**2. General aspects of MSCs**

MSCs are adult stem cells with self-renewing and differentiation abilities. These cells can be isolated from different sources (bone marrow, adipose tissue, umbilical cord (UC), and amniotic fluid) and are easily preserved without raising any ethical issue [21]. Mammalian bone marrow is the best understood niche that harbors hematopoietic stem cells (HSCs), and MSCs are believed to provide the basis for the physical structures of the niche [22]. Moreover, MSCs are defined as multipotent cells that are thought to regulate the self-renewal, proliferation, and differentiation of the HSCs through the production of cytokines and intracellular signals that are initiated by cell-to-cell interaction. Lastly, MSCs can differentiate into cells from different lineages, such as osteoblasts, cartilage cells, fibroblasts, muscle cells, fat cells, and neurons [23, 24].

#### **3. Markers of MSCs**

Most researchers have suggested minimal criteria to define MSCs. The International Society for Cellular Therapy (ISCT) established specific criteria in order to identify unique populations of MSCs [25].

1.MSCs must be plastic adherent when maintained under standard culture conditions.

