Efficient and ligand-dependent regulated erythropoietin production by naked dna injection and in vivo electroporation

In situ transient transfection of 3D cell cultures and tissues, a promising tool for tissue engineering and gene therapy

Various research fields use the transfection of mammalian cells with genetic material to induce the expression of a target transgene or gene silencing. It is a tool widely used in biological research, bioproduction, and therapy. Current transfection protocols are usually performed on 2D adherent cells or suspension cultures. The important rise of new gene therapies and regenerative medicine in the last decade raises the need for new tools to empower the in situ transfection of tissues and 3D cell cultures. This review will present novel in situ transfection methods based on a chemical or physical non-viral transfection of cells in tissues and 3D cultures, discuss the advantages and remaining gaps, and propose future developments and applications.

Construction of porcine growth hormone eukaryotic expression vector and its transfection mediated by cationic liposome in mice

The present study was designed to construct the eukaryotic expression vector for pGH mature peptide (mpGH) and to investigate its transfection mediated by cationic liposome (CLs) in COS-7 cells and mice. The cDNA of mpGH ORF was successfully cloned by reverse transcription-PCR (RT-PCR) using the adult pig pituitary gland RNA. The recombinant eukaryotic expression vector, VmpGH, was constructed by ligating the cDNA fragment to the vector VR1020. The successful construction was confirmed by restriction enzyme digestion, and the expression of mpGH was confirmed by RT-PCR, immunofluorescence analyses (IFA), and ELISA in COS-7 cells. The VmpGH and VR1020 plasmids were entrapped with CLs, and four experimental groups of male Kunming mice were administrated with VmpGH / lipoplex or naked VmpGH plasmids at two dosages (0.5 and 1.0 mg/kg), while the mice injected with VR1020-lipoplex at the dosage of 0.5 mg/kg body weight (BW) were used as control. The BWs of the mice administrated with VmpGH-lipoplex at both dosages were significantly higher than not only those of the control (P < 0.01) but also those of mice injected with naked plasmids (P < 0.01), from 30 to 60 days post-transfection. The transcription of VmpGH was detected by RT-PCR in six tissues, including the liver, kidney, spleen, heart, muscle, and blood, of the mice injected with VmpGH-lipoplex, but not in the same tissues of control mice. Furthermore, the mice injected with VmpGH-lipoplex showed higher plasma GH contents than the control mice (P < 0.05), although their IgG contents did not show much difference. Our study demonstrates that the VmpGH plasmids' transfection mediated by CLs can significantly promote the growth of mice, which may be used to improve the livestock production.

Numerical optimization of gene electrotransfer into muscle tissue

BACKGROUND

Electroporation-based gene therapy and DNA vaccination are promising medical applications that depend on transfer of pDNA into target tissues with use of electric pulses. Gene electrotransfer efficiency depends on electrode configuration and electric pulse parameters, which determine the electric field distribution. Numerical modeling represents a fast and convenient method for optimization of gene electrotransfer parameters. We used numerical modeling, parameterization and numerical optimization to determine the optimum parameters for gene electrotransfer in muscle tissue.

METHODS

We built a 3D geometry of muscle tissue with two or six needle electrodes (two rows of three needle electrodes) inserted. We performed a parametric study and optimization based on a genetic algorithm to analyze the effects of distances between the electrodes, depth of insertion, orientation of electrodes with respect to muscle fibers and applied voltage on the electric field distribution. The quality of solutions were evaluated in terms of volumes of reversibly (desired) and irreversibly (undesired) electroporated muscle tissue and total electric current through the tissue.

RESULTS

Large volumes of reversibly electroporated muscle with relatively little damage can be achieved by using large distances between electrodes and large electrode insertion depths. Orienting the electrodes perpendicular to muscle fibers is significantly better than the parallel orientation for six needle electrodes, while for two electrodes the effect of orientation is not so pronounced. For each set of geometrical parameters, the window of optimal voltages is quite narrow, with lower voltages resulting in low volumes of reversibly electroporated tissue and higher voltages in high volumes of irreversibly electroporated tissue. Furthermore, we determined which applied voltages are needed to achieve the optimal field distribution for different distances between electrodes.

CONCLUSION

The presented numerical study of gene electrotransfer is the first that demonstrates optimization of parameters for gene electrotransfer on tissue level. Our method of modeling and optimization is generic and can be applied to different electrode configurations, pulsing protocols and different tissues. Such numerical models, together with knowledge of tissue properties can provide useful guidelines for researchers and physicians in selecting optimal parameters for in vivo gene electrotransfer, thus reducing the number of animals used in studies of gene therapy and DNA vaccination.

Erythropoietin over-expression protects against diet-induced obesity in mice through increased fat oxidation in muscles

Erythropoietin can be over-expressed in skeletal muscles by gene electrotransfer, resulting in 100-fold increase in serum EPO and significant increases in haemoglobin levels. Earlier studies have suggested that EPO improves several metabolic parameters when administered to chronically ill kidney patients. Thus we applied the EPO over-expression model to investigate the metabolic effect of EPO in vivo.

At 12 weeks, EPO expression resulted in a 23% weight reduction (P<0.01) in EPO transfected obese mice; thus the mice weighed 21.9±0.8 g (control, normal diet,) 21.9±1.4 g (EPO, normal diet), 35.3±3.3 g (control, high-fat diet) and 28.8±2.6 g (EPO, high-fat diet). Correspondingly, DXA scanning revealed that this was due to a 28% reduction in adipose tissue mass.

The decrease in adipose tissue mass was accompanied by a complete normalisation of fasting insulin levels and glucose tolerance in the high-fat fed mice. EPO expression also induced a 14% increase in muscle volume and a 25% increase in vascularisation of the EPO transfected muscle. Muscle force and stamina were not affected by EPO expression. PCR array analysis revealed that genes involved in lipid metabolism, thermogenesis and inflammation were increased in muscles in response to EPO expression, while genes involved in glucose metabolism were down-regulated. In addition, muscular fat oxidation was increased 1.8-fold in both the EPO transfected and contralateral muscles.

In conclusion, we have shown that EPO when expressed in supra-physiological levels has substantial metabolic effects including protection against diet-induced obesity and normalisation of glucose sensitivity associated with a shift to increased fat metabolism in the muscles.

Electroporation-mediated gene therapy

Non-viral gene transfer is markedly enhanced by the application of in vivo electroporation. Electroporation is a safe and efficient system to introduce genes to a wide variety of tissues, including skeletal muscle, tumors, kidney, liver and skin. Electroporation has been demonstrated to be effective in numerous disease models. This review focuses on the principles of electroporation and the target tissues employed for gene therapy. Based on the accumulation of positive results, the first clinical study for the treatment of malignant melanoma is now underway, and preclinical studies have suggested that electroporation is useful as a gene therapy protocol.

Gene expression profiles in skeletal muscle after gene electrotransfer

BACKGROUND

Gene transfer by electroporation (DNA electrotransfer) to muscle results in high level long term transgenic expression, showing great promise for treatment of e.g. protein deficiency syndromes. However little is known about the effects of DNA electrotransfer on muscle fibres. We have therefore investigated transcriptional changes through gene expression profile analyses, morphological changes by histological analysis, and physiological changes by force generation measurements. DNA electrotransfer was obtained using a combination of a short high voltage pulse (HV, 1000 V/cm, 100 mus) followed by a long low voltage pulse (LV, 100 V/cm, 400 ms); a pulse combination optimised for efficient and safe gene transfer. Muscles were transfected with green fluorescent protein (GFP) and excised at 4 hours, 48 hours or 3 weeks after treatment.

RESULTS

Differentially expressed genes were investigated by microarray analysis, and descriptive statistics were performed to evaluate the effects of 1) electroporation, 2) DNA injection, and 3) time after treatment. The biological significance of the results was assessed by gene annotation and supervised cluster analysis.Generally, electroporation caused down-regulation of structural proteins e.g. sarcospan and catalytic enzymes. Injection of DNA induced down-regulation of intracellular transport proteins e.g. sentrin. The effects on muscle fibres were transient as the expression profiles 3 weeks after treatment were closely related with the control muscles. Most interestingly, no changes in the expression of proteins involved in inflammatory responses or muscle regeneration was detected, indicating limited muscle damage and regeneration. Histological analysis revealed structural changes with loss of cell integrity and striation pattern in some fibres after DNA+HV+LV treatment, while HV+LV pulses alone showed preservation of cell integrity. No difference in the force generation capacity was observed in the muscles 2 weeks after DNA electrotransfer.

CONCLUSION

The small and transient changes found in the gene expression profiles are of great importance, as this demonstrates that DNA electrotransfer is safe with minor effects on the muscle host cells. These findings are essential for introducing the DNA electrotransfer to muscle for clinical use. Indeed the HV+LV pulse combination used has been optimised to ensure highly efficient and safe DNA electrotransfer.

Sensitive and precise regulation of haemoglobin after gene transfer of erythropoietin to muscle tissue using electroporation

Electroporation-based gene transfer (electro gene transfer (EGT)) is gaining increasing momentum, in particular for muscle tissue, where long-term high-level expression is obtainable. Induction of expression using the Tet-On system was previously established; however, attempts to reach a predefined target dose - a prescription, have not been reported. We set three target haemoglobin levels (10, 12 and 14 mmol/l, base level was 8.2 mmol/l) and aimed at them by transferring the erythropoietin (EPO) gene to mouse tibialis cranialis (TC) muscle, and varying (1) DNA amount, (2) muscle mass transfected and (3) induction with the Tet-On system. Results showed that (a) using GFP, luciferase and EPO low DNA amounts were needed. In fact, 0.5 microg of DNA to one TC muscle led to significant Hgb elevation - this amount extrapolates to 1.4 mg of DNA in humans, (b) three prescribers hit the targets with average Hgb of 10.5, 12.0 and 13.7 mmol/l, (c) different approaches could be used, (d) undershooting could be corrected by retransferring, and (e) overshooting could be alleviated by reducing dose of inducer (doxycycline (dox)). In conclusion, this study shows that using EGT to muscle, a preset level of protein expression can be reached. This is of great interest for future clinical use.

Highly Efficient Constant-Current Electroporation IncreasesIn VivoPlasmid Expression

Electroporation has been demonstrated as an effective technique for enhancing the delivery of plasmids coding for DNA vaccines and therapeutic proteins into skeletal muscle. Nevertheless, constant-voltage techniques do not take into account the resistance of the tissue and result in tissue damage, inflammation, and loss of plasmid expression. In the present study, we have used a software-driven constant-current electroporator to deliver plasmids to mice and small and large pigs. The voltage, amperage, and resistance of the tissue during pulses were recorded and analyzed. Optimal conditions of electroporation were identified in both species, and found to be highly dependent on the individual tissue resistance. Six- to 10-week-old pigs had higher muscle resistance compared to 1- to 2-year-old pigs, but both values were four to five times lower than the resistance of the mouse muscle. In mice, optimum amperage, pulse length, and lag time between plasmid injection and electroporation were identified to be 0.1 Amps, 20 msec and 0 sec. The electroporation pulse pattern among the electrodes also affected plasmid expression. These results indicate that age- and tissue-specific resistance, pulse pattern, and other variables associated with the electroporation need to be optimized for each separate species to achieve maximum plasmid expression.

Electric pulse-mediated gene delivery to various animal tissues

Electroporation designates the use of electric pulses to transiently permeabilize the cell membrane. It has been shown that DNA can be transferred to cells through a combined effect of electric pulses causing (1) permeabilization of the cell membrane and (2) an electrophoretic effect on DNA, leading the polyanionic molecule to move toward or across the destabilized membrane. This process is now referred to as DNA electrotransfer or electro gene transfer (EGT). Several studies have shown that EGT can be highly efficient, with low variability both in vitro and in vivo. Furthermore, the area transfected is restricted by the placement of the electrodes, and is thus highly controllable. This has led to an increasing use of the technology to transfer reporter or therapeutic genes to various tissues, as evidenced from the large amount of data accumulated on this new approach for non-viral gene therapy, termed electrogenetherapy (EGT as well). By transfecting cells with a long lifetime, such as muscle fibers, a very long-term expression of genes can be obtained. A great variety of tissues have been transfected successfully, from muscle as the most extensively used, to both soft (e.g., spleen) and hard tissue (e.g., cartilage). It has been shown that therapeutic levels of systemically circulating proteins can be obtained, opening possibilities for using EGT therapeutically. This chapter describes the various aspects of in vivo gene delivery by means of electric pulses, from important issues in methodology to updated results concerning the electrotransfer of reporter and therapeutic genes to different tissues.

DNA electrotransfer: its principles and an updated review of its therapeutic applications

The use of electric pulses to transfect all types of cells is well known and regularly used in vitro for bacteria and eukaryotic cells transformation. Electric pulses can also be delivered in vivo either transcutaneously or with electrodes in direct contact with the tissues. After injection of naked DNA in a tissue, appropriate local electric pulses can result in a very high expression of the transferred genes. This manuscript describes the evolution in the concepts and the various optimization steps that have led to the use of combinations of pulses that fit with the known roles of the electric pulses in DNA electrotransfer, namely cell electropermeabilization and DNA electrophoresis. A summary of the main applications published until now is also reported, restricted to the in vivo preclinical trials using therapeutic genes.

Laparoscopic Assisted Colectomies in Kidney Transplant Recipients with Colon Cancer

BACKGROUND

Kidney transplant recipients have increased operative risks for major abdominal surgery. The purpose of this study is to present the results of laparoscopic assisted colectomies (LAC) in patients who have received a kidney transplant, and evaluate the difficulty and potential benefits or hazards inherent in this approach.

PATIENTS AND METHODS

From September 1993 to March 2003, 820 patients underwent LAC in our service. We studied all patients with kidney transplant and LAC.

RESULTS

Three kidney transplantation recipients were included. Two patients were female and one male. The mean age was 65 years (range, 54-73 years). The average time elapsed since transplantation was 8 years (range, 6-10 years), and no patient had experienced problems with rejection. All patients had colon cancer. All of the allografts were contralateral to the side of the colon resection. The mean operative time was 103 minutes (range, 100-105 minutes). There were no complications, renal function remained intact, and there was no need to stop immunosuppression. The average length of hospital stay was 5 days (range, 4-7 days). The mean followup time has been 17 months (range, 3-40 months). Since surgery there have been no episodes of rejection and the patients have been free of cancer.

CONCLUSION

The benefits of minimal access surgery seem to be shared by kidney transplant recipients. A key feature may be to avoid stopping immunosuppression perioperatively, therefore lowering the potential risk of rejection. Also, lessening the number of wound-related problems appears important for these patients. LAC in experienced hands must be considered a safe alternative for elective colon resections in highly selected patients with kidney transplants.

Effects of plasmid-mediated growth hormone releasing hormone supplementation in young, healthy Beagle dogs

Our study focused on the evaluation of the pharmacological and toxicological effects of plasmid-mediated GHRH supplementation with electroporation in normal adult dogs over a 180-d period. Twenty-eight dogs (< 2 yr of age) were randomized to four groups. Three groups (four dogs/sex for each group) were treated with ascending doses of GHRH-expressing plasmid: 0.2, 0.6, and 1 mg. One group (two dogs of each sex) served as the control. Clinical observations and body weights were recorded. Hematological, serum biochemical, and urine analyses were performed. Serum IGF-I, ACTH, and insulin were determined. Necropsies were performed on d 93 and 180; organs were weighed and tissues were fixed and processed for light microscopy. Selected tissues were used to assess plasmid biodistribution on d 93. At all doses, plasmid GHRH caused increased weight gain (P < 0.001), without organomegaly. Serum glucose and insulin in fasted dogs remained within normal ranges at all time points. Adrenocorticotropic hormone was normal in all groups. Significant increases in number of red blood cells, hematocrit, and hemoglobin (P < 0.01) were observed. In conclusion, our study shows that plasmid-mediated GHRH supplementation is safe in electroporated doses up to 1.0 mg in young healthy dogs.

High-efficiency growth hormone-releasing hormone plasmid vector administration into skeletal muscle mediated by electroporation in pigs

We report here a very efficient method for the in vivo transfer of therapeutic plasmid DNA into porcine muscle fibers by using electric pulses of low field intensity. We evaluated delivery of 0.1-3 mg of plasmid vectors that encode reporter secreted-embryonic alkaline phosphatase (SEAP) or therapeutic growth hormone releasing hormone (GHRH). Reporter gene studies showed that internal needle electrodes give a 25-fold increase in expression levels compared with caliper electrodes in skeletal muscle in swine. Dose and time courses were performed. Pigs injected with 0.1 mg plasmid had significantly greater weight gain than controls over 53 days (22.4 +/- 0.8 kg vs. 19.7 +/- 0.03 kg, respectively; P<0.01). The group treated with GHRH-expressing plasmid at 14 days of age demonstrated greater weight gain than controls at every time point (25.8 +/- 1.5 kg vs. 19.7 +/- 0.03 kg; P<0.01). Body composition studies by dual X-ray absorbitometry showed a 22% decrease in fat deposition (P<0.05) and a 10% increase in bone mineral density (P<0.004). Our studies demonstrate that by optimizing the electroporation method, favorable physiological changes, such as enhanced weight gain and improved body composition, can be obtained at extremely low plasmid doses in a large mammal.

Progress and prospects: naked DNA gene transfer and therapy

Increases in efficiency have made naked DNA gene transfer a viable method for gene therapy. Intravascular delivery results in effective gene delivery to liver and muscle, and provides in vivo transfection methods for basic and applied gene therapy and antisense strategies with oligonucleotides and small interfering RNA (siRNA). Delivery via the tail vein in rodents provides an especially simple and effective means for in vivo gene transfer. Electroporation methods significantly enhance direct injection of naked DNA for genetic immunization. The availability of plasmid DNA expression vectors that enable sustained high level expression, allows for the development of gene therapies based on the delivery of naked plasmid DNA.

Electrical enhancement of formulated plasmid delivery in animals

Electroporation has been shown to significantly increase plasmid transfer to the skeletal muscle, but this procedure is also implicated in muscle damage. We are reporting a highly efficient in vivo transfer of a plasmid formulated with poly-(L-glutamate) (PLG) into murine, canine and porcine muscle fibers using electric pulses of low field intensity. In mice and pigs, the use of secreted embryonic alkaline phosphatase (SEAP) as the indicator gene caused increased PLG expression by 2-3 fold compared to naked plasmid; while delivery of a PLG-plasmid formulation to dogs showed a 10-fold increase in serum SEAP levels compared to plasmid alone. Muscle lesions were reduced by the protective PLG. Thus, PLG may constitute a useful adjuvant for increased expression and reduced muscle trauma to plasmid DNA delivered by electroporation.