1. Introduction

Stem cells have the ability of self-renewal, giving rise to a variety of cell lineages. They constitute a significant paradigm of cell-based therapy for various diseases.

© 2016 The Author(s). Licensee InTech. This chapter is distributed under the terms of the Creative Commons Attribution License (http://creativecommons.org/licenses/by/3.0), which permits unrestricted use, distribution, and eproduction in any medium, provided the original work is properly cited. © 2018 The Author(s). Licensee IntechOpen. This chapter is distributed under the terms of the Creative Commons Attribution License (http://creativecommons.org/licenses/by/3.0), which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited.

Embryonic and non-embryonic stem cells, are the two principal types of stem cells. Embryonic stem cells (ESCs) originate from the blastocyst's inner cell mass and have the ability for differentiation into cells of all three germ layers. However, teratoma formation and ethical controversy represent an obstacle in their research and clinical application.

3. Sources

3.1. Bone marrow

3.2. Adipose tissue

3.3. Peripheral blood

3.4. Umbilical cord blood

4. Characteristics

following three criteria [8]:

were identified as mesenchymal stem cells.

entiate into cell types of all 3 germ layers [7].

BM-MSCs are isolated from bone marrow aspirate. This invasive procedure is painful for the patient with a risk of infection. The commonly used method for the generation of MSCs from bone marrow is density gradient centrifugation [3]. The collected fraction containing mononu-

Stromal Stem Cells: Nature, Biology and Potential Therapeutic Applications

http://dx.doi.org/10.5772/intechopen.77346

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AT-MSC also termed as adipose-derived stem cells are usually isolated from the biological material generated during liposuction, lipoplasty or lipectomy procedures by enzymatic diges-

Following a density gradient centrifugation, PB-MSC can be collected from the mononuclear cells' lymphocyte separation fluid fraction. Kassis et al. [6] described another method, which is loading PB-MSC on fibrin microbeads, then separating the cell loaded beads from the mono-

Pittenger et al. [3], isolated MSCs from BM by density gradient centrifugation to eliminate unwanted cell types and only 0.001 to 0.01% of the cells isolated from the density interface

As umbilical cord blood contains MSCs, it could serve as an alternative source of MSCs to bone marrow. A novel method to obtain single cell-derived and clonally expanded MSCs that have multilineage differentiation potential, is negative immunoselection and limiting dilution. The immunophenotype of these clonally expanded cells is similar with bone marrow mesenchymal stem cells. These cells can differentiate into bone, cartilage, and fat under suitable induction conditions. These cells were also able to differentiate into neuroglial- and hepatocyte-like cells; therefore, these cells may be more than mesenchymal stem cells due to their ability to differ-

In 2006, the International Society of Cellular Therapy defined characterization of MSCs by the

1. MSCs must be adherent to plastic under standard tissue culture conditions;

clear cells is washed and the cells are seeded on a plastic dish for proliferation.

nuclear fraction. This method allows getting enormous amounts of MSCs [6].

tion with collagenase followed by centrifugation and washing [5].

On the other side, non-embryonic stem cells, mostly adult stem cells, are fairly specialized and have limited differentiation potential. They can be isolated from various tissues and are currently the most used in regenerative medicine.

Over the last decade, cellular therapy has developed quickly at the level of in vitro and in vivo preclinical research and in clinical trials. Mesenchymal stem cells (MSCs), one type of adult stem cells, have provided a great amount of interest in the field of regenerative medicine due to their unique biological properties [1]. The acronym "MSCs" is restricted to the subset of mesenchymal cells demonstrating stem cell activity by accurate criteria.
