CD34+ cells: single and dual-platform. For the assessment of the single-platform, Procount and SCE kits were used, both of which use fluorescent beads as a counting reference to obtain absolute CD34+ cells numbers. Moreover, after the acquisition of samples in flow cytometer Accuri^TM C6, following the protocol established for each kit, the number of CD34+ cells was recalculated, considering the cell count provided by the Accuri^TM C6.

Main Results

In our analysis, the results showed a strong correlation between the number of CD34+ cells/μL (r² = 0.77) when comparing the SCE kit and the current dual-platform method. On the other hand, the comparison between Procount kit and dual-platform results showed a moderate correlation for the number of CD34+/μL cells (r² = 0.64).

Conclusion

Our results showed that the Accuri^TM C6 flow cytometer can be used safely, applying both the dual and single platform analysis strategy. Considering the ISHAGE protocol-based single-platform approach, as the most appropriate methodology for CD34+ cells enumeration, our results demonstrated that the SCE kit has great potential for national standardization of UCB samples analysis methodology.

Comparison of Volumetric and Bead-Based Counting of CD34 Cells by Single-Platform Flow Cytometry

Background

Over 2,000 people a year in the United Kingdom need a bone marrow or blood stem cell transplant. It is important to accurately quantify the hematopoietic stem cells to predict whether the transplant will be successful in replenishing the immune system. However, they are present at low frequency, which complicates accurate quantification. The current gold standard method is single‐platform flow cytometry using internal reference counting beads to determine the concentration of CD34 cells. However, volumetric flow cytometers have the ability to measure the acquisition volume, which removes the need for reference beads for calculation of cell concentrations.

Method

In this study, we compared both methods for calculating CD34 cell concentrations in volumetric cytometers, using either the volume reading or the number of reference beads for calculation. In addition, the uncertainty of measurement for each method was estimated.

Results

The results show that both methods have similar uncertainties of measurement. Regression analysis showed low to no statistical difference in CD34 cell concentrations obtained with each method.

Conclusions

Overall, this study suggests that the volumetric method is a valid approach but that the adoption of this technology may be hindered without some form of external calibration of volume readings to increase confidence in the measurement. © 2019 The Authors. Cytometry Part B: Clinical Cytometry published by Wiley Periodicals, Inc. on behalf of International Clinical Cytometry Society.

Evaluation of an easy and affordable flow cytometer for volumetric haematopoietic stem cell counting

BACKGROUND

Accurate estimation of haematopoietic stem cell (HSC) counts by flow cytometry may be difficult in laboratories in which sophisticated equipment and staff with specific expertise are not available. Affordable flow cytometers that can perform basic functions may help to overcome these difficulties. In this study we compared HSC and leucocyte counts determined by volumetric and bead-based protocols performed with the small, low-cost Accuri(®) C6, with those obtained with two gold-standard instruments, the four-colour FACSCalibur(®) and the eight-colour FACSCantoII(®), our reference flow cytometers.

MATERIALS AND METHODS

With the three cytometers we tested, in parallel, 111 consecutive samples from cord blood, peripheral blood from patients with myelofibrosis and myeloproliferative syndromes, fresh and thawed HSC collected by apheresis and bone marrow products. The findings were compared with one-way ANOVA, Bland-Altman analysis and linear regression.

RESULTS

The results of HSC and leucocyte enumeration by the three devices were strongly correlated (r(2)>0.99; p<0.0001). ANOVA performed on different subgroups of samples did not reveal significant differences between HSC count determined by the C6 bead-based and reference flow cytometers in any of the subgroups. Regarding the C6 volumetric protocol, a statistically significant difference was observed only in the cord blood subgroup. Time for instrument set-up, calibration and analysis was slightly longer with Accuri(®) C6 (40 min) than with FACSCantoII(®) (30 min).

DISCUSSION

Accuri(®) C6 is a reliable instrument for HSC enumeration in fresh samples, using both volumetric and bead-based approaches, although the volumetric protocol on cord blood samples needs to be improved. The Accuri(®) C6 is easy to use, does not require profound knowledge of flow cytometry and could be employed in an urgent setting. Its performance may be improved by more efficient calibration and shorter analysis time.

Bone marrow-derived mesenchymal stem cells increase dopamine synthesis in the injured striatum

Previous studies showed that tyrosine hydroxylase or neurturin gene-modified cells transplanted into rats with Parkinson’s disease significantly improved behavior and increased striatal dopamine content. In the present study, we transplanted tyrosine hydroxylase and neurturin gene-modified bone marrow-derived mesenchymal stem cells into the damaged striatum of Parkinson’s disease model rats. Several weeks after cell transplantation, in addition to an improvement of motor function, tyrosine hydroxylase and neurturin proteins were up-regulated in the injured striatum, and importantly, levels of dopamine and its metabolite 3,4-dihydroxyphenylacetic acid increased significantly. Furthermore, the density of the D2 dopamine receptor in the postsynaptic membranes of dopaminergic neurons was decreased. These results indicate that transplantation of tyrosine hydroxylase and neurturin gene-modified bone marrow-derived mesenchymal stem cells increases dopamine synthesis and significantly improves the behavior of rats with Parkinson’s disease.