Suppression of cellular immunity by cord blood-derived unrestricted somatic stem cells is cytokine-dependent

Tracking of GFP-labeled unrestricted somatic stem cells transplanted in the sepsis mouse model

Cell-based therapy provides a promising approach for the treatment of sepsis and related disorders. Fate determination of transplanted cells is the most essential issue for cell therapist. Optical imaging is the reliable, time and cost-effective system for cell tracking. The present study was aimed to apply an optical imaging system for monitoring of GFP-labeled unrestricted somatic stem cells in the sepsis animal model. In vivo imaging showed the most accumulation of intravenously injected cells into the lungs and liver of septic mice. Thereafter, the imaging data were more approved by flow cytometry and immunohistochemistry staining. Cellular localization in septic lungs and liver that observed by optical imaging technique may offer beneficial evidence for designing of sepsis clinical trials.

The effects of culture conditions on the functionality of efficiently obtained mesenchymal stromal cells from human cord blood

BACKGROUND AIMS

Cord blood (CB) is an attractive source of mesenchymal stromal cells (MSCs) because of its abundant availability and ease of collection. However, the success rate of generating CB-MSCs is low. In this study, our aim was to demonstrate the efficiency of our previously described method to obtain MSCs from CB and further characterize them and to study the effects of different culture conditions on MSCs.

METHODS

CB-MSC cultures were established in low oxygen (3%) conditions on fibronectin in 10% fetal bovine serum containing culture medium supplemented with combinations of growth factors. Cells were characterized for their adipogenic, osteogenic and chondrogenic differentiation capacity; phenotype; and HOX gene expression profile. The functionality of the cells cultured in different media was tested in vitro with angiogenesis and T-cell proliferation assays.

RESULTS

We demonstrate 87% efficacy in generating MSCs from CB. The established cells had typical MSC characteristics with reduced adipogenic differentiation potential and a unique HOX gene fingerprint. Growth factor-rich medium and a 3% oxygen condition enhanced cell proliferation; however, the growth factor-rich medium had a negative effect on the expression of CD90. Dexamethasone-containing medium improved the capacity of the cells to suppress T-cell proliferation, whereas the cells grown without dexamethasone were more able to support angiogenesis.

CONCLUSIONS

Our results demonstrate that the composition of expansion medium is critical for the functionality of MSCs and should always be appropriately defined for each purpose.

Characterization of Regenerative Phenotype of Unrestricted Somatic Stem Cells (USSC) from Human Umbilical Cord Blood (hUCB) by Functional Secretome Analysis

Stem cell transplantation is a promising therapeutic strategy to enhance axonal regeneration after spinal cord injury. Unrestricted somatic stem cells (USSC) isolated from human umbilical cord blood is an attractive stem cell population available at GMP grade without any ethical concerns. It has been shown that USSC transplantation into acute injured rat spinal cords leads to axonal regrowth and significant locomotor recovery, yet lacking cell replacement. Instead, USSC secrete trophic factors enhancing neurite growth of primary cortical neurons in vitro. Here, we applied a functional secretome approach characterizing proteins secreted by USSC for the first time and validated candidate neurite growth promoting factors using primary cortical neurons in vitro. By mass spectrometric analysis and exhaustive bioinformatic interrogation we identified 1156 proteins representing the secretome of USSC. Using Gene Ontology we revealed that USSC secretome contains proteins involved in a number of relevant biological processes of nerve regeneration such as cell adhesion, cell motion, blood vessel formation, cytoskeleton organization and extracellular matrix organization. We found for instance that 31 well-known neurite growth promoting factors like, e.g. neuronal growth regulator 1, NDNF, SPARC, and PEDF span the whole abundance range of USSC secretome. By the means of primary cortical neurons in vitro assays we verified SPARC and PEDF as significantly involved in USSC mediated neurite growth and therewith underline their role in improved locomotor recovery after transplantation. From our data we are convinced that USSC are a valuable tool in regenerative medicine as USSC's secretome contains a comprehensive network of trophic factors supporting nerve regeneration not only by a single process but also maintained its regenerative phenotype by a multitude of relevant biological processes.

Human Cord Blood-Derived Unrestricted Somatic Stem Cells Promote Wound Healing and have Therapeutic Potential for Patients with Recessive Dystrophic Epidermolysis Bullosa

Human umbilical cord blood (CB)-derived unrestricted somatic stem cells (USSCs) have previously been demonstrated to have a broad differentiation potential and regenerative beneficial effects when administered in animal models of multiple degenerative diseases. Here we demonstrated that USSCs could be induced to express genes that hallmark keratinocyte differentiation. We also demonstrated that USSCs express type VII collagen (C7), a protein that is absent or defective in patients with an inherited skin disease, recessive dystrophic epidermolysis bullosa (RDEB). In mice with full-thickness excisional wounds, a single intradermal injection of USSCs at a 1-cm distance to the wound edge resulted in significantly accelerated wound healing. USSC-treated wounds displayed a higher density of CD31+ cells, and the wounds healed with a significant increase in skin appendages. These beneficial effects were demonstrated without apparent differentiation of the injected USSCs into keratinocytes or endothelial cells. In vivo bioluminescent imaging (BLI) revealed specific migration of USSCs modified with a luciferase reporter gene, from a distant intradermal injection site to the wound, as well as following systemic injection of USSCs. These data suggest that CB-derived USSCs could significantly contribute to wound repair and be potentially used in cell therapy for patients with RDEB.

A comparison of the efficacy of transplantation of bone marrow-derived mesenchymal stem cells and unrestricted somatic stem cells on outcome after acute myocardial infarction

Introduction

A number of questions remain unanswered in the field of cell therapy for acute myocardial infarction, including what is the optimal cell type, and can therapeutic efficacy be enhanced by conditioning regimens. In this study, we sought to address these questions by directly comparing the effect of bone marrow-derived mesenchymal stem cells and unrestricted somatic stem cells delivered 24 hours post-myocardial infarction and by determining if the therapeutic efficacy of unrestricted somatic stem cells could be enhanced by exposing the cells to guiding factors before cell transplantation.

Methods

Unrestricted somatic stem cells were guided by exposure to 50 ng/mL basic fibroblast growth factor, 20 ng/mL hepatocyte growth factor and 20 ng/mL bone morphogenetic protein-2 for 24 hours. Using a Sprague-Dawley rat model of acute myocardial infarction, we transplanted cells by intramyocardial injection 24 hours post-myocardial infarction. Cardiac function was serially measured using echocardiography, and histological analyses of infarct morphology, angiogenesis and apoptosis were obtained. Transcriptomic and proteomic changes were assessed using microarray and real-time quantitative PCR.

Results

When assessed 28 days after the myocardial infarction, the delivery of mesenchymal stem cells 24 hours post-myocardial infarction did not improve ejection fraction (P = 0.19), and did not prevent the decline in ejection fraction observed in the absence of cell therapy (P = 0.17). The administration of unrestricted somatic stem cells also did not improve ejection fraction (P = 0.11), but did prevent a further decline in ejection fraction (P = 0.001). Delivery of guided unrestricted somatic stem cells significantly improved ejection fraction (P = 0.03). Guided unrestricted somatic stem cells restored function to a greater extent than mesenchymal stem cells (P = 0.03). The infarct area (P = 0.2), apoptosis (P = 0.07) and angiogenesis (P = 0.09) did not differ between groups. Microarray analysis revealed that, following pre-implantation guiding, the gene groupings of mitosis, signalling and angiogenesis were highly overrepresented, mediators of apoptosis were overrepresented, and cardiomyocyte-associated genes were not differentially expressed.

Conclusions

These results suggest that guided unrestricted somatic stem cells have a moderate capacity to repair cardiac damage and that they are more effective than mesenchymal stem cells in restoring cardiac function after a myocardial infarction. The mechanism of the benefit was not fully elucidated in this study, but these observations may be mediated by favorable dysregulation of angiogenic and apoptotic gene groupings.

Significant clinical, neuropathological and behavioural recovery from acute spinal cord trauma by transplantation of a well-defined somatic stem cell from human umbilical cord blood

Stem cell therapy is a potential treatment for spinal cord injury and different stem cell types have been grafted into animal models and humans suffering from spinal trauma. Due to inconsistent results, it is still an important and clinically relevant question which stem cell type will prove to be therapeutically effective. Thus far, stem cells of human sources grafted into spinal cord mostly included barely defined heterogeneous mesenchymal stem cell populations derived from bone marrow or umbilical cord blood. Here, we have transplanted a well-defined unrestricted somatic stem cell isolated from human umbilical cord blood into an acute traumatic spinal cord injury of adult immune suppressed rat. Grafting of unrestricted somatic stem cells into the vicinity of a dorsal hemisection injury at thoracic level eight resulted in hepatocyte growth factor-directed migration and accumulation within the lesion area, reduction in lesion size and augmented tissue sparing, enhanced axon regrowth and significant functional locomotor improvement as revealed by three behavioural tasks (open field Basso-Beattie-Bresnahan locomotor score, horizontal ladder walking test and CatWalk gait analysis). To accomplish the beneficial effects, neither neural differentiation nor long-lasting persistence of the grafted human stem cells appears to be required. The secretion of neurite outgrowth-promoting factors in vitro further suggests a paracrine function of unrestricted somatic stem cells in spinal cord injury. Given the highly supportive functional characteristics in spinal cord injury, production in virtually unlimited quantities at GMP grade and lack of ethical concerns, unrestricted somatic stem cells appear to be a highly suitable human stem cell source for clinical application in central nervous system injuries.

DLK-1 as a marker to distinguish unrestricted somatic stem cells and mesenchymal stromal cells in cord blood

In addition to hematopoietic stem cells, cord blood (CB) also contains different nonhematopoietic CD45-, CD34- adherent cell populations: cord blood mesenchymal stromal cells (CB MSC) that behave almost like MSC from bone marrow (BM MSC) and unrestricted somatic stem cells (USSC) that differentiate into cells of all 3 germ layers. Distinguishing between these populations is difficult due to overlapping features such as the immunophenotype or the osteogenic and chondrogenic differentiation pathway. Functional differences in the differentiation potential suggest different developmental stages or different cell populations. Here we demonstrate that the expression of genes and the differentiation toward the adipogenic lineage can discriminate between these 2 populations. USSC, including clonal-derived cells lacking adipogenic differentiation, strongly expressed δ-like 1/preadipocyte factor 1 (DLK-1/PREF1) correlating with high proliferative potential, while CB MSC were characterized by a strong differentiation toward adipocytes correlating with a weak or negative DLK-1/PREF1 expression. Constitutive overexpression of DLK-1/PREF1 in CB MSC resulted in a reduced adipogenic differentiation, whereas silencing of DLK-1 in USSC resulted in adipogenic differentiation.

Cord blood transplantation and stem cell regenerative potential

The past 20 years of experience with umbilical cord blood transplantation have demonstrated that cord blood is effective in the treatment of a spectrum of diseases, including hematological malignancies, bone marrow failure, hemoglobinopathies, and inborn errors of metabolism. Cord blood can be obtained with ease and then safely cryopreserved for either public or private use without loss of viability. As compared to other unrelated donor cell sources, cord blood transplantation allows for greater human leukocyte antigen disparity without a corresponding increase in graft-vs.-host disease. Moreover, cord blood has a lower risk of transmitting infections by latent viruses and is less likely to carry somatic mutations than other adult cells. Recently, multiple populations of stem cells with primitive stem cell properties have been identified from cord blood. Meanwhile, there is an increasing interest in applying cord blood mononuclear cells or enriched stem cell populations to regenerative therapies. Accumulating evidence has suggested functional improvements after cord blood transplantation in various animal models for treatments of cardiac infarction, diabetes, neurological diseases, etc. In this review, we will summarize the most recent updates on clinical applications of cord blood transplantation and the promises and limitations of cell-based therapies for tissue repair and regeneration.

Improvement of the cell-loading efficiency of biomaterials by inoculation with stem cell-based microspheres, in osteogenesis

In critical-size bone defects, autologous or allogenic cells are required in addition to compatible biomaterials for the successful defect healing. State of the art inoculation methods of biomaterials are based on the application of cell suspensions to the biomaterial. However, only less amounts of cells can be applied and sufficient adhesion to the material is required. Therefore, it was investigated whether the advantages of stem cell-based microspheres and insoluble collagenous bone matrix (ICBM) scaffolds can be combined which can lead to an advancement in cell seeding on biomaterials. Microspheres were produced from unrestricted somatic stem cells from human umbilical cord blood and were mounted on ICBM scaffolds. Following the incubation with osteogenic or control medium, the constructs were analyzed histologically after 3, 7, 14, and 28 days. Alizarin Red S and von Kossa staining revealed microsphere mineralization after 3 days in osteogenic and after 14 days in control medium. Meanwhile, a time-dependent increase in tissue, growing out of the microspheres, was detected. Our results provide evidence that microsphere-ICBM constructs are promising candidates for approaches of bone regeneration. They allow the transfer of substantially high numbers of cells in partially mineralized constructs.

Mesenchymal stromal cells from human perinatal tissues: From biology to cell therapy

Cell-based regenerative medicine is of growing interest in biomedical research. The role of stem cells in this context is under intense scrutiny and may help to define principles of organ regeneration and develop innovative therapeutics for organ failure. Utilizing stem and progenitor cells for organ replacement has been conducted for many years when performing hematopoietic stem cell transplantation. Since the first successful transplantation of umbilical cord blood to treat hematological malignancies, non-hematopoietic stem and progenitor cell populations have recently been identified within umbilical cord blood and other perinatal and fetal tissues. A cell population entitled mesenchymal stromal cells (MSCs) emerged as one of the most intensely studied as it subsumes a variety of capacities: MSCs can differentiate into various subtypes of the mesodermal lineage, they secrete a large array of trophic factors suitable of recruiting endogenous repair processes and they are immunomodulatory.Focusing on perinatal tissues to isolate MSCs, we will discuss some of the challenges associated with these cell types concentrating on concepts of isolation and expansion, the comparison with cells derived from other tissue sources, regarding phenotype and differentiation capacity and finally their therapeutic potential.

Cord blood mesenchymal stem cells propel human dendritic cells to an intermediate maturation state and boost interleukin-12 production by mature dendritic cells

Pathogen-derived entities force the tissue-resident dendritic cells (DCs) towards a mature state, followed by migration to the draining lymph node to present antigens to T cells. Bone marrow mesenchymal stem cells (MSCs) modulate the differentiation, maturation and function of DCs. In umbilical cord blood an immature MSC population was identified. Remarkably, these immature stem cells modulated DCs in a different way. Marker expression was unchanged during the differentiation of monocytes towards immature DCs (iDCs) when cocultured with cord blood MSC [unrestricted somatic stem cells (USSCs)]. The maturation to mature DCs (mDCs) was enhanced when DCs were co-cultured with USSC, as evidenced by the up-regulation of costimulatory molecules. Endocytosis of dextran by iDCs was hampered in the presence of USSCs, which is indicative for the maturation of iDCs. Despite this maturation, the migration of iDCs cocultured with USSCs appeared to be identical to iDCs cultured alone. However, USSCs increased the migration of mDCs towards CCL21 and boosted interleukin-12 production. So, USSCs mature iDCs, thereby redirecting the antigen-uptake phenotype towards a mature phenotype. Furthermore, DC maturation by lipopolysaccharide (LPS) or USSCs reflects two distinct pathways because migration was unaffected when iDCs were matured by coculture with USSCs, while it was strongly enhanced in the presence of LPS. DCs are able to discriminate the different MSC subtypes, resulting in diverse differentiation programmes.

Future of cord blood for non-oncology uses

For the last 5 years cord blood (CB) has been under intense experimental investigation in in vitro differentiation models and in preclinical animal models ranging from bone to muscle regeneration, cardiovascular diseases including myocardial and peripheral arterial disease, stroke and Parkinson's disease. On the basis of its biological advantages, CB can be an ideal source for tissue regeneration. However, in the hype of the so-called 'plasticity', many cell types have been characterized either on cell surface Ag expression alone or by RNA expression only, and without detailed characterization of genetic pathways; frequently, cells are defined without analysis of cellular function in vitro and in vivo, and the definition of the lineage of origin and cells have not been defined in preclinical studies. Here, we explore not only the most consistent data with regard to differentiation of CB cells in vitro and in vivo, but also show technical limitations, such as why in contrast to cell populations isolated from fresh CB, cryopreserved CB is not the ideal source for tissue regeneration. By taking advantage of numerous CB units discarded due to lack of sufficient hematopoietic cells for clinical transplantation, new concepts to produce off-the-shelf products are presented as well.