Spontaneous expression of embryonic factors and p53 point mutations in aged mesenchymal stem cells: a model of age-related tumorigenesis in mice

Revisiting the role of mesenchymal stromal cells in cancer initiation, metastasis and immunosuppression

Immune checkpoint blockade (ICB) necessitates a thorough understanding of intricate cellular interactions within the tumor microenvironment (TME). Mesenchymal stromal cells (MSCs) play a pivotal role in cancer generation, progression, and immunosuppressive tumor microenvironment. Within the TME, MSCs encompass both resident and circulating counterparts that dynamically communicate and actively participate in TME immunosurveillance and response to ICB. This review aims to reevaluate various facets of MSCs, including their potential self-transformation to function as cancer-initiating cells and contributions to the creation of a conducive environment for tumor proliferation and metastasis. Additionally, we explore the immune regulatory functions of tumor-associated MSCs (TA-MSCs) and MSC-derived extracellular vesicles (MSC-EVs) with analysis of potential connections between circulating and tissue-resident MSCs. A comprehensive understanding of the dynamics of MSC-immune cell communication and the heterogeneous cargo of tumor-educated versus naïve MSCs may unveil a new MSC-mediated immunosuppressive pathway that can be targeted to enhance cancer control by ICB.

Serine Metabolism Regulates the Replicative Senescence of Human Dental Pulp Cells through Histone Methylation

Tissue regeneration therapy based on human dental pulp cells (hDPCs) faces the distinct challenge of cellular senescence during massive expansion in vitro. To further explore the regulatory mechanism of cellular senescence in hDPCs, we conduct experiments on young cells (Passage 5, P5) and replicative senescent (Passage 12, P12) hDPCs. The results confirm that hDPCs undergo replicative senescence with passaging, during which their ability to proliferate and osteogenic differentiation decreases. Notably, during replicative senescence, phosphoglycerate dehydrogenase (PHGDH), the key enzyme of the serine synthesis pathway (SSP), is significantly downregulated, as well as S-adenosylmethionine (SAM) levels, resulting in reduced H3K36me3 modification on Sirtuin 1 (SIRT1)and Runt-related transcription factor 2 (RUNX2) promoters. Inhibition of PHGDH leads to the same phenotype as replicative senescence. Serine supplementation fails to rescue the senescence phenotype caused by replicative senescence and inhibitors, in which folate metabolism-related genes, including serine hydroxymethyl transferase 2 (SHMT2), methylenetetrahydrofolate dehydrogenase 1(MTHFD1), methylenetetrahydrofolate dehydrogenase 2(MTHFD2), are notably decreased. Our research raised a possibility that PHGDH may be involved in cellular senescence by affecting folate metabolism and histone methylation in addition to serine biosynthesis, providing potential targets to prevent senescence.

Stem Cell-Based Tissue Engineering Approaches for Diabetic Foot Ulcer: a Review from Mechanism to Clinical Trial

Diabetic foot ulcer (DFU) is a complication from incomplete or prolonged wound healing, at times requires amputation, putting substantial health and socioeconomic burden. Wound healing is a dynamic overlapping process that can be regulated by arrays of molecular factors showing redundancy in function. However, dysregulation in the mechanism of angiogenesis, extra cellular matrix (ECM) formation and immune modulation are the major causes for impair wound healing in hyperglycaemic patients. Despite development of wound care research, there is a lack of well-accepted targeted therapy with multidisciplinary approach for DFU treatment. Stem cell therapy holds a promising outcome both in preclinical and clinical trials because of its ability to promote healing via regeneration and specialized tissue differentiation. Among different types of stem cells, regenerative potential of mesenchymal stem cell (MSC) is well demonstrated in both experimental and clinical trial. Still there is a huge knowledge gap among medical practitioners for deciding the best stem cell source, administration route, and safety. This review strengthens the fact that why stem cell therapy is a promising candidate to treat DFU and cited multiple tissue engineering and biomaterial-based approaches for delivering stem cells and their aftermath paracrine events. Based on the pre-clinical and clinical studies, the review tried to come up with optimum stem cell source and delivery route for the treatment of DFU. At last, the review glances on possible direction to enhance therapeutics strategy for the same, including different approaches like: phytocompounds, exosomes, scaffold geometry, cell preconditioning and licensing etc.

Liver Disease and Cell Therapy: Advances Made and Remaining Challenges

The limited availability of organs for liver transplantation, the ultimate curative treatment for end stage liver disease, has resulted in a growing and unmet need for alternative therapies. Mesenchymal stromal cells (MSCs) with their broad ranging anti-inflammatory and immunomodulatory properties have therefore emerged as a promising therapeutic agent in treating inflammatory liver disease. Significant strides have been made in exploring their biological activity. Clinical application of MSC has shifted the paradigm from using their regenerative potential to one which harnesses their immunomodulatory properties. Reassuringly, MSCs have been extensively investigated for over 30 years with encouraging efficacy and safety data from translational and early phase clinical studies, but questions remain about their utility. Therefore, in this review, we examine the translational and clinical studies using MSCs in various liver diseases and their impact on dampening immune-mediated liver damage. Our key observations include progress made thus far with use of MSCs for clinical use, inconsistency in the literature to allow meaningful comparison between different studies and need for standardized protocols for MSC manufacture and administration. In addition, the emerging role of MSC-derived extracellular vesicles as an alternative to MSC has been reviewed. We have also highlighted some of the remaining clinical challenges that should be addressed before MSC can progress to be considered as therapy for patients with liver disease.

Aged mesenchymal stem cells and inflammation: from pathology to potential therapeutic strategies

Natural ageing of organisms and corresponding age-related diseases result mainly from stem cell ageing and "inflammaging". Mesenchymal stem cells (MSCs) exhibit very high immune-regulating capacity and are promising candidates for immune-related disease treatment. However, the effect of MSC application is not satisfactory for some patients, especially in elderly individuals. With ageing, MSCs undergo many changes, including altered cell population reduction and differentiation ability, reduced migratory and homing capacity and, most important, defective immunosuppression. It is necessary to explore the relationship between the "inflammaging" and aged MSCs to prevent age-related diseases and increase the therapeutic effects of MSCs. In this review, we discuss changes in naturally ageing MSCs mainly from an inflammation perspective and propose some ideas for rejuvenating aged MSCs in future treatments.

Mesenchymal loss of p53 alters stem cell capacity and models human soft tissue sarcoma traits

Soft tissue sarcomas (STSs) are a heterogeneous group of tumors that originate from mesenchymal cells. p53 is frequently mutated in human STS. In this study, we found that the loss of p53 in mesenchymal stem cells (MSCs) mainly causes adult undifferentiated soft tissue sarcoma (USTS). MSCs lacking p53 show changes in stem cell properties, including differentiation, cell cycle progression, and metabolism. The transcriptomic changes and genetic mutations in murine p53-deficient USTS mimic those seen in human STS. Furthermore, single-cell RNA sequencing revealed that MSCs undergo transcriptomic alterations with aging-a risk factor for certain types of USTS-and that p53 signaling decreases simultaneously. Moreover, we found that human STS can be transcriptomically classified into six clusters with different prognoses, different from the current histopathological classification. This study paves the way for understanding MSC-mediated tumorigenesis and provides an efficient mouse model for sarcoma studies.

Latest Advances in 3D Bioprinting of Cardiac Tissues

Cardiovascular diseases (CVDs) are known as the major cause of death worldwide. In spite of tremendous advancements in medical therapy, the gold standard for CVD treatment is still transplantation. Tissue engineering, on the other hand, has emerged as a pioneering field of study with promising results in tissue regeneration using cells, biological cues, and scaffolds. Three-dimensional (3D) bioprinting is a rapidly growing technique in tissue engineering because of its ability to create complex scaffold structures, encapsulate cells, and perform these tasks with precision. More recently, 3D bioprinting has made its debut in cardiac tissue engineering, and scientists are investigating this technique for development of new strategies for cardiac tissue regeneration. In this review, the fundamentals of cardiac tissue biology, available 3D bioprinting techniques and bioinks, and cells implemented for cardiac regeneration are briefly summarized and presented. Afterwards, the pioneering and state-of-the-art works that have utilized 3D bioprinting for cardiac tissue engineering are thoroughly reviewed. Finally, regulatory pathways and their contemporary limitations and challenges for clinical translation are discussed.

Alterations of epigenetic regulators and P53 mutations in murine mesenchymal stem cell cultures: A possible mechanism of spontaneous transformation

BACKGROUND

Recent studies demonstrated the involvement of mesenchymal stem/stromal cells (MSCs) in carcinogenesis, but the molecular mechanism behind this transformation is still obscured.

OBJECTIVE

To screen both the expression levels of polycomb and trithorax epigenetic regulators and TrP53 mutations in early and late MSC culture passages in an attempt to decipher the mechanism of spontaneous transformation.

METHODS

The study was conducted on early and late passages of MSC culture model from C57BL/6J mice. The expression profile of 84 epigenetic regulators was examined using RT2 profiler PCR array. TrP53 mutations in the DNA binding domain was screened. Codons, amino acids positions and the corresponding human variants were detected in P53 sequences.

RESULTS

Sixty-two epigenetic regulators were dysregulated. Abnormalities were detected starting the third passage. Nine regulators were dysregulated in all passages. (C>G) substitution P53 mutation was detected in passage 3 resulting in Ser152Arg substitution. Passages 6, 9, 12 and the last passage showed T>C substitution resulting in Cys235Arg substitution. The last passage had T deletion and A insertion resulting in frame shift mutations changing the p.Phe286Ser and p.Asn103Lys respectively.

CONCLUSION

In vitro expanded MSCs undergo transformation through alteration of epigenetic regulators which results in genomic instability and frequent P53 mutations.

Cancer and stem cells

Being the second leading cause of death globally, cancer has been a long-standing and rapidly evolving focus of biomedical research and practice in the world. A tremendous effort has been made to understand the origin of cancer cells, the formation of cancerous tissues, and the mechanism by which they spread and relapse, but the disease still remains mysterious. Here, we made an attempt to scrutinize evidences that indicate the role of stem cells in tumorigenesis and metastasis, and cancer relapse. We also looked into the influence of cancers on stem cells, which in turn represent a major constituent of tumor microenvironment. Based on current understandings of the properties of (cancer) stem cells and their relation to cancers, we can foresee that novel therapeutic approaches would become the next wave of cancer treatment.

Ganoderic Acid D Protects Human Amniotic Mesenchymal Stem Cells against Oxidative Stress-Induced Senescence through the PERK/NRF2 Signaling Pathway

Aging is an important risk factor in the occurrence of many chronic diseases. Senescence and exhaustion of adult stem cells are considered as a hallmark of aging in organisms. In this study, a senescent human amniotic mesenchymal stem cell (hAMSC) model subjected to oxidative stress was established in vitro using hydrogen peroxide. We investigated the effects of ganoderic acid D (GA-D), a natural triterpenoid compound produced from Ganoderma lucidum, on hAMSC senescence. GA-D significantly inhibited β-galactosidase (a senescence-associated marker) formation, in a dose-dependent manner, with doses ranging from 0.1 μM to 10 μM, without inducing cytotoxic side-effects. Furthermore, GA-D markedly inhibited the generation of reactive oxygen species (ROS) and the expression of p21 and p16 proteins, relieved the cell cycle arrest, and enhanced telomerase activity in senescent hAMSCs. Furthermore, GA-D upregulated the expression of phosphorylated protein kinase R- (PKR-) like endoplasmic reticulum kinase (PERK), peroxidase III (PRDX3), and nuclear factor-erythroid 2-related factor (NRF2) and promoted intranuclear transfer of NRF2 in senescent cells. The PERK inhibitor GSK2656157 and/or the NRF2 inhibitor ML385 suppressed the PERK/NRF2 signaling, which was activated by GA-D. They induced a rebound for the generation of ROS and β-galactosidase-positive cells and attenuated the differentiation capacity. These findings suggest that GA-D retards hAMSC senescence through activation of the PERK/NRF2 signaling pathway and may be a promising candidate for the discovery of antiaging agents.

Ischemia-Induced Multipotent Stem Cells Isolated from Stroke Patients Exhibit Higher Neurogenic Differentiation Potential than Bone Marrow-Derived Mesenchymal Stem Cells

Perivascular areas of the brain harbor multipotent stem cells. We recently demonstrated that after a stroke, brain pericytes exhibit features of multipotent stem cells. Moreover, these ischemia-induced multipotent stem cells (iSCs) are present within ischemic areas of the brain of patients diagnosed with stroke. Although increasing evidence shows that iSCs have traits similar to those of mesenchymal stem cells (MSCs), the phenotypic similarities and differences between iSCs and MSCs remain unclear. In this study, we used iSCs extracted from stroke patients (h-iSCs) and compared their neurogenic potential with that of human MSCs (h-MSCs) in vitro. Microarray analysis, fluorescence-activated cell sorting, immunohistochemistry, and multielectrode array were performed to compare the characteristics of h-iSCs and h-MSCs. Although h-iSCs and h-MSCs had similar gene expression profiles, the percentage expressing the neural stem/progenitor cell marker nestin was significantly higher in h-iSCs than in h-MSCs. Consistent with these findings, h-iSCs, but not h-MSCs, differentiated into electrophysiologically functional neurons. In contrast, although both h-iSCs and h-MSCs were able to differentiate into several mesodermal lineages, including adipocytes, osteocytes, and chondrocytes, the potential of h-iSCs to differentiate into adipocytes and osteocytes was relatively low. These results suggest that compared with h-MSCs, h-iSCs predominantly exhibit neural rather than mesenchymal lineages. In addition, these results indicate that h-iSCs have the potential to repair the injured brain of patients with stroke by directly differentiating into neuronal lineages.

Epidemiology and Risk Factors of Osteosarcoma

Osteosarcoma is a rare tumor diagnosed at any age; however younger age is a common risk factor. In addition, multiple factors are believed to contribute to higher rates of osteosarcoma, particularly race and gender. Although diagnosed worldwide, osteosarcoma is found to be more prevalent in Africa with high numbers of cases reported in Nigeria, Uganda, and Sudan. Additionally, higher rates are detected in African Americans, suggesting a genetic predisposition linked to race. This review focuses on identifying high risk factors of osteosarcoma with an emphasis on sarcoma epidemiology and risk factors in African countries.

Best Practices for Preclinical In Vivo Testing of Cancer Nanomedicines

Significant advances have been made in the development of nanoparticles for cancer treatment in recent years. Despite promising results in preclinical animal models, cancer nanomedicines often fail in clinical trials. This failure rate could be reduced by defining stringent criteria for testing and quality control during the design and development stages, and by performing carefully planned preclinical studies in relevant animal models. This article discusses best practices for the evaluation of nanomedicines in murine tumor models. First, a recommended set of experiments to perform is introduced, including discussion of the types of data to collect during these studies. This is followed by an outline of various tumor models and their clinical relevance. Next, different routes of nanoparticle administration are overviewed, followed by a summary of important controls to include in in vivo studies of nanomedicine. Finally, animal welfare considerations are discussed, and an overview of the steps involved in achieving US Food and Drug Administration approval after animal studies are completed is provided. Researchers should use this report as a guideline for effective preclinical evaluation of cancer nanomedicine. As the community adopts best practices for in vivo testing, the rate of clinical translation of cancer nanomedicines is likely to improve.

Effects of cryopreservation and long-term culture on biological characteristics and proteomic profiles of human umbilical cord-derived mesenchymal stem cells

Background

Human umbilical cord-derived MSCs (hUC-MSCs) have been identified as promising seeding cells in tissue engineering and clinical applications of regenerative medicine due to their advantages of simple acquisition procedure and the capability to come from a young tissue donor over the other MSCs sources. In clinical applications, large scale production is required and optimal cryopreservation and culture conditions are essential to autologous and allogeneic transplantation in the future. However, the influence of cryopreserved post-thaw and long-term culture on hUC-MSCs remains unknown, especially in terms of specific protein expression. Therefore, biological characteristics and proteomic profiles of hUC-MSCs after cryopreserving and long-term culturing were investigated.

Methods

Firstly, hUC-MSCs were isolated from human umbilical cord tissues and identified through morphology, surface markers and tri-lineage differentiation potential at passage 3, and then the biological characteristics and proteomic profiles were detected and compared after cryopreserving and long-term culturing at passage 4 and continuously cultured to passage 10 with detection occurring here as well. The proteomic profiles were tested by using the isobaric tags for relative and absolute quantification (iTRAQ) labeling technique and differential protein were confirmed by mass spectrometry.

Results

The results showed no significant differences in phenotypes including morphology, surface marker and tri-lineage differentiation potential but have obvious changes in translation level, which is involved in metabolism, cell cycle and other pathways.

Conclusion

This suggests that protein expression may be used as an indicator of hUC-MSCs security testing before applying in clinical settings, and it is also expected to provide the foundation or standardization guide of hUC-MSCs applications in regenerative medicine.

Investigation of Cellular Function and DNA Integrity during 2D in vitro Culture of Human Salivary Gland Epithelial Cells

In vitro culture of human salivary gland epithelial cells (SGEC) is still a challenge. A high quantity and quality of cells are needed for the cultivation of 3D matrices. Furthermore, it is known that DNA damage is supposed to be an important factor involved in carcinogenesis. This study investigates cellular function and DNA integrity of human SGEC during 3 passage steps in 2 groups (group 1: n = 10; group 2: n = 9). Cellular function was analyzed by immunofluorescence, transmission electron microscopy (TEM), and quantitative real-time polymerase chain reaction (qPCR). DNA integrity was tested via the comet assay. Immunohistochemistry and qPCR results showed stable α-amylase and pan-cytokeratin levels; TEM revealed functional cells; and no significant DNA damage could be detected in the comet assay during 3 culture steps. The study shows that not only at cellular but also at DNA level human SGEC can be safely quantified over 3 passages for preclinical tissue engineering without loss of differentiation and function.

Mutant p53 Gain-of-Function: Role in Cancer Development, Progression, and Therapeutic Approaches

Frequent p53 mutations (mutp53) not only abolish tumor suppressor capacities but confer various gain-of-function (GOF) activities that impacts molecules and pathways now regarded as central for tumor development and progression. Although the complete impact of GOF is still far from being fully understood, the effects on proliferation, migration, metabolic reprogramming, and immune evasion, among others, certainly constitute major driving forces for human tumors harboring them. In this review we discuss major molecular mechanisms driven by mutp53 GOF. We present novel mechanistic insights on their effects over key functional molecules and processes involved in cancer. We analyze new mechanistic insights impacting processes such as immune system evasion, metabolic reprogramming, and stemness. In particular, the increased lipogenic activity through the mevalonate pathway (MVA) and the alteration of metabolic homeostasis due to interactions between mutp53 and AMP-activated protein kinase (AMPK) and Sterol regulatory element-binding protein 1 (SREBP1) that impact anabolic pathways and favor metabolic reprograming. We address, in detail, the impact of mutp53 over metabolic reprogramming and the Warburg effect observed in cancer cells as a consequence, not only of loss-of-function of p53, but rather as an effect of GOF that is crucial for the imbalance between glycolysis and oxidative phosphorylation. Additionally, transcriptional activation of new targets, resulting from interaction of mutp53 with NF-kB, HIF-1α, or SREBP1, are presented and discussed. Finally, we discuss perspectives for targeting molecules and pathways involved in chemo-resistance of tumor cells resulting from mutp53 GOF. We discuss and stress the fact that the status of p53 currently constitutes one of the most relevant criteria to understand the role of autophagy as a survival mechanism in cancer, and propose new therapeutic approaches that could promote the reduction of GOF effects exercised by mutp53 in cancer.

Epigenetic changes in fibroblasts drive cancer metabolism and differentiation

Genomic changes that drive cancer initiation and progression contribute to the co-evolution of the adjacent stroma. The nature of the stromal reprogramming involves differential DNA methylation patterns and levels that change in response to the tumor and systemic therapeutic intervention. Epigenetic reprogramming in carcinoma-associated fibroblasts are robust biomarkers for cancer progression and have a transcriptional impact that support cancer epithelial progression in a paracrine manner. For prostate cancer, promoter hypermethylation and silencing of the RasGAP, RASAL3 that resulted in the activation of Ras signaling in carcinoma-associated fibroblasts. Stromal Ras activity initiated a process of macropinocytosis that provided prostate cancer epithelia with abundant glutamine for metabolic conversion to fuel its proliferation and a signal to transdifferentiate into a neuroendocrine phenotype. This epigenetic oncogenic metabolic/signaling axis seemed to be further potentiated by androgen receptor signaling antagonists and contributed to therapeutic resistance. Intervention of stromal signaling may complement conventional therapies targeting the cancer cell.

A Comparison of Phenotypic and Functional Properties of Mesenchymal Stromal Cells and Multipotent Adult Progenitor Cells

Both Multipotent Adult Progenitor Cells and Mesenchymal Stromal Cells are bone-marrow derived, non-haematopoietic adherent cells, that are well-known for having immunomodulatory and pro-angiogenic properties, whilst being relatively non-immunogenic. However, they are phenotypically and functionally distinct cell types, which has implications for their efficacy in different settings. In this review we compare the phenotypic and functional properties of these two cell types, to help in determining which would be the superior cell type for different applications.

Mesenchymal Stromal Cell Therapeutic Delivery: Translational Challenges to Clinical Application

For several decades, multipotent mesenchymal stromal cells (MSCs) have been extensively studied for their therapeutic potential across a wide range of diseases. In the preclinical setting, MSCs demonstrate consistent ability to promote tissue healing, down-regulate excessive inflammation and improve outcomes in animal models. Several proposed mechanisms of action have been posited and demonstrated across an array of in vitro models. However, translation into clinical practice has proven considerably more difficult. A number of prominent well-funded late-phase clinical trials have failed, thus calling out for new efforts to optimize product delivery in the clinical setting. In this review, we discuss novel topics critical to the successful translation of MSCs from pre-clinical to clinical applications. In particular, we focus on the major routes of cell delivery, aspects related to hemocompatibility, and potential safety concerns associated with MSC therapy in the different settings.

Tumor Formation of Adult Stem Cell Transplants in Rodent Arthritic Joints

PURPOSE

While imaging matrix-associated stem cell transplants aimed for cartilage repair in a rodent arthritis model, we noticed that some transplants formed locally destructive tumors. The purpose of this study was to determine the cause for this tumor formation in order to avoid this complication for future transplants.

PROCEDURES

Adipose-derived stem cells (ADSC) isolated from subcutaneous adipose tissue were implanted into 24 osteochondral defects of the distal femur in ten athymic rats and two immunocompetent control rats. All transplants underwent serial magnetic resonance imaging (MRI) up to 6 weeks post-transplantation to monitor joint defect repair. Nine transplants showed an increasing size over time that caused local bone destruction (group 1), while 11 transplants in athymic rats (group 2) and 4 transplants in immunocompetent rats did not. We compared the ADSC implant size and growth rate on MR images, macroscopic features, histopathologic features, surface markers, and karyotypes of these presumed neoplastic transplants with non-neoplastic ADSC transplants.

RESULTS

Implants in group 1 showed a significantly increased two-dimensional area at week 2 (p = 0.0092), 4 (p = 0.003), and 6 (p = 0.0205) compared to week 0, as determined by MRI. Histopathological correlations confirmed neoplastic features in group 1 with significantly increased size, cellularity, mitoses, and cytological atypia compared to group 2. Six transplants in group 1 were identified as malignant chondrosarcomas and three transplants as fibromyxoid sarcomas. Transplants in group 2 and immunocompetent controls exhibited normal cartilage features. Both groups showed a normal ADSC phenotype; however, neoplastic ADSC demonstrated a mixed population of diploid and tetraploid cells without genetic imbalance.

CONCLUSIONS

ADSC transplants can form tumors in vivo. Preventive actions to avoid in vivo tumor formations may include karyotyping of culture-expanded ADSC before transplantation. In addition, serial imaging of ADSC transplants in vivo may enable early detection of abnormally proliferating cell transplants.

A simple and reliable protocol for long-term culture of murine bone marrow stromal (mesenchymal) stem cells that retained their in vitro and in vivo stemness in long-term culture

Background

Bone marrow derived stromal stem cells (BMSCs) are a clonogenic cell population that is characterized by self-renewal capacity and differentiation potential into osteoblasts, and other mesenchymal cell types. Mouse BMSCs (mBMSCs) are difficult to be cultured and propagated in vitro due to their replicative senescent phenotype, heterogeneity and high contamination with plastic adherent hematopoietic progenitors (HPCs). In this study, we described long-term culture of homogenous population of mBMSCs using simple and highly reproducible approach based on frequent subculturing (FS) at fixed split ratio in the presence of basic fibroblast growth factor (bFGF).

Results

Cultured mBMSCs using this protocol (mBMSCs-FS) showed long-term survival in culture > 70 population doubling (PD) and retained their characteristic surface markers and differentiation capacity into osteoblast and adipocyte lineages. When compared to the clonal bone marrow-derived cell line ST2, mBMSCs-FS displayed more enhanced osteoblast differentiation potential and responsiveness to osteogenic factors including BMPs, IGF-1, PDGF, TGFβ1,3, FGF, cAMP, Wnt3a and VEGF. In addition, unlike ST2 cells, mBMSCs-FS maintained capacity to form ectopic bone and bone marrow stroma upon in vivo transplantation in immune-compromising mice, even at high PD levels. Interestingly, by applying the same FS + bFGF protocol, we succeeded to obtain long-term cultures of primary neonatal calvarial osteoprogenitor cells (OBs) that were cultured for more than 70 PD and maintained in vitro and in vivo osteoblast differentiation capacities.

Conclusions

Our data provide a simple and reliable protocol for generating long-term cultures of mBMSCs and OBs with retained high in vitro and in vivo osteoblast differentiation capacities for use in pre-clinical and molecular mechanism studies.

Electronic supplementary material

The online version of this article (10.1186/s12575-019-0091-3) contains supplementary material, which is available to authorized users.

Transplanting Mesenchymal Stem Cells for Treatment of Ischemic Stroke

Stroke is a major disease that leads to high mortality and morbidity. Given the ageing population and the potential risk factors, the prevalence of stroke and socioeconomic burden associated with stroke are expected to increase. During the past decade, both prophylactic and therapeutic strategies for stroke have made significant progress. However, current therapies still cannot adequately improve the outcomes of stroke and may not apply to all patients. One of the significant advances in modern medicine is cell-derived neurovascular regeneration and neuronal repair. Progress in stem cell biology has greatly contributed to ameliorating stroke-related brain injuries in preclinical studies and demonstrated clinical potential in stroke treatment. Mesenchymal stem cells (MSCs) have the differentiating potential of chondrocytes, adipocytes, and osteoblasts, and they have the ability to transdifferentiate into endothelial cells, glial cells, and neurons. Due to their great plasticity, MSCs have drawn much attention from the scientific community. This review will focus on MSCs, stem cells widely utilized in current medical research, and evaluate their effect and potential of improving outcomes in ischemic stroke.

[Integrative analysis of gene expression profile and DNA methylation profile of long-term cultivated porcine bone marrow mesenchymal stem cells]

Objective

To integrate the result of whole genome expression data and whole genome promoter CpG island methylation data, to screen the epigenetic modulated differentially expressed genes from transformed porcine bone marrow mesenchymal stem cells (BMSCs) after long-term cultivation.

Methods

Bone marrow from 6 landrace pigs, 3-month-old about 50 kg weight, was aspirated from the medullary cavity of the proximal tibia. The BMSCs were isolated, and purified by Ficoll density gradient centrifugation combined with adherent culture method. The transfor mation of BMSCs was tested by several methods including cell morphology observation, karyotype analysis, clone forming in soft agarose, serum requirement assay, and tumor forming in mice. The Agilent Pig 4x44k Gene Expression Microarray was used to investigate the differentially expressed mRNA. The methylated genes expression profile was performed using customized pig methylation chip. The gene expression and DNA methylation profiles were integrated to find out the epigenetic modulated differentially expressed genes, and to complete the bioinformatic analysis.

Results

BMSCs showed a change in appearance, from the initial spindle shape to a more flatted morphology then to small contact shape. After additional passages, BMSCs gradually acquired recovery of proliferating capacity and transformation properties such as anchorage-independent growth, chromosomal abnormality, and tumor formation in nude mice. The gene chip analysis demonstrated that 257 genes were upregulated and 315 genes were downregulated during long-term cultures as well as multiple signal pathways transduction involved, such as cell cycle, ECM-receptor interaction, focal adhesion, regulation of actin cytoskeleton, pathways in cancer, and P53. The analysis from methylation chip of coding genes suggested epigenetic regulation was involved in BMSCs spontaneous transformation and play a important role on it; 962 genes were hypermethylated and 1219 genes were hypomethylated, which were involved in the biological process of cellular metabolic, structure, and tumor generation. The combined analysis of genes regulated by methylation in the transformation process of BMSCs found that the methylation changes of the 35 genes were contrary to the direction of expression change (correlation coefficient r=-0.686, P=0.000); in which the methylation level of 21 genes promoter regions were increased while the gene expression decreased, and the methylation level of the 14 genes promoter regions decreased and the gene expression increased. At the same time, KEGG enrichment analysis revealed multiple genes regulated by methylation, involved in stem cell differentiation and multiple cell signaling pathways. Among the 14 down-regulated genes, many of them have the role of regulating the interaction of tumor and immunization, and the change of the methylation status of the CDKN3 promoter region may be closely related to the cell oncology.

Conclusion

The results deepen our understanding of the crucial role of coding genes methylation modification in BMSCs transformation, and may provide new approach to establish safe criteria for BMSCs clinical applications and transformation prevention.

Three-Dimensional Patient-Derived In Vitro Sarcoma Models: Promising Tools for Improving Clinical Tumor Management

Over the past decade, the development of new targeted therapeutics directed against specific molecular pathways involved in tumor cell proliferation and survival has allowed an essential improvement in carcinoma treatment. Unfortunately, the scenario is different for sarcomas, a group of malignant neoplasms originating from mesenchymal cells, for which the main therapeutic approach still consists in the combination of surgery, chemotherapy, and radiation therapy. The lack of innovative approaches in sarcoma treatment stems from the high degree of heterogeneity of this tumor type, with more that 70 different histopathological subtypes, and the limited knowledge of the molecular drivers of tumor development and progression. Currently, molecular therapies are available mainly for the treatment of gastrointestinal stromal tumor, a soft-tissue malignancy characterized by an activating mutation of the tyrosine kinase KIT. Since the first application of this approach, a strong effort has been made to understand sarcoma molecular alterations that can be potential targets for therapy. The low incidence combined with the high level of histopathological heterogeneity makes the development of clinical trials for sarcomas very challenging. For this reason, preclinical studies are needed to better understand tumor biology with the aim to develop new targeted therapeutics. Currently, these studies are mainly based on in vitro testing, since cell lines, and in particular patient-derived models, represent a reliable and easy to handle tool for investigation. In the present review, we summarize the most important models currently available in the field, focusing in particular on the three-dimensional spheroid/organoid model. This innovative approach for studying tumor biology better represents tissue architecture and cell–cell as well as cell–microenvironment crosstalk, which are fundamental steps for tumor cell proliferation and survival.

Multipotent stromal cells/mesenchymal stem cells and fibroblasts combine to minimize skin hypertrophic scarring

Background

Transplantation of mesenchymal stem cells (MSC) has been proposed to improve wound healing. However, as these cells only transiently survive in the implantation site, the mechanisms underlying this beneficial healing response are associated with restorative paracrine effects of MSC matricellular factors on resident stromal cells. However, this requires that the recipient has a robust reservoir of viable cells. Here, we examine the influence of MSCs on the behavior of cotransplanted fibroblasts, in a manner to provide augmented cellular reserve to debilitated individuals, specifically focusing on matrix remodeling following in-vivo wounding.

Methods

Using a Hylan-A dermal filler hydrogel containing collagen I and tenascin-C for delivery and increased survival of transplanted cells, we find that cotransplantation of MSCs with fibroblasts reduces scarring.

Results

Transplanted xenogeneic MSCs augmented fibroblast proliferation, migration, and extracellular matrix deposition critical for wound closure, and reduced inflammation following wounding. MSCs also corrected matrix remodeling by CXCR3-deficient fibroblasts which otherwise led to hypertrophic scarring. This effect was superior to MSC or fibroblast transplantation alone.

Conclusions

Taken together, these data suggest that MSCs, even if eventually rejected, transplanted with fibroblasts normalize matrix regeneration during healing. The current study provides insight into cellular therapies as a viable method for antifibrotic treatment and demonstrates that even transiently engrafted cells can have a long-term impact via matrix modulation and education of other tissue cells.

Genetically transforming human osteoblasts to sarcoma: development of an osteosarcoma model

Osteosarcoma is the most common primary malignant bone tumor in children and young adults. Although histologically defined by the presence of malignant osteoid, the tumor possesses lineage multipotency suggesting it could be derived from a cell anywhere on the differentiation pathway between a mesenchymal stem cell (MSC) and a mature osteoblast. To determine if preosteoblasts (pOB) could be the cell of origin differentiated MSCs were transformed with defined genetic elements. MSCs and pOB differentiated from the same MSCs were serially transformed with the oncogenes hTERT, SV40 large T antigen and H-Ras. Assays were performed to determine their tumorigenic properties, differentiation capacity and histologic appearance. When subcutaneously implanted in immunocompromised mice, cell lines derived from transformed MSC and pOB formed tumors in 4 weeks. In contrast to the transformed MSC, the pOB tumors demonstrated a histological appearance characteristic of osteosarcoma. The cell lines derived from the transformed pOB only had osteogenic and chondrogenic differentiation potential, but not adipogenic ones. However, the transformed MSC cells and standard osteosarcoma cell lines maintained their tri-lineage differentiation capacity. The inability of the transformed pOB cell line to undergo adipogenic differentiation, may suggest that osteosarcoma is derived from a cell intermediate in differentiation between an MSC and a pOB, with partial commitment to the osteoblastic lineage.

Cell therapy for heart disease after 15 years: Unmet expectations

Over the past two decades cardiac cell therapy (CCT) has emerged as a promising new strategy to cure heart diseases at high unmet need. Thousands of patients have entered clinical trials for acute or chronic heart conditions testing different cell types, including autologous or allogeneic bone marrow (BM)-derived mononuclear or selected cells, BM- or adipose tissue-derived mesenchymal cells, or cardiac resident progenitors based on their potential ability to regenerate scarred or dysfunctional myocardium. Nowadays, the original enthusiasm surrounding the regenerative medicine field has been cushioned by a cumulative body of evidence indicating an inefficient or modest efficacy of CCT in improving cardiac function, along with the continued lack of indisputable proof for long-term prognostic benefit. In this review, we have firstly comprehensively outlined the positive and negative results of cell therapy studies in patients with acute myocardial infarction, refractory angina and chronic heart failure. Next, we have discussed cell therapy- and patient-related variables (e.g. cell intrinsic and extrinsic characteristics as well as criteria of patient selection and proposed methodologies) that might have dampened the efficacy of past cell therapy trials. Finally, we have addressed critical factors to be considered before embarking on further clinical trials.

β-Catenin Accumulation Is Associated With Increased Expression of Nanog Protein and Predicts Maintenance of MSC Self-Renewal

Human mesenchymal stem cells (hMSCs) are self-renewing cells with the ability to differentiate into organized, functional network of cells. Recent studies have revealed that activation of the Wnt/β-catenin pathway by a glycogen synthase kinase (GSK)-3-specific pharmacological inhibitor, Bio, results in the maintenance of self-renewal in both mouse and human ES cells. The molecular mechanism behind the maintenance of hMSCs by these factors, however, is not fully understood. We found that rEGF enhances the level of β-catenin, a component of the Wnt/β-catenin signaling pathway. Furthermore, it was found that β-catenin upregulates Nanog. EGF activates the β-catenin pathway via the Ras protein and also increased the Nanog protein and gene expression levels 2 h after rEGF treatment. These results suggest that adding EGF can enhance β-catenin and Nanog expression in MSCs and facilitate EGF-mediated maintenance of MSC self-renewal. EGF was shown to augment MSC proliferation while preserving early progenitors within MSC population and thus did not induce differentiation. Thus, EGF not only can be used to expand MSC in vitro but also be utilized to autologous transplantation of MSCs in vivo.

Means of enhancing bone fracture healing: optimal cell source, isolation methods and acoustic stimulation

BACKGROUND

The human body has an extensive capacity to regenerate bone tissue after trauma. However large defects such as long bone fractures of the lower limbs cannot be restored without intervention and often lead to nonunion. Therefore, the aim of the present study was to assess the pool and biological functions of human mesenchymal stromal cells (hMSCs) isolated from different bone marrow locations of the lower limbs and to identify novel strategies to prime the cells prior to their use in bone fracture healing. Following, bone marrow from the ilium, proximal femur, distal femur and proximal tibia was aspirated and the hMSCs isolated. Bone marrow type, volume, number of mononuclear cells/hMSCs and their self-renewal, multilineage potential, extracellular matrix (ECM) production and surface marker profiling were analyzed. Additionally, the cells were primed to accelerate bone fracture healing either by using acoustic stimulation or varying the initial hMSCs isolation conditions.

RESULTS

We found that the more proximal the bone marrow aspiration location, the larger the bone marrow volume was, the higher the content in mononuclear cells/hMSCs and the higher the self-renewal and osteogenic differentiation potential of the isolated hMSCs were. Acoustic stimulation of bone marrow, as well as the isolation of hMSCs in the absence of fetal bovine serum, increased the osteogenic and ECM production potential of the cells, respectively.

CONCLUSION

We showed that bone marrow properties change with the aspiration location, potentially explaining the differences in bone fracture healing between the tibia and the femur. Furthermore, we showed two new priming methods capable of enhancing bone fracture healing.

The Role of Hypoxia and Cancer Stem Cells in Renal Cell Carcinoma Pathogenesis

The cancer stem cell (CSC) model has recently been approached also in renal cell carcinoma (RCC). A few populations of putative renal tumor-initiating cells (TICs) were identified, but they are indifferently understood; however, the first and most thoroughly investigated are CD105-positive CSCs. The article presents a detailed comparison of all renal CSC-like populations identified by now as well as their presumable origin. Hypoxic activation of hypoxia-inducible factors (HIFs) contributes to tumor aggressiveness by multiple molecular pathways, including the governance of immature stem cell-like phenotype and related epithelial-to-mesenchymal transition (EMT)/de-differentiation, and, as a result, poor prognosis. Due to intrinsic von Hippel-Lindau protein (pVHL) loss of function, clear-cell RCC (ccRCC) develops unique pathological intra-cellular pseudo-hypoxic phenotype with a constant HIF activation, regardless of oxygen level. Despite satisfactory evidence concerning pseudo-hypoxia importance in RCC biology, its influence on putative renal CSC-like largely remains unknown. Thus, the article discusses a current knowledge of HIF-1α/2α signaling pathways in the promotion of undifferentiated tumor phenotype in general, including some experimental findings specific for pseudo-hypoxic ccRCC, mostly dependent from HIF-2α oncogenic functions. Existing gaps in understanding both putative renal CSCs and their potential connection with hypoxia need to be filled in order to propose breakthrough strategies for RCC treatment.

Umbilical cord-derived mesenchymal stem cells alleviate liver fibrosis in rats

AIM: To evaluate the efficacy of umbilical cord-derived mesenchymal stem cells (UC-MSCs) transplantation in the treatment of liver fibrosis.

METHODS: Cultured human UC-MSCs were isolated and transfused into rats with liver fibrosis induced by dimethylnitrosamine (DMN). The effects of UC-MSCs transfusion on liver fibrosis were then evaluated by histopathology; serum interleukin (IL)-4 and IL-10 levels were also measured. Furthermore, Kupffer cells (KCs) in fibrotic livers were isolated and cultured to analyze their phenotype. Moreover, UC-MSCs were co-cultured with KCs in vitro to assess the effects of UC-MSCs on KCs’ phenotype, and IL-4 and IL-10 levels were measured in cell culture supernatants. Finally, UC-MSCs and KCs were cultured in the presence of IL-4 antibodies to block the effects of this cytokine, followed by phenotypical analysis of KCs.

RESULTS: UC-MSCs transfused into rats were recruited by the injured liver and alleviated liver fibrosis, increasing serum IL-4 and IL-10 levels. Interestingly, UC-MSCs promoted mobilization of KCs not only in fibrotic livers, but also in vitro. Co-culture of UC-MSCs with KCs resulted in increased production of IL-4 and IL-10. The addition of IL-4 antibodies into the co-culture system resulted in decreased KC mobilization.

CONCLUSION: UC-MSCs could increase IL-4 and promote mobilization of KCs both in vitro and in vivo, subsequently alleviating the liver fibrosis induced by DMN.

Rebuilding the Damaged Heart: Mesenchymal Stem Cells, Cell-Based Therapy, and Engineered Heart Tissue

Mesenchymal stem cells (MSCs) are broadly distributed cells that retain postnatal capacity for self-renewal and multilineage differentiation. MSCs evade immune detection, secrete an array of anti-inflammatory and anti-fibrotic mediators, and very importantly activate resident precursors. These properties form the basis for the strategy of clinical application of cell-based therapeutics for inflammatory and fibrotic conditions. In cardiovascular medicine, administration of autologous or allogeneic MSCs in patients with ischemic and nonischemic cardiomyopathy holds significant promise. Numerous preclinical studies of ischemic and nonischemic cardiomyopathy employing MSC-based therapy have demonstrated that the properties of reducing fibrosis, stimulating angiogenesis, and cardiomyogenesis have led to improvements in the structure and function of remodeled ventricles. Further attempts have been made to augment MSCs' effects through genetic modification and cell preconditioning. Progression of MSC therapy to early clinical trials has supported their role in improving cardiac structure and function, functional capacity, and patient quality of life. Emerging data have supported larger clinical trials that have been either completed or are currently underway. Mechanistically, MSC therapy is thought to benefit the heart by stimulating innate anti-fibrotic and regenerative responses. The mechanisms of action involve paracrine signaling, cell-cell interactions, and fusion with resident cells. Trans-differentiation of MSCs to bona fide cardiomyocytes and coronary vessels is also thought to occur, although at a nonphysiological level. Recently, MSC-based tissue engineering for cardiovascular disease has been examined with quite encouraging results. This review discusses MSCs from their basic biological characteristics to their role as a promising therapeutic strategy for clinical cardiovascular disease.

Preclinical Biosafety Evaluation of Genetically Modified Human Adipose Tissue-Derived Mesenchymal Stem Cells for Clinical Applications to Brainstem Glioma

Stem-cell based gene therapy is a promising novel therapeutic approach for inoperable invasive tumors, including brainstem glioma. Previously, we demonstrated the therapeutic potential of human adipose tissue-derived mesenchymal stem cells (hAT-MSC) genetically engineered to express a secreted form of tumor necrosis factor-related apoptosis-inducing ligand (sTRAIL) against brainstem glioma. However, safety concerns should be comprehensively investigated before clinical applications of hAT-MSC.sTRAIL. At first, we injected stereotactically low (1.2 × 10(5) cells/18 μL), medium (2.4 × 10(5)/18 μL), or high dose (3.6 × 10(5)/18 μL) of hAT-MSC.sTRAIL into the brainstems of immunodeficient mice reflecting the plan of the future clinical trial. Local toxicity, systemic toxicity, secondary tumor formation, and biodistribution of hAT-MSC.sTRAIL were investigated. Next, presence of hAT-MSC.sTRAIL was confirmed in the brain and major organs at 4, 9, and 14 weeks in brainstem glioma-bearing mice. In the 15-week subchronic toxicity test, no serious adverse events in terms of body weight, food consumption, clinical symptom, urinalysis, hematology, clinical chemistry, organ weight, and histopathology were observed. In the 26-week tumorigenicity test, hAT-MSC.sTRAIL made no detectable tumors, whereas positive control U-87 MG cells made huge tumors in the brainstem. No remaining hAT-MSC.sTRAIL was observed in any organs examined, including the brainstem at 15 or 26 weeks. In brainstem glioma-bearing mice, injected hAT-MSC.sTRAIL was observed, but gradually decreased over time in the brain. The mRNA of human specific GAPDH and TRAIL was not detected in all major organs. These results indicate that the hAT-MSC.sTRAIL could be applicable to the future clinical trials in terms of biosafety.

Current Biosafety Considerations in Stem Cell Therapy

Stem cells can be valuable model systems for drug discovery and modelling human diseases as well as to investigate cellular interactions and molecular events in the early stages of development. Controlling the differentiation of stem cells into specific germ layers provides a potential source of highly specialized cells for therapeutic applications. In recent years, finding individual properties of stem cells such as their ultimate self-renewal capacity and the generation of particular cell lines by differentiation under specific culture conditions underpins the development of regenerative therapies. These futures make stem cells a leading candidate to treat a wide range of diseases. Nevertheless, as with all novel treatments, safety issues are one of the barriers that should be overcome to guarantee the quality of a patient's life after stem cell therapy. Many studies have pointed to a large gap in our knowledge about the therapeutic applications of these cells. This gap clearly shows the importance of biosafety concerns for the current status of cell-based therapies, even more than their therapeutic efficacy. Currently, scientists report that tumorigenicity and immunogenicity are the two most important associated cell-based therapy risks. In principle, intrinsic factors such as cell characteristics and extrinsic elements introduced by manufacturing of stem cells can result in tumor formation and immunological reactions after stem cell transplantation. Therapeutic research shows there are many biological questions regarding safety issues of stem cell clinical applications. Stem cell therapy is a rapidly advancing field that needs to focus more on finding a comprehensive technology for assessing risk. A variety of risk factors (from intrinsic to extrinsic) should be considered for safe clinical stem cell therapies.

Loss of interactions between p53 and survivin gene in mesenchymal stem cells after spontaneous transformation in vitro

Mesenchymal stem cells (MSC) from various animals undergo a spontaneous transformation in long-term culture. The transformed MSCs are highly tumorigenic and are likely to be the tumor-initiating cells of sarcoma. To explain why the transformed MSCs become tumorigenic, the present study investigated the characteristics of rat MSCs before and after spontaneous transformation. It was shown that although the transformed MSCs maintained typical surface markers of MSC, they exhibited some cancer stem cell-like characteristics such as loss of contact inhibition and multi-potency to mesenchymal lineages, and acquirement of ability of anchorage-independent growth. The expression of a key senescence regulator p16 almost disappeared, but the other one, p53 abnormally increased in the transformed MSCs. ChIP assay demonstrated that a normal negative regulation of p53 on survivin gene disappeared in the transformed cells due to a lack of p53 binding to the promoter of survivin gene. DNA sequencing revealed that the p53 gene in transformed MSCs was not a wild-type, but a 942C>T mutant with the mutation located in the sequence coding p53 protein's DNA-binding domain. These findings indicate that the transformed MSCs express high levels of a p53 mutant that loses the ability to bind survivin gene, leading to an abnormally upregulated expression of survivin, which is a key reason for the cell's unlimited proliferation.

Isolation of Mouse Bone Marrow Mesenchymal Stem Cells

Mesenchymal stem cells (MSCs) were initially characterized as connective tissue progenitors resident in bone marrow, but have now been isolated from a variety of tissues and organs and shown to also exhibit potent tissue regenerative properties mediated largely via paracrine actions. These findings have spurred the development of MSC-based therapies for treating a diverse array of nonskeletal diseases. Although genetic and experimental rodent models of disease represent important tools for developing efficacious MSC-based therapies, development of reliable methods to isolate MSCs from mouse bone marrow has been hampered by the unique biological properties of these cells. Indeed, few isolation schemes afford high yields and purity while maintaining the genomic integrity of cells. We recently demonstrated that mouse MSCs are highly sensitive to oxidative stress, and long-term expansion of these cells in atmospheric oxygen selects for immortalized clones that lack a functional p53 protein. Herein, we describe a protocol for the isolation of primary MSCs from mouse bone marrow that couples immunodepletion with culture in a low-oxygen environment and affords high purity and yield while preserving p53 function.

Malignant transformation of bone marrow stromal cells induced by the brain glioma niche in rats

Normal human embryonic stem cells (hESCs) can develop neoplastic cancer stem cell (CSC) properties after coculture with transformed hESCs in vitro. In the present study, the influence of the tumor microenvironment on malignant transformation of bone marrow stromal cells (BMSCs) was studied after allografting a mixture of enhanced green fluorescent protein (EGFP)-labeled BMSCs and C6 glioma cells into the rat brain to understand the influence of the cellular environment, especially the tumor environment, on the transformation of grafted BMSCs in the rat brain. We performed intracerebral transplantation in the rat brain using EGFP-labeled BMSCs coinjected with C6 tumor cells. After transplantation, the EGFP-labeled cells were isolated from the tumor using fluorescence-activated cell sorting, and the characteristics of the recovered cells were investigated. Glioma-specific biomarkers of the sorted cells and the biological characteristics of the tumors were analyzed. The BMSCs isolated from the cografts were transformed into glioma CSCs, as indicated by the marked expression of the glioma marker GFAP in glioma cells, and of Nestin and CD133 in neural stem cells and CSCs, as well as rapid cell growth, decreased level of the tumor suppressor gene p53, increased level of the oncogene murine double minute gene 2 (MDM2), and recapitulation of glioma tissues in the brain. These data suggest that BMSCs can be transformed into CSCs, which can be further directed toward glioma formation under certain conditions, supporting the notion that the tumor microenvironment is involved in transforming normal BMSCs into glial CSCs.

The potential of mesenchymal stem cells in the management of radiation enteropathy

Although radiotherapy is effective in managing abdominal and pelvic malignant tumors, radiation enteropathy is still unavoidable. This disease severely affects the quality of life of cancer patients due to some refractory lesions, such as intestinal ischemia, mucositis, ulcer, necrosis or even perforation. Current drugs or prevailing therapies are committed to alleviating the symptoms induced by above lesions. But the efficacies achieved by these interventions are still not satisfactory, because the milieus for tissue regeneration are not distinctly improved. In recent years, regenerative therapy for radiation enteropathy by using mesenchymal stem cells is of public interests. Relevant results of preclinical and clinical studies suggest that this regenerative therapy will become an attractive tool in managing radiation enteropathy, because mesenchymal stem cells exhibit their pro-regenerative potentials for healing the injuries in both epithelium and endothelium, minimizing inflammation and protecting irradiated intestine against fibrogenesis through activating intrinsic repair actions. In spite of these encouraging results, whether mesenchymal stem cells promote tumor growth is still an issue of debate. On this basis, we will discuss the advances in anticancer therapy by using mesenchymal stem cells in this review after analyzing the pathogenesis of radiation enteropathy, introducing the advances in managing radiation enteropathy using regenerative therapy and exploring the putative actions by which mesenchymal stem cells repair intestinal injuries. At last, insights gained from the potential risks of mesenchymal stem cell-based therapy for radiation enteropathy patients may provide clinicians with an improved awareness in carrying out their studies.

Mesenchymal stem cell aging: Mechanisms and influences on skeletal and non-skeletal tissues

The aging population and the incidence of aging-related diseases such as osteoporosis are on the rise. Aging at the tissue and organ levels usually involves tissue stem cells. Human and animal model studies indicate that aging affects two aspects of mesenchymal stem cell (MSC): a decrease in the bone marrow MSC pool and biased differentiation into adipocyte at the cost of osteoblast, which underlie the etiology of osteoporosis. Aging of MSC cells is also detrimental to some non-skeletal tissues, in particular the hematopoietic system, where MSCs serve as a niche component. In addition, aging compromises the therapeutic potentials of MSC cells, including cells isolated from aged individuals or cells cultured for many passages. Here we discuss the recent progress on our understanding of MSC aging, with a focus on the effects of MSC aging on bone remodeling and hematopoiesis and the mechanisms of MSC aging.

A shorter telomere is the key factor in preventing cultured human mesenchymal stem cells from senescence escape

Mesenchymal stem cells (MSCs) from various animals undergo spontaneous transformation in vitro,establishing some malignant characteristics. However,this phenomenon seems seldom appearing in human (h)MSCs. To address the question whether the hMSCs really do not undergo the spontaneous transformation and why,the present study compared MSCs from two species under the same conditions, the commercialized primary hMSCs whose in vitro life span is very uniform, and the rat (r)MSCs whose spontaneous transformation in vitro is well defined.It was demonstrated that in rMSCs, there were small numbers of re-proliferating cells appearing after a substantial senescent period. These “senescence-escaped”rMSCs were highly proliferative and did not show any sign of growth arrest during the following subcultures upto observed passage 32. Whereas after entering senescence, hMSCs no longer re-proliferated and finally died from apoptosis. Compared with rMSCs, the hMSCs possessed a much shorter telomere, and lacked both telomerase reverse transcriptase expression and telomerase activity. When proliferating from pre-senescent to senescent stages,the hMSCs had a greater loss of relative telomere length(51 % in hMSC vs. 15 % in rMSC), but both cells displayed a similar average telomere shortening per population doubling (0.50 ± 0.06 kb in rMSC vs. 0.49 ± 0.06 kbin hMSC; p > 0.05), indicating that the greater relative shortening of the hMSC telomeres was due to their original shorter length, rather than lack of telomere maintenance mechanisms. In conclusion, the hMSCs do not spontaneously initiate transformation, because they cannot escape senescence. This is particularly due to their much shorter telomere.

The potential use of mesenchymal stem cells in stroke therapy--From bench to bedside

Stroke is the second main cause of morbidity and mortality worldwide. The rationale for the use of mesenchymal stem cells (MSCs) in stroke is based on the capacity of MSCs to secrete a large variety of bioactive molecules such as growth factors, cytokines and chemokines leading to reduction of inflammation, increased neurogenesis from the germinative niches of central nervous system, increased angiogenesis, effects on astrocytes, oligodendrocytes and axons. This review presents the data derived from experimental studies and the evidence available from clinical trials about the use of MSCs in stroke therapy.

Alteration of histone acetylation pattern during long-term serum-free culture conditions of human fetal placental mesenchymal stem cells

Increasing evidence suggests that the mesenchymal stem cells (MSCs) derived from placenta of fetal origin (fPMSCs) are superior to MSCs of other sources for cell therapy. Since the initial number of isolated MSCs is limited, in vitro propagation is often required to reach sufficient numbers of cells for therapeutic applications, during which MSCs may undergo genetic and/or epigenetic alterations that subsequently increase the probability of spontaneous malignant transformation. Thus, factors that influence genomic and epigenetic stability of MSCs following long-term expansions need to be clarified before cultured MSCs are employed for clinical settings. To date, the genetic and epigenetic stability of fPMSCs after long-term in vitro expansion has not been fully investigated. In this report, alterations to histone acetylation and consequence on the expression pattern of fPMSCs following in vitro propagation under serum-free conditions were explored. The results show that fPMSCs maintain their MSC characteristics before they reached a senescent state. Furthermore, acetylation modification patterns were changed in fPMSCs along with gradually increased global histone deacetylase (HDAC) activity and expression of HDAC subtypes HDAC4, HDAC5 and HDAC6, as well as a down-regulated global histone H3/H4 acetylation during in vitro culturing. In line with the acetylation alterations, the expression of oncogenes Oct4, Sox2 and TERT were significantly decreased over the propagation period. Of note, the down-regulation of Oct4 was strongly associated with changes in acetylation. Intriguingly, telomere length in fPMSCs did not significantly change during the propagating process. These findings suggest that human fPMSCs may be a safe and reliable resource of MSCs and can be propagated under serum-free conditions with less risk of spontaneous malignancy, and warrants further validation in clinical settings.

Disease-in-a-dish: the contribution of patient-specific induced pluripotent stem cell technology to regenerative rehabilitation

Advances in regenerative medicine technologies will lead to dramatic changes in how patients in rehabilitation medicine clinics are treated in the upcoming decades. The multidisciplinary field of regenerative medicine is developing new tools for disease modeling and drug discovery based on induced pluripotent stem cells. This approach capitalizes on the idea of personalized medicine by using the patient's own cells to discover new drugs, increasing the likelihood of a favorable outcome. The search for compounds that can correct disease defects in the culture dish is a conceptual departure from how drug screens were done in the past. This system proposes a closed loop from sample collection from the diseased patient, to in vitro disease model, to drug discovery and Food and Drug Administration approval, to delivering that drug back to the same patient. Here, recent progress in patient-specific induced pluripotent stem cell derivation, directed differentiation toward diseased cell types, and how those cells can be used for high-throughput drug screens are reviewed. Given that restoration of normal function is a driving force in rehabilitation medicine, the authors believe that this drug discovery platform focusing on phenotypic rescue will become a key contributor to therapeutic compounds in regenerative rehabilitation.

The role of mesenchymal stem/progenitor cells in sarcoma: update and dispute

Sarcoma is the collective name for a relatively rare, yet heterogeneous group of cancers, most probably derived from mesenchymal tissues. There are currently over 50 sarcoma subtypes described underscoring the clinical and biologic diversity of this group of malignant cancers. This wide lineage range might suggest that sarcomas originate from either many committed different cell types or from a multipotent cell. Mesenchymal stem/progenitor cells (MSCs) are able to differentiate into many cell types and these multipotent cells have been isolated from several adult human tumors, making them available for research as well as potential beneficial therapeutical agents. Recent accomplishments in the field have broadened our knowledge of MSCs in relation to sarcoma origin and sarcoma treatment in therapeutic settings. However, numerous concerns and disputes have been raised about whether they are the putative originating cells of sarcoma and their questionable role in sarcomagenesis and progression. We summarize the update and dispute about MSC investigations in sarcomas including the definition, cell origin hypothesis, functional and descriptive assays, roles in sarcomagenesis and targeted therapy, with the purpose to give a comprehensive view of the role of MSCs in sarcomas.

Fate of graft cells: what should be clarified for development of mesenchymal stem cell therapy for ischemic stroke?

Mesenchymal stem cells (MSCs) are believed to be promising for cell administration therapy after ischemic stroke. Because of their advantageous characteristics, such as ability of differentiation into neurovascular lineages, avoidance of immunological problems, and abundance of graft cells in mesodermal tissues, studies regarding MSC therapy have increased recently. However, several controversies are yet to be resolved before a worldwide consensus regarding a standard protocol is obtained. In particular, the neuroprotective effects, the rate of cell migration to the lesion, and differentiation direction differ depending on preclinical observations. Analyses of these differences and application of recent developments in stem cell biology or engineering in imaging modality may contribute to identification of criteria for optimal stem cell therapy in which reliable protocols, which control cell quality and include safe administration procedures, are defined for each recovery phase after cerebral ischemia. In this mini review, we examine controversies regarding the fate of grafts and the prospects for advanced therapy that could be obtained through recent developments in stem cell research as direct conversion to neural cells.

Mesenchymal stem cells induce epithelial proliferation within the inflamed stomach

Bone marrow-derived mesenchymal stem cells (MSCs) sustain cancer cells by creating a microenvironment favorable for tumor growth. In particular, MSCs have been implicated in gastric cancer development. There is extensive evidence suggesting that Hedgehog signaling regulates tumor growth. However, very little is known regarding the precise roles of Hedgehog signaling and MSCs in tumor development within the stomach. The current study tests that hypothesis that Sonic Hedgehog (Shh), secreted from MSCs, provides a proliferative stimulus for the gastric epithelium in the presence of inflammation. Red fluorescent protein-expressing MSCs transformed in vitro (stMSCs) were transduced with lentiviral constructs containing a vector control (stMSC(vect)) or short hairpin RNA (shRNA) targeting the Shh gene (stMSC(ShhKO)). Gastric submucosal transplantation of wild-type MSCs (wtMSCs), wild-type MSCs overexpressing Shh (wtMSC(Shh)), stMSC(vect), or stMSC(ShhKO) cells in C57BL/6 control (BL/6) or gastrin-deficient (GKO) mice was performed and mice analyzed 30 and 60 days posttransplantation. Compared with BL/6 mice transplanted with wtMSC(Shh) and stMSC(vect) cells, inflamed GKO mice developed aggressive gastric tumors. Tumor development was not observed in mouse stomachs transplanted with wtMSC or stMSC(ShhKO) cells. Compared with stMSC(ShhKO)-transplanted mice, within the inflamed GKO mouse stomach, Shh-expressing stMSC(vect)- and wtMSC(Shh)-induced proliferation of CD44-positive cells. CD44-positive cells clustered in gland-like structures within the tumor stroma and were positive for Patched (Ptch) expression. We conclude that Shh, secreted from MSCs, provides a proliferative stimulus for the gastric epithelium that is associated with tumor development, a response that is sustained by chronic inflammation.