## 3 Results  
### Identification of Umbilical Cord-Derived Cells  
Cells were effectively isolated by the above-described explant method from the WJ and SA (Figure 1A). Approximately 48 to 72 h after starting the cultures, the first migratory cells were observed (Figure 1B). The cells grew out of explant pieces and displayed a fibroblast-like and spindle-shaped morphology. A small amount of large polygonal, flattened cells were observed as well. All cells were firmly attached to the culture plastic, proliferated, and reached over 40% confluence after an average of 8-10 days (\(n=6\)). Then, the explants were transferred to new wells and culture for another 10 days. The cells formed a dense \begin{table}
\begin{tabular}{c c c c} \hline \hline
**Gene Name** & **Forward Primer (5\({}^{\prime}\) to 3\({}^{\prime}\))** & **Reverse Primer (5\({}^{\prime}\) to 3\({}^{\prime}\))** & **Ta (\({}^{\circ}\)O)** \\ \hline _oct4a_ & AGTGAGAGCCAACCTGAGA & GTGAAAGTGAGGCTTCCATA & 60 \\ _oct4b_ & TATGGGGACCCCTCAC & CAAAAACCCTGGCACAAACT & 60 \\ _oct4b1_ & _AGACTATTCCTTGGGCCACACAC_ & GGCTGAATACCTTCCCAAATAGA & 63 \\ _sox2_ & _ACACACACATCCCACACACT_ & GCAAACTTCCTGCAAAAGCTC & 60 \\ _nanog_ & _GTCCGGTCAAGACAGA_ & TGCGTCACACACATTGCCTATT & 60 \\ _\(\beta\)-actin_ & _TGACGGGTCACCCACACACCTGCCCATCTA_ & CTAGAAGCATTTCCGGACACATGGAGGG & 62 \\ \hline \hline \end{tabular}
\end{table} 
Table 1: Sequences of the oligonucleotide primers used for RT-PCR. monolayer around 16-18 days. The number of WJ-MSCs was 5-6 \(\times\) 10\({}^{4}\) cells/cm\({}^{2}\), while 3-4 \(\times\) 10\({}^{4}\) cells/cm\({}^{2}\) were obtained for SA-MSCs (passage 0). An analysis of the MSC morphology in culture (length and width) revealed significant differences in length between WJ-MSCs and SA-MSCs (Figure 2). In comparison to SA-MSCs (mean/median 129/128 \(\upmu\)m), WJ-MSCs (mean/median 149/154 \(\upmu\)m) were longer (\(p<0.05\)). There was no significant difference in the width of WJ-MSCs (mean/median 34/25 \(\upmu\)m) and SA-MSCs (mean/median 41/35 \(\upmu\)m). WJ-MSCs showed a higher polarity index (mean/median 5,7/6,6), as there were more elongated cells (\(p<0.005\)). The lower polarity index of SA-MSCs (mean/median 3,9/3,5) indicates a more rounded cell shape. To overcome variations in cells caused by the difference in the passage number, all experiments were conducted on cells at passage 3, except some flow cytometric analyses that were performed up to the 5 th passage. During the cultivation period between the cells obtained from the WJ and SA, no significant morphological differences were observed. The cells isolated from the WJ and SA were harvested and subjected to immunophe-notyping. They were \(>\) 95% positive for the thymocyte differentiation antigen-1 CD90, the ecto-5\({}^{\prime}\)-nucleotidase CD73, b1-integrin CD29, and Class I histocompatibility protein HLA-ABC. A flow cytometric analysis was negative for the primitive hematopoietic progenitor and endothelial cell marker CD34, the pan-leukocyte marker CD45, and class II histocompatibility molecule HLA-DR (Figure 3). Figure 1: An overview of the isolation of WJ-MSCs and SA-MSCs. (**A**) Histology of human umbilical cord. (**B**) Morphology of cells derived from tissue explant technique. Primary explant cultures from human WJ and SA explants at early stage outgrowth at 2 and 8 days after explantation. Cell reached over 80% confluence after 16 days in culture. Scale bar = 200 \(\upmu\)m.  
Figure 2: The morphological characteristics of SA-MSCs (\(n=220\)) and WJ-MSCs (\(n=205\)) were analyzed 24 h after passaging (P3). Values were obtained from three pairs isolated from the same UC. SA-MSCs have a longer length, a higher polarity index, and a similar width to WJ-MSCs. Indicated statistical significance represents \(p<0.05\) *, \(p<0.01\) **, and a non-significant value is expressed as ’ns’ in the graph. To examine the differentiation potential of the WJ- and SA-derived cells, osteogenic and adipogenic differentiations were used.