Intersecting Worlds of Transfusion and Transplantation Medicine: An International Symposium Organized by the Canadian Blood Services Centre for Innovation

The principal theme of the symposium was centered on how the world of regenerative medicine intersects with that of transfusion medicine, with a particular focus on hematopoietic stem cells (HSCs) and stem cell therapies. The symposium highlighted several exciting developments and identified areas where additional research is needed. A revised map of human hematopoietic hierarchy was presented based on the functional and phenotypic analysis of thousands of single stem and progenitor cells from adult bone marrow and fetal liver. These analyses revealed that multipotency is largely restricted to the HSC and multipotent progenitor compartments in adult bone marrow where most progenitors are unipotent, whereas fetal liver contains a large number of distinct oligopotent progenitors. Furthermore, unlike adult bone marrow, multipotency is extended in the downstream progenitors in the hierarchy in the fetal liver stage. Production of platelets ex vivo from HSCs is emerging as a potentially viable option because of advances in culture techniques that combine cytokine mixtures, small molecules, and shear stress. However, limited HSC expansion and low platelet yield from culture-derived megakaryocytes remain problematic. Evidence was presented to support stricter guidelines for transfusion of platelets and red blood cells practices in allogeneic HSC transplant patients, although evidence is often extrapolated from general indications. Basic principles of human leukocyte antigen testing in HSC transplant were described, emphasizing the need for a national (and global) stem cell donor registry. Ongoing research is aimed at improving cellular cryopreservation including the establishment of a new thawing protocol that improves viability of umbilical cord blood CD34+ cells. Umbilical cord blood transplantation practices have also been improved; recent studies suggest noninferior outcomes when patients are transplanted with umbilical cord blood vs a matched adult donor. Finally, mesenchymal stem cell infusion is an example of a cellular therapy useful for immunomodulation. Preclinical trials suggest that mesenchymal stem cells may be effective in managing sepsis. In conclusion, practices and research surrounding HSCs are continuing to evolve rapidly as new information is obtained.