Role of the oxygen-dependent degradation domain in a hypoxia-inducible gene expression system in vascular endothelial growth factor gene therapy

BMSC-Exosomes Carry Mutant HIF-1α for Improving Angiogenesis and Osteogenesis in Critical-Sized Calvarial Defects

Repair and reconstruction of critical-sized bone defects has always been a difficult task in orthopedics. Hypoxia inducible factor-1α (HIF-1α) plays an important role in bone defect repair, it has the dual function of promoting osteogenesis and vascular regeneration, but it is quickly degraded by the body under normoxic conditions. Previously we prepared mutant HIF-1α, which has been shown to efficiently maintain cellular expression under normoxic conditions. In this study, we evaluated for the first time the role of exosomes of rat bone marrow mesenchymal stem cell carry mutant HIF-1α (BMSC-Exos-HIF1α) in repairing critical-sized bone defects. Evaluation of the effects of BMSC-Exos-HIF1α on bone marrow mesenchymal stem cells (BMSCs) proliferation and osteogenic differentiation by cell proliferation assay, alkaline phosphatase activity assay, alizarin red staining, real-time quantitative polymerase chain reaction. BMSC-Exos-HIF1α was loaded onto the β-TCP stent implanted in the bone defect area using a rat cranial critical-sized bone defect model, and new bone formation and neovascularization were detected in vivo by micro-CT, fluorescence labeling analysis, Microfil perfusion, histology and immunohistochemical analysis. In vitro results showed that BMSC-Exos-HIF1α stimulated the proliferation of BMSCs and up-regulated the expression level of bone-related genes, which was superior to bone marrow MSC exosomes (BMSC-Exos). In vivo results showed that BMSC-Exos-HIF1α combined with β-TCP scaffold promoted new bone regeneration and neovascularization in the bone defect area, and the effect was better than that of BMSC-Exos combined with β-TCP scaffold. In this study, the results showed that BMSC-Exos-HIF1α stimulated the proliferation and osteogenic differentiation of BMSCs and that BMSC-Exos-HIF1α combined with β-TCP scaffolds could repair critical-sized bone defects by promoting new bone regeneration and neovascularization.

The combination of forskolin and VPA increases gene expression efficiency to the hypoxia/neuron-specific system

Background

Spinal cord injury (SCI) tends to damage neural tissue and generate a hypoxic environment. Studies have confirmed that single therapy with gene or stem cells is inefficient, but research into combining stem cells and gene therapy in treating tissue damage has been undertaken to overcome the related limitations, which include low gene delivery efficiency and therapeutic outcome. Thus, a combination of stem cells, gene therapy, and a hypoxia-specific system may be useful for the reconstruction of SCI.

Methods

To synergistically treat SCI, a combined platform using a hypoxia/neuron-inducible gene expression system (HNIS) and human induced-neural stem cells (hiNSCs) produced by direct reprogramming was designed. Sox2- or nestin-positive hiNSCs were differentiated to Tuj1-, MAP2-, or NeuN-positive neurons.

Results

HNIS showed consistent hypoxia/neuron-specific gene expression in hiNSCs cultured under hypoxia. In particular, the HNIS-hiNSC combined platform revealed a complex pattern with higher gene expression compared with a single platform. In addition, we found that an optimal combination of small molecules, such as CHIR99021, valproic acid (VPA), glycogen synthase kinase-3β (GSK3β), and histone deacetylase (HDAC) inhibitors, could significantly enhance gene expression with HNIS-hiNSCs in the hypoxic environment.

Conclusions

This experiment demonstrated that HNIS-hiNSCs combined with GSK3 and HDAC inhibitors may present another promising strategy in the treatment of SCI.

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.

Electrophysiological, Morphological, and Ultrastructural Features of the Injured Spinal Cord Tissue after Transplantation of Human Umbilical Cord Blood Mononuclear Cells Genetically Modified with the VEGF and GDNF Genes

In this study, we examined the efficacy of human umbilical cord blood mononuclear cells (hUCB-MCs), genetically modified with the VEGF and GDNF genes using adenoviral vectors, on posttraumatic regeneration after transplantation into the site of spinal cord injury (SCI) in rats. Thirty days after SCI, followed by transplantation of nontransduced hUCB-MCs, we observed an improvement in H (latency period, LP) and M(A_max) waves, compared to the group without therapy after SCI. For genetically modified hUCB-MCs, there was improvement in A_max of M wave and LP of both the M and H waves. The ratio between A_max of the H and M waves (H_max/M_max) demonstrated that transplantation into the area of SCI of genetically modified hUCB-MCs was more effective than nontransduced hUCB-MCs. Spared tissue and myelinated fibers were increased at day 30 after SCI and transplantation of hUCB-MCs in the lateral and ventral funiculi 2.5 mm from the lesion epicenter. Transplantation of hUCB-MCs genetically modified with the VEGF and GNDF genes significantly increased the number of spared myelinated fibers (22-fold, P > 0.01) in the main corticospinal tract compared to the nontransduced ones. HNA⁺ cells with the morphology of phagocytes and microglia-like cells were found as compact clusters or cell bridges within the traumatic cavities that were lined by GFAP⁺ host astrocytes. Our results show that hUCB-MCs transplanted into the site of SCI improved regeneration and that hUCB-MCs genetically modified with the VEGF and GNDF genes were more effective than nontransduced hUCB-MCs.

Assessment of Glial Scar, Tissue Sparing, Behavioral Recovery and Axonal Regeneration following Acute Transplantation of Genetically Modified Human Umbilical Cord Blood Cells in a Rat Model of Spinal Cord Contusion

OBJECTIVE AND METHODS

This study investigated the potential for protective effects of human umbilical cord blood mononuclear cells (UCB-MCs) genetically modified with the VEGF and GNDF genes on contusion spinal cord injury (SCI) in rats. An adenoviral vector was constructed for targeted delivery of VEGF and GDNF to UCB-MCs. Using a rat contusion SCI model we examined the efficacy of the construct on tissue sparing, glial scar severity, the extent of axonal regeneration, recovery of motor function, and analyzed the expression of the recombinant genes VEGF and GNDF in vitro and in vivo.

RESULTS

Transplantation of UCB-MCs transduced with adenoviral vectors expressing VEGF and GDNF at the site of SCI induced tissue sparing, behavioral recovery and axonal regeneration comparing to the other constructs tested. The adenovirus encoding VEGF and GDNF for transduction of UCB-MCs was shown to be an effective and stable vehicle for these cells in vivo following the transplantation into the contused spinal cord.

CONCLUSION

Our results show that a gene delivery using UCB-MCs-expressing VEGF and GNDF genes improved both structural and functional parameters after SCI. Further histological and behavioral studies, especially at later time points, in animals with SCI after transplantation of genetically modified UCB-MCs (overexpressing VEGF and GDNF genes) will provide additional insight into therapeutic potential of such cells.

Antiapoptotic Effect of Highly Secreted GMCSF From Neuronal Cell-specific GMCSF Overexpressing Neural Stem Cells in Spinal Cord Injury Model

STUDY DESIGN

Neuronal cell-specific gene expression system and neural stem cells (NSCs) were combined for treatment of spinal cord injury (SCI).

OBJECTIVE

To verify the reproducibility of the neuronal cell-specific therapeutic gene overexpression system, we develop a neuronal cell-specific granulocyte-macrophage colony-stimulating factor expression system (NSE-GMCSF), and then examine the characteristics of GMCSF overexpression and protective effect on neural cells in vitro and vivo.

SUMMARY OF BACKGROUND DATA

The stem cell transplantation is considered a promising therapy for SCI. However, stem cell monotherapy strategy is insufficient for complete recovery after SCI. Therefore, combined treatment method based on stem cells with other therapeutic system may be effective for improving the therapeutic efficacy. In this study, we established the gene and stem cell therapy platform based on NSCs and neuronal cell-specific gene expression system.

METHODS

To examine the GMCSF expression pattern, we compared the amount of secreted GMCSF from the neuronal cell-specific GMCSF expressing NSCs with control GMCSF-expressing NSCs (respectively, NSE-GMCSF-NSCs vs. SV-GMCSF-NSCs) by ELISA in vitro and in vivo, and then verified the neuronal protective effect of these cells in vitro and vivo.

RESULTS

The results showed that NSE-GMCSF-NSCs secreted more GMCSF compared with SV-GMCSF-NSCs in normoxia, hypoxia and cytotoxic conditions. The cell viability of NSE-GMCSF-NSCs was increased depending on the amount of secreted GMCSF in cytotoxic condition. In addition, the amount of secreted GMCSF by NSE-GMCSF-NSCs transplanted into injured spinal cord was significantly higher than SV-GMCSF-NSCs. Higher amount of secreted GMCSF decreased the expression of proapoptotic protein, Bax.

CONCLUSION

In this study, we demonstrated that the neuronal cell-specific gene expression system induced overexpression of GMCSF in NSCs. These combined NSCs & gene therapy treatment protocol would be an effective therapeutic system for SCI.

LEVEL OF EVIDENCE

N/A.

A Gene and Neural Stem Cell Therapy Platform Based on Neuronal Cell Type-Inducible Gene Overexpression

PURPOSE

Spinal cord injury (SCI) is associated with permanent neurological damage, and treatment thereof with a single modality often does not provide sufficient therapeutic outcomes. Therefore, a strategy that combines two or more techniques might show better therapeutic effects.

MATERIALS AND METHODS

In this study, we designed a combined treatment strategy based on neural stem cells (NSCs) introduced via a neuronal cell type-inducible transgene expression system (NSE::) controlled by a neuron-specific enolase (NSE) promoter to maximize therapeutic efficiency and neuronal differentiation. The luciferase gene was chosen to confirm whether this combined system was working properly prior to using a therapeutic gene. The luciferase expression levels of NSCs introduced via the neuronal cell type-inducible luciferase expression system (NSE::Luci) or via a general luciferase expressing system (SV::Luci) were measured and compared in vitro and in vivo.

RESULTS

NSCs introduced via the neuronal cell type-inducible luciferase expressing system (NSE::Luci-NSCs) showed a high level of luciferase expression, compared to NSCs introduced via a general luciferase expressing system (SV::Luci-NSCs). Interestingly, the luciferase expression level of NSE::Luci-NSCs increased greatly after differentiation into neurons.

CONCLUSION

We demonstrated that a neuronal cell type-inducible gene expression system is suitable for introducing NSCs in combined treatment strategies. We suggest that the proposed strategy may be a promising tool for the treatment of neurodegenerative disorders, including SCI.

Functional polymers of gene delivery for treatment of myocardial infarct

Ischemic heart disease is rapidly growing as the common cause of death in the world. It is a disease that occurs as a result of coronary artery stenosis and is caused by the lack of oxygen within cardiac muscles due to an imbalance between oxygen supply and demand. The conventional medical therapy is focused on the use of drug eluting stents, coronary-artery bypass graft surgery and anti-thrombosis. Gene therapy provides great opportunities for treatment of cardiovascular disease. In order for gene therapy to be successful, the development of proper gene delivery systems and hypoxia-regulated gene expression vectors is the most important factors. Several non-viral gene transfer methods have been developed to overcome the safety problems of viral transduction. Some of which include plasmids that regulate gene expression that is controlled by environment specific promoters in the transcriptional or the translational level. This review explores polymeric gene carriers that target the myocardium and hypoxia-inducible vectors, which regulate gene expression in response to hypoxia, and their application in animal myocardial infarction models.

Post-translational regulated and hypoxia-responsible VEGF plasmid for efficient secretion

Gene therapy using angiogenic genes has emerged as a potentially viable alternative treatment strategy for myocardial ischemia. Non-specific expression of angiogenic genes, however, may result in side effects, including the growth of occult tumors. Regulation of gene expression may help to avoid the occurrence of these side effects. In this study, a plasmid expressing vascular endothelial growth factor (VEGF) was constructed with an oxygen dependent degradation (ODD) domain and a secretion signal peptide (SP) in order to stabilize the VEGF protein and facilitate the secretion of VEGF protein, specifically under hypoxic conditions. We found that this plasmid, pβ-SP-ODD-VEGF, expresses the SP-ODD-VEGF protein at increased levels under hypoxic conditions compared to normoxic conditions. Since the size of the ODD domain is almost the same as that of VEGF, the ODD-VEGF fusion protein may have lower secretion efficiency. To address this issue, a furin recognition site was located between the ODD domain and the VEGF site to facilitate elimination of the SP-ODD domain from the fusion protein before its secretion. This optimizes the likelihood that the VEGF secreted from the target cells will be wild-type VEGF. Treatment with a furin inhibitor reduced the secretion efficiency of the VEGF, indicating that furin digestion increases the secretion of VEGF. The secreted wild-type VEGF facilitated the growth of endothelial cells more efficiently under hypoxic conditions than normoxic conditions. These results suggest that this plasmid, pβ-SP-ODD-VEGF, warrants further study as a more efficient form of hypoxia-inducible gene therapy for the treatment of myocardial ischemia.

Long space missions, gene therapy, and the vital role of magnesium: a three-pronged plan for the next 50 years

Since pharmaceuticals cannot be used in space until liver and kidney dysfunctions are corrected, and with invariable malabsorption, it appears there is no alternative other than to use subcutaneous magnesium (Mg) replacements in the presence of deficiencies and use of gene therapy. I suggest beginning with the correction of as many as four gene deficiencies: atrial natriuretic peptide (ANP), nitric oxide (NO), vascular endothelial growth factor (VEGF), and erythropoietin (EPO), all as well as Mg related to perfusion and angiogenesis. There is no evidence of significant lunar radiation levels in the absence of a solar storm. It could then be determined whether this has resulted in correction of liver and kidney dysfunction. If this persists, serial additions of gene therapy will be required determining the effect of each individual gene trial on organ function. Microgravity and endothelial gaps with leaks trigger reduced plasma volume. Partial correction by use of a plasma volume substitute and development of a delivery device may reduce complexity of gene therapy. Research would be conducted both on Earth and in microgravity, with the development of subcutaneous pharmaceuticals and Mg, and a space walk-reliable subcutaneous silicon device, given that no replenishable subcutaneous device is presently available. A three-pronged approach provides a plan for the next 50 years: A. complete correction of a Mg deficit; B. partial replacement with plasma volume substitutes, and C. multiple gene factor strategy.