Human Fetal Mesenchymal Stem Cells as Vehicles for Gene Delivery

Extended and stable gene expression via nucleofection of MIDGE construct into adult human marrow mesenchymal stromal cells

Human mesenchymal stromal cell (hMSC) is a potential target for cell and gene therapy-based approaches against a variety of different diseases. Whilst cationic lipofection has been widely experimented, the Nucleofector technology is a relatively new non-viral transfection method designed for primary cells and hard-to-transfect cell lines. Herein, we compared the efficiency and viability of nucleofection with cationic lipofection, and used the more efficient transfection method, nucleofection, to deliver a construct of minimalistic, immunologically defined gene expression encoding the erythropoietin (MIDGE-EPO) into hMSC. MIDGE construct is relatively safer than the viral and plasmid expression systems as the detrimental eukaryotic and prokaryotic gene and sequences have been eliminated. Using a plasmid encoding the luciferase gene, we demonstrated a high transfection efficiency using the U-23 (21.79 ± 1.09%) and C-17 (5.62 ± 1.09%) pulsing program in nucleofection. The cell viabilities were (44.93 ± 10.10)% and (21.93 ± 5.72)%, respectively 24 h post-nucleofection. On the other hand, lipofection treatment only yielded less than 0.6% efficiencies despite showing higher viabilities. Nucleofection did not affect hMSC renewability, immunophenotype and differentiation potentials. Subsequently, we nucleofected MIDGE-EPO using the U-23 pulsing program into hMSC. The results showed that, despite a low nucleofection efficiency with this construct, the EPO protein was stably expressed in the nucleofected cells up to 55 days when determined by ELISA or immunocytochemical staining. In conclusion, nucleofection is an efficient non-viral transfection approach for hMSC, which when used in conjunction with a MIDGE construct, could result in extended and stable transgene expression in hMSC.

Genetically-manipulated adult stem cells as therapeutic agents and gene delivery vehicle for wound repair and regeneration

Wound therapy remains a clinical challenge and much effort has been focused on the development of novel therapeutic approaches for wound management. New knowledge about the way in which signals control wound cellular and molecular behavior has promoted the topical application of multipotent stem cells and bioactive molecules to injured tissue, for skin regeneration with less scar formation. However, limited clinical success indicates that the effective delivery of polypeptides and therapeutic cells, with controlled releasing profile, is a major challenge which is yet to be overcome. Recently, a technique in which the genetically-manipulated stem cells were used both as the therapeutic agents and the vehicle for gene delivery for wound treatment - a method which serves to provide regenerative cells and bioactive genes within an optimal environment of regulatory molecular expression for wound sites - has emerged as a promising strategy for wound regenerative therapy. In this article, the roles of adult stem cells - as the therapeutics and the vehicles in these advanced biomimetic drug delivery systems for wound regeneration medicine - are scrutinized to indicate their mechanisms, characteristics, broad applicability and future lines of investigation.

Genetically manipulated adult stem cells for wound healing

New knowledge of the signal controls and activities of adult stem cells (ASCs) involved in wound repair have led to extensive investigation of the topical delivery of biomacromolecules and multipotent stem cells to injured tissues for scar-less regeneration. The transplantation of genetically recombinant stem cells, which have roles as both therapeutics and carriers for gene delivery to wound sites, represents an attractive strategy for wound treatment. Here, we compare viral and non-viral vectors and three-dimensional scaffold-based transfection strategies in terms of their biosafety, recombinant efficiency and influence on the differentiation of ASCs, to indicate the future direction of the application of recombinant ASCs in wound treatment.

Growth inhibition of colorectal carcinoma by lentiviral TRAIL-transgenic human mesenchymal stem cells requires their substantial intratumoral presence

Colorectal carcinoma (CRC) constitutes a common malignancy with limited therapeutic options in metastasized stages. Mesenchymal stem cells (MSC) home to tumours and may therefore serve as a novel therapeutic tool for intratumoral delivery of antineoplastic factors. Tumour necrosis factor (TNF)-related apoptosis inducing ligand (TRAIL) which promises apoptosis induction preferentially in tumour cells represents such a factor. We generated TRAIL-MSC by transduction of human MSC with a third generation lentiviral vector system and analysed their characteristics and capacity to inhibit CRC growth. (1) TRAIL-MSC showed stable transgene expression with neither changes in the defining MSC characteristics nor signs of malignant transformation. (2) Upon direct in vitro coculture TRAIL-MSC induced apoptosis in TRAIL-sensitive CRC-cell lines (DLD-1 and HCT-15) but also in CRC-cell lines resistant to soluble TRAIL (HCT-8 and SW480). (3) In mixed subcutaneous (s.c.) xenografts TRAIL-MSC inhibited CRC-tumour growth presumably by apoptosis induction but a substantial proportion of TRAIL-MSC within the total tumour cell number was needed to yield such anti-tumour effect. (4) Systemic application of TRAIL-MSC had no effect on the growth of s.c. DLD-1 xenografts which appeared to be due to a pulmonary entrapment and low rate of tumour integration of TRAIL-MSC. Systemic TRAIL-MSC caused no toxicity in this model. (5) Wild-type MSC seemed to exert a tumour growth-supporting effect in mixed s.c. DLD-1 xenografts. These novel results support the idea that lentiviral TRAIL-transgenic human MSC may serve as vehicles for clinical tumour therapy but also highlight the need for further investigations to improve tumour integration of transgenic MSC and to clarify a potential tumour-supporting effect by MSC.

Thymidine kinase gene modified bone marrow mesenchymal stem cells as vehicles for antitumor therapy

Bone marrow mesenchymal stem cells (BMSCs) represent an important source of cells for tissue repair. The tropism of these cells to the sites of injury and tumors has been well established. Their tumor-homing properties make BMSCs good candidates as antitumor agent delivery vehicles. In this study, we showed that BMSCs have the ability to migrate toward various cancer cells, including prostate cancer cells in vitro and in vivo and incorporating into the tumor mass. When infected with herpes simplex virus thymidine kinase (TK) gene by lentiviral transduction, TK-BMSCs maintained their tumor tropism capabilities and significantly inhibited the growth of subcutaneous PC3 prostate cancer xenografts in nude mice, in the presence of prodrug ganciclovir (GCV). Xenogenic TK-BMSCs also survived and exerted a significant antitumor effect in an animal model bearing metastastic RIF-1 (fibrosarcoma) tumor in the presence of prodrug GCV. The present study demonstrated that overexpression of TK in BMSCs did not affect their multidifferentiation potentials and their specific homing capacities toward the tumor mass, and the TK-BMSCs alone did not cause any harmful side effects in vivo. The use of TK-BMSCs as tumor-specific delivery vehicles together with controlled prodrug treatment may be a safe and novel anticancer therapy approach.

Concise review: Nanoparticles and cellular carriers-allies in cancer imaging and cellular gene therapy?

Ineffective treatment and poor patient management continue to plague the arena of clinical oncology. The crucial issues include inadequate treatment efficacy due to ineffective targeting of cancer deposits, systemic toxicities, suboptimal cancer detection and disease monitoring. This has led to the quest for clinically relevant, innovative multifaceted solutions such as development of targeted and traceable therapies. Mesenchymal stem cells (MSCs) have the intrinsic ability to "home" to growing tumors and are hypoimmunogenic. Therefore, these can be used as (a) "Trojan Horses" to deliver gene therapy directly into the tumors and (b) carriers of nanoparticles to allow cell tracking and simultaneous cancer detection. The camouflage of MSC carriers can potentially tackle the issues of safety, vector, and/or transgene immunogenicity as well as nanoparticle clearance and toxicity. The versatility of the nanotechnology platform could allow cellular tracking using single or multimodal imaging modalities. Toward that end, noninvasive magnetic resonance imaging (MRI) is fast becoming a clinical favorite, though there is scope for improvement in its accuracy and sensitivity. In that, use of superparamagnetic iron-oxide nanoparticles (SPION) as MRI contrast enhancers may be the best option for tracking therapeutic MSC. The prospects and consequences of synergistic approaches using MSC carriers, gene therapy, and SPION in developing cancer diagnostics and therapeutics are discussed.

Interferon-gamma and tumor necrosis factor-alpha differentially affect cytokine expression and migration properties of mesenchymal stem cells

Mesenchymal stem cells (MSCs) are multipotent progenitor cells with the capacity to differentiate into different tissue cell types such as chondrocytes, osteocytes, and adipocytes. In addition, they can home to damaged, in-flamed, and malignant tissues and display immunomodulatory properties. Since tissue-derived factors might modulate these properties, we decided to explore the impact of prototypic tissue-derived inflammatory cytokines such as TNF-alpha and IFN-gamma on immunomodulatory MSCs functions. To this end, we used primary bone marrow and cord blood-derived MSCs as well as an immortalized MSC line (V54/2) as model systems. We demonstrate that under unstimulated conditions, V54/2 cells constitutively express low levels of indoleamine 2,3-dioxygenase (IDO), exert an immunosuppressive effect on activated T-lymphocyte proliferation, secrete a distinct set of cytokines, and express a wide range of chemokine receptors. Upon stimulation, the proinflammatory cytokines IFN-gamma and TNF-alpha did not inhibit suppression of T-cell proliferation, although IDO expression was up-regulated by IFN-gamma. In contrast, TNF-alpha but not IFN-gamma amplified the cytokine production of V54/2 and primary MSCs. Interestingly, IFN-gamma was superior to TNF-alpha in up-regulating expression of chemokine receptors and migration of the V54/2 cell line, while TNF-alpha was the predominant regulator of migration in primary MSCs. Altogether, our data show that properties of MSCs depend on local environmental factors. In particular, we have shown that IFN-gamma and TNF-alpha differentially regulate cytokine expression and migration of MSCs.

Developing cell therapy techniques for respiratory disease: intratracheal delivery of genetically engineered stem cells in a murine model of airway injury

Interest has increased in the use of exogenous stem cells to optimize lung repair and serve as carriers of a therapeutic gene for genetic airway diseases such as cystic fibrosis. We investigated the survival and engraftment of exogenous stem cells after intratracheal injection, in a murine model of acute epithelial airway injury already used in gene therapy experiments on cystic fibrosis. Embryonic stem cells and mesenchymal stem cells were intratracheally injected 24 hr after 2% polidocanol administration, when epithelial airway injury was maximal. Stem cells were transfected with reporter genes immediately before administration. Reporter gene expression was analyzed in trachea-lungs and bronchoalveolar lavage, using nonfluorescence, quantitative, and sensitive methods. Enzyme-linked immunosorbent assay quantitative results showed that 0.4 to 5.5% of stem cells survived in the injured airway. Importantly, no stem cells survived in healthy airway or in the epithelial lining fluid. Using 5-bromo-4-chloro-3-indolyl-beta-d-galactopyranoside staining, transduced mesenchymal stem cells were detected in injured trachea and bronchi lumen. When the epithelium was spontaneously regenerated, the in vivo amount of engrafted mesenchymal stem cells from cell lines decreased dramatically. No stem cells from primary culture were located within the lungs at 7 days. This study demonstrated the feasibility of intratracheal cell delivery for airway diseases with acute epithelial injury.

Biological characteristics of stem cells from foetal, cord blood and extraembryonic tissues

Foetal stem cells (FSCs) can be isolated during gestation from many different tissues such as blood, liver and bone marrow as well as from a variety of extraembryonic tissues such as amniotic fluid and placenta. Strong evidence suggests that these cells differ on many biological aspects such as growth kinetics, morphology, immunophenotype, differentiation potential and engraftment capacity in vivo. Despite these differences, FSCs appear to be more primitive and have greater multi-potentiality than their adult counterparts. For example, foetal blood haemopoietic stem cells proliferate more rapidly than those found in cord blood or adult bone marrow. These features have led to FSCs being investigated for pre- and post-natal cell therapy and regenerative medicine applications. The cells have been used in pre-clinical studies to treat a wide range of diseases such as skeletal dysplasia, diaphragmatic hernia and respiratory failure, white matter damage, renal pathologies as well as cancers. Their intermediate state between adult and embryonic stem cells also makes them an ideal candidate for reprogramming to the pluripotent status.

The immunomodulatory properties of mesenchymal stem cells: implications for surgical disease

Mesenchymal stem cells (MSCs) have been used experimentally and clinically in the treatment of a wide variety of pathologies. It is now clear that a number of different mechanisms contribute to the therapeutic effects exerted by these cells. The ability of MSCs to interact with and modulate the functions of a wide variety of immune cells has been recognized as one such mechanism. The implications that the immunomodulatory properties of MSCs may have for the treatment of solid organ rejection, the Systemic Inflammatory Response Syndrome, cancer, and Crohn's disease are reviewed herein.

Mesenchymal stem cells: a promising targeted-delivery vehicle in cancer gene therapy

The targeting drug delivery systems (TDDS) have attracted extensive attention of researchers in recent years. More and more drug/gene targeted delivery carriers, such as liposome, magnetic nanoparticles, ligand-conjugated nanoparticles, microbubbles, etc., have been developed and under investigation for their application. However, the currently investigated drug/gene carriers have several disadvantages, which limit their future use in clinical practice. Therefore, design and development of novel drug/gene delivery vehicles has been a hot area of research. Recent studies have shown the ability of mesenchymal stem cells (MSCs) to migrate towards and engraft into the tumor sites, which make them a great hope for efficient targeted-delivery vehicles in cancer gene therapy. In this review article, we examine the promising of using mesenchymal stem cells as a targeted-delivery vehicle for cancer gene therapy, and summarize various challenges and concerns regarding these therapies.

Stem cells as vectors for antitumour therapy

Recent research suggests that mesenchymal stem cells (MSCs) are able to migrate specifically to tumours and their metastases throughout the body. This has led to considerable excitement about the possibility of modifying these cells to express anticancer molecules and using them as specific targeted anticancer agents. However, there are concerns that systemically delivered MSCs may have non-desirable effects, and there are also many unanswered questions including the mechanism of tumour homing. This review investigates the different MSC-delivered anticancer agents, addresses the questions and concerns, and tries to place this potential therapy in future cancer management.

Microgel iron oxide nanoparticles for tracking human fetal mesenchymal stem cells through magnetic resonance imaging

Stem cell transplantation for regenerative medicine has made significant progress in various injury models, with the development of modalities to track stem cell fate and migration post-transplantation being currently pursued rigorously. Magnetic resonance imaging (MRI) allows serial high-resolution in vivo detection of transplanted stem cells labeled with iron oxide particles, but has been hampered by low labeling efficiencies. Here, we describe the use of microgel iron oxide (MGIO) particles of diameters spanning 100-750 nm for labeling human fetal mesenchymal stem cells (hfMSCs) for MRI tracking. We found that MGIO particle uptake by hfMSCs was size dependent, with 600-nm MGIO (M600) particles demonstrating three- to sixfold higher iron loading than the clinical particle ferucarbotran (33-263 versus 9.6-42.0 pg iron/hfMSC; p < .001). Cell labeling with either M600 particles or ferucarbotran did not affect either cellular proliferation or tri-lineage differentiation into osteoblasts, adipocytes, and chondrocytes, despite differences in gene expression on a genome-wide microarray analysis. Cell tracking in a rat photothrombotic stroke model using a clinical 1.5-T MRI scanner demonstrated the migration of labeled hfMSCs from the contralateral cortex to the stroke injury, with M600 particles achieving a five- to sevenfold higher sensitivity for MRI detection than ferucarbotran (p < .05). However, model-related cellular necrosis and acute inflammation limited the survival of hfMSCs beyond 5-12 days. The use of M600 particles allowed high detection sensitivity with low cellular toxicity to be achieved through a simple incubation protocol, and may thus be useful for cellular tracking using standard clinical MRI scanners.

Lentiviral vector transduction of fetal mesenchymal stem cells

Human fetal mesenchymal stem cells (hfMSC) demonstrate extensive expansion and differentiation capacities and are hence being studied for use in stem cell therapeutics, including gene delivery. With advanced prenatal diagnosis, fetal gene therapy represents an additional avenue for the treatment of inherited deficiencies. We have recently demonstrated harvesting of first-trimester fMSC from fetal blood for ex vivo genetic engineering to introduce genes of interest, and finally intra-uterine transplantation (IUT) of these cells to the fetus. Here we discuss methods in the harvesting of hfMSC, lentiviral transduction to introduce genes of interest, and in vitro methods to characterise transgene expression.

Magnetic resonance imaging of mesenchymal stem cells homing to pulmonary metastases using biocompatible magnetic nanoparticles

The ability of mesenchymal stem cells (MSC) to specifically home to tumors has suggested their potential use as a delivery vehicle for cancer therapeutics. MSC integration into tumors has been shown in animal models using histopathologic techniques after animal sacrifice. Tracking the delivery and engraftment of MSCs into human tumors will need in vivo imaging techniques. We hypothesized that labeling MSCs with iron oxide nanoparticles would enable in vivo tracking with magnetic resonance imaging (MRI). Human MSCs were labeled in vitro with superparamagnetic iron oxide nanoparticles, with no effect on differentiation potential, proliferation, survival, or migration of the cells. In initial experiments, we showed that as few as 1,000 MSCs carrying iron oxide nanoparticles can be detected by MRI one month after their coinjection with breast cancer cells that formed subcutaneous tumors. Subsequently, we show that i.v.- injected iron-labeled MSCs could be tracked in vivo to multiple lung metastases using MRI, observations that were confirmed histologically. This is the first study to use MRI to track MSCs to lung metastases in vivo. This technique has the potential to show MSC integration into human tumors, allowing early-phase clinical studies examining MSC homing in patients with metastatic tumors.

Mesenchymal stem cells: emerging therapy for Duchenne muscular dystrophy

Multipotent cells that can give rise to bone, cartilage, fat, connective tissue, and skeletal and cardiac muscle are termed mesenchymal stem cells. These cells were first identified in the bone marrow, distinct from blood-forming stem cells. Based on the embryologic derivation, availability, and various pro-regenerative characteristics, research exploring their use in cell therapy shows great promise for patients with degenerative muscle diseases and a number of other conditions. In this review, the authors explore the potential for mesenchymal stem cell therapy in the emerging field of regenerative medicine with a focus on treatment for Duchenne muscular dystrophy.

Fetal-maternal exchange of multipotent stem/progenitor cells: microchimerism in diagnosis and disease

The biological concept of microchimerism, the bidirectional trafficking and stable long-term persistence of small numbers of allogeneic (fetal and maternal) cells in a genetically different organ, has gained considerable attention. Microchimerism is a common phenomenon in many species, including humans, and microchimeric cells can modify immunological recognition or tolerance, affect the course and outcome of various diseases and demonstrate stem cell-like or regenerative potential. Here, we review current knowledge of the biology of microchimerism and show how long-term allogeneic co-existence within an organism can impact on existing paradigms in chronic disease, cancer biology, regenerative medicine and fetal-maternal immunology. We discuss diagnostic challenges, clinical applications and future research directions in this exciting and rapidly emerging field of allogeneic fetal-maternal cell exchange.

Osteogenic differentiation of mesenchymal stem cells promoted by overexpression of connective tissue growth factor

OBJECTIVE

Large segmental bone defect repair remains a clinical and scientific challenge with increasing interest focusing on combining gene transfection with tissue engineering techniques. The aim of this study is to investigate the effect of connective tissue growth factor (CTGF) on the proliferation and osteogenic differentiation of the bone marrow mesenchymal stem cells (MSCs).

METHODS

A CTGF-expressing plasmid (pCTGF) was constructed and transfected into MSCs. Then expressions of bone morphogenesis-related genes, proliferation rate, alkaline phosphatase activity, and mineralization were examined to evaluate the osteogenic potential of the CTGF gene-modified MSCs.

RESULTS

Overexpression of CTGF was confirmed in pCTGF-MSCs. pCTGF transfection significantly enhanced the proliferation rates of pCTGF-MSCs (P<0.05). CTGF induced a 7.5-fold increase in cell migration over control (P<0.05). pCTGF transfection enhanced the expression of bone matrix proteins, such as bone sialoprotein, osteocalcin, and collagen type I in MSCs. The levels of alkaline phosphatase (ALP) activities of pCTGF-MSCs at the 1st and 2nd weeks were 4.0- and 3.0-fold higher than those of MSCs cultured in OS-medium, significantly higher than those of mock-MSCs and normal control MSCs (P<0.05). Overexpression of CTGF in MSCs enhanced the capability to form mineralized nodules.

CONCLUSION

Overexpression of CTGF could improve the osteogenic differentiation ability of MSCs, and the CTGF gene-modified MSCs are potential as novel cell resources of bone tissue engineering.

Superior osteogenic capacity for bone tissue engineering of fetal compared with perinatal and adult mesenchymal stem cells

Mesenchymal stem cells (MSCs) from human adult bone marrow (haMSCs) represent a promising source for bone tissue engineering. However, their low frequencies and limited proliferation restrict their clinical utility. Alternative postnatal, perinatal, and fetal sources of MSCs appear to have different osteogenic capacities, but have not been systematically compared with haMSCs. We investigated the proliferative and osteogenic potential of MSCs from human fetal bone marrow (hfMSCs), human umbilical cord (hUCMSCs), and human adult adipose tissue (hATMSCs), and haMSCs, both in monolayer cultures and after loading into three-dimensional polycaprolactone-tricalcium-phosphate scaffolds.Although all MSCs had comparable immunophenotypes, only hfMSCs and hUCMSCs were positive for the embryonic pluripotency markers Oct-4 and Nanog. hfMSCs expressed the lowest HLA-I level (55% versus 95%-99%) and the highest Stro-1 level (51% versus 10%-27%), and had the greatest colony-forming unit-fibroblast capacity (1.6x-2.0x; p < .01) and fastest doubling time (32 versus 54-111 hours; p < .01). hfMSCs had the greatest osteogenic capacity, as assessed by von-Kossa staining, alkaline phosphatase activity (5.1x-12.4x; p < .01), calcium deposition (1.6x-2.7x in monolayer and 1.6x-5.0x in scaffold culture; p < .01), calcium visualized on micro-computed tomography (3.9x17.6x; p < .01) and scanning electron microscopy, and osteogenic gene induction. Two months after implantation of cellular scaffolds in immunodeficient mice, hfMSCs resulted in the most robust mineralization (1.8x-13.3x; p < .01).The ontological and anatomical origins of MSCs have profound influences on the proliferative and osteogenic capacity of MSCs. hfMSCs had the most proliferative and osteogenic capacity of the MSC sources, as well as being the least immunogenic, suggesting they are superior candidates for bone tissue engineering.

Adenine nucleotide translocase 4 deficiency leads to early meiotic arrest of murine male germ cells

Male fertility relies on the highly specialized process of spermatogenesis to continually renew the supply of spermatozoa necessary for reproduction. Central to this unique process is meiosis that is responsible for the production of haploid spermatozoa as well as for generating genetic diversity. During meiosis I, there is a dramatic increase in the number of mitochondria present within the developing spermatocytes, suggesting an increased necessity for ATP production and utilization. Essential for the utilization of ATP is the translocation of ADP and ATP across the inner mitochondrial membrane, which is mediated by the adenine nucleotide translocases (Ant). We recently identified and characterized a novel testis specific Ant, ANT4 (also known as SLC25A31 and Aac4). The generation of Ant4-deficient animals resulted in the severe disruption of the seminiferous epithelium with an apparent spermatocytic arrest of the germ cell population. In the present study utilizing a chromosomal spread technique, we determined that Ant4-deficiency results in an accumulation of leptotene spermatocytes, a decrease in pachytene spermatocytes, and an absence of diplotene spermatocytes, indicating early meiotic arrest. Furthermore, the chromosomes of Ant4-deficient pachytene spermatocyte occasionally demonstrated sustained gammaH2AX association as well as synaptonemal complex protein 1 (SYCP1)/SYCP3 dissociation beyond the sex body. Large ATP supplies from mitochondria may be critical for normal progression of spermatogenesis during early stages of meiotic prophase I, including DNA double-strand break repair and chromosomal synapsis.

Mesenchymal stem cell delivery of TRAIL can eliminate metastatic cancer

Cancer is a leading cause of mortality throughout the world and new treatments are urgently needed. Recent studies suggest that bone marrow-derived mesenchymal stem cells (MSC) home to and incorporate within tumor tissue. We hypothesized that MSCs engineered to produce and deliver tumor necrosis factor-related apoptosis-inducing ligand (TRAIL), a transmembrane protein that causes selective apoptosis of tumor cells, would home to and kill cancer cells in a lung metastatic cancer model. Human MSCs were transduced with TRAIL and the IRES-eGFP reporter gene under the control of a tetracycline promoter using a lentiviral vector. Transduced and activated MSCs caused lung (A549), breast (MDAMB231), squamous (H357), and cervical (Hela) cancer cell apoptosis and death in coculture experiments. Subcutaneous xenograft experiments confirmed that directly delivered TRAIL-expressing MSCs were able to significantly reduce tumor growth [0.12 cm(3) (0.04-0.21) versus 0.66 cm(3) (0.21-1.11); P < 0.001]. We then found, using a pulmonary metastasis model, systemically delivered MSCs localized to lung metastases and the controlled local delivery of TRAIL completely cleared the metastatic disease in 38% of mice compared with 0% of controls (P < 0.05). This is the first study to show a significant reduction in metastatic tumor burden with frequent eradication of metastases using inducible TRAIL-expressing MSCs. This has a wide potential therapeutic role, which includes the treatment of both primary tumors and their metastases, possibly as an adjuvant therapy in clearing micrometastatic disease following primary tumor resection.

Assessment of therapeutic efficacy and fate of engineered human mesenchymal stem cells for cancer therapy

The poor prognosis of patients with aggressive and invasive cancers combined with toxic effects and short half-life of currently available treatments necessitate development of more effective tumor selective therapies. Mesenchymal stem cells (MSCs) are emerging as novel cell-based delivery agents; however, a thorough investigation addressing their therapeutic potential and fate in different cancer models is lacking. In this study, we explored the engineering potential, fate, and therapeutic efficacy of human MSCs in a highly malignant and invasive model of glioblastoma. We show that engineered MSC retain their "stem-like" properties, survive longer in mice with gliomas than in the normal brain, and migrate extensively toward gliomas. We also show that MSCs are resistant to the cytokine tumor necrosis factor apoptosis ligand (TRAIL) and, when engineered to express secreted recombinant TRAIL, induce caspase-mediated apoptosis in established glioma cell lines as well as CD133-positive primary glioma cells in vitro. Using highly malignant and invasive human glioma models and employing real-time imaging with correlative neuropathology, we demonstrate that MSC-delivered recombinant TRAIL has profound anti-tumor effects in vivo. This study demonstrates the efficacy of diagnostic and therapeutic MSC in preclinical glioma models and forms the basis for developing stem cell-based therapies for different cancers.

Isolation and culture of bone marrow mesenchymal stem cells from human fetus and their biological properties

The population doubling number (70–80 times) of human fetal bone marrow mesenchymal stem cells (BMMSCs) is about two times higher than that (30–40 times) of adult BMMSCs, and their differentiation capacity is superior to that of their adult counterparts. In this study, BMMSCs were isolated from long bones of 2- to 3-month-old human abortuses by rinsing and selectively culturing whole marrow cells. Basic medium and serum concentration were optimized and growth curves plotted, both by MTT [3-(4,5-dimethylthiazol-2-yl)-2,5-di-phenyltetrazolium bromide] reduction assay. Isolated cells were identified by flow cytometry and immunocytochemistry for their antigen markers. The biosafety of isolated cells was evaluated by karyotype analysis and a tumour-forming experiment. The results indicated that lengthwise scissoring of fetal long bones and rinsing of their marrow cells was practical and useful for recovery of BMMSCs from the investigated human abortuses. In this experiment, α-MEM (minimum essential medium, alpha medium)+20% FCS (fetal calf serum) was the best for in vitro culture of BMMSCs. The third-passage BMMSCs expressed Oct4, SSEA3 and SSEA4 besides the surface markers of their adult counterparts. The population doubling time of the BMMSCs of passage 6, 12 and 24 were 34, 36 and 40 h, respectively. Cells in all passages showed a diploid karyotype and formed no tumours in nude mice. The BMMSCs used in this study proved to be biologically safe and ideal seed cells for research on human tissue engineering and regeneration medicine.

A simple and reliable electroporation method for human bone marrow mesenchymal stem cells

Adult human mesenchymal stem cells (hMSCs) are able to differentiate into a range of specific cell types in vitro and in vivo, and thus hold tremendous potential for use in regenerative medicine. Despite this promise, deficient understanding of the mechanisms that regulate their differentiation has precluded their widespread use. Genetic manipulation of hMSCs by introduction of transgenes is an indispensable tool for gaining insight into these mechanisms. Like most primary cultures, hMSCs are difficult to transfect with conventional techniques, and although some viral transduction techniques are highly efficient, the protocols require extensive optimization and contain significant health risks. We were generally unable to achieve high transfection efficiencies with lipofection-based reagents that we found, in contrast to electroporation, adversely affected hMSC proliferation and differentiation. Here we report a simple and reliable electroporation protocol that results in transfection efficiencies up to 90% that are comparable to most viral methods while maintaining hMSC stemness. Most importantly, our protocol does not rely on a specific electroporator with preset programs and unique buffers, and is thus much simpler, cheaper, and easier to optimize. Furthermore, we show sustained transgene expression lasting several weeks that was useful for assessing the effects on hMSC function and in transient expression gene therapy.

Human amnion-derived mesenchymal stem cells are a potential source for uterine stem cell therapy

OBJECTIVES

Human amnion is an easy-to-obtain novel source of human mesenchymal stem cells, which poses little or no ethical dilemmas. We have previously shown that human amnion-derived mesenchymal (HAM) cells exhibit certain mesenchymal stem cell-like characteristics with respect to expression of stem cell markers and differentiation potentials.

MATERIALS AND METHODS

In this study, we further characterized HAM cells' potential for in vivo therapeutic application.

RESULTS

Flow cytometric analyses of HAM cells show that they express several stem cell-related cell surface markers, including CD90, CD105, CD59, CD49d, CD44 and HLA-ABC, but not CD45, CD34, CD31, CD106 or HLA-DR. HAM cells at the 10th passage showed normal karyotype. More interestingly, the AbdB-like HOXA genes HOXA9, HOXA10 and HOXA11 that are expressed in the mesenchyme of the developing female reproductive tract and pregnant uteri are also expressed in HAM cells, suggesting similarities between these two mesenchymal cell types. Progesterone receptor is also highly expressed in HAM cells and expression of genes or proteins in HAM cells could be manipulated with the aid of lentivirus technology or cell-permeable peptides. To test potentials of HAM cells for in vivo application, we introduced enhanced green fluorescence protein (EGFP)-expressing HAM cells to mice by intrauterine infusion (into uteri) or by intravenous injection (into the circulation). Presence of EGFP-expressing cells within the uterine mesenchyme after intrauterine infusion or in lungs after intravenous injection was noted within 1-4 weeks.

CONCLUSIONS

Collectively, these results suggest that HAM cells are a potential source of mesenchymal stem cells with therapeutic potential.

Modulation of biodistribution and expression of plasmid DNA following mesenchymal progenitor cell-based delivery

Although therapeutic applications of mesenchymal progenitor cells (MPCs) have been studied, the in vivo fate of genes delivered by the MPCs has received little attention. We report here the in vivo kinetics, tissue distribution, and duration of gene expression after systemic administration of plasmid DNA delivered by MPCs. Murine MPCs were isolated from bone marrow, cultured, and transfected with plasmid DNA using polyethylenimine. The gene-modified MPCs or naked plasmid DNA was administered intravenously to mice. Injected MPCs incorporating plasmid DNA yielded elevated serum concentrations when compared with the group treated with plasmid DNA alone, a 280-fold higher level measured at 5-min post-administration. Moreover, plasmid DNA delivered in MPCs was detected in several organs, lymph nodes, and bone marrow. The highest levels of distribution were observed in the liver, followed by lung and spleen at 4 days post-dose. Similar to the distribution of DNA, significant expression levels of the exogenous gene were observed only after delivery of the DNA in MPCs, demonstrating the sustained expression at the liver, lung, and kidney for 4 days after tail vein injection. This study provides perspectives regarding the in vivo fate and target tissue distribution of genes following MPC-based delivery.

Comparative osteogenic transcription profiling of various fetal and adult mesenchymal stem cell sources

Human mesenchymal stem cells (MSC) from adult and fetal tissues are promising candidates for cell therapy but there is a need to identify the optimal source for bone regeneration. We have previously characterized MSC populations in first trimester fetal blood, liver, and bone marrow and we now evaluate their osteogenic differentiation potential in comparison to adult bone marrow MSC. Using quantitative real-time RT-PCR, we demonstrated that 16 osteogenic-specific genes (OC, ON, BSP, OP, Col1, PCE, Met2A, OPG, PHOS1, SORT, ALP, BMP2, CBFA1, OSX, NOG, IGFII) were expressed in both fetal and adult MSC under basal conditions and were up-regulated under osteogenic conditions both in vivo and during an in vitro 21-day time-course. However, under basal conditions, fetal MSC had higher levels of osteogenic gene expression than adult MSC. Upon osteogenic differentiation, fetal MSC produced more calcium in vitro and reached higher levels of osteogenic gene up-regulation in vivo and in vitro. Second, we observed a hierarchy within fetal samples, with fetal bone marrow MSC having greater osteogenic potential than fetal blood MSC, which in turn had greater osteogenic potential than fetal liver MSC. Finally, we found that the level of gene expression under basal conditions was positively correlated with both calcium secretion and gene expression after 21 days in osteogenic conditions. Our findings suggest that stem cell therapy for bone dysplasias such as osteogenesis imperfecta may benefit from preferentially using first trimester fetal blood or bone marrow MSC over fetal liver or adult bone marrow MSC.

Transplantation of human fetal mesenchymal stem cells improves glomerulopathy in a collagen type I alpha 2-deficient mouse

Fetal mesenchymal stem cell (fetal MSC) therapy has potential to treat genetic diseases with early onset, including those affecting the kidney and urinary tract. A collagen type I alpha 2-deficient mouse has a deletion in the alpha2 chain of the procollagen type I gene, resulting in the synthesis of abnormal alpha1(I)(3) homotrimers, which replace normal alpha 1(I)2 alpha 2(I)1 heterotrimers and a glomerulopathy. We first confirmed that col1 alpha 2-deficient homozygous mice show abnormal collagen deposition in the glomeruli, which increases in frequency and severity with postnatal age. Intrauterine transplantation of human MSCs from first trimester fetal blood led postnatally to a reduction of abnormal homotrimeric collagen type I deposition in the glomeruli of 4-12 week-old col1 alpha 2-deficient mice. Using bioluminescence imaging, in situ hybridization and immunohistochemistry in transplanted col1 alpha 2-deficient mice, we showed that the damaged kidneys preferentially recruited donor cells in glomeruli, around mesangial cells. Real-time RT-PCR demonstrated that this effect was seen at an engraftment level of 1% of total cells in the kidney, albeit higher in glomeruli. We conclude that intrauterine transplantation of human fetal MSCs improves renal glomerulopathy in a collagen type I-deficient mouse model. These data support the feasibility of prenatal treatment for hereditary renal diseases.

Stem and progenitor cell-mediated tumor selective gene therapy

The poor prognosis for patients with aggressive or metastatic tumors and the toxic side effects of currently available treatments necessitate the development of more effective tumor-selective therapies. Stem/progenitor cells display inherent tumor-tropic properties that can be exploited for targeted delivery of anticancer genes to invasive and metastatic tumors. Therapeutic genes that have been inserted into stem cells and delivered to tumors with high selectivity include prodrug-activating enzymes (cytosine deaminase, carboxylesterase, thymidine kinase), interleukins (IL-2, IL-4, IL-12, IL-23), interferon-beta, apoptosis-promoting genes (tumor necrosis factor-related apoptosis-inducing ligand) and metalloproteinases (PEX). We and others have demonstrated that neural and mesenchymal stem cells can deliver therapeutic genes to elicit a significant antitumor response in animal models of intracranial glioma, medulloblastoma, melanoma brain metastasis, disseminated neuroblastoma and breast cancer lung metastasis. Most studies reported reduction in tumor volume (up to 90%) and increased survival of tumor-bearing animals. Complete cures have also been achieved (90% disease-free survival for >1 year of mice bearing disseminated neuroblastoma tumors). As we learn more about the biology of stem cells and the molecular mechanisms that mediate their tumor-tropism and we identify efficacious gene products for specific tumor types, the clinical utility of cell-based delivery strategies becomes increasingly evident.

Optimization of a gene electrotransfer method for mesenchymal stem cell transfection

Gene electrotransfer is an efficient and reproducible nonviral gene transfer technique useful for the nonpermanent expression of therapeutic transgenes. The present study established optimal conditions for the electrotransfer of reporter genes into mesenchymal stem cells (MSCs) isolated from rat bone marrow by their selective adherence to tissue-culture plasticware. The electrotransfer of the lacZ reporter gene was optimized by adjusting the pulse electric field intensity, electric pulse type, electropulsation buffer conductivity and electroporation temperature. LacZ electrotransfection into MSCs was optimal at 1500 V cm(-1) with pre-incubation in Spinner's minimum essential medium buffer at 22 degrees C. Under these conditions beta-galactosidase expression was achieved in 29+/-3% of adherent cells 48 h post transfection. The kinetics of beta-galactosidase activity revealed maintenance of beta-galactosidase production for at least 10 days. Moreover, electroporation did not affect the MSC potential for multidifferentiation; electroporated MSCs differentiated into osteoblastic, adipogenic and chondrogenic lineages to the same extent as cells that were not exposed to electric pulses. Thus, this study demonstrates the feasibility of efficient transgene electrotransfer into MSCs while preserving cell viability and multipotency.

Intrauterine transplantation of human fetal mesenchymal stem cells from first-trimester blood repairs bone and reduces fractures in osteogenesis imperfecta mice

The inherited skeletal dysplasia osteogenesis imperfecta (OI) results in multiple fractures and is currently treated empirically. We transplanted human first-trimester fetal blood mesenchymal stem cells (MSCs) into homozygous oim mice in utero. This resulted in a two-thirds reduction in long bone fractures (P < .01), with fewer fractures per mouse (median 1, range 0-2 in mice that received transplants vs median 3, range 1-5 in mice that did not receive transplants by 12 weeks, P < .01). Nearly all mice that did not receive transplants had fractures (47 [97.9%] of 48), in contrast to 17 (58.6%) of 29 4- to 12-week-old mice that received transplants (P < .01). Transplantation was associated with increased bone strength (P < .01), thickness (P < .01), and length (P < .01), and normalization/reduction of growth plate height in 4- to 12-week-old oim was reduced in mice that underwent transplantion (P < .001). More donor cells were found in bone tissues compared with other organs (P < .001), with cells clustered in areas of active bone formation and remodeling, and at sites of fracture healing. Donor cells found in the bone expressed osteoblast lineage genes, and produced the extracellular bone structural protein osteopontin. Finally, MSC transplantation decreased bone hydroxyproline content. In conclusion, intrauterine transplantation of fetal MSCs markedly reduced fracture rates and skeletal abnormalities in a mouse model of the intermediate severity type III OI, suggesting a scientific basis for MSC treatment of affected human fetuses.

Mesenchymal stem cells in cancer: tumor-associated fibroblasts and cell-based delivery vehicles

Recent evidence suggests that mesenchymal stem cells (MSC) selectively home to tumors, where they contribute to the formation of tumor-associated stroma. This effect can be opposed by genetically modifying MSC to produce high levels of anti-cancer agents that blunt tumor growth kinetics and inhibit the growth of tumors in situ. In this review article, we describe the biological properties of MSC within the tumor microenvironment and discuss the potential use of MSC and other bone marrow-derived cell populations as delivery vehicles for antitumor proteins.

Osterix induces osteogenic gene expression but not differentiation in primary human fetal mesenchymal stem cells

The transcription factor osterix (Osx) is a key regulator of osteoblast differentiation and induces bone formation in embryonic but not adult stem cells. We investigated the effect of up-regulating Osx on an intermediate stem cell type, first trimester fetal mesenchymal stem cells (MSCs), which are more expandable than adult MSCs. Human fetal (hf ) MSCs were transduced with a lentiviral vector encoding human Osx. In undifferentiating MSCs cultures, forced expression of Osx stimulated osteopontin and alkaline phosphatase expression. However, Osx did not up-regulate osteocalcin, a late marker of osteoblast differentiation or result in extracellular calcium crystals, indicating that Osx does not directly mediate terminal differentiation in primary hfMSCs. To understand the downstream effects of Osx expression in primary hfMSCs, we next investigated the regulatory relationship between Osx, and the transcription factors Dlx5, Runx2, and Msx2. Osx induced Dlx5 but did not affect Runx2 and Msx2, whereas stealth ribonucleic acid interference of Osx inhibited Dlx5 without affecting expression of Runx2 and Msx2. In conclusion, Osx regulates osteogenic gene expression in hfMSCs but is insufficient to induce terminal osteogenic differentiation.

Recent advances in delivery systems for anti-HIV1 therapy

In the last years, different non-biological and biological carrier systems have been developed for anti-HIV1 therapy. Liposomes are excellent potential anti-HIV1 carriers that have been tested with drugs, antisense oligonucleotides, ribozymes and therapeutic genes. Nanoparticles and low-density lipoproteins (LDLs) are cell-specific transporters of drugs against macrophage-specific infections such as HIV1. Through a process of protein transduction, cell-permeable peptides of natural origin or designed artificially allow the delivery of drugs and genetic material inside the cell. Erythrocyte ghosts and bacterial ghosts are a promising delivery system for therapeutic peptides and HIV vaccines. Of interest are the advances made in the field of HIV gene therapy by the use of autologous haematopoietic stem cells and viral vectors for HIV vaccines. Although important milestones have been reached in the development of carrier systems for the treatment of HIV, especially in the field of gene therapy, further clinical trials are required so that the efficiency and safety of these new systems can be guaranteed in HIV patients.

Murine but not human mesenchymal stem cells generate osteosarcoma-like lesions in the lung

Murine mesenchymal stem cells are capable of differentiation into multiple cell types both in vitro and in vivo and may be good candidates to use as cell therapy for diseased or damaged organs. We have previously reported a method of enriching a population of murine MSCs that demonstrated a diverse differentiation potential both in vitro and in vivo. In this study, we show that this enriched population of murine mesenchymal stem cells embolize within lung capillaries following systemic injection and then rapidly expand within, and invade into, the lung parenchyma, forming tumor nodules. These lesions rarely contain cells bearing the immunohistochemical characteristics of lung epithelium, but they do show the characteristics of immature bone and cartilage that resembles exuberant fracture callus or well-differentiated osteosarcoma. Our findings indicate that murine mesenchymal stem cells can behave in a manner similar to tumor cells, with dysregulated growth and aberrant differentiation within the alveolar microenvironment after four passages. We demonstrate that unlike human MSCs, MSCs from different mouse strains can acquire chromosomal abnormalities after only a few in vitro passages. Moreover, other parameters, such as mouse strain used, might also play a role in the induction of these tumors. These findings might be clinically relevant for future stem cell therapy studies. Disclosure of potential conflicts of interest is found at the end of this article.