Expansion Of Human Hematopoietic Progenitors Research Articles

Enhanced Ex Vivo Expansion of Human Hematopoietic Progenitors on Native and Spin Coated Acellular Matrices Prepared from Bone Marrow Stromal Cells.

The extracellular microenvironment in bone marrow (BM) is known to regulate the growth and differentiation of hematopoietic stem and progenitor cells (HSPC). We have developed cell-free matrices from a BM stromal cell line (HS-5), which can be used as substrates either in native form or as tissue engineered coatings, for the enhanced ex vivo expansion of umbilical cord blood (UCB) derived HSPC. The physicochemical properties (surface roughness, thickness, and uniformity) of native and spin coated acellular matrices (ACM) were studied using scanning and atomic force microscopy (SEM and AFM). Lineage-specific expansion of HSPC, grown on these substrates, was evaluated by immunophenotypic (flow cytometry) and functional (colony forming) assays. Our results show that the most efficient expansion of lineage-specific HSPC occurred on spin coated ACM. Our method provides an improved protocol for ex vivo HSPC expansion and it offers a system to study the in vivo roles of specific molecules in the hematopoietic niche that influence HSPC expansion.

Ex vivo expansion of human hematopoietic progenitors and cells to support high-dose chemoradiation therapy: five years of clinical experience.

The identification of cytokines-soluble or membrane-bound regulators of hematopoietic stem and progenitor cell survival, proliferation, and differentiation - and the definition of culture conditions that enable cell and progenitor expansion, has lead to the first clinical trials using cultured cells in addition to or in place of unmanipulated cells. The use of ex vivo expanded cells can improve several aspects of autologous and allogeneic hematopoietic cell and progenitor transplantation, such as reducing or abolishing the nadir that follows high-dose chemoradiation therapy regimens, or reducing the clinical risks associated with the use of small numbers of progenitors as in cord blood transplantation and in autologous transplantation for poor mobilizers. In addition, biological questions raised by ex vivo expansion are shared by scientists and clinicians interested in gene transfer into hematopoietic stem cells. We here review the biological problems associated with ex vivo expansion: defining efficient culture conditions, considering not only scientific and biological issues but also regulatory and commercial issues, defining appropriate surrogate endpoints that predict engraftment and superior clinical efficacy to that obtained with the use of unmanipulated grafts. We also review the results of the first clinical trials that have demonstrated the feasibilty of this approach, and have shown some of its limitations; demonstration of clinical efficacy will require more preclinical and clinical work.

Thrombopoietin augments ex vivo expansion of human cord blood-derived hematopoietic progenitors in combination with stem cell factor and flt3 ligand.

We studied the effects of stem cell factor (SCF) and flt3 ligand (FL) on the ex vivo expansion of human umbilical cord blood (CB)-derived CD34+ cells in combination with various cytokines, including interleukin (IL)-3, IL-6, IL-11, and c-Mpl ligand (thrombopoietin, TPO), in a short-term serum-free liquid suspension culture system. Among the two-factor combinations tested, SCF plus IL-3 most effectively expanded committed progenitor cells, including mixed colony-forming units (CFU-Mix). The expansion efficiency (EE) of FL for each progenitor was inferior to that of SCF in the presence of various cytokines, except TPO. IL-6 significantly increased the EE for granulocyte/macrophage colony-forming units (CFU-GM) obtained with SCF + IL-3 or FL + IL-3. Interestingly, TPO markedly augmented the EE for committed progenitors, including CFU-GM, erythroid burst-forming units (BFU-E), and CFU-Mix, in the presence of SCF + IL-3 or FL + IL-3. The combinations of SCF + IL-3 + TPO + IL-6 or IL-11 maximally stimulated the expansion of committed progenitors. The maximum EE for CFU-GM, BFU-E, and CFU-Mix was respectively 197-fold (day 14), 60-fold (day 7) and 51-fold (day 14). Other combinations of cytokines without IL-3 failed to expand effectively these committed progenitors. Our data demonstrate that it is possible to expand human CB-derived committed progenitors in vitro using SCF or FL with several other cytokines including TPO, and that IL-3 is the key cytokine promoting the expansion of human hematopoietic progenitors in the presence of SCF or FL.