Evaluation of optimal survival of primitive progenitor cells (LTC-IC) from PBPC apheresis products after overnight storage

Evaluation of overnight storage conditions for autologous peripheral blood stem cell products: comparison of three different conditions

BACKGROUND

Overnight (ON) storage of peripheral blood stem cell (PBSC) occurs frequently in clinical settings. However, there are no standard guidelines for optimal storage conditions of freshly harvested PBSC. The aim of this study was to investigate the influence of storage temperatures on the quality of autologous PBSC and establish optimal storage conditions before cryopreservation.

METHODS

A retrospective analysis was performed on 260 PBSC harvests according to pre-cryopreservation conditions: immediate processing or ON storage at room temperature (RT). For direct comparison, 30 autologous PBSC products were collected prospectively and prepared under three different pre-cryopreservation conditions: immediate processing, ON storage at 4°C and ON storage at RT. The recovery of CD34(+) cells, post-thaw CFU-GM count and viability were analysed.

RESULTS

Retrospective analysis revealed that post-thaw CFU-GM count was significantly lower when PBSC were stored ON at RT compared to when immediately processed (136·4 vs. 409·6/μl). Prospective analysis showed a mean recovery of CD34(+) cells of 65·5 ± 25·1%, 70·5 ± 27·4% and 35·9 ± 25·1% for immediate processing, ON storage at 4°C and ON storage at RT, respectively. Similarly, mean viability and CFU-GM counts were significantly reduced when stored ON at RT compared to when immediately processed or stored ON at 4°C (60·4 ± 25·6 vs. 84·1 ± 12·9 vs. 82·7 ± 12·6%, 15·7 ± 25·7 vs. 398·5 ± 906·2 vs. 350·0 ± 847·9/μl, respectively).

CONCLUSIONS

ON storage of autologous PBSC at RT significantly decreased the quality of HPCs. These data indicate that ON storage of autologous PBSC at 4°C would be the most reasonable approach for maintaining the quality of HPCs when immediate processing is not possible.

Low-oxygen and high-carbon-dioxide atmosphere improves the conservation of hematopoietic progenitors in hypothermia

BACKGROUND

During short-term storage of hematopoietic cells (HCs) at 4°C a substantial decline in number and in functional capacity of progenitors occurs after 3 days. We hypothesized that physiologic O2 and CO2 concentrations of hematopoietic tissue microenvironment (approx. 3% O2 and approx. 6% CO2) could improve cell viability and functionality during storage at 4°C.

STUDY DESIGN AND METHODS

Mobilized peripheral blood (PB) CD34+ cells from multiple myeloma or non-Hodgkin's lymphoma patients were stored in flasks containing air (approx. 20% O2 and approx. 0.05% CO2) or 3% O2/6% CO2 atmosphere, for 3, 5, and 7 days at 4°C. The total number of cells, the number of cells in G0 or G1 phase of cell cycle, and the apoptosis rate were determined. The functional capacity of stored cells was assessed by the capacity of progenitors to form colonies in methylcellulose (colony-forming cells [CFCs]) and of stem cells to repopulate the bone marrow (BM) of immunodeficient mice (SCI D-repopulating cell [SRC] assay).

RESULTS

The total number of viable cells and cells in G1 phase as well as the number of total CFCs were significantly higher at 3% O2/6% CO2 than in air at all time points. Cells in G0 phase and SRC were equally preserved in both conditions.

CONCLUSION

Atmosphere with low O2 and high CO2 concentration (3% O2/6% CO2) in hypothermia (+4°C) during 7 days of storage prevents cell damage and preserves a high number of functional HSCs and progenitors mobilized in PB by granulocyte-colony-stimulating factor.

Validation of short-term handling and storage conditions for marrow and peripheral blood stem cell products

BACKGROUND

Allogeneic hematopoietic stem cell transplants from unrelated donors are routinely used in the treatment of patients with hematologic malignancies. These cellular products are often collected off-site and require transport from the collection site to transplantation centers. However, the effects of transport conditions and media on stem cell graft composition during short-term storage have not been well described.

STUDY DESIGN AND METHODS

Five bone marrow (BM), four filgrastim-mobilized peripheral blood stem cell (PBSC), and four nonmobilized peripheral blood mononuclear cell (PBMNC) products were collected from healthy volunteer donors and stored at 4 or 20°C for up to 72 hours in 10% PlasmaLyte A plus anticoagulants such as 10% acid citrate dextran-A (ACD-A) and/or 10 IU/mL heparin. Products were evaluated at 0, 24, 48, and 72 hours for cellular content, viability, and metabolic activities.

RESULTS

BM products maintained equivalent cell viability when stored at either 4 or 20°C over 72 hours, but cell viability was better maintained for PBSC products stored at 4°C. The mean viable CD34+ cell recovery for PBSC and BM products stored over 72 hours at 4°C was higher than 75%. Significantly lower CD34+ cell and colony-forming unit recoveries were seen in PBSC products but not BM products stored at room temperature. Faster lactic acid accumulation was observed in PBMNC and PBSC products stored without ACD-A.

CONCLUSIONS

Seventy-two-hour storage of BM, PBSC, and PBMNC products at refrigerated temperature maintains optimal cell viability and recovery. Anticoagulation with ACD-A is preferred over heparin to reduce lactic acid accumulation in the product media.

Protocols for hematopoietic stem cell expansion from umbilical cord blood

The reconstitution of adult stem cells may be a promising source for the regeneration of damaged tissues and for the reconstitution of organ dysfunction. However, there are two major limitations to the use of such cells: they are rare, and only a few types exist that can easily be isolated without harming the patient. The best studied and most widely used stem cells are of the hematopoietic lineage. Pioneering work on hematopoietic stem cell (HSC) transplantation was done in the early 1970s by ED. Thomas and colleagues. Since then HSCs have been used in allogenic and autologous transplantation settings to reconstitute blood formation after high-dose chemotherapy for various blood disorders. The cells can be easily harvested from donors, but the cell number is limited, especially when the HSCs originate from umbilical cord blood (UCB). It would be desirable to set up an ex vivo strategy to expand HSCs in order to overcome the cell dose limit, whereby the expansion would favor cell proliferation over cell differentiation. This review provides an overview of the various existing HSC expansion strategies-focusing particularly on stem cells derived from UCB-of the parameters that might affect the outcome, and of the difficulties that may occur when trying to expand such cells.

Anti-leukemic activity of valproic acid and imatinib mesylate on human Ph+ ALL and CML cells in vitro

The armamentarium of anti-leukemic drugs has increased substantially since anti-leukemic activities were recently found for a variety of non-classical cytostatic drugs, among them the histone deacetylase (HDAC) inhibitor valproic acid (VPA). This study investigated the effect of VPA on proliferation and apoptosis of human Philadelphia chromosome-positive (Ph+) acute lymphatic (ALL) and chronic myeloid leukemia (CML) cells and on colony formation of human chronic-phase CML progenitor cells. Strong anti-proliferative and pro-apoptotic effects of VPA were observed on human ALL and CML cell lines at concentrations achievable in vivo. These effects were most pronounced in ALL cell lines as well as in primary ALL cells. Notably, VPA revealed enhanced activity with imatinib mesylate, nilotinib, the farnesyl transferase inhibitor SCH66336, interferon-alpha and cytosine arabinoside. VPA inhibited the growth of colony-forming cells from 12 Ph+ chronic-phase CML patients but also of those from normal healthy controls in a dose-dependent fashion. HDAC-inhibiting activity of VPA was confirmed on ALL and CML cells. In conclusion, VPA, whether alone or in combination with other non-classical anti-leukemic compounds, exerts significant anti-leukemic effects on human ALL and CML cells.

Mosaicism due to myeloid lineage–restricted loss of heterozygosity as cause of spontaneous Rh phenotype splitting

Spontaneous Rh phenotype alteration interferes with pretransfusion and prenatal blood group examinations and may potentially indicate hematologic disease. In this study, the molecular background of this biologic phenomenon was investigated. In 9 patients (3 with hematologic disease), routine RhD typing showed a mixture of D-positive and D-negative red cells not attributable to transfusion or hematopoietic stem-cell transplantation. In all patients, congenital and acquired chimerism was excluded by microsatellite analysis. In contrast to D-positive red cells, D-negative subpopulations were also negative for C or E in patients genotyped CcDdee or ccDdEe, respectively, which suggested the presence of erythrocyte precursors with an apparent homozygous cde/cde or hemizygous cde/— genotype. Except for one patient with additional Fyb antigen anomaly, no other blood group systems were affected. RH genotyping of single erythropoietic burst-forming units, combined with microsatellite analysis of blood, different tissues, sorted blood cell subsets, and erythropoietic burst-forming units, indicated myeloid lineage–restricted loss of heterozygosity (LOH) of variable chromosome 1 stretches encompassing the RHD/RHCE gene loci. Fluorescent in situ hybridization studies indicated that LOH was caused by either somatic recombination or deletion. Therefore, most cases of spontaneous Rh phenotype splitting appear to be due to hematopoietic mosaicism based on LOH on chromosome 1.

Overnight refrigerator storage of autologous peripheral progenitor stem cells without cryopreservation

We compared cryopreservation of peripheral blood progenitor cell (PBPC) products immediately and after overnight storage. There was no statistically significant difference in the groups regarding median CD(34)+ cell count of the product, storage duration at -80 degrees C, viability rates, neutrophil and platelet engraftment days. Overnight storage of products with leukocyte count >300x10(9)/l has longer leukocyte (P=0.03) and platelet (P=0.01) engraftment days compared to other groups. Overnight storage without adding any medium or plasma for the apheresis product with leukocyte count of less than 300x10(9)/l in a commercially available refrigerator can easily and safely be used in transplantation centers.

Fresh PBSC harvests, but not BM, show temperature-related loss of CD34 viability during storage and transport

BACKGROUND

The optimum conditions for storage and transport of freshly harvested HPC in the liquid state are uncertain. It is not specified in commonly applied standards for stem cell transplantation. We used a viable CD34 assay to determine the optimum temperature for maintaining progenitor cell viability in freshly harvested BM and PBSC. Our aim was to identify standardized conditions for storage and transport of marrow or peripheral blood products that would optimize CD34 recovery, leading to better transplant outcomes.

METHODS

Samples were aseptically removed from 46 fresh HPC harvests (34 PBSC and 12 BM) and stored at refrigerated temperature (2-8 degrees C), room temperature (18-24 degrees C) and 37 degrees C for up to 72 h. Samples were analyzed for viable CD34+ cells/microL at 0, 24, 48 and 72 h.

RESULTS

The mean viable CD34+ yield prior to storage was 7.7 x 10(6)/kg (range 0.7-30.3). The mean loss of viable CD34+ cells in HPC products at refrigerated temperature was 9.4%, 19.4% and 28% at 24, 48 and 72 h, respectively. In contrast, the mean loss of viable CD34+ cells at room temperature was 21.9%, 30.7% and 43.3% at 24, 48 and 72 h, respectively. No viable CD34+ cells remained after storage at 37 degrees C for 24 h. Only PBSC products and not BM showed temperature-related loss of CD34 viability. Greater loss of viable CD34+ cells was observed for allogeneic PBSC compared with autologous PBSC.

DISCUSSION

These results demonstrate that the optimum temperature for maintaining the viability of CD34+ cells, during overnight storage and transport of freshly harvested HPC, is 2-8 degrees C. These findings will allow the development of standard guidelines for HPC storage and transport.

Cobblestone Area-Forming Cells in Human Cord Blood Are Heterogeneous and Differ from Long-Term Culture-Initiating Cells

The long-term culture-initiating cell (LTC-IC) assay is a physiological approach to the quantitation of primitive human hematopoietic cells. The readout using identification of cobblestone area-forming cells (CAFC) has gained popularity over the LTC-IC readout where cells are subcultured in a colony-forming cell assay. However, comparing the two assays, cord blood (CB) mononuclear cell (MNC) samples were found to contain a higher frequency of CAFC than LTC-IC (126 +/- 83 versus 40 +/- 31 per 10(5) cells, p = 0.0001). Overall, 60% of week-5 cobblestones produced by CB MNC were not functional LTC-IC and were classified as "false." Separation of CB MNC using immunomagnetic columns showed that false cobblestones were CD34(-)/lineage(+). Purified CD34(+) cells, as expected, gave very similar readouts in the two assays, with 4,084 and 3,468/10(5) cells being CAFC and LTC-IC, respectively. CD34(-)/lineage(-) cells did not form cobblestones or become CD34(+) on stroma or in cytokine culture. Human CB MNC contain a population of mature lineage(+) cells, possibly mature T or B cells, which, although producing cobblestone areas (CA), are not functional LTC-IC. The CAFC readout by this method, therefore, is unreliable for estimation of primitive hematopoietic cells by limiting dilution analysis in whole human CB or MNC and also may not detect CD34(-) CA stem cells.

Expansion of mobilized peripheral blood progenitor cells under defined culture conditions rsing CD34+CD71-CD45- cells as a starting population

A major goal of experimental and clinical hematology is the identification of mechanisms and conditions supporting the expansion of transplantable hematopoietic stem cells. We assessed the expansion potential of CD34+CD71-CD45- cells derived from granulocyte colony-stimulating factor (G-CSF)-mobilized peripheral blood under recently defined serum-free culture conditions. The CD34+CD71-CD45- cells in mobilized peripheral blood were found to contain the majority (92%+/-5.6) of primitive long-term culture initiating cells (LTCIC) and 53.5%+/-16.7 of the more committed colony-forming cells (CFC). Furthermore, this population represents 23.3%+/-4.1 of the total CD34+ cells and allows reduction of the cell density important for maintenance/expansion of primitive progenitor cells. CD34+ CD71- CD45- cells were cultured in defined serum-free media supplemented with 300 ng each of Flt-3 ligand and stem cell factor (SCF), 60 ng of interleukin (IL)-3, and 20 ng each of IL-6 and G-CSF. Mononuclear cells (MNC) and CFC were expanded 50-fold and 200-fold, respectively; primitive progenitor cells (LTC-IC) were maintained at input values after a total of 10 days of expansion. The addition of IL-15 to our cytokine cocktail expanded LTC-IC 2- to 3-fold and CFC to >500-fold. The data presented should allow clinical manipulation (purging) and expansion procedures with mobilized PBPC harvests without the loss of primitive progenitor cells and could be made applicable for large-scale clinical expansion.

Breaking the rules? X-ray examination of hematopoietic stem cell grafts at international airports

Hematopoietic stem cell grafts from unrelated donors are commonly transported by aircraft. They must not be subjected to x-rays during security checks, which may cause inconvenient discussions between the courier and the airport security staff. We exposed hematopoietic stem cells from mobilized peripheral blood to a widely used x-ray hand-luggage control system. Cell viability as well as growth in vitro of mature progenitor cells (colony-forming cells), primitive progenitor cells (long-term culture-initiating cells), and lymphocytes were not altered even after 10 passages through the hand-luggage control system. Thus, repeated exposure to the low radiation dose of hand-luggage control systems (1.5 +/- 0.6 microSv per exposure) seems to be harmless for hematopoietic stem cells, which should simplify the international transport of stem cell grafts.

Low concentrations of STI571 in the cerebrospinal fluid: a case report

We report a 53-year-old man with lymphoid blast crisis of Ph+ chronic myeloid leukaemia who was treated with STI571, a selective inhibitor of the enzymatic activity of BCR-ABL. He responded excellently to STI571 (600 mg/d), obtaining a complete cytogenetic remission after 3 months of therapy. Although remission in the bone marrow was sustained, the patient developed an isolated central nervous system relapse. Subsequent analyses of STI571 concentrations in the cerebrospinal fluid (CSF) revealed 2-log lower CSF levels of STI571 than corresponding plasma levels. These are the first data demonstrating a low penetration of orally administered STI571 into the CSF in humans.

High-dose hydroxyurea plus G-CSF mobilize BCR-ABL-negative progenitor cells (CFC, LTC-IC) into the blood of newly diagnosed CML patients at any time of hematopoietic regeneration

The objective of this study was to analyze the mobilization kinetics of normal (BCR-ABL(neg)) and malignant (BCR-ABL(pos)) progenitor cells using a new, low toxic, out-patient-based mobilization regimen for Philadelphia chromosome-positive (Ph(pos)) chronic myelogenous leukemia (CML) patients. High doses of hydroxyurea (HD-HU, 3.5 g/m(2) per day, orally for 7 days) followed by granulocyte colony-stimulating factor (G-CSF) (10 microg/kg subcutaneously) were administered to 11 newly diagnosed CML patients. Each apheresis product (n = 30) was individually analyzed for the number and genotype of mature colony-forming cells (CFC) and primitive long-term culture initiating cells (LTC-IC), respectively, by reverse transcription polymerase chain reaction (RT-PCR) of individual colonies. Sufficient numbers of CD34(+) cells/kg bodyweight (BW) could easily be obtained in all patients (median, 15 x 10(6)/kg BW per patient) with a median number of three aphereses performed per patient (range 2-4). Almost each apheresis itself (25/30) contained > or =2 x 10(6) CD34(+) cells/kg BW. All patients with low and intermediate Sokal risk indices (9/11) mobilized primarily BCR-ABL(neg) LTC-IC (median 92%, range 47-100) and CFC (median 89%, range 57-100). Moreover, the mean percentage of BCR-ABL(neg) CFC and LTC-IC in the various apheresis products in these patients did not change throughout the entire time of hematopoietic regeneration. The toxicity of the mobilization procedure was low. Side effects were mild erythema in 8/11 and oral mucositis in 3/11 patients. Overall, the low toxicity of this regimen, together with the fact that sufficient BCR-ABL(neg) progenitors can be collected throughout the entire period of hematopoietic regeneration, renders this mobilization regimen particularly attractive for the collection of BCR-ABL(neg) progenitors in early chronic phase of Ph(pos) CML.

The phenotypic profile of CD34-positive peripheral blood stem cells in different mobilization regimens

The type of regimen used might result in mobilization of phenotypically and functionally different CD34(+) cells. We compared the phenotype of CD34(+) cells in leukapheresis products of three homogeneous groups: I, healthy individuals treated with granulocyte colony-stimulating factor (G-CSF) alone (n = 13); II, patients mobilized with G-CSF following chemotherapy (n = 16); and III, patients mobilized with G-CSF after high-dose chemotherapeutic pretreatment (n = 24). Multiparameter flow cytometry was performed for CD34(+) subpopulation analysis and focused on adhesion molecules, differentiation markers and megakaryocytic markers relevant for stem cell homing, with special reference to the importance of L-selectin expression. Regimens I and II led to higher numbers of mobilized CD34(+) cells (mean 468 x 10(6) and 491 x 10(6) CD34(+) cells per leukapheresis procedure respectively) than regimen III (mean 41 x 10(6) CD34(+) cells per leukapheresis procedure). Both the expression of L-selectin and CD54 on CD34(+) cells was significantly lower in group III, as was the percentage of megakaryocytic (CD41(+)) progenitors. A higher percentage of primitive (CD38(-) and/or HLA(-)DR(-)) CD34(+) cells was found in group III, correlating with a higher clonogenicity of the CD34(+) cells. However, when comparing the CD34(+)_ subpopulations that were also positive for L-selectin, there was no significant difference between the three regimens. A similar approach for the megakaryocytic CD34+ population resulted in an even worse quality of regimen III: 5.1% of CD34(+) being CD41(+)/L-selectin(+) compared with 9.2% and 8.9% in regimens I and II respectively. We concluded that the phenotypes of the CD34(+) cells in the G-CSF (group I) and G-CSF-chemotherapy (group II) regimens are similar, whereas the phenotype of the CD34(+) cells mobilized in the high-dose regimen (group III) displayed features that might negatively influence homing of the cells. Future studies will be directed towards regimens that will lead to the mobilization of a higher amount of CD34(+) cells with a phenotypically favourable phenotype.