Stem cells: Haemobiology and clinical data summarising: A critical review

Abstract

Stem cells (SC) are the unique and "key-cells" in the human body "working" as a source of producing a large number (proliferation) of mature (differentiation) cells inside different tissues ("cytopoiesis") - while at the same time maintaining the ability to "reproduce" themselves (self-renewal). These events are balanced by interactive signals from the extracellular matrix, as well as microenvironment provided by stromal cells. On the other hand, SC plasticity (so-called "inter-systemic plasticity") is the ability of the most "primitive" (immature) adult SCs to switch to novel identities. The phrase SC plasticity also involves phenotypic potential of these cells, broader than spectrum of phenotypes of differentiated cells in their original tissues. Recent increasing clinical use of cell-mediated therapeutic approaches has resulted in enlarged needs for both, higher quantity of SCs and improved operating procedures during extracorporeal manipulations. The aim of harvesting procedures is to obtain the best SC yield and viability. The goal of optimised cryopreservation is to minimise cellular thermal damages during freeze/thaw process (cryoinjury). Despite the fact that different SC collection, purification and cryopreservation protocols are already in routine use - a lot of problems related to the optimal SC extracorporeal manipulations are still unresolved. The objective of this paper is to provide an integral review of early haemobiological and cryobiological research in the unlimited "SC-field" with emphasis on their entities, recent cell-concepts, extracorporeal manipulative and "graft-engineering" systems. Their therapeutic relevance and efficacy in "conventional" SC transplants or regenerative medicine will be briefly summarised. Finally, in this paper original results will not be pointed out - related to neither SC transplants nor regenerative medicine - but a light will be shed on some of them.