Role of mesenchymal stem cells in regenerative medicine: application to bone and cartilage repair

Cellular therapies in trauma and critical care medicine: Looking towards the future

Shibani Pati and Todd Rasmussen summarize progress in preclinical research on cellular therapeutics for traumatic injury and its sequelae and discuss prospects for clinical translation.

Laminin differentially regulates the stemness of type I and type II pericytes

Background

Laminin, a major basement membrane component that has direct contact with pericytes under physiological conditions, actively regulates the proliferation and differentiation/fate determination of pericytes. Recently, two types of pericytes (type I and type II) with different molecular markers and functions have been identified in skeletal muscles. Whether laminin differentially regulates the proliferation and differentiation of these two subpopulations remains unclear.

Methods

Wild-type and pericytic laminin-deficient mice under Nestin-GFP background were used to determine if laminin differentially regulates the proliferation and differentiation of type I and type II pericytes. Specifically, type I and type II pericytes were isolated from these mice, and their proliferation and differentiation were examined in vitro. Moreover, in vivo studies were also performed.

Results

We demonstrate that, although laminin inhibits the proliferation of both type I and type II pericytes in vitro, loss of laminin predominantly induces proliferation of type II pericytes in vivo. In addition, laminin negatively regulates the adipogenic differentiation of type I pericytes and positively regulates the myogenic differentiation of type II pericytes in vitro.

Conclusions

Laminin differentially regulates the proliferation and differentiation of type I and type II pericytes.

Electronic supplementary material

The online version of this article (doi:10.1186/s13287-017-0479-4) contains supplementary material, which is available to authorized users.

Kupffer cells-dependent inflammation in the injured liver increases recruitment of mesenchymal stem cells in aging mice

Mesenchymal stem cells (MSCs) repair tissue injury and may be used to treat immune associated diseases. In carbon tetrachloride (CCl4)-induced liver injury murine model, we administered MSCs. When MSCs were transmitted to young and old mice with liver injury, more MSCs were recruited in old mice. In old mice, inflammation, characterized by TNF-α and IL-6, was increased due to hyper-activation and hyper-function of Kupffer cells. Blocking Kupffer cells decreased MSCs migration in old mice. In vitro, Kupffer cells isolated from old mice secreted more inflammatory cytokines and chemokines. Thus, hyper-activation of Kupffer cells in old mice increased recruitment of MSCs after their therapeutic administration.

Cellular Therapies in Trauma and Critical Care Medicine: Forging New Frontiers

Trauma is a leading cause of death in both military and civilian populations worldwide. Although medical advances have improved the overall morbidity and mortality often associated with trauma, additional research and innovative advancements in therapeutic interventions are needed to optimize patient outcomes. Cell-based therapies present a novel opportunity to improve trauma and critical care at both the acute and chronic phases that often follow injury. Although this field is still in its infancy, animal and human studies suggest that stem cells may hold great promise for the treatment of brain and spinal cord injuries, organ injuries, and extremity injuries such as those caused by orthopedic trauma, burns, and critical limb ischemia. However, barriers in the translation of cell therapies that include regulatory obstacles, challenges in manufacturing and clinical trial design, and a lack of funding are critical areas in need of development. In 2015, the Department of Defense Combat Casualty Care Research Program held a joint military–civilian meeting as part of its effort to inform the research community about this field and allow for effective planning and programmatic decisions regarding research and development. The objective of this article is to provide a “state of the science” review regarding cellular therapies in trauma and critical care, and to provide a foundation from which the potential of this emerging field can be harnessed to mitigate outcomes in critically ill trauma patients.

The Possible Roles of Biological Bone Constructed with Peripheral Blood Derived EPCs and BMSCs in Osteogenesis and Angiogenesis

This study aimed to determine the possible potential of partially deproteinized biologic bone (PDPBB) seeded with bone marrow stromal cells (BMSCs) and endothelial progenitor cells (EPCs) in osteogenesis and angiogenesis. BMSCs and EPCs were isolated, identified, and cocultured in vitro, followed by seeding on the PDPBB. Expression of osteogenesis and vascularization markers was quantified by immunofluorescence (IF) staining, immunohistochemistry (IHC), and quantitive real-time polymerase chain reaction (qRT-PCR). Scanning electron microscope (SEM) was also employed to further evaluate the morphologic alterations of cocultured cells in the biologic bone. Results demonstrated that the coculture system combined with BMSCs and EPCs had significant advantages of (i) upregulating the mRNA expression of VEGF, Osteonectin, Osteopontin, and Collagen Type I and (ii) increasing ALP and OC staining compared to the BMSCs or EPCs only group. Moreover, IHC staining for CD105, CD34, and ZO-1 increased significantly in the implanted PDPBB seeded with coculture system, compared to that of BMSCs or EPCs only, respectively. Summarily, the present data provided evidence that PDPBB seeded with cocultured system possessed favorable cytocompatibility, provided suitable circumstances for different cell growth, and had the potential to provide reconstruction for cases with bone defection by promoting osteogenesis and angiogenesis.

Immunomodulatory properties of mesenchymal stem cell in experimental arthritis in rat and mouse models: A systematic review

BACKGROUND

Despite recent advances in the treatment of arthritis with the development of disease-modifying antirheumatic drugs, 30% of patients still fail to respond to treatment. Given the potent anti-inflammatory and immunomodulatory properties of mesenchymal stem cells (MSC) and their ability to repair damaged cartilage, bone, and tendons, it has been proposed that MSC could be ideal for cell-based treatment of arthritis.

OBJECTIVE

This systematic review investigates evidence from studies on the therapeutic efficacy of MSC in rodent models of arthritis.

METHODS

PubMed, Embase, MEDLINE, and Wed of Science were searched to June 2015 for quantitative studies examining the outcome of treating animal models of arthritis with MSC. Inclusion criteria were as follows: administration of mesenchymal stem as a treatment approach for arthritis; animal models only; and published in English. We followed the preferred reporting items for systematic reviews and meta-analyses (PRISMA) guidelines.

RESULTS

The literature search identified 30 studies which met the inclusion criteria. A range of MSC populations were assessed in various rodent models of arthritis. Of these, 19 demonstrated positive outcomes while 11 studies failed to demonstrate positive effects. Owing to the extensive variation in the experimental design, cells investigated and the outcome measures described in the manuscripts, no meta-analysis was possible. Furthermore, the numerical values for the primary outcome measure of clinical paw score were frequently not published in the manuscripts analyzed, as they were only illustrated in graphical form.

CONCLUSIONS

Numerous studies have investigated the utility of a range of MSC populations in the treatment of experimental arthritis. The results obtained from these studies have been highly inconsistent, with multiple studies identifying a statistically significant improvement in arthritis scores after treatment with MSC, while other studies identified a statistically significant deterioration in arthritis scores and thirdly some studies showed no effect. Further studies using standardized protocols and outcome measures are needed to determine fully the potential of MSC populations in the treatment of experimental arthritis.

Engineering Stem Cells for Biomedical Applications

Stem cells are characterized by a number of useful properties, including their ability to migrate, differentiate, and secrete a variety of therapeutic molecules such as immunomodulatory factors. As such, numerous pre-clinical and clinical studies have utilized stem cell-based therapies and demonstrated their tremendous potential for the treatment of various human diseases and disorders. Recently, efforts have focused on engineering stem cells in order to further enhance their innate abilities as well as to confer them with new functionalities, which can then be used in various biomedical applications. These engineered stem cells can take on a number of forms. For instance, engineered stem cells encompass the genetic modification of stem cells as well as the use of stem cells for gene delivery, nanoparticle loading and delivery, and even small molecule drug delivery. The present Review gives an in-depth account of the current status of engineered stem cells, including potential cell sources, the most common methods used to engineer stem cells, and the utilization of engineered stem cells in various biomedical applications, with a particular focus on tissue regeneration, the treatment of immunodeficiency diseases, and cancer.

Dendrimer surface orientation of the RGD peptide affects mesenchymal stem cell adhesion

Mesenchymal stem cells (MSCs) are promising candidates for a range of tissue regeneration applications.

Advances of human bone marrow-derived mesenchymal stem cells in the treatment of cartilage defects: a systematic review

Mesenchymal stem cell (MSC)-based therapies represent a new option for treating damaged cartilage. However, the outcomes following its clinical application have seldom been previously compared. The present paper presents the systematic review of current literatures on MSC-based therapy for cartilage repair in clinical applications. Ovid, Scopus, PubMed, ISI Web of Knowledge and Google Scholar online databases were searched using several keywords, which include "cartilage" and "stem cells". Only studies using bone marrow-derived MSC (BM-MSC) to treat cartilage defects clinically were included in this review. The clinical outcomes were compared, and the quality of the tissue repair was analysed where possible. Of the 996 articles, only six (n = 6) clinical studies have described the use of BM-MSC in clinical applications. Two studies were cohort observational trials, three were case series, and one was a case report. In the two comparative trials, BM-MSCs produced superior repair to cartilage treatment without cells and have comparable outcomes to autologous chondrocyte implantation. The case series and case-control studies have demonstrated that use of BM-MSCs resulted in better short- to long-term clinical outcomes with minimal complications. In addition, histological analyses in two studies have resulted in good repair tissue formation at the damaged site, composed mainly of hyaline-like cartilage. Although results of the respective studies are highly indicative that BM-MSC-based therapy is superior, due to the differences in methods and selection criteria used, it was not possible to make direct comparison between the studies. In conclusion, published studies do suggest that BM-MSCs could provide superior cartilage repair. However, due to limited number of reports, more robust studies might be required before a definitive conclusion can be drawn.

Effects of the endocrine-disrupting chemical DDT on self-renewal and differentiation of human mesenchymal stem cells

BACKGROUND

Although the global use of the endocrine-disrupting chemical DDT has decreased, its persistence in the environment has resulted in continued human exposure. Accumulating evidence suggests that DDT exposure has long-term adverse effects on development, yet the impact on growth and differentiation of adult stem cells remains unclear.

OBJECTIVES

Human mesenchymal stem cells (MSCs) exposed to DDT were used to evaluate the impact on stem cell biology.

METHODS

We assessed DDT-treated MSCs for self-renewal, proliferation, and differentiation potential. Whole genome RNA sequencing was performed to assess gene expression in DDT-treated MSCs.

RESULTS

MSCs exposed to DDT formed fewer colonies, suggesting a reduction in self-renewal potential. DDT enhanced both adipogenic and osteogenic differentiation, which was confirmed by increased mRNA expression of glucose transporter type 4 (GLUT4), lipoprotein lipase (LpL), peroxisome proliferator-activated receptor gamma (PPARγ), leptin, osteonectin, core binding factor 1 (CBFA1), and FBJ murine osteosarcoma viral oncogene homolog (c-Fos). Expression of factors in DDT-treated cells was similar to that in estrogen-treated MSCs, suggesting that DDT may function via the estrogen receptor (ER)-mediated pathway. The coadministration of ICI 182,780 blocked the effects of DDT. RNA sequencing revealed 121 genes and noncoding RNAs to be differentially expressed in DDT-treated MSCs compared with controls cells.

CONCLUSION

Human MSCs provide a powerful biological system to investigate and identify the molecular mechanisms underlying the effects of environmental agents on stem cells and human health. MSCs exposed to DDT demonstrated profound alterations in self-renewal, proliferation, differentiation, and gene expression, which may partially explain the homeostatic imbalance and increased cancer incidence among those exposed to long-term EDCs.

Identification and characterization of mesenchymal-epithelial progenitor-like cells in normal and injured rat liver

In normal rat liver, thymocyte antigen 1 (Thy1) is expressed in fibroblasts/myofibroblasts and in some blood progenitor cells. Thy1-expressing cells also accumulate in the liver during impaired liver regeneration. The origin and nature of these cells are not well understood. By using RT-PCR analysis and immunofluorescence microscopy, we describe the presence of rare Thy1(+) cells in the liver lobule of normal animals, occasionally forming small collections of up to 20 cells. These cells constitute a small portion (1.7% to 1.8%) of nonparenchymal cells and reveal a mixed mesenchymal-epithelial phenotype, expressing E-cadherin, cytokeratin 18, and desmin. The most potent mitogens for mesenchymal-epithelial Thy1(+) cells in vitro are the inflammatory cytokines interferon γ, IL-1, and platelet-derived growth factor-BB, which are not produced by Thy1(+) cells. Thy1(+) cells express all typical mesenchymal stem cell and hepatic progenitor cell markers and produce growth factor and cytokine mRNA (Hgf, Il6, Tgfa, and Tweak) for proteins that maintain oval cell growth and differentiation. Under appropriate conditions, mesenchymal-epithelial cells differentiate in vitro into hepatocyte-like cells. In this study, we show that the adult rat liver harbors a small pool of endogenous mesenchymal-epithelial cells not recognized previously. In the quiescent state, these cells express both mesenchymal and epithelial cell markers. They behave like hepatic stem cells/progenitors with dual phenotype, exhibiting high plasticity and long-lasting proliferative activity.

Nestin expression in mesenchymal stromal cells: regulation by hypoxia and osteogenesis

Background

The intermediate filament protein nestin is used as a marker for neural stem cells, and its expression is inversely correlated with cellular differentiation. More recently, nestin expression has also been described in other cell types including multipotential mesenchymal stromal cells (MSCs). In this study, we examined the expression of nestin in equine, canine and human bone marrow-derived MSCs undergoing osteogenic differentiation, to determine whether nestin levels were attenuated as the cells acquired a more mature phenotype. In addition, the expression of nestin may be under the influence of cellular hypoxia, as nestin expression is known to increase in areas of ischemic tissue damage. Therefore, we also examined the effects of hypoxia on expression of nestin in human MSCs and examined a role for hypoxia inducible factor 1-alpha (HIF-1α) and vascular endothelial growth factor (VEGF) in the response. Additionally, we quantified the temporal expression of nestin in the fracture callus during bone regeneration, a site that has been characterized as hypoxic.

Results

There were no significant changes in nestin expression in MSCs during osteogenic differentiation. There was a significant increase in expression of nestin mRNA and protein in human MSCs in response to hypoxia (1% O₂) or the chemical hypoxia mimetic desferroxamine. This may be due to upregulation of VEGF under hypoxia, as treatment of cells with the VEGF receptor antagonist CPO-P11 attenuated hypoxia-induced nestin expression. A significant increase in nestin mRNA expression was observed in the fracture callus of mice three and seven days post fracture.

Conclusions

Nestin was not a selective marker for MSCs, as its expression was maintained during osteogenic differentiation, in all species examined. Furthermore our data suggest that nestin expression can be induced by hypoxia, and that this increase in nestin is partially regulated by HIF-1α and VEGF. Interestingly, nestin levels were significantly upregulated at the fracture site. Further studies are required to understand the role of nestin in bone cell biology and ultimately bone regeneration.

Mesenchymal stem cells as a potent cell source for articular cartilage regeneration

Since articular cartilage possesses only a weak capacity for repair, its regeneration potential is considered one of the most important challenges for orthopedic surgeons. The treatment options, such as marrow stimulation techniques, fail to induce a repair tissue with the same functional and mechanical properties of native hyaline cartilage. Osteochondral transplantation is considered an effective treatment option but is associated with some disadvantages, including donor-site morbidity, tissue supply limitation, unsuitable mechanical properties and thickness of the obtained tissue. Although autologous chondrocyte implantation results in reasonable repair, it requires a two-step surgical procedure. Moreover, chondrocytes expanded in culture gradually undergo dedifferentiation, so lose morphological features and specialized functions. In the search for alternative cells, scientists have found mesenchymal stem cells (MSCs) to be an appropriate cellular material for articular cartilage repair. These cells were originally isolated from bone marrow samples and further investigations have revealed the presence of the cells in many other tissues. Furthermore, chondrogenic differentiation is an inherent property of MSCs noticed at the time of the cell discovery. MSCs are known to exhibit homing potential to the damaged site at which they differentiate into the tissue cells or secrete a wide spectrum of bioactive factors with regenerative properties. Moreover, these cells possess a considerable immunomodulatory potential that make them the general donor for therapeutic applications. All of these topics will be discussed in this review.

Preparation, quality criteria, and properties of human blood platelet lysate supplements for ex vivo stem cell expansion

Most clinical applications of human multipotent mesenchymal stromal cells (MSCs) for cell therapy, tissue engineering, regenerative medicine, and treatment of immune and inflammatory diseases require a phase of isolation and ex vivo expansion allowing a clinically meaningful cell number to be reached. Conditions used for cell isolation and expansion should meet strict quality and safety requirements. This is particularly true for the growth medium used for MSC isolation and expansion. Basal growth media used for MSC expansion are supplemented with multiple nutrients and growth factors. Fetal bovine serum (FBS) has long been the gold standard medium supplement for laboratory-scale MSC culture. However, FBS has a poorly characterized composition and poses risk factors, as it may be a source of xenogenic antigens and zoonotic infections. FBS has therefore become undesirable as a growth medium supplement for isolating and expanding MSCs for human therapy protocols. In recent years, human blood materials, and most particularly lysates and releasates of platelet concentrates have emerged as efficient medium supplements for isolating and expanding MSCs from various origins. This review analyzes the advantages and limits of using human platelet materials as medium supplements for MSC isolation and expansion. We present the modes of production of allogeneic and autologous platelet concentrates, measures taken to ensure optimal pathogen safety profiles, and methods of preparing PLs for MSC expansion. We also discuss the supply of such blood preparations. Produced under optimal conditions of standardization and safety, human platelet materials can become the future 'gold standard' supplement for ex vivo production of MSCs for translational medicine and cell therapy applications.

Thrombospondin-2 secreted by human umbilical cord blood-derived mesenchymal stem cells promotes chondrogenic differentiation

Increasing evidence indicates that the secretome of mesenchymal stem cells (MSCs) has therapeutic potential for the treatment of various diseases, including cartilage disorders. However, the paracrine mechanisms underlying cartilage repair by MSCs are poorly understood. Here, we show that human umbilical cord blood-derived MSCs (hUCB-MSCs) promoted differentiation of chondroprogenitor cells by paracrine action. This paracrine effect of hUCB-MSCs on chondroprogenitor cells was increased by treatment with synovial fluid (SF) obtained from osteoarthritis (OA) patients but was decreased by SF of fracture patients, compared to that of an untreated group. To identify paracrine factors underlying the chondrogenic effect of hUCB-MSCs, the secretomes of hUCB-MSCs stimulated by OA SF or fracture SF were analyzed using a biotin label-based antibody array. Among the proteins increased in response to these two kinds of SF, thrombospondin-2 (TSP-2) was specifically increased in only OA SF-treated hUCB-MSCs. In order to determine the role of TSP-2, exogenous TSP-2 was added to a micromass culture of chondroprogenitor cells. We found that TSP-2 had chondrogenic effects on chondroprogenitor cells via PKCα, ERK, p38/MAPK, and Notch signaling pathways. Knockdown of TSP-2 expression on hUCB-MSCs using small interfering RNA abolished the chondrogenic effects of hUCB-MSCs on chondroprogenitor cells. In parallel with in vitro analysis, the cartilage regenerating effect of hUCB-MSCs and TSP-2 was also demonstrated using a rabbit full-thickness osteochondral-defect model. Our findings suggested that hUCB-MSCs can stimulate the differentiation of locally presented endogenous chondroprogenitor cells by TSP-2, which finally leads to cartilage regeneration.

Cartilage tissue engineering: molecular control of chondrocyte differentiation for proper cartilage matrix reconstruction

BACKGROUND

Articular cartilage defects are a veritable therapeutic problem because therapeutic options are very scarce. Due to the poor self-regeneration capacity of cartilage, minor cartilage defects often lead to osteoarthritis. Several surgical strategies have been developed to repair damaged cartilage. Autologous chondrocyte implantation (ACI) gives encouraging results, but this cell-based therapy involves a step of chondrocyte expansion in a monolayer, which results in the loss in the differentiated phenotype. Thus, despite improvement in the quality of life for patients, reconstructed cartilage is in fact fibrocartilage. Successful ACI, according to the particular physiology of chondrocytes in vitro, requires active and phenotypically stabilized chondrocytes.

SCOPE OF REVIEW

This review describes the unique physiology of cartilage, with the factors involved in its formation, stabilization and degradation. Then, we focus on some of the most recent advances in cell therapy and tissue engineering that open up interesting perspectives for maintaining or obtaining the chondrogenic character of cells in order to treat cartilage lesions.

MAJOR CONCLUSIONS

Current research involves the use of chondrocytes or progenitor stem cells, associated with "smart" biomaterials and growth factors. Other influential factors, such as cell sources, oxygen pressure and mechanical strain are considered, as are recent developments in gene therapy to control the chondrocyte differentiation/dedifferentiation process.

GENERAL SIGNIFICANCE

This review provides new information on the mechanisms regulating the state of differentiation of chondrocytes and the chondrogenesis of mesenchymal stem cells that will lead to the development of new restorative cell therapy approaches in humans. This article is part of a Special Issue entitled Matrix-mediated cell behaviour and properties.

Delivery of growth factors using a smart porous nanocomposite scaffold to repair a mandibular bone defect

Implantation of a porous scaffold with a large volume into the body in a convenient and safe manner is still a challenging task in the repair of bone defects. In this study, we present a porous smart nanocomposite scaffold with a combination of shape memory function and controlled delivery of growth factors. The shape memory function enables the scaffold with a large volume to be deformed into its temporal architecture with a small volume using hot-compression and can subsequently recover its original shape upon exposure to body temperature after it is implanted in the body. The scaffold consists of chemically cross-linked poly(ε-caprolactone) (c-PCL) and hydroxyapatite nanoparticles. The highly interconnected pores of the scaffold were obtained using the sugar leaching method. The shape memory porous scaffold loaded with bone morphogenetic protein-2 (BMP-2) was also fabricated by coating the calcium alginate layer and BMP-2 on the surface of the pore wall. Under both in vitro and in vivo environmental conditions, the porous scaffold displays good shape memory recovery from the compressed shape with deformed pores of 33 μm in diameter to recover its porous shape with original pores of 160 μm in diameter. In vitro cytotoxicity based on the MTT test revealed that the scaffold exhibited good cytocompatibility. The in vivo micro-CT and histomorphometry results demonstrated that the porous scaffold could promote new bone generation in the rabbit mandibular bone defect. Thus, our results indicated that this shape memory porous scaffold demonstrated great potential for application in bone regenerative medicine.

A scalable approach to obtain mesenchymal stem cells with osteogenic potency on apatite microcarriers

Bone tissue engineering, which relies on the interactions between stem cells and suitable scaffold materials, represents a highly desirable alternative to currently used allograft or autograft strategies for the treatment of bone defects caused by injury or disease, with one of the major challenges being to generate sufficient quantities of stem cells to bring about the intended therapeutic effect. However, conventional cell culture to achieve sufficient cell numbers faces limitations of low efficiency and diminished efficacy of stem cells due to repeated passaging. Furthermore, current microcarriers available may not be suitable for therapeutic implantation. Here, the authors featured an apatite-based microcarrier intended for bone tissue engineering applications. These apatite microcarriers have a diameter of ∼230 µm, and exhibited porous and rough surface morphology. Peaks obtained from X-ray diffractometry (XRD) corresponded to hydroxyapatite (HA) with high crystallinity. Fourier transform infrared spectrophotometry (FTIR) showed that no residues of alginate remained, and all bands observed belong to phosphate and hydroxyl groups of HA. To evaluate the cytocompatibility of these microcarriers, in vitro proliferation studies were conducted and compared with conventional monolayer as well as Cytodex 3. The authors found that human foetal mesenchymal stem cells (hfMSCs) cultured on apatite microcarriers exhibited comparable growth characteristics, achieving 1.4-fold higher live cells than Cytodex 3 over a 9-day culture period. As these microcarriers were hypothesised to offer enhanced osteogenic potency over conventional monolayer culture, alkaline phosphatase (ALP), type I collagen and osteocalcin expression of hfMSCs cultured on the apatite microcarriers were evaluated over a 12-day period. ALP expression for hfMSCs seeded on apatite microcarriers was 2.7-fold higher than that of adherent monolayer culture (p < 0.001). Additionally, type I collagen and osteocalcin expression were 1.8- and 1.5-fold higher than that of adherent monolayer culture on day 12, respectively (p < 0.001).

Optimization of the isolation and expansion method of human mediastinal-adipose tissue derived mesenchymal stem cells with virally inactivated GMP-grade platelet lysate

Mesenchymal stem cells (MSCs) are adult multipotent cells currently employed in several clinical trials due to their immunomodulating, angiogenic and repairing features. The adipose tissue is certainly considered an eligible source of MSCs. Recently, putative adipose tissue derived MSCs (ADMSCs) have been isolated from the mediastinal depots. However, very little is known about the properties, the function and the potential of human mediastinal ADMSCs (hmADMSCs). However, the lack of standardized methodologies to culture ADMSCs prevents comparison across. Herein for the first time, we report a detailed step by step description to optimize the isolation and the expansion methodology of hmADMSCs using a virally inactivated good manufacturing practice (GMP)-grade platelet lysate, highlighting the critical aspects of the procedure and providing useful troubleshooting suggestions. Our approach offers a reproducible system which could provide standardization across laboratories. Moreover, our system is time and cost effective, and it can provide a reproducible source of adipose stem cells to enable future studies to unravel new insights regard this promising stem cell population.

Autophagy prevents irradiation injury and maintains stemness through decreasing ROS generation in mesenchymal stem cells

Stem cells were characterized by their stemness: self-renewal and pluripotency. Mesenchymal stem cells (MSCs) are a unique type of adult stem cells that have been proven to be involved in tissue repair, immunoloregulation and tumorigenesis. Irradiation is a well-known factor that leads to functional obstacle in stem cells. However, the mechanism of stemness maintenance in human MSCs exposed to irradiation remains unknown. We demonstrated that irradiation could induce reactive oxygen species (ROS) accumulation that resulted in DNA damage and stemness injury in MSCs. Autophagy induced by starvation or rapamycin can reduce ROS accumulation-associated DNA damage and maintain stemness in MSCs. Further, inhibition of autophagy leads to augment of ROS accumulation and DNA damage, which results in the loss of stemness in MSCs. Our results indicate that autophagy may have an important role in protecting stemness of MSCs from irradiation injury.

Bone regeneration by transplantation of human mesenchymal stromal cells in a rabbit mandibular distraction osteogenesis model

Ex vivo expanded mesenchymal stromal cells (MSCs) represent a potential cell population for tissue regeneration strategy. Xenogeneic transplantation using human MSCs (hMSCs) can be an approach to reveal what hMSCs guide in bone regeneration with distinguishable gene expression from a host animal. In this study, we investigated the regenerating effect of hMSCs varying injection time point in a rabbit distraction osteogenesis model. Undifferentiated hMSCs (2×10(6) cells) were injected transcutaneously into the osteotomy site of one side of the mandible 1 day before the onset of distraction (Group 1) or after distraction (Group 2). The contralateral side of the mandible, which was subjected to distraction, but no hMSC injection, was used as the control in each group. hMSCs showed lack of major histocompatibility complex class II expression and suppression of xenogeneic lymphocyte proliferation stimulated by a proinflammatory cytokine. A microcomputed tomography-based evaluation showed a significant increase in new bone volume in the distracted callus in Group 1 compared to the contralateral side. Injection of hMSCs increased the bone mineral density (BMD) of the regenerated bone in both Group 1 and 2, although the former had a higher BMD than the latter. hMSCs of Group 1 subjected to distraction after injection expressed insulin-like growth factor-1 (IGF-1) and fibronectin (FN), while the expression of most osteoblast differentiation-related markers and growth factors was negligible. These results demonstrated that hMSCs exerted immune suppressive behavior in rabbit T cells in vitro, and hMSC transplantation into the distracted callus of a rabbit model provided osteogenic benefits that were more pronounced when the hMSCs were injected just before distraction than at the end of distraction. The beneficial effect of hMSCs might be mediated, partly by the expression of matrix proteins or IGF-1, which are known to favor bone formation.

Effect of bone marrow mesenchymal stem cells from blastic phase chronic myelogenous leukemia on the growth and apoptosis of leukemia cells

Chronic myelogenous leukemia (CML) has a typical progressive course with transition from a chronic phase to a terminal blast crisis phase. However, the mechanisms that lead to disease progression remain unclear. Bone marrow mesenchymal stem cells (BMMSCs) play important roles in maintaining the bone marrow microenvironment. In the present study, the biological characteristics of BMMSCs were determined including proliferation, apoptosis and secretion of cytokines during blastic phase CML (CML-Bp). The effect of BMMSCs in CML-Bp on K562 human CML cells and the CML-Bp original generation leukemia cells were also explored. Our results showed that CML-Bp BMMSCs protect tumor cells and increase their anti-apoptotic ability through regulating the expression of apoptosis-related proteins and activating the Wnt pathway.

Mesenchymal stem cells: a new trend for cell therapy

Mesenchymal stem cells (MSCs), the major stem cells for cell therapy, have been used in the clinic for approximately 10 years. From animal models to clinical trials, MSCs have afforded promise in the treatment of numerous diseases, mainly tissue injury and immune disorders. In this review, we summarize the recent opinions on methods, timing and cell sources for MSC administration in clinical applications, and provide an overview of mechanisms that are significant in MSC-mediated therapies. Although MSCs for cell therapy have been shown to be safe and effective, there are still challenges that need to be tackled before their wide application in the clinic.

Engineering bone tissue using human dental pulp stem cells and an osteogenic collagen-hydroxyapatite-poly (L-lactide-co-ε-caprolactone) scaffold

The aim of this study was to design a new natural/synthetic bioactive bone scaffold for potential use in bone replacement applications. We developed a tri-component osteogenic composite scaffold made of collagen (Coll), hydroxyapatite (HA) and poly(l-lactide-co-ε-caprolactone) (PLCL). This Coll/HA/PLCL composite scaffold was combined with human osteoblast-like cells obtained by differentiation of dental pulp stem cells (DPSCs) to engineer bone tissue in vitro. Results show that the 3D Coll/HA/PLCL composite scaffold was highly porous, thereby enabling osteoblast-like cell adhesion and growth. Cultured in the Coll/HA/PLCL scaffold, the osteoblast-like cells expressed different osteogenic genes, produced alkaline phosphatase and formed nodules more than did PLCL alone. Micro-CT analyses revealed a significant (30%) increase of tissue mineralisation on the surface as well as inside of the Coll/HA/PLCL scaffold, thus confirming its effectiveness as a bone regeneration platform.

BMP2 genetically engineered MSCs and EPCs promote vascularized bone regeneration in rat critical-sized calvarial bone defects

Current clinical therapies for critical-sized bone defects (CSBDs) remain far from ideal. Previous studies have demonstrated that engineering bone tissue using mesenchymal stem cells (MSCs) is feasible. However, this approach is not effective for CSBDs due to inadequate vascularization. In our previous study, we have developed an injectable and porous nano calcium sulfate/alginate (nCS/A) scaffold and demonstrated that nCS/A composition is biocompatible and has proper biodegradability for bone regeneration. Here, we hypothesized that the combination of an injectable and porous nCS/A with bone morphogenetic protein 2 (BMP2) gene-modified MSCs and endothelial progenitor cells (EPCs) could significantly enhance vascularized bone regeneration. Our results demonstrated that delivery of MSCs and EPCs with the injectable nCS/A scaffold did not affect cell viability. Moreover, co-culture of BMP2 gene-modified MSCs and EPCs dramatically increased osteoblast differentiation of MSCs and endothelial differentiation of EPCs in vitro. We further tested the multifunctional bone reconstruction system consisting of an injectable and porous nCS/A scaffold (mimicking the nano-calcium matrix of bone) and BMP2 genetically-engineered MSCs and EPCs in a rat critical-sized (8 mm) caviarial bone defect model. Our in vivo results showed that, compared to the groups of nCS/A, nCS/A+MSCs, nCS/A+MSCs+EPCs and nCS/A+BMP2 gene-modified MSCs, the combination of BMP2 gene -modified MSCs and EPCs in nCS/A dramatically increased the new bone and vascular formation. These results demonstrated that EPCs increase new vascular growth, and that BMP2 gene modification for MSCs and EPCs dramatically promotes bone regeneration. This system could ultimately enable clinicians to better reconstruct the craniofacial bone and avoid donor site morbidity for CSBDs.

Therapeutic potential of mesenchymal stem cells in regenerative medicine

Mesenchymal stem cells (MSCs) are stromal cells that have the ability to self-renew and also exhibit multilineage differentiation into both mesenchymal and nonmesenchymal lineages. The intrinsic properties of these cells make them an attractive candidate for clinical applications. MSCs are of keen interest because they can be isolated from a small aspirate of bone marrow or adipose tissues and can be easily expanded in vitro. Moreover, their ability to modulate immune responses makes them an even more attractive candidate for regenerative medicine as allogeneic transplant of these cells is feasible without a substantial risk of immune rejection. MSCs secrete various immunomodulatory molecules which provide a regenerative microenvironment for a variety of injured tissues or organ to limit the damage and to increase self-regulated tissue regeneration. Autologous/allogeneic MSCs delivered via the bloodstream augment the titers of MSCs that are drawn to sites of tissue injury and can accelerate the tissue repair process. MSCs are currently being tested for their potential use in cell and gene therapy for a number of human debilitating diseases and genetic disorders. This paper summarizes the current clinical and nonclinical data for the use of MSCs in tissue repair and potential therapeutic role in various diseases.

One cell, multiple roles: contribution of mesenchymal stem cells to tumor development in tumor microenvironment

The discovery of tissue reparative and immunosuppressive abilities of mesenchymal stem cells (MSCs) has drawn more attention to tumor microenvironment and its role in providing the soil for the tumor cell growth. MSCs are recruited to tumor which is referred as the never healing wound and altered by the inflammation environment, thereby helping to construct the tumor microenvironment. The environment orchestrated by MSCs and other factors can be associated with angiogenesis, immunosuppression, inhibition of apoptosis, epithelial-mesenchymal transition (EMT), survival of cancer stem cells, which all contribute to tumor growth and progression. In this review, we will discuss how MSCs are recruited to the tumor microenvironment and what effects they have on tumor progression.

Utilization of transgenic models in the evaluation of osteogenic differentiation of embryonic stem cells

Previous studies reported that embryonic stem cells (ESCs) can be induced to differentiate into cells showing a mature osteoblastic phenotype by culturing them under osteo-inductive conditions. It is probable that osteogenic differentiation requires that ESCs undergo differentiation through an intermediary step involving a mesenchymal lineage precursor. Based on our previous studies indicating that adult mesenchymal progenitor cells express α-smooth muscle actin (αSMA), we have generated ESCs from transgenic mice in which an αSMA promoter directs the expression of red fluorescent protein (RFP) to mesenchymal progenitor cells. To track the transition of ESC-derived MSCs into mature osteoblasts, we have utilized a bone-specific fragment of rat type I collagen promoter driving green fluorescent protein (Col2.3GFP). Following osteogenic induction in ESCs, we have observed expression of alkaline phosphatase (ALP) and subsequent mineralization as detected by von Kossa staining. After 1 week of osteogenic induction, ESCs begin to express αSMARFP. This expression was localized to the peripheral area encircling a typical ESC colony. Nevertheless, these αSMARFP positive cells did not show activation of the Col2.3GFP promoter, even after 7 weeks of osteogenic differentiation in vitro. In contrast, Col2.3GFP expression was detected in vivo, in mineralized areas following teratoma formation. Our results indicate that detection of ALP activity and mineralization of ESCs cultured under osteogenic conditions is not sufficient to demonstrate osteogenic maturation. Our study indicates the utility of the promoter-visual transgene approach to assess the commitment and differentiation of ESCs into the osteoblast lineage.

Mesenchymal stem cells facilitate fracture repair in an alcohol-induced impaired healing model

OBJECTIVES

Clinical studies have shown alcohol to be a risk factor for traumatic orthopaedic injuries and for nonunion. Data from animal studies suggest that alcohol exposure inhibits fracture healing. This report presents a novel rodent model of impaired fracture healing caused by repeated alcohol exposure. Using this model, we examined the regenerative effects of an intravenously administered population of isolated and expanded mesenchymal stem cells (MSCs) on fracture healing.

METHODS

Bone marrow-derived MSC were isolated from transgenic green fluorescent protein C57BL/6 mice, and culture expanded using a lineage depletion protocol. Adult wild-type C57BL/6 mice were subjected to a 2-week binge alcohol exposure paradigm (3 days during which they received daily intraperitoneal injections of a 20% alcohol/saline solution followed by a 4-day rest period and another binge cycle for 3 consecutive days). At completion of the second binge cycle, mice were subjected to a mid-shaft tibia fracture while intoxicated. Twenty-four hours after the fracture, animals were administered an intravenous transplant of green fluorescent protein-labeled MSC. Two weeks after the fracture, animals were euthanized and injured tibiae were collected and subjected to biomechanical, histologic, and microcomputed tomography analysis.

RESULTS

Pre-injury binge alcohol exposure resulted in a significant impairment in biomechanical strength and decrease in callus volume. MSC transplants restored both fracture callus volume (P < 0.05) and biomechanical strength (P < 0.05) in animals with alcohol-impaired healing. In vivo imaging demonstrated a time-dependent MSC migration to the fracture site.

CONCLUSIONS

These data suggest that a 2-week binge alcohol exposure significantly impairs fracture healing in a murine tibia fracture model. Intravenously administered MSC were capable of specifically homing to the fracture site and of normalizing biomechanical, histologic, and microcomputed tomography parameters of healing in animals exposed to alcohol. Understanding MSC recruitment patterns and functional contributions to fracture repair may lead to their use in patients with impaired fracture healing and nonunion.

Systemically delivered insulin-like growth factor-I enhances mesenchymal stem cell-dependent fracture healing

In this study, we examined the effectiveness of systemic subcutaneous delivery of recombinant Insulin-like growth factor (IGF)-I concurrently with primary cultured bone marrow-derived mesenchymal stem cell (MSC) transplant on fracture repair. We found that the fracture callus volume increased in mice with a stabilized tibia fracture that received IGF-I+MSC when compared with that in either untreated or MSC alone treated mice. In evaluating the callus tissue components, we found that the soft and new bone tissue volumes were significantly increased in IGF-I+MSC recipients. Histological and in-situ hybridization analyses confirmed a characteristic increase of newly forming bone in IGF-I+MSC recipients and that healing progressed mostly through endochondral ossification. The increase in soft and new bone tissue volumes correlated with increased force and toughness as determined by biomechanical testing. In conclusion, MSC transplant concurrent with systemic delivery of IGF-I improves fracture repair suggesting that IGF-I+MSC could be a novel therapeutic approach in patients who have inadequate fracture repair.

Intercellular cytosolic transfer correlates with mesenchymal stromal cell rescue of umbilical cord blood cell viability during ex vivo expansion

Background aims. Mesenchymal stromal cells (MSC) have been observed to participate in tissue repair and to have growth-promoting effects on ex vivo co-culture with other stem cells. Methods. In order to evaluate the mechanism of MSC support on ex vivo cultures, we performed co-culture of MSC with umbilical cord blood (UCB) mononuclear cells (MNC) (UCB-MNC). Results. Significant enhancement in cell growth correlating with cell viability was noted with MSC co-culture (defined by double-negative staining for Annexin-V and 7-AAD; P<0.01). This was associated with significant enhancement of mitochondrial membrane potential (P<0.01). We postulated that intercellular transfer of cytosolic substances between MSC and UCB-MNC could be one mechanism mediating the support. Using MSC endogenously expressing green fluorescent protein (GFP) or labeled with quantum dots (QD), we performed co-culture of UCB-MNC with these MSC. Transfer of these GFP and QD was observed from MSC to UCB-MNC as early as 24 h post co-culture. Transwell experiments revealed that direct contact between MSC and UCB-MNC was necessary for both transfer and viability support. UCB-MNC tightly adherent to the MSC layer exhibited the most optimal transfer and rescue of cell viability. DNA analysis of the viable, GFP transfer-positive UCB-MNC ruled out MSC transdifferentiation or MSC-UCB fusion. In addition, there was statistical correlation between higher levels of cytosolic transfer and enhanced UCB-MNC viability (P< 0.0001). Conclusions. Collectively, the data suggest that intercellular transfer of cytosolic materials could be one novel mechanism for preventing UCB cell death in MSC co-culture.

Comparison of microCT and an inverse finite element approach for biomechanical analysis: results in a mesenchymal stem cell therapeutic system for fracture healing

An important concern in the study of fracture healing is the ability to assess mechanical integrity in response to candidate therapeutics in small-animal systems. In recent reports, it has been proposed that microCT image-derived densitometric parameters could be used as a surrogate for mechanical property assessment. Recently, we have proposed an inverse methodology that iteratively reconstructs the modulus of elasticity of the lumped soft callus/hard callus region by integrating both intrinsic mechanical property (from biomechanical testing) and geometrical information (from microCT) within an inverse finite element analysis (FEA) to define a callus quality measure. In this paper, data from a therapeutic system involving mesenchymal stem cells is analyzed within the context of comparing traditional microCT densitometric and mechanical property metrics. In addition, a novel multi-parameter regression microCT parameter is analyzed as well as our inverse FEA metric. The results demonstrate that the inverse FEA approach was the only metric to successfully detect both longitudinal and therapeutic responses. While the most promising microCT-based metrics were adequate at early healing states, they failed to track late-stage mechanical integrity. In addition, our analysis added insight to the role of MSCs by demonstrating accelerated healing and was the only metric to demonstrate therapeutic benefits at late-stage healing. In conclusion, the work presented here indicates that microCT densitometric parameters are an incomplete surrogate for mechanical integrity. Additionally, our inverse FEA approach is shown to be very sensitive and may provide a first-step towards normalizing the often challenging process of assessing mechanical integrity of healing fractures.

Sternal reconstruction for unusual chondrosarcoma: innovative technique

The authors report a clinical case of a primary sternal chondrosarcoma, presented as a mass in the anterior mediastinum. The patient was treated with subtotal sternectomy and sternal transplantation followed by radiotherapy. Twelve months after surgery, the patient is in good clinical condition, without any sign of tumor relapse and with normal respiratory mechanics. Primary malignant tumors of the sternum are uncommon and a presentation mimicking thymoma is rare and unreported. The stermal replacement with a cryopreserved allograft sternum is an innovative technique that overcomes the problems related to the prosthetic biocompatibility or to the bone autograft.

Co-culture of mesenchymal stem cells with umbilical vein endothelial cells under hypoxic condition

By co-culturing humm mesenchymal stem cells (hMSCs) and human umbilical rein endothelial cells (HUVECs) under hypoxia and creating a microenvironment similar to that of transplanted hMSCs for the treatment of avascular ni ANFH, the effect of hMSCs on survival, apoptosis, migration and angiogenesis of human umbilical vein endothelial cells (HUVECs) under the hypoxic condition were investigated in vitro. hMSCs and HUVECs were cultured and identified in vitro. Three kinds of conditioned media, CdM-CdM(NOR), CdM-CdM(HYP) and HUVEC-CdM(HYP) were prepared. HUVECs were cultured with these conditioned media under hypoxia. The survival rate, apoptosis rate, migration and angiogenesis of HUVECs were respectively detected by CCK-8, flow cytometry, Transwell and tube formation assay. The content of SDF-1α, VEGF and IL-6 in CdM was determined by ELISA. Our results showed that hMSCs and HUVECs were cultured and identified successfully. Compared with MSC-CdM(NOR) and HUVEC-CdM(HYP) groups, the survival rate, migration and angiogenesis of HUVECs in MSC-CdM(HYP) group were significantly increased while the apoptosis rate was declined (P<0.05). Moreover, the expression of SDF-1α, VEGF and IL-6 in MSC-CdM(HYP) group was up-regulated. Under hypoxia, the apoptosis of HUVECs was inhibited while survival, migration and angiogenesis were improved by co-culture of hMSCs and HUVECs. The underlying mechanism may be that hMSCs could secrete a number of cytokines and improve niche, which might be helpful in the treatment of femoral head necrosis.

The therapeutic potential of bone marrow-derived stromal cells

Since the replacement of the hematopoietic system became feasible through bone marrow (BM) transplantation, the idea of how to replace other organs of the body has been in the forefront of medical research. Scientists have been searching for the ideal stem cell that could be manipulated to differentiate into any tissue. Although the embryonal stem cells seemed to have the ability to do this, the difficulties surrounding their use prevented them from becoming therapeutically useful. Thus, the field turned to adult stem cells, particularly stem cells of BM origin. We have learnt a lot during the last decade about the potential of the BM-derived stromal (also called mesenchymal stem) cells (BMSCs). The first studies suggested them as cell replacement tools, but later it turned out that their usefulness is more likely due to paracrine effects due to a large variety of secreted factors that induce growth and differentiation of the tissue-specific stem cells as well as prevent injured cells from apoptotic death. Finally, a whole new field emerged when many groups confirmed that these cells are also capable of regulating immune function in a so far unknown, dynamic manner. When BMSCs are injected they seem to be able to sense the environment and respond according to the actual need of the organism in order to survive. This plasticity can never be done by the use of any drugs and such a "live" cell therapy could open a whole new chapter in clinical care in the future.

Mesenchymal stem cells as a potent cell source for bone regeneration

While small bone defects heal spontaneously, large bone defects need surgical intervention for bone transplantation. Autologous bone grafts are the best and safest strategy for bone repair. An alternative method is to use allogenic bone graft. Both methods have limitations, particularly when bone defects are of a critical size. In these cases, bone constructs created by tissue engineering technologies are of utmost importance. Cells are one main component in the manufacture of bone construct. A few cell types, including embryonic stem cells (ESCs), adult osteoblast, and adult stem cells, can be used for this purpose. Mesenchymal stem cells (MSCs), as adult stem cells, possess characteristics that make them good candidate for bone repair. This paper discusses different aspects of MSCs that render them an appropriate cell type for clinical use to promote bone regeneration.

Mesenchymal stem cells expressing insulin-like growth factor-I (MSCIGF) promote fracture healing and restore new bone formation in Irs1 knockout mice: analyses of MSCIGF autocrine and paracrine regenerative effects

Failures of fracture repair (nonunions) occur in 10% of all fractures. The use of mesenchymal stem cells (MSC) in tissue regeneration appears to be rationale, safe, and feasible. The contributions of MSC to the reparative process can occur through autocrine and paracrine effects. The primary objective of this study is to find a novel mean, by transplanting primary cultures of bone marrow-derived MSCs expressing insulin-like growth factor-I (MSC(IGF)), to promote these seed-and-soil actions of MSC to fully implement their regenerative abilities in fracture repair and nonunions. MSC(IGF) or traceable MSC(IGF)-Lac-Z were transplanted into wild-type or insulin-receptor-substrate knockout (Irs1(-/-)) mice with a stabilized tibia fracture. Healing was assessed using biomechanical testing, microcomputed tomography (μCT), and histological analyses. We found that systemically transplanted MSC(IGF) through autocrine and paracrine actions improved the fracture mechanical strength and increased new bone content while accelerating mineralization. We determined that IGF-I adapted the response of transplanted MSC(IGF) to promote their differentiation into osteoblasts. In vitro and in vivo studies showed that IGF-I-induced osteoglastogenesis in MSCs was dependent of an intact IRS1-PI3K signaling. Furthermore, using Irs1(-/-) mice as a nonunion fracture model through altered IGF signaling, we demonstrated that the autocrine effect of IGF-I on MSC restored the fracture new bone formation and promoted the occurrence of a well-organized callus that bridged the gap. A callus that was basically absent in Irs1(-/-) left untransplanted or transplanted with MSCs. We provided evidence of effects and mechanisms for transplanted MSC(IGF) in fracture repair and potentially to treat nonunions.

Soluble molecules are key in maintaining the immunomodulatory activity of murine mesenchymal stromal cells

Mesenchymal stromal cells (MSCs) possess both immuno-privileged and immuno-inhibitory properties that contribute to their therapeutic effects. Ex vivo expansion is required to obtain sufficient cells for therapy, but might also alter their immunological properties. To date there has been no systematic study of MSC immunobiology during extended culture. Here, we demonstrate that both immuno-privilege and immunosuppressive properties of MSCs change with increasing passage. We demonstrate that although MSCs exhibit powerful immunosuppressive effects through secretion of transforming growth factor-β (TGF-β) and induction of interleukin-10, these effects are diminished by a concomitant increase in MSC immunogenicity. Interferon-γ treatment for 3 days induced extendedly cultured MSCs to express significantly higher levels of major histocompatibility complex class I. In vivo, this results in cells that induce significant delayed-type hypersensitivity reactions in allogeneic recipients. Importantly, these effects are alleviated by isolation of the transplanted MSCs using a semi-permeable barrier. Under these conditions, even MSCs cultured through as many as 14 passages still exhibit immuno-inhibitory effects in vivo. Furthermore, the levels of anti-inflammatory molecule TGF-β secreted by MSCs were maintained in the extended culture. These data shed light on the variable results of allogeneic MSCs in transplantation and suggest alternative strategies for prolonging the effect of allogeneic MSCs in cell-based therapy.

Osteoblasts derived from induced pluripotent stem cells form calcified structures in scaffolds both in vitro and in vivo

Reprogramming somatic cells into an ESC-like state, or induced pluripotent stem (iPS) cells, has emerged as a promising new venue for customized cell therapies. In this study, we performed directed differentiation to assess the ability of murine iPS cells to differentiate into bone, cartilage, and fat in vitro and to maintain an osteoblast phenotype on a scaffold in vitro and in vivo. Embryoid bodies derived from murine iPS cells were cultured in differentiation medium for 8–12 weeks. Differentiation was assessed by lineage-specific morphology, gene expression, histological stain, and immunostaining to detect matrix deposition. After 12 weeks of expansion, iPS-derived osteoblasts were seeded in a gelfoam matrix followed by subcutaneous implantation in syngenic imprinting control region (ICR) mice. Implants were harvested at 12 weeks, histological analyses of cell and mineral and matrix content were performed. Differentiation of iPS cells into mesenchymal lineages of bone, cartilage, and fat was confirmed by morphology and expression of lineage-specific genes. Isolated implants of iPS cell-derived osteoblasts expressed matrices characteristic of bone, including osteocalcin and bone sialoprotein. Implants were also stained with alizarin red and von Kossa, demonstrating mineralization and persistence of an osteoblast phenotype. Recruitment of vasculature and microvascularization of the implant was also detected. Taken together, these data demonstrate functional osteoblast differentiation from iPS cells both in vitro and in vivo and reveal a source of cells, which merit evaluation for their potential uses in orthopedic medicine and understanding of molecular mechanisms of orthopedic disease.

Hypoxia induces osteogenesis-related activities and expression of core binding factor α1 in mesenchymal stem cells

Mesenchymal stem sells (MSCs) have received much attention in the field of bone tissue engineering due to their biological capability to differentiate into osteogenic lineage cells. Hypoxia-inducible factor 1alpha (HIF-1α) plays an important role in the MSC-related bone regeneration during hypoxia, while core binding factor alpha 1 (Cbfα1) is a transcription regulator that is involved in the chondrocyte differentiation and ossification. In the present study, we investigated the effects of hypoxia on biological capability of MSCs. MSCs were isolated from adult rabbit bone marrow, and were cultured in vitro under normoxia (air with 5% CO(2)) or hypoxia (5% CO(2) and 95% N(2)). The proliferation of MSCs, alkaline phosphatase (ALP) activity, and production of collagens type I and type III (Col I/III) were examined. The expression levels of HIF-1α and Cbfα1 were measured by real-time PCR and western blot analyses. We found that hypoxia significantly induced the proliferation of MSCs and increased ALP activity and the production of Col I/III. Moreover, hypoxia increased the expression of Cbfα1 mRNA after 12 h, whereas the expression of HIF-1α mRNA was increased after 1 h of hypoxia. Knockdown of HIF-1α expression with a small interfering RNA significantly increased the expression levels of Cbfα1 protein either under the normoxia or hypoxia condition. Our results indicate that hypoxia enhances MSCs to differentiate into osteogenic lineage cells and suggest that Cbfα1 may be negatively regulated by HIF-1α.

Plasticity of human menstrual blood stem cells derived from the endometrium

Stem cells can be obtained from women's menstrual blood derived from the endometrium. The cells display stem cell markers such as Oct-4, SSEA-4, Nanog, and c-kit (CD117), and have the potent ability to differentiate into various cell types, including the heart, nerve, bone, cartilage, and fat. There has been no evidence of teratoma, ectopic formation, or any immune response after transplantation into an animal model. These cells quickly regenerate after menstruation and secrete many growth factors to display recurrent angiogenesis. The plasticity and safety of the acquired cells have been demonstrated in many studies. Menstrual blood-derived stem cells (MenSCs) provide an alternative source of adult stem cells for research and application in regenerative medicine. Here we summarize the multipotent properties and the plasticities of MenSCs and other endometrial stem cells from recent studies conducted both in vitro and in vivo.

In vitro differentiation and maturation of human embryonic stem cell into multipotent cells

Human embryonic stem cells (hESCs), which have the potential to generate virtually any differentiated progeny, are an attractive cell source for transplantation therapy, regenerative medicine, and tissue engineering. To realize this potential, it is essential to be able to control ESC differentiation and to direct the development of these cells along specific pathways. Basic science in the field of embryonic development, stem cell differentiation, and tissue engineering has offered important insights into key pathways and scaffolds that regulate hESC differentiation, which have produced advances in modeling gastrulation in culture and in the efficient induction of endoderm, mesoderm, ectoderm, and many of their downstream derivatives. These findings have lead to identification of several pathways controlling the differentiation of hESCs into mesodermal derivatives such as myoblasts, mesenchymal cells, osteoblasts, chondrocytes, adipocytes, as well as hemangioblastic derivatives. The next challenge will be to demonstrate the functional utility of these cells, both in vitro and in preclinical models of bone and vascular diseases.

Comparative study of stemness characteristics of mesenchymal cells from bone marrow of children and adults

BACKGROUND AIMS

Age-related changes that could affect the biologic features of mesenchymal stromal cells (MSC), such as a decrease in proliferation and osteoblast differentiation capacity and an increase of senescence markers and apoptosis, have been reported recently. The aim of this study was the evaluation of age-related characteristics and the correlation of age with the functional properties of MSC.

METHODS

The doubling time (DT), colony-forming unit–fibroblast (CFU-F) colonies and surface antigen expression of MSC isolated from bone marrow (BM) of children (C-MSC) were compared with those from adults (A-MSC). The expression of Oct-4 and Nanog transcripts and the relative telomere length were evaluated in both groups.

RESULTS

DT values were lower in C-MSC compared with A-MSC, and a higher CFU-F count was observed in children. However, the expression of Oct-4 and Nanog did not differ between C-MSC and A-MSC and was not correlated with the proliferative capacity. The telomere length was significantly higher in C-MSC compared with A-MSC.

CONCLUSIONS

These data suggest that children's BM-derived MSC could be a more advantageous source of these cells for tissue engineering and cell therapy.