The effect of CD34 count and clonogenic potential of hematopoietic stem cells on engraftment

DNA contamination within recombinant adeno-associated virus preparations correlates with decreased CD34+ cell clonogenic potential

Recombinant adeno-associated viruses (rAAV) are promising for applications in many genome editing techniques through their effectiveness as carriers of DNA homologous donors into primary hematopoietic stem and progenitor cells (HSPCs), but they have many outstanding concerns. Specifically, their biomanufacturing and the variety of factors that influence the quality and consistency of rAAV preps are in question. During the process of rAAV packaging, a cell line is transfected with several DNA plasmids that collectively encode all the necessary information to allow for viral packaging. Ideally, this process results in the packaging of complete viral particles only containing rAAV genomes; however, this is not the case. Through this study, we were able to leverage single-stranded virus (SSV) sequencing, a next-generation sequencing-based method to quantify all DNA species present within rAAV preps. From this, it was determined that much of the DNA within some rAAV preps is not vector-genome derived, and there is wide variability in the contamination by DNA across various preps. Furthermore, we demonstrate that transducing CD34+ HSPCs with preps with higher contaminating DNA resulted in decreased clonogenic potential, altered transcriptomic profiles, and decreased genomic editing. Collectively, this study characterized the effects of DNA contamination within rAAV preps on CD34+ HSPC cellular potential.

Gestational Diabetes Mellitus in Pregnancy Increased Erythropoietin Level Affecting Differentiation Potency of Haematopoietic Stem Cell of Umbilical Cord Blood

Background: The in utero environment has many factors that can support cell differentiation. Cytokines, chemokines and growth factors play big roles in haematopoietic mechanisms. Some diseases like gestational diabetes mellitus (GDM) might affect the environment and haematopoietic stem cell (HSC) quality. The aim of this study is to investigate the adverse effects of GDM on umbilical cord blood (UCB) HSC in terms of differentiation potency including the UCB parameters used for banking and transplantation purposes. Methods: UCB-HSC was collected from 42 GDM and 38 normal pregnancies. UCB-HSC was isolated and further enriched using immuno-magnetic separation beads (MACS). The UCB-HSC were cultured in methylcellulose media to investigate the differentiation potency. The level of erythropoietin (EPO) and insulin in the UCB plasma was measured using enzyme linked immunoassay (ELISA) technique. Result: The UCB parameters; volume, total nucleated count (TNC) and total CD34+ cells were significantly reduced in the GDM group compared to the control group. The number of HSC progenitors' colonies were significantly reduced in the GDM group except for progenitor BFU-E, which was significantly increased (GDM = 94.19 ± 6.21, Control = 73.61 ± 2.73, p = 0.010). This data was associated with higher EPO level in GDM group. However, the insulin level in the GDM group was comparable to the Control group. Conclusion: Our results suggest that the changes in the in utero environment due to abnormalities during pregnancy such as GDM might affect the differentiation potency of UCB-HSC. These findings can be considered as an additional parameter for the inclusion and exclusion criteria for UCB banking, particularly for mothers with GDM.

Preeclampsia in pregnancy affecting the stemness and differentiation potency of haematopoietic stem cell of the umbilical cord blood

BACKGROUND

Umbilical cord blood (UCB) has been proposed as the potential source of haematopoietic stem cells (HSC) for allogeneic transplantation. However, few studies have shown that a common disease in pregnancy such as preeclampsia would affect the quality of UCB-HSC. Total nucleated cell count (TNC) is an important parameter that can be used to predict engraftment including UCB banking. Colony forming unit (CFU) assay is widely used as an indicator to predict the success of engraftment, since direct quantitative assay for HSC proliferation is unavailable. The aim of this study is to investigate the effects of preeclampsia in pregnancy on the stemness and differentiation potency of UCB-HSC.

METHODS

Mononuclear cells (MNC) were isolated from UCB and further enriched for CD34+ cells using immune-magnetic method followed by CFU assay. A panel of HSC markers including differentiated haematopoietic markers were used to confirm the differentiation ability of UCB-HSC by flow cytometry analysis.

RESULTS/ DISCUSSION

The HSC progenitor's colonies from the preeclampsia group were significantly lower compared to the control. This correlates with the low UCB volume, TNC and CD34+ cells count. In addition, the UCB-enriched CD34+ population were lymphoid progenitors and capable to differentiate into natural killer cells and T-lymphocytes.

CONCLUSION

These findings should be taken into consideration when selecting UCB from preeclamptic mothers for banking and predicting successful treatment related to UCB transplant.

Comparison of the methods evaluating post thawing viability of peripheral blood stem cell graft

OBJECTIVE

Reliable and pratique methods are essential for rapid and accurate determination of post thawing viability of peripheral blood stem cell (PBSC) graft before hematopoietic stem cell transplantation. In this study, Trypan Blue (TP) Eosin Y (EO), and Acridine-orange-ethidium bromide (AO/EB), which are of the methods commonly used for the assessment of viability in clinic practice, were compared with the flow cytometry-7AAD (7AAD) method, which is a more sensitive method. The aim of this study is to examine which method evaluates postthawing viability in a more compatible manner with 7AAD.

MATERIALS-METHODS

Postthawing viability rates were examined simultaneously by means of four different methods before hematopoietic stem cell transplantation in a total of 20 PBSC graft. The results obtained from the AO/EB, TP, EO methods were evaluated with the flow cytometry-7AAD in terms of concordance.

RESULTS

The AO / EB was determined to be the method having the best concordance with the flow cytometry-7AAD method. Although, at a lower level compared to the AO/EB method, the EO method had a statistically significant concordance with the flow cytometry-7AAD method. No statistically significant concordance was detected between the TP method and 7AAD method in terms of viability results.

CONCLUSION

The AO/EB method was identified to be the method having the best compatibility with the flow cytometry -7AAD method in showing the viability of the cryopreserved PBSC graft. In the viability assessment of PBCS graft using light microscopy, the EO may be preferred since is more sensitive compared to the TP method.

Quantifying loss of CD34+ cells collected by apheresis after processing for freezing and post-thaw

INTRODUCTION

CD34(+) cells collected for autologous bone marrow transplantation (BMT) are usually quantified in the apheresis product after collection, but the necessity to repeat these measures post-thaw is controversial.

METHODS

We examined the loss of CD34(+) cells after collection, preparation for freezing and post-thaw in apheresis products collected for BMT.

RESULTS

Median number of CD34(+) cells collected per unit was 1.61×10(6)/kg, viability: 97-100%. This number decreased to 1.38×10(6)/kg, viability: 96-100% before freezing and was 1.17×10(6)/kg post-thaw. Viability decreased to 86-98%. The relative loss of viable PBHPC showed an inverse correlation with the ratio "CD34(+) cells/total nucleated cells" (r=-0.45; p=<0.0005). This relative loss was largest in patients with Hodgkin's lymphoma.

CONCLUSION

Cryopreservation and thawing of PBHPCs in leukapheresis products provokes a small but significant stem cell loss. So, quantification of viable CD34(+) cells post-thaw is important, especially in poorly mobilizing patients. Besides, the ratio "CD34(+) cells/total nucleated cells" after leukapheresis is an important parameter for prediction of neutrophil recovery after BMT.