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Extensive amplification and self-renewal of human primitive hematopoietic stem cells from cord blood
W Piacibello1, F Sanavio, L Garetto
1Department of Biomedical Sciences, Torino Medical School, University of Torino, Italy.
Insights
Umbilical cord blood stem cells can be significantly expanded ex vivo using a two-growth-factor system. This method sustains primitive hematopoietic progenitors for over six months, enabling potential adult transplantation.
Area of Science:
- Hematology
- Stem Cell Biology
- Transplantation Medicine
Background:
- Umbilical cord blood (UCB) is an established source of hematopoietic stem cells for pediatric malignancies.
- UCB offers advantages in availability and procurement over bone marrow or peripheral blood stem cells.
- A key limitation for UCB use in adults is the potentially insufficient number of hematopoietic stem cells for engraftment.
Purpose of the Study:
- To develop an in vitro system for expanding UCB-derived hematopoietic stem cells.
- To overcome the limitation of cell numbers for adult transplantation using UCB.
- To investigate the sustained growth and differentiation potential of UCB CD34+ cells ex vivo.
Main Methods:
- Culturing CD34+ cells from UCB in vitro.
- Utilizing a combination of two specific hematopoietic growth factors.
- Monitoring cell expansion and lineage potential over a 6-month period.
Main Results:
- Sustained and massive expansion of UCB CD34+ cells for over 6 months.
- Continuous generation of progenitors across all hematopoietic lineages, with over 2,000,000-fold increase in CFU-GM.
- Significant expansion of primitive progenitors, including LTC-ICs (over 200,000-fold increase after 20 weeks).
Conclusions:
- The described in vitro system enables extensive expansion and prolonged maintenance of hematopoietic stem cell progenitors from UCB.
- The expanded cells exhibit characteristics similar to murine long-term repopulating cells, suggesting self-renewal capacity.
- This expansion system holds promise for clinical applications in adult transplantation of normal or genetically modified hematopoietic stem cells.
Abstract:
The use of umbilical cord blood as a source of marrow repopulating cells for the treatment of pediatric malignancies has been established. Given the general availability, the ease of procurement, and progenitor content, cord blood is an attractive alternative to bone marrow or growth factor mobilized peripheral blood cells as a source of transplantable hematopoietic tissue. However, there is a major potential limitation to the widespread use of cord blood as a source of hematopoietic stem cells for marrow replacement and gene therapy. There may be enough hematopoietic stem cells to reconstitute children, but the ability to engraft an adult might require ex vivo manipulations. We describe an in vitro system in which the growth of cord blood CD34+ cells is sustained and greatly expanded for more than 6 months by the simple combination of two hematopoietic growth factors. Progenitors and cells belonging to all hematopoietic lineages are continuously and increasingly generated (the number of colony-forming unit-granulocyte-macrophage [CFU-GM] present at the end of 6 months of culture are well over 2,000,000-fold the CFU-GM present at the beginning of the culture). Very primitive hematopoietic progenitors, including long-term culture-initiating cells (LTC-ICs) and blast cell colony-forming units, are also greatly expanded (after 20 weeks of liquid culture, LTC-IC number is over 200,000-fold the initial number). The extremely prolonged maintenance and the massive expansion of these progenitors, which share many similarities with murine long-term repopulating cells, suggest that extensive renewal and little differentiation take place. This system might prove useful in diverse clinical settings involving treatment of grown-up children and adults with transplantation of normal or genetically manipulated hematopoietic stem cells.