Stable gene expression by self-complementary adeno-associated viruses in human MSCs

Human umbilical cord mesenchymal stem cell-based gene therapy for hemophilia B using scAAV-DJ/8-LP1-hFIXco transduction

BACKGROUND

Hemophilia B is an X-linked bleeding disorder caused by a mutation in the gene responsible for encoding coagulation factor IX (FIX). Gene therapy offers promising potential for curing this disease. However, the current method of relatively high dosage of virus injection carries inherent risks. The purpose of this study was to introduce a novel scAAV-DJ/8-LP1-hFIXco vector transduced human umbilical cord blood derived mesenchymal stem cells (HUCMSCs) as an alternative cell-based gene therapy to conventional gene therapy for Hemophilia B.

METHODS

The LP1-hFIXco gene structure was designed by us through searching the literature from NCBI and the scAAV-DJ/8-LP1-hFIXco vector was constructed by a commercial company. The HUCMSCs were cultivated in routine approach and transduced with scAAV-DJ/8-LP1-hFIXco vector. The human FIX activation system was employed for detection of hFIXco activity. The RNA and protein expression levels of the hFIXco were evaluated using PCR and western blot techniques. In animal studies, both NSG and F9-KO mice were used for the experiment, in which clotting time was utilized as a parameter for bleeding assessment. The immunohistochemical analysis was used to assess the distribution of HUCMSCs in mouse tissue sections. The safety for tumorigenicity of this cell-based gene therapy was evaluated by pathological observation after hematoxylin-eosin staining.

RESULTS

The transduction of HUCMSCs with the scAAV-DJ/8-LP1-hFIXco vector results in consistent and sustainable secretion of human FIXco during 5 months period both in vitro and in mouse model. The secretion level (hFIXco activity: 97.1 ± 2.3% at day 7 to 48.8 ± 4.5% at 5 months) was comparable to that observed following intravenous injection with a high dose of the viral vector (hFIXco activity: 95.2 ± 2.2% to 40.8 ± 4.3%). After a 5-month observation period, no clonal expansions of the transduced cells in tissues were observed in any of the mice studied.

CONCLUSIONS

We have discovered a novel and safer HUCMSCs mediated approach potentially effective for gene therapy in hemophilia B.

PEO-PPO-PEO micelles as effective rAAV-mediated gene delivery systems to target human mesenchymal stem cells without altering their differentiation potency

Recombinant adeno-associated viral (rAAV) vectors are clinically adapted gene transfer vectors for direct human cartilage regenerative medicine. Their appropriate use in patients is still limited by a relatively low efficacy of vector penetration inside the cells, by the pre-existing humoral immune responses against the viral capsid proteins in a large part of the human population, and by possible inhibition of viral uptake by clinical compounds such as heparin. The delivery of rAAV vectors to their targets using optimized vehicles is therefore under active investigation. Here, we evaluated the possibility of providing rAAV to human bone marrow-derived mesenchymal stem cells (hMSCs), a potent source of cartilage regenerative cells, via self-assembled poly(ethylene oxide) (PEO) and poly(propylene oxide) (PPO) triblock copolymers as linear poloxamers or X-shaped poloxamines. Encapsulation in poloxamer PF68 and poloxamine T908 polymeric micelles allowed for an effective, durable, and safe modification of hMSCs via rAAV to levels similar to or even higher than those noted upon direct vector application. The copolymers were capable of restoring the transduction of hMSCs with rAAV in conditions of gene transfer inhibition, i.e. in the presence of heparin or of a specific antibody directed against the rAAV capsid, enabling effective therapeutic delivery of a chondrogenic sox9 sequence leading to an enhanced chondrocyte differentiation of the cells. The present findings highlight the value of PEO-PPO copolymers as powerful tools for rAAV-based cartilage regenerative medicine.

STATEMENT OF SIGNIFICANCE

While recombinant adeno-associated viral (rAAV) vectors are adapted vectors to treat a variety of human disorders, their clinical use is still restricted by pre-existing antiviral immune responses, by a low efficacy of natural vector entry in the target cells, and by inhibition of viral uptake by clinically used compounds like heparin. The search for alternative routes of rAAV delivery is thus becoming a new field of investigation. In the present study, we describe the strong benefits of providing rAAV to human mesenchymal stem cells, a potent source of cells for regenerative medicine, encapsulated in polymeric micelles based on poly(ethylene oxide) (PEO) and poly(propylene oxide) (PPO) triblock copolymers as novel, effective and safe delivery systems for human gene therapy.

Combined antitumor gene therapy with herpes simplex virus-thymidine kinase and short hairpin RNA specific for mammalian target of rapamycin

A proof-of-concept study is presented using dual gene therapy that employed a small hairpin RNA (shRNA) specific for mammalian target of rapamycin (mTOR) and a herpes simplex virus-thymidine kinase (HSV-TK) gene to inhibit the growth of tumors. Recombinant adeno-associated virus (rAAV) vectors containing a mutant TK gene (sc39TK) were transduced into HeLa cells, and the prodrug ganciclovir (GCV) was administered to establish a suicide gene-therapy strategy. Additionally, rAAV vectors expressing an mTOR-targeted shRNA were employed to suppress mTOR-dependent tumor growth. GCV selectively induced death in tumor cells expressing TK, and the mTOR-targeted shRNA altered the cell cycle to impair tumor growth. Combining the TK-GCV system with mTOR inhibition suppressed tumor growth to a greater extent than that achieved with either treatment alone. Furthermore, HSV-TK expression and mTOR inhibition did not mutually interfere with each other. In conclusion, gene therapy that combines the TK-GCV system and mTOR inhibition shows promise as a novel strategy for cancer therapy.

Upregulation of TrkB by forskolin facilitated survival of MSC and functional recovery of memory deficient model rats

Mesenchymal stem cells (MSCs) are effective vectors in delivering a gene of interest into degenerating brain. In ex vivo gene therapy, viability of transplanted MSCs is correlated with the extent of functional recovery. It has been reported that BDNF facilitates survival of MSCs but dividing MSCs do not express the BDNF receptor, TrkB. In this study, we found that the expression of TrkB is upregulated in human MSCs by the addition of forskolin (Fsk), an activator of adenylyl cyclase. To increase survival rate of MSCs and their secretion of tropic factors that enhance regeneration of endogenous cells, we pre-exposed hMSCs with Fsk and transduced with BDNF-adenovirus before transplantation into the brain of memory deficient rats, a degenerating brain disease model induced by ibotenic acid injection. Viability of MSCs and expression of a GABA synthesizing enzyme were increased. The pre-treatment improved learning and memory, as detected by the behavioral tests including Y-maze task and passive avoidance test. These results suggest that TrkB expression of hMSCs elevates the neuronal regeneration and efficiency of BDNF delivery for treating degenerative neurological diseases accompanying memory loss.

Self-complementary adeno-associated viral vectors for gene therapy of hemophilia B: progress and challenges

Therapies currently used for hemophilia involve injection of protein concentrates that are expensive, invasive and associated with side effects such as development of neutralizing antibodies (inhibitors) that diminish therapeutic efficacy. Gene transfer is an attractive alternative to circumvent these issues. However, until now, clinical trials using gene therapy to treat hemophilia have failed to demonstrate sustained efficacy, although a vector based on a self-complementary adeno-associated virus has recently shown promise. This article will briefly outline a novel gene-transfer approach using self-complementary adeno-associated viral vectors using hemophilia B as a target disorder. This approach is currently being evaluated in the clinic. We will provide an overview of the development of self-complementary adeno-associated virus vectors as well as preclinical and clinical data with this vector system.

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

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

Genetically manipulated adult stem cells for wound healing

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

Safe and effective gene transfer by adeno-associated virus of neonatal thymus-derived mesenchymal stromal cells

Recently, human neonatal thymus-derived mesenchymal stromal cells (nTMSCs) have been recognized as a promising mesenchymal stem cell source for combined cell and gene therapy. While efficient gene transfer is crucial for optimizing therapeutic efficacy, almost no studies have yet reported on the characteristics of nTMSC in terms of genetic modification. The present study investigates and realizes the potential of self-complementary adeno-associated viruses (scAAVs) as an effective transduction tool for nTMSCs. Transduction efficiency (TE), cytotoxicity and functional characteristics were determined in nTMSCs isolated from thymic tissues and transduced with scAAV1-6 and -8 serotypes expressing GFP. Our study confirms MSC-typical characteristics in nTMSCs and additionally, suggests further therapeutic advantages of nTMSCs due to its particularities with lower levels of MHC class I protein and higher levels of CD31 and CD34 expression. Effective transduction by scAAV2 and scAAV5 was evident in the majority of nTMSCs that were GFP-positive at a multiplicity of infection (MOI) of 1000. TE was further improved by higher MOI treatments. Transduced cells also successfully maintained adipocyte and vessel-forming endothelial cell multi-potency and showed no evidence of gene delivery-related cytotoxicity. Collectively, the data strongly suggest that scAAVs are promising technical platforms for safe and effective transgene expression in nTMSCs.

Synthetic scaffold coating with adeno-associated virus encoding BMP2 to promote endogenous bone repair

Biomaterial scaffolds functionalized to stimulate endogenous repair mechanisms via the incorporation of osteogenic cues offer a potential alternative to bone grafting for the treatment of large bone defects. We first quantified the ability of a self-complementary adeno-associated viral vector encoding bone morphogenetic protein 2 (scAAV2.5-BMP2) to enhance human stem cell osteogenic differentiation in vitro. In two-dimensional culture, scAAV2.5-BMP2-transduced human mesenchymal stem cells (hMSCs) displayed significant increases in BMP2 production and alkaline phosphatase activity compared with controls. hMSCs and human amniotic-fluid-derived stem cells (hAFS cells) seeded on scAAV2.5-BMP2-coated three-dimensional porous polymer Poly(ε-caprolactone) (PCL) scaffolds also displayed significant increases in BMP2 production compared with controls during 12 weeks of culture, although only hMSC-seeded scaffolds displayed significantly increased mineral formation. PCL scaffolds coated with scAAV2.5-BMP2 were implanted into critically sized immunocompromised rat femoral defects, both with or without pre-seeding of hMSCs, representing ex vivo and in vivo gene therapy treatments, respectively. After 12 weeks, defects treated with acellular scAAV2.5-BMP2-coated scaffolds displayed increased bony bridging and had significantly higher bone ingrowth and mechanical properties compared with controls, whereas defects treated with scAAV2.5-BMP2 scaffolds pre-seeded with hMSCs failed to display significant differences relative to controls. When pooled, defect treatment with scAAV2.5-BMP2-coated scaffolds, both with or without inclusion of pre-seeded hMSCs, led to significant increases in defect mineral formation at all time points and increased mechanical properties compared with controls. This study thus presents a novel acellular bone-graft-free endogenous repair therapy for orthotopic tissue-engineered bone regeneration.

Gene therapeutic approach for inhibiting hepatitis C virus replication using a recombinant protein that controls interferon expression

The hepatitis C virus (HCV) is a continuing threat to public health. The systemic administration of interferon alpha with ribavirin is the only currently approved treatment. However, this treatment is associated with a wide spectrum of systemic side effects that limits its effectiveness; thus, there is an urgent need for new treatment modalities. In this study, we describe a novel anti-HCV strategy employing a recombinant transcription factor that we have engineered in such a way that NS3/4a viral protease controls its intracellular localization, thereby restoring interferon secretion specifically in cells infected with HCV. Proof-of-concept experiments validated the strategy, showing that the recombinant transcription factor was triggered to stimulate interferon promoter by NS3/4A and remained inactive in cells without NS3/4a. Using an adenovirus-associated viral vector delivery system, we found that the recombinant transcription factor inhibited HCV replication effectively in vitro in cultured cells.

Effective relief of neuropathic pain by adeno-associated virus-mediated expression of a small hairpin RNA against GTP cyclohydrolase 1

Background

Recent studies show that transcriptional activation of GTP cyclohydrolase I (GCH1) in dorsal root ganglia (DRG) is significantly involved in the development and persistency of pain symptoms. We thus hypothesize that neuropathic pain may be attenuated by down-regulation of GCH1 expression, and propose a gene silencing system for this purpose.

Results

To interrupt GCH1 synthesis, we designed a bidirectional recombinant adeno-associated virus encoding both a small hairpin RNA against GCH1 and a GFP reporter gene (rAAV-shGCH1). After rAAV-shGCH1 was introduced into the sciatic nerve prior to or following pain-inducing surgery, therapeutic efficacy and the underlying mechanisms were subsequently validated in animal models. The GFP expression data indicates that rAAV effectively delivered transgenes to DRG. Subsequently reduced GCH1 expression was evident from immunohistochemistry and western-blotting analysis. Along with the down-regulation of GCH1, the von Frey test correspondingly indicated a sharp decline in pain symptoms upon both pre- and post-treatment with rAAV-shGCH1. Interestingly, GCH1 down-regulation additionally led to decreased microglial activation in the dorsal horn, implying an association between pain attenuation and reduced inflammation.

Conclusion

Therefore, the data suggests that GCH1 levels can be reduced by introducing rAAV-shGCH1, leading to pain relief. Based on the results, we propose that GCH1 modulation may be developed as a clinically applicable gene therapy strategy to treat neuropathic pain.

Viral vectors for stable transduction of human mesenchymal stem cells: systems based on adeno-associated viruses and lentiviruses

We compared the efficiency of transduction with lentivectors based on HIV-1 and adeno-associated viruses serotype 2 and stability of transgene expression in human mesenchymal bone marrow stem cells.

Effective transduction by self-complementary adeno-associated viruses of human dendritic cells with no alteration of their natural characteristics

BACKGROUND

Effective gene delivery techniques are required to genetically manipulate dendritic cells (DCs). We therefore investigated the feasibility of using various self-complementary recombinant adeno-associated virus (scAAV) serotypes to deliver genes to human DCs.

METHODS

Monocytes isolated from healthy volunteers were differentiated to immature DCs (iDC) by incubation with interleukin (IL)-4 and granulocyte macrophage colony-stimulating factor. The iDCs were transduced with scAAV1, 2, 3, 4, 5, 6 or 8 at various multiplicities of infection (MOIs). Transduction efficiency (TE), cell viability and functional characteristics of the transduced DCs were evaluated.

RESULTS

TE of scAAV was three-fold greater than TE of conventional recombinant adeno-associated virus with a single-stranded genome. The TEs of scAAV2, 5, and 6 were much higher than those of the other scAAVs; at 1000 MOI, the TEs were 22.2% +/- 9.5%, 27.0% +/- 8.8% and 28.4% +/- 6.0%, respectively. Exposure of iDCs to 5000 MOI of these viruses increased their TEs, leading to the transduction of nearly the entire DC population. In addition, gene transfer by scAAV did not cause any cytotoxicity. Flow cytometric analysis of scAAV-transduced DCs showed no changes in surface marker profiles. Moreover, transduced cells maintained their functional properties, as represented by active antigen uptake. These cells could efficiently differentiate into mature DCs, as shown by their release of IL-12, the substantial loss of antigen-uptake activity, and the ability of T-cell stimulation.

CONCLUSIONS

These findings strongly indicate that scAAVs, especially subtypes 2, 5 and 6, hold a promising potential as gene delivery tools in human DCs.