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

No Detectable Alteration of Inorganic Allogeneic Bone Matrix Colonizing Mesenchymal Cells: A Step Towards Personalized Bone Grafts

Background

During major bone substance loss, secured allogeneic bone matrix (ABM) is normally utilized for bone repair. Here, we propose a method to colonize ABM using autologous mesenchymal cells (MCs) to improve their integration. Moreover, in this study, the consequences of in vitro colonization on MCs have been evaluated.

Methods

After in vitro propagation of MCs, their proliferation kinetics on ABM pre-coated with gelatin, fibronectin, collagen IV and human serum (HS) was monitored, and they were compared with cells cultured without ABM for 8 weeks. The effect of ABM on cell phenotype was also assessed. Lastly, the ability of ABM-colonizing MCs to perform hematopoiesis, a function normally preserved in selected culture conditions, and their differentiation towards osteoblastic lineage were evaluated.

Results

MC and colony-forming unit-fibroblast proliferated 930- and 590-fold, respectively. The proliferation rate of the expanded MCs was higher, forming a 3-dimensional structure in all ABMs. Pre-coating with HS was the most efficient treatment of ABMs to increase the initial adherence of MCs, and it partly explains the reason for the higher propagation of MCs. Flow cytometry analyses revealed subtle alterations in ABM-colonizing cells; however, the ability of MCs to maintain long-term culture initiating cells proliferation and differentiate into osteoblastic lineage was preserved.

Conclusions

In this study, the in vitro biocompatibility of bone marrow (BM) MCs with ABMs, the role of HS in scaffold coating, and the possibility of initially using a small BM sample for this approach were demonstrated.

Assessing hematopoietic (stem-) cell behavior during regenerative pressure

Hematopoiesis is a complex and strongly regulated process. In case of regenerative pressure, efficient recovery of blood cell counts is crucial for survival of an individual. We propose a quantitative mathematical model of white blood cell formation based on the following cell parameters: (1) proliferation rate, (2) self-renewal, and (3) cell death. Simulating this model we assess the change of these parameters under regenerative pressure. The proposed model allows to quantitatively describe the impact of these cell parameters on engraftment time after stem cell transplantation. Results indicate that enhanced self-renewal during the posttransplant period is crucial for efficient regeneration of blood cell counts while constant or reduced self-renewal leads to delayed recovery or graft failure. Increased cell death in the posttransplant period has a similar impact. In contrast, reduced proliferation or pre-homing cell death causes only mild delays in blood cell recovery which can be compensated sufficiently by increasing the dose of transplanted cells.

Efficacious but insidious: a retrospective analysis of fludarabine-induced myelotoxicity using long-term culture-initiating cells in 100 follicular lymphoma patients

OBJECTIVE

Fludarabine has been recognized as effective treatment in patients with follicular lymphoma (FL), but can induce myelotoxicity of unknown mechanism.

MATERIALS AND METHODS

Myelotoxicity was assessed by cultivation of two types of hematopoietic progenitor cells: colony-forming units granulocyte-macrophage (CFU-GM) and long-term culture-initiating cells (LTC-IC). Pretreatment amounts of CFU-GM and LTC-IC were correlated to age, gender, stage of disease, bone marrow involvement, and previous therapy. Posttreatment comparison of CFU-GM and LTC-IC was performed after different regimens of chemotherapy: fludarabine-based (FND +/- R), procarbazine-based (COPP +/- R), and CHOP(cyclophosphamide, doxorubicin, vincristine, prednisone) +/- R(Rituximab).

RESULTS

One-hundred patients (median age 55 years; 21 patients relapsed) treated for FL were analyzed. The total number of progenitor hematopoietic cells in both types of cultures varied in wide ranges; for LTC-IC between 0 and 874 cells/mL with a median of 77.71 cells/mL and for CFU-GM between 0 and 531 x 10(2) cells/mL with a median of 30.58 x 10(2) cells/mL. Bone marrow involvement, gender, stage of disease, or previous therapy had no influence on LTC-IC and CFU-GM counts. We identified an increase in LTC-IC, but not CFU-GM, associated with age (p = 0.01). Median figures for CFU-GM and LTC-IC were found to be significantly lower after FND +/- R and COPP +/- R than after CHOP +/- R therapy, compared to baseline values (p < 0.01).

CONCLUSIONS

Fludarabine and procarbazine have a dramatic influence, especially on the most immature hematopoietic cells, mirrored in reduced numbers of LTC-IC. This finding is consistent with clinical observations (poor mobilization after fludarabine) and offers an insight into the mechanism of fludarabine-induced myelotoxicity.

Effects of Delta1 and Jagged1 on early human hematopoiesis: correlation with expression of notch signaling-related genes in CD34+ cells

It has been shown that Notch signaling mediated by ligands of both Jagged and Delta families expands the hematopoietic stem cell compartment while blocking or delaying terminal myeloid differentiation. Here we show that Delta1- and Jagged1-expressing stromal cells have distinct effects on the clonogenic and differentiation capacities of human CD34(+) CD38(+) cells. Jagged1 increases the number of bipotent colony-forming unit-granulocyte macrophage (CFU-GM) and unipotent progenitors (CFU-granulocytes and CFU-macrophages), without quantitatively affecting terminal cell differentiation, whereas Delta1 reduces the number of CFU-GM and differentiated monocytic cells. Expression analysis of genes coding for Notch receptors, Notch targets, and Notch signaling modulators in supernatant CD34(+) cells arising upon contact with Jagged1 and Delta1 shows dynamic and differential gene expression profiles over time. At early time points, modest upregulation of Notch1, Notch3, and Hes1 was observed in Jagged1-CD34(+) cells, whereas those in contact with Delta1 strikingly upregulated Notch3 and Hes1. Later, myeloid progenitors with strong clonogenic potential emerging upon contact with Jagged1 upregulated Notch1 and Deltex and downregulated Notch signaling modulators, whereas T/NK progenitors originated by Delta1 strikingly upregulated Notch3 and Deltex and, to a lesser extent, Hes1, Lunatic Fringe, and Numb. Together, the data unravel previously unrecognized expression patterns of Notch signaling-related genes in CD34(+) CD38(+) cells as they develop in Jagged1- or Delta1-stromal cell environments, which appear to reflect sequential maturational stages of CD34(+) cells into distinct cell lineages.

Influence of telomere length on short-term recovery after allogeneic stem cell transplantation

OBJECTIVE

Telomeres shorten in somatic cells during aging and states of increased turnover, including hematopoietic stem cell transplantation. Fast hematopoietic recovery is critical for the patients' course after hematopoietic stem cell transplantation. It is unknown whether telomere length in hematopoietic stem cells (HSCs) predicts short-term hematopoietic recovery.

METHODS

We quantified telomere length by flow fluorescence in situ hybridization analysis in HSCs and granulocytes of healthy stem cell donors and monitored time to peripheral blood cell recovery in transplanted hosts. Furthermore, we measured in vitro repopulation potency of HSCs by assaying for colony-forming units granulocyte-macrophage (CFU-GM).

RESULTS

Telomere length in HSC shortens continuously in vivo and is comparable to telomere length in granulocytes from the same individual. Numbers of in vitro formed CFU-GM per HSC show an inverse relationship to age and telomere length. However, telomere length in HSCs was not correlated with short-term recovery after HSC transplantation.

CONCLUSION

These findings suggest that healthy stem cell donors have sufficient telomere length reserve to repopulate a myeloablatively treated host, despite continuous aging of HSCs in vivo and decreased repopulation ability of HSCs from older donors in vitro.

CD34+CDw90(Thy-1)+ subset colocated with mesenchymal progenitors in human normal bone marrow hematon units is enriched in colony-forming unit megakaryocytes and long-term culture-initiating cells

OBJECTIVE

The progress made in the supportive care of allografts and the identification of mesenchymal stem cells in adult human bone marrow (BM) has prompted renewed interest in the use of BM as a form of cell therapy. With the aim of optimizing the collection of BM cells, we evaluated the hematopoietic and mesenchymal immature cell contents of BM hematon units (HUs), which usually are eliminated during graft processing.

MATERIALS AND METHODS

Hematopoietic CD34+ progenitors from HU and buffy coat (BC) compartments were characterized in short-term culture. The sorted CD34+CDw90(Thy-1)+ primitive subset was assessed in colony-forming cell (CFC) and long-term culture-initiating cell (LTC-IC) assays, then further characterized by the expression of additional antigens. In parallel, we evaluated the colony-forming unit fibroblast (CFU-F) number and phenotyped the fresh adherent (D1-3) cells.

RESULTS

The plating efficiencies of CD34+ cells derived from HU and BC were identical. However, the HU CD34+CDw90(Thy-1)+ subset was enriched in colony-forming unit megakaryocyte (2.3x), LTC-IC (4.6x), and cells coexpressing CD105 (5x). We found a higher frequency of CFU-F (4.7x), considered to be the mesenchymal stem cell-containing population, correlated with an enrichment in fresh adherent (CD45/GPA)-CD14- cells.

CONCLUSIONS

We show for the first time that functional properties of the CD34+CDw90+ subset are related to its in vivo location in HU, which may represent the BM mesenchymal reserve compartment. The location in HU of 35.6%, 59.1%, and 58.7% of CD34+ cells, CD34+CDw90+ LTC-IC, and CFU-F, respectively, justifies the development of a procedure to collect them in order to reduce the therapeutic BM volume.

Granulocyte colony-stimulating factor mobilized whole blood containing over 0.3 x 106/kg CD34+ cells is a sufficient graft in autologous transplantation for relapsed non-Hodgkin's lymphoma

The feasibility of unprocessed, granulocyte colony-stimulating factor (G-CSF)-mobilized whole blood (WB) as an alternative stem cell source for autologous stem cell transplantation was studied. Forty-seven relapsed non-Hodgkin's lymphoma (NHL) patients entered the study. After two or three ifosfamide, methotrexate and etoposide (IMVP) courses, 1 l of G-CSF-mobilized WB was collected and stored refrigerated for 72 h. Meanwhile, BAM conditioning was given: BCNU (carmustine) 300 mg/m(2), high-dose cytarabine 6000 mg/m(2) and melphalan 140 mg/m(2). Toxicity, haematological recovery and survival were assessed and compared with peripheral blood stem cell transplantation (PBSCT) and bone marrow transplantation (BMT) reference groups. High-dose G-CSF (2 x 12 microg/kg/d) gave the best mobilization results. Haematological recovery was related to the WB CD34+ content. A CD34+ threshold of >or= 0.3 10(6)/kg, obtained in 90% of patients using high-dose G-CSF, correlated with adequate recovery: absolute neutrophil count (ANC) > 0.5 x 10(9)/l: median 12 d (range 9-19). Platelet recovery > 20 and > 50 x 10(9)/l was 19 (11-59) and 30 d (14 not reached) respectively. Overall survival of patients < 60 years was 57% at 4 years and event-free survival was 32%. Survival was comparable with PBSCT and BMT after BEAM (BCNU, etoposide, cytarabine, melphalan). Remarkably, haematological recovery after BAM + WB was rapid and comparable (ANC) or slightly prolonged (platelets) in comparison with BEAM + PBSCT, despite a 10-20 times lower CD34+ cell dose in the WB graft. In conclusion, transplantation of WB containing >or= 0.3 x 10(6)/kg CD34+ cells after BAM conditioning is a safe procedure, and offers a fully equivalent and less costly alternative for PBSC.