Retinoic Acid-Mediated Differentiation of Mouse Embryonic Stem Cells to Neuronal Cells

The capability of pluripotent embryonic stem cells (ESCs) to proliferate and differentiate into specific lineages makes them an important avenue of research in the field of cell therapy as well as a useful model to study patterns of differentiation and gene expression, recapitulating many events that occur during the very early stages of development of the mammalian embryo. With striking similarities that exist between inherently programmed embryonic development of the nervous system in vivo and the differentiation of ESCs in vitro, they have already been used to treat locomotive and cognitive deficits caused by brain injury in rodents. A suitable differentiation model thus empowers us with all these opportunities. In this chapter, we describe a neural differentiation model from mouse embryonic stem cells using retinoic acid as the inducer. This method is among the most commonly used one to acquire a homogeneous population of neuronal progenitor cells or mature neurons as desired. The method is scalable, efficient, and results in production of ~70% neural progenitor cells within 4-6 days.

Sustained growth factor delivery from bioactive PNIPAM-grafted-chitosan/heparin multilayers as a tool to promote growth and migration of cells

Delivery of growth factors (GFs) is challenging for regulation of cell proliferation and differentiation due to their rapid inactivation under physiological conditions. Here, a bioactive polyelectrolyte multilayer (PEM) is engineered by the combination of thermoresponsive poly(N-isopropylacrylamide) (PNIPAM) and glycosaminoglycans to be used as reservoir for GF storage. PNIPAM-grafted-chitosan (PChi) with two degrees of substitution (DS) are synthesized, namely LMW* (DS 0.14) and HMW (DS 0.03), by grafting low (2 kDa) and high (10 kDa) molecular weight of PNIPAM on the backbone of chitosan (Chi) to be employed as polycations to form PEM with the polyanion heparin (Hep) at pH 4. Subsequently, PEMs are chemically crosslinked to improve their stability at physiological pH 7.4. Resulting surface and mechanical properties indicate that PEM containing HMW is responsive to temperature at 20 °C and 37 °C, while LMW is not. More importantly, Hep as terminal layer combined with HMW allows not only a better retention of the adhesive protein vitronectin but also a sustained release of FGF-2 at 37 °C. With the synergistic effect of vitronectin and matrix-bound FGF-2, significant promotion on adhesion, proliferation, and migration of 3T3 mouse embryonic fibroblasts is achieved on HMW-containing PEM compared to Chi-containing PEM and exogenously added FGF-2. Thus, PEM containing PNIPAM in combination with bioactive glycosaminoglycans like Hep represents a versatile approach to fabricate a GF delivery system for efficient cell culture, which can be potentially served as cell culture substrate for production of (stem) cells and bioactive wound dressing for tissue regeneration.

Low-glucose culture environment can enhance the wound healing capability of diabetic adipose-derived stem cells

BACKGROUND

Application of autologous adipose-derived stem cells (ASC) for diabetic chronic wounds has become an emerging treatment option. However, ASCs from diabetic individuals showed impaired cell function and suboptimal wound healing effects. We proposed that adopting a low-glucose level in the culture medium for diabetic ASCs may restore their pro-healing capabilities.

METHODS

ASCs from diabetic humans and mice were retrieved and cultured in high-glucose (HG, 4.5 g/L) or low-glucose (LG, 1.0 g/L) conditions. Cell characteristics and functions were investigated in vitro. Moreover, we applied diabetic murine ASCs cultured in HG or LG condition to a wound healing model in diabetic mice to compare their healing capabilities in vivo.

RESULTS

Human ASCs exhibited decreased cell proliferation and migration with enhanced senescence when cultured in HG condition in vitro. Similar findings were noted in ASCs derived from diabetic mice. The inferior cellular functions could be partially recovered when they were cultured in LG condition. In the animal study, wounds healed faster when treated with HG- or LG-cultured diabetic ASCs relative to the control group. Moreover, higher collagen density, more angiogenesis and cellular retention of applied ASCs were found in wound tissues treated with diabetic ASCs cultured in LG condition.

CONCLUSIONS

In line with the literature, our study showed that a diabetic milieu exerts an adverse effect on ASCs. Adopting LG culture condition is a simple and effective approach to enhance the wound healing capabilities of diabetic ASCs, which is valuable for the clinical application of autologous ASCs from diabetic patients.

State of the Art Procedures for the Isolation and Characterization of Mesoangioblasts

Adult skeletal muscle is a dynamic tissue able to regenerate quite efficiently, thanks to the presence of stem cell machinery. Besides the quiescent satellite cells that are activated upon injury or paracrine factors, other stem cells are described to be directly or indirectly involved in adult myogenesis. Mesoangioblasts (MABs) are vessel-associated stem cells originally isolated from embryonic dorsal aorta and, at later stages, from the adult muscle interstitium expressing pericyte markers. Adult MABs entered clinical trials for the treatment of Duchenne muscular dystrophy and the transcriptome of human fetal MABs has been described. In addition, single cell RNA-seq analyses provide novel information on adult murine MABs and more in general in interstitial muscle stem cells. This chapter provides state-of-the-art techniques to isolate and characterize murine MABs, fetal and adult human MABs.

Long-Term Ex Vivo Expansion of Murine Spermatogonial Stem Cells in a Simple Serum-Free Medium

Spermatogonial stem cells (SSCs) possess both self-renewal and differentiation abilities to sustain lifelong production of enormous numbers of spermatozoa in males. SSCs hold a unique position among tissue-specific stem cells in adults because of their ability to transmit the genetic information to subsequent generations. Ex vivo expansion of SSCs in conjunction with their transplantation is highly invaluable to study SSCs and develop new reproductive technologies for therapeutic applications. In this chapter, we describe a culture system involving a simple serum-free medium for mouse SSCs. Elimination of the serum from the culture is important to enhance the effects of exogenous factors, which are rather masked by the serum, and to avert the serum-induced inflammatory responses of testicular mesenchymal cells, which cause adverse effects on SSC proliferation. Consequently, using this culture system has proven for the first time that glial cell line-derived neurotrophic factor (GDNF) was found to be the key factor to drive the self-renewing proliferation of SSCs, and fibroblast growth factor 2 enhanced the GDNF-dependent proliferation of SSCs. Besides determining these two key cytokines, the simplicity of the system enabled individual modification of its components to develop long-term cultures of rat and rabbit SSCs. The basics of these culture systems will enable development of the culture conditions for human and other mammalian SSCs in the near future.

Long-Term Human Hematopoietic Stem Cell Culture in Microdroplets

We previously reported a new approach for micromanipulation and encapsulation of human stem cells using a droplet-based microfluidic device. This approach demonstrated the possibility of encapsulating and culturing difficult-to-preserve primary human hematopoietic stem cells using an engineered double-layered bead composed by an inner layer of alginate and an outer layer of Puramatrix. We also demonstrated the maintenance and expansion of Multiple Myeloma cells in this construction. Here, the presented microfluidic technique is applied to construct a 3D biomimetic model to recapitulate the human hematopoietic stem cell niche using double-layered hydrogel beads cultured in 10% FBS culture medium. In this model, the long-term maintenance of the number of cells and expansion of hHSCS encapsulated in the proposed structures was observed. Additionally, a phenotypic characterization of the human hematopoietic stem cells generated in the presented biomimetic model was performed in order to assess their long-term stemness maintenance. Results indicate that the ex vivo cultured human CD34+ cells from bone marrow were viable, maintained, and expanded over a time span of eight weeks. This novel long-term stem cell culture methodology could represent a novel breakthrough to improve Hematopoietic Progenitor cell Transplant (HPT) as well as a novel tool for further study of the biochemical and biophysical factors influencing stem cell behavior. This technology opens a myriad of new applications as a universal stem cell niche model potentially able to expand other types of cells.

Isolation and In Vitro Culture of Human Gut Progenitor Cells

The gastrointestinal epithelium is a highly regenerative organ, where each cell is replaced in a cycle of 4-6 days, depending on the mammalian species. This highly proliferative state is driven by gastrointestinal stem and progenitor cells, located at the base of crypts. These cells give rise to at least six types of differentiated epithelial cells, each with a distinct function in maintaining homeostasis between the intestinal interface and the luminal environment. The isolation and culture of these cells from mammalian gastrointestinal tissue is a novel technique, which allows for the generation and maintenance of an in vitro culture system for adult epithelial cells. There are two predominant methods for isolation and propagation of gastrointestinal epithelial cells, the first is the organoid system developed in 2009, and the second is a later version known as the L-WRN spheroid system. In this chapter, we describe the method to isolate and culture human gastrointestinal stem and progenitor cells and culture them as three-dimensional spheroids using L-WRN cell conditioned media.

Transforming Growth Factor β-Activated Kinase 1 Regulates Mesenchymal Stem Cell Proliferation Through Stabilization of Yap1/Taz Proteins

Bone marrow-derived mesenchymal stem cells (BMMSCs) are multipotent stem cells capable of differentiation into a variety of cell types, proliferation, and production of clinically useful secretory factors. These advantages make BMMSCs highly useful for cell transplantation therapy. However, the molecular network underlying BMMSC proliferation remains poorly understood. Here, we showed that TGFβ-activated kinase 1 (Tak1) is a critical molecule that regulates the activation of cell cycling and that Tak1 inhibition leads to quiescence in BMMSCs both in vivo and in vitro. Mechanistically, Tak1 was phosphorylated by growth factor stimulations, allowing it to bind and stabilize Yap1/Taz, which could then be localized to the nucleus. We also demonstrated that the quiescence induction by inhibiting Tak1 increased oxidized stress tolerance and improved BMMSC engraftment in intramuscular and intrabone marrow cell transplantation models. This study reveals a novel pathway controlling BMMSC proliferation and suggests a useful method to improve the therapeutic effect of BMMSC transplantation. Stem Cells 2019;37:1595-1605.

Tunable hydrogels for mesenchymal stem cell delivery: Integrin-induced transcriptome alterations and hydrogel optimization for human wound healing

Therapeutic applications for mesenchymal stem/stromal cells (MSCs) are growing; however, the successful implementation of these therapies requires the development of appropriate MSC delivery systems. Hydrogels are ideally suited to cultivate MSCs but tuning hydrogel properties to match their specific in vivo applications remains a challenge. Thus, further characterization of how hydrogel-based delivery vehicles broadly influence MSC function and fate will help lead to the next generation of more intelligently designed delivery vehicles. To date, few attempts have been made to comprehensively characterize hydrogel impact on the MSC transcriptome. Herein, we have synthesized cell-degradable hydrogels based on bio-inert poly(ethylene glycol) tethered with specific integrin-binding small molecules and have characterized their resulting effect on the MSC transcriptome when compared with 2D cultured and untethered 3D hydrogel cultured MSCs. The 3D culture systems resulted in alterations in the MSC transcriptome, as is evident by the differential expression of genes related to extracellular matrix production, glycosylation, metabolism, signal transduction, gene epigenetic regulation, and development. For example, genes important for osteogenic differentiation were upregulated in 3D hydrogel cultures, and the expression of these genes could be partially suppressed by tethering an integrin-binding RGD peptide within the hydrogel. Highlighting the utility of tunable hydrogels, when applied to ex vivo human wounds the RGD-tethered hydrogel was able to support wound re-epithelialization, possibly due to its ability to increase PDGF expression and decrease IL-6 expression. These results will aid in future hydrogel design for a broad range of applications.

Microporous scaffolds support assembly and differentiation of pancreatic progenitors into β-cell clusters

Human pluripotent stem cells (hPSCs) represent a promising cell source for the development of β-cells for use in therapies for type 1 diabetes. Current culture approaches provide signals to mimic a temporal control of organogenesis to drive the differentiation towards β-cells. However, spatial control may represent an opportunity to improve the efficiency and manufacturing of β-cells. Herein, we adapted the current culture systems to microporous biomaterials with the hypothesis that the pores can guide the assembly of pancreatic progenitors into clusters of defined size that can influence maturation. The scaffold culture allowed hPSC-derived pancreatic progenitors to form clusters at a consistent size as cells differentiated. By modulating the scaffold pore sizes, we observed 250-425 µm pore size scaffold cultures augmented insulin expression and key β-cell maturation markers compared to cells cultured in suspension. Furthermore, when compared to suspension cultures, the scaffold culture showed increased insulin secretion in response to glucose stimulus indicating the development of functional β-cells. In addition, scaffolds facilitated cell-cell interactions enabled by the scaffold design and supported cell-mediated matrix deposition of extracellular matrix (ECM) proteins associated with the basement membrane of islet cells. We further investigated the influence of ECM on cell development by incorporating an ECM matrix on the scaffold prior to cell seeding; however, their presence did not further enhance maturation. These results suggest the microporous scaffold culture provides a conducive environment that drives in vitro differentiation of hPSC-derived insulin-producing glucose-responsive β-cells and demonstrates the feasibility of these scaffolds as a biomanufacturing platform. STATEMENT OF SIGNIFICANCE: Cell therapy for diabetes is a promising strategy, yet generating limitless insulin-producing mature β-cells from human pluripotent stem cells (hPSCs) remains a challenge. Current hPSC differentiation methods involve media containing signals to drive maturation toward β-cells and spontaneous cluster formation. Herein, we sought to provide spatial cues to guide assembly of cells into 3D structures by culture within the pores of a microporous scaffold. The scaffolds direct cell-cell interactions within the pores and provide a support for cell-mediated matrix deposition that collectively creates a niche to promote functional hPSC-derived β-cell clusters. These scaffolds for 3D culture may contribute to hPSC differentiation methods for the generation of β-cells that can treat patients with diabetes.

Isolation and Propagation of Mammary Epithelial Stem and Progenitor Cells

Several methods of mammary gland dissociation have been described that utilize a combined strategy of mechanical and enzymatic dissociation to isolate mammary epithelial cells (MECs) from intact tissue (Smalley et al., J Mammary Gland Biol Neoplasia 17:91-97, 2012). Here we detail a robust method that enables the isolation of all major stem and progenitor MEC populations, which has been successfully used to study stem cell behavior when coupled with transplantation and in vitro assays (Shackleton et al., Nature 439:84-88, 2006; Bouras et al., Cell Stem Cell 3:429-441, 2008; Sheridan et al., BMC Cancer 15:221, 2015; Jamieson et al., Development 144:1065-1071, 2017). Furthermore, we outline two prominent methods for culturing MECs for the purposes of ex vivo manipulation or study: 2D feeder layer cultures and 3D Matrigel colony assays. Importantly, all outlined methods retain stem and progenitor cell behaviors and can be used in combination with downstream in vivo, in vitro, or in silico analyses.

Concise Review: Current Status of Three-Dimensional Organoids as Preclinical Models

Three-dimensional (3D) cultures use the property of some cells to self-organize in matrices and generate structures that can be programmed to represent an organ or a pathology. Organoid cultures are the 3D cultivation of source tissue (ranging from cells to tissue fragments) in a support matrix and specialized media that nearly resembles the physiological environment. Depending on the source tissue, growth factors, and inhibitors provided, organoids can be programmed to recapitulate the biology of a system and progression of pathology. Organoids are genetically stable, and genetically amenable, making them very suitable tools to study tissue homeostasis and cancer. In this Review, we focus on providing recent technical advances from published literature to efficiently use organoids as a tool for disease modeling and therapeutics. Also, we discuss stem cell biology principles used to generate multiple organoids and their characteristics, with a brief description of methodology. A major theme of this review is to expand organoid applications to the study disease progression and drug response in different cancers. We also discuss shortcomings, limitations, and advantages of developed 3D cultures, with the rationale behind the methodology. Stem Cells 2018;36:1329-1340.

Clonal dynamics studied in cultured induced pluripotent stem cells reveal major growth imbalances within a few weeks

Background

Human induced pluripotent stem (iPS) cells have revolutionised research and spark hopes for future tissue replacement therapies. To obtain high cell numbers, iPS cells can be expanded indefinitely. However, as long-term expansion can compromise cell integrity and quality, we set out to assess potential reduction of clonal diversity by inherent growth imbalances.

Methods

Using red, green, blue marking as a lentiviral multi-colour clonal cell tracking technology, we marked three different iPS cell lines as well as three other cell lines, assigning a unique fluorescent colour to each cell at one point in culture. Subsequently, we followed the sub-clonal distribution over time by flow cytometry and fluorescence microscopy analysis in regular intervals.

Results

In three human iPS cell lines as well as primary human fibroblasts and two widely used human cell lines as controls (K562 and HEK 293 T), we observed a marked reduction in sub-clonal diversity over time of culture (weeks). After 38 passages, all iPS cultures consisted of less than 10 residual clones. Karyotype and function, the latter assessed by cardiomyocyte differentiation and tissue engineering, did not reveal obvious differences.

Conclusions

Our results argue for a quick selection of sub-clones with a growth advantage and flag a normally invisible and potentially undesired behaviour of cultured iPS cells, especially when using long-term cultured iPS cells for experiments or even in-vivo applications.

Electronic supplementary material

The online version of this article (10.1186/s13287-018-0893-2) contains supplementary material, which is available to authorized users.

Preparation of Amyloid Fibril Networks

Networks of amyloid nanofibrils fabricated from common globular proteins such as lysozyme and β-lactoglobulin have material properties that mimic the extracellular microenvironment of many cell types. Cells cultured on such amyloid fibril networks show improved attachment, spreading and in the case of mesenchymal stem cells improved differentiation. Here we describe a detailed protocol for fabricating amyloid fibril networks suitable for eukaryotic cell culture applications.

Isolation of Human Photoreceptor Precursors via a Cell Surface Marker Panel from Stem Cell-Derived Retinal Organoids and Fetal Retinae

Loss of photoreceptor cells due to retinal degeneration is one of the main causes of blindness in the developed world. Although there is currently no effective treatment, cell replacement therapy using stem‐cell‐derived photoreceptor cells may be a feasible future treatment option. In order to ensure safety and efficacy of this approach, robust cell isolation and purification protocols must be developed. To this end, we previously developed a biomarker panel for the isolation of mouse photoreceptor precursors from the developing mouse retina and mouse embryonic stem cell cultures. In the current study we applied this approach to the human pluripotent stem cell (hPSC) system, and identified novel biomarker combinations that can be leveraged for the isolation of human photoreceptors. Human retinal samples and hPSC‐derived retinal organoid cultures were screened against 242 human monoclonal antibodies using a high through‐put flow cytometry approach. We identified 46 biomarkers with significant expression levels in the human retina and hPSC differentiation cultures. Human retinal cell samples, either from fetal tissue or derived from embryonic and induced pluripotent stem cell cultures, were fluorescence‐activated cell sorted (FACS) using selected candidate biomarkers that showed expression in discrete cell populations. Enrichment for photoreceptors and exclusion of mitotically active cells was demonstrated by immunocytochemical analysis with photoreceptor‐specific antibodies and Ki‐67. We established a biomarker combination, which enables the robust purification of viable human photoreceptors from both human retinae and hPSC‐derived organoid cultures. Stem Cells2018;36:709–722

Re-using blood products as an alternative supplement in the optimisation of clinical-grade adipose-derived mesenchymal stem cell culture

Objectives

Adipose-derived mesenchymal stem cells (ADMSCs) are a promising strategy for orthopaedic applications, particularly in bone repair. Ex vivo expansion of ADMSCs is required to obtain sufficient cell numbers. Xenogenic supplements should be avoided in order to minimise the risk of infections and immunological reactions. Human platelet lysate and human plasma may be an excellent material source for ADMSC expansion. In the present study, use of blood products after their recommended transfusion date to prepare human platelet lysate (HPL) and human plasma (Hplasma) was evaluated for in vitro culture expansion and osteogenesis of ADMSCs.

Methods

Human ADMSCs were cultured in medium supplemented with HPL, Hplasma and a combination of HPL and Hplasma (HPL+Hplasma). Characteristics of these ADMSCs, including osteogenesis, were evaluated in comparison with those cultured in fetal bovine serum (FBS).

Results

HPL and HPL+Hplasma had a significantly greater growth-promoting effect than FBS, while Hplasma exhibited a similar growth-promoting effect to that of FBS. ADMSCs cultured in HPL and/or Hplasma generated more colony-forming unit fibroblasts (CFU-F) than those cultured in FBS. After long-term culture, ADMSCs cultured in HPL and/or Hplasma showed reduced cellular senescence, retained typical cell phenotypes, and retained differentiation capacities into osteogenic and adipogenic lineages.

Conclusion

HPL and Hplasma prepared from blood products after their recommended transfusion date can be used as an alternative and effective source for large-scale ex vivo expansion of ADMSCs.

Cite this article: J. Phetfong, T. Tawonsawatruk, K. Seenprachawong, A. Srisarin, C. Isarankura-Na-Ayudhya, A. Supokawej. Re-using blood products as an alternative supplement in the optimisation of clinical-grade adipose-derived mesenchymal stem cell culture. Bone Joint Res 2017;6:414–422. DOI: 10.1302/2046-3758.67.BJR-2016-0342.R1.

Isolation, culture and analysis of adult subependymal neural stem cells

Individual cells dissected from the subependymal neurogenic niche of the adult mouse brain proliferate in medium containing basic fibroblast growth factor (bFGF) and/or epidermal growth factor (EGF) as mitogens, to produce multipotent clonal aggregates called neurospheres. These cultures constitute a powerful tool for the study of neural stem cells (NSCs) provided that they allow the analysis of their features and potential capacity in a controlled environment that can be modulated and monitored more accurately than in vivo. Clonogenic and population analyses under mitogen addition or withdrawal allow the quantification of the self-renewing and multilineage potency of these cells and the identification of the mechanisms involved in these properties. Here, we describe a set of procedures developed and/or modified by our group including several experimental options that can be used either independently or in combination for the ex vivo assessment of cell properties of NSCs obtained from the adult subependymal niche.

Isolation and Colony Formation of Murine Bone and Bone Marrow Cells

Adult homeostasis is dependent on normal Wt1 expression. Loss of Wt1 expression in adult mice causes rapid loss of the mesenchymal tissues, fat and bone, amongst other phenotypes. Bone and bone marrow mesenchymal stromal cells can be studied by cell isolation and expansion. The stemness of these cells can then be characterized by carrying out a colony-forming unit-fibroblast assay and observing clonogenic capabilities.

Concise Review: Understanding the Renal Progenitor Cell Niche In Vivo to Recapitulate Nephrogenesis In Vitro

Chronic kidney disease (CKD), defined as progressive kidney damage and a reduction of the glomerular filtration rate, can progress to end-stage renal failure (CKD5), in which kidney function is completely lost. CKD5 requires dialysis or kidney transplantation, which is limited by the shortage of donor organs. The incidence of CKD5 is increasing annually in the Western world, stimulating an urgent need for new therapies to repair injured kidneys. Many efforts are directed toward regenerative medicine, in particular using stem cells to replace nephrons lost during progression to CKD5. In the present review, we provide an overview of the native nephrogenic niche, describing the complex signals that allow survival and maintenance of undifferentiated renal stem/progenitor cells and the stimuli that promote differentiation. Recapitulating in vitro what normally happens in vivo will be beneficial to guide amplification and direct differentiation of stem cells toward functional renal cells for nephron regeneration.

SIGNIFICANCE

Kidneys perform a plethora of functions essential for life. When their main effector, the nephron, is irreversibly compromised, the only therapeutic choices available are artificial replacement (dialysis) or renal transplantation. Research focusing on alternative treatments includes the use of stem cells. These are immature cells with the potential to mature into renal cells, which could be used to regenerate the kidney. To achieve this aim, many problems must be overcome, such as where to take these cells from, how to obtain enough cells to deliver to patients, and, finally, how to mature stem cells into the cell types normally present in the kidney. In the present report, these questions are discussed. By knowing the factors directing the proliferation and differentiation of renal stem cells normally present in developing kidney, this knowledge can applied to other types of stem cells in the laboratory and use them in the clinic as therapy for the kidney.

Development of a Monitoring Method for Nonlabeled Human Pluripotent Stem Cell Growth by Time-Lapse Image Analysis

: Cell growth is an important criterion for determining healthy cell conditions. When somatic cells or cancer cells are dissociated into single cells for passaging, the cell numbers can be counted at each passage, providing information on cell growth as an indicator of the health conditions of these cells. In the case of human pluripotent stem cells (hPSCs), because the cells are usually dissociated into cell clumps of ∼50-100 cells for passaging, cell counting is time-consuming. In the present study, using a time-lapse imaging system, we developed a method to determine the growth of hPSCs from nonlabeled live cell phase-contrast images without damaging these cells. Next, the hPSC colony areas and number of nuclei were determined and used to derive equations to calculate the cell number in hPSC colonies, which were assessed on time-lapse images acquired using a culture observation system. The relationships between the colony areas and nuclei numbers were linear, although the equation coefficients were dependent on the cell line used, colony size, colony morphology, and culture conditions. When the culture conditions became improper, the change in cell growth conditions could be detected by analysis of the phase-contrast images. This method provided real-time information on colony growth and cell growth rates without using treatments that can damage cells and could be useful for basic research on hPSCs and cell processing for hPSC-based therapy.

SIGNIFICANCE

This is the first study to use a noninvasive method using images to systemically determine the growth of human pluripotent stem cells (hPSCs) without damaging or wasting cells. This method would be useful for quality control during cell culture of clinical hPSCs.

Mesenchymal Stem Cells Derived from Human Adipose Tissue

Human adult mesenchymal stem cells are present in fat tissue, which can be obtained using surgical procedures such as liposuction. The multilineage capacity of mesenchymal stem cells makes them very valuable for cell-based medical therapies. In this chapter, we describe how to isolate mesenchymal stem cells from human adult fat tissue, propagate the cells in culture, and cryopreserve the cells for tissue engineering applications. Flow cytometry methods are also described for identification and characterization of adipose-derived stem cells and for cell sorting.

Adult stem cells in the small intestine are intrinsically programmed with their location-specific function

Differentiation and specialization of epithelial cells in the small intestine are regulated in two ways. First, there is differentiation along the crypt-villus axis of the intestinal stem cells into absorptive enterocytes, Paneth, goblet, tuft, enteroendocrine, or M cells, which is mainly regulated by WNT. Second, there is specialization along the cephalocaudal axis with different absorptive and digestive functions in duodenum, jejunum, and ileum that is controlled by several transcription factors such as GATA4. However, so far it is unknown whether location-specific functional properties are intrinsically programmed within stem cells or if continuous signaling from mesenchymal cells is necessary to maintain the location-specific identity of the small intestine. Using the pure epithelial organoid technique, we show that region-specific gene expression profiles are conserved throughout long-term cultures of both mouse and human intestinal stem cells and correlated with differential Gata4 expression. Furthermore, the human organoid culture system demonstrates that Gata4-regulated gene expression is only allowed in absence of WNT signaling. These data show that location-specific function is intrinsically programmed in the adult stem cells of the small intestine and that their differentiation fate is independent of location-specific extracellular signals. In light of the potential future clinical application of small intestine-derived organoids, our data imply that it is important to generate GATA4-positive and GATA4-negative cultures to regenerate all essential functions of the small intestine.

Concise review: animal substance-free human embryonic stem cells aiming at clinical applications

Human embryonic stem cells have been considered the gold standard as a cell source for regenerative medicine since they were first cultured in 1998. They are pluripotent and can form principally all the cells types in the body. They are obtained from supernumerary human in vitro fertilization embryos that cannot be used for infertility treatment. Following studies on factors regulating pluripotency and differentiation, we now have techniques to establish and effectively expand these cells in animal substance-free conditions, even from single cells biopsied from eight-cell stage embryos in chemically defined feeder-free cultures. The genetic stability and absence of tumorigenic mutations can be determined. There are satisfactory animal tests for functionality and safety. The first clinical trials are ongoing for two indications: age-related macular degeneration and spinal cord injury.

Measuring dissolved oxygen to track erythroid differentiation of hematopoietic progenitor cells in culture

As stem cell technologies move from the developmental to the commercial stage strategies must be developed to monitor culture operations. These will ensure consistency of differentiation programs and maintenance of optimum cell viability during production runs. Due to the sensitivity of stem cells to their environment, and their variability in response to external stimuli, accurate monitoring of in vitro conditions will be crucial for effective large-scale culturing of therapeutic stem cells. Here we describe a simple method to monitor the expansion and maturation of adult human haematopoietic stem/progenitor cells into red blood cells in vitro by measuring the oxygen consumption rate of cultures. Cell cultures followed a characteristic pattern of oxygen consumption that is reflective of in vivo erythroid maturation. This method could be easily developed as an online system to map erythroid differentiation and maturation of cultured cells as effectively as the more time consuming process of flow cytometric analysis of surface marker expression patterns.

Mouse embryonic stem cells established in physiological-glucose media express the high KM Glut2 glucose transporter expressed by normal embryos

Glut2 is one of the facilitative glucose transporters expressed by preimplantation and early postimplantation embryos. Glut2 is important for survival before embryonic day 10.5. The Glut2 KM (∼16 mmol/liter) is significantly higher than physiologic glucose concentrations (∼5.5 mmol/liter), suggesting that Glut2 normally performs some essential function other than glucose transport. Nevertheless, Glut2 efficiently transports glucose when extracellular glucose concentrations are above the Glut2 KM. Media containing 25 mmol/liter glucose are widely used to establish and propagate embryonic stem cells (ESCs). Glut2-mediated glucose uptake by embryos induces oxidative stress and can cause embryo cell death. Here we tested the hypothesis that low-glucose embryonic stem cells (LG-ESCs) isolated in physiological-glucose (5.5 mmol/liter) media express a functional Glut2 glucose transporter. LG-ESCs were compared with conventional D3 ESCs that had been cultured only in high-glucose media. LG-ESCs expressed Glut2 mRNA and protein at much higher levels than D3 ESCs, and 2-deoxyglucose transport by LG-ESCs, but not D3 ESCs, exhibited high Michaelis-Menten kinetics. Glucose at 25 mmol/liter induced oxidative stress in LG-ESCs and inhibited expression of Pax3, an embryo gene that is inhibited by hyperglycemia, in neuronal precursors derived from LG-ESCs. These effects were not observed in D3 ESCs. These findings demonstrate that ESCs isolated in physiological-glucose media retain a functional Glut2 transporter that is expressed by embryos. These cells are better suited to the study of metabolic regulation characteristic of the early embryo and may be advantageous for therapeutic applications.

Decellularized feeders: an optimized method for culturing pluripotent cells

Pluripotent cells such as human embryonic stem cells and human induced pluripotent stem cells are useful in the field of regenerative medicine because they can proliferate indefinitely and differentiate into all cell types. However, a limiting factor for maintaining and propagating stem cells is the need for inactivated fibroblasts as a growth matrix, since these may potentially cause cross-contamination. In this study, we aimed to maintain stem cells on the extracellular matrix (ECM) of either nonirradiated or γ-irradiated fibroblasts. It has been demonstrated that the ECM contains factors and proteins vital for the adhesion, proliferation, and differentiation of pluripotent cells. In order to preserve the ECM, the cell layers of the fibroblasts were decellularized by treatment with 0.05% sodium dodecyl sulfate (SDS), which resulted in an absence of DNA as compared with conventional feeder culture. However, SDS treatment did not cause a detectable change in the ECM architecture and integrity. Furthermore, immunohistochemistry demonstrated that expressions of major ECM proteins, such as fibronectin, collagen, and laminin, remained unaltered. The human pluripotent cells cultured on this decellularized matrix maintained gene expression of the pluripotency markers NANOG and OCT4 and had the potency to differentiate to three germ layers. The in vitro culture system shown here has an excellent potential since the main allogeneic components (i.e., DNA of the feeder cells) are removed. It is also a technically easy, fast, safe, and cheap method for maintaining a refined feeder-free stem cell culture for further cell differentiation studies.

Concise review: guidance in developing commercializable autologous/patient-specific cell therapy manufacturing

Cell therapy is poised to play an enormous role in regenerative medicine. However, little guidance is being made available to academic and industrial entities in the start-up phase. In this technical review, members of the International Society for Cell Therapy provide guidance in developing commercializable autologous and patient-specific manufacturing strategies from the perspective of process development. Special emphasis is placed on providing guidance to small academic or biotech researchers as to what simple questions can be addressed or answered at the bench in order to make their cell therapy products more feasible for commercial-scale production. We discuss the processes that are required for scale-out at the manufacturing level, and how many questions can be addressed at the bench level. The goal of this review is to provide guidance in the form of topics that can be addressed early in the process of development to better the chances of the product being successful for future commercialization.

Delivery of differentiation factors by mesoporous silica particles assists advanced differentiation of transplanted murine embryonic stem cells

Stem cell transplantation holds great hope for the replacement of damaged cells in the nervous system. However, poor long-term survival after transplantation and insufficiently robust differentiation of stem cells into specialized cell types in vivo remain major obstacles for clinical application. Here, we report the development of a novel technological approach for the local delivery of exogenous trophic factor mimetics to transplanted cells using specifically designed silica nanoporous particles. We demonstrated that delivering Cintrofin and Gliafin, established peptide mimetics of the ciliary neurotrophic factor and glial cell line-derived neurotrophic factor, respectively, with these particles enabled not only robust functional differentiation of motor neurons from transplanted embryonic stem cells but also their long-term survival in vivo. We propose that the delivery of growth factors by mesoporous nanoparticles is a potentially versatile and widely applicable strategy for efficient differentiation and functional integration of stem cell derivatives upon transplantation.

Long-term maintenance of limbal epithelial progenitor cells using rho kinase inhibitor and keratinocyte growth factor

Corneal epithelial stem cells are located in the limbus, the junction between the cornea and the conjunctiva. A limbal epithelium model in vitro would be useful for the study of epithelial stem cells, as well as improving the quality of cultivated epithelial sheets for the treatment of limbal stem cell deficiency. In this study, we succeeded in constructing a limbal epithelium-like structure that could be maintained for at least 5 months in vitro. We modified conventional medium by replacing epidermal growth factor with keratinocyte growth factor (KGF) and adding Y-27632, a rho kinase inhibitor. Using this medium, epithelial cells freshly isolated from human limbus were cocultured with human mesenchymal stem cell-derived feeder cells. Cells formed a stratified layer without air exposure, and both basal and suprabasal layers maintained their unique morphologies for up to 5 months. Basal layers expressed the progenitor marker p63 uniformly and K15 heterogeneously. Expressions of PAX6, K3, and K12 indicated that cell sheets underwent normal differentiation in the corneal epithelium lineage. Although medium was changed daily after day 7, cell debris was observed every day, suggesting that cell sheets underwent turnover. Furthermore, secondary colonies were observed from cells dissociated from 1-month and 3-month cultured sheets. In conclusion, human limbal epithelial cell sheet cultures with KGF and Y-27632 maintained stratification, high expression of both stem/progenitor markers and differentiation markers, and colony-forming cells long-term. This protocol may be useful as an in vitro limbal epithelial model for basic studies.

A novel combinatorial therapy with pulp stem cells and granulocyte colony-stimulating factor for total pulp regeneration

Treatment of deep caries with pulpitis is a major challenge in dentistry. Stem cell therapy represents a potential strategy to regenerate the dentin-pulp complex, enabling conservation and restoration of teeth. The objective of this study was to assess the efficacy and safety of pulp stem cell transplantation as a prelude for the impending clinical trials. Clinical-grade pulp stem cells were isolated and expanded according to good manufacturing practice conditions. The absence of contamination, abnormalities/aberrations in karyotype, and tumor formation after transplantation in an immunodeficient mouse ensured excellent quality control. After autologous transplantation of pulp stem cells with granulocyte-colony stimulating factor (G-CSF) in a dog pulpectomized tooth, regenerated pulp tissue including vasculature and innervation completely filled in the root canal, and regenerated dentin was formed in the coronal part and prevented microleakage up to day 180. Transplantation of pulp stem cells with G-CSF yielded a significantly larger amount of regenerated dentin-pulp complex compared with transplantation of G-CSF or stem cells alone. Also noteworthy was the reduction in the number of inflammatory cells and apoptotic cells and the significant increase in neurite outgrowth compared with results without G-CSF. The transplanted stem cells expressed angiogenic/neurotrophic factors. It is significant that G-CSF together with conditioned medium of pulp stem cells stimulated cell migration and neurite outgrowth, prevented cell death, and promoted immunosuppression in vitro. Furthermore, there was no evidence of toxicity or adverse events. In conclusion, the combinatorial trophic effects of pulp stem cells and G-CSF are of immediate utility for pulp/dentin regeneration, demonstrating the prerequisites of safety and efficacy critical for clinical applications.