Although stem cells are used as important cell therapies in regenerative medicine, the electrophysiological problems that arise in the expansion of cells have not been known much. This study was conducted to investigate the functional expression of inward rectifying K+ current (IKir) using a patch-clamp technique, and the change in the resting membrane potential and the membrane capacitance were investigated in mesenchymal stem cells derived from human umbilical vein (hUC-MSC). The IKir plays an important role in regulating the resting membrane potential in many cells and is known to contribute to the maintenance of intracellular K+ concentration. In this study, electrophysiologically recorded current exhibited typical IKir characteristics. The current shifted along the K+ equilibrium potential (Ek) with the extracellular K+ concentration change. In addition, IKir was blocked by the divalent Ba2+ in a dose-dependent manner. The frequency of functional expression of IKir changed with number of passages (P2: 5.3% vs P8: 77.8% vs P12: 34.5%). There was no significant change in the resting membrane potential of hUC-MSC (P2: -21.0 mV, P8: -20.1 mV and P12: -21.9 mV). However, the capacitance of the cell membrane was significantly changed after P9 (P2: 8.9 pF vs P9: 16.9 pF) compared to P2. All the results suggest that changes in electrophysiological distribution of IKir as the passages increase may cause changes in K+ permeability even in cell proliferation and differentiation, suggesting a possible physiological role in maintaining cell homeostasis and resting membrane potential (RMP).

One of the most extensively studied populations of multipotent adult stem cells are mesenchymal stem cells (MSCs). MSCs derived from the human umbilical cord vein (HUC-MSCs) are morphologically and immunophenotypically similar to MSCs isolated from bone marrow. HUC-MSCs are multipotent stem cells, differ from hematopoietic stem cells and can be differentiated into neural cells. Since neural tissue has limited intrinsic capacity of repair after injury, the identification of alternate sources of neural stem cells has broad clinical potential. We isolated mesenchymal-like stem cells from the human umbilical cord vein, and studied transdifferentiation-promoting conditions in neural cells. Dopaminergic neuronal differentiation of HUC-MSCs was also studied. Neural differentiation was induced by adding bFGF, EGF, dimethyl sulfoxide (DMSO) and butylated hydroxyanisole (BHA) in N2 medium and N2 supplement. The immunoreactive cells for -tubulin III, a neuron-specific marker, GFAP, an astrocyte marker, or Gal-C, an oligodendrocyte marker, were found. HUC-MSCs treated with bFGF, SHH and FGF8 were differentiated into dopaminergic neurons that were immunopositive for tyrosine hydroxylase (TH) antibody. HUC-MSCs treated with DMSO and BHA rapidly showed the morphology of multipolar neurons. Both immunocytochemistry and RT-PCR analysis indicated that the expression of a number of neural markers including NeuroD1, -tubulin III, GFAP and nestin was markedly elevated during this acute differentiation. While the stem cell markers such as SCF, C-kit, and Stat-3 were not expressed after neural differentiation, we confirmed the differentiation of dopaminergic neurons by TH/-tubulin III positive cells. In conclusion, HUC-MSCs can be differentiated into dopaminergic neurons and these findings suggest that HUC-MSCs are alternative cell source of therapeutic treatment for neurodegenerative diseases.

Adult stem cells can make identical copies of themselves for long periods of time. They also give rise to many differentiated mature cell types that have characteristic morphology and specialized function. Human adult stem cells are the attractive raw materials for the cell/tissue therapy, however, it is not easy to get from the adult tissues. In the present study, we tried to isolate a cell population derived from human umbilical cord vein which has been discarded after birth. The cells were isolated after treatment of the umbilical vein with collagenase or trypsin. After 3 days of culture, two kinds of cell populations were found consisting of adherent cells with endothelial cell-like and fibroblast-like morphology, respectively. When these cells were subcultured 12 times over a period of 3 months, almost cells appeared uniformly to exhibit fibroblastoid morphology which was different from that of mesenchymal stem cells obtained from human bone marrow The results of RT-PCR analyses showed distinct expression of BMP-4, oct-4, and SCF genes but not of GATA, PAX-6 and Brachyury genes. On immunohistochemical staining, the cells were negative for the von Willebrand factor(vWF), alpha-smooth muscle actin and placental alkaline phosphatase. From these observations, it is suggested that stem-like cells might be present in human umbilical cord vein.