Mobilization and collection of autologous hematopoietic progenitor/stem cells.

Autologous hematopoietic progenitor/stem cell (HPC) transplantation has become a standard treatment for a wide variety of malignancies. Most HPCs at present are collected from the peripheral blood via leukapheresis following chemotherapy and/or growth factor-mediated mobilization. Several commercial platforms are available to enumerate the circulating levels of CD34+ HPCs. These values can then be used to guide the timing of leukapheresis as well as to measure the success of daily collections. Most mobilization regimens consist of chemotherapy followed by one or more growth factors such as granulocyte colony-stimulating factor, granulocyte-macrophage colony-stimulating factor, erythropoietin, or AMD3100. Occasionally a subset of patients will prove unable to mobilize effectively enough to collect at least 2 x 106 CD34+ cells/kg, the number of HPCs currently considered to be appropriate for timely engraftment and recovery of hematopoiesis. In this subset of patients, repeat HPC collection or marrow harvest with or without growth factor stimulation may be tried. The importance of the stem cell niche in mobilization, in particular the relationship of osteoblasts and the sympathetic nervous system in the release of HPCs and other cells from the marrow stroma, may lead to entirely different or improved methods of mobilization in the future. Recent research has explored the benefits of using HPCs outside of the oncology arena, notably in the area of cardiac myocyte regeneration following infarction, making the subject of mobilization potentially important to physicians in many areas of medicine.