Can the life span of human marrow stromal cells be prolonged by bmi-1, E6, E7, and/or telomerase without affecting cardiomyogenic differentiation?

Immortalization of epidural fat-derived mesenchymal stem cells: In vitro characterization and adipocyte differentiation potential

BACKGROUND

Mesenchymal stem cells (MSCs) are promising candidates for regenerative therapy due to their self-renewal capability, multilineage differentiation potential, and immunomodulatory effects. The molecular characteristics of MSCs are influenced by their location. Recently, epidural fat (EF) and EF-derived MSCs (EF-MSCs) have garnered attention due to their potential benefits to the spinal microenvironment and their high expression of neural SC markers. However, their clinical applications are limited due to cell senescence and limited accessibility of EF. Although many studies have attempted to establish an immortalized, stable SC line, the characteristics of immortalized EF-MSCs remain to be clarified.

AIM

To establish and analyze stable immortalized EF-MSCs.

METHODS

The phenotypes of EF-MSCs were analyzed using optical microscopy. Cell immortalization was performed using lentiviral vectors. The biomolecular characteristics of the cells were analyzed by immunoblotting, quantitative PCR, and proteomics.

RESULTS

The immortalized EF-MSCs demonstrated a significantly extended lifespan compared to the control group, with well-preserved adipogenic potential and SC surface marker expression. Introduction of human telomerase reverse transcriptase genes markedly increased the lifespan of EF-MSCs. Proteomics analysis revealed substantial increase in the expression of DNA replication pathway components in immortalized EF-MSCs.

CONCLUSION

Immortalized EF-MSCs exhibited significantly enhanced proliferative capacity, retained adipogenic potential, and upregulated the expression of DNA replication pathway components.

Generation of functional liver sinusoidal endothelial-like cells from human bone marrow-derived mesenchymal stem cells

Introduction

Liver sinusoidal endothelial cells (LSECs) are specialized vascular endothelial cells that play an important role in the maintenance of biological homeostasis. However, the lack of versatile human LSECs has hindered research on LSECs and development of medical technologies for liver diseases including hemophilia A. In this study, we developed a technique to induce LSEC differentiation from human bone marrow-derived mesenchymal stem cells (BM-MSCs).

Methods

To induce LSECs from human BM-MSCs, cytokines and chemical compounds associated with signaling implicated in LSEC differentiation and liver development were screened. Then LSEC-related genes and proteins expression in the differentiated cells were analyzed by qPCR and flow cytometry analysis, respectively. LSEC-related functions of the differentiated cells were also examined.

Results

We found that the gene expression of LSEC markers, such as LYVE1, was considerably increased by culturing human BM-MSCs with bone morphogenetic protein 4, fibroblast growth factor 8b, transforming growth factor-β signal inhibitor, and cyclic AMP. Furthermore, the differentiated cells expressed LSEC marker proteins and clearly demonstrated LSEC-specific functions, such as the uptake of hyaluronic acid.

Conclusions

Our result indicate that the functional LSEC-like cells were successfully generated from human BM-MSCs using our established protocol.

Surface modification of silica nonwoven fabrics for osteogenesis of bone marrow-derived mesenchymal stem cells

Silica nonwoven fabrics (SNFs) with high mechanical strength and porosity are known to exhibit high cell proliferation and osteogenic differentiation potential of mesenchymal stem cells (MSCs) by morphologically mimicking the extracellular matrix (ECM). To further improve the osteoinductive ability of SNFs, it could be effective to increase the interaction between MSCs and ECM components because exogenous ECM components seem to modulate the fate of MSCs differentiation. In this study, we developed immobilization methods for ECM components, such as collagen, fibronectin, and chondroitin sulphate C on SNFs, to improve cell-matrix interactions and examined their suitability for bone tissue regeneration. Collagen and fibronectin were immobilized via physical adsorption and chondroitin sulphate C was also immobilized by the layer-by-layer method combined with chitosan on SNF surfaces to maintain the high porosity of SNFs. The treated SNFs were characterized using scanning electron microscopy, Fourier transform infrared spectroscopy, and X-ray photoelectron spectroscopy. In osteogenic differentiation culture, modified SNFs showed significantly increased expression of osteogenic differentiation marker genes compared to unmodified SNFs. These results suggest that the present methods improve cell-matrix interactions and enhance the cellular functions of MSCs. We are convinced that these simple modification techniques for ECM components are effective in functionalizing various 3D fabric scaffolds possessing hydrophilic groups.

Strategies for immortalisation of amnion-derived mesenchymal and epithelial cells

Mesenchymal (human amniotic mesenchymal stem cell [HAMSC]) and epithelial cells (human amnion epithelial cell [HAEC]) derived from human amniotic membranes possess characteristics of pluripotency. However, the pluripotency of HAMSC and HAEC are sustained only for a finite period. This in vitro cell growth can be extended by cell immortalisation. Many well-defined immortalisation systems have been used for artificially overexpressing genes such as human telomerase reverse transcriptase in HAMSC and HAEC leading to controlled and prolonged cell proliferation. In recent years, much progress has been made in our understanding of the cellular machinery that regulates the cell cycle when immortalised. This review summarises the current understanding of molecular mechanisms that contribute to cell immortalisation, the strategies that have been employed to immortalise amnion-derived cell types, and their likely applications in regenerative medicine.

Involvement of the p53-p16/RB pathway control mechanism in early-stage carcinogenesis in head and neck squamous cell carcinoma

Head and neck squamous cell carcinoma develops through a heterogeneous process involving human papillomavirus infection, smoking, and alcohol consumption. A comprehensive genomic analysis of head and neck squamous cell carcinomas to date has identified a few single driver gene mutations, the most frequent of which involve TP53 and CDKN2A/p16. To investigate the involvement of the tumorigenesis mechanism in early-stage carcinogenesis, HPV-derived genomes E6 and E7, which are carcinogens, and stem/progenitor-associated, polycomb (PcG) genes Bmi1 and TERT were induced into human stromal cells and immortalized as the head and neck squamous cell carcinoma model. We found that Bmi1 suppressed both the p16INK4a and p16/Rb-p53 pathway cross-talks. The E7 group showed that endogenous p53 is highly expressed and eludes chromosome number aberration, even on long-term observation. Bmi1 was predominantly expressed in early head and neck squamous cell carcinoma, and PcG was essential in early cancer development. Additionally, TP53 whole exon analysis revealed categories useful for estimating malignant potential, such as poor prognosis and high recurrence at the transection site. Therefore, understanding the p53-p16/RB pathway in head and neck squamous cell carcinoma is an essential factor to elucidate the early carcinogenesis of head and neck squamous cell carcinoma.

Preliminary Characterization of the Epigenetic Modulation in the Human Mesenchymal Stem Cells during Chondrogenic Process

Regenerative medicine represents a growing hot topic in biomedical sciences, aiming at setting out novel therapeutic strategies to repair or regenerate damaged tissues and organs. For this perspective, human mesenchymal stem cells (hMSCs) play a key role in tissue regeneration, having the potential to differentiate into many cell types, including chondrocytes. Accordingly, in the last few years, researchers have focused on several in vitro strategies to optimize hMSC differentiation protocols, including those relying on epigenetic manipulations that, in turn, lead to the modulation of gene expression patterns. Therefore, in the present study, we investigated the role of the class II histone deacetylase (HDAC) inhibitor, MC1568, in the hMSCs-derived chondrogenesis. The hMSCs we used for this work were the hMSCs obtained from the amniotic fluid, given their greater differentiation capacity. Our preliminary data documented that MC1568 drove both the improvement and acceleration of hMSCs chondrogenic differentiation in vitro, since the differentiation process in MC1568-treated cells took place in about seven days, much less than that normally observed, namely 21 days. Collectively, these preliminary data might shed light on the validity of such a new differentiative protocol, in order to better assess the potential role of the epigenetic modulation in the process of the hypertrophic cartilage formation, which represents the starting point for endochondral ossification.

Analysis of the aggregation mechanism of chondroitin sulfate/chitosan particles and fabrication of hydrogel cell scaffolds

In this study, the aggregation mechanism of polyion complex (PIC) particles from chitosan (CHI) and chondroitin sulfate C (CS) in phosphate-buffered saline (PBS) was analyzed, and a novel method for the fabrication of hydrogels via aggregation was developed. The PBS induced a decrease in the ζ-potential of the CS/CHI PIC particles, increase in their diameter, and aggregation in a concentration-dependent manner. The hydrogels prepared by mixing CS/CHI PIC particle dispersion and PBS showed the PIC components, with porous structure, high swelling ratio (161.4 ± 13.3%), and high storage moduli (26.2 ± 1.4 kPa). By mixing PBS with suspended adhesive cells and CS/CHI PIC particle dispersion, hydrogels with high cell-loading efficiency were successfully synthesized. The loaded cells within the hydrogels exhibited high viability, uniform distribution, and formation of cell aggregates. These results indicate that CS/CHI-based hydrogels have a potential application as three-dimensional scaffolds for cell culture in tissue engineering.

Generation of Mesenchymal Cell Lines Derived from Aged Donors

Background: Mesenchymal stromal cells (MSCs) have the capacity for self-renewal and multi-differentiation, and for this reason they are considered a potential cellular source in regenerative medicine of cartilage and bone. However, research on this field is impaired by the predisposition of primary MSCs to senescence during culture expansion. Therefore, the aim of this study was to generate and characterize immortalized MSC (iMSC) lines from aged donors. Methods: Primary MSCs were immortalized by transduction of simian virus 40 large T antigen (SV40LT) and human telomerase reverse transcriptase (hTERT). Proliferation, senescence, phenotype and multi-differentiation potential of the resulting iMSC lines were analyzed. Results: MSCs proliferate faster than primary MSCs, overcome senescence and are phenotypically similar to primary MSCs. Nevertheless, their multi-differentiation potential is unbalanced towards the osteogenic lineage. There are no clear differences between osteoarthritis (OA) and non-OA iMSCs in terms of proliferation, senescence, phenotype or differentiation potential. Conclusions: Primary MSCs obtained from elderly patients can be immortalized by transduction of SV40LT and hTERT. The high osteogenic potential of iMSCs converts them into an excellent cellular source to take part in in vitro models to study bone tissue engineering.

BMI1 in the heart: Novel functions beyond tumorigenesis

The BMI1 protein, a member of the PRC1 family, is a well recognised transcriptional suppressor and has the capability of maintaining the self-renewal and proliferation of tissue-specific stem cells. Numerous studies have established that BMI1 is highly expressed in a variety of malignant cancers and serves as a key regulator in the tumorigenesis process. However, our understanding of BMI1 in terminally differentiated organs, such as the heart, is relatively nascent. Importantly, emerging data support that, beyond the tumor, BMI1 is also expressed in the heart tissue and indeed exerts profound effects in various cardiac pathological conditions. This review gives a summary of the novel functions of BMI1 in the heart, including BMI1-positive cardiac stem cells and BMI1-mediated signaling pathways, which are involved in the response to various cardiac pathological stimuli. Besides, we summarize the recent progress of BMI1 in some novel and rapidly developing cardiovascular therapies. Furtherly, we highlight the properties of BMI1, a therapeutic target proved effective in cancer treatment, as a promising target to alleviate cardiovascular diseases.

Usefulness of Mesenchymal Cell Lines for Bone and Cartilage Regeneration Research

The unavailability of sufficient numbers of human primary cells is a major roadblock for in vitro repair of bone and/or cartilage, and for performing disease modelling experiments. Immortalized mesenchymal stromal cells (iMSCs) may be employed as a research tool for avoiding these problems. The purpose of this review was to revise the available literature on the characteristics of the iMSC lines, paying special attention to the maintenance of the phenotype of the primary cells from which they were derived, and whether they are effectively useful for in vitro disease modeling and cell therapy purposes. This review was performed by searching on Web of Science, Scopus, and PubMed databases from 1 January 2015 to 30 September 2019. The keywords used were ALL = (mesenchymal AND ("cell line" OR immortal*) AND (cartilage OR chondrogenesis OR bone OR osteogenesis) AND human). Only original research studies in which a human iMSC line was employed for osteogenesis or chondrogenesis experiments were included. After describing the success of the immortalization protocol, we focused on the iMSCs maintenance of the parental phenotype and multipotency. According to the literature revised, it seems that the maintenance of these characteristics is not guaranteed by immortalization, and that careful selection and validation of clones with particular characteristics is necessary for taking advantage of the full potential of iMSC to be employed in bone and cartilage-related research.

Peripheral artery disease: the new frontiers of imaging techniques to evaluate the evolution of regenerative medicine

Introduction: Stem cells (ESC, iPSC, MSC) are known to have intrinsic regenerative properties. In the last decades numerous findings have favored the development of innovative therapeutic protocols based on the use of stem cells (Regenerative Medicine/Cell Therapy) for the treatment of numerous diseases including PAD, with promising results in preclinical studies. So far, several clinical studies have shown a general improvement of the patient's clinical outcome, however they possess many critical issues caused by the non-randomized design of the limited number of patients examined, the type cells to be used, their dosage, the short duration of treatment and also their delivery strategy. Areas covered: In this context, the use of the most advanced molecular imaging techniques will allow the visualization of very important physio-pathological processes otherwise invisible with conventional techniques, such as angiogenesis, also providing important structural and functional data. Expert opinion: The new frontier of cell therapy applied to PAD, potentially able to stop or even the process that causes the disease, with particular emphasis on the clinical aspects that different types of cells involve and on the use of more innovative molecular imaging techniques now available.

Reversal of established liver fibrosis by IC-2-engineered mesenchymal stem cell sheets

Chronic hepatitis viral infection, alcoholic intoxication, and obesity cause liver fibrosis, which progresses to decompensated liver cirrhosis, a disease for which medical demands cannot be met. Since there are currently no approved anti-fibrotic therapies for established liver fibrosis, the development of novel modalities is required to improve patient prognosis. In this study, we clarified the anti-fibrotic effects of cell sheets produced from human bone marrow-derived mesenchymal stem cells (MSCs) incubated on a temperature-sensitive culture dish with the chemical compound IC-2. Orthotopic transplantation of IC-2-engineered MSC sheets (IC-2 sheets) remarkably reduced liver fibrosis induced by chronic CCl4 administration. Further, the marked production of fibrolytic enzymes such as matrix metalloproteinase (MMP)-1 and MMP-14, as well as thioredoxin, which suppresses hepatic stellate cell activation, was observed in IC-2 sheets. Moreover, the anti-fibrotic effect of IC-2 sheets was much better than that of MSC sheets. Finally, knockdown experiments revealed that MMP-14 was primarily responsible for the reduction of liver fibrosis. Here, we show that IC-2 sheets could be a promising therapeutic option for established liver fibrosis.

Mesenchymal stem cells suppress fibroblast proliferation and reduce skin fibrosis through a TGF-β3-dependent activation

Recent studies showed that transplantation of mesenchymal stem cells (MSCs) significantly decreased tissue fibrosis; however, little attention has been paid to its efficacy on attenuating skin fibrosis, and the mechanism involved in its effect is poorly understood. In this work, we investigated the effects of MSCs on keloid fibroblasts and extracellular matrix deposition through paracrine actions and whether the antifibrotic properties of MSCs involved transforming growth factor-β (TGF-β)-dependent activation. In vitro experiments showed that conditioned media (CM) from MSCs decreased viability, a-smooth muscle actin expression, and collagen secretion of human keloid fibroblasts. In addition, TGF-β3 secreted by MSCs was expressed at high level under inflammatory environment, and blocking the activity of TGF-β3 apparently antagonized the suppressive activity of MSC CM, which demonstrated that TGF-β3 played a preponderant role in preventing collagen accumulation. In vivo studies showed that MSC CM infusion in a mouse dermal fibrosis model induced a significant decrease in skin fibrosis. Histological examination of tissue sections and immunohistochemical analysis for α-smooth muscle actin revealed that TGF-β3 of CM-mediated therapeutic effects could obviously attenuate matrix production and myofibroblast proliferation and differentiation. These findings suggest that TGF-β3 mediates the attenuating effect of MSCs on both the proliferation and extracellular matrix production of human keloid fibroblasts and decreases skin fibrosis of mouse model, thus providing new understanding and MSC-based therapeutic strategy for cutaneous scar treatment.

Magnetic resonance monitoring of superparamagnetic iron oxide (SPIO)-labeled stem cells transplanted into the inner ear

In the field of regenerative medicine, cell transplantation or cell-based therapies for inner ear defects are considered to be promising candidates for a therapeutic strategy. In this paper, we report on a study that examined the use of magnetic resonance imaging (MRI) to monitor stem cells transplanted into the cochlea labeled with superparamagnetic iron oxide (SPIO), a contrast agent commonly used with MRI. First, we demonstrated in vitro that stem cells efficiently took up SPIO particles. This was confirmed by Prussian blue staining and TEM. In MRI studies, T2 relaxation times of SPIO-labeled cells decreased in a dose-dependent manner. Next, we transplanted SPIO-labeled cells directly into the cochlea in vivo and then performed MRI 1h, 2 weeks, and 4 weeks after transplantation. The images were evaluated objectively by measuring signal intensity (SI). SI within the ears receiving transplants was significantly lower (P<0.05) than that of control sides at the 1-h assessment. This novel method will be helpful for evaluating stem cell therapies, which represents a new strategy for inner ear regeneration. To the best of our knowledge, this study is the first to demonstrate that local transplantation of labeled stem cells into the inner ear can be visualized in vivo via MRI.

Mesenchymal stem cells correct inappropriate epithelial-mesenchyme relation in pulmonary fibrosis using stanniocalcin-1

Current hypotheses suggest that aberrant wound healing has a critical role in the pathogenesis of idiopathic pulmonary fibrosis (IPF). In these hypotheses, continuous TGF-β1 secretion by alveolar epithelial cells (AECs) in abnormal wound healing has a critical role in promoting fibroblast differentiation into myofibroblasts. Mesenchymal stem cells (MSCs) home to the injury site and reduce fibrosis by secreting multifunctional antifibrotic humoral factors in IPF. In this study, we show that MSCs can correct the inadequate-communication between epithelial and mesenchymal cells through STC1 (Stanniocalcin-1) secretion in a bleomycin-induced IPF model. Inhalation of recombinant STC1 shows the same effects as the injection of MSCs. Using STC1 plasmid, it was possible to enhance the ability of MSCs to ameliorate the fibrosis. MSCs secrete large amounts of STC1 in response to TGF-β1 in comparison to AECs and fibroblasts. The antifibrotic effects of STC1 include reducing oxidative stress, endoplasmic reticulum (ER) stress, and TGF-β1 production in AECs. The STC1 effects can be controlled by blocking uncoupling protein 2 (UCP2) and the secretion is affected by the PI3/AKT/mTORC1 inhibitors. Our findings suggest that STC1 tends to correct the inappropriate epithelial-mesenchymal relationships and that STC1 plasmid transfected to MSCs or STC1 inhalation could become promising treatments for IPF.

Amniotic membrane covering for facial nerve repair

Amniotic membranes have been widely used in ophthalmology and skin injury repair because of their anti-inflammatory properties. In this study, we measured therapeutic efficacy and determined if amniotic membranes could be used for facial nerve repair. The facial nerves of eight rats were dissected and end-to-end anastomosis was performed. Amniotic membranes were covered on the anastomosis sites in four rats. Electromyography results showed that, at the end of the 3(rd) and 8(th) weeks after amniotic membrane covering, the latency values of the facial nerves covered by amniotic membranes were significantly shortened and the amplitude values were significantly increased. Compared with simple facial nerve anastomosis, after histopathological examination, facial nerve anastomosed with amniotic membrane showed better continuity, milder inflammatory reactions, and more satisfactory nerve conduction. These findings suggest that amniotic membrane covering has great potential in facial nerve repair.

Umbilical cord blood mesenchymal stem cells co-modified by TERT and BDNF: a novel neuroprotective therapy for neonatal hypoxic-ischemic brain damage

Hypoxic-ischemic brain damage (HIBD), a leading cause of perinatal disability and death, has limited therapeutic options. Stem cell therapy has been demonstrated as a potential novel therapy for neurological disorders. Compared with other types of stem cells, umbilical cord blood mesenchymal stem cells (UCB-MSCs) have several unique characteristics, such as a higher rate of cell proliferation and clonality. However, the limited life span of UCB-MSCs hinders their clinical application. Therefore, efforts are urgently needed to circumvent this disadvantage. Telomerase reverse transcriptase (TERT), which promotes cell proliferation and survival, plays a protective role in hypoxic-ischemic (HI) brain injury. Thus, it is reasonable to propose that UCB-MSCs modified by exogenous TERT expression might have a longer lifespan and increased viability. Moreover, brain-derived neurotrophic factor (BDNF), a neurotrophin that regulates development, regeneration, survival and maintenance of neurons, facilitates post-injury recovery when administered by infusion or virus-mediated delivery. Therefore, TERT- and BDNF-modified UCB-MSCs may have a longer lifespan and also maintain neural differentiation, thus promoting the recovery of neurological function following hypoxic-ischemic brain damage (HIBD) and thereby representing a new effective strategy for HIBD in neonates.

Cotransplantation of human umbilical cord-derived mesenchymal stem cells and umbilical cord blood-derived CD34⁺ cells in a rabbit model of myocardial infarction

The objective of the study is to investigate the effect of hypoxic preconditioning on the immunomodulatory properties of human umbilical cord-derived mesenchymal stem cells (hUC-MSCs) and the effect of cotransplantation of hUC-MSCs and human umbilical cord blood (hUCB)-derived CD34(+) cells in a rabbit model of myocardial infarction. hUC-MSCs with or without hypoxic preconditioning by cobalt chloride were plated in a 24-well plate, and then cocultured with hUCB-CD34(+) cells and PBMCs for 96 h at 37 °C in a 5% CO₂ incubator. For the negative control, hUC-MSCs were omitted. The groups were divided as follows: A1 = HP-MSCs + hUCB-CD34(+) cells + PBMC, A2 = hUC-MSCs + hUCB-CD34(+) cells + PBMC, Negative Control = hUCB-CD34(+) cells + PBMC. Culture supernatants of each group were collected, and the IL-10 and IFN-γ levels were measured by ELISA. A rabbit model of MI was established using a modified Fujita method. The animals were then randomized into three groups and received intramyocardial injections of 0.4 ml of PBS alone (n = 8, PBS group), hUC-MSCs in PBS (n = 8, hUC-MSCs group), or hUC-MSCs + CD34(+) cells in PBS (n = 8, Cotrans group), at four points in the infarct border zone. Echocardiography was performed at baseline, 4 weeks after MI induction, and 4 weeks after cell transplantation, respectively. Stem cell differentiation and neovascularization in the infracted area were characterized for the presence of cardiac Troponin I (cTnI) and CD31 by immunohistochemical staining, and the extent of myocardial fibrosis was evaluated by hematoxylin and eosin (H&E) and Masson's trichrome. IFN-γ was 27.00 ± 1.11, 14.20 ± 0.81, and 7.22 ± 0.14 pg/ml, and IL-10 was 31.68 ± 3.08, 61.42 ± 1.08, and 85.85 ± 1.80 pg/ml for the Control, A1 and A2 groups, respectively, which indicated that hUCB-CD34(+) cells induced immune reaction of peripheral blood mononuclear cells, whereas both hUC-MSCs and HP-MSCs showed an immunosuppressive effect, which, however, was attenuated by hypoxic preconditioning. The Cotrans group had less collagen deposition in the infarcted myocardium and better heart function than the hUC-MSCs or PBS group. The presence of cTnI-positive cells and CD31-positive tubular structures indicated the differentiation of stem cells into cardiomyocytes and neovascularization. The microvessel density was 12.19 ± 3.05/HP for the hUC-MSCs group and 31.63 ± 2.45/HP for the Cotrans group, respectively (P < 0.01). As a conclusion, both hUC-MSCs and HP-MSCs have an immunosuppressive effect on lymphocytes, which, however, can be attenuated by hypoxic preconditioning. Cotransplantation of hUC-MSCs and hUCB-CD34(+) cells can improve heart function and decrease collagen deposition in post-MI rabbits. Thus, a combined regimen of hUC-MSCs and hUCB-CD34(+) cells would be more desirable than either cells administered alone. This is most likely due to the increase of cardiomyocytes and enhanced angiogenesis in the infarcted myocardium.

N-Cadherin is a prospective cell surface marker of human mesenchymal stem cells that have high ability for cardiomyocyte differentiation

Mesenchymal stem cells (MSCs) are among the most promising sources of stem cells for regenerative medicine. However, the range of their differentiation ability is very limited. In this study, we explored prospective cell surface markers of human MSCs that readily differentiate into cardiomyocytes. When the cardiomyogenic differentiation potential and the expression of cell surface markers involved in heart development were analyzed using various immortalized human MSC lines, the MSCs with high expression of N-cadherin showed a higher probability of differentiation into beating cardiomyocytes. The differentiated cardiomyocytes expressed terminally differentiated cardiomyocyte-specific markers such as α-actinin, cardiac troponin T, and connexin-43. A similar correlation was observed with primary human MSCs derived from bone marrow and adipose tissue. Moreover, N-cadherin-positive MSCs isolated with N-cadherin antibody-conjugated magnetic beads showed an apparently higher ability to differentiate into cardiomyocytes than the N-cadherin-negative population. Quantitative polymerase chain reaction analyses demonstrated that the N-cadherin-positive population expressed significantly elevated levels of cardiomyogenic progenitor-specific transcription factors, including Nkx2.5, Hand1, and GATA4 mRNAs. Our results suggest that N-cadherin is a novel prospective cell surface marker of human MSCs that show a better ability for cardiomyocyte differentiation.

MePR: a novel human mesenchymal progenitor model with characteristics of pluripotency

Human embryo stem cells or adult tissues are excellent models for discovery and characterization of differentiation processes. The aims of regenerative medicine are to define the molecular and physiological mechanisms that govern stem cells and differentiation. Human mesenchymal stem cells (hMSCs) are multipotent adult stem cells that are able to differentiate into a variety of cell types under controlled conditions both in vivo and in vitro, and they have the remarkable ability of self-renewal. hMSCs derived from amniotic fluid and characterized by the expression of Oct-4 and Nanog, typical markers of pluripotent cells, represent an excellent model for studies on stemness. Unfortunately, the limited amount of cells available from each donation and, above all, the limited number of replications do not allow for detailed studies. Here, we report on the immortalization and characterization of novel mesenchymal progenitor (MePR) cell lines from amniotic fluid-derived hMSCs, whose biological properties are similar to primary amniocytes. Our data indicate that MePR cells display the multipotency potential and differentiation rates of hMSCs, thus representing a useful model to study both mechanisms of differentiation and pharmacological approaches to induce selective differentiation. In particular, MePR-2B cells, which carry a bona fide normal karyotype, might be used in basic stem cell research, leading to the development of new approaches for stem cell therapy and tissue engineering.

Establishment of Immortalized Human Amniotic Mesenchymal Stem Cells

Human amniotic mesenchymal cells (HAM cells) are known to contain somatic stem cells possessing the characteristics of pluripotency. However, little is known about the biology of these somatic cells because isolated HAM cells from amniotic membrane have a limited lifespan. To overcome this problem, we attempted to prolong the lifespan of HAM cells by infecting retrovirus encoding human papillomavirus type16E6 and E7 (HPV16E6E7), bmi-1, and/or human telomerase reverse transcriptase (hTERT) genes and investigated their characteristics as stem cells. We confirmed the immortalization of the four lines of cultured HAM cells for about 1 year. Immortalized human amnion mesenchymal cells (iHAM cells) have continued to proliferate over 200 population doublings (PDs). iHAM cells were positive for CD73, CD90, CD105, and CD44 and negative for CD34, CD14, CD45, and HLA-DR. They expressed stem cell markers such as Oct3/4, Sox2, Nanog, Klf4, SSEA4, c-myc, vimentin, and nestin. They showed adipogenic, osteogenic, and chondrogenic differentiation abilities after induction. These results suggested that immortalized cell lines with characteristics of stem cells can be established. iHAM cells with an extended lifespan can be used to produce good experimental models both in vitro and in vivo.

Establishment and characterization of immortalized human amniotic epithelial cells

Human amniotic epithelial cells (HAEs) have a low immunogenic profile and possess potent immunosuppressive properties. HAEs also have several characteristics similar to stem cells, and they are discarded after parturition. Thus, they could potentially be used in cell therapy with fewer ethical problems. HAEs have a short life, so our aim is to establish and characterize immortalized human amniotic epithelial cells (iHAEs). HAEs were introduced with viral oncogenes E6/E7 and with human telomerase reverse transcriptase (hTERT) to create iHAEs. These iHAEs have proliferated around 200 population doublings (PDs) for at least 12 months. High expression of stem cell markers (Oct 3/4, Nanog, Sox2, Klf4) and epithelial markers (CK5, CK18) were detected by immunohistochemistry and reverse transcription polymerase chain reaction (RT-PCR). These iHAEs were expanded in ultra-low-attachment dishes to form spheroids similarly to epithelial stem/precursor cells. High expression of mesenchymal (CD44, CD73, CD90, CD105) and somatic (CD24, CD29, CD271, Nestin) stem cell markers was detected by flow cytometry. The iHAEs showed adipogenic, osteogenic, neuronal, and cardiac differentiation abilities. In conclusion, the immortalization of HAEs with the characteristics of stem cells has been established, allowing these iHAEs to become useful for cell therapy and regenerative medicine.

Chondrogenic differentiation of immortalized human mesenchymal stem cells on zirconia microwell substrata

Human mesenchymal stem cells (hMSCs) that can differentiate into chondrocytes are a potential autologous cell source for repair of damaged tissue. Current methods usually induce the formation of all three chondrocyte phenotypes, hyaline, fibrous, and elastic, without the ability to selectively induce only one of them. By controlling the size of hMSC cell clusters, it may be possible to direct differentiation more uniformly toward hyaline chondrocytes. We designed new cell culture platforms containing microwells of different diameters. The platforms and wells were composed of a zirconia ceramics substratum. hMSCs briefly adhered to the substratum before releasing and entering the microwells. The physical restraints imposed by the microwells enabled hMSC clusters to homogenously differentiate into hyaline chondrocyte-like cells. Chondrogenic aggregates in microwells expressed the hyaline chondrocyte-specific genes Col II, aggrecan (ACAN), and cartilage oligomeric protein (COMP). The cultures also produced hyaline chondrocyte-specific matrix proteins Col II and ACAN homogenously throughout the aggregates. In contrast, chondrogenesis in pellet cultures was heterogeneous with the expression of nonhyaline chondrocyte genes CD105, Col X, and Col I. In these pellet cultures, hyaline and nonhyaline chondrocyte-specific matrix proteins were distributed heterogeneously. Thus, this novel ceramic microwell substratum technology efficiently directed the differentiation of hyaline chondrocyte-like cells from hMSCs. These results indicate that there is a close relationship between hMSC cluster size regulation in the microwells and differentiation tendency. This microwell culture differentiation method will provide a valuable experimental system for both experimental and potential clinical studies.

Reawakening atlas: chemical approaches to repair or replace dysfunctional musculature

Muscle diseases are major health concerns. For example, ischemic heart disease is the third most common cause of death. Cell therapy is an attractive approach for treating muscle diseases, although this is hampered by the need to generate large numbers of functional muscle cells. Small molecules have become established as attractive tools for modulating cell behavior and, in this review, we discuss the recent, rapid research advances made in the development of small molecule methods to facilitate the production of functional cardiac, skeletal, and smooth muscle cells. We also describe how new developments in small molecule strategies for muscle disease aim to induce repair and remodelling of the damaged tissues in situ. Recent progress has been made in developing small molecule cocktails that induce skeletal muscle regeneration, and these are discussed in a broader context, because a similar phenomenon occurs in the early stages of salamander appendage regeneration. Although formidable technical hurdles still remain, these new advances in small molecule-based methodologies should provide hope that cell therapies for patients suffering from muscle disease can be developed in the near future.

Differentiation of human umbilical cord mesenchymal stem cells into hepatocyte-like cells by hTERT gene transfection in vitro

The availability of a large quantity of MSCs (mesenchymal stem cells) would greatly advance liver-directed cell therapies. However, MSCs have a limited lifespan in vitro. Therefore we tested whether hUCMSCs (human umbilical cord MSCs) could be immortalized by transduction with a lentiviral vector carrying the hTERT (human telomerase reverse transcriptase) catalytic subunit gene, and investigated their differentiation potential. Transfected hUCMSCs overexpressed the hTERT gene and up-regulated their telomerase activity. The transfected hUCMSCs maintained their typical morphology and MSC-specific markers, and vigorously proliferated, undergoing more than 100 PDs (population doublings) to date. Following incubation with hepatogenic agents, the transfected hUCMSCs differentiated into hepatocyte-like cells, and expressed hepatic markers, such as albumin, AFP (α-fetoprotein) and CK-18 (cytokeratin-18). Transfected hUCMSCs showed no transformation into tumours in nude mice. In conclusion, telomerization of hUCMSCs by hTERT overexpression extends their replicative lifespan without influencing their hepatogenic differentiation potential. This offers opportunities for obtaining sufficient quantities of cells for liver-directed therapies.

Treatment of human mesenchymal stem cells with angiotensin receptor blocker improved efficiency of cardiomyogenic transdifferentiation and improved cardiac function via angiogenesis

To improve the modest efficacy of mesenchymal stem cell (MSC) transplantation, the treatment of human MSCs with angiotensin receptor blockers (ARBs) was investigated. MSCs were cultured with or without the medium containing 3 μmol/l of ARBs before cardiomyogenic induction. After cardiomyogenic induction in vitro, cardiomyogenic transdifferentiation efficiency (CTE) was calculated by immunocytochemistry using anticardiac troponin-I antibody. In the nude rat chronic myocardial infarction model, we injected MSCs pretreated with candesartan (A-BM; n = 18) or injected MSCs without pretreatment of candesartan (BM; n = 25), each having survived for 2 weeks. The left ventricular function, as measured by echocardiogram, was compared with cardiomyogenic transdifferentiation in vivo, as determined by immunohistochemistry. Pretreatment with ARBs significantly increased the CTE in vitro (10.1 ± 0.8 n = 12 vs. 4.6 ± 0.3% n = 25, p < .05). Transplantation of candesartan-pretreated MSCs significantly improved the change in left ventricular ejection fraction (BM; -7.2 ± 2.0 vs. A-BM; 3.3 ± 2.3%). Immunohistochemistry revealed significant improvement of cardiomyogenic transdifferentiation in A-BM in vivo (BM; 0 ± 0 vs. A-BM; 0.014 ± 0.006%). Transplantation of ARB-pretreated MSCs significantly improved cardiac function and can be a promising cardiac stem cell source from which to expect cardiomyogenesis.

Pretreatment of human mesenchymal stem cells with pioglitazone improved efficiency of cardiomyogenic transdifferentiation and cardiac function

The efficacy of transplantation of default human marrow-derived mesenchymal stem cells (MSCs) was modest. In this study, our challenge was to improve the efficacy of MSC transplantation in vivo by pretreatment of MSCs with pioglitazone. MSCs were cultured with or without medium containing 1 μM of pioglitazone before cardiomyogenic induction. After cardiomyogenic induction in vitro, cardiomyogenic transdifferentiation efficiency (CTE) was calculated by immunocytochemistry using anti-cardiac troponin-I antibody. For the in vivo experiments, myocardial infarction (MI) at the anterior left ventricle was made in nude rats. Two weeks after MI, MSCs pretreated with pioglitazone (p-BM; n = 30) or without pioglitazone (BM; n = 17) were injected, and then survived for 2 weeks. We compared left ventricular function by echocardiogram and immunohistochemistry to observe cardiomyogenic transdifferentiation in vivo. Pretreatment with pioglitazone significantly increased the CTE in vitro (1.9% ± 0.2% n = 47 vs. 39.5% ± 4.7% n = 13, p < .05). Transplantation of pioglitazone pretreated MSCs significantly improved change in left ventricular % fractional shortening (BM; -4.8% ± 2.1%, vs. p-BM; 5.2% ± 1.5%). Immunohistochemistry revealed significant improvement of cardiomyogenic transdifferentiation in p-BM in vivo (BM; 0% ± 0% n = 5, vs. p-BM; 0.077% ± 0.041% n = 5). Transplantation of pioglitazone-pretreated MSCs significantly improved cardiac function and can be a promising cardiac stem cell source to expect cardiomyogenesis.

Effects of age on parathyroid hormone signaling in human marrow stromal cells

Human bone marrow stromal cells (hMSCs) have the potential to differentiate into osteoblasts; there are age-related decreases in their proliferation and differentiation to osteoblasts. Parathyroid hormone (PTH), when applied intermittently in vivo, has osteoanabolic effects in a variety of systems. In this study, we compared PTH signaling and osteoanabolic effects in hMSCs from young and old subjects. There were age-related decreases in expression of PTH/PTHrP receptor type 1 (PTHR1) gene (P = 0.049, n = 19) and in PTH activation of CREB (P = 0.029, n = 7) and PTH stabilization of β-catenin (P = 0.018, n = 7). Three human PTH peptides, PTH1-34, PTH1-31C (Ostabolin-C, Leu(27) , Cyclo[Glu(22) -Lys(26) ]-hPTH1-31), and PTH1-84 (10 nm), stimulated osteoblast differentiation with hMSCs. Treatment with PTH1-34 resulted in a significant 67% increase in alkaline phosphatase activity in hMSCs obtained from younger subjects (<50 years old, n = 5), compared with an 18% increase in hMSCs from elders (>55 years old, n = 7). Both knockdown of CREB and treatment with a protein kinase A inhibitor H-89 blocked PTH stimulation of osteoblast differentiation in hMSCs from young subjects. The PTH peptides significantly stimulated proliferation of hMSCs. Treatment with PTH1-34 resulted in an average of twice as many cells in cultures of hMSCs from young subjects (n = 4), but had no effect with hMSCs from elders (n = 7). Upregulation of PTHR1 by 24-h pretreatment with 100 nm dexamethasone rescued PTH stimulation of proliferation in hMSCS from elders. In conclusion, age-related intrinsic alterations in signaling responses to osteoanabolic agents like PTH may contribute to cellular and tissue aging of the human skeleton.

Cardiac cell therapy and arrhythmias

Cardiac stem cell based therapy is a promising therapy for patients with severe heart failure. Many types of stem cells, such as embryonic stem cells, myoblasts, marrow-derived mesenchymal stem cells, circulating endothelial progenitor cells, and cardiac precursor cells etc, are known as cellular sources for cardiac stem cell therapy. Both in the clinical and experimental setting, stem cells are reported, and supposed, to cause some arrhythmogenic adverse effects. In order to overcome these serious adverse effects, it is necessary to know the electrophysiological properties of stem cell-derived cardiomyocytes, and have a profound insight into the mechanisms of arrhythmia to know whether such arrhythmogenic properties of the cells can cause serious arrhythmia in situ. In the present study, recent publications that focus on the electrophysiological aspect of stem cell based therapy are reviewed and, furthermore, a new perspective on cardiac stem cell therapy of arrhythmias is given.

The HPB-AML-I cell line possesses the properties of mesenchymal stem cells

Background

In spite of its establishment from the peripheral blood of a case with acute myeloid leukemia (AML)-M1, HPB-AML-I shows plastic adherence with spindle-like morphology. In addition, lipid droplets can be induced in HPB-AML-I cells by methylisobutylxanthine, hydrocortisone, and indomethacin. These findings suggest that HPB-AML-I is similar to mesenchymal stem cells (MSCs) or mesenchymal stromal cells rather than to hematopoietic cells.

Methods

To examine this possibility, we characterized HPB-AML-I by performing cytochemical, cytogenetic, and phenotypic analyses, induction of differentiation toward mesenchymal lineage cells, and mixed lymphocyte culture analysis.

Results

HPB-AML-I proved to be negative for myeloperoxidase, while surface antigen analysis disclosed that it was positive for MSC-related antigens, such as CD29, CD44, CD55, CD59, and CD73, but not for CD14, CD19, CD34, CD45, CD90, CD105, CD117, and HLA-DR. Karyotypic analysis showed the presence of complicated abnormalities, but no reciprocal translocations typically detected in AML cases. Following the induction of differentiation toward adipocytes, chondrocytes, and osteocytes, HPB-AML-I cells showed, in conjunction with extracellular matrix formation, lipid accumulation, proteoglycan synthesis, and alkaline phosphatase expression. Mixed lymphocyte culture demonstrated that CD3⁺ T-cell proliferation was suppressed in the presence of HPB-AML-I cells.

Conclusions

We conclude that HPB-AML-I cells appear to be unique neoplastic cells, which may be derived from MSCs, but are not hematopoietic progenitor cells.

Biologic function and clinical potential of telomerase and associated proteins in cardiovascular tissue repair and regeneration

Telomeres comprise long tracts of double-stranded TTAGGG repeats that extend for 9-15 kb in humans. Telomere length is maintained by telomerase, a specialized ribonucleoprotein that prevents the natural ends of linear chromosomes from undergoing inappropriate repair, which could otherwise lead to deleterious chromosomal fusions. During the development of cardiovascular tissues, telomerase activity is strong but diminishes with age in adult hearts. Dysfunction of telomerase is associated with the impairment of tissue repair or regeneration in several pathologic conditions, including heart failure and infarction. Under both physiologic and pathophysiologic conditions, telomerase interacts with promyogenic nuclear transcription factors (e.g. myocardin, serum response factor) to augment the potency of cardiovascular cells during growth, survival, and differentiation. We review recent findings on the biologic function of telomerase and its potential for clinical application in cardiovascular development and repair. Understanding the roles of telomerase and its associated proteins in the functional regulation of cardiovascular cells and their progenitors may lead to new strategies for cardiovascular tissue repair and regeneration.

A microfabricated scaffold induces the spheroid formation of human bone marrow-derived mesenchymal progenitor cells and promotes efficient adipogenic differentiation

Here, we report the highly efficient in vitro differentiation of human bone marrow-derived mesenchymal stem/progenitor cells (MPCs) using a novel nanotechnology-based culture plate, nanoculture plate(®) (NCP). The NCP contains uneven microfabrications with diameters of ∼2-3 μm arranged in a honeycomb pattern on its culture surface, which is devoid of animal-derived protein sources. When human MPCs were subjected to three-dimensional (3D) culture using an NCP, they rapidly formed adhesive spheroids. We showed that adipogenic differentiation in NCP-mediated 3D cultures led to more rapid accumulation of triglycerides than that in two-dimensional cultures. During adipogenesis in 3D cultures, the rapid and intense induction of adipocyte-specific gene expressions, such as peroxisome proliferator-activated receptor γ (PPAR-γ), CCAAT-enhancer-binding protein α (C/EBP-α), adipocyte protein 2 (aP2), and adiponectin was observed. Together, these results indicate that this 3D culture system is suitable for the differentiation of human MPCs into adipogenic lineage, and could be applicable to adipose tissue engineering under xeno-free condition.

Serum-independent cardiomyogenic transdifferentiation in human endometrium-derived mesenchymal cells

Media with high concentrations of serum are commonly used to induce cardiomyogenic transdifferentiation in mesenchymal stem cells; however, serum contains numerous unknown growth factors and interferes with definition of specific cardiomyogenic transdifferentiation factors secreted from feeder cells. In the present study, we determined whether the transdifferentiation of human mesenchymal cells can be observed in a FBS-free medium. The efficiency of transdifferentiation was observed in 10% FBS-containing standard medium (10%FBS) and in FBS-free medium containing insulin and thyroxin (FBS-free). In the present study, we used human uterine endometrium-derived mesenchymal cells (EMC100, EMC214) and menstrual blood-derived mesenchymal cells (MMCs). After cardiomyogenic transdifferentiation, the efficiency and physiological properties of cardiomyogenesis (fractional shortening of the cell [%FS] and action potential [AP]) were evaluated. The efficiency of transdifferentiation in EMC100 and in MMCs increased 36%* and 163%* (*P < 0.05), respectively. The %FS in EMCs increased to 103%*. AP-duration more than 250 ms with a marked plateau was only observed in FBS-free (3/19), and not in 10% FBS (0/41). The cardiomyogenic transdifferentiation of human mesenchymal cells can be observed in the FBS-free medium. Phenotypes of generated cardiomyocytes were significantly more physiological in FBS-free than in 10% FBS.

Xenografted human amniotic membrane-derived mesenchymal stem cells are immunologically tolerated and transdifferentiated into cardiomyocytes

RATIONALE

Amniotic membrane is known to have the ability to transdifferentiate into multiple organs and is expected to stimulate a reduced immunologic reaction.

OBJECTIVE

Determine whether human amniotic membrane-derived mesenchymal cells (hAMCs) can be an ideal allograftable stem cell source for cardiac regenerative medicine.

METHODS AND RESULTS

We established hAMCs. After cardiomyogenic induction in vitro, hAMCs beat spontaneously, and the calculated cardiomyogenic transdifferentiation efficiency was 33%. Transplantation of hAMCs 2 weeks after myocardial infarction improved impaired left ventricular fractional shortening measured by echocardiogram (34+/-2% [n=8] to 39+/-2% [n=11]; P<0.05) and decreased myocardial fibrosis area (18+/-1% [n=9] to 13+/-1% [n=10]; P<0.05), significantly. Furthermore hAMCs transplanted into the infarcted myocardium of Wistar rats were transdifferentiated into cardiomyocytes in situ and survived for more than 4 weeks after the transplantation without using any immunosuppressant. Immunologic tolerance was caused by the hAMC-derived HLA-G expression, lack of MHC expression of hAMCs, and activation of FOXP3-positive regulatory T cells. Administration of IL-10 or progesterone, which is known to play an important role in feto-maternal tolerance during pregnancy, markedly increased HLA-G expression in hAMCs in vitro and, surprisingly, also increased cardiomyogenic transdifferentiation efficiency in vitro and in vivo.

CONCLUSIONS

Because hAMCs have a high ability to transdifferentiate into cardiomyocytes and to acquire immunologic tolerance in vivo, they can be a promising cellular source for allograftable stem cells for cardiac regenerative medicine.

Derivation of multipotent progenitors from human circulating CD14+ monocytes

Circulating CD14(+) monocytes are originated from hematopoietic stem cells in the bone marrow and believed to be committed precursors for phagocytes, such as macrophages. Recently, we have reported a primitive cell population termed monocyte-derived multipotential cells (MOMCs), which has a fibroblast-like morphology in culture and a unique phenotype positive for CD14, CD45, CD34, and type I collagen. MOMCs are derived from circulating CD14(+) monocytes, but circulating precursors for MOMCs still remain undetermined. Comparative analysis of gene expression profiles of MOMCs and other monocyte-derived cells has revealed that embryonic stem cell markers, Nanog and Oct-4, are specifically expressed by MOMCs. In vitro generation of MOMCs requires binding to fibronectin and exposure to soluble factors derived from activated platelets. MOMCs contain progenitors with capacity to differentiate into a variety of nonphagocytes, including bone, cartilage, fat, skeletal and cardiac muscle, neuron, and endothelium, indicating that circulating monocytes are more multipotent than previously thought. In addition, MOMCs are capable of promoting ex vivo expansion of human hematopoietic progenitor cells through direct cell-to-cell contact and secretion of a variety of hematopoietic growth factors. These findings obtained from the research on MOMCs indicate that CD14(+) monocytes in circulation are involved in a variety of physiologic functions other than innate and acquired immune responses, such as repair and regeneration of the damaged tissue.

Differential effect of myocardial matrix and integrins on cardiac differentiation of human mesenchymal stem cells

Dysregulation of matrix synthesis during myocardial fibrosis in post-infarct ventricular remodeling contributes to ventricular dysfunction. Bone marrow stem cell transplantation prevents functional deterioration following myocardial infarction. However, effect of myocardial extracellular matrix (ECM) on stem cell differentiation is poorly understood. We investigate the role of collagen matrices and integrin system in cardiac differentiation and engraftment of stem cells in infarcted myocardium. Sternum-derived bone marrow mesenchymal stem cells (MSCs) were differentiated into cardiomyocyte-like cells (CLCs). They were characterized using RT-PCR, immunofluorescence, flow cytometry and functional integrin neutralization assays. CLCs were injected into peri-infarct borders of injured myocardium of Wistar rats one week following left anterior descending (LAD) artery ligation. Cardiac function was analyzed via pressure-volume relationships. Cardiac differentiated CLCs displayed collagen V specificity, which was absent in undifferentiated MSCs. Collagen V, but not collagen I matrix, promoted attachment, proliferation and cardiac differentiation of CLCs. In contrast to beta(1), alpha(v) integrin contributed minimally in the attachment of CLCs on collagen matrices. However, inhibition of alpha(v)beta(3,) but not alpha(2)beta(1) integrin, selectively attenuated troponin T, sarcomeric alpha-actin and ryanodine 2 receptor gene expression in CLCs. Both MSC and CLC transplantation prevented chamber dilatation and improved contractile function. However, systolic activity in MSC transplanted animals was accompanied by heightened wall stress as demonstrated by elevated myocardial end-diastolic pressure and prolonged tissue relaxation time. Localization of CLCs in the vicinity of collagen V-expressing myofibers promoted their integration into cardiac syncytium. CLCs may facilitate hemodynamic recovery by preserving tissue elasticity in the peri-infarct borders that sustains contractile efficiency for functional recovery in an actively remodeling infarcted myocardium.

ES, iPS, MSC, and AFS cells. Stem cells exploitation for Pediatric Surgery: current research and perspective

Despite the advancements that have been made in treating infants with congenital malformations, these still represent a major cause of disease and death during the first years of life and childhood. Regeneration of natural tissue from living cells to restore damaged tissues and organs is the main purpose of regenerative medicine. This relatively new field has emerged by the combination of tissue engineering and stem cell transplantation as a possible strategy for the replacement of damaged organs or tissues. This review would like to offer an insight on the latest evolution of stem cells with a glance at their possible application for regenerative medicine, particularly in the Paediatric Surgery field.

Bone repair by transplantation of hTERT-immortalized human mesenchymal stem cells in mice

BACKGROUND

Human mesenchymal stem cells (hMSCs) are multipotent stem cells found in the adult bone marrow that have the capacity to differentiate into various mesenchymal cell types. The hMSCs may provide a potential therapy to restore damaged tissues or organs of mesenchymal origin; however, a drawback is their limited life span in vitro.

METHODS

We immortalized normal hMSCs with retrovirally transmitted human telomerase reverse transcriptase cDNA. One of the immortalized clones (YKNK-12) was established, and the biological characteristics were investigated in vitro and in vivo.

RESULTS

YKNK-12 cells were capable of differentiating adipocytes, osetoblasts, and chondrocytes. Osteogenically differentiated YKNK-12 cells produced significant levels of growth factors BMP4, BMP6, FGF6, FGF7, transforming growth factor-beta1, and transforming growth factor-beta3.. Microcomputer tomography T and soft X-ray assays showed an excellent calvarial bone healing in mice after transplantation of osteogenically differentiated YKNK-12 cells. These cells expressed human-specific osteocalcin and increased the gene expression of runt-related transcription factor 2, alkaline phosphatase, osteocalcin, and osterix in the bone regenerating area. YKNK-12 cell transplant corrected the bone defect without inducing any adverse effects.

CONCLUSIONS

We conclude that hMSCs immortalized by transduction with human telomerase reverse transcriptase may provide an unlimited source of cells for therapeutic use in bone regeneration.

A comprehensive review on mesenchymal stem cell growth and senescence

In recent years mesenchymal stem cells (MSCs) have generated a great deal of excitement as an attractive alternative to embryonic stem cells (ESCs) in cell-based regenerative medicine. In contrast to cells of embryonic origin, however, the clinical application of MSCs is heavily restricted by their finite ability of self-renewal, in which they resemble the rest of the somatic cells. Yet the mechanisms controlling MSC proliferation and senescence remain unclear. This review summarizes recent advances in our understanding of the factors affecting MSC expansion in vitro and discusses the pattern of their senescence with particular emphasis on the role of telomere shortening, activation of effectory pathways, and oxidative stress. The issues associated with MSC growth and senescence will be shown in the context of other somatic cells, and all of the parallels and disparities will be delineated precisely.

Expression localization of Bmi1 in mice testis

B cell-specific Moloney murine leukaemia virus integration site 1 (Bmi1), known as the first functional member of PcG (Polycomb Group) family, is supposed to be a key regulator of stem cell self-proliferation. In this study, we investigated its expression in testis and its impact on spermatogonia proliferation for better understanding of its role in spermatogenesis. Results showed that Bmi1 was expressed in undifferentiated spermatogonia (A(s), A(pr) and A(al) spermatogonia). Overexpression of BMI1 could promote spermatogonia proliferation, while repression of endogenous Bmi1 by RNAi resulted in inhibition of the proliferation.