Optimization of primary culture condition for mesenchymal stem cells derived from umbilical cord blood with factorial design

Optimizing the generation of mature bone marrow-derived dendritic cells in vitro: a factorial study design

BACKGROUND

Factorial design is a simple, yet elegant method to investigate the effect of multiple factors and their interaction on a specific response simultaneously. Hence, this type of study design reaches the best optimization conditions of a process. Although the interaction between the variables is widely prevalent in cell culture procedures, factorial design per se is infrequently utilized in improving cell culture output. Therefore, we aim to optimize the experimental conditions for generating mature bone marrow-derived dendritic cells (BMDCs). Two different variables were investigated, including the concentrations of the inducing factors and the starting density of the bone marrow mononuclear cells. In the current study, we utilized the design of experiments (DoE), a statistical approach, to systematically assess the impact of factors with varying levels on cell culture outcomes. Herein, we apply a two-factor, two-level (22) factorial experiment resulting in four conditions that are run in triplicate. The two variables investigated here are cytokines combinations with two levels, granulocyte-macrophage colony-stimulating factor (GM-CSF) alone or with interleukin-4 (IL4). The other parameter is cell density with two different concentrations, 2 × 106 and 4 × 106 cells/mL. Then, we measured cell viability using the trypan blue exclusion method, and a flow cytometer was used to detect the BMDCs expressing the markers FITC-CD80, CD86, CD83, and CD14. BMDC marker expression levels were calculated using arbitrary units (AU) of the mean fluorescence intensity (MFI).

RESULTS

The current study showed that the highest total viable cells and cells yield obtained were in cell group seeded at 2 × 106 cells/mL and treated with GM-CSF and IL-4. Importantly, the expression of the co-stimulatory molecules CD83 and CD80/CD86 were statistically significant for cell density of 2 × 106 cells/mL (P < 0.01, two-way ANOVA). Bone marrow mononuclear cells seeded at 4 × 106 in the presence of the cytokine mix less efficiently differentiated and matured into BMDCs. Statistical analysis via two-way ANOVA revealed an interaction between cell density and cytokine combinations.

CONCLUSION

The analysis of this study indicates a substantial interaction between cytokines combinations and cell densities on BMDC maturation. However, higher cell density is not associated with optimizing DC maturation. Notably, applying DoE in bioprocess designs increases experimental efficacy and reliability while minimizing experiments, time, and process costs.

Clever Experimental Designs: Shortcuts for Better iPSC Differentiation

For practical use of pluripotent stem cells (PSCs) for disease modelling, drug screening, and regenerative medicine, the cell differentiation process needs to be properly refined to generate end products with consistent and high quality. To construct and optimize a robust cell-induction process, a myriad of cell culture conditions should be considered. In contrast to inefficient brute-force screening, statistical design of experiments (DOE) approaches, such as factorial design, orthogonal array design, response surface methodology (RSM), definitive screening design (DSD), and mixture design, enable efficient and strategic screening of conditions in smaller experimental runs through multifactorial screening and/or quantitative modeling. Although DOE has become routinely utilized in the bioengineering and pharmaceutical fields, the imminent need of more detailed cell-lineage specification, complex organoid construction, and a stable supply of qualified cell-derived material requires expedition of DOE utilization in stem cell bioprocessing. This review summarizes DOE-based cell culture optimizations of PSCs, mesenchymal stem cells (MSCs), hematopoietic stem cells (HSCs), and Chinese hamster ovary (CHO) cells, which guide effective research and development of PSC-derived materials for academic and industrial applications.

Prospects for the therapeutic development of umbilical cord blood-derived mesenchymal stem cells

Umbilical cord blood (UCB) is a primitive and abundant source of mesenchymal stem cells (MSCs). UCB-derived MSCs have a broad and efficient therapeutic capacity to treat various diseases and disorders. Despite the high latent self-renewal and differentiation capacity of these cells, the safety, efficacy, and yield of MSCs expanded for ex vivo clinical applications remains a concern. However, immunomodulatory effects have emerged in various disease models, exhibiting specific mechanisms of action, such as cell migration and homing, angiogenesis, anti-apoptosis, proliferation, anti-cancer, anti-fibrosis, anti-inflammation and tissue regeneration. Herein, we review the current literature pertaining to the UCB-derived MSC application as potential treatment strategies, and discuss the concerns regarding the safety and mass production issues in future applications.

A simple, efficient and economical method for isolating and culturing human umbilical cord blood‑derived mesenchymal stromal cells

Mesenchymal stromal cells (MSCs) hold broad therapeutic potential in various diseases, however, it is difficult to produce sufficient numbers of MSCs for clinical application, therefore, improved culture systems are required. The present study aimed to develop a novel method for isolating and culturing human umbilical cord blood‑derived mesenchymal stromal cells (hUCB‑MSCs). A sequential culture method was developed that uses two types of culture media to optimize the isolation and culture of hUCB‑MSCs. First, DMEM supplemented with mesenchymal stem cell growth supplement was used to improve the colony formation and primary culture success rates of hUCB‑MSCs. Then, after removing the heterogeneous cell population, ordinary DMEM was used from the fourth passage. This method obtained hUCB‑MSCs with high culture efficiency and at a greatly reduced cost. The optimal culture conditions were determined and the hUCB‑MSCs were phenotypically characterized after passaging. Taken together, this simple, efficient and economical method can produce a large number of high‑quality hUCB‑MSCs in <1 month, therefore facilitating the future clinical applications of hUCB‑MSCs.

Current Status of Canine Umbilical Cord Blood-Derived Mesenchymal Stem Cells in Veterinary Medicine

Stem cell therapy has prompted the expansion of veterinary medicine both experimentally and clinically, with the potential to contribute to contemporary treatment strategies for various diseases and conditions for which limited or no therapeutic options are presently available. Although the application of various types of stem cells, such as bone marrow-derived mesenchymal stem cells (BM-MSCs), adipose tissue-derived mesenchymal stem cells (AT-MSCs), and umbilical cord blood-derived mesenchymal stem cells (UCB-MSCs), has promising potential to improve the health of different species, it is crucial that the benefits and drawbacks are completely evaluated before use. Umbilical cord blood (UCB) is a rich source of stem cells; nonetheless, isolation of mesenchymal stem cells (MSCs) from UCB presents technical challenges. Although MSCs have been isolated from UCB of diverse species such as human, equine, sheep, goat, and canine, there are inherent limitations of using UCB from these species for the expansion of MSCs. In this review, we investigated canine UCB (cUCB) and compared it with UCB from other species by reviewing recent articles published from February 2003 to June 2017 to gain an understanding of the limitations of cUCB in the acquisition of MSCs and to determine other suitable sources for the isolation of MSCs from canine. Our review indicates that cUCB is not an ideal source of MSCs because of insufficient volume and ethical issues. However, canine reproductive organs discarded during neutering may help broaden our understanding of effective isolation of MSCs. We recommend exploring canine reproductive and adipose tissue rather than UCB to fulfill the current need in veterinary medicine for the well-designed and ethically approved source of MSCs.

The treatment of spinal cord injury in rats using bone marrow-derived neural-like cells induced by cerebrospinal fluid

This study aimed to evaluate the effect of bone mesenchymal stem cells (BMSCs) and BMSC neural-like cells (BMSC-Ns) on the spinal cord injury (SCI) in the rat model of SCI. BMSC-Ns were prepared from the third passage of BMSCs by induction of healthy cerebrospinal fluid (CSF) of an adult human. The SCI rat model was established through a surgical procedure, and after 7 days the rats were randomly divided into 3 (A, B and C) groups. Groups A (BMSC-Ns) and B (BMSCs) were treated with 1 × 10⁶/20 μl cells, while group C (saline) was treated with saline, all via intracerebroventricular injection. After transplantation, the BBB score of group A was significantly higher than that of group B, which in turn was significantly higher than that of group C (P < .05). The levels of Bdnf, Ngf, Ntf3 were statistically significantly higher in group A than those in groups B and C (P < .05). The levels of 5-HT, NA, Ach, DA, GABA in group A were significantly higher than those in groups B and C, whereas the level of Glu was significantly lower in group A than that in groups B and C (P < .05). The histopathological data showed remarkably less necrosis of the spinal cord in group A, compared to that in groups B and C. Transplanting BMSC-Ns or BMSCs into the lateral ventricles improved the neurological function of rats with SCI. Moreover, BMSC-Ns were significantly more effective than BMSCs, which provides a possible approach for the treatment of SCI.

Perinatal Brain Injury As a Consequence of Preterm Birth and Intrauterine Inflammation: Designing Targeted Stem Cell Therapies

Chorioamnionitis is a major cause of preterm birth and brain injury. Bacterial invasion of the chorion and amnion, and/or the placenta, can lead to a fetal inflammatory response, which in turn has significant adverse consequences for the developing fetal brain. Accordingly, there is a strong causal link between chorioamnionitis, preterm brain injury and the pathogenesis of severe postnatal neurological deficits and cerebral palsy. Currently there are no treatments to protect or repair against brain injury in preterm infants born after pregnancy compromised by intrauterine infection. This review describes the injurious cascade of events in the preterm brain in response to a severe fetal inflammatory event. We will highlight specific periods of increased vulnerability, and the potential effects of therapeutic intervention with cell-based therapies. Many clinical trials are underway to investigate the efficacy of stem cells to treat patients with cerebral palsy. Stem cells, obtained from umbilical cord tissue and cord blood, normally discarded after birth, are emerging as a safe and potentially effective therapy. It is not yet known, however, which stem cell type(s) are the most efficacious for administration to preterm infants to treat brain injury-mediated inflammation. Individual stem cell populations found in cord blood and tissue, such as mesenchymal stem cells (MSCs) and endothelial progenitor cells (EPCs), have a number of potential benefits that may specifically target preterm inflammatory-induced brain injury. MSCs have strong immunomodulatory potential, protecting against global and local neuroinflammatory cascades triggered during infection to the fetus. EPCs have angiogenic and vascular reparative qualities that make them ideal for neurovascular repair. A combined therapy using both MSCs and EPCs to target inflammation and promote angiogenesis for re-establishment of vital vessel networks is a treatment concept that warrants further investigation.

[Development of blood-brain barrier under the modulation of HIF activity in astroglialand neuronal cells in vitro]

Barriergenesis is the process of maturation of the primary vascular network of the brain responsible for the establishment of the blood-brain barrier. It represents a combination of factors that, on the one hand, contribute to the process of migration and tubulogenesis of endothelial cells (angiogenesis), on the other hand, contribute to the formation of new connections between endothelial cells and other elements of the neurovascular unit. Astrocytes play a key role in barriergenesis, however, mechanisms of their action are still poorly examined. We have studied the effects of HIF-1 modulators acting on the cells of non-endothelial origin (neurons and astrocytes) on the development of the blood-brain barrier in vitro. Application of FM19G11 regulating expression of HIF-1 activity and GSI-1 suppressing gamma-secretase and/or proteasomal activity resulted in the elevated expression of thrombospondins and matrix metalloproteinases in the developing blood-brain barrier. However, it caused the opposite effect on VEGF expression thus promoting barrier maturation in vitro.

High content analysis platform for optimization of lipid mediated CRISPR-Cas9 delivery strategies in human cells

Non-viral gene-editing of human cells using the CRISPR-Cas9 system requires optimized delivery of multiple components. Both the Cas9 endonuclease and a single guide RNA, that defines the genomic target, need to be present and co-localized within the nucleus for efficient gene-editing to occur. This work describes a new high-throughput screening platform for the optimization of CRISPR-Cas9 delivery strategies. By exploiting high content image analysis and microcontact printed plates, multi-parametric gene-editing outcome data from hundreds to thousands of isolated cell populations can be screened simultaneously. Employing this platform, we systematically screened four commercially available cationic lipid transfection materials with a range of RNAs encoding the CRISPR-Cas9 system. Analysis of Cas9 expression and editing of a fluorescent mCherry reporter transgene within human embryonic kidney cells was monitored over several days after transfection. Design of experiments analysis enabled rigorous evaluation of delivery materials and RNA concentration conditions. The results of this analysis indicated that the concentration and identity of transfection material have significantly greater effect on gene-editing than ratio or total amount of RNA. Cell subpopulation analysis on microcontact printed plates, further revealed that low cell number and high Cas9 expression, 24h after CRISPR-Cas9 delivery, were strong predictors of gene-editing outcomes. These results suggest design principles for the development of materials and transfection strategies with lipid-based materials. This platform could be applied to rapidly optimize materials for gene-editing in a variety of cell/tissue types in order to advance genomic medicine, regenerative biology and drug discovery.

STATEMENT OF SIGNIFICANCE

CRISPR-Cas9 is a new gene-editing technology for "genome surgery" that is anticipated to treat genetic diseases. This technology uses multiple components of the Cas9 system to cut out disease-causing mutations in the human genome and precisely suture in therapeutic sequences. Biomaterials based delivery strategies could help transition these technologies to the clinic. The design space for materials based delivery strategies is vast and optimization is essential to ensuring the safety and efficacy of these treatments. Therefore, new methods are required to rapidly and systematically screen gene-editing efficacy in human cells. This work utilizes an innovative platform to generate and screen many formulations of synthetic biomaterials and components of the CRISPR-Cas9 system in parallel. On this platform, we watch genome surgery in action using high content image analysis. These capabilities enabled us to identify formulation parameters for Cas9-material complexes that can optimize gene-editing in a specific human cell type.

Mesenchymal stromal cells derived from human umbilical cord tissues: primitive cells with potential for clinical and tissue engineering applications

Mesenchymal stem or stromal cells (MSCs) have a high potential for cell-based therapies as well as for tissue engineering applications. Since Friedenstein first isolated stem or precursor cells from the human bone marrow (BM) stroma that were capable of osteogenesis, BM is currently the most common source for MSCs. However, BM presents several disadvantages, namely low frequency of MSCs, high donor-dependent variations in quality, and painful invasive intervention. Thus, tremendous research efforts have been observed during recent years to find alternative sources for MSCs.In this context, the human umbilical cord (UC) has gained more and more attention. Since the UC is discarded after birth, the cells are easily accessible without ethical concerns. This postnatal organ was found to be rich in primitive stromal cells showing typical characteristics of bone-marrow MSCs (BMSCs), e.g., they grow as plastic-adherent cells with a fibroblastic morphology, express a set of typical surface markers, and can be directly differentiated at least along mesodermal lineages. Compared to BM, the UC tissue bears a higher frequency of stromal cells with a higher in vitro expansion potential. Furthermore, immune-privileged and immune-modulatory properties are reported for UC-derived cells, which open highly interesting perspectives for clinical applications.

Functional and differential proteomic analyses to identify platelet derived factors affecting ex vivo expansion of mesenchymal stromal cells

Background

Multilineage differentiation, immunomodulation and secretion of trophic factors render mesenchymal stromal cells (MSC) highly attractive for clinical application. Human platelet derivatives such as pooled human platelet lysate (pHPL) and thrombin-activated platelet releasate in plasma (tPRP) have been introduced as alternatives to fetal bovine serum (FBS) to achieve GMP-compliance. However, whereas both pHPL and tPRP support similar proliferation kinetics of lipoaspirate-derived MSC (LA-MSC), only pHPL significantly accelerates bone marrow-derived MSC (BM-MSC) expansion. To identify functionally bioactive factors affecting ex vivo MSC expansion, a differential proteomic approach was performed and identified candidate proteins were evaluated within a bioassay.

Results

Two dimensional difference gel electrophoresis (2D-DIGE), MALDI-TOF analyses and complementary Western blotting revealed 20 differential protein species. 14 candidate proteins occured at higher concentrations in pHPL compared to tPRP and 6 at higher concentrations in tPRP. The candidate proteins fibrinogen and apolipoprotein A1 differentially affected LA- and BM-MSC proliferation.

In a second set of experiments, reference cytokines known to foster proliferation in FBS were tested for their effects in the human supplements. Interestingly although these cytokines promoted proliferation in FBS, they failed to do so when added to the humanized system.

Conclusions

The differential proteomic approach identified novel platelet derived factors differentially acting on human MSC proliferation. Complementary testing of reference cytokines revealed a lack of stimulation in the human supplements compared to FBS. The data describe a new coherent approach to combine proteomic technologies with functional testing to develop novel, humanized, GMP-compliant conditions for MSC expansion.

Comparison of different methods for the isolation of mesenchymal stem cells from umbilical cord matrix: proliferation and multilineage differentiation as compared to mesenchymal stem cells from umbilical cord blood and bone marrow

We have identified the most appropriate method of isolating human umbilical cord matrix-derived mesenchymal stem cells (UCM-MSCs) and compared morphological, phenotypic, proliferative, and differentiation characteristics of UCM-MSCs with bone marrow-derived MSCs (BM-MSCs) and umbilical cord blood-derived MSCs (UCB-MSCs). Three explant culture methods and 3 enzymatic methods were compared with regards to time for primary culture, cell number, cell morphology, immune phenotype, and differentiation potential. Morphological, phenotypic, proliferative, and differentiation characteristics of UCM-MSCs, BM-MSCs, and UCB-MSCs were also compared. UCM-MSCs isolated using the 10 mm size tissue explant method led to shorter primary culture time, higher numbers of isolated cells, and higher proliferation rates compared with other isolation methods. Immune phenotype and multilineage differentiation capacity did not differ significantly among 6 groups. UCM-MSCs had similar characteristics as BM-MSCs and UCB-MSCs, including fibroblastic morphology, typical immunophenotypic markers, and multilineage differentiation capacity. In comparison with UCB-MSCs and BM-MSCs, UCM-MSCs have higher proliferative capacity, higher rate of chondrogenic differentiation, and higher expression of CD 146. The results suggest that the 10 mm size tissue culture method is the optimal protocol for the isolation of UCM-MSCs. Given the distinct advantages of UC, such as accessibility, painless acquisition, and abundance of cells obtained, we propose that UC be considered an alternative to BM and UCB as a source of MSCs for cell therapy.

Comparative analysis of human mesenchymal stem cells from bone marrow, adipose tissue, and umbilical cord blood as sources of cell therapy

Various source-derived mesenchymal stem cells (MSCs) have been considered for cell therapeutics in incurable diseases. To characterize MSCs from different sources, we compared human bone marrow (BM), adipose tissue (AT), and umbilical cord blood-derived MSCs (UCB-MSCs) for surface antigen expression, differentiation ability, proliferation capacity, clonality, tolerance for aging, and paracrine activity. Although MSCs from different tissues have similar levels of surface antigen expression, immunosuppressive activity, and differentiation ability, UCB-MSCs had the highest rate of cell proliferation and clonality, and significantly lower expression of p53, p21, and p16, well known markers of senescence. Since paracrine action is the main action of MSCs, we examined the anti-inflammatory activity of each MSC under lipopolysaccharide (LPS)-induced inflammation. Co-culture of UCB-MSCs with LPS-treated rat alveolar macrophage, reduced expression of inflammatory cytokines including interleukin-1α (IL-1α), IL-6, and IL-8 via angiopoietin-1 (Ang-1). Using recombinant Ang-1 as potential soluble paracrine factor or its small interference RNA (siRNA), we found that Ang-1 secretion was responsible for this beneficial effect in part by preventing inflammation. Our results demonstrate that primitive UCB-MSCs have biological advantages in comparison to adult sources, making UCB-MSCs a useful model for clinical applications of cell therapy.

Purified human pancreatic duct cell culture conditions defined by serum-free high-content growth factor screening

The proliferation of pancreatic duct-like CK19+ cells has implications for multiple disease states including pancreatic cancer and diabetes mellitus. The in vitro study of this important cell type has been hampered by their limited expansion compared to fibroblast-like vimentin+ cells that overgrow primary cultures. We aimed to develop a screening platform for duct cell mitogens after depletion of the vimentin+ population. The CD90 cell surface marker was used to remove the vimentin+ cells from islet-depleted human pancreas cell cultures by magnetic-activated cell sorting. Cell sorting decreased CD90+ cell contamination of the cultures from 34±20% to 1.3±0.6%, yielding purified CK19+ cultures with epithelial morphology. A full-factorial experimental design was then applied to test the mitogenic effects of bFGF, EGF, HGF, KGF and VEGF. After 6 days in test conditions, the cells were labelled with BrdU, stained and analyzed by high-throughput imaging. This screening assay confirmed the expected mitogenic effects of bFGF, EGF, HGF and KGF on CK19+ cells and additionally revealed interactions between these factors and VEGF. A serum-free medium containing bFGF, EGF, HGF and KGF led to CK19+ cell expansion comparable to the addition of 10% serum. The methods developed in this work should advance pancreatic cancer and diabetes research by providing effective cell culture and high-throughput screening platforms to study purified primary pancreatic CK19+ cells.

Expansion of Mesenchymal Stem/Stromal cells under xenogenic-free culture conditions

Mesenchymal Stem/Stromal cells (MSCs) are increasingly applied in cell-based regenerative medicine. To yield clinically relevant cell doses, ex vivo expansion of MSCs is required to be compliant with good manufacturing practice (GMP) guidelines. A lack of standardization and harmonization seems to hamper rapid progress in the translational phase. Most protocols still use fetal bovine serum (FBS) to expand MSCs. However, the high lot-to-lot variability, risk of contamination and immunization call for xenogenic-free culture conditions. Chemically defined media are the ultimate achievement in terms of standardization. These media, however, need to maintain all key cellular and therapy-relevant features of MSCs. Because of the numerous constituents of FBS, the development of such chemically defined media with an optimal composition of the few essential factors is only beginning. Meanwhile, various human blood-derived components are under investigation, including human plasma, human serum, human umbilical cord blood serum and human platelet derivatives such as platelet lysate.

Human umbilical cord blood-derived stromal cells are superior to human umbilical cord blood-derived mesenchymal stem cells in inducing myeloid lineage differentiation in vitro

Stromal cells and mesenchymal stem cells (MSCs), 2 important cell populations within the hematopoietic microenvironment, may play an important role in the development of hematopoietic stem/progenitor cells. We have successfully cultured human umbilical cord blood-derived stromal cells (hUCBDSCs). It has been demonstrated that MSCs also exist in hUCB. However, we have not found any reports on the distinct characteristics of hUCBDSCs and human umbilical cord blood-derived mesenchymal stem cells (hUCBDMSCs). In this study, hUCBDSCs and hUCBDMSCs were isolated from the cord blood of full-term infants using the same density gradient centrifugation and cultured in the appropriate medium. Some biological characteristics and hematopoietic supportive functions were compared in vitro. hUCBDSCs were distinct from hUCBDMSCs in morphology, proliferation, cell cycle, passage, immunophenotype, and the capacity for classical tri-lineage differentiation. Finally, quantitative real-time polymerase chain reaction analysis revealed that granulocyte colony-stimulating factor (G-CSF) gene expression was higher in hUCBDSCs than that in hUCBDMSCs. Enzyme-linked immunosorbent assay revealed that the secretion of G-CSF, thrombopoietin (TPO), and granulocyte macrophage colony-stimulating factor (GM-CSF) by hUCBDSCs was higher than that by hUCBDMSCs. After coculture, the granulocyte/macrophage colony-forming units (CFU-GM) of hematopoietic cells from the hUCBDSC feeder layer was more than that from the hUCBDMSC feeder layer. Flow cytometry was used to detect CD34(+) hematopoietic stem/progenitor cell committed differentiation during 14 days of coculture; the results demonstrated that CD14 and CD33 expression in hUCBDSCs was significantly higher than their expression in hUCBDMSCs. This observation was also true for the granulocyte lineage marker, CD15. This marker was expressed beginning at day 7 in hUCBDSCs. It was expressed earlier and at a higher level in hUCBDSCs compared with hUCBDMSCs. In conclusion, hUCBDSCs are different from hUCBDMSCs. hUCBDSCs are superior to hUCBDMSCs in supporting hematopoiesis stem/progenitor cells differentiation into myeloid lineage cells at an early stage in vitro.

Isolation and characterization of mesenchymal stem cells from human umbilical cord blood: reevaluation of critical factors for successful isolation and high ability to proliferate and differentiate to chondrocytes as compared to mesenchymal stem cells from bone marrow and adipose tissue

Human umbilical cord blood (CB) is a potential source for mesenchymal stem cells (MSC) capable of forming specific tissues, for example, bone, cartilage, or muscle. However, difficulty isolating MSC from CB (CB-MSC) has impeded their clinical application. Using more than 450 CB units donated to two public CB banks, we found that successful cell recovery fits a hyper-exponential function of time since birth with very high fidelity. Additionally, significant improvement in the isolation of CB-MSC was achieved by selecting cord blood units having a volume ≥90  ml and time ≤2  h after donor's birth. This resulted in 90% success in isolation of CB-MSC by density gradient purification and without a requirement for immunoaffinity methods as previously reported. Using MSC isolated from bone marrow (BM-MSC) and adipose tissue (AT-MSC) as reference controls, we observed that CB-MSC exhibited a higher proliferation rate and expanded to the order of the 1 × 10(9)  cells required for cell therapies. CB-MSC showed karyotype stability after prolonged expansion. Functionally, CB-MSC could be more readily induced to differentiate into chondrocytes than could BM-MSC and AT-MSC. CB-MSC showed immunosuppressive activity equal to that of BM-MSC and AT-MSC. Collectively, our data indicate that viable CB-MSC could be obtained consistently and that CB should be reconsidered as a practical source of MSC for cell therapy and regenerative medicine using the well established CB banking system.

The isolation and culture of human cord blood-derived mesenchymal stem cells under low oxygen conditions

There is growing evidence that low oxygen conditions are beneficial for in vitro stem cell culturing. Mimicking the physiological oxygen tension of the placental stem cell niche in cell expansion can -ultimately result in more robust cell expansion. Growing evidence also suggests that hypoxic preconditioning of cells may improve therapeutic outcomes. Here we describe a scalable method that enables mesenchymal stromal cell expansion from virtually every cord blood unit, including those that would normally be disqualified from banking. In addition, the cells obtained by the described method fulfill exclusively the mesenchymal stromal cell characteristics defined by the International Society for Cellular Therapy.

Adventures in time and space: Nonlinearity and complexity of cytokine effects on stem cell fate decisions

Cytokines are central factors in the control of stem cell fate decisions and, as such, they are invaluable to those interested in the manipulation of stem and progenitor cells for clinical or research purposes. In their in vivo niches or in optimized cultures, stem cells are exposed to multiple cytokines, matrix proteins and other cell types that provide individual and combinatorial signals that influence their self-renewal, proliferation and differentiation. Although the individual effects of cytokines are well-characterized in terms of increases or decreases in stem cell expansion or in the production of specific cell lineages, their interactions are often overlooked. Factorial design experiments in association with multiple linear regression is a powerful multivariate approach to derive response-surface models and to obtain a quantitative understanding of cytokine dose and interactions effects. On the other hand, cytokine interactions detected in stem cell processes can be difficult to interpret due to the fact that the cell populations examined are often heterogeneous, that cytokines can exhibit pleiotropy and redundancy and that they can also be endogenously produced. This perspective piece presents a list of possible biological mechanisms that can give rise to positive and negative two-way factor interactions in the context of in vivo and in vitro stem cell-based processes. These interpretations are based on insights provided by recent studies examining intra- and extra-cellular signaling pathways in adult and embryonic stem cells. Cytokine interactions have been classified according to four main types of molecular and cellular mechanisms: (i) interactions due to co-signaling; (ii) interactions due to sequential actions; (iii) interactions due to high-dose saturation and inhibition; and (iv) interactions due to intercellular signaling networks. For each mechanism, possible patterns of regression coefficients corresponding to the cytokine main effects, quadratic effects and two-way interactions effects are provided. Finally, directions for future mechanistic studies are presented.

Cord blood--an alternative source for bone regeneration

Bone regeneration is one of the best investigated pathways in mesenchymal stromal cell (MSC) biology. Therefore strong efforts have been made to introduce tissue engineering and cell therapeutics as an alternative treatment option for patients with bone defects. This review of the literature gives an overview of MSC biology aiming for clinical application including advantages but also specific challenges and problems which are associated with cord blood derived stromal cell (CB-MSC) as a source for bone regeneration. The use of postnatal CB-MSC is ethically uncomplicated and requires no invasive harvesting procedure. Moreover, most data document a high osteogenic potential of CB-MCS and also low immunoreactivity compared with other MSC types. The expression profile of CB-MSC during osteogenic differentiation shows similarities to that of other MSC types. Within the umbilical cord different MSC types have been characterized which are potent to differentiate into osteoblasts. In contrast to a large number of in vitro investigations there are only few in vivo studies available so far.