Genetically Engineered Stem Cell Therapy for Tissue Regeneration

CD34 positive cells as endothelial progenitor cells in biology and medicine

CD34 is a cell surface antigen expressed in numerous stem/progenitor cells including hematopoietic stem cells (HSCs) and endothelial progenitor cells (EPCs), which are known to be rich sources of EPCs. Therefore, regenerative therapy using CD34⁺ cells has attracted interest for application in patients with various vascular, ischemic, and inflammatory diseases. CD34⁺ cells have recently been reported to improve therapeutic angiogenesis in a variety of diseases. Mechanistically, CD34⁺ cells are involved in both direct incorporation into the expanding vasculature and paracrine activity through angiogenesis, anti-inflammatory, immunomodulatory, and anti-apoptosis/fibrosis roles, which support the developing microvasculature. Preclinical, pilot, and clinical trials have well documented a track record of safety, practicality, and validity of CD34⁺ cell therapy in various diseases. However, the clinical application of CD34⁺ cell therapy has triggered scientific debates and controversies in last decade. This review covers all preexisting scientific literature and prepares an overview of the comprehensive biology of CD34⁺ cells as well as the preclinical/clinical details of CD34⁺ cell therapy for regenerative medicine.

Genetically-Modified Stem Cell in Regenerative Medicine and Cancer Therapy; A New Era

Recently, genetic engineering by various strategies to stimulate gene expression in a specific and controllable mode is a speedily growing therapeutic approach. Genetic modification of human stem or progenitor cells, such as embryonic stem cells (ESCs), neural progenitor cells (NPCs), mesenchymal stem/stromal cells (MSCs), and hematopoietic stem cells (HSCs) for direct delivery of specific therapeutic molecules or genes has been evidenced as an opportune plan in the context of regenerative medicine due to their supported viability, proliferative features, and metabolic qualities. On the other hand, a large number of studies have investigated the efficacy of modified stem cells in cancer therapy using cells from various sources, disparate transfection means for gene delivery, different transfected yields, and wide variability of tumor models. Accordingly, cell-based gene therapy holds substantial aptitude for the treatment of human malignancy as it could relieve signs or even cure cancer succeeding expression of therapeutic or suicide transgene products; however, there exist inconsistent results in this regard. Herein, we deliver a brief overview of stem cell potential to use in cancer therapy and regenerative medicine and importantly discuss stem cells based gene delivery competencies to stimulate tissue repair and replacement in concomitant with their potential to use as an anti-cancer therapeutic strategy, focusing on the last two decades in vivo studies.

Recent advances and challenges on application of tissue engineering for treatment of congenital heart disease

Congenital heart disease (CHD) affects a considerable number of children and adults worldwide. This implicates not only developmental disorders, high mortality, and reduced quality of life but also, high costs for the healthcare systems. CHD refers to a variety of heart and vascular malformations which could be very challenging to reconstruct the malformed region surgically, especially when the patient is an infant or a child. Advanced technology and research have offered a better mechanistic insight on the impact of CHD in the heart and vascular system of infants, children, and adults and identified potential therapeutic solutions. Many artificial materials and devices have been used for cardiovascular surgery. Surgeons and the medical industry created and evolved the ball valves to the carbon-based leaflet valves and introduced bioprosthesis as an alternative. However, with research further progressing, contracting tissue has been developed in laboratories and tissue engineering (TE) could represent a revolutionary answer for CHD surgery. Development of engineered tissue for cardiac and aortic reconstruction for developing bodies of infants and children can be very challenging. Nevertheless, using acellular scaffolds, allograft, xenografts, and autografts is already very common. Seeding of cells on surface and within scaffold is a key challenging factor for use of the above. The use of different types of stem cells has been investigated and proven to be suitable for tissue engineering. They are the most promising source of cells for heart reconstruction in a developing body, even for adults. Some stem cell types are more effective than others, with some disadvantages which may be eliminated in the future.

Characterization of neural stem cells modified with hypoxia/neuron-specific VEGF expression system for spinal cord injury

Spinal cord injury (SCI) is an incurable disease causing an ischemic environment and functional defect, thus a new therapeutic approach is needed for SCI treatment. Vascular endothelial growth factor (VEGF) is a potent therapeutic gene to treat SCI via angiogenesis and neuroprotection, and both tissue-specific gene expression and high gene delivery efficiency are important for successful gene therapy. Here we design the hypoxia/neuron dual-specific gene expression system (pEpo-NSE) and efficient gene delivery platform can be achieved by the combination ex vivo gene therapy with erythropoietin (Epo) enhancer, neuron-specific enolase (NSE) promoter and neural stem cells (NSCs). An in vitro model, NSCs transfected with pEpo-NSE were consistently and selectively overexpressing therapeutic genes in response to neural differentiation and hypoxic conditions. Also, in SCI model, ex vivo gene therapy using pEpo-NSE system with NSCs significantly enhanced gene delivery efficiency compared with pEpo-NSE system gene therapy alone. However, microarray analysis reveals that introducing exogenous pEpo-NSE and VEGF triggers biological pathways in NSCs such as glycolysis and signaling pathways such as Ras and mitogen-activated protein kinase, leading to cell proliferation, differentiation and apoptosis. Collectively, it indicates that the pEpo-NSE gene expression system works stably in NSCs and ex vivo gene therapy using pEpo-NSE system with NSCs improves gene expression efficiency. However, exogenously introduced pEpo-NSE system has an influence on gene expression profiles in NSCs. Therefore, when we consider ex vivo gene therapy for SCI, the effects of changes in gene expression profiles in NSCs on safety should be investigated.

Schwann cells promote the capability of neural stem cells to differentiate into neurons and secret neurotrophic factors

The present study investigated whether co-culturing Schwann cells (SCs) with neural stem cells (NSCs) improves viability, direction of differentiation and secretion of brain-derived neurotrophic factor (BDNF) and glial cell-derived neurotrophic factor (GDNF) in NSCs. The three groups assessed were as follows: SCs, NSCs, and a co-culture of SCs and NSCs. Cellular morphological changes were observed under an inverted phase contrast microscope and quantified. Cells were identified by immunofluorescence staining: S100 for SCs, Nestin for NSCs, microtubule associated protein (Map) 2 and NeuN for neurons and glial fibrillary acidic protein for astrocytes. Cell viability was evaluated by MTT assay. Secretion of BDNF and GDNF was quantified; mRNA expression was quantified by reverse transcription-quantitative polymerase chain reaction. The majority of NSCs in the co-cultured group differentiated into neurons. The cell survival rate of the co-culture group was significantly higher than the other groups on days 3, 5 and 10 (P<0.01). The secretion of BDNF in the co-culture group was significantly higher than NSCs on days 3, 5 and 7 (P<0.05), while the amount of GDNF in co-culture was significantly higher than both NSCs and SCs on day 1 (P<0.05). BDNF and GDNF gene expression in the co-culture group was significantly higher than SCs (P<0.01). Gene expression of Map2 in co-culture group was also significantly higher than both NSC and SC groups (P<0.01). Therefore, co-cultured SCs and NSCs promote differentiation of NSCs into neurons and secrete higher levels of neurotropic factors including BDNF and GDNF.

Progress in cell-based therapies for tendon repair

The last decade has seen significant developments in cell therapies, based on permanently differentiated, reprogrammed or engineered stem cells, for tendon injuries and degenerative conditions. In vitro studies assess the influence of biophysical, biochemical and biological signals on tenogenic phenotype maintenance and/or differentiation towards tenogenic lineage. However, the ideal culture environment has yet to be identified due to the lack of standardised experimental setup and readout system. Bone marrow mesenchymal stem cells and tenocytes/dermal fibroblasts appear to be the cell populations of choice for clinical translation in equine and human patients respectively based on circumstantial, rather than on hard evidence. Collaborative, inter- and multi-disciplinary efforts are expected to provide clinically relevant and commercially viable cell-based therapies for tendon repair and regeneration in the years to come.

Effect of calcitonin gene-related peptide on the neurogenesis of rat adipose-derived stem cells in vitro

Calcitonin gene-related peptide (CGRP) promotes neuron recruitment and neurogenic activity. However, no evidence suggests that CGRP affects the ability of stem cells to differentiate toward neurogenesis. In this study, we genetically modified rat adipose-derived stem cells (ADSCs) with the CGRP gene (CGRP-ADSCs) and subsequently cultured in complete neural-induced medium. The formation of neurospheres, cellular morphology, and proliferative capacity of ADSCs were observed. In addition, the expression of the anti-apoptotic protein Bcl-2 and special markers of neural cells, such as Nestin, MAP2, RIP and GFAP, were evaluated using Western blot and immunocytochemistry analysis. The CGRP-ADSCs displayed a greater proliferation than un-transduced (ADSCs) and Vector-transduced (Vector-ADSCs) ADSCs (p<0.05), and lower rates of apoptosis, associated with the incremental expression of Bcl-2, were also observed for CGRP-ADSCs. Moreover, upon neural induction, CGRP-ADSCs formed markedly more and larger neurospheres and showed round cell bodies with more branching extensions contacted with neighboring cells widely. Furthermore, the expression levels of Nestin, MAP2, and RIP in CGRP-ADSCs were markedly increased, resulting in higher levels than the other groups (p<0.05); however, GFAP was distinctly undetectable until day 7, when slight GFAP expression was detected among all groups. Wnt signals, primarily Wnt 3a, Wnt 5a and β-catenin, regulate the neural differentiation of ADSCs, and CGRP gene expression apparently depends on canonical Wnt signals to promote the neurogenesis of ADSCs. Consequently, ADSCs genetically modified with CGRP exhibit stronger potential for differentiation and neurogenesis in vitro, potentially reflecting the usefulness of ADSCs as seed cells in therapeutic strategies for spinal cord injury.

Experimental considerations concerning the use of stem cells and tissue engineering for facial nerve regeneration: a systematic review

PURPOSE

Peripheral nerve trauma results in functional loss in the innervated organ, and recovery without surgical intervention is rare. Many surgical techniques can be used for repair in experimental models. The authors investigated the source and delivery method of stem cells in experimental outcomes, seeking to clarify whether stem cells must be differentiated in the injured facial nerve and improve the regenerative process.

MATERIALS AND METHODS

The following key terms were used: nervous regeneration, nerve regeneration, facial nerve regeneration, stem cells, embryonic stem cells, fetal stem cells, adult stem cells, facial nerve, facial nerve trauma, and facial nerve traumatism. The search was restricted to experimental studies that applied stem cell therapy and tissue engineering for nerve repair.

RESULTS

Eight studies meeting the inclusion criteria were reviewed. Different sources of stem and precursor cells were explored (bone marrow mesenchymal stem cells, adipose-derived stem cells, dental pulp cells, and neural stem cells) for their potential application in the scenario of facial nerve injuries. Different material conduits (vases, collagen, and polyglycolic acid) were used as bridges. Immunochemistry and electrophysiology are the principal methods for analyzing regenerative effects. Although recent studies have shown that stem cells can act as a promising bridge for nerve repair, considerable optimization of these therapies will be required for their potential to be realized in a clinical setting.

CONCLUSION

Based on these studies, the use of stem cells derived from different sources presents promising results related to facial nerve regeneration and produces effective functional results. The use of tubes also optimizes nerve repair, thus promoting greater myelination and axonal growth of peripheral nerves.

Methodological Development of a Clonogenic Assay to Determine Endothelial Progenitor Cell Potential

The precise and conceptual insight of circulating endothelial progenitor cell (EPC) kinetics is hampered by the absence of an assay system capable of evaluating the EPC differentiation cascade. An assay system for EPC colony formation was developed to delineate circulating EPC differentiation. EPC colony-forming assay using semisolid medium and single or bulk CD133 + cells from umbilical cord blood exhibited the formation of two types of attaching cell colonies made of small or large cells featuring endothelial lineage potential and properties, termed small EPC colony-forming units and large EPC colony-forming units, respectively. In vitro and in vivo assays of each EPC colony-forming unit cell revealed a differentiation hierarchy from small EPC to large EPC colonies, indicating a primitive EPC stage with highly proliferative activity and a definitive EPC stage with vasculogenic properties, respectively. Experimental comparison with a conventional EPC culture assay system disclosed EPC colony-forming unit cells differentiate into noncolony-forming early EPC. The fate analysis of single CD133 + cells into the endothelial and hematopoietic lineage was achieved by combining this assay system with a hematopoietic progenitor assay and demonstrated the development of colony-forming EPC and hematopoietic progenitor cells from a single hematopoietic stem cell. EPC colony-forming assay permits the determination of circulating EPC kinetics from single or bulk cells, based on the evaluation of hierarchical EPC colony formation. This assay further enables a proper exploration of possible links between the origin of EPC and hematopoietic stem cells, representing a novel and powerful tool to investigate the molecular signaling pathways involved in EPC biology.

Construction of tissue engineered nerve grafts and their application in peripheral nerve regeneration

Surgical repair of severe peripheral nerve injuries represents not only a pressing medical need, but also a great clinical challenge. Autologous nerve grafting remains a golden standard for bridging an extended gap in transected nerves. The formidable limitations related to this approach, however, have evoked the development of tissue engineered nerve grafts as a promising alternative to autologous nerve grafts. A tissue engineered nerve graft is typically constructed through a combination of a neural scaffold and a variety of cellular and molecular components. The initial and basic structure of the neural scaffold that serves to provide mechanical guidance and optimal environment for nerve regeneration was a single hollow nerve guidance conduit. Later there have been several improvements to the basic structure, especially introduction of physical fillers into the lumen of a hollow nerve guidance conduit. Up to now, a diverse array of biomaterials, either of natural or of synthetic origin, together with well-defined fabrication techniques, has been employed to prepare neural scaffolds with different structures and properties. Meanwhile different types of support cells and/or growth factors have been incorporated into the neural scaffold, producing unique biochemical effects on nerve regeneration and function restoration. This review attempts to summarize different nerve grafts used for peripheral nerve repair, to highlight various basic components of tissue engineered nerve grafts in terms of their structures, features, and nerve regeneration-promoting actions, and finally to discuss current clinical applications and future perspectives of tissue engineered nerve grafts.

Application of neural stem cells in tissue-engineered artificial nerve

OBJECTIVE

To observe the curative effect of neural stem cells (NSCs), which are used in tissue-engineered artificial nerve, on repairing rabbit 10-mm facial nerve defects.

METHODS

Thirty-six Oryctolagus cuniculi were randomly divided into three groups (each group with 12 Oryctolagus cuniculi). In group A, chitosan conduit, collagen protein sponge, nerve growth factor (NGF), and NSCs were used. In group B, chitosan conduit, collagen sponge, and NGF were used. In group C, nerve autograft was performed. Electrophysiologic detection, histologic observation, and BrdU and S100 immunohistochemical examination were performed 12 weeks after operation.

RESULTS

All observation items in group A were better than those in group B (P < 0.01), and there were no significant differences between group A and group C (P > 0.05).

CONCLUSION

NSCs may be served as seed cells of peripheral nerve tissue engineering and be used in artificial nerve to repair facial nerve defects.

Growth and phenotypic expression of human endothelial cells cultured on a glass-reinforced hydroxyapatite

Glass-reinforced hydroxyapatite composites (GR-HA) are bone regenerative materials that are characterized by their increased mechanical properties, when compared to synthetic hydroxyapatite. Bonelike is a GR-HA that is a result of the addition of a CaO-P(2)O(5) based glass to a HA matrix. This biomaterial has been successfully applied in clinical bone regenerative applications. This work aims to evaluate the ability of Bonelike to support the adhesion, proliferation and phenotypic expression of human endothelial cells, aiming to establish new bone tissue engineering pre-endothelialization strategies. Bonelike discs, regardless of being submitted to a pre-immersion treatment with culture medium, were seeded with first passage human umbilical vein endothelial cells, and characterized regarding proliferation and differentiation events. Pre-immersed Bonelike allowed the adhesion, proliferation and phenotype expression of endothelial cells. Seeded materials presented positive immunofluorescent staining for PECAM-1 and a tendency for the formation of cord-like arrangements under angiogenesis-stimulating conditions, although, compared to standard culture plates, a slight decreased cell growth was observed. In this way, Bonelike may be a suitable candidate for pre-endothelialization approaches in bone tissue engineering applications.

Differentiation and dynamic analysis of primitive vessels from embryonic stem cells

Embryonic stem (ES) cells, which are derived from developing mouse blastocysts, have the ability to differentiate into various cell types in vitro. When placed in basal medium with added serum, mouse ES cells undergo a programmed differentiation favoring formation of cell types that are found in the embryonic yolk sac, including vascular endothelial cells. These in vitro differentiated endothelial cells form primitive blood vessels, analogous to the first vessels that form in the embryo and the yolk sac. This differentiation model is ideal for both genetic and pharmacological manipulation of early vascular development. We have made mouse ES cell lines that express endothelial-specific GFP or H2B-GFP and used these lines to study the processes of mammalian vessel development by real-time imaging. Here we describe protocols for making transgenic ES cells and imaging the processes of blood vessel development. We also provide methods for ES cell maintenance and differentiation, and methods for analysis of vascular marker expression.

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.

Mesenchymal stromal cells genetically engineered to overexpress IGF-I enhance cell-based gene therapy of renal failure-induced anemia

We previously demonstrated that erythropoietin (EPO)-secreting mesenchymal stromal cells (MSC) can be used for the long-term correction of renal failure-induced anemia. The present study provides evidence that coimplantation of insulin-like growth factor I (IGF-I)-overexpressing MSC (MSC-IGF) improves MSC-based gene therapy of anemia by providing paracrine support to EPO-secreting MSC (MSC-EPO) within a subcutaneous implant. IGF-I receptor RNA expression in murine MSC was demonstrated by RT-PCR. Functional protein expression was confirmed by immunoblots and MSC responsiveness to IGF-I stimulation in vitro. IGF-I was also shown to improve MSC survival following staurosporin-induced apoptosis in vitro. A cohort of C57Bl/6 mice was rendered anemic by right kidney electrocoagulation and left nephrectomy. MSC-EPO were subsequently admixed in a bovine collagen matrix and implanted, in combination with MSC-IGF or MSC null, by subcutaneous injection in renal failure mice. In mice receiving MSC-EPO coimplanted with MSC-IGF, hematocrit elevation was greater and enhanced compared with control mice; heart function was also improved. MSC-IGF coimplantation, therefore, represents a promising new strategy for enhancing MSC survival within implanted matrices and for improving cell-based gene therapy of renal anemia.

Strategies to enhance capillary formation inside biomaterials: a computational study

Control over angiogenesis (formation of new capillaries from preexisting vessels) is often a crucial requirement for implantable porous biomaterials serving as scaffolds for tissue regeneration. Angiogenesis is influenced by the transport of chemoattractants such as vascular endothelial growth factor (VEGF) through the implant. To investigate this influence, we developed a computational model of capillary formation based on endothelial cell migration by modeling the random motion of sprout tips biased along spatially and temporally evolving concentration gradients of VEGF. The model focuses on the effect of diffusive VEGF transport inside a 2D domain on the directed migration of sprouts to test several chemical and physical strategies to stimulate and control angiogenesis. We considered a 2D porous membrane that is located between the primary vessel and a line source of VEGF. We assess the vascular network formed in 2 cases of a high and zero VEGF degradation rates applying 3 strategies of VEGF production: (1) only a line source; (2) a line source plus controlled release from a small number of VEGF sources that are randomly dispersed on the pore boundaries; and (3) a line source plus controlled release of VEGF from the pore boundaries themselves. Results show that in the limiting cases where VEGF degradation rate is relatively high, strategies 2 and 3 lead to a substantial increase in the number of vessels. This increase depends on the relative rates at which the line source and embedded sources or solid boundaries produce VEGF. Using strategy 2 results in a newly formed capillary network that is highly localized around the embedded sources. However, using strategy 3 leads to a more uniformly distributed vessel network and a higher degree of vessel ingrowth inside the porous membrane. In addition, the duration at which we engineer the embedded sources or pore boundaries to release VEGF determines the morphology of the capillary network. Although a higher release duration leads to a dense network of newly formed vessels near the primary vessel, it hinders further vessel penetration inside the porous membrane. Therefore, in applying both strategies 2 and 3, there is an optimum release duration that leads to a deeper penetration of vessels inside the membrane. It is hoped that insights from this study will aid in the design of materials with optimal structural and chemical properties to facilitate controlled angiogenesis.

Mesenchymal stem cells modified with angiopoietin-1 improve remodeling in a rat model of acute myocardial infarction

We used human angiopoietin-1 (hAng1)-modified mesenchymal stem cells (MSCs) to treat acute myocardial infarction (AMI) in rats. The hAng1 gene was transfected into cultured rat MSCs using an adenoviral vector. Five million hAng-transfected MSCs (MSC(Ang1)) or green fluorescent protein transfected MSCs (MSC(GFP)) or PBS only (PBS group) were injected intramyocardially into the inbred Lewis rat hearts immediately after myocardial infarction. MSC(Ang1) survived in the infarcted myocardium, and expressed hAng1 at both mRNA and protein levels. The vascular density was higher in the MSC(Ang1) and MSC(GFP) groups than in the PBS group. The measurements of infarcted ventricular wall thickness, infarction area, and left ventricular diameter indicated that heart remodeling was inhibited and heart function was improved in both the MSC(Ang1) and MSC(GFP) groups. However, in contrast to the MSC(GFP) group, the MSC(Ang1) group showed enhanced angiogenesis and arteriogenesis (by 11-35%), infarction area was reduced by 30% and the left ventricular wall was 46% thicker (P<0.05). The results indicated that hAng1-modified MSCs improved heart function, followed by angiogenic effects in salvaging ischemic myocardium and reduced cardiac remodeling.

Response of micro- and macrovascular endothelial cells to starch-based fiber meshes for bone tissue engineering

The establishment of a functional vasculature is as yet an unrealized milestone in bone reconstruction therapy. For this study, fiber-mesh scaffolds obtained from a blend of starch and poly(caprolactone) (SPCL), that have previously been shown to be an excellent material for the proliferation and differentiation of bone marrow cells and thereby represent great potential as constructs for bone regeneration, were examined for endothelial cell (EC) compatibility. To be successfully applied in vivo, this tissue engineered construct should also be able to support the growth of ECs in order to facilitate vascularization and therefore assure the viability of the construct upon implantation. The main goal of this study was to examine the interactions between ECs and SPCL fiber meshes. Primary cultures of HUVEC cells were selected as a model of macrovascular cells and the cell line HPMEC-ST1.6R as a model for microvascular ECs. Both macro- and microvascular ECs adhered to SPCL fiber-mesh scaffolds and grew to cover much of the available surface area of the scaffold. In addition, ECs growing on the SPCL fibers exhibited a typical morphology, maintained important functional properties, such as the expression of the intercellular junction proteins, PECAM-1 and VE-cadherin, the expression of the most typical endothelial marker vWF and sensitivity to pro-inflammatory stimuli, as shown by induction of the expression of cell adhesion molecules (CAMs) by lipopolysaccharide (LPS). These data indicate that ECs growing on SPCL fiber-mesh scaffolds maintain a normal expression of EC-specific genes/proteins, indicating a cell compatibility and potential suitability of these scaffolds for the vascularization process in bone tissue engineering in vivo.

Angiogenic therapy for coronary artery and peripheral arterial disease

Neovascularization in chronically ischemic adult cardiac and skeletal muscle results from the processes of angiogenesis, arteriogenesis and vasculogenesis. Therapeutic angiogenesis describes an emerging field of cardiovascular medicine whereby new blood vessels are induced to grow to supply oxygen and nutrients to cardiac or skeletal muscle rendered ischemic as a result of progressive atherosclerosis. Various techniques have been utilized to promote new blood vessel growth in the heart and extremities, including mechanical means such as surgical or percutaneous myocardial laser revascularization, angiogenic growth factor therapies involving members of the vascular endothelial growth factor and fibroblast growth factor families, and more recently, cellular-based therapies using stem cells known as endothelial progenitor cells or angioblasts. The following review discusses each of these treatment strategies in detail including both preclinical and clinical data for their use in peripheral arterial and coronary artery disease.

Cell and Molecular Approaches to the Attenuation of Pain after Spinal Cord Injury

Recent experimental research to treat spinal cord injury (SCI) pain has greatly increased our understanding of how such chronic pain might be modulated in the human population. Neuropathic pain is caused by the structural and biochemical changes associated with the peripheral and central nervous system damage associated with nervous system trauma, often leading to an imbalance in endogenous excitatory and inhibitory spinal systems that modulate sensory processing. But current pharmacological therapies are often ineffective over time for the greater number of patients. Although there are a variety of useful surgical and pharmacologic interventions (including electric stimulation, implantable mechanical pumps and a myriad of drugs for pain relief) cell and molecular technologies are a new frontier in pain medicine. These other potential therapeutic agents of pain are based on current and developing treatment strategies elucidated from recent research, especially concerning central spinal sensitization, and the spinal mechanisms that are thought to be the origin and ongoing cause of chronic pain, even when the injury is peripheral in location. Newly developing translational strategies such as molecular agents, viral-mediated gene transfer or cellular transplants to treat chronic pain are being evaluated in a variety of peripheral and central injury models. They seek to address both the causes of neuropathic pain, to interfere with its development and maintenance over time, and give the injured person with pain an improved quality-of-life that allows them to better deal with the larger tasks of daily life and the strenuous rehabilitation that might also improve motor function after SCI.

Noninvasive imaging of transplanted living functional cells transfected with a reporter estrogen receptor gene

The transplantation of functional cells such as dopaminergic cells into damaged tissue is now clinically ongoing, but at present the population of surviving cells at the transplantation site mostly cannot be noninvasively examined. To visualize surviving transplanted functional cells using a noninvasive method, we chose the estrogen receptor ligand binding domain (ERL) as a reporter molecule and 16alpha-[18F]-fluoro-17beta-estradiol (FES) for its ligand. We used a mouse embryonic stem (ES) cell line for recipient cells as a model. To obtain ES cells that constitutively or inducibly express ERL, we transfected two types of expression vectors into EB5 parental ES cell line using the lipofection method and obtained about 30 clones for each of the two types of transfectants. Then, to examine the expression level of ERL, we performed Western blotting analysis. Ligand uptake experiments were carried out using [3H]-estradiol with or without excessive unlabeled estradiol for control cells and ERL transfectants. Each selected clone was also used for in vivo positron emission tomography (PET) imaging studies involving FES in nude mice transplanted with control cells and ERL transfectants. In some of the clones transfected with the inducible-type ERL gene, protein was expressed much higher than in the controls. However, constitutive-type ERL gene-transfected ES cells showed no protein production in spite of their gene expression activity being considerably high. All clones also expressed equal levels of the Oct-3/4 gene, a marker of pluripotency, in comparison with the parental cells. Also, the specific uptake of [3H]-estradiol was over 30 times higher in inducer-treated ERL-expressing ES cells compared to untreated control cells. Finally, by performing dynamic PET imaging, we successfully visualized ERL-expressing teratomas using FES.

Long-Term Culture of Human Urothelial Cells – A Qualitative Analysis

Today, in vitro culturing of autologous cells is an established method in the field of tissue reconstruction. It can be applied to urothelial cells and could have many clinical implications in urological reconstructive surgery. This development calls for quality controls concerning cells used for clinical treatment when cells are autotransplanted back to the patient. We have studied cultured cells in order to detect whether genetic or morphologic changes occur. Urothelial cells isolated from bladder lavage were cultured according to different protocols based on the presence or absence of feeder cells. Genetic studies were performed by means of karyotyping with standard G-banding and interphase fluorescent in situ hybridization (FISH) analyses. The morphology of these epithelial cells was judged as well as immunostaining for epithelial cell markers. In addition, to minimize the risk of feeder cell contamination, proliferation studies were performed on cultures including feeder cells that had been pretreated with different doses of mitomycin or radiation. In initial studies, when using feeder cells in each passage according to standard protocols, urothelial cells proliferated unfavourably after the fourth passage with increasing numbers of mouse cells as well as urothelial tetraploid cells. We could also show that urothelial cells from bladder lavage need feeder cells in order to establish primary cultures. Further propagation up to 14 passages was performed without feeder cells and the urothelial cells retained normal karyotypes. We also found that mitomycin treatment had its main effect on feeder cells during the first 2 h. When feeder cells were irradiated, 20 Gy was effective and no feeder cell contamination was seen. In conclusion, we found that a high standard of quality in urothelial cell culturing can be achieved with a careful culturing technique.

Review: application of stem cells for vascular tissue engineering

As the prevalence of vascular disease has continued to expand, the need for a suitable arterial replacement has prompted researchers to look beyond synthetic and autologous grafts toward the field of tissue engineering. Advances in vascular tissue engineering have utilized both mesenchymal and hematopoietic stem cells as a cell source in an attempt to create a fully engineered small-diameter graft. Stem cells offer enormous potential as a cell source because of their proliferative and growth potential, and the application of stem cell technology has far-reaching implications for future applications. The innovative use of stem cells for vascular tissue engineering has opened new possibilities for a fully engineered blood vessel. The purpose of this review is to summarize the current perspective on the use of stem cells for vascular tissue engineering. It focuses principally on the classes of stem cells used, techniques for differentiation scaffolding technology, and the successes and failures of models.

Tissue engineering of angiogenesis with autologous endothelial progenitor cells

Adult bone marrow and peripheral blood contain small subsets of mononuclear cells that can be differentiated into endothelial-like cells in vitro. Experimental and clinical transplantation of such cell isolates--often referred to as endothelial stem/progenitor cells--into ischaemic or infarcted areas shows their incorporation into sites of new vessel growth along with improvement of regional blood flow. Emerging evidence suggests that these beneficial effects on vascular growth can be attributed to the paracrine activation of resident endothelial cells, rather than their integration into new endothelium. Autologous endothelial progenitor cells can also substitute for native vessel-derived endothelial cells in tissue-engineered vascular autografts.

Combined cord blood stem cells and gene therapy enhances angiogenesis and improves cardiac performance in mouse after acute myocardial infarction

BACKGROUND

Gene and stem cell therapies hold promise for the treatment of ischaemic cardiovascular disease. However, combined stem cell and angiogenic growth factor gene therapy for acute ischaemic myocardium has not been previously reported. This study hypothesized that combined stem cell and gene therapy would not only augment new vessels formation but also improve myocardial function in acute ischaemic myocardium.

METHODS

Human angiopoietin-1 (Ang1) cDNA and VEGF(165) cDNA were ligated into AAV vector. The purified CD34(+) cells were obtained from human umbilical cord blood samples. Cord blood CD34(+) cells were transduced with AAV vector encoding either the human Ang1 (AAV-Ang1) or VEGF(165) (AAV-VEGF) cDNA alone, or both (AAV-Ang1 plus VEGF). Immediately after ligation of the left anterior descending coronary artery in male SCID mice, culture-expanded CD34(+) cells transduced with AAV-Ang1, AAV-VEGF or AAV-Ang1 plus VEGF were injected intramyocardially at the left anterior free wall.

RESULTS

Western blot showed that Ang1 and VEGF protein expressions were enhanced in the CD34(+)cells transduced with AAV-Ang1 and AAV-VEGF, respectively. Infarct size significantly decreased and capillary density significantly increased after treatment with CD34(+)/AAV-Ang1 plus VEGF when compared with treatment by CD34(+) only. Combined therapy with CD34(+) and AAV-Ang1, CD34(+) and AAV-VEGF, CD34(+) and AAV-Ang1 plus VEGF, all showed significantly higher cardiac performance in echocardiography than the therapy with CD34(+) alone 4 weeks after myocardial infarction.

CONCLUSIONS

Combined therapy with human umbilical cord blood CD34(+) cells and both Ang1 and VEGF genes reduced infarct size, attenuated the progression of cardiac dysfunction and increased capillary density in acute myocardial infarction in mice.

Stem cell-based composite tissue constructs for regenerative medicine

A major task of contemporary medicine and dentistry is restoration of human tissues and organs lost to diseases and trauma. A decade-long intense effort in tissue engineering has provided the proof of concept for cell-based replacement of a number of individual tissues such as the skin, cartilage, and bone. Recent work in stem cell-based in vivo restoration of multiple tissue phenotypes by composite tissue constructs such as osteochondral and fibro-osseous grafts has demonstrated probable clues for bioengineered replacement of complex anatomical structures consisting of multiple cell lineages such as the synovial joint condyle, tendon-bone complex, bone-ligament junction, and the periodontium. Of greater significance is a tangible contribution by current attempts to restore the structure and function of multitissue structures using cell-based composite tissue constructs to the understanding of ultimate biological restoration of complex organs such as the kidney or liver. The present review focuses on recent advances in stem cell-based composite tissue constructs and attempts to outline challenges for the manipulation of stem cells in tailored biomaterials in alignment with approaches potentially utilizable in regenerative medicine of human tissues and organs.

ACE2: A novel therapeutic target for cardiovascular diseases

Hypertension afflicts over 65 million Americans and poses an increased risk for cardiovascular morbidity such as stroke, myocardial infarction and end-stage renal disease resulting in significant mortality. Overactivity of the renin-angiotensin system (RAS) has been identified as an important determinant that is implicated in the etiology of these diseases and therefore represents a major target for therapy. In spite of the successes of drugs inhibiting various elements of the RAS, the incidence of hypertension and cardiovascular diseases remain steadily on the rise. This has lead many investigators to seek novel and innovative approaches, taking advantage of new pathways and technologies, for the control and possibly the cure of hypertension and related pathologies. The main objective of this review is to forward the concept that gene therapy and the genetic targeting of the RAS is the future avenue for the successful control and treatment of hypertension and cardiovascular diseases. We will present argument that genetic targeting of angiotensin-converting enzyme 2 (ACE2), a newly discovered member of the RAS, is ideally poised for this purpose. This will be accomplished by discussion of the following: (i) summary of our current understanding of the RAS with a focus on the systemic versus tissue counterparts as they relate to hypertension and other cardiovascular pathologies; (ii) the newly discovered ACE2 enzyme with its physiological and pathophysiological implications; (iii) summary of the current antihypertensive pharmacotherapy and its limitations; (iv) the discovery and design of ACE inhibitors; (v) the emerging concepts for ACE2 drug design; (vi) the current status of genetic targeting of the RAS; (vii) the potential of ACE2 as a therapeutic target for hypertension and cardiovascular disease treatment; and (viii) future perspectives for the treatment of cardiovascular diseases.

Characterization of mitochondrial and extra-mitochondrial oxygen consuming reactions in human hematopoietic stem cells. Novel evidence of the occurrence of NAD(P)H oxidase activity

This study was aimed to characterize the mitochondrial and extra-mitochondrial oxygen consuming reactions in human CD34+ hematopoietic stem cells. Cell samples were collected by apheresis following pre-conditioning by granulocyte colony-stimulating factor and isolated by anti-CD34 positive immunoselection. Polarographic analysis of the CN-sensitive endogenous cell respiration revealed a low mitochondrial oxygen consumption rate. Differential absorbance spectrometry on whole cell lysate and two-dimensional blue native-PAGE analysis of mitoplast proteins confirmed a low amount of mitochondrial respiratory chain complexes thus qualifying the hematopoietic stem cell as a poor oxidative phosphorylating cell type. Confocal microscopy imaging showed, however, that the intracellular content of mitochondria was not homogeneously distributed in the CD34+ hematopoietic stem cell sample displaying a clear inverse correlation of their density with the expression of the CD34 commitment marker. About half of the endogenous oxygen consumption was extra-mitochondrial and completely inhibitable by enzymatic scavengers of reactive oxygen species and by diphenylene iodinium. By spectral analysis, flow cytometry, reverse transcriptase-PCR, immunocytochemistry, and immunoprecipitation it was shown that the extra-mitochondrial oxygen consumption was contributed by the NOX2 and NOX4 isoforms of the O2-*. producer plasma membrane NAD(P)H oxidase with low constitutive activity. A model is proposed suggesting for the NAD(P)H oxidase a role of O2 sensor and/or ROS source serving as redox messengers in the activation of intracellular signaling pathways leading (or contributing) to mitochondriogenesis, cell survival, and differentiation in hematopoietic stem cells.

Cell therapy for neuropathic pain in spinal cord injuries

Cell therapy to treat neuropathic pain after spinal cord injury (SCI) is in its infancy. However, the development of cellular strategies that would replace or be used as an adjunct to existing pharmacological treatments for neuropathic pain have progressed tremendously over the past 20 years. The earliest cell therapy studies for pain relief tested adrenal chromaffin cells from rat or bovine sources, placed in the subarachnoid space, near the spinal cord pain- processing pathways. These grafts functioned as cellular minipumps, secreting a cocktail of antinociceptive agents around the spinal cord for peripheral nerve injury, inflammatory or arthritic pain. These initial animal, and later clinical, studies suggested that the spinal intrathecal space was a safe and accessible location for the placement of cell grafts. However, one major problem was the lack of a homogeneous, expandable cell source to supply the antinociceptive agents. Cell lines that can be reversibly immortalised are the next phase for the development of a practical, homogenous cell source. These technologies have been modelled with a variety of murine cell lines, derived from embryonic adrenal medulla or CNS brainstem, in which cells are transplanted, which downregulate their proliferative, oncogenic phenotype either before or after transplant. An alternative approach for existing human cell lines is the use of neural or adrenal precursors, in which the antinociceptive properties are induced by in vitro treatment with molecules that move the cells to an irreversible neural or chromaffin, and non-oncogenic, phenotype. Although such human cell lines are at an early stage of investigation, their clinical antinociceptive potential is significant given the daunting problem of difficult-to-treat neuropathic SCI pain.

Neural progenitor cell lines inhibit rat tumor growth in vivo

Current therapies for gliomas often fail to address their infiltrative nature. Conventional treatments leave behind small clusters of neoplastic cells, resulting in eventual tumor recurrence. In the present study, we have evaluated the antitumor activity of neural progenitor cells against gliomas when stereotactically injected into nucleus Caudatus of Fisher rats. We show that the rat neural progenitor cell lines HiB5 and ST14A, from embryonic hippocampus and striatum primordium, respectively, are able to prolong animal survival and, in 25% of the cases, completely inhibit the outgrowth of N29 glioma compared with control animals. Delayed tumor outgrowth was also seen when HiB5 cells were inoculated at the site of tumor growth 1 week after tumor inoculation or when a mixture of tumor cells and HiB5 cells were injected s.c. into Fisher rats. HiB5 cells were additionally coinoculated together with two alternative rat gliomas, N32 and N25. N32 was growth inhibited, but rats inoculated with N25 cells did not show a prolonged survival. To evaluate the possibility of the involvement of the immune system in the tumor outgrowth inhibition, we show that HiB5 cells do not evoke an immune response when injected into Fisher rats. Furthermore, the rat neural progenitor cells produce all transforming growth factor beta isotypes, which could explain the observed immunosuppressive nature of these cells. Hence, some neural progenitor cells have the ability to inhibit tumor outgrowth when implanted into rats. These results indicate the usefulness of neural stem cells as therapeutically effective cells for the treatment of intracranial tumors.