CD34-positive Progenitor Research Articles

An update on peripheral blood progenitor cell transplantation

High-dose therapy with stem cell rescue is increasingly being used as a salvage or consolidation therapy for patients with poor-risk malignant disease. The availability of peripheral blood progenitor cells (PBPC) has opened new therapeutic perspectives to alleviate the severe toxicity related to prolonged myelo-suppression. The preferred method of collection is still a matter of much debate. PBPC can be collected in steady state and after chemotherapeutic conditioning, growth factor priming, or both. Usually a heterogeneous population containing both committed progenitors and pluripotent stem cells can be harvested. Studies comparing engraftment after mobilized PBPC with recovery after autologous bone marrow transplantation confirm the beneficial effect on neutrophil and platelet engraftment. The accelerated hematological recovery can be associated with a number of clinical benefits including a reduction of platelet transfusions and shorter hospital stay. Only a few randomized studies are currently available on the long-term outcome after PBPC transplantation. Recent findings on tumor cell mobilization stimulated the development of techniques for tumor cell reduction, based on negative selection ("purging") of tumor cells or positive selection of CD34-positive progenitor cells. Positive CD34 selection is also imperative for successful ex vivo expansion of progenitor cells and gene transfer experiments. The value of PBPC in the field of allogeneic transplantation is currently being examined.

Bone marrow pathology in relapsing polychondritis: high frequency of myelodysplastic syndromes.

Haemopathologic changes were studied in 19 patients (13 male, six female, age 33-85 years, mean 56 years) with relapsing polychondritis (RP). Anaemia was found in eight, thrombocytopenia in two and splenomegaly in three patients. A total of 17 bone marrow biopsies were obtained from seven individuals. Bone marrow evaluation revealed myelodysplastic syndromes (MDS) with marked trilineage hyperplasia and dysplasia in three cases. Since an excess of myeloblasts or an increase of CD34 positive progenitor cells was not seen, the disorders were designated as 'refractory anaemia' or with regard to the dysplastic megakaryopoiesis 'MDS, unclassifiable'. Two of the three patients died after 10 and 55 months of follow-up due to infectious complications. In a further patient, bone marrow analysis repeatedly showed an unexplained granulopoietic hyperplasia, which, however, was not dysplastic enough to allow a diagnosis of MDS. The remaining patients had clearly reactive changes. Our findings support the notion that RP is a heterogenous disorder and suggest that RP may at times represent a paraneoplastic phenomenon of an underlying MDS. Since HLA typing revealed a significantly increased frequency of the antigen DR4 (10/17 patients positive = 59%), we hypothesize that immunological imbalances due to the MDS in conjunction with a specific immunogenetic background may play key roles in the pathogenesis of RP in these patients.

Subpopulations of CD34-positive haemopoietic progenitors in fetal blood.

Flow cytometry was used to determine the percentage and number of circulating CD34+ cells in fetal blood from 100 pregnancies at 13-38 weeks gestation. When expressed as a percentage of the total number of lymphocytes, the proportion of CD34+ cells decreased exponentially from a mean of 11.1% (9.2 x 10(7)/l) at 13 weeks to 1.0% (3.0 x 10(7)/l) at 38 weeks (r = 0.751, P < 0.0001). The use of primitive fetal blood CD34+ progenitor cells for prenatal somatic gene therapy may have distinct advantages over postnatal somatic gene therapy.

Transplantation of enriched CD34-positive autologous marrow into breast cancer patients following high-dose chemotherapy: influence of CD34-positive peripheral-blood progenitors and growth factors on engraftment.

To evaluate the capacity of enriched CD34-positive (CD34+) progenitor cells to reconstitute hematopoiesis in poor-prognosis breast cancer patients following administration of a high-dose alkylating agent chemotherapy regimen. Forty-four breast cancer patients received high-dose chemotherapy followed by autologous bone marrow support (ABMS) with CD34+ hematopoietic progenitor cells in five sequentially treated cohorts. Following infusion of CD34+ marrow, cohort no. 1 received no growth factor, cohort no. 2 received granulocyte colony-stimulating factor (G-CSF), and cohort no. 3 received granulocyte-macrophage colony-stimulating factor (GM-CSF). Cohort no. 4 received the CD34+ fractions of both marrow and peripheral-blood progenitor cells (PBPCs) plus G-CSF. Cohort no. 5 received only the CD34+ PBPCs plus G-CSF. Immunohistochemical staining for breast cancer was performed on all hematopoietic cell products before and after the positive selection procedure, to assess quantitatively the level of tumor-cell contamination. Cohorts no. 1, 2, 3, 4, and 5 achieved a granulocyte count > or = 500 x 10(9)/L in a median of 23, 10, 16, 11, and 11 days, with a platelet count greater than 20,000 x 10(9)/L documented in a median of 22, 23, 32, 12, and 10 days, respectively. The time to granulocyte reconstitution was significantly shorter for patients who received CD34+ PBPCs alone (cohort no. 5), or in combination with CD34+ marrow (cohort no. 4), when compared with those who received only the CD34+ marrow fraction (P < .01). From 1 to greater than 4 logs of breast cancer cell depletion were documented after CD34-selection, for patients in whom tumor was initially detected. CD34+ marrow and/or PBPCs provide reliable and timely hematopoietic reconstitution in breast cancer patients receiving high-dose chemotherapy. Contamination of both marrow and PBPCs with breast cancer cells was reduced using this positive selection technique.

Affection of CD 34-positive progenitor cells by chromosome abnormalities and karyotype evolution in a case of secondary MDS

Affection of CD 34-positive progenitor cells by chromosome abnormalities and karyotype evolution in a case of secondary MDS

The effect of recombinant stem cell factor (SCF) on purified CD34-positive human umbilical cord blood progenitor cells.

We describe the effect of soluble c-kit ligand (stem cell factor, SCF) on highly purified CD34-positive hemopoietic progenitors from human umbilical cord blood. Progenitor cells were purified from cord blood mononuclear cells by immune rosetting with lineage specific antibodies and subsequent sorting of the rosette-negative population for CD34(BI3C5)-positive cells. This procedure enriched greater than 100-fold for colony forming cells (CFC). Using optimal concentrations of colony-stimulating factors (CSF) without added SCF approximately 2.5% of cells formed colonies. SCF also had CSF activity on this population, up to 0.5% of cells forming small colonies in response to SCF alone. In contrast, the addition of SCF to optimal concentrations of the other growth factors produced a greater than 10-fold increase in colony number. However, the most notable effect was an approximately 100-fold increase in the number of cells in each colony. Equally striking was the very high proportion (50-80%) of mixed colonies (CFU-MIX). These findings suggest the progenitor cell pool in cord blood is skewed towards very early cells. However, when day 14 colonies formed in response to SCF and other factors were assessed for their re-cloning potential they did not contain significant numbers of CFC, implying that SCF did not support the self-renewal of these CD34 positive cord blood progenitor cells. These findings support a role for SCF as an enhancing factor for hemopoietic progenitor cells but it does not promote self-renewal in these populations.

Proliferative Responses to Interleukin-3 and Granulocyte Colony-Stimulating Factor Distinguish a Minor Subpopulation of CD34-Positive Marrow Progenitors That Do Not Express CD33 and a Novel Antigen, 7B9

Human hematopoietic colony-forming cells (CFC) express the CD34 antigen (CD34+) as well as differentiation antigens such as CD33 and HLA-DR. CD34+ cells that do not express these latter differentiation antigens have been shown to contain few CFC in direct culture, but generate increasing numbers of CFC when cultured over a marrow stromal cell layer in the long-term culture system. In this study we determined if CD34+ cells with low or absent expression of CD33 and a novel antigen, 7B9 (CD34+CD33-7B9-), could be distinguished from CD34+ cells expressing these antigens (CD34+CD33+7B9+) based on their proliferative responses to interleukin-3 (IL-3) and granulocyte colony-stimulating factor (G-CSF) in a short-term liquid culture system. These two populations were separated by fluorescence-activated cell sorting, cultured with IL-3 (10 ng/mL), G-CSF (100 ng/mL), or IL-3 and G-CSF, and 3H-thymidine uptake was measured. CD34+CD33-7B9- cells proliferated in the presence of IL-3, but not G-CSF. However, a synergistic response to the combination of IL-3 and G-CSF was seen in most experiments. In contrast, CD34+CD33+7B9+ cells proliferated in the presence of either IL-3 or G-CSF but did not display an additive or synergistic response to the combination of IL-3 and G-CSF. In colony-forming assays performed before and after liquid culture, the CD34+CD33-7B9- cells in two experiments contained 0.3% and 2.2% of all sorted marrow CFC before liquid culture and generated 40-fold and ninefold increases in the number of granulocyte-macrophage colony-forming units (CFU-GM), respectively, after liquid culture with IL-3 and G-CSF. In contrast, the CD34+CD33+7B9+ cells contained 99.7% and 97.8% of all sorted marrow CFC before liquid culture and had no change or a threefold increase in the number of CFU-GM, respectively, after liquid culture with IL-3 and G-CSF. Single-cell liquid cultures containing IL-3 and G-CSF with cells that were either CD34+CD33-7B9- and depleted of mature lymphoid cells (CD34+lin-) or were CD34+lin+ showed that a higher proportion of wells containing a CD34+lin- cell gave rise to one or more CFC (8.7%) than did wells containing a CD34+lin+ cell (2.9%), with the responding cells in the former population giving rise to an average of 2.9 +/- 0.6 CFC and in the latter population, 2.0 +/- 1.0 CFC.(ABSTRACT TRUNCATED AT 400 WORDS)

Proliferative responses to interleukin-3 and granulocyte colony- stimulating factor distinguish a minor subpopulation of CD34-positive marrow progenitors that do not express CD33 and a novel antigen, 7B9

Human hematopoietic colony-forming cells (CFC) express the CD34 antigen (CD34+) as well as differentiation antigens such as CD33 and HLA-DR. CD34+ cells that do not express these latter differentiation antigens have been shown to contain few CFC in direct culture, but generate increasing numbers of CFC when cultured over a marrow stromal cell layer in the long-term culture system. In this study we determined if CD34+ cells with low or absent expression of CD33 and a novel antigen, 7B9 (CD34+CD33–7B9-), could be distinguished from CD34+ cells expressing these antigens (CD34+CD33+7B9+) based on their proliferative responses to interleukin-3 (IL-3) and granulocyte colony-stimulating factor (G-CSF) in a short-term liquid culture system. These two populations were separated by fluorescence-activated cell sorting, cultured with IL-3 (10 ng/mL), G-CSF (100 ng/mL), or IL-3 and G-CSF, and 3H-thymidine uptake was measured. CD34+CD33–7B9- cells proliferated in the presence of IL-3, but not G-CSF. However, a synergistic response to the combination of IL-3 and G-CSF was seen in most experiments. In contrast, CD34+CD33+7B9+ cells proliferated in the presence of either IL-3 or G-CSF but did not display an additive or synergistic response to the combination of IL-3 and G-CSF. In colony-forming assays performed before and after liquid culture, the CD34+CD33–7B9- cells in two experiments contained 0.3% and 2.2% of all sorted marrow CFC before liquid culture and generated 40-fold and ninefold increases in the number of granulocyte-macrophage colony-forming units (CFU-GM), respectively, after liquid culture with IL-3 and G-CSF. In contrast, the CD34+CD33+7B9+ cells contained 99.7% and 97.8% of all sorted marrow CFC before liquid culture and had no change or a threefold increase in the number of CFU-GM, respectively, after liquid culture with IL-3 and G-CSF. Single-cell liquid cultures containing IL-3 and G-CSF with cells that were either CD34+CD33–7B9- and depleted of mature lymphoid cells (CD34+lin-) or were CD34+lin+ showed that a higher proportion of wells containing a CD34+lin- cell gave rise to one or more CFC (8.7%) than did wells containing a CD34+lin+ cell (2.9%), with the responding cells in the former population giving rise to an average of 2.9 +/- 0.6 CFC and in the latter population, 2.0 +/- 1.0 CFC.(ABSTRACT TRUNCATED AT 400 WORDS)

Analysis of CD34-positive hemopoietic progenitor cells from normal human adult peripheral blood: flow-cytometrical studies and in-vitro colony (CFU-GM, BFU-E) assays

Hemopoietic progenitor cells are present in minute numbers in the peripheral blood of healthy adults. By in vitro colony-assays evaluating BFU-E- and CFU-GM-growth, their numbers have been estimated to be about 1,000 per 1.0 ml of whole blood. Employing a CD34-moAb, detecting an antigen present on virtually all hemopoietic progenitor cells, and by using multiparameter flow-cytometry, we have designed a flow-cytometric method for the quantitation of CD34(+)-cells in blood. Comparative studies on bone marrow and blood have shown that CD34(+)-cells from both sources display almost identical light-scatter characteristics. They differ, however, with regard to the coexpression of the CD33- and the CD19-antigens. In vitro colony-assays for BFU-E and CFU-GM in single cultures have shown that about 25% of the CD34(+)-cells from blood were clonogenic in vitro. Our data indicate that the CD34(+)-cells from peripheral blood differ substantially from bone marrow CD34(+)-cells.

Early Development of Mast Cells

Mast cells originate from pluripotential cells in the bone marrow. Specifically, human mast cells originate from CD 34-positive progenitor cells. Mast cell proliferation requires IL-3. In the mouse, additional mast cell growth is achieved by the addition of IL-4, and GM-CSF prevents mast cell proliferation. Early bone-marrow-derived mast cells can be identified by their IgE receptors, although they may not yet have the characteristic morphology of mature mast cells. Whether these early cells may by themselves have a physiologic role, remains to be determined. Mast cells persist in culture on fibroblast monolayers, in part due to the production of soluble factor(s) from the fibroblasts themselves. Final mast cell phenotype appears dependent upon the local tissue environment.