Umbilical cord blood stem cells can expand hematopoietic and neuroglial progenitors in vitro

The potential of umbilical cord blood multipotent stem cells for nonhematopoietic tissue and cell regeneration

Stem cells have been isolated from human embryos, fetal tissue, umbilical cord blood (UCB), and also from "adult" sources. Adult stem cells are found in many tissues of the body and are capable of maintaining, generating, and replacing terminally differentiated cells. A source of pluripotent stem cells has been recently identified in UCB that can also differentiate across tissue lineage boundaries into neural, cardiac, epithelial, hepatocytic, and dermal tissue. Thus, UCB may provide a future source of stem cells for tissue repair and regeneration. Its widespread availability makes UCB an attractive source for tissue regeneration. UCB-derived stem cells offer multiple advantages over adult stem cells, including their immaturity, which may play a significant role in reduced rejection after transplantation into a mismatched host and their ability to produce larger quantities of homogenous tissue or cells. While research with embryonic stem cells continues to generate considerable controversy, human umbilical stem cells provide an alternative cell source that has been more ethically acceptable and appears to have widespread public support. This review will summarize the in vitro and in vivo studies examining UCB stem cells and their potential use for therapeutic application for nonhematopoietic tissue and cell regeneration.

The potential of cord blood stem cells for use in regenerative medicine

It is estimated that up to 128 million individuals might benefit from regenerative medicine therapy, or almost 1 in 3 individuals in the US. If accurate, the need to relieve suffering and reduce healthcare costs is an enormous motivator to rapidly bring stem cell therapies to the clinic. Unfortunately, embryonic stem (ES) cell therapies are limited at present by ethical and political constraints and, most importantly, by significant biologic hurdles. Thus, for the foreseeable future, the march of regenerative medicine to the clinic will depend on the development of non-ES cell therapies. At present, non-ES cells easily available in large numbers can be found in the bone marrow, adipose tissue and umbilical cord blood (CB). Each of these stem cells is being used to treat a variety of diseases. This review shows that CB contains multiple populations of pluripotent stem cells, and can be considered the best alternative to ES cells. CB stem cells are capable of giving rise to hematopoietic, epithelial, endothelial and neural tissues both in vitro and in vivo. Thus, CB stem cells are amenable to treat a wide variety of diseases including cardiovascular, ophthalmic, orthopedic, neurologic and endocrine diseases.

Directed engineering of umbilical cord blood stem cells to produce C-peptide and insulin

OBJECTIVES

In this study, we investigated the potential of umbilical cord blood stem cell lineages to produce C-peptide and insulin.

MATERIALS AND METHODS

Lineage negative, CD133+ and CD34+ cells were analyzed by flow cytometry to assess expression of cell division antigens. These lineages were expanded in culture and subjected to an established protocol to differentiate mouse embryonic stem cells (ESCs) toward the pancreatic phenotype. Phase contrast and fluorescence immunocytochemistry were used to characterize differentiation markers with particular emphasis on insulin and C-peptide.

RESULTS

All 3 lineages expressed SSEA-4, a marker previously reported to be restricted to the ESC compartment. Phase contrast microscopy showed all three lineages recapitulated the treatment-dependent morphological changes of ESCs as well as the temporally restricted expression of nestin and vimentin during differentiation. After engineering, each isolate contained both C-peptide and insulin, a result also obtained following a much shorter protocol for ESCs.

CONCLUSIONS

Since C-peptide can only be derived from de novo synthesis and processing of pre-proinsulin mRNA and protein, we conclude that these results are the first demonstration that human umbilical cord blood-derived stem cells can be engineered to engage in de novo synthesis of insulin.

An overview of tissue engineering approaches for management of spinal cord injuries

Severe spinal cord injury (SCI) leads to devastating neurological deficits and disabilities, which necessitates spending a great deal of health budget for psychological and healthcare problems of these patients and their relatives. This justifies the cost of research into the new modalities for treatment of spinal cord injuries, even in developing countries. Apart from surgical management and nerve grafting, several other approaches have been adopted for management of this condition including pharmacologic and gene therapy, cell therapy, and use of different cell-free or cell-seeded bioscaffolds. In current paper, the recent developments for therapeutic delivery of stem and non-stem cells to the site of injury, and application of cell-free and cell-seeded natural and synthetic scaffolds have been reviewed.

Identification and analysis of in vitro cultured CD45-positive cells capable of multi-lineage differentiation

We report on a subset of cells that co-purify with CD45-positive/Lineage minus (CD45(pos)/Lin(minus)) hematopoietic cells that are capable of in vitro differentiation into multi-potential cells including cells with neuroectoderm properties. Although these cells are CD45 positive and have properties similar to CD45-negative mesenchymal progenitor cells (MPC) derived from bone marrow (BM), they are neither hematopoietic cells nor mesenchymal cells. These CD45(pos)/Lin(minus) cells can be expanded in vitro, express the stem cell genes Oct-4 and Nanog and can be induced to differentiate into endothelial cells, osteoblasts, muscle cells and neural cells at frequencies similar to those reported for bone marrow mesenchymal cells. Long-term culture of these cells followed by transplantation into NOD/SCID mice resulted in positive bone marrow stromal cell engraftment but not hematopoietic engraftment, suggesting that despite their CD45-positive status these cells do not have the same properties as hematopoietic stem cells. Clonal cell analysis determined that the culture period caused a broadening in the differentiation potential of the starting population.

Development and Validation of a 3D Clinostat for the Study of Cells during Microgravity Simulation

The clinostat was originally used to find out why plant roots appear to grow predominantly toward the center of the Earth. Over the last 2-3 decades, slow- and fast-rotating 2D and 3D clinostats have been used to assess cellular adaptation to this environment. A cell culture is placed in a spin module of the clinostat platform and its rotation is set empirically (2-3 rpm). The machine is then allowed to run for a specified period (hours to days) after which the cultures are removed and assayed for specific properties, such as cell growth, size and shape, distribution of receptors, integrity of the cytoskeleton or gene expression. A 3D clinostat was developed by the Microgravity Laboratory/IPCT-PUCRS group and validated by the Stem Cell Group of Kingston University London, which used 4 different types of human cancer cells and cord blood stem cells (CBSC). After rotation for 19h at 37degC, 5%CO2 humidified atmosphere, the 3D clinostat significantly improved proliferation potential of all tested cell populations when compared to static cultures. After only 5 days, high definition microscopic analysis revealed that all CBSC adhered and expanded onto the BDtrade 3D collagen composite scaffolds, and cross-developed into hepatocyte-like cells upon stimulation.

Cord blood in regenerative medicine: do we need immune suppression?

Cord blood is currently used as an alternative to bone marrow as a source of stem cells for hematopoietic reconstitution after ablation. It is also under intense preclinical investigation for a variety of indications ranging from stroke, to limb ischemia, to myocardial regeneration. A major drawback in the current use of cord blood is that substantial morbidity and mortality are associated with pre-transplant ablation of the recipient hematopoietic system. Here we raise the possibility that due to unique immunological properties of both the stem cell and non-stem cell components of cord blood, it may be possible to utilize allogeneic cells for regenerative applications without needing to fully compromise the recipient immune system. Issues raised will include: graft versus host potential, the immunogenicity of the cord blood graft, and the parallels between cord blood transplantation and fetal to maternal trafficking. The previous use of unmatched cord blood in absence of any immune ablation, as well as potential steps for widespread clinical implementation of allogeneic cord blood grafts will also be discussed.

Cerebrospinal fluid Flt3 ligand level in patients with amyotrophic lateral sclerosis

OBJECTIVES

The Flt3 ligand (FL) is a cytokine with a neurotrophic and antiapoptotic activity in the central nervous system that induces the survival of neurons. The aim of the study was to measure levels of FL in amyotrophic lateral sclerosis (ALS) patients.

MATERIALS AND METHODS

The study involved 23 ALS patients and 23 people in the control group. The measurement of FL in the cerebrospinal fluid (CSF) and serum was performed by the enzyme-linked immunosorbent method.

RESULTS

Results showed that CSF FL levels were significantly increased in ALS patients compared with the controls (P < 0.05) but the serum levels of this cytokine did not differ from the controls (P > 0.05). There was no significant correlation between CSF and serum FL levels and clinical parameters of ALS (P > 0.05). The difference in CSF/serum ratio of FL between ALS patients and controls was not statistically significant (P > 0.05).

CONCLUSION

An increase in CSF FL levels in ALS patients, observed in this study, could be a compensative response for neurodegeneration but may also reflect increased diffusion of this cytokine into the central nervous system caused by blood-CSF barrier dysfunction.

Early appearance of stem/progenitor cells with neural-like characteristics in human cord blood mononuclear fraction cultured in vitro

OBJECTIVE

The exposure of human umbilical cord blood mononuclear cells devoid of hematopoietic stem cells (HUCB-MNCsCD34-) to defined culture condition promotes their conversion into neural lineage. We have asked the question if observed fate change of HUCB-MNCsCD34- results from direct conversion of hematopoietic precursors into neural-like phenotypes due to expression of overlapping genetic program or, alternatively, these neural phenotypes arise from sequential differentiation of more primitive progenitors (embryonic-like cells) preexisting in HUCB-MNCsCD34- fraction.

MATERIALS AND METHODS

HUCB-MNCs negatively selected for CD34 antigens were cultured in vitro up to 14 days. Changes in stem/neural cell genes and proteins were successively evaluated during this period and after evoked neuronal differentiation of cells in the presence of RA or BDNF or cocultured with neonatal rat brain astrocytes.

RESULTS

Freshly isolated HUCB-MNCsCD34- expressed pluripotent cell markers: Oct3/4, Sox2, and Rex1 genes. During 24 hours of culture the frequency of Oct3/4 immunopositive cells increased markedly with parallel enlargement of "side population" and CD133+ cell appearance. Concomitantly, cultured cells start to form aggregates and express pro-neural genes, i.e., enhanced Sox2, OTX1, Nestin, GFAP, and NF-200. During the next days of culture immunoreactions for beta-tubulin III, MAP2, GFAP, S100beta, Doublecortin, and GalC were induced with reciprocal lowering of stem cell gene and protein markers. At this stage cells successively adhered to the bottom, dispersed, and decreased proliferation rate (Ki67 expression). Additional treatments with neuromorphogenes or coculturing with rat brain primary culture induced further differentiation of these neural precursors toward more advanced neuronal phenotypes.

CONCLUSIONS

HUCB-MNCs(CD34-) fraction contains embryonic-like stem/progenitor cells which increase rapidly but transiently in culture, then differentiate spontaneously after cell aggregate adhesion toward neural lineage. Neurally promoted cells from 10-14 DIV culture acquire three main neural-like phenotypes, i.e., neurons, astrocytes, and oligodendrocytes. In this respect they are promising candidates for experimental treatment of neuronal injury; however, the final proof for conversion of HUCB cells to neural cells can be obtained through transplantation experiments.

Neural stem-like cell line derived from a nonhematopoietic population of human umbilical cord blood

The ability of stem and progenitor cells to proliferate and differentiate into other lineages is widely viewed as a characteristic of stem cells. Previously, we have reported that cells from a CD34(-) (nonhematopoietic) adherent subpopulation of human cord blood can acquire a feature of multipotential neural progenitors in vitro. In the present study, using these cord blood-derived stem cells, we have established a clonal cell line termed HUCB-NSCs (human umbilical cord blood-neural stem cells) that expresses several neural antigens and has been grown in culture for more than 60 passages. During this time, HUCB-NSCs retained their growth rate, the ability to differentiate into neuronal-, astrocyte-, and oligodendrocyte-like cells and displayed a stable karyotype. DNA microarray analysis of HUCB-NSCs revealed enhanced expression of selected genes encoding putative stem and progenitor cell markers when compared to other mononuclear cells. dBcAMP-induced HUCBNSCs were further differentiated into more advanced neuronal cells. This is the first report of the establishment and characterization of a nontransformed HUCB-NSC line that can be grown continuously in a monolayer culture and induced to terminal differentiation. These cells should further our understanding of the regulatory mechanisms involved in NSC self-renewal and differentiation.

Umbilical cord blood-derived stem cells and brain repair

Human umbilical cord blood (HUCB) is now considered a valuable source for stem cell-based therapies. HUCB cells are enriched for stem cells that have the potential to initiate and maintain tissue repair. This potential is especially attractive in neural diseases for which no current cure is available. Furthermore, HUCB cells are easily available and less immunogenic compared to other sources for stem cell therapy such as bone marrow. Accordingly, the number of cord blood transplants has doubled in the last year alone, especially in the pediatric population. The therapeutic potential of HUCB cells may be attributed to inherent ability of stem cell populations to replace damaged tissues. Alternatively, various cell types within the graft may promote neural repair by delivering neural protection and secretion of neurotrophic factors. In this review, we evaluate the preclinical studies in which HUCB was applied for treatment of neurodegenerative diseases and for traumatic and ischemic brain damage. We discuss how transplantation of HUCB cells affects these disorders and we present recent clinical studies with promising outcome.

The application of umbilical cord blood cells in the treatment of diabetes mellitus

In recent years, human umbilical cord blood (HUCB) has emerged as an attractive tool for cell-based therapy. Although at present the clinical application of HUCB is limited to the fields of hematology and oncology, a rising number of studies show potential for further application in the treatment of non-hematopoietic diseases. HUCB, with its real abundance, simple collection procedure and no serious ethical dilemmas, represents a valuable alternative to the use of other stem cell sources. The aim of this article is to review the literature on HUCB and to assess its eventual usability in the treatment of diabetes mellitus. This review presents some recent reports concerning pancreatic endocrine stem cells and their identification, HUCB stem cells and their advantages and, finally, the potential for converting HUCB-derived stem cells into insulin-producing beta-cells.

Novel cell therapy approaches for brain repair

Numerous reports elucidate that tissue-specific stem cells are phenotypically plastic and their differentiation pathways are not strictly delineated. Although the identity of all the epigenetic factors which may trigger stem cells to make a lineage selection are still unknown, the plasticity of adult stem cells opens new approaches for their application in the treatment of various disorders. There is increasing researcher interest in hematopoietic stem cells for treatment of not only blood-related diseases but also various unrelated disorders including neurodegenerative diseases. Human umbilical cord blood (hUCB) cells, due to their primitive nature and ability to develop into nonhematopoietic cells of various tissue lineages, including neural cells, may be useful as an alternative cell source for cell-based therapies requiring either the replacement of individual cell types and/or substitution of missing substances. Here we focus on recent findings showing the robustness of adult stem cells derived from hUCB and their potential as a source of transplant cells for the treatment of diseased or injured brains and spinal cords. Depending upon the pathological microenvironment in which the hUCB cells are introduced, neuroprotective and/or trophic effects of these cells, from release of various growth or anti-inflammatory factors to moderation of immune-inflammatory effectors, may be more likely than neural replacement. These protective effects may prove essential to maintaining restored tissue integrity over the course of various diseases or injuries.

Production of stem cells with embryonic characteristics from human umbilical cord blood

When will embryonic stem cells reach the clinic? The answer is simple -- not soon! To produce large quantities of homogeneous tissue for transplantation, without feeder layers, and with the appropriate recipient's immunological phenotype, is a significant scientific hindrance, although adult stem (ADS) cells provide an alternative, more ethically acceptable, source. The annual global 100 million human birth rate proposes umbilical cord blood (UCB) as the largest untouched stem cell source, with advantages of naive immune status and relatively unshortened telomere length. Here, we report the world's first reproducible production of cells expressing embryonic stem cell markers, - cord-blood-derived embryonic-like stem cells (CBEs). UCB, after elective birth by Caesarean section, has been separated by sequential immunomagnetic removal of nucleate granulocytes, erythrocytes and haemopoietic myeloid/lymphoid progenitors. After 7 days of high density culture in microflasks, (10(5) cells/ml, IMDM, FCS 10%, thrombopoietin 10 ng/ml, flt3-ligand 50 ng/ml, c-kit ligand 20 ng/ml). CBE colonies formed adherent to the substrata; these were maintained for 6 weeks, then were subcultured and continued for a minimum 13 weeks. CBEs were positive for TRA-1-60, TRA-1-81, SSEA-4, SSEA-3 and Oct-4, but not SSEA-1, indicative of restriction in the human stem cell compartment. The CBEs were also microgravity--bioreactor cultured with hepatocyte growth medium (IMDM, FCS 10%, HGF 20 ng/ml, bFGF 10 ng/ml, EGF 10 ng/ml, c-kit ligand 10 ng/ml). After 4 weeks the cells were found to express characteristic hepatic markers, cytokeratin-18, alpha-foetoprotein and albumin. Thus, such CBEs are a viable human alternative from embryonic stem cells for stem cell research, without ethical constraint and with potential for clinical applications.

Human cord blood stem cells generate human cytokeratin 18-negative hepatocyte-like cells in injured mouse liver

Differentiation of adult bone marrow (BM) cells into nonhematopoietic cells is a rare phenomenon. Several reports, however, suggest that human umbilical cord blood (hUCB)-derived cells give rise to hepatocytes after transplantation into nonobese diabetic-severe combined immunodeficient (NOD-SCID) mice. Therefore, we analyzed the hepatic differentiation potential of hUCB cells and compared the frequency of newly formed hepatocyte-like cells in the livers of recipient NOD-SCID mice after transplantation of hUCB versus murine BM cells. Mononuclear cell preparations of hUCB cells or murine BM from enhanced green fluorescent protein transgenic or wild-type mice were transplanted into sublethally irradiated NOD-SCID mice. Liver regeneration was induced by carbon tetrachloride injury with and without subsequent hepatocyte growth factor treatment. By immunohistochemistry and reverse transcriptase-polymerase chain reaction, we detected clusters of hepatocyte-like cells in the livers of hUCB-transplanted mice. These cells expressed human albumin and Hep Par 1 but mouse CK18, suggesting the formation of chimeric hepatocyte-like cells. Native fluorescence microscopy and double immunofluorescence failed to detect single hepatocytes derived from transplanted enhanced green fluorescent protein-transgenic mouse BM. Fluorescent in situ hybridization rarely revealed donor-derived hepatocyte-like cells after cross-gender mouse BM transplantation. Thus, hUCB cells have differentiation capabilities different from murine BM cells after transplantation into NOD-SCID mice, demonstrating the importance of further testing before hUCB cells can be used therapeutically.

Human umbilical cord blood cells express neurotrophic factors

Freshly isolated or culture-expanded human umbilical cord blood mononuclear cells (CBMNCs) have been known to express neural phenotypes in vitro and to differentiate into neural cells and improve neurological function recovery after being administrated into rodent models of neurological diseases. However, the mechanism of action remains unclear. The present study observed that CBMNCs expressed higher level mRNAs of several neurotrophic factors than adult peripheral blood mononuclear cells (PBMCs). In addition, a significantly increase in the levels of brain-derived neurotrophic factor (BDNF) and neurotrophin-4/5 (NT4/5) was found in culture supernatants of CBMNCs compared to that of PBMNCs. These findings indicate that CBMNCs express several neurotrophic factors and suggest that the neurotrophic factors secreted by CBMNCs may be responsible for amelioration of central nervous system deficits in animal models after CBMNC administration.

Functional neural stem cells derived from adult bone marrow

Pluripotent hematopoietic cells from adult bone marrow may give rise not only to neurons, oligodendrocytes and astrocytes after transplantation into newborn brains, but also to neural stem cells (NSC). These NSC localize to both the ventricular epithelium and subventricular zone, persist in the transplanted brain, and may generate neurospheres 1 month after transplant, which after in vitro expansion differentiate into the different neural lineages. Furthermore, the bone marrow-derived NSC differentiate in vivo into functional oligodendrocytes and neurons following demyelinating lesions, thus, demonstrating the ability of adult bone marrow progenitors to generate self-renewing, functional neural stem cells, validating this approach as an alternative source of long-lasting neural stem cells with therapeutic implications in neurodegenerative diseases.

Neural stem cells and cell replacement therapy: making the right cells

The past few years have seen major advances in the field of NSC (neural stem cell) research with increasing emphasis towards its application in cell-replacement therapy for neurological disorders. However, the clinical application of NSCs will remain largely unfeasible until a comprehensive understanding of the cellular and molecular mechanisms of NSC fate specification is achieved. With this understanding will come an increased possibility to exploit the potential of stem cells in order to manufacture transplantable NSCs able to provide a safe and effective therapy for previously untreatable neurological disorders. Since the pathology of each of these disorders is determined by the loss or damage of a specific neural cell population, it may be necessary to generate a range of NSCs able to replace specific neurons or glia rather than generating a generic NSC population. Currently, a diverse range of strategies is being investigated with this goal in mind. In this review, we focus on the relationship between NSC specification and differentiation and discuss how this information may be used to direct NSCs towards a particular fate.

Thrombopoietin, flt3-ligand and c-kit-ligand modulate HOX gene expression in expanding cord blood CD133 cells

Haemopoietic stem/progenitor cell (HSPC) development is regulated by extrinsic and intrinsic stimuli. Extrinsic modulators include growth factors and cell adhesion molecules, whereas intrinsic regulation is achieved with many transcription factor families, of which the HOX gene products are known to be important in haemopoiesis. Umbilical cord blood CD133+ HSPC proliferation potential was tested in liquid culture with 'TPOFLK' (thrombopoietin, flt-3 ligand and c-kit ligand, promoting HSPC survival and self-renewal), in comparison to 'K36EG' (c-kit-ligand, interleukins-3 and -6, erythropoietin and granulocyte colony-stimulating factor, inducing haemopoietic differentiation). TPOFLK induced a higher CD133+ HSPC proliferation (up to 60-fold more, at week 8) and maintained a higher frequency of the primitive colony-forming cells than K36EG. Quantitative polymerase chain reaction analysis revealed opposite expression patterns for specific HOX genes in expanding cord blood CD133+ HSPC. After 8 weeks in liquid culture, TPOFLK increased the expression of HOX B3, B4 and A9 (associated with uncommitted HSPC) and reduced the expression of HOX B8 and A10 (expressed in committed myeloid cells) when compared to K36EG. These results suggest that TPOFLK induces CD133+ HSPC proliferation, self-renewal and maintenance, up-regulation of HOX B3, B4 and A9 and down-regulation of HOX B8 and A10 gene expression.