The Possibilities of Harvesting and the Modalities of Processing Hematopoetic Stem Cells

Hematopoietic stem cells are defined as cells with self-renewing capabilities that can differentiate into multiple cell liniages. In adults, the stem cells are part of the tissue-specific cells into which they are committed to differentiate. The embrionic stem cells are derived from embryos and have the ability to generate any cell in the body.
The adult hematopoietic stem cells are organized in a hierarchic tree, with multipotent, self-renewing stem cells at the base, the committed progenitor cells as the main branches and lineage restricted precursor cells as terminal branches. The lineage restricted stem cells give rise to terminally differentiated cells. The classic paradigm of organ-restricted stem cell differentiation is challenged by the possibility of the hematopoietic stem cells to retain a degree of plasticity that allows them to diffe-rentiate into any cell of the adult human body, according to the microenvironment [1].
The initial source for stem cells was the bone marrow. After transplantation of unselected cells in animals previously conditioned with chemotherapy/radiotherapy treatment there was evidence that not only hematopoietic tissue was generated by the transplanted cells, but also non-lymphohematopoietic tissue, such as hepatocytes, muscle fibers and neuronal tissue.
Since 1990 the main source of stem cells was the periphe-ral blood after mobilization with cytokine (granulocyte colony stimulating factor – G-CSF) with or without chemotherapy. Several investigators reported that human peripheral blood stem cells can generate also non-lymphohematopoietic tissue in the same way the cells from the marrow did.[More]