Potential of embryonic and adult stem cells in vitro

Study on the mechanism of quercetin inducing mesenchymal stem cells to differentiate into fibroblasts through TGF-β1 and IGF-1

BACKGROUND

Stem cell differentiation has opened up new avenues for disease treatment, tissue repair, and drug development in the study of regenerative medicine, and has huge application prospects. This study aimed to explore the mechanism of quercetin on the differentiation of mesenchymal stem cells (MSCs) into fibroblasts.

METHODS

In this study, cell differentiation experiments and flow cytometry were used to detect the successful isolation of bone marrow MSCs from SD rats. Quercetin at 5, 10, and 20 μM was used as low, medium, and high doses to intervene in MSCs. The cell viability changes of ligament fibroblasts at 24, 48, and 72 hours after quercetin treatment were detected using a CCK-8 cell counting kit. Cell proliferative capacity was determined by flow cytometry. RT-qPCR measured the relative expression levels of TGF-β1, IGF-1, COL-Ⅰ, COL-Ⅲ, FN (fibronectin), and TNMD (Tenomodulin) in different experimental groups. Molecular docking experiments were conducted to explore the binding effect of quercetin on TGF-β1 and IGF-1 proteins.

RESULTS

Flow cytometry verified the successful isolation of MSCs, which had high expression of CD29 and CD73, while lower expression of CD90 and CD45. Experimental results show that low and medium doses of quercetin can enhance cell proliferation, while high doses have no significant effect on cells. Detection of cell proliferation through flow cytometry yielded similar results to CCK-8. Transwell experiments have shown that low and medium doses of quercetin can increase cell migration ability. In addition, RT-qPCR detection showed that quercetin can increase the mRNA expression of TGF-β1 and IGF-1, and promote the expression of COL-Ⅰ, COL-Ⅲ, FN, and TNMD genes in ligament fibroblasts. Molecular docking results showed that quercetin can bind firmly to TGF-β1 and IGF-1.

CONCLUSION

Overall, this study revealed the morphological characteristics and identification of MSCs, as well as the regulatory mechanism of quercetin on the behavior of ligament fibroblasts. Quercetin affects the proliferation and gene expression of ligament fibroblasts by regulating the expression of TGF-β1 and IGF-1, which may provide a new perspective for biomedical research on the skeletal system.

The Role of Mesenchymal Stem Cell Secretome (Extracellular Microvesicles and Exosomes) in Animals' Musculoskeletal and Neurologic-Related Disorders

The advances in regenerative medicine are very important for the development of medicine and the discovery of stem cells has shown a greater capacity to raise the level of therapeutic quality while their use becomes more accessible, especially in their mesenchymal form. In veterinary medicine, it is not different. The use of those cells, as well as recent advances related to the use of their extracellular vesicles, demonstrates a great opportunity to enhance therapeutic methods and ensure more life quality for patients, which can be in clinical or surgical treatments. Knowing the advances in these modalities and the growing clinical and surgery research and demands for innovations in orthopedic and neurology medicines, this paper aimed to review the literature about the methodologies of use and applications such as the pathways of action and the advances that were postulated for microvesicles and exosomes derived from mesenchymal stem cells in veterinary medicine, especially for musculoskeletal disorders and related injuries.

Comparison of Differentiation Pattern and WNT/SHH Signaling in Pluripotent Stem Cells Cultured under Different Conditions

Pluripotent stem cells (PSCs) are characterized by the ability to self-renew as well as undergo multidirectional differentiation. Culture conditions have a pivotal influence on differentiation pattern. In the current study, we compared the fate of mouse PSCs using two culture media: (1) chemically defined, free of animal reagents, and (2) standard one relying on the serum supplementation. Moreover, we assessed the influence of selected regulators (WNTs, SHH) on PSC differentiation. We showed that the differentiation pattern of PSCs cultured in both systems differed significantly: cells cultured in chemically defined medium preferentially underwent ectodermal conversion while their endo- and mesodermal differentiation was limited, contrary to cells cultured in serum-supplemented medium. More efficient ectodermal differentiation of PSCs cultured in chemically defined medium correlated with higher activity of SHH pathway while endodermal and mesodermal conversion of cells cultured in serum-supplemented medium with higher activity of WNT/JNK pathway. However, inhibition of either canonical or noncanonical WNT pathway resulted in the limitation of endo- and mesodermal conversion of PSCs. In addition, blocking WNT secretion led to the inhibition of PSC mesodermal differentiation, confirming the pivotal role of WNT signaling in this process. In contrast, SHH turned out to be an inducer of PSC ectodermal, not mesodermal differentiation.

Conditional reprogramming: next generation cell culture

Long-term primary culture of mammalian cells has been always difficult due to unavoidable senescence. Conventional methods for generating immortalized cell lines usually require manipulation of genome which leads to change of important biological and genetic characteristics. Recently, conditional reprogramming (CR) emerges as a novel next generation tool for long-term culture of primary epithelium cells derived from almost all origins without alteration of genetic background of primary cells. CR co-cultures primary cells with inactivated mouse 3T3-J2 fibroblasts in the presence of RHO-related protein kinase (ROCK) inhibitor Y-27632, enabling primary cells to acquire stem-like characteristics while retain their ability to fully differentiate. With only a few years' development, CR shows broad prospects in applications in varied areas including disease modeling, regenerative medicine, drug evaluation, drug discovery as well as precision medicine. This review is thus to comprehensively summarize and assess current progress in understanding mechanism of CR and its wide applications, highlighting the value of CR in both basic and translational researches and discussing the challenges faced with CR.

Differentiation Potential and Tumorigenic Risk of Rat Bone Marrow Stem Cells Are Affected By Long-Term In Vitro Expansion

Objective:

Mesenchymal stem cells (MSCs) have the capacity for extensive expansion and adipogenic, osteogenic, chondrogenic, myogenic, and neural differentiation in vitro. The aim of our study was to determine stemness, differentiation potential, telomerase activity, and ultrastructural characteristics of long-term cultured rat bone marrow (rBM)-MSCs.

Materials and Methods:

rBM-MSCs from passages 3, 50, and 100 (P3, P50, and P100) were evaluated through immunocytochemistry, reverse transcription-polymerase chain reaction, telomerase activity assays, and electron microscopy.

Results:

A dramatic reduction in the levels of myogenic markers actin and myogenin was detected in P100. Osteogenic markers Coll1, osteonectin (Sparc), and osteocalcin as well as neural marker c-Fos and chondrogenic marker Coll2 were significantly reduced in P100 compared to P3 and P50. Osteogenic marker bone morphogenic protein-2 (BMP2) and adipogenic marker peroxisome proliferator-activated receptor gamma (Pparγ) expression was reduced in late passages. The expression of stemness factor Rex-1 was lower in P100, whereas Oct4 expression was decreased in P50 compared to P3 and P100. Increased telomerase activity was observed in long-term cultured cells, signifying tumorigenic risk. Electron microscopic evaluations revealed ultrastructural changes such as smaller number of organelles and increased amount of autophagic vacuoles in the cytoplasm in long-term cultured rBM-MSCs.

Conclusion:

This study suggests that long-term culture of rBM-MSCs leads to changes in differentiation potential and increased tumorigenic risk.

Comparative capability of menstrual blood versus bone marrow derived stem cells in neural differentiation

In order to characterize the potency of menstrual blood stem cells (MenSCs) for future cell therapy of neurological disorders instead of bone marrow stem cells (BMSCs) as a well-known and conventional source of adult stem cells, we examined the in vitro differentiation potential of these stem cells into neural-like cells. The differentiation potential of MenSCs to neural cells in comparison with BMSCs was assessed under two step neural differentiation including conversion to neurosphere-like cells and final differentiation. The expression levels of Nestin, Microtubule-associated protein 2, gamma-aminobutyric acid type B receptor subunit 1 and 2, and Tubulin, beta 3 class III mRNA and/or protein were up-regulated during development of MenSCs into neurosphere-like cells (NSCs) and neural-like cells. The up-regulation level of these markers in differentiated neural-like cells from MenSCs was comparable with differentiated cells from BMSCs. Moreover, both differentiated MenSCs and BMSCs expressed high levels of potassium, calcium and sodium channel genes developing functional channels with electrophysiological recording. For the first time, we demonstrated that MenSCs are a unique cell population with differentiation ability into neural-like cells comparable to BMSCs. In addition, we have introduced an approach to generate NSCs from MenSCs and BMSCs and their further differentiation into neural-like cells in vitro. Our results hold a promise to future stem cell therapy of neurological disorders using NSCs derived from menstrual blood, an accessible source in every woman.

Research Advancements in Porcine Derived Mesenchymal Stem Cells

In the present era of stem cell biology, various animals such as Mouse, Bovine, Rabbit and Porcine have been tested for the efficiency of their mesenchymal stem cells (MSCs) before their actual use for stem cell based application in humans. Among them pigs have many similarities to humans in the form of organ size, physiology and their functioning, therefore they have been considered as a valuable model system for in vitro studies and preclinical assessments. Easy assessability, few ethical issues, successful MSC isolation from different origins like bone marrow, skin, umbilical cord blood, Wharton’s jelly, endometrium, amniotic fluid and peripheral blood make porcine a good model for stem cell therapy. Porcine derived MSCs (pMSCs) have shown greater in vitro differentiation and transdifferention potential towards mesenchymal lineages and specialized lineages such as cardiomyocytes, neurons, hepatocytes and pancreatic beta cells. Immunomodulatory and low immunogenic profiles as shown by autologous and heterologous MSCs proves them safe and appropriate models for xenotransplantation purposes. Furthermore, tissue engineered stem cell constructs can be of immense importance in relation to various osteochondral defects which are difficult to treat otherwise. Using pMSCs successful treatment of various disorders like Parkinson’s disease, cardiac ischemia, hepatic failure, has been reported by many studies. Here, in this review we highlight current research findings in the area of porcine mesenchymal stem cells dealing with their isolation methods, differentiation ability, transplantation applications and their therapeutic potential towards various diseases.

Gene Transfection of Human Turbinate Mesenchymal Stromal Cells Derived from Human Inferior Turbinate Tissues

Human turbinate mesenchymal stromal cells (hTMSCs) are novel stem cells derived from nasal inferior turbinate tissues. They are easy to isolate from the donated tissue after turbinectomy or conchotomy. In this study, we applied hTMSCs to a nonviral gene delivery system using polyethyleneimine (PEI) as a gene carrier; furthermore, the cytotoxicity and transfection efficiency of hTMSCs were evaluated to confirm their potential as resources in gene therapy. DNA-PEI nanoparticles (NPs) were generated by adding the PEI solution to DNA and were characterized by a gel electrophoresis and by measuring particle size and surface charge of NPs. The hTMSCs were treated with DNA-PEI NPs for 4 h, and toxicity of NPs to hTMSCs and gene transfection efficiency were monitored using MTT assay, fluorescence images, and flow cytometry after 24 h and 48 h. At a high negative-to-positive charge ratio, DNA-PEI NPs treatment led to cytotoxicity of hTMSCs, but the transfection efficiency of DNA was increased due to the electrostatic effect between the NPs and the membranes of hTMSCs. Importantly, the results of this research verified that PEI could deliver DNA into hTMSCs with high efficiency, suggesting that hTMSCs could be considered as untapped resources for applications in gene therapy.

High Content Analysis of Human Pluripotent Stem Cell Derived Hepatocytes Reveals Drug Induced Steatosis and Phospholipidosis

Hepatotoxicity is one of the most cited reasons for withdrawal of approved drugs from the market. The use of nonclinically relevant in vitro and in vivo testing systems contributes to the high attrition rates. Recent advances in differentiating human induced pluripotent stem cells (hiPSCs) into pure cultures of hepatocyte-like cells expressing functional drug metabolizing enzymes open up possibilities for novel, more relevant human cell based toxicity models. The present study aimed to investigate the use of hiPSC derived hepatocytes for conducting mechanistic toxicity testing by image based high content analysis (HCA). The hiPSC derived hepatocytes were exposed to drugs known to cause hepatotoxicity through steatosis and phospholipidosis, measuring several endpoints representing different mechanisms involved in drug induced hepatotoxicity. The hiPSC derived hepatocytes were benchmarked to the HepG2 cell line and generated robust HCA data with low imprecision between plates and batches. The different parameters measured were detected at subcytotoxic concentrations and the order of which the compounds were categorized (as severe, moderate, mild, or nontoxic) based on the degree of injury at isomolar concentration corresponded to previously published data. Taken together, the present study shows how hiPSC derived hepatocytes can be used as a platform for screening drug induced hepatotoxicity by HCA.

In vitro hepatic trans-differentiation of human mesenchymal stem cells using sera from congestive/ischemic liver during cardiac failure

Cellular therapy for end-stage liver failures using human mesenchymal stem cells (hMSCs)-derived hepatocytes is a potential alternative to liver transplantation. Hepatic trans-differentiation of hMSCs is routinely accomplished by induction with commercially available recombinant growth factors, which is of limited clinical applications. In the present study, we have evaluated the potential of sera from cardiac-failure-associated congestive/ischemic liver patients for hepatic trans-differentiation of hMSCs. Results from such experiments were confirmed through morphological changes and expression of hepatocyte-specific markers at molecular and cellular level. Furthermore, the process of mesenchymal-to-epithelial transition during hepatic trans-differentiation of hMSCs was confirmed by elevated expression of E-Cadherin and down-regulation of Snail. The functionality of hMSCs-derived hepatocytes was validated by various liver function tests such as albumin synthesis, urea release, glycogen accumulation and presence of a drug inducible cytochrome P450 system. Based on these findings, we conclude that sera from congestive/ischemic liver during cardiac failure support a liver specific microenvironment for effective hepatic trans-differentiation of hMSCs in vitro.

MiR-495 suppresses mesendoderm differentiation of mouse embryonic stem cells via the direct targeting of Dnmt3a

Embryonic stem cells (ESCs) are promising resources for clinical therapies due to their potential to generate multiple cell types. The dynamic expression of de novo methyltransferases (Dnmt3a and Dnmt3b) is essential to ESCs; however, the regulatory mechanism of Dnmt3a or Dnmt3b expression in ESCs is still poorly understood. Here, we reported that decreased expression of microRNA-495 (miR-495) in the first 2days of embryoid body (EB) formation was required for mouse embryonic stem cell (mESC) differentiation because repressed mesoderm and endoderm lineages were detected in ectopic miR-495 expression mESCs. This effect was reversed by the function blockade of miR-495. We identified Dnmt3a as a functional target of miR-495 and showed that endogenous miR-495 repressed the expression of Dnmt3a in mESCs. Furthermore, the effect of miR-495 on mESCs could be eliminated by Dnmt3a overexpression. Moreover, miR-495 had no effect on the expression of Dnmt3b despite the findings obtained from previous studies that mainly focused on the common characteristics of the regulatory mechanisms of Dnmt3a and Dnmt3b expression. Thus, our studies not only uncovered a previously uncharacterized function of miR-495 in mESC differentiation but also generated a new idea to explore the mechanisms governing the functional difference between Dnmt3a and Dnmt3b.

Differentiation potential of menstrual blood- versus bone marrow-stem cells into glial-like cells

Menstrual blood is easily accessible, renewable, and inexpensive source of stem cells that have been interested for cell therapy of neurodegenerative diseases. In this study, we showed conversion of menstrual blood stem cells (MenSCs) into clonogenic neurosphere- like cells (NSCs), which can be differentiated into glial-like cells. Moreover, differentiation potential of MenSCs into glial lineage was compared with bone marrow stem cells (BMSCs). Differentiation potential of individual converted NSCs derived from MenSCs or BMSCs into glial-like cells was investigated using immunofluorescence staining and real-time polymerase chain reaction.The fibroblastic morphology of both MenSCs and BMSCs was turned into NSCs shape during first step of differentiation. NSCs derived from both BMSCs and MenSCs expressed higher levels of Olig-2 and Nestin markers compared to undifferentiated cells. The expression levels of myelin basic protein (MBP) mRNA up regulated only in BMSCs-NSCs no in MenSCs-NSCs. However, outgrowth of individual NSCs derived from both MenSCs and BMSCs into glial-like cells led to significant up regulation of glial fibrillary acidic protein,Olig-2 and MBP at mRNA and protein level accompanied with down regulation of Nestin protein.This is the first study demonstrating that MenSCs can be converted to NSCs with differentiation ability into glial-like cells. Accumulative data show different expression pattern of glial markers in differentiated MenSCs compared to BMSCs. The comparable differentiation potential, more accessibility and no invasive technique for sample collection of MenSCs in comparison with BMSCs introduce MenSCs as an apt, consistent and safe alternative to BMSCs for cell therapy of neurodegenerative diseases.

Differential hepatic stem cell proliferation and differentiation after partial hepatectomy in rats

Stem cell‑derived hepatocyte precursor cells represent a promising model for clinical transplantation to diseased livers, as well as for establishment of in vitro systems for drug metabolism and toxicology studies. The present study aimed to establish a new method of induction of hepatocyte differentiation using various factors and evaluate the effect of different partial hepatectomies and the duration of collagenase perfusion on hepatic stem cell proliferation and differentiation. A rat model of hepatic oval cell proliferation was established by partial hepatectomy (PH). Following 73.1 and 83.4% PH, rats underwent perfusion with IV collagenase for 10, 20 and 30 min. Density gradient centrifugation was performed and cells in the supernatant were cultured in various combinations of factors to induce oval cells to differentiate into mature hepatocytes. Cells were characterized for hepatocyte marker expression by morphology, flow cytometry, immunofluorescence and western blot analysis. Hepatic oval cells isolated from rats at 7 and 14 days post‑PH exhibited properties of hepatic stem/progenitor cells. Following culturing in RPMI‑1640 medium with hepatocyte growth factor and fibroblast growth factor‑4, the cells resembled primary human hepatocytes with regard to morphology and expression of the hepatocyte markers, cytokeratin 18 (CK‑18) and α‑1‑fetoprotein (AFP). Optimal differentiation of hepatic stem cells to CK‑18‑ and AFP‑positive cells was observed when stem cells isolated from 83.4% PH rats (7 days following surgery) were perfused with IV collagenase for 20 min. The results of this study provide novel insights into characteristics of rat hepatic stem cells.

Thinking outside the liver: induced pluripotent stem cells for hepatic applications

The discovery of induced pluripotent stem cells (iPSCs) unraveled a mystery in stem cell research, after identification of four re-programming factors for generating pluripotent stem cells without the need of embryos. This breakthrough in generating iPSCs from somatic cells has overcome the ethical issues and immune rejection involved in the use of human embryonic stem cells. Hence, iPSCs form a great potential source for developing disease models, drug toxicity screening and cell-based therapies. These cells have the potential to differentiate into desired cell types, including hepatocytes, under in vitro as well as under in vivo conditions given the proper microenvironment. iPSC-derived hepatocytes could be useful as an unlimited source, which can be utilized in disease modeling, drug toxicity testing and producing autologous cell therapies that would avoid immune rejection and enable correction of gene defects prior to cell transplantation. In this review, we discuss the induction methods, role of reprogramming factors, and characterization of iPSCs, along with hepatocyte differentiation from iPSCs and potential applications. Further, we discuss the location and detection of liver stem cells and their role in liver regeneration. Although tumor formation and genetic mutations are a cause of concern, iPSCs still form a promising source for clinical applications.

Expansion and differentiation of germline-derived pluripotent stem cells on biomaterials

Stem cells with broad differentiation potential, such as the recently described germline-derived pluripotent stem cells (gPS cells), are an appealing source for tissue engineering strategies. Biomaterials can inhibit, support, or induce proliferation and differentiation of stem cells. Here we identified (1) polymers that maintain self-renewal and differentiation potential of gPS cells for feeder-free expansion and (2) polymers supporting the cardiomyogenic fate of gPS cells by analyzing a panel of polymers of an established biomaterial bank previously used to assess growth of diverse stem cell types. Identification of cytocompatible gPS cell/biomaterial combinations required analysis of several parameters, including morphology, viability, cytotoxicity, apoptosis, proliferation, and differentiation potential. Pluripotency of gPS cells was visualized by the endogenous Oct4-promoter-driven GFP and by Sox2 and Nanog immunofluorescence. Viability assay, proliferation assay, and flow cytometry showed that gPS cells efficiently adhere and are viable on synthetic polymers, such as Resomer(®) LR704 (poly(L-lactic-D,L-lactic acid), poly(tetrafluor ethylene) (PTFE), poly(vinylidene fluoride) (PVDF), and on gelatine-coated tissue culture polystyrene. Expansion experiments showed that Resomer LR704 is an alternative substrate for feeder-free gPS cell maintenance. Resomer LR704, PTFE, and PVDF were found to be suitable for gPS cell differentiation. Spontaneous beating in embryoid bodies cultured on Resomer LR704 occurred already on day 8 of differentiation, much earlier compared to the other surfaces. This indicates that Resomer LR704 supports spontaneous cardiomyogenic differentiation of gPS cells, which was also confirmed on molecular, protein and functional level.

Stem-cell niche based comparative analysis of chemical and nano-mechanical material properties impacting ex vivo expansion and differentiation of hematopoietic and mesenchymal stem cells

The ability of stem cells to self-renew with minimal or no differentiation and, when appropriately cued, to give rise to many types of progenitor and mature cells, is the basis for applications in regenerative and transfusion medicine, but also in drug discovery and in vitro toxicology. Inspired by the complex interactions between stem cells and their microenvironment, the so-called stem-cell niche, the properties of supporting biomaterials, including surface biochemistry, topography (type, size, organization, and geometry of nanostructures), and mechanical properties, have been identified as important determinants of stem-cell fate in vitro. 3D culture environments that could recapitulate the complexity of the in vivo stem-cell microenvironment could further expand the complexity and repertoire of engineered environments with exciting translational applications. Herein, the material aspects that affect the expansion and differentiation fate of adult hematopoietic stem/progenitor cells (HSPCs) and mesenchymal stem cells (MSCs), two powerful cell types that co-reside in the bone-marrow niche, but with distinct, sometime complementary, differentiation fates, properties, and translational applications, are examined. Although MSCs are adherent cells and, in contrast, HSPCs are non- or weakly adherent cells, both can sense and respond to material properties, including surface (bio)chemistry, ECM composition, topography, and matrix elasticity, possibly through similar molecular mechanisms.

Chitosan-based hydrogels to induce neuronal differentiation of rat muscle-derived stem cells

In this study, we used a chitosan hydrogel as a 3-dimensional substrate for the attachment, proliferation, and differentiation of rat muscle-derived stem cells (rMDSCs) in the presence of valproic acid (VA). Chitosan solutions containing glycerol phosphate disodium salt form a hydrogel at body temperature. The chitosan hydrogel exhibited a porous 3-dimensional network that allowed the culture medium to penetrate. The chitosan hydrogel acted as a suitable biocompatible substrate for the attachment and proliferation of rMDSCs. On chitosan hydrogel in the presence of VA, rMDSCs exhibited higher expression of the neural markers, neuron-specific enolase (NSE) and beta tubulin III (Tuj-1), the oligodendrocyte marker, oligodendrocyte transcription factor 2 (Olig-2), and the astrocyte marker, glial fibrillary acidic protein (GFAP) than those in the absence of VA. Our results suggest that rMDSCs on a chitosan hydrogel in the presence of VA can differentiate into cells with a neural-like phenotype.

Isolation of insulin-producing cells from different populations of multipotent stromal cells of the umbilical cord and human adipose tissue

Stromal cells of adipose tissue and human umbilical cord were isolated by the original method from general populations of multipotent subpopulation of multipotent stromal cells exhibiting perivascular phenotype (CD146+, CD31-). Effective directed differentiation of these cells into insulin-producing cells by transient transfection of the gene Pdx1 was demonstrated. Transfection multipotent stromal cells CD146-, CD31- derived from adipose tissue and umbilical cord and isolated by the standard method, did not result in activation of insulin gene transcription. It was shown that the expression of nestin was not necessary for effective pancreatic cell differentiation.

Variation of telomerase activity and morphology in porcine mesenchymal stem cells and fibroblasts during prolonged in vitro culture

The purpose of this study was to examine the telomerase activity, population doubling time (PDT), morphological alterations, and the cell cycle status with activity of senescence-associated-ß-galactosidase in porcine mesenchymal stem cells (MSCs) and fibroblasts during an extended in vitro culture. MSCs and fibroblasts were isolated from bone marrow and ear skin of a miniature pig, respectively, and cultured up to 20 passages. The analysis was carried out in MSCs and fibroblasts at 1, 5, 10, 15, and 20 passages. Relative telomerase activity (RTA) levels were significantly (P < 0.05) higher in MSCs than in fibroblasts at all the passages. The PDT and cellular size slightly increased in MSCs at later passages. In contrast, fibroblasts had significantly (P < 0.05) increased PDT and cellular size, and the morphology revealed senescent-like abnormal type after passage 10. Further, the high incidence of ß-galactosidase stained cells was observed in fibroblasts compared to that of MSCs at passage 15, and cell cycle stage at G0 / G1 phase was significantly (P < 0.05) increased in the fibroblasts at 15 and 20 passages compared to that of MSCs. Based on these observations, we concluded that porcine MSCs possessed more tolerance against senescence and aging compared to fibroblasts following prolonged in vitro culture.

Mouse and human pluripotent stem cells and the means of their myogenic differentiation

Pluripotent stem cells, such as embryonic stem cells and induced pluripotent stem cells, are an important tool in the studies focusing at the differentiation of various cell types, including skeletal myoblasts. They are also considered as a source of the cells that due to their pluripotent character and availability could be turned into any required tissue and then used in future in regenerative medicine. However, the methods of the derivation of some of cell types from pluripotent cells still need to be perfected. This chapter summarizes the history and current advancements in the derivation and testing of pluripotent stem cells-derived skeletal myoblasts. It focuses at the in vitro methods allowing the differentiation of stem cells grown in monolayer or propagated as embryoid bodies, and also at in vivo tests allowing the verification of the functionality of obtained skeletal myoblasts.

Induced pluripotent stem cells and personalized medicine: current progress and future perspectives

Generation of induced pluripotent stem cells (iPSCs) has revolutionized the field of regenerative medicine by providing researchers with a unique tool to derive disease-specific stem cells for study. iPSCs can self-renew and can differentiate into many cell types, offering a potentially unlimited source of cells for targeted differentiation into somatic effector cells. Hence, iPSCs are likely to be invaluable for therapeutic applications and disease-related research. In this review, we summarize the recent progress of iPSC generation that has been made with an emphasis on both basic and clinical applications including disease modeling, drug toxicity screening/drug discovery and cell replacement therapy.

In vivo liver regeneration potential of human induced pluripotent stem cells from diverse origins

Human induced pluripotent stem cells (iPSCs) are a potential source of hepatocytes for liver transplantation to treat end-stage liver disease. In vitro differentiation of human iPSCs into hepatic cells has been achieved using a multistage differentiation protocol, but whether these cells are functional and capable of engrafting and regenerating diseased liver tissue is not clear. We show that human iPSC-derived hepatic cells at various differentiation stages can engraft the liver in a mouse transplantation model. Using the same differentiation and transplantation protocols, we also assessed the ability of human iPSCs derived from each of the three developmental germ layer tissues (that is, ectoderm, mesoderm, and endoderm) to regenerate mouse liver. These iPSC lines, with similar but distinct global DNA methylation patterns, differentiated into multistage hepatic cells with an efficiency similar to that of human embryonic stem cells. Human hepatic cells at various differentiation stages derived from iPSC lines of different origins successfully repopulated the liver tissue of mice with liver cirrhosis. They also secreted human-specific liver proteins into mouse blood at concentrations comparable to that of proteins secreted by human primary hepatocytes. Our results demonstrate the engraftment and liver regenerative capabilities of human iPSC-derived multistage hepatic cells in vivo and suggest that human iPSCs of distinct origins and regardless of their parental epigenetic memory can efficiently differentiate along the hepatic lineage.

Isolation of hematopoietic stem cells and the effect of CD38 expression during the early erythroid progenitor cell development process

The aim of this study was to investigate changes in primitive hematopoietic cells through CD38 expression, identify the stage at which erythrocyte differentiation CD38 gains activity and the effects of serum factors on this expression by establishing a hematopoietic stem cell system in the erythroid development process. Using an immunomagnetic labeling and separation technique, CD34(+) cells were selected from cord blood. The CD34(+) cells were cultured in a 2 mM L-glutamine-enriched medium containing erythropoietin (Epo), penicillin-streptomycin and stem cell factor (SCF), and were incubated in 5% CO(2) at 37°C. In erythroid development pathways following CD38 expression, primitive/progenitor human hematopoietic cells obtained from cord blood were assessed through the erythroid development process in a serum-free medium in the presence of proper SCF and Epo. At the end of the 26-day process, using staining with a Megacult-c staining kit, it was determined that progenitor cells nucleate and differentiate into erythroid cell lines of 8-10 μm. During the course of this process, we analyzed increases over time in NAD glycohydrolase activity rates using the supernatant liquid samples. Results of co-culture experiments in cell culture studies showed that the stimulating effects of CD38 expression originate from specific serum factors. CD38 expression has been shown to occur at hematopoietic cell sources as well as at a number of differentiation levels. In the proliferation process the possible induction of CD38 through specific serum factors leads us to conclude that it may be involved in proliferation with a physiological task or that it may be involved in an event, such as an apoptotic process.

Concise review: Human pluripotent stem cell-based models for cardiac and hepatic toxicity assessment

Considering the costs associated with drug development, there are billions of dollars to be saved by reducing late-stage attrition in the pharmaceutical industries. Reports on the use of human pluripotent stem cells (hPSCs) and their functional derivatives in applications for safety assessment of drugs have begun to appear in the scientific literature. These reports are encouraging and fuel further developments of improved human cellular models that may increase the clinical relevance and reduce the need of experimental animals in preclinical drug discovery. However, a few factors still limit the general and wide-spread industry implementation of these new stem cell-based models, including cost of manufacture, level of functionality of the differentiated cells, assay validation, verification of human relevance, and benchmarking to conventional models. This review discusses the emerging field of hPSC-based models for drug discovery and development with a focus on cardiac and hepatic toxicity testing and how these approaches may improve current applications used in the pharmaceutical industry. Although much research remains to make hPSC-based models mainstream tools in the industry, importantly, this review highlights currently available opportunities. In addition, a forward looking discussion on novel applications using tissue preparations generated from hPSCs illustrates the opportunities to create complex models in vitro with the aim of simulating the systemic response of a drug in vivo.

Cellular Reprogramming toward the Erythroid Lineage

Haemoglobinopathies such as thalassaemia and sickle cell disease present a major health burden. Currently, the main forms of treatment for these diseases are packed red blood cell transfusions and the administration of drugs which act to nonspecifically reactivate the production of foetal haemoglobin. These treatments are ongoing throughout the life of the patient and are associated with a number of risks, such as limitations in available blood for transfusion, infections, iron overload, immune rejection, and side effects associated with the drug treatments. The field of cellular reprogramming has advanced significantly in the last few years and has recently culminated in the successful production of erythrocytes in culture. This paper will discuss cellular reprogramming and its potential relevance to the treatment of haemoglobinopathies.

Applications of patient-specific induced pluripotent stem cells; focused on disease modeling, drug screening and therapeutic potentials for liver disease

The recent advances in the induced pluripotent stem cell (iPSC) research have significantly changed our perspectives on regenerative medicine by providing researchers with a unique tool to derive disease-specific stem cells for study. In this review, we describe the human iPSC generation from developmentally diverse origins (i.e. endoderm-, mesoderm-, and ectoderm- tissue derived human iPSCs) and multistage hepatic differentiation protocols, and discuss both basic and clinical applications of these cells including disease modeling, drug toxicity screening/drug discovery, gene therapy and cell replacement therapy.

Knockdown of tissue nonspecific alkaline phosphatase impairs neural stem cell proliferation and differentiation

In the adult mammalian brain the subependymal layer of the lateral ventricles houses neural stem cells giving rise to young neurons migrating towards the olfactory bulb. The molecular cues controlling essential functions within the neurogenesis pathway such as proliferation, short and long distance migration, differentiation and functional integration are poorly understood. Neural progenitors in situ express the tissue nonspecific form of alkaline phosphatase (TNAP), a cell surface-located nonspecific phosphomonoesterase capable of hydrolyzing extracellular nucleotides. To gain insight into the functional role of TNAP in cultured multipotent neural stem cells we applied a knockdown protocol using RNA interference with shRNA and retroviral infection. We show that TNAP knockdown reduces cell proliferation and differentiation into neurons or oligodendrocytes. This effect is abrogated by addition of alkaline phosphatase to the culture medium. Our results suggest that TNAP is essential for NSC proliferation and differentiation in vitro and possibly also in vivo.

Promotion of human adipose-derived stem cell proliferation mediated by exogenous nucleosides

Adult stem cells are becoming the best option for regenerative medicine because they have low tumourigenic potential and permit autologous transplantation, even without in vitro culture. Our objectives were to evaluate the effects of exogenous nucleosides on the proliferation of hASCs (human adipose-derived stem cells), with or without co-treatment with 5-aza (5-azacytidine), and to analyse the expression of lamin A/C during cardiomyocyte differentiation of these cells. We isolated hASCs from human lipoaspirates that were positive for mesenchymal stem cell markers. We found that 5-aza induces a dose-dependent inhibition of hASC proliferation [IC50 (inhibitory concentration 50): 5.37 microM], whereas exogenous nucleosides significantly promote the proliferation of hASCs and partially revert the antiproliferative effect of the drug. Multipotentiality of isolated hASCs was confirmed by adipogenic, osteogenic and cardiomyogenic induction. 5-Aza-induced cells expressed cardiac troponins I and T and myosin light chain 2, myocardial markers that were directly correlated with lamin A/C expression. Our results support the importance of the nucleoside supplementation of media to improve conditions for the expansion and maintenance of hASCs in culture. In addition, the quantification of lamin A/C expression appears to be a good marker for the characterization of cardiomyocyte differentiation of stem cells that has rarely been used.

Pluripotent stem cell derived hepatocyte like cells and their potential in toxicity screening

Despite considerable progress in modelling human liver toxicity, the requirement still exists for efficient, predictive and cost effective in vitro models to reduce attrition during drug development. Thousands of compounds fail in this process, with hepatotoxicity being one of the significant causes of failure. The cost of clinical studies is substantial, therefore it is essential that toxicological screening is performed early on in the drug development process. Human hepatocytes represent the gold standard model for evaluating drug toxicity, but are a limited resource. Current alternative models are based on immortalised cell lines and animal tissue, but these are limited by poor function, exhibit species variability and show instability in culture. Pluripotent stem cells are an attractive alternative as they are capable of self-renewal and differentiation to all three germ layers, and thereby represent a potentially inexhaustible source of somatic cells. The differentiation of human embryonic stem cells and induced pluripotent stem cells to functional hepatocyte like cells has recently been reported. Further development of this technology could lead to the scalable production of hepatocyte like cells for liver toxicity screening and clinical therapies. Additionally, induced pluripotent stem cell derived hepatocyte like cells may permit in vitro modelling of gene polymorphisms and genetic diseases.

Role of stem-cell-derived hepatic endoderm in human drug discovery

Accurate prediction of human drug toxicity is a vital part of the drug discovery process. However, the safety evaluation process is hindered by the availability and quality of primary human liver models with which to study drug toxicity. In an attempt to overcome this limitation, research has focused on deriving human hepatocytes from a number of sources, including progenitors from fetal and adult liver, human cell lines derived from liver tumours, immortalized human hepatocytes and pluripotent stem cells. The major hurdles in developing scalable and high-fidelity human hepatocytes from hepatic cell lines and fetal and adult progenitors have been limited organ availability, homogeneous cell purification, short-term cell culture, and the rapid loss of hepatocyte phenotype and function in culture. Therefore it has been necessary to find alternative sources of human hepatocytes which circumvent these issues. The research in our group has focused on generating human hepatic endoderm from the scalable pluripotent stem cell populations, human embryonic stem cells and induced pluripotent stem cells. We have developed efficient and scalable models of human hepatocyte differentiation from these cell populations. Moreover, stem-cell-derived hepatic endoderm displays many of the functional attributes of primary human hepatocytes. Our research is now focused on developing defined culture systems and improving cell culture microenvironments in order to improve our understanding of the mechanisms regulating human liver development. This will in turn facilitate the generation of broad-range functioning hepatic endoderm in vitro. By taking these approaches, we believe that it will be possible to improve the predictive nature of our in vitro models, revolutionizing the manner in which industry measures human drug toxicity and having an impact on drug attrition.

BMP-2/6 heterodimer is more effective than BMP-2 or BMP-6 homodimers as inductor of differentiation of human embryonic stem cells

Background

Bone Morphogenetic Protein (BMP) signaling pathways are involved in differentiation of stem cells into diverse cell types, and thus BMPs can be used as main guidance molecules for in vitro differentiation of human stem cells.

Methodology/Principal Findings

We have analyzed the ability for inducing differentiation of the heterodimer BMP-2/BMP-6 (BMP-2/6) compared to the homodimers BMP-2 or BMP-6, using human embryonic stem (hES) cells H9 as model system. When incubated in a medium with high concentration of basic fibroblastic growth factor (FGF2), 100 ng/ml of human recombinant BMPs induced morphological changes and differentiation of hES cells in 24 to 48 hours. After 5 days, expression of differentiation markers was induced and quantified by quantitative PCR (qPCR) and flow cytometry. BMP-2/6 exhibited stronger activity for the induction of the expression of trophectodermal (CDX2) and endodermal (SOX17, GATA4, AFP) markers than BMP-2 or BMP-6 homodimers. BMP-2/6 also induced the expression of BMPR2 gene more effectively than BMP-2 or BMP-6 when used at the same concentration and time. Moreover, the percentage of cells expressing the surface endodermal marker CXCR4 was also increased for the heterodimer when compared to both homodimers. BMP-2/6 was a more potent activator of Smad-dependent (SMAD1/5) and Smad-independent signaling (mitogen-activated protein kinases ERK and p38) than BMP-2 and BMP-6, and the activation of these pathways might play a role in its increased potency for inducing hES cell differentiation.

Conclusions/Significance

Therefore, we conclude that BMP-2/6 is more potent than BMP-2 or BMP-6 for inducing differentiation of hES cells, and it can be used as a more powerful substitute of these BMPs in in vitro differentiation guidance.

Progress and future challenges in stem cell-derived liver technologies

The emergence of regenerative medicine has led to significant advances in the identification and understanding of human stem cells and adult progenitor cells. Both cell populations exhibit plasticity and theoretically offer a potential source of somatic cells in large numbers. Such a resource has an important role to play in the understanding of human development, in modeling human disease and drug toxicity, and in the generation of somatic cells in large numbers for cell-based therapies. Presently, liver transplantation is the only effective treatment for end-stage liver disease. Although this procedure can be carried out with high levels of success, the routine transplant of livers is severely limited by organ donor availability. As a result, attention has focused on the ability to restore liver mass and function by alternative approaches ranging from the bioartificial device to transplantation of human hepatocytes. In this review we will focus on the generation of human hepatic endoderm from different stem/progenitor cell populations with a view to its utility in regenerative medicine.

Altered migration and adhesion potential of pro-neurally converted human bone marrow stromal cells

BACKGROUND

Bone marrow (BM)-derived mesenchymal stromal cells (MSC) are promising candidate cells for the development of neuroregenerative therapies. We have previously introduced the pro-neural conversion of human MSC to neural stem cell-like cells (m-NSC) by culturing them in suspension culture under serum-free conditions.

METHODS

In the present study, we used a modified Boyden chamber assay to study the influence of various chemoattractants and extracellular matrix components on MSC and m-NSC migration in vitro. The underlying mechanisms were investigated further by applying real-time reverse transcriptase (RT)-polymerase chain reaction (PCR) and flow cytometry.

RESULTS

The basal migration of m-NSC was significantly reduced compared with MSC (six versus 27 out of 10,000 cells migrated within 6 h). We evaluated the effects of bone morphogenic protein 2 (BMP2), insulin-like growth factor 1 (IGF1), platelet-derived growth factor bb (PDGFbb), vascular endothelial growth factor (VEGFa), and stromal cell-derived factor 1 (SDF1) on the migration potential of both cell types and PDGFbb proved to be the most potent stimulant of migration (235 versus 198 m-NSC or MSC migrated). Adhesion of m-NSC to the filter membrane was delayed and not affected by IGF1 or PDGFbb: 90% of MSC, but only 20% of m-NSC, adhered within 1 h, with 90% of m-NSC adhering within 3 h. However, real-time RT-PCR and flow cytometry revealed an up-regulation of the PDGF receptor B following conversion. Coating the membranes with collagen type I or hyaluronan also significantly influenced cell migration.

DISCUSSION

We could identify major chemoattractive factors for m-NSC and gained partial insight into the complex processes involved in migration of neurally converted cells.

Arachidonic acid potentiates hypoxia-induced VEGF expression in mouse embryonic stem cells: involvement of Notch, Wnt, and HIF-1α

Recent investigations suggest that hypoxia increases the release of fatty acids, which participate in the regulation of cytokine synthesis and cell growth. Therefore, in this study, we examined the effect of arachidonic acid (AA) on hypoxia-induced vascular endothelial growth factor (VEGF) expression and its related signaling pathways in mouse embryonic stem (ES) cells. Hypoxia increased the level of [3H]AA release and VEGF expression. AA treatment concurrent with hypoxia further increased the PGE2 production and VEGF expression level, which was inhibited by the suppression of cPLA2 and cyclooxygenase 2 (COX-2) pathways. Hypoxia increased the level of Notch-1 and Wnt-1/β-catenin expression, which was blocked by the inhibition of COX-2, and inhibition of Notch-1 by γ-secretase inhibitor blocked Wnt-1 activation. Moreover, the hypoxia-induced increase of hypoxia-inducible factor 1α (HIF-1α) expression induced Notch-1 activation and was regulated by Wnt-1 activation. The expression of each signaling molecule induced an increase in VEGF expression that was greater in hypoxia with AA than in hypoxia alone. The inhibition of VEGF expression using VEGF-targeted small interfering RNA decreased the hypoxia-induced increase in cell cycle regulatory protein expression, DNA synthesis, and cell number, suggesting that hypoxia-induced VEGF expression stimulates proliferation of mouse ES cells. In conclusion, AA potentiates hypoxia-induced VEGF expression in mouse ES cells through the Notch-1, Wnt-1, and HIF-1α pathways.

Human beta-cell precursors mature into functional insulin-producing cells in an immunoisolation device: implications for diabetes cell therapies

BACKGROUND

Islet transplantation is limited by the need for chronic immunosuppression and the paucity of donor tissue. As new sources of human beta-cells are developed (e.g., stem cell-derived tissue), transplanting them in a durable device could obviate the need for immunosuppression, while also protecting the patient from any risk of tumorigenicity. Here, we studied (1) the survival and function of encapsulated human beta-cells and their progenitors and (2) the engraftment of encapsulated murine beta-cells in allo- and autoimmune settings.

METHODS

Human islets and human fetal pancreatic islet-like cell clusters were encapsulated in polytetrafluorethylene devices (TheraCyte) and transplanted into immunodeficient mice. Graft survival and function was measured by immunohistochemistry, circulating human C-peptide levels, and blood glucose levels. Bioluminescent imaging was used to monitor encapsulated neonatal murine islets.

RESULTS

Encapsulated human islet-like cell clusters survived, replicated, and acquired a level of glucose responsive insulin secretion sufficient to ameliorate hyperglycemia in diabetic mice. Bioluminescent imaging of encapsulated murine neonatal islets revealed a dynamic process of cell death followed by regrowth, resulting in robust long-term allograft survival. Further, in the non-obese diabetic (NOD) mouse model of type I diabetes, encapsulated primary beta-cells ameliorated diabetes without stimulating a detectable T-cell response.

CONCLUSIONS

We demonstrate for the first time that human beta-cells function is compatible with encapsulation in a durable, immunoprotective device. Moreover, our study suggests that encapsulation of beta-cells before terminal differentiation will be a successful approach for new cell-based therapies for diabetes, such as those derived from stem cells.

Aging of the inceptive cellular population: the relationship between stem cells and aging

The average life expectancy worldwide has about doubled and the global population has increased six fold over the past century. With improving health care in the developed world there is a proportional augmentation in the treatment necessary for elderly patients occasioning the call for increased research in the area of aging and age-related diseases. The manifestation of this research has been focalized on the causative cellular processes and molecular mechanisms involved. Here we will discuss the efforts of this research in the area of stem cells, delving into the regulatory mechanisms and how their de-regulation could be attributed to aging and age-related diseases.

The inhibitory role of stromal cell mesenchyme on human embryonic stem cell hepatocyte differentiation is overcome by Wnt3a treatment

Pluripotent stem cells are derived from the inner cell mass of preimplantation embryos, and display the ability of the embryonic founder cells by forming all three germ lineages in vitro. It is well established that the cellular niche plays an important role in stem cell maintenance and differentiation. Stem cells generally have limited function without the specialized microenvironment of the niche that provides key cell-cell contact, soluble mediators, and extracellular matrices. We were interested in the role that Wnt signaling, in particular Wnt3a, played in human embryonic stem cell (hESC) differentiation to hepatic endoderm in vitro. hESC differentiation to hepatic endoderm was efficient in pure stem cell populations. However, in younger hESC lines, generating stromal cell mesenchyme, our model was very inefficient. The negative effect of stroma could be reversed by pretreating hESCs with Wnt3a prior to the onset of hepatocyte differentiation. Wnt3a pretreatment reinstated efficient hESC differentiation to hepatic endoderm. These studies represent an important step in understanding hepatocyte differentiation from hESCs and the role played by the cellular niche in vitro.

Highly efficient differentiation of hESCs to functional hepatic endoderm requires ActivinA and Wnt3a signaling

Human embryonic stem cells (hESCs) are a valuable source of pluripotential primary cells. To date, however, their homogeneous cellular differentiation to specific cell types in vitro has proven difficult. Wnt signaling has been shown to play important roles in coordinating development, and we demonstrate that Wnt3a is differentially expressed at critical stages of human liver development in vivo. The essential role of Wnt3a in hepatocyte differentiation from hESCs is paralleled by our in vitro model, demonstrating the importance of a physiologic approach to cellular differentiation. Our studies provide compelling evidence that Wnt3a signaling is important for coordinated hepatocellular function in vitro and in vivo. In addition, we demonstrate that Wnt3a facilitates clonal plating of hESCs exhibiting functional hepatic differentiation. These studies represent an important step toward the use of hESC-derived hepatocytes in high-throughput metabolic analysis of human liver function.