IntroductionMesenchymal stem cells (MSCs) are self-renewing and multipotent cells, which have the potential to differentiate into various tissue cells, including osteoblasts (1,2), adipocytes, chondrocytes (3), neurons, glia cells (4), and cardiomyocytes (5), under favorable conditions. Owing to this potential, MSCs are being increasingly investigated for their use in cell-based regenerative medicine and tissue engineering (6).In recent years, MSCs have been reported to be isolated from various tissues, including adipose tissue, cartilaginous tissue, muscles, tendons, the periodontal ligament, synovial membranes, trabecular bone and bone marrow, umbilical cords, placentas, the nervous system, skin, the periosteum, fetal liver, and dental pulp (7-9).The umbilical cord (UC), which is of varying length in different species, is a transparent flexible tissue externally surrounded by the amniotic membrane and composed of three blood vessels, including two arteries and one vein, which are encapsulated by a mucous connective tissue referred to as Wharton's jelly (10). Although the umbilical cord appears to be homogeneous at macroscopic level, it has been shown to comprise three compartments on the basis of the proliferation and differentiation characteristics determined for expanded stromal cells. These compartments are the subamniotic stroma, intervascular stroma, and perivascular stroma (11).UC-derived MSCs can be isolated from Wharton's jelly, the perivascular stroma, and the subamniotic membrane (10,12). Human UC-derived MSCs offer several advantages, including their isolation being easier, noninvasive, and less contentious when compared to that of MSCs isolated from the bone marrow and adipose tissue, as well as their contamination risk being lower and their differentiation and immunomodulatory capacity being higher (13).Although several studies have been carried out to demonstrate various features of these cells, including their phenotypic characteristics and plasticity, the number of studies available on the ultrastructure of MSCs is rather limited. This study was aimed at determining the plasticity of UC-derived MSCs isolated from the rat and also at demonstrating, for the first time, the ultrastructural characteristics of these cells in detail.
Materials and methods
Isolation and expansion of umbilical cord-derived mesenchymal stem cellsUC samples were collected from the fetuses of pregnant Wistar albino rats under general anesthesia. Immediately