3. Sources

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

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

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

MSCs are multipotent stromal cells that can differentiate into a variety of cell types, including: osteoblasts (bone cells), chondrocytes (cartilage cells), myocytes (muscle cells) and adipocytes (fat cells which give rise to marrow adipose tissue). MSCs exist in organisms (in-vivo) and have

Due to the lack of a particularly unique MSCs function, they have been termed 'mesenchymal stem cells' or interchangeably 'mesenchymal stromal cells', 'BM (bone marrow) stromal cells' and 'marrow stromal cells'. MSCs are usually identified by mere plastic adherence and by their morphological appearance, such as the fibroblastoid phenotype. This procedure leads to a diverse population containing both single stem cell-like cells and progenitor cells having various lineage commitment. Compared to hematopoietic stem cells (HSCs), which have been proven to repopulate the bone marrow and give all blood types, and embryonic stem cells (ESCs) which after re-injection into early embryos, were proven to participate in embryonic

In 1970, Friedenstein and colleagues were the first who identified mesenchymal stem cells as colony-forming unit-fibroblasts (CFU-Fs) [4]. Pittenger and colleagues were the first to desc-

The first clinical trials of MSCs were completed in 1995 when a group of 15 patients were

controversy represent an obstacle in their research and clinical application.

mesenchymal cells demonstrating stem cell activity by accurate criteria.

development of all tissues; MSCs have no established in vivo tests [3].

injected with cultured MSCs to test the safety of the treatment [1].

currently the most used in regenerative medicine.

4 Stromal Cells - Structure, Function, and Therapeutic Implications

been studied as well in tissue culture (in-vitro) [2].

1.1. Definition

1.2. Terminology

2. History

ribe the tri-lineage potential of MSCs [3].
