Stem cells for regenerative medicine—Biological attributes and clinical application

Isolation and characterization of a new SHED cell line as a standard source for stem cell research and clinical translation

BACKGROUND AND AIMS

Stem cells from human exfoliated deciduous teeth (SHED) are multi-potent mesenchymal stem/stromal cells (MSCs) and are inspected a favorable, non-invasive source beneficial to stem cell-mediated regeneration of damaged tissues. Our aim was to establish and characterize a non-immortalized SHED cell line as an accessible resource and novel platform for stem cell research and tissue regeneration studies.

METHODS

A Healthy exfoliated deciduous molar was extracted from a 12-year-old girl and shipped to an animal cell culture laboratory. Outgrowing primary cells from explanted small pulp tissues were monitored daily and characterized after passage 3 both morphologically and functionally. The SHED cell line was characterized by calculation of doubling time, cytogenetic analyses, STR analysis, adherence to cell culture flasks under standard cell culture media, and immunophenotypic analysis of specific MSC markers (CD90+, CD73+, CD34- and CD45-) using flow cytometry method. Differentiation potential to osteoblast, adipocyte, and chondrocyte was evaluated under standard differentiation media Expression of OCT-4 and NANOG genes was also assessed using RT-PCR method.

RESULTS

After the third day, SHED cells were visible. SHED cells were subcultured when they reached 90 % confluence after approximately 17 days. The doubling time of SHED cells was forty seven hours. SHED immunophenotyping showed the high expression level of CD90 (99.2 %) and CD73 (45.9 %), and approximately no expression of CD34 (0.079 %) and CD45 (0.19 %). The human origin, female gender and chromosomal normality of SHED cells was confirmed by cytogenetic analysis. The STR matching analysis showed that SHED cells are well-identified and authentic. No genetic instability and cross-contamination were observed in SHED cells.

CONCLUSIONS

This study provides a new SHED cell line with a normal karyotype and all the characteristics of MSCs, which can be used as a favorable model cell line in biomedical research and a promising source for clinical translation.

Comparison Among Bone Marrow and Wheat Flour's Mixture and Standard Treatment on Healing Second-Degree Burn Wound in Rats

The treatment of extensive skin burns remains as a challenge for health care personnel. This study aimed to compare the combination of bone marrow and wheat flour with standard treatment on animal models. In this experimental study, 45 male rats were randomly assigned into three groups as follows: The first group was control (no treatment), the second group received bone marrow and wheat flour combination topically, and the third group received standard treatment (1% silver sulfadiazine). The treatment lasted for up to 21 days. On the 22nd day, the rats were killed. The number of blood vessels and hair follicles was measured in the burn wound bed. The area and depth of the wound were also measured. Data were analyzed using SPSS software version 16. The results showed that, complete closure of the wound was better in the bone marrow treated group compared with the group receiving the silver sulfadiazine and the control group. Furthermore, the wound healing was better in the silver sulfadiazine group compared with the control group. Microscopic examination revealed a significant increase in the number of hair follicles and blood vessels in the bone marrow and silver groups compared with the control group. The results showed that, the group treated with bone marrow, because of the presence of mesenchymal and stem cells can cause stimulating angiogenesis and producing vegetative tissue, hence it improved maturation, shrinkage, and contraction of the wound in comparison with the silver sulfadiazine and control groups.

Potential Clinical Applications of Stem Cells in Regenerative Medicine

The field of regenerative medicine is looking for a pluripotent/multipotent stem cell able to differentiate across germ layers and be safely employed in therapy. Unfortunately, with the exception of hematopoietic stem/progenitor cells (HSPCs) for hematological applications, the current clinical results with stem cells are somewhat disappointing. The potential clinical applications of the more primitive embryonic stem cells (ESCs) and induced pluripotent stem cells (iPSCs) have so far been discouraging, as both have exhibited several problems, including genomic instability, a risk of teratoma formation, and the possibility of rejection. Therefore, the only safe stem cells that have so far been employed in regenerative medicine are monopotent stem cells, such as the abovementioned HSPCs or mesenchymal stem cells (MSCs) isolated from postnatal tissues. However, their monopotency, and therefore limited differentiation potential, is a barrier to their broader application in the clinic. Interestingly, results have accumulated indicating that adult tissues contain rare, early-development stem cells known as very small embryonic-like stem cells (VSELs), which can differentiate into cells from more than one germ layer. This chapter addresses different sources of stem cells for potential clinical application and their advantages and problems to be solved.

Bone marrow niche-mimetics modulate HSPC function via integrin signaling

The bone marrow (BM) microenvironment provides critical physical cues for hematopoietic stem and progenitor cell (HSPC) maintenance and fate decision mediated by cell-matrix interactions. However, the mechanisms underlying matrix communication and signal transduction are less well understood. Contrary, stem cell culture is mainly facilitated in suspension cultures. Here, we used bone marrow-mimetic decellularized extracellular matrix (ECM) scaffolds derived from mesenchymal stromal cells (MSCs) to study HSPC-ECM interaction. Seeding freshly isolated HSPCs adherent (AT) and non-adherent (SN) cells were found. We detected enhanced expansion and active migration of AT-cells mediated by ECM incorporated stromal derived factor one. Probing cell mechanics, AT-cells displayed naïve cell deformation compared to SN-cells indicating physical recognition of ECM material properties by focal adhesion. Integrin αIIb (CD41), αV (CD51) and β3 (CD61) were found to be induced. Signaling focal contacts via ITGβ3 were identified to facilitate cell adhesion, migration and mediate ECM-physical cues to modulate HSPC function.

Evaluation of umbilical cord blood CD34+ hematopoietic stem cells expansion with inhibition of TGF-β receptorII in co-culture with bone marrow mesenchymal stromal cells

BACKGROUND

Umbilical cord blood (UCB) is an important source of hematopoietic stem cells (HSCs). However, low number of HSCs in UCB has been an obstacle for adult hematopoietic stem cell transplantation. The expansion of HSCs in culture is one approach to overcome this problem. In this study, we investigated the expansion of UCB-HSCs by using human bone marrow mesenchymal stromal cells (MSCs) as feeder layer as well as inhibiting the TGF-β signaling pathway through reduction of TGF-βRII expression.

MATERIALS AND METHODS

CD34(+) cells were isolated from UCB and transfected by SiRNA targeting TGF-βRII mRNA. CD34(+) cells were expanded in four culture media with different conditions, including 1) expansion of CD34(+) cells in serum free medium containing growth factors, 2) expansion of cells transfected with SiRNA targeting TGF-βRII in medium containing growth factors, 3) expansion of cells in presence of growth factors and MSCs, 4) expansion of cells transfected with SiRNA targeting TGF-βRII on MSCs feeder layer in medium containing growth factors. These culture conditions were evaluated for the number of total nucleated cells (TNCs), CD34 surface marker as well as using CFU assay on 8th day after culture.

RESULTS

The fold increase in CD34(+) cells, TNCs, and colony numbers (71.8±6.9, 93.2±10.2 and 128±10, respectively) was observed to be highest in fourth culture medium compared to other culture conditions. The difference between number of cells in four culture media in 8th day compared to unexpanded cells (0day) before expansion was statistically significant (P<0.05).

CONCLUSION

The results showed that transfection of CD34(+) cells with SiRNA targeting TGF-βRII and their co-culture with MSCs could considerably increase the number of progenitors. Therefore, this method could be useful for UCB-HSCs expansion.

Endothelial Progenitor Cell Fraction Contained in Bone Marrow-Derived Mesenchymal Stem Cell Populations Impairs Osteogenic Differentiation

In bone tissue engineering (TE) endothelial cell-osteoblast cocultures are known to induce synergies of cell differentiation and activity. Bone marrow mononucleated cells (BMCs) are a rich source of mesenchymal stem cells (MSCs) able to develop an osteogenic phenotype. Endothelial progenitor cells (EPCs) are also present within BMC. In this study we investigate the effect of EPCs present in the BMC population on MSCs osteogenic differentiation. Human BMCs were isolated and separated into two populations. The MSC population was selected through plastic adhesion capacity. EPCs (CD34⁺ and CD133⁺) were removed from the BMC population and the resulting population was named depleted MSCs. Both populations were cultured over 28 days in osteogenic medium (Dex⁺) or medium containing platelet lysate (PL). MSC population grew faster than depleted MSCs in both media, and PL containing medium accelerated the proliferation for both populations. Cell differentiation was much higher in Dex⁺ medium in both cases. Real-time RT-PCR revealed upregulation of osteogenic marker genes in depleted MSCs. Higher values of ALP activity and matrix mineralization analyses confirmed these results. Our study advocates that absence of EPCs in the MSC population enables higher osteogenic gene expression and matrix mineralization and therefore may lead to advanced bone neoformation necessary for TE constructs.

A Short-activating RNA Oligonucleotide Targeting the Islet β-cell Transcriptional Factor MafA in CD34(+) Cells

Upon functional loss of insulin producing islet β-cells, some patients with diabetes become dependent on life-long insulin supplementation therapy. Bioengineering surrogate insulin producing cells is an alternative replacement strategy. We have developed a novel approach using short-activating RNA oligonucleotides to differentiate adult human CD34(+) cells into insulin-secreting cells. By transfecting RNA to increase transcript levels of the master regulator of insulin biosynthesis, v-maf musculoaponeurotic fibrosarcoma oncogene homolog A (MafA), several pancreatic endodermal genes were upregulated during the differentiation procedure. These included Pancreatic and duodenal homeobox gene-1 (PDX1), Neurogenin 3, NeuroD, and NK6 homeobox 1 (NKx6-1). Differentiated CD34(+) cells also expressed glucokinase, glucagon-like peptide 1 receptor (GLP1R), sulfonylurea receptor-1 (SUR1) and phogrin-all essential for glucose sensitivity and insulin secretion. The differentiated cells appropriately processed C-peptide and insulin in response to increasing glucose stimulation as shown by enzyme-linked immunosorbent assay (ELISA), fluorescence-activated cell sorting analysis, western blotting, and immunofluorescence staining. We provide a new approach using short-activating RNA in developing insulin producing surrogate cells for treating diabetes.Molecular Therapy - Nucleic Acids (2013) 2, e97; doi:10.1038/mtna.2013.23; advance online publication 4 June 2013.

Evaluation of umbilical cord blood CD34 (+) hematopoietic stem cell expansion in co-culture with bone marrow mesenchymal stem cells in the presence of TEPA

BACKGROUND

During the last three decades hematopoietic stem cells (HSC) have become a standard protocol for the treatment of many hematologic malignancies and non-malignant disorders. Umbilical cord blood (UCB), as a source of HSCs, has many advantages compared with other sources. One major drawback in using this source in treatment of adult patients is the low HSC dose available. Ex vivo expansion of HSCs is a solution to overcome this limitation. In this study we used TEPA, as a Cu chelator, and human bone marrow (BM) mesenchymal stem cells (MSCs) to investigate expansion rate of UCB-HSCs.

MATERIALS AND METHODS

CB-HSCs were isolated using miniMACS magnetic separation system. We cultured the enriched CD34(+)cells in various conditions: culture condition A, supplemented only with recombinant cytokines; culture condition B, supplemented with BM-MSCs as a cell feeder layer and recombinant cytokines; culture condition C, supplemented with recombinant cytokines and TEPA; culture condition D, supplemented with recombinant cytokines, BM-MSCs as a cell feeder layer and TEPA. In order to evaluate the HSC expansion, we performed cell count, analysis of CD34(+) expression by flow cytometry, and colony-forming cell assay on Day 10 after culture.

RESULTS

The most fold increase in CD34(+) cell, total cell, and total colony numbers was observed in culture condition D (110.11 ± 15.3, 118.5 ± 21, and 172.9 ± 44.7, respectively) compared to other conditions.

CONCLUSION

The results showed that co-culture of HSCs with BM-MSCs in the presence of copper chelating agent (TEPA) could dramatically increase expansion rate of UCB-HSCs. Therefore, this strategy could be useful for HSC expansion.

Pluripotent and multipotent stem cells in adult tissues

One of the most intriguing questions in stem cell biology is whether pluripotent stem cells exist in adult tissues. Several groups of investigators employing i) various isolation protocols, ii) detection of surface markers, and iii) experimental in vitro and in vivo models, have reported the presence of cells that possess a pluripotent character in adult tissues. Such cells were assigned various operational abbreviations and names in the literature that added confusion to the field and raised the basic question of whether these are truly distinct or overlapping populations of the same primitive stem cells. Unfortunately, these cells were never characterized side-by-side to address this important issue. Nevertheless, taking into consideration their common features described in the literature, it is very likely that various investigators have described overlapping populations of developmentally early stem cells that are closely related. These different populations of stem cells will be reviewed in this paper.

Methods of cell purification: a critical juncture for laboratory research and translational science

Research in cell biology and the development of translational technologies are driven by competition, public expectations, and regulatory oversight, putting these fields at a critical juncture. Success in these fields is quickly becoming dependent on the ability of researchers to identify and isolate specific cell populations from heterogeneous mixtures accurately and efficiently. Many methods for cell purification have been developed, and each has advantages and disadvantages that must be considered in light of the intended application. Current cell separation strategies make use of surface proteins, genetic expression, and physics to isolate specific cells by phenotypic traits. Cell purification is also dependent on the cellular reagents available for use and the intended application, as these factors may preclude certain mechanisms used in the processes of labeling and sorting cells.

Promotion of cutaneous wound healing by local application of mesenchymal stem cells derived from human umbilical cord blood

This study aimed to determine whether mesenchymal stem cells (MSCs) derived from umbilical cord blood (UCB) would promote cutaneous wound healing. MSCs from human UCB were isolated and identified. The characteristics of the isolated MSCs' growth and proliferation were assayed in vitro. The MSCs labeled with 5-bromodeoxyuridine (BrdU) were applied on fresh cutaneous mice wounds. The healing rates were surveyed. The distribution and the differentiation into keratinocytes of the labeled MSCs in the wound tissue were checked by immunohistochemistry staining. The isolated MSCs could grow and proliferate well in vitro. The isolated MSCs from UCB could be labeled by 5-bromodeoxyuridine successfully. The MSCs derived from UCB could enhance the healing of mice skin defect wounds, and it was found that the implanted MSCs could differentiate into keratinocyte in the wound tissue. It was demonstrated that MSCs from UCB can be isolated and proliferated successfully. The local administration of MSCs derived from UCB improves skin defect wound healing in mice.

Biotechnology-Derived Medicines: What are They? A Pharmacological and a Historical Perspective

Biologicals, that is, medicines obtained from living organisms, are not new. History provides many examples of animal or human extracts being used to prevent or treat human diseases. Physicians have thus been aware for centuries of the therapeutic value of our own molecules. The difficulty laid many times in how to obtain these self or self-like compounds. Biotechnology - a technology by which manipulated living organisms are utilized to generate useful products such as drugs - provided a revolutionary answer. We know how to genetically engineer bacteria, yeast, insect or mammalian cells to synthesize human molecules, the so-called human recombinant therapeutic proteins. Murine and humanized monoclonal antibodies against human antigens are also biotechnological products. The number of biotechnological drugs being marketed, and those in clinical trials or awaiting authorization, is growing exponentially. We are now still on the beginnings of a new era in pharmacotherapy of which it is impossible to see the end. Pharmacologists need to keep pace with these changes and develop new skills. They may even have to challenge old assumptions in order to investigate new molecules. Using an easy and comprehensible approach, this review article revisits ‘bio-concepts’, and underlines the real dimension of the challenge.

Hematopoietic stem cells in co-culture with mesenchymal stromal cells--modeling the niche compartments in vitro

BACKGROUND

Hematopoietic stem cells located in the bone marrow interact with a specific microenvironment referred to as the stem cell niche. Data derived from ex vivo co-culture systems using mesenchymal stromal cells as a feeder cell layer suggest that cell-to-cell contact has a significant impact on the expansion, migratory potential and 'stemness' of hematopoietic stem cells. Here we investigated in detail the spatial relationship between hematopoietic stem cells and mesenchymal stromal cells during ex vivo expansion.

DESIGN AND METHODS

In the co-culture system, we defined three distinct localizations of hematopoietic stem cells relative to the mesenchymal stromal cell layer: (i) those in supernatant (non-adherent cells); (ii) those adhering to the surface of mesenchymal stromal cells (phase-bright cells) and (iii) those beneath the mesenchymal stromal cells (phase-dim cells). Cell cycle, proliferation, cell division and immunophenotype of these three cell fractions were evaluated from day 1 to 7.

RESULTS

Phase-bright cells contained the highest proportion of cycling progenitors during co-culture. In contrast, phase-dim cells divided much more slowly and retained a more immature phenotype compared to the other cell fractions. The phase-dim compartment was soon enriched for CD34(+)/CD38(-) cells. Migration beneath the mesenchymal stromal cell layer could be hampered by inhibiting integrin beta1 or CXCR4.

CONCLUSIONS

Our data suggest that the mesenchymal stromal cell surface is the predominant site of proliferation of hematopoietic stem cells, whereas the compartment beneath the mesenchymal stromal cell layer seems to mimic the stem cell niche for more immature cells. The SDF-1/CXCR4 interaction and integrin-mediated cell adhesion play important roles in the distribution of hematopoietic stem cells in the co-culture system.

EpCAM is involved in maintenance of the murine embryonic stem cell phenotype

Epithelial cell adhesion molecule EpCAM is a transmembrane glycoprotein that is expressed on subsets of normal epithelia, numerous stem- and progenitor-type cells, and most carcinomas and highly overexpressed on cancer-initiating cells. The role of EpCAM in early development, particularly in stem-like cells, has remained unclear. Here, we show that the maintenance of self-renewal in murine embryonic stem (ES) cells depends on the high-level expression of EpCAM. Cultivation of ES cells under differentiation conditions in the absence of leukemia inhibitory factor (LIF) caused down-regulation of EpCAM along with decreased expression of cellular myelocytomatosis oncogene (c-Myc), Sex-determining region Y-Box 2, Octamer 3/4 (Oct3/4), and Stat3. As a consequence ES cells were morphologically differentiated and ceased to proliferate. RNA interference-mediated inhibition of EpCAM expression under self-renewal conditions resulted in quantitatively decreased proliferation, decreased Oct3/4, SSEA-1, and c-Myc expression, and diminished alkaline phosphatase activity. Conversely, exogenous expression of EpCAM partially compensated for the requirement of ES cells for LIF to retain a stem cell phenotype. Thus, murine EpCAM is a transmembrane protein, which is essential but by itself is not sufficient for maintenance of the ES cell phenotype.

Genetic control of wayward pluripotent stem cells and their progeny after transplantation

The proliferative capacity of pluripotent stem cells and their progeny brings a unique aspect to therapeutics, in that once a transplant is initiated the therapist no longer has control of the therapy. In the context of the recent FDA approval of a human ESC trial and report of a neuronal-stem-cell-derived tumor in a human trial, strategies need to be developed to control wayward pluripotent stem cells. Here, we focus on one approach: direct genetic modification of the cells prior to transplantation with genes that can prevent the adverse events and/or eliminate the transplanted cells and their progeny.