Abstract
Both in malignant and non-malignant disorders stem cell based therapies are increasingly being utilized with promising results. hematopoietic reconstitution comprises mainly of 3 types of cells bone marrow (BM), peripheral blood (PB), and umbilical cord blood (UCB). The readily available and abundant resource of stem cell is umbilical cord blood. However, the typical single UCB unit could fetch relatively low numbers of hematopoietic stem- and progenitor cells (HSPCs) and the associated delay in procuring them restrict its routine applicability. In the past decade, the clinical applications of UCBbased cell therapies have broadened with a growing number of diseases treated with hematopoietic stem cell (HSC) transplantation. The assessment of UCB unit hematopoietic stem cells (HSCs), such as CD34+ cells or CFUs (Colony forming units), may provide a more direct estimate of the hematopoietic potential of the unit than the TNC count. As interlaboratory standardization of these assays has been achieved, the selection of UCB units for banking based on quantitation of hematopoietic progenitors is currently not feasible. However, CFU assays provide the only reliable assessment of the viability of the CB unit, although great efforts have been made to develop flow cytometry methods for viability staining. Despite of extreme efforts to find strategies that would enable the ex vivo amplification of stem cells for transplantation globally, it has been proven difficult to culture the HSCs in the labs. Therefore, it is imperative to have clear understanding regarding integration of HSC self-renewal, proliferation, and differentiation, molecules participating in their regulation and clinical benefit after their modification. Attempts have been made to improve the quality of UCB units through e.g. standardization of bank procedures, of stem cell enumeration, and of the assessment of HPCs viability. Over 4000000 UCB units are currently available in international registries. However, a significant proportion of patients is still left without a suitable donor, necessitating further development of UCB banking process.

Key words: Umbilical Cord Blood, hematopoietic stem cells