Efficient adenoviral-mediated gene delivery into porcine mesenchymal stem cells

K2 Transfection System Boosts the Adenoviral Transduction of Murine Mesenchymal Stromal Cells

Adenoviral vectors are important vehicles for delivering therapeutic genes into mammalian cells. However, the yield of the adenoviral transduction of murine mesenchymal stromal cells (MSC) is low. Here, we aimed to improve the adenoviral transduction efficiency of bone marrow-derived MSC. Our data showed that among all the potential transduction boosters that we tested, the K2 Transfection System (K2TS) greatly increased the transduction efficiency. After optimization of both K2TS components, the yield of the adenoviral transduction increased from 18% to 96% for non-obese diabetic (NOD)-derived MSC, from 30% to 86% for C57BL/6-derived MSC, and from 0.6% to 63% for BALB/c-derived MSC, when 250 transduction units/cell were used. We found that MSC derived from these mouse strains expressed different levels of the coxsackievirus and adenovirus receptors (MSC from C57BL/6≥NOD>>>BALB/c). K2TS did not increase the level of the receptor expression, but desensitized the cells to foreign DNA and facilitated the virus entry into the cell. The expression of Stem cells antigen-1 (Sca-1) and 5'-nucleotidase (CD73) MSC markers, the adipogenic and osteogenic differentiation potential, and the immunosuppressive capacity were preserved after the adenoviral transduction of MSC in the presence of the K2TS. In conclusion, K2TS significantly enhanced the adenoviral transduction of MSC, without interfering with their main characteristics and properties.

Therapeutic Mesenchymal Stromal Cells for Immunotherapy and for Gene and Drug Delivery

Mesenchymal stromal cells (MSCs) possess several fairly unique properties that, when combined, make them ideally suited for cellular-based immunotherapy and as vehicles for gene and drug delivery for a wide range of diseases and disorders. Key among these are: (1) their relative ease of isolation from a variety of tissues; (2) the ability to be expanded in culture without a loss of functionality, a property that varies to some degree with tissue source; (3) they are relatively immune-inert, perhaps obviating the need for precise donor/recipient matching; (4) they possess potent immunomodulatory functions that can be tailored by so-called licensing in vitro and in vivo; (5) the efficiency with which they can be modified with viral-based vectors; and (6) their almost uncanny ability to selectively home to damaged tissues, tumors, and metastases following systemic administration. In this review, we summarize the latest research in the immunological properties of MSCs, their use as immunomodulatory/anti-inflammatory agents, methods for licensing MSCs to customize their immunological profile, and their use as vehicles for transferring both therapeutic genes in genetic disease and drugs and genes designed to destroy tumor cells.

Rodents Versus Pig Model for Assessing the Performance of Serotype Chimeric Ad5/3 Oncolytic Adenoviruses

Oncolytic adenoviruses (Ad) are promising tools for cancer therapeutics. Most Ad-based therapies utilize species C serotypes, with Adenovirus type 5 (Ad5) most commonly employed. Prior clinical trials demonstrated low efficiency of oncolytic Ad5 vectors, mainly due to the absence of Ad5 primary receptor (Coxsackie and Adenovirus Receptor, CAR) on cancer cells. Engineering serotype chimeric vectors (Ad5/3) to utilize Adenovirus type 3 (Ad3) receptors has greatly improved their oncolytic potential. Clinical translation of these infectivity-enhanced vectors has been challenging due to a lack of replication permissive animal models. In this study, we explored pigs as a model to study the performance of fiber-modified Ad5/3 chimeric vectors. As a control, the Ad5 fiber-unmodified virus was used. We analyzed binding, gene transfer, replication, and cytolytic ability of Ad5 and Ad5/3 in various non-human cell lines (murine, hamster, canine, porcine). Among all tested cell lines only porcine cells supported active binding and replication of Ad5/3. Syrian hamster cells supported Ad5 replication but showed no evidence of productive viral replication after infection with Ad5/3 vectors. Transduction and replication ability of Ad5/3 in porcine cells outperformed Ad5, a phenomenon often observed in human cancer cell lines. Replication of Ad5 and Ad5/3 was subsequently evaluated in vivo in immunocompetent pigs. Quantitative PCR analyses 7 days post infection revealed Ad5 and Ad5/3 DNA and replication-dependent luciferase activity in the swine lungs and spleen indicating active replication in these tissues. These studies demonstrated the flaws in using Syrian hamsters for testing serotype chimeric Ad5/3 vectors. This is the first report to validate the pig as a valuable model for preclinical testing of oncolytic adenoviruses utilizing Adenovirus type 3 receptors. We hope that these data will help to foster the clinical translation of oncolytic adenoviruses including those with Ad3 retargeted tropism.

Effects of Adenoviral Gene Transduction on the Stemness of Human Bone Marrow Mesenchymal Stem Cells

Human mesenchymal stem cells (MSCs) are currently being evaluated as a cell-based therapy for tissue injury and degenerative diseases. Recently, several methods have been suggested to further enhance the therapeutic functions of MSCs, including genetic modifications with tissue- and/or disease-specific genes. The objective of this study was to examine the efficiency and stability of transduction using an adenoviral vector in human MSCs. Additionally, we aimed to assess the effects of transduction on the proliferation and multipotency of MSCs. The results indicate that MSCs can be transduced by adenoviruses in vitro, but high viral titers are necessary to achieve high efficiency. In addition, transduction at a higher multiplicity of infection (MOI) was associated with attenuated proliferation and senescence-like morphology. Furthermore, transduced MSCs showed a diminished capacity for adipogenic differentiation while retaining their potential to differentiate into osteocytes and chondrocytes. This work could contribute significantly to clinical trials of MSCs modified with therapeutic genes.

Homing and restorative effects of bone marrow-derived mesenchymal stem cells on cisplatin injured ovaries in rats

Premature ovarian failure (POF) is a long-term adverse effect of chemotherapy treatment. However, current available treatment regimens are not optimal. Emerging evidence suggests that bone marrow-derived mesenchymal stem cells (BMSCs) could restore the structure and function of injured tissues, but the homing and restorative effects of BMSCs on chemotherapy injured ovaries are still not clear. In this study, we found that granulosa cell (GC) apoptosis induced by cisplatin was reduced when BMSCs were migrated to granulosa cells (GCs) in vitro. Chemotherapy-induced POF was induced by intraperitoneal injection of cisplatin in rats. BMSCs labeled with enhanced green fluorescent protein (EGFP) were injected into the rats via the tail vein to investigate the homing and distribution of BMSCs in vivo. The number of BMSCs in the ovarian hilum and medulla was greater than in the cortex, but no BMSCs were found in the follicles and corpus lutea. In addition, the BMSCs treatment group's antral follicle count and estradiol levels increased after 30 days, compared with the POF group. Hence, our study demonstrates that intravenously delivered BMSCs can home to the ovaries, and restore its structure and function in POF model rats.

Differential effects of extracellular vesicles secreted by mesenchymal stem cells from different sources on glioblastoma cells

BACKGROUND

Malignant glial tumors, including glioblastoma multiforme, account for 15 - 20% of pediatric CNS malignancies. They are most resistant to therapy and are associated with a poor prognosis.

OBJECTIVE

Given the ability of mesenchymal stem cells (MSCs) to affect glioma growth, we investigated the effects of extracellular vesicles (EVs) derived from MSCs on U87MG glioblastoma cells line.

METHODS

EVs were isolated from culture media of MSCs from different sources, including bone marrow (BM), umbilical cord (UC) and adipose tissue (AT) and added to U87MG culture. The internalization and the effects of BM-, UC- and AT-MSC-EVs on proliferation and apoptosis of tumor cells were evaluated.

RESULTS

Both confocal microscopy and FACS analysis showed internalization of EVs into tumor cells. BM- and UC-MSC-EVs decreased cell proliferation, while an opposite effect was observed with AT-MSC-EVs. Moreover, both BM- and UC-MSC-EVs induced apoptosis of glioblastoma cells, while AT-MSC-EVs had no effect. Loading UC-MSC-EVs with Vincristine further increased cytotoxicity when compared both to the free drug and to untreated EVs.

CONCLUSIONS

Different effects of MSC-EVs on cancer cells were observed depending on their tissue of origin. Moreover, MSC-EVs can deliver antiblastic drugs to glioblastoma cells.

Hemophilia A: an ideal disease to correct in utero

Hemophilia A (HA) is the most frequent inheritable defect of the coagulation proteins. The current standard of care for patients with HA is prophylactic factor infusion, which is comprised of regular (2-3 times per week) intravenous infusions of recombinant or plasma-derived FVIII to maintain hemostasis. While this treatment has greatly increased the quality of life and lengthened the life expectancy for many HA patients, its high cost, the need for lifelong infusions, and the fact that it is unavailable to roughly 75% of the world's HA patients make this type of treatment far from ideal. In addition, this lifesaving therapy suffers from a high risk of treatment failure due to immune response to the infused FVIII. There is thus a need for novel treatments, such as those using stem cells and/or gene therapy, which have the potential to mediate long-term correction or permanent cure following a single intervention. In the present review, we discuss the clinical feasibility and unique advantages that an in utero approach to treating HA could offer, placing special emphasis on a new sheep model of HA we have developed and on the use of mesenchymal stromal cells (MSC) as cellular vehicles for delivering the FVIII gene.

Effects of Transplantation of hTIMP-1-Expressing Bone Marrow Mesenchymal Stem Cells on the Extracellular Matrix of Degenerative Intervertebral Discs in an In Vivo Rabbit Model

STUDY DESIGN

Prospective, randomized, and controlled animal study.

OBJECTIVE

To observe extracellular matrix (ECM) changes in degenerative intervertebral disc (IVD) after transplantation of bone marrow mesenchymal stem cells (BMSCs) virally transfected with a construct expressing "human tissue inhibitor of metalloproteinase 1" (hTIMP-1), and to discuss the feasibility of using this approach to treat IVD degeneration.

SUMMARY OF BACKGROUND DATA

Intervertebral disc (IVD) degeneration is characterized by decreased cell numbers, bioactivity of the nucleus pulposus, and remodeled ECM. Exogenous genes can be targeted into cells to produce inhibition of ECM degradation and increase ECM content in IVDs, and thereby potentially stop or reverse degenerative processes and modify disc structure.

METHODS

BMSCs were isolated from a pure New Zealand white rabbit and identified by flow cytometry. Transgenic BMSCs were acquired by transfection with a recombinant adenovirus vector carrying the hTIMP-1 gene. Animal models of IVD degeneration were established by annulus puncture and then given intra-nucleus pulposus injections according to their random assignment into 3 groups: (1) a transgenic BMSC transplantation (TgBT) group that received BMSCs transfected with an hTIMP-1-expressing adenovirus vector; (2) a BMSC transplantation (BT) group that received unaltered BMSCs; and (3) a control group that received cell-free phosphate-buffered saline. Degree of degeneration was evaluated 12 weeks after modeling. ECM content was quantified using immunohistochemistry and spectrophotography. Expression of hTIMP-1 was observed via quantitative polymerase chain reaction, western blot, and immunohistochemistry.

RESULTS

Significantly fewer degenerative changes and increased ECM content were observed in the TBT and BT groups than the control group animals (P < 0.05). The TBT group had greater ECM content than did the BT group (P < 0.05), as well as higher levels of hTIMP-1 mRNA and protein.

CONCLUSION

Transplantation of BMSCs transfected with hTIMP-1 can increase ECM content by inhibiting ECM degradation and promoting ECM synthesis.

LEVEL OF EVIDENCE

N/A.

Generation of mouse induced pluripotent stem cells by protein transduction

Somatic cell reprogramming has generated enormous interest after the first report by Yamanaka and his coworkers in 2006 on the generation of induced pluripotent stem cells (iPSCs) from mouse fibroblasts. Here we report the generation of stable iPSCs from mouse fibroblasts by recombinant protein transduction (Klf4, Oct4, Sox2, and c-Myc), a procedure designed to circumvent the risks caused by integration of exogenous sequences in the target cell genome associated with gene delivery systems. The recombinant proteins were fused in the frame to the glutathione-S-transferase tag for affinity purification and to the transactivator transcription-nuclear localization signal polypeptide to facilitate membrane penetration and nuclear localization. We performed the reprogramming procedure on embryonic fibroblasts from inbred (C57BL6) and outbred (ICR) mouse strains. The cells were treated with purified proteins four times, at 48-h intervals, and cultured on mitomycin C treated mouse embryonic fibroblast (MEF) cells in complete embryonic stem cell (ESC) medium until colonies formed. The iPSCs generated from the outbred fibroblasts exhibited similar morphology and growth properties to ESCs and were sustained in an undifferentiated state for more than 20 passages. The cells were checked for pluripotency-related markers (Oct4, Sox2, Klf4, cMyc, Nanog) by immunocytochemistry and by reverse transcription-polymerase chain reaction. The protein iPSCs (piPSCs) formed embryoid bodies and subsequently differentiated towards all three germ layer lineages. Importantly, the piPSCs could incorporate into the blastocyst and led to variable degrees of chimerism in newborn mice. These data show that recombinant purified cell-penetrating proteins are capable of reprogramming MEFs to iPSCs. We also demonstrated that the cells of the generated cell line satisfied all the requirements of bona fide mouse ESCs: form round colonies with defined boundaries; have a tendency to attach together with high nuclear/cytoplasmic ratio; express key pluripotency markers; and are capable of in vitro differentiation into ecto-, endo-, and mesoderm, and in vivo chimera formation.

An MRI-visible non-viral vector bearing GD2 single chain antibody for targeted gene delivery to human bone marrow mesenchymal stem cells

The neural ganglioside GD2 has recently been reported to be a novel surface marker that is only expressed on human bone marrow mesenchymal stem cells within normal marrow. In this study, an MRI-visible, targeted, non-viral vector for effective gene delivery to human bone marrow mesenchymal stem cells was first synthesized by attaching a targeting ligand, the GD2 single chain antibody (scAb_GD2), to the distal ends of PEG-g-PEI-SPION. The targeted vector was then used to condense plasmid DNA to form nanoparticles showing stable small size, low cytotoxicity, and good biocompatibility. Based on a reporter gene assay, the transfection efficiency of targeting complex reached the highest value at 59.6% ± 4.5% in human bone marrow mesenchymal stem cells, which was higher than those obtained using nontargeting complex and lipofectamine/pDNA (17.7% ± 2.9% and 34.9% ± 3.6%, respectively) (P<0.01). Consequently, compared with the nontargeting group, more in vivo gene expression was observed in the fibrotic rat livers of the targeting group. Furthermore, the targeting capacity of scAb_GD2-PEG-g-PEI-SPION was successfully verified in vitro by confocal laser scanning microscopy, Prussian blue staining, and magnetic resonance imaging. Our results indicate that scAb_GD2-PEG-g-PEI-SPION is a promising MRI-visible non-viral vector for targeted gene delivery to human bone marrow mesenchymal stem cells.

Treatment of Hemophilia A in Utero and Postnatally using Sheep as a Model for Cell and Gene Delivery

Hemophilia A represents the most common inheritable deficiency of the coagulation proteins. Current state-of- the-art treatment consists of frequent prophylactic infusions of plasma-derived or recombinant FVIII protein to maintain hemostasis, and has greatly increased life expectancy and quality of life for many hemophilia A patients. This treatment approach is, however, far from ideal, due to the need for lifelong intravenous infusions, the high treatment cost, and the fact that it is unavailable to a large percentage of the world's hemophiliacs. There is thus a need for novel treatments that can promise long-term or permanent correction. In contrast to existing protein based therapeutics, gene therapy offers to provide a permanent cure following few, or even a single, treatment. In the present paper, we review ongoing work towards this end, focusing on studies we have performed in a large animal model. Some of the key topics covered in this review include the unique opportunities sheep offer as a model system, the re-establishment and clinical and molecular characterization of a line of sheep with severe hemophilia A, the advantages and feasibility of treating a disease like hemophilia A in utero, and the use of Mesenchymal Stem Cells (MSC) as cellular delivery vehicles for the FVIII gene. The review finishes with a brief discussion of our recent success correcting ovine hemophilia A with a postnatal transplant with gene-modified MSC, and the limitations of this approach that remain to be overcome.

JNK inhibitors increase osteogenesis in Nf1-deficient cells

Neurofibromatosis type 1 (NF1) is an autosomal dominant disorder that is associated with a variety of manifestations, including orthopedic complications such as scoliosis and tibial pseudarthrosis. Orthopedic management of these skeletal complications is rendered more challenging due to a lack of standardized adjunctive pharmacotherapies. NF1 leads to disruption of the canonical Ras/Raf-1/MEK/ERK axis, and this has been associated with defects in bone anabolism. The roles of other non-canonical Ras effector pathways, such as the c-Jun N-terminal Kinase (JNK) pathway, are less well understood. In this study we examine the effects of an anthrapyrazolone inhibitor of JNK (SP600125) on inducible osteoprogenitors as well as Nf1-deficient and Nf1-null primary osteoblasts. C2C12 cells, which are highly responsive to rhBMP-2, were examined with exogenous rhBMP-2 and a range of SP600125 doses. Based on the expression of early and late bone markers and matrix mineralization, 10 μM SP600125 was found to be pro-osteogenic whether delivered concurrent with or following 2 days of rhBMP-2 treatment. Aberrant JNK activity was identified in Nf1-deficient osteoprogenitors (increased rhBMP-2 induced phospho-c-Jun) and in Nf1-null mature osteoblasts (increased total c-Jun). Next, SP600125 was used to treat these cells and was found to facilitate osteogenesis in Nf1-deficient osteoprogenitors, and in Nf1-null osteoblasts when given in conjunction with rhBMP-2. Outcome measures included alkaline phosphatase activity, matrix mineralization, and osteogenic gene expression. In summary, JNK inhibitors represent a class of potentially useful adjunctive agents for orthopedic medicine, particularly in the context of NF1.

Synthesis and evaluation of an anti-MLC1 × anti-CD90 bispecific antibody for targeting and retaining bone-marrow-derived multipotent stromal cells in infarcted myocardium

A key issue regarding the use of stem cells in cardiovascular regenerative medicine is their retention in target tissues. Here, we have generated and assessed a bispecific antibody heterodimer designed to improve the retention of bone-marrow-derived multipotent stromal cells (BMMSC) in cardiac tissue damaged by myocardial infarction. The heterodimer comprises an anti-human CD90 monoclonal antibody (mAb) (clone 5E10) and an anti-myosin light chain 1 (MLC1) mAb (clone MLM508) covalently cross-linked by a bis-arylhydrazone. We modified the anti-CD90 antibody with a pegylated-4-formylbenzamide moiety to a molar substitution ratio (MSR) of 2.6 and the anti-MLC1 antibody with a 6-hydrazinonicotinamide moiety to a MSR of 0.9. The covalent modifications had no significant deleterious effect on mAb epitope binding. Furthermore, the binding of anti-CD90 antibody to BMMSCs did not prevent their differentiation into adipo-, chondro-, or osteogenic lineages. Modified antibodies were combined under mild conditions (room temperature, pH 6, 1 h) in the presence of a catalyst (aniline) to allow for rapid generation of the covalent bis-arylhydrazone, which was monitored at A(354). We evaluated epitope immunoreactivity for each mAb in the construct. Flow cytometry demonstrated binding of the bispecific construct to BMMSCs that was competed by free anti-CD90 mAb, verifying that modification and cross-linking were not detrimental to the anti-CD90 complementarity-determining region. Similarly, ELISA-based assays demonstrated bispecific antibody binding to plastic-immobilized recombinant MLC1. Excess anti-MLC1 mAb competed for bispecific antibody binding. Finally, the anti-CD90 × anti-MLC1 bispecific antibody construct induced BMMSC adhesion to plastic-immobilized MLC1 that was resistant to shear stress, as measured in parallel-plate flow chamber assays. We used mAbs that bind both human antigens and the respective pig homologues. Thus, the anti-CD90 × anti-MLC1 bispecific antibody may be used in large animal studies of acute myocardial infarction and may provide a starting point for clinical studies.

Porcine induced pluripotent stem cells produce chimeric offspring

Ethical and moral issues rule out the use of human induced pluripotent stem cells (iPSCs) in chimera studies that would determine the full extent of their reprogrammed state, instead relying on less rigorous assays such as teratoma formation and differentiated cell types. To date, only mouse iPSC lines are known to be truly pluripotent. However, initial mouse iPSC lines failed to form chimeric offspring, but did generate teratomas and differentiated embryoid bodies, and thus these specific iPSC lines were not completely reprogrammed or truly pluripotent. Therefore, there is a need to address whether the reprogramming factors and process used eventually to generate chimeric mice are universal and sufficient to generate reprogrammed iPSC that contribute to chimeric offspring in additional species. Here we show that porcine mesenchymal stem cells transduced with 6 human reprogramming factors (POU5F1, SOX2, NANOG, KLF4, LIN28, and C-MYC) injected into preimplantation-stage embryos contributed to multiple tissue types spanning all 3 germ layers in 8 of 10 fetuses. The chimerism rate was high, 85.3% or 29 of 34 live offspring were chimeras based on skin and tail biopsies harvested from 2- to 5-day-old pigs. The creation of pluripotent porcine iPSCs capable of generating chimeric offspring introduces numerous opportunities to study the facets significantly affecting cell therapies, genetic engineering, and other aspects of stem cell and developmental biology.

Mesenchymal stem cells as therapeutics and vehicles for gene and drug delivery

Mesenchymal stem cells (MSCs) possess a set of several fairly unique properties which make them ideally suited both for cellular therapies/regenerative medicine, and as vehicles for gene and drug delivery. These include: 1) relative ease of isolation; 2) the ability to differentiate into a wide variety of seemingly functional cell types of both mesenchymal and non-mesenchymal origin; 3) the ability to be extensively expanded in culture without a loss of differentiative capacity; 4) they are not only hypoimmunogenic, but they produce immunosuppression upon transplantation; 5) their pronounced anti-inflammatory properties; and 6) their ability to home to damaged tissues, tumors, and metastases following in vivo administration. In this review, we summarize the latest research in the use of mesenchymal stem cells in regenerative medicine, as immunomodulatory/anti-inflammatory agents, and as vehicles for transferring both therapeutic genes in genetic disease and genes designed to destroy malignant cells.

Directing systemic oncolytic viral delivery to tumors via carrier cells

The systemic administration of oncolytic virus (OV) is often inefficient due to clearance of the virus by host defense mechanism and spurious targeting of non-cancer tissues through the bloodstream. Cell mediated OV delivery could hide the virus from host defenses and direct them toward tumors: Mesenchymal and neural stem cells have been described to possess tumor-homing ability as well as the capacity to deliver OVs. In this review, we will focus on approaches where OV and carrier cells are utilized for cancer therapy. Effective cellular internalization and replication of OVs need to occur both in cancer and carrier cells. We thus will discuss the current challenges faced by the use of OV delivery via carrier cells.

Large-scale bicortical skull bone regeneration using ex vivo replication-defective adenoviral-mediated bone morphogenetic protein-2 gene-transferred bone marrow stromal cells and composite biomaterials

OBJECTIVE

Bone marrow stromal cells (BMSCs) have great potential in bone repair. We developed an animal model to test the hypothesis that ex vivo gene transfer of human bone morphogenetic protein (BMP)-2 to BMSCs via a replication-defective (E1A-deleted) adenovirus vector (AdV) with appropriate biopolymers would enhance autologous bone formation during repair of a large-scale skull defect.

METHODS

Eighteen miniature swine were treated with AdV BMP-2-transduced BMSCs in biopolymer (group 1), BMSCs in biopolymer (group 2), or biopolymer alone (group 3). After 6 months, the swine were killed, and the skull repair was examined by gross pictures, histology, 3-dimensional computed tomography, and biomechanical study.

RESULTS

Group 1 showed complete solid bone formation after 6 months, and hematoxylin and eosin staining demonstrated the presence of mature, woven, well-mineralized bone. Computed tomography showed wholesome repair of the skull defect. Statistical analysis demonstrated a significant difference in bone thickness between groups 1 and 2. Biomechanical testing showed a statistically significant difference in the stiffness of new bone formed in group 1 compared with group 2.

CONCLUSION

The Ad5 E1A-deleted AdV may be the optimal starting vector in ex vivo gene therapy for benign skeletal diseases. Additionally, the use of the gelatin/tricalcium phosphate ceramic/glutaraldehyde biopolymer with AdV BMP-2 gene transfer strongly enhances the bony healing of critical-size bicortical craniofacial defects. This method can be used by modifying the delivery of constructs to malunion treatment, in regional osteoporosis therapy, and spinal fusion.

Human embryonic stem cell-derived mesoderm-like epithelium transitions to mesenchymal progenitor cells

Human embryonic stem cells (hESC) have the potential to produce all of the cells in the body. They are able to self-renew indefinitely, potentially making them a source for large-scale production of therapeutic cell lines. Here, we developed a monolayer differentiation culture that induces hESC (WA09 and BG01) to form epithelial sheets with mesodermal gene expression patterns (BMP4, RUNX1, and GATA4). These E-cadherin+ CD90low cells then undergo apparent epithelial-mesenchymal transition for the derivation of mesenchymal progenitor cells (hESC-derived mesenchymal cells [hES-MC]) that by flow cytometry are negative for hematopoietic (CD34, CD45, and CD133) and endothelial (CD31 and CD146) markers, but positive for markers associated with mesenchymal stem cells (CD73, CD90, CD105, and CD166). To determine their functionality, we tested their capacity to produce the three lineages associated with mesenchymal stem cells and found they could form osteogenic and chondrogenic, but not adipogenic lineages. The derived hES-MC were able to remodel and contract collagen I lattice constructs to an equivalent degree as keloid fibroblasts and were induced to express alpha-smooth muscle actin when exposed to transforming growth factor (TGF)-beta1, but not platelet derived growth factor-B (PDGF-B). These data suggest that the derived hES-MC are multipotent cells with potential uses in tissue engineering and regenerative medicine and for providing a highly reproducible cell source for adult-like progenitor cells.

Application of genetically modified and cloned pigs in translational research

Pigs are increasingly being recognized as good large-animal models for translational research, linking basic science to clinical applications in order to establish novel therapeutics. This article reviews the current status and future prospects of genetically modified and cloned pigs in translational studies. It also highlights pigs specially designed as disease models, for xenotransplantation or to carry cell marker genes. Finally, use of porcine somatic stem and progenitor cells in preclinical studies of cell transplantation therapy is also discussed.

Coculture of bone marrow mesenchymal stem cells and nucleus pulposus cells modulate gene expression profile without cell fusion

STUDY DESIGN

Changes in gene expression profile and cell fusion of mesenchymal stem cells (MSC) and nucleus pulposus cells (NPC) after coculture were analyzed.

OBJECTIVE

To investigate the mechanisms of the interaction between NPC and MSC such us differentiation, stimulatory effect, and cell fusion.

SUMMARY OF BACKGROUND DATA

Introduction of exogenous cells to supplement and replenish intervertebral disc cell population offers a potential approach to treat intervertebral disc degeneration (IDD). Recent evidences showed that intradiscal injection of MSC effectively alter the course of IDD in vivo, and the regenerative potential may result from up-regulated extracellular matrix protein synthesis mediated by MSC and NPC interaction.

METHODS

Using a double labeling cell system and flow activated cell sorting, we quantitatively analyzed changes in the gene expression profile of human male MSC and female NPC after coculture in a 3-dimensional system that allows short distance paracrine interactions typical of the nucleus pulposus. Furthermore, we analyzed for cell fusion in the cell interaction by fluorescence in situ hybridization (FISH) for X and Y chromosomes, using a 3-dimensional culture system to allow cell-to-cell interactions conducive to cell fusion.

RESULTS

Two weeks of coculture cell interaction in a 3-dimensional environment induces a change in MSCs towards a more chondrogenic gene expression profile indicating MSC differentiation, and NPC gene expression changes in matrix and chondrogenic genes demonstrating only a modest trophic effect of MSC on NPC. Moreover, FISH analysis demonstrated that cell fusion is not responsible for MSC plasticity in the interaction with NPCs.

CONCLUSION

This study clarifies the mechanism of MSCs and NPCs interaction in a 3-dimensional environment, excluding cell fusion. These data support the use of undifferentiated MSC for stem cell therapy for IDD treatment.

A simple, lanthanide-based method to enhance the transduction efficiency of adenovirus vectors

Based upon the powerful bridging and charge-masking properties of lanthanide cations (Ln3+), we have investigated their use to improve the transduction efficiency of adenovirus vectors. Using a luciferase marker gene, it was possible to increase transgene expression by the murine mesenchymal stem cell line C3H10T(1/2) by up to four log orders when using very low multiplicities of infection in conjunction with Ln3+; La3+ was superior to Gd3+, Y3+ and Lu3+ in this regard. All Ln3+ were more effective than Ca2+. Flow cytometry, using a green fluorescent protein marker gene, confirmed that La3+ increased both the percentage of transduced cells and the level of transgene expression per cell. Transduction of primary cultures of a variety of different mesenchymal cells from human, rabbit, bovine and rat sources, as well as gene transfer to synovium and muscle in vivo, was also greatly enhanced. Our findings suggest that this lanthanide-based method holds much promise for expediting both experimental and clinical applications of gene transfer with adenoviral vectors.

Pigs taking wing with transposons and recombinases

Swine production has been an important part of our lives since the late Mesolithic or early Neolithic periods, and ranks number one in world meat production. Pig production also contributes to high-value-added medical markets in the form of pharmaceuticals, heart valves, and surgical materials. Genetic engineering, including the addition of exogenous genetic material or manipulation of the endogenous genome, holds great promise for changing pig phenotypes for agricultural and medical applications. Although the first transgenic pigs were described in 1985, poor survival of manipulated embryos; inefficiencies in the integration, transmission, and expression of transgenes; and expensive husbandry costs have impeded the widespread application of pig genetic engineering. Sequencing of the pig genome and advances in reproductive technologies have rejuvenated efforts to apply transgenesis to swine. Pigs provide a compelling new resource for the directed production of pharmaceutical proteins and the provision of cells, vascular grafts, and organs for xenotransplantation. Additionally, given remarkable similarities in the physiology and size of people and pigs, swine will increasingly provide large animal models of human disease where rodent models are insufficient. We review the challenges facing pig transgenesis and discuss the utility of transposases and recombinases for enhancing the success and sophistication of pig genetic engineering. 'The paradise of my fancy is one where pigs have wings.' (GK Chesterton).

Efficient and rapid osteoinduction in an immune-competent host

Osteoinductive systems to induce targeted rapid bone formation hold clinical promise, but development of technologies for clinical use that must be tested in animal models is often a difficult challenge. We previously demonstrated that implantation of human cells transduced with Ad5F35BMP2 to express high levels of bone morphogenetic protein-2 (BMP2) resulted in rapid bone formation at targeted sites. Inclusion of human cells in this model precluded us from testing this system in an immune-competent animal model, thus limiting information about the efficacy of this approach. Here, for the first time we demonstrate the similarity between BMP2-induced endochondral bone formation in a system using human cells in an immune-incompetent mouse and a murine cell-based BMP2 gene therapy system in immune-competent animals. In both cases the delivery cells are rapidly cleared, within 5 days, and in neither case do they appear to contribute to any of the structures forming in the tissues. Endochondral bone formation progressed through a highly ordered series of stages that were both morphologically and temporally indistinguishable between the two models. Even longterm analysis of the heterotopic bone demonstrated similar bone volumes and the eventual remodeling to form similar structures. The results suggest that the ability of BMP2 to rapidly induce bone formation overrides contributions from either immune status or the nature of delivery cells.

Adenoviral transduction of mesenchymal stem cells

Intact or genetically manipulated mesnechymal stem cells (MSCs) are being considered an important cell source for developing human cell-based therapeutic approaches. For applications in which transient, high-level expression of the transgene is necessary, adenovirus vectors have become increasingly popular gene-transfer vehicles. However, host range and cell-type tropism restrict the use of specific adenovectors, sometimes necessitating the lengthy development of vectors with appropriate cell specificity. Here, we present a versatile and inexpensive porcine MSC transduction procedure that can also be used on other cell types from various species, including human that are otherwise refractory to adenovirus infection.