Methods of Hematopoietic Stem Cells Expansion in In Vitro

Hematopoietic stem cells are rare cells that have two unique specificity; self renewal and differentiation to all blood lineages. Hematopoietic stem cells are used in treatments of many diseases such as leukemia, congenital abnormalities related to blood and immune system, aplastic anemia. Bone marrow stem cells and mobilized stem cells are most common sources for transplantation; however using them because of the low availability to Human leukocyte antigen-compatible donors is limited. An alternative method for solving this problem is use of umbilical cord blood that can tolerate low incompatible donors. However the number of cells present in each unit of umbilical cord blood is not enough for transplantation for an adult. Now, many methods are utilized for Hematopoietic stem cells expansion in ex vivo like using cytokine cocktails, copper chelators, stromal support and gene transfer methods. Among them, the gene transfer approach was the most effective method. The genes used to increase the hematopoietic stem cells expansion by lentiviral vectors and recombinant proteins include HOXB4, WNT, Notch, BMP4, BMI-1 and SALL4 and recently has been shown that the microRNAs such as miR-125a/b, miR-17 and miR-29a are able to increase the ex vivo expansion of hematopoietic stem cells.