Mesenchymal and Induced Pluripotent Stem Cells - General Outline

**3**

**Chapter 1**

Introductory Chapter: Update

on Mesenchymal and Induced

Stem cells are a subset of biological cells in the human body that are capable of self-renewal, tissue repair, differentiation, and division into different cell lineages [1–3]. Based on their origin and potency, stem cells are divided into either (1) embryonic and adult (non-embryonic) stem cells or (2) unipotent, oligopotent, totipotent, multipotent, and pluripotent stem cells [1, 2, 4, 5]. Multipotent or adult stem cells include mesenchymal stem cells (MSCs), while pluripotent stem cells include embryonic stem cells (ESCs) and induced pluripotent stem cells (iPSCs) [5].

MSCs are heterogeneous, non-hematopoietic, adult multipotent stromal progenitor cells that are capable of self-renewal and differentiation into multiple lineages and various cell types [6–12]. They were first described in the 1960s by Alexander Friedenstein [7, 8, 10, 13]. They can be isolated from the bone marrow (BM), peripheral blood, umbilical cord blood, amniotic fluid, placenta, adipose tissue (AT), dental pulp, palatal tonsil, synovial fluid, salivary glands, as well as liver, lung, skin, and skeletal muscle tissues [6–13]. The main source of MSCs is the BM although MSCs constitute only a small fraction of the total number of cells populat-

MSCs have certain distinguishing features: being plastic adherent and ability of differentiation into osteoblasts, adipocytes, and chondrocytes, in addition to having characteristic surface markers [6–8, 10, 11, 13, 14]. On flow cytometry, they are characteristically positive for CD105, CD73, and CD90 and negative for CD45, CD34, CD11b, CD14, CD19, CD79a, and HLA-DR [6–8, 10, 11, 13]. However, several studies have shown that MSCs obtained from BM, AT, and other sources do express CD34 surface markers [9, 15–18]. MSCs can be seen in abundant numbers in the circulation under the following circumstances: stem cell mobilization with growth factors, tissue injuries, stroke, hypoxia, and inflammatory conditions [9, 19–24]. Despite the efforts made over the last five decades including identification of nine transcriptional factors, little is known about the molecular basis underlying the stemness of MSCs, and it is still unclear whether the recently discovered genes regulate stemness

MSCs have immunomodulatory and immunosuppressive properties that enable

them to have several therapeutic and clinical applications, which include the enhancement of engraftment as well as prevention and treatment of graft versus

Pluripotent Stem Cells

*Khalid Ahmed Al-Anazi*

**1. Introduction**

**2. MSCs**

ing the BM [7, 9–11].

or only differentiation of MSCs [12].

### **Chapter 1**
