The umbilical cord contains an inexhaustible, noncontroversial source of stem cells for therapy. In the U.S., stem cells found in the umbilical cord are routinely placed into biohazardous waste after birth. Here, stem cells derived from human umbilical cord Wharton's Jelly, called umbilical cord matrix stem (UCMS) cells, are characterized. UCMS cells have several properties that make them of interest as a source of cells for therapeutic use. For example, they 1) can be isolated in large numbers, 2) are negative for CD34 and CD45, 3) grow robustly and can be frozen/thawed, 4) can be clonally expanded, and 5) can easily be engineered to express exogenous proteins. UCMS cells have genetic and surface markers of mesenchymal stem cells (positive for CD10, CD13, CD29, CD44, and CD90 and negative for CD14, CD33, CD56, CD31, CD34, CD45, and HLA-DR) and appear to be stable in terms of their surface marker expression in early passage (passages 4 -8). Unlike traditional mesenchymal stem cells derived from adult bone marrow stromal cells, small populations of UCMS cells express endoglin (SH2, CD105) and CD49e at passage 8. UCMS cells express growth factors and angiogenic factors, suggesting that they may be used to treat neurodegenerative disease. To test the therapeutic value of UCMS cells, undifferentiated human UCMS cells were transplanted into the brains of hemiparkinsonian rats that were not immune-suppressed. UCMS cells ameliorated apomorphine-induced rotations in the pilot test. UCMS cells transplanted into normal rats did not produce brain tumors, rotational behavior, or a frank host immune rejection response. In summary, the umbilical cord matrix appears to be a rich, noncontroversial, and inexhaustible source of primitive mesenchymal stem cells. STEM CELLS 2006;24:781-792

STEM CELLS 2008;26:591-599 Disclosure of potential conflicts of interest is found at the end of this article.

We have identified an easily attainable source of primitive, potentially multipotent stem cells from Wharton's jelly, the matrix of umbilical cord. Wharton's jelly cells have been propagated in culture for more than 80 population doublings. Several markers for stem cells, including c-kit (CD117), and telomerase activity are expressed in these cells. Treatment with basic fibroblast growth factor overnight and low-serum media plus butylated hydroxyanisole and dimethylsulfoxide induced Wharton's jelly cells to express a neural phenotype. Within several hours of this treatment, Wharton's jelly cells developed rounded cell bodies with multiple neurite-like extensions, similar to the morphology of neural stem cells. Neuron-specific enolase (NSE), a neural stem cell marker, was expressed in these cells, as shown by immunocytochemistry. Immunoblot analysis showed similar levels of NSE expression in both untreated and induced Wharton's jelly cells. After 3 days, the induced Wharton's jelly cells resembled bipolar or multipolar neurons, with processes that formed networks reminiscent of primary cultures of neurons. The neuron-like cells in these cultures stained positively for several neuronal proteins, including neuron-specific class III beta-tubulin, neurofilament M, an axonal growth-cone-associated protein, and tyrosine hydroxylase. Immunoblot analysis showed increasing levels of protein markers for mature neurons over time post induction. Markers for oligodendrocytes and astrocytes were also detected in Wharton's jelly cells. These exciting findings show that cells from the matrix of umbilical cord have properties of stem cells and may, thus, be a rich source of primitive cells. This study shows their capacity to differentiate into a neural phenotype in vitro.

Cells isolated from Wharton's jelly, referred to as umbilical cord matrix stromal (UCMS) cells, adhere to a tissue-culture plastic substrate, express mesenchymal stromal cell (MSC) surface markers, self-renew, and are multipotent (differentiate into bone, fat, cartilage, etc.) in vitro. These properties support the notion that UCMS cells are a member of the MSC family. Here, the immune properties of UCMS cells are characterized in vitro. The overall hypothesis is that UCMS cells possess immune properties that would be permissive to allogeneic transplantation. For example, UCMS cells will suppress of the proliferation of "stimulated" lymphocytes (immune suppression) and have reduced immunogenicity (e.g., would be poor stimulators of allogeneic lymphocyte proliferation). Hypothesis testing was as follows: first, the effect on proliferation of coculture of mitotically inactivated human UCMS cells with concanavalin-A-stimulated rat splenocytes was assessed in three different assays. Second, the effect of human UCMS cells on one-way and two-way mixed lymphocyte reaction (MLR) assays was determined. Third, the expression of human leukocyte antigen (HLA)-G was examined in human UCMS cells using reverse transcription-polymerase chain reaction, since HLA-G expression conveys immune regulatory properties at the maternal-fetal interface. Fourth, the expression of CD40, CD80, and CD86 was determined by flow cytometry. Fifth, the cytokine expression of UCMS cells was evaluated by focused gene array. The results indicate that human UCMS cells inhibit splenocyte proliferation response to concanavalin A stimulation, that they do not stimulate T-cell proliferation in a one-way MLR, and that they inhibit the proliferation of stimulated T cells in a two-way MLR. Human UCMS cells do not inhibit nonstimulated splenocyte proliferation, suggesting specificity of the response. UCMS cells express mRNA for pan-HLA-G. UCMS cells do not express the costimulatory surface antigens CD40, CD80, and CD86. UCMS cells express vascular endothelial growth factor and interleukin-6, molecules previously implicated in the immune modulation observed in MSCs. In addition, the array data indicate that UCMS cells make a cytokine and other factors that may support hematopoiesis. Together, these results support previous observations made following xenotransplantation; for example, there was no evidence of frank immune rejection of undifferentiated UCMS cells. The results suggest that human UCMS will be tolerated in allogeneic transplantation.

Stem cells are the next frontier in medicine. Stem cells are thought to have great therapeutic and biotechnological potential. This will not only to replace damaged or dysfunctional cells, but also rescue them and/or deliver therapeutic proteins after they have been engineered to do so. Currently, ethical and scientific issues surround both embryonic and fetal stem cells and hinder their widespread implementation. In contrast, stem cells recovered postnatally from the umbilical cord, including the umbilical cord blood cells, amnion/placenta, umbilical cord vein, or umbilical cord matrix cells, are a readily available and inexpensive source of cells that are capable of forming many different cell types (i.e., they are "multipotent"). This review will focus on the umbilical cord-derived stem cells and compare those cells with adult bone marrow-derived mesenchymal stem cells.