Culturing human umbilical cord blood: a comparison of mononuclear vs CD34+ selected cells

In vitro expansion of fetal liver hematopoietic stem cells

Fetal liver hematopoietic stem and progenitor cells (HSPCs) have been considered appropriate for the management of aplastic anemia owing to their proliferative potential. Bone marrow recovery was possible in some cases; the engraftment potential of these cells, however was unsatisfactory, possibly due to the availability of a smaller number of these cells from a single fetus. The present study explores how we can expand fetal liver hematopoietic stem cells under in vitro conditions. We isolated mononuclear cells from fetal liver and hematopoietic stem cells were identified and analyzed by cell surface marker CD34. CD34⁺ fetal liver HSPCs cells were separated by magnetic cell sorting positive selection method. HSPCs (CD34⁺) were cultured by using 5 cytokines, stem cell factor (SCF), granulocyte macrophages-colony stimulating factor (GM-CSF), interleukin-6 (IL-6), Fms-related tyrosine kinase 3 (FLT-3) and erythropoietin (EPO), in 4 different combinations along with supplements, in serum-free culture media for 21 days. Cell viability continued to be greater than 90% throughout 21 days of culture. The cells expanded best in a combination of media, supplements and 5 cytokines, namely SCF, FLT-3, IL6, EPO and GM-CSF to yield a large number of total (CD34⁺ & CD34^-) cells. Even though the total number of nucleated cells increased in culture significantly, levels of CD34 antigen expression declined steadily over this period.

Interleukin-6 enhances the activity of in vivo long-term reconstituting hematopoietic stem cells in "hypoxic-like" expansion cultures ex vivo

BACKGROUND

Since interleukin (IL)-6 synergizes with the physiologically relevant O2 concentration in the maintenance of primitive hematopoietic stem cell (HSC) subpopulations, we hypothesized that its addition to our hypoxic response mimicking cultures (HRMCs), composed of an antioxidant-supplied serum-free xeno-free medium supplemented with the cytokines stabilizing hypoxia-inducible factor-1α and balancing HSC self-renewal and commitment, will result in a similar effect even if they are exposed to 20% O2 .

STUDY DESIGN AND METHODS

HRMCs were exposed to 20 and 5% O2 with and without IL-6. Functional committed progenitors (colony-forming cells [CFCs]: CFU-GM, BFU-E, CFU-Mix, and CFU-Mk) were evaluated as well as the short- and long-term repopulating HSCs using in vivo NSG mice model (primary and secondary recipients, respectively).

RESULTS

The addition of IL-6 to HRMCs exposed to 20% O2 did not significantly impact either the CFCs or in vivo short-term repopulating cells. However, it enhanced both the frequency and the individual proliferative capacity of the most primitive long-term repopulating cell population evidenced by the generation of human CFCs in the marrow of secondary recipient mice. The exposure of HRMCs to 5% O2 negatively affected the amplification of CFCs, which was not changed by the addition of IL-6 and exhibited a partial enhancing effect on the long-term repopulating cells.

CONCLUSION

The addition of IL-6 to the cytokine cocktail further improves our expansion procedure based on atmospheric O2 concentration-exposed HRMCs by enhancing the maintenance of the most primitive HSCs without a negative impact on the less primitive HSC populations and CFCs.

Cytokinesis-block micronucleus assay adapted for analyzing genomic instability of human mesenchymal stem cells

Human mesenchymal stem cells (hMSCs) are multipotent cells used in cell therapy research. One of the problems involving hMSCs is the possibility of genetic instability during in vitro expansion required to obtain a suitable number of cells for clinical applications. The cytokinesis-block micronucleus (CBMN) assay measures genetic instability by analyzing the presence of micronucleus (MN), nucleoplasmic bridges (NPBs), and nuclear buds (NBUDs) in binucleated cells. The present study describes modifications in the CBMN assay methodology to analyze genetic instability in hMSCs isolated from the umbilical vein and in vitro expanded. The best protocol to achieve binucleated hMSCs with preserved cytoplasm was as follows: cytochalasin B concentration (4.0 μg/mL), use of hypotonic treatment (3 min), and the fixative solution (9 methanol:1 acetic acid). These adaptations were reproduced in three hMSC primary cell cultures and also in XP4PA and A549 cell lines. The frequency of hMSCs treated with mitomycin-C presenting MN was lower than that with other nuclear alterations, indicating that the hMSCs contain mechanisms to avoid a high level of chromosomal breaks. However, a high frequency of cells with NPBs was detected and spontaneous anaphase bridges under normal hMSC in vitro culture were observed. Considering that anaphase bridges are characteristic alterations in tumor cells, the CBMN assay is indicated as an important tool associated with other genetic analyses in order to ensure the safe clinical use of hMSCs in cell therapy.

Chromosomal characterization of cryopreserved mesenchymal stem cells from the human subendothelium umbilical cord vein

AIMS

To conduct a morphological, functional and chromosomal characterization of mesenchymal stem cell populations from the human subendothelium umbilical cord vein after cryopreservation.

MATERIAL & METHODS

Five human umbilical cords were processed in order to obtain mesenchymal stem cells. Flow cytometry, differentiation assays and cytogenetic analysis were carried out before and after the cryopreservation process.

RESULTS

Flow cytometry revealed that CD105, CD73 and CD90 markers were expressed by the cells, which lacked the expression of hematopoietic lineage markers, such as CD14, CD34 and CD45. The mesenchymal stem cells demonstrated capacity for osteogenic, adipogenic and chondrogenic differentiation. Chromosome analysis showed no clonal chromosome changes in the cells in either situation. However, a significant number of nonclonal chromosomal aberrations were apparent after cryopreservation, including monosomies and structural changes. Cells isolated from one umbilical cord exhibited a rare balanced paracentric inversion, likely a cytogenetic constitutional alteration. This was present both before and after experimental procedures.

CONCLUSION

These findings show that using mesenchymal stem cells for clinical approaches requires careful investigation and sensitive tests in order to ensure cellular therapy biosafety.

Ex vivo expansion of stem cells: defining optimum conditions using various cytokines

With the increasing information on the number, quality, and characteristics of hematopoietic stem cells (HSC) in umbilical cord and placental blood, this material has been found to be efficacious as an alternative source of HSC for transplantation in children. In this study, we sought to define the optimal conditions for ex vivo expansion of cord blood (CB) stem cells. These conditions include: the combinations and concentrations of hematopoietic growth factors (stem cell factor [SCF], granulocyte-macrophage colony-stimulating factor [GM-CSF], interleukin [IL]-3, thrombopoietin [Tpo], IL-6 and Fms-like tyrosine kinase 3 ligand [Flt-3L]), the duration of culture, and the effect of serum supplementation. In this study, 2 protocols were applied for ex vivo expansion of CB stem cells. In protocol I, 20 CB samples were expanded in a static, serum-added, liquid culture for 7 and 11 days using 5 cytokine cocktails. In protocol II, 10 CB samples were expanded for 7 days using cytokines of cocktail 1, with and without IL-6 and Flt-3L, in serum-added and serum-free culture media. This protocol was intended to verify the effect of IL-6, Flt-3L, and the role of serum supplementation in short-term liquid culture. From the present study, it can be concluded that cocktail 1 is the cocktail of choice for ex vivo expansion of CB stem cells in serum-free, liquid culture expanded for 7 days. We can also conclude that culture expanded for 7 days is better than 11 days, as the fold expansion of CD34+ cells was not significantly increased or even decreased in some of the cocktails used. Moreover, the percent of CD95+ cells (apoptotic cells) was significantly increased on day 11 compared to day 7 in the cocktails tested.

Stem cells expressing homing receptors could be expanded from cryopreserved and unselected cord blood

We assessed the cytokine combinations that are best for ex vivo expansion of cord blood (CB) and the increment for cell numbers of nucleated cells, as well as stem cells expressing homing receptors, by an ex vivo expansion of cryopreserved and unselected CB. Frozen leukocyte concentrates (LC) from CB were thawed and cultured at a concentration of 1 x 10(5)/mL in media supplemented with a combination of SCF (20 ng/mL)+TPO (50 ng/mL)+FL (50 ng/mL)+/-IL-6 (20 ng/mL)+/-G-CSF (20 ng/mL). After culturing for 14 days, the expansion folds of cell numbers were as follows: TNC 22.3+/-7.8 approximately 26.3+/-4.9, CFU-GM 4.7+/-5.1 approximately 11.7+/-2.6, CD34+CD38- cell 214.0+/-251.9 approximately 464.1+/-566.1, CD34+CXCR4+ cell 4384.5+/-1664.7 approximately 7087.2+/-4669.3, CD34+VLA4+ cell 1444.3+/-1264.0 approximately 2074.9+/-1537.0, CD34+VLA5+ cell 86.2+/-50.9 approximately 113.2+/-57.1. These results revealed that the number of stem cells expressing homing receptors could be increased by an ex vivo expansion of cryopreserved and unselected CB using 3 cytokines (SCF, TPO, FL) only. Further in vivo studies regarding the engraftment after expansion of the nucleated cells, as well as the stem cells expressing homing receptors will be required.

The impact of progenitor enrichment, serum, and cytokines on the ex vivo expansion of mobilized peripheral blood stem cells: a controlled trial

The aim of this study was to verify, and possibly improve, culture conditions to expand human mobilized peripheral blood stem cells (PBSCs). We investigated the role of three parameters: A) the culture medium (serum-free versus serum-dependent); B) the initial cell population (Ficoll-separated mononucleated cells versus CD34(+)-selected cells), and C) the low concentration of recombinant cytokines, flt3 ligand, and thrombopoietin in association with a basic cocktail of stem cell factor, interleukin (IL)-6, IL-3, GM-CSF, and erythropoietin. Eighteen leukapheresis samples were monitored in static culture for 15 days. The expansion potential was assessed at day 10 and 15 by total nuclear cells, colony-forming-units (CFUs) (burst-forming units-erythroid [BFU-E], colony-forming units-granulocyte-macrophage [CFU-GM], and colony-forming units-granulocyte-erythroid-macrophage-megakaryocyte [CFU-GEMM]), and flow cytometry immunophenotyping (CD34(+)/CD38(-), CD38(+), CD33(+), CD41(+), GlyA(+) progenitor cells). The results, evaluated by multivariate analysis of variance, emphasize that some variables affected the outcome of stem and progenitor cell expansion. CD34(+) enrichment increased expansion of total nuclear cells, number of CD38(+) and CD33(+) late precursors, and number of the CFU-GM compartment. Interestingly, however, quantitative expansion of GlyA(+) and the early progenitor cells (CD34(+)/CD38(-), CFU-GEMM, BFU-E) are favored by the use of unselected mononucleated cells. Regarding the role of serum, no significant difference was observed except for expansion of total nuclear cells, CFU-GM, and BFU-E. Cytokine combinations, in particular the use of flt3 ligand, stimulated expansion of almost all the cellular subsets, reaching a statistical significance for total nuclear cells and CFU-GM. Our study indicates that progenitor and late precursor multilineage cell compartments of mobilized PBSCs may be significantly expanded in short-term cultures by well-defined experimental conditions. Furthermore, these data might be useful when evaluating ex vivo expansion of hematopoietic cells for clinical purposes.

Expansion of megakaryocyte progenitors from cryopreserved leukocyte concentrates of human placental and umbilical cord blood in short-term liquid culture

Long-term severe thrombocytopenia following human placental and umbilical cord blood (CB) transplantation is a significant clinical problem. We studied the ex vivo expansion of megakaryocytic progenitor cells (CFU-Meg) from cryopreserved/thawed leukocyte concentrates (LC) of CB prepared by the Tokyo Cord Blood Bank protocol. The LC cells were cultured in serum-free culture medium supplemented with a combination of early-acting cytokines including thrombopoietin (TPO), flt3-ligand (FL), and stem cell factor (SCF). Combination of TPO plus FL, TPO plus SCF, and all of these cytokines together resulted in 8.9-, 7.7-, and 8.4-fold increases in CFU-Meg, respectively, by Day 5 of culture. Our results showed that this simple expansion strategy has the potential for expanding CFU-Meg from cryopreserved/thawed LC cells from CB.

Prenatal diagnosis of genetic abnormalities using fetal CD34+ stem cells in maternal circulation and evidence they do not affect diagnosis in later pregnancies

In the present study, we report a new method for enrichment and analysis of fetal CD34+ stem cells after culture in order to determine whether it is feasible for noninvasive prenatal diagnosis. We also determined whether fetal CD34+ stem cells persist in maternal blood after delivery and assessed whether they have an impact on noninvasive prenatal diagnosis of genetic abnormalities. Peripheral blood samples were obtained from 35 pregnant women, 13 non-pregnant women who had given birth to male offsprings, 12 women who had never been pregnant, and eight pregnant women with male fetuses. CD34+ stem cells were enriched and either cultured for prenatal diagnosis or analyzed with fluorescence in situ hybridization (FISH)/polymerase chain reaction (PCR) to determine peristance in maternal blood. Fetal/maternal cells can be isolated and grown "in vitro" to provide enough cells for a more accurate fetal sex or aneuploid prediction than is provided by unenriched and uncultured CD34+ stem cells. The presence of fetal cells in maternal blood samples from mothers who had given birth to male offspring was found in 3 of 13 blood samples. PCR was positive for Y chromosome in one woman who had never been pregnant. Analysis of cultured CD34+ stem cells from mothers with Y PCR positivity did not detect any male cells in any samples. Even if PCR positivity is due to persistence of fetal stem cells from previous pregnancies, it does not seem to affect this new system of enrichment, culture, and FISH analysis of CD34+ fetal stem cells.

IL-10 increases the number of CFU-GM generated by ex vivo expansion of unmanipulated human MNCs and selected CD34+ cells

BACKGROUND

Ex vivo expansion strategies with different cytokine combinations are currently used by several groups as a means of increasing the number of HPCs for a variety of special clinical applications. Because there is little information on the potential role of IL-10 in such ex vivo expansion models, the effect of this cytokine on the generation of myeloid progenitor cells in suspension cultures was investigated.

STUDY DESIGN AND METHODS

On the basis of data from the literature and from new experiments, the combination of SCF and IL-3 at concentrations of 100 ng per mL and 100 U per mL, respectively, was chosen as the standard cocktail. The addition of IL-10 to such cultures resulted in a marked and dose-dependent potentiation of myeloid progenitor cell production.

RESULTS

Using unmanipulated leukapheresis components from 13 individuals (including lymphoma and cancer patients and normal donors), the expansion multiple of CFU-GM after 14 days as compared with pre-expansion values was 9.54 +/- 2.31 times by SCF/IL-3 and 46.38 +/- 7.37 times by the combination of SCF/IL-3 and 100 ng per mL of IL-10 (p<0.001). IL-10 also potentiated CFU-GM generation from selected CD34 PBMNCs (n = 9) with an expansion of 17.22 +/- 7.04 times versus 45.67 +/- 16.78 times using the SCF/IL-3 and SCF/IL-3/IL-10 combination, respectively (p<0.05). Moreover, expansion-promoting effects of IL-10 were observed in liquid cultures containing MNCs from bone marrow (n = 4) and cord blood (n = 3), but did not reach statistical significance because of the small number of samples.

CONCLUSION

These results suggest IL-10 as a useful cytokine to optimize progenitor cell-expansion strategies for clinical application.

Chromosome analysis after ex vivo expansion of CD34+ cells from human cord blood

Ex vivo expansion of cord blood hematopoietic progenitors is an attractive way to prepare a sufficient number of transplantable cells for cord blood transplantation in adult patients. The expanded cells need to have genetic stability. Karyotypic analysis of the expanded cells from cord blood CD34(+) cells by 7-day culture with stem cell growth factor, interleukin (IL)-3, IL-6, granulocyte colony-stimulating factor, and erythropoietin was performed. Several-fold increases in total cell number and CFU-GM were 186.7 +/- 62.1 and 27.1 +/- 9.4 (mean +/- standard deviation of data from 6 samples), respectively. Karyotypes were analyzed in 600 expanded cells in total, and all of them showed normal karyotypes. This observation suggests that multifactor supported expansion of cord blood cells may not induce karyotypic abnormality, although a limited number of ex vivo expanded cells were tested.

Granulocyte colony-stimulating factor-mobilized peripheral blood CD34+ cells from children contain the same levels of long-term culture-initiating cells producing the same numbers of colony-forming cells as those from adults, but display greater in vitro monocyte/macrophage potential

Autologous peripheral blood progenitor cell (PBPC) transplantation is now commonly used in children. The ontogenic differences in haematopoiesis published in recent years suggest differences in the categories of mobilized PBPCs between children and adults. We investigated the frequency and distribution of mature progenitor cells (colony-forming cells, CFCs) and primitive progenitor cells [CD34+ CD38- and CD34+ Thy-1+ cells, long-term culture-initiating cells (LTC-ICs)] in children and adults mobilized using granulocyte colony-stimulating factor alone. We found similar proportions of granulocyte colony-forming units (CFU-G) and/or macrophage CFUs (CFU-M), mixed lineage CFUs (CFU-Mix) and megakarocyte CFUs (CFU-Mk), CD34+ CD38- and CD34+ Thy-1+ cells, and LTC-ICs (16.5 +/- 3.5 vs. 10.65 +/- 5 per 104 CD34+ cells), which produced the same number of CFCs (5 +/- 1 vs. 6 +/- 1 CFCs/LTC-ICs) in PB CD34+ cells from children and adults. However, we noted a higher proportion of erythroid blast-forming units (BFU-E) in PB CD34+ cells from adults (x 1.5, P = 0.003). Using cord blood as a third ageing point, we observed an inverse age-related propensity for commitment to the monocyte/macrophage lineage that was still found after normalizing the data per body weight and processed blood mass. This ontogeny-related programming was detected from the LTC-IC level, which produced 1.7 times more CFU-M in children than in adults (P = 0.048). These subtle differences in commitment between children and adults, shown here for the first time, are of interest for the in vitro manipulation of PBPCs and, in particular, for application in adoptive immunotherapy in children.

Serum supplement, inoculum cell density, and accessory cell effects are dependent on the cytokine combination selected to expand human HPCs ex vivo

BACKGROUND

The prolonged periods of pancytopenia associated with cord blood transplants suggest that in some cases cell numbers may be limiting. The possibility that limiting cell numbers may be overcome and prolonged periods of pancytopenia abrogated by the transplantation of human umbilical cord blood cells expanded ex vivo has led to efforts to define optimal culture conditions for these cells.

STUDY DESIGN AND METHODS

Cord blood CD34+ cells were cultured with three cytokine combinations: SCF+G-CSF+GM-CSF+MGDF (SGGM); IL-6+ SCF+MGDF+Flt3-ligand (6SMF); and IL-1+IL-3+IL-6+G-CSF+GM-CSF+SCF+Epo (GFmix). Serum effects, inoculum concentration (cells/mL) seeding density (cell/cm(2)) and accessory cell effects on the expansion of CD34+ cells were determined.

RESULTS

Cellular outputs were significantly higher with fetal calf serum (FCS) than with cord blood serum (CBS) or adult group AB serum (ABS) in the presence of 6SMF, however, CBS was as effective as FCS. The best seeding concentrations varied for each of the cytokine combinations, and inoculum densities exceeding 1000 cells per cm(2) proved detrimental for cultures containing GFmix and SGGM. Accessory cell studies indicated that populations expressing the CD33 antigen inhibited the expansion of purified CD34+ cells in the presence of GFmix or SGGM, but not in the presence of 6SMF.

CONCLUSION

Serum supplement, inoculum cell concentration, seeding densities, and accessory cell effects are dependent upon the cytokine combination selected to expand cord blood HPCs ex vivo. Thus, each of these measures should be assessed to establish reproducible and reliable conditions for the selection of different cytokine combinations to culture cord blood HPCs.

Expansion and transduction of nonenriched human cord blood cells using HS-5 conditioned medium and FLT3-L

Cord blood (CB) stem cell transplantations have been associated with delayed hematopoietic engraftment. This has most likely been due to the limited numbers of hematopoietic short-term repopulating cells in CB. Ex vivo expansion of CB has been attempted, and expansion of CD34-enriched CB has been successful; however, CD34 enrichment procedures are in general associated with substantial cell loss. Thus, we have studied culture conditions for expansion of nonenriched CB. Nonenriched CB cells were cultured for 21 days in the presence of conditioned medium from the HS-5 stromal cell line and FLT3-L or alternatively in the presence of FLT3-L, stem cell factor (SCF), megakaryocite growth and development factor (MGDF), and granulocyte colony-stimulating factor (G-CSF) (FSMG), either on fibronectin fragment CH-296-coated dishes or on uncoated dishes. With all four culture conditions, the number of mononuclear cells initially decreased until day 7 and then increased until the end of the expansion cultures. Overall expansion using HS-5 and FLT3-L resulted in superior expansion of MNC and CFU-C (44-/34-fold) for both cultures with and without CH-296 compared to FSMG (18-/17-fold). Expansion on CH-296 was less efficient than expansion on tissue culture-treated wells without CH-296 for both conditions. We then studied the best time for transduction on nonenriched CB. In contrast to enriched CD34 cells, we found for both conditions, HS-5/FLT3-L and growth factor cocktail, higher transduction efficiencies when cells were transduced on day 7 as compared to day 2. Gene transfer rates up to 45% were achieved with both conditions, which corresponded with the increased number of cells in S phase on day 7 compared to day 2. We conclude that HS-5 and FLT-3L allow efficient expansion and transduction of nonenriched CB.