Mesenchymal Stem Cells in the Wharton’s Jelly of the Human Umbilical Cord

Abstract: The Wharton’s jelly of the umbilical cord contains mucoid connective tissue and fibroblast-like cells. Using flow cytometric analysis, we found that mesenchymal cells isolated from the umbilical cord express matrix receptors (CD44, CD105) and integrin markers (CD29, CD51) but not hematopoietic lineage markers (CD34, CD45). Interestingly, these cells also express significant amounts of mesenchymal stem cell markers (SH2, SH3).

We therefore investigated the potential of these cells to differentiate into cardiomyocytes by treating them with 5-azacytidine or by culturing them in cardiomyocyte conditioned medium and found that both sets of conditions resulted in the expression of cardiomyocyte markers, namely N-cadherin and cardiac troponin I. We also showed that these cells have multilineage potential and that, under suitable culture conditions, are able to differentiate into cells of the adipogenic and osteogenic lineages.

These findings may have a significant impact on studies of early human cardiac differentiation, functional genomics, pharmacological testing, cell therapy, and tissue engineering by helping to eliminate worrying ethical and technical issues.

Introduction: The umbilical cord contains two arteries and one vein, which are surrounded by mucoid connective tissue, and this is called the Wharton’s jelly. The cord is covered by an epithelium derived from the enveloping amnion.

The network of glycoprotein microfibrils and collagen fibrils in the Wharton’s jelly has been previously studied [1]. The interlaced collagen fibers and small, woven bundles are arranged to form a continuous soft skeleton that encases the umbilical vessels [2]. In the Wharton’s jelly, the most abundant glycosaminoglycan is hyaluronic acid [3], which forms a hydrated gel around the fibroblasts and collagen fibrils and maintains the tissue architecture of the umbilical cord by protecting it from pressure [4]. The phenotypic stromal cells in the Wharton’s jelly are fibroblast-like cells [5]. However, cells with the ultrastructural characteristics of myofibroblasts have been found [6]. Recently, Mitchell et al. [7] found that matrix cells from Wharton’s jelly can be induced to form neurons and glia cells by treating with basic fibroblast growth factor and low-serum media plus butylated hydroxyanisole and dimethyl sulfoxide.

In this study, we demonstrate that mesenchymal cells from the umbilical cord, when expanded in culture, express adhesion molecules (CD44, CD105), integrin markers (CD29, CD51), and mesenchymal stem cell (MSC) markers (SH2, SH3) but not markers of hematopoietic differentiation (CD34, CD45). After exposure of these cells to cardiomyocyte- conditioned medium or 5-azacytidine, they expressed cardiac troponin-I and N-cadherin, indicating differentiation into cardiomyocytes. Under suitable culture conditions, these cells could also differentiate into osteogenic and adipogenic cells.

Thus, human umbilical cord mesenchymal cells can be expanded in culture and induced to form several different types of cells. They may therefore prove to be a new source of cells for cell therapy, including targets such as stromal tissue and cardiac muscle. This will help to avoid several ethical and technical issues.