Delivery of a secretable adenosine deaminase through microcapsules--a novel approach to somatic gene therapy

Adenosine-associated delivery systems

Adenosine is a naturally occurring purine nucleoside in every cell. Many critical treatments such as modulating irregular heartbeat (arrhythmias), regulation of central nervous system (CNS) activity and inhibiting seizural episodes can be carried out using adenosine. Despite the significant potential therapeutic impact of adenosine and its derivatives, the severe side effects caused by their systemic administration have significantly limited their clinical use. In addition, due to adenosine's extremely short half-life in human blood (<10 s), there is an unmet need for sustained delivery systems to enhance efficacy and reduce side effects. In this article, various adenosine delivery techniques, including encapsulation into biodegradable polymers, cell-based delivery, implantable biomaterials and mechanical-based delivery systems, are critically reviewed and the existing challenges are highlighted.

Reduction of GAG storage in MPS II mouse model following implantation of encapsulated recombinant myoblasts

BACKGROUND

Hunter syndrome, mucopolysaccharidosis type II (MPS II), is a X-linked inherited disorder caused by the deficiency of the enzyme iduronate-2-sulfatase (IDS), involved in the lysosomal catabolism of the glycosaminoglycans (GAG) dermatan and heparan sulfate. Such a deficiency leads to the intracellular accumulation of undegraded GAG and eventually to a progressive severe clinical pattern. Many attempts have been made in the last two to three decades to identify possible therapeutic strategies for the disorder, including gene therapy and somatic cell therapy.

METHODS

In this study we evaluated the intraperitoneal implantation of allogeneic myoblasts over-expressing IDS, enclosed in alginate microcapsules, in the MPS II mouse model. Animals were monitored for 8 weeks post-implantation, during which plasma and tissue IDS levels, as well as tissue and urinary GAG contents, were measured.

RESULTS AND CONCLUSIONS

Induced enzyme activity occurred both in the plasma and in the different tissues analyzed. A significant decrease in urinary undegraded GAG between the fourth and the sixth week of treatment was observed. Moreover, a biochemical reduction of GAG deposits was measured 8 weeks after treatment in the liver and kidney, on average 30 and 38%, respectively, while in the spleen GAG levels were almost normalized. Finally, the therapeutic effect was confirmed by histolochemical examination of the same tissues. Such effects were obtained following implantation of about 1.5 x 10(6) recombinant cells/animal. Taken together, these results represent a clear evidence of the therapeutic efficacy of this strategy in the MPS II mouse model, and encourage further evaluation of this approach for potential treatment of human beings.

A novel cytomedical vehicle capable of protecting cells against complement

We have developed "Cytomedicine," which consists of functional cells entrapped in semipermeable polymer, and previously reported that APA microcapsules could protect the entrapped cells from injury by cellular immune system. However, microencapsulated cells were not protected from humoral immune system. Here, we developed a novel APA microcapsule, in which APA microbeads (APA(Ba) microbeads) were modified to contain a barium alginate hydrogel within their centers in an attempt to make it more difficult for antibody and complement to permeate the microcapsules. The permeability of APA(Ba) microbeads was clearly less than that of APA microcapsules, presumably due to the presence of barium alginate hydrogel. Cells encapsulated within APA(Ba) microbeads were protected against treatment with xenogeneic anti-serum. Furthermore, murine pancreatic beta-cells encapsulated in APA(Ba) microbeads remained viable and continued to secrete insulin in response to glucose. Therefore, APA(Ba) microbeads may be a useful carrier for developing anti-complement device for cytomedical therapy.

Non-viral transfer approaches for the gene therapy of mucopolysaccharidosis type II (Hunter syndrome)

AIMS

Hunter syndrome is a rare X-linked lysosomal storage disorder caused by the deficiency of the housekeeping enzyme iduronate-2-sulphatase (IDS). Deficiency of IDS causes accumulation of undegraded dermatan and heparan-sulphate in various tissues and organs. Approaches have been proposed for the symptomatic therapy of the disease, including bone marrow transplantation and, very recently, enzyme replacement. To date, gene therapy strategies have considered mainly retroviral and adenoviral transduction of the correct cDNA. In this paper, two non-viral somatic gene therapy approaches are proposed: encapsulated heterologous cells and muscle electro-gene transfer (EGT).

METHODS

Hunter primary fibroblasts were co-cultured with either cell clones over-expressing the lacking enzyme or with the same incorporated in alginate microcapsules. For EGT, plasmid vector was injected into mouse quadriceps muscle, which was then immediately electro-stimulated.

RESULTS

Co-culturing Hunter primary fibroblasts with cells over-expressing IDS resulted in a three- to fourfold increase in fibroblast enzyme activity with respect to control cells. Fibroblast IDS activity was also increased after co-culture with encapsulated cells. EGT was able to transduce genes in mouse muscle, resulting in at least a tenfold increase in IDS activity 1-5 weeks after treatment.

CONCLUSION

Although preliminary, results from encapsulated heterologous cell clones and muscle EGT encourage further evaluations for possible application to gene therapy for Hunter syndrome.

Oxygen and inulin transport measurements in a planar tissue-engineered bioartificial organ

In vivo oxygen and inulin transport rates were measured in a planar tissue-engineered bioartificial organ implanted in a rat. A compartmental model was used to describe the transport of oxygen and inulin between the cell chamber, across the immunoisolation membrane, and within the neovascularized region adjacent to the immunoisolation membrane. A nonlinear regression analysis of the plasma inulin levels and the oxygen transport rate into the device provided information on the degree of vascularization in the region adjacent to the bioartificial organ. Key parameters that were obtained from the analysis of the in vivo transport data included the average capillary blood oxygen partial pressure, the Krogh tissue cylinder radius, the extracellular volume fraction, and the capillary blood residence time. These four parameters are important indicators for assessing the degree of vascularization in the tissue adjacent to the immunoisolation membrane in the bioartificial organ. The oxygen and inulin transport technique reported here is a useful tool for describing the in vivo transport characteristics of a bioartificial organ and for assessment of the vascularization within tissue engineered structures.

Characterization of algG encoding C5-epimerase in the alginate biosynthetic gene cluster of Pseudomonas fluorescens

The organization of the alginate gene cluster in Pseudomonas fluorescens was characterized. A bank of genomic DNA from P. fluorescens was mobilized to a strain of Pseudomonas aeruginosa with a transposon insertion (algJ::Tn501) in the alginate biosynthetic operon that rendered it non-mucoid. Phenotypic complementation in this heterologous host was observed, and a complementing clone containing 32 kb of P. fluorescens DNA was obtained. Southern hybridization studies showed that genes involved in alginate biosynthesis (e.g. algD, algG, and algA) were approximately in the same order and position as in P. aeruginosa. When the clone was mobilized to a P. aeruginosa algG mutant that produced alginate as polymannuronate due to its C5-epimerase defect, complementation was observed and the alginate from the recombinant strain contained L-guluronate as determined by proton nuclear magnetic resonance spectroscopy. A sequence analysis of the P. fluorescens DNA containing algG revealed sequences similar to P. aeruginosa algG that were also flanked by algE- and algX-like sequences. The predicted AlgG amino acid sequence of P. fluorescens was 67% identical (80% similar) to P. aeruginosa AlgG and 60% identical (76% similar) to Azotobacter vinelandii AlgG. As in P. aeruginosa, AlgG from P. fluorescens appeared to have a signal sequence that would localize it to the periplasm where AlgG presumably acts as a C5-epimerase at the polymer level. Non-polar algG knockout mutants of P. fluorescens were defective in alginate production, suggesting a potential role for this protein in polymer formation.

In vivo perivascular implantation of encapsulated packaging cells for prolonged retroviral gene transfer

Long-term benefits of coronary angioplasty remain limited by the treatment-induced renarrowing of arteries, termed restenosis. One of the mechanisms leading to restenosis is the proliferation of smooth muscle cells. Therefore, proliferating cells of the injured arterial wall, which can be selectively transduced by retroviruses, are potential targets for gene therapy strategies. A direct single-dose therapeutic application of retroviral vectors for inhibition of cell proliferation is normally limited by too low transduction efficiencies. Encapsulated retrovirus-producing cells release viral vectors from microcapsules, and may enhance the transduction efficiency by prolonged infection. Primary and immortal murine and porcine cells and murine retrovirus-producing cells were encapsulated in cellulose sulphate. Cell viability was monitored by analysing cell metabolism. Safety, stability, transfer efficiency and extent of restenosis using capsules were determined in a porcine restenosis model for local gene therapy using morphometry, histology, in situ beta-galactosidase assay and PCR. Encapsulation of cells did not impair cell viability. Capsules containing retrovirus-producing cells expressing the beta-galactosidase reporter gene were implanted into periarterial tissue or a pig model of restenosis. Three weeks following implantation, beta-galactosidase activity was detected in the pericapsular tissue with a transduction efficiency of approximately 1 in 500 cells. Adventitial implantation of vector-producing encapsulated cells for gene therapy may, therefore, facilitate successful targeting of proliferating vascular smooth muscle cells, and allow stable integration of therapeutic genes into surrounding cells. The encapsulation of vector-producing cells could represent a novel and feasible way to optimize local retroviral gene therapy.

Grafting of encapsulated BDNF-producing fibroblasts into the injured spinal cord without immune suppression in adult rats

Grafting of genetically modified cells that express therapeutic products is a promising strategy in spinal cord repair. We have previously grafted BDNF-producing fibroblasts (FB/BDNF) into injured spinal cord of adult rats, but survival of these cells requires a strict protocol of immune suppression with cyclosporin A (CsA). To develop a transplantation strategy without the detrimental effects of CsA, we studied the properties of FB/BDNF that were encapsulated in alginate-poly-L-ornithine, which possesses a semipermeable membrane that allows production and diffusion of a therapeutic product while protecting the cells from the host immune system. Our results show that encapsulated FB/BDNF, placed in culture, can survive, secrete bioactive BDNF and continue to grow for at least one month. Furthermore, encapsulated cells that have been stored in liquid nitrogen retain the ability to grow and express the transgene. Encapsulated FB/BDNF survive for at least one month after grafting into an adult rat cervical spinal cord injury site in the absence of immune suppression. Transgene expression decreased within two weeks after grafting but resumed when the cells were harvested and re-cultured, suggesting that soluble factors originating from the host immune response may contribute to the downregulation. In the presence of capsules that contained FB/BDNF, but not cell-free control capsules, there were many axons and dendrites at the grafting site. We conclude that alginate encapsulation of genetically modified cells may be an effective strategy for delivery of therapeutic products to the injured spinal cord and may provide a permissive environment for host axon growth in the absence of immune suppression.

Gene medicine : a new field of molecular medicine

Gene therapy has emerged as a new concept of therapeutic strategies to treat diseases which do not respond to the conventional therapies. The principle of gene therapy is to introduce genetic materials into patient cells to produce therapeutic proteins in these cells. Gene therapy is now at the stage where a number of dinical trials have been carried out to patients with gene-deficiency disease or cancer. Genetic materials for gene therapy are generally composed of gene expression system and gene delivery system. For the dinical application of gene therapy in a way which conventional drugs are used, researches have been focused on the design of gene delivery system which can offer high transfection efficiency with minimal toxicity. Currently, viral delivery systems generally provide higher transfection efficiency compared with non-viral delivery systems while non-viral delivery systems are less toxic, less immunogenic and manufacturable in large scale compared with viral systems. Recently, novel strategies towards the design of new non-viral delivery system, combination of viral and non-viral delivery systems and targeted delivery system have been extensively studied. The continued effort in this area will lead us to develop gene medicine as 'gene as a drug' in the near future.

Osmotic pressure test: a simple, quantitative method to assess the mechanical stability of alginate microcapsules

Implantation of microencapsulated, nonautologous cells and tissues is an effective method to deliver therapeutic proteins in vivo. Its success depends on the maintenance of the immunoisolating barrier provided by the microcapsule. Thus, one goal in the development of this technology is to create mechanically stable microcapsules. We have developed an osmotic pressure test to quantify the strength of microcapsules by exposing alginate microcapsules to a graded series of hypotonic solutions and quantifying the percentage of broken microcapsules. The test was validated by confirming the relative strengths of different types of alginate capsules, previously known from implantation in dogs to have differing mechanical stability in vivo. Thus, solid alginate microcapsules crosslinked with Ba(2+) were shown to be stronger than those crosslinked with Ca(2+), which in turn were shown to be stronger than the corresponding hollow alginate microcapsules. The incorporation of cells was demonstrated to reduce the mechanical stability of the microcapsules significantly. Hence, this test provides a simple and quantitative method for rapidly determining the strength of a large number of microcapsules. Thus, it is suitable for monitoring the mechanical stability of various types of microcapsules, predicting the performance of microcapsules in vivo, and for quality control of microcapsules during scale-up productions.

Alginate-encapsulated producer cells: a potential new approach for the treatment of malignant brain tumors

In recent years gene therapy has evolved as a new treatment for brain tumors, where genetically engineered cells can be used to deliver specific substances to target cells. However, clinical success has been limited due to insufficient gene transfer, lack of prolonged gene expression, and immunorejection of producer cells. These obstacles may be overcome by encapsulating producer cells into immunoisolating substances such as alginate. This may provide a stable in situ delivery system of specific proteins, which can interfere with tumor growth and differentiation. This article represents a fundamental study describing the in vitro and the in vivo behavior of alginate-encapsulated producer cells. The viability and cell cycle distribution of encapsulated NIH 3T3 cells was studied by confocal laser scanning microscopy (CLSM) and by flow cytometry. The CLSM study showed a high viability of the encapsulated NIH 3T3 cells during 9 weeks in culture. The flow cytometric analysis revealed a change in cellular ploidy after 1 week in culture, with normalization in ploidy after 3 and 9 weeks. The production of the bacterial E. coli beta-galactosidase in alginate-encapsulated BT4CnVlacZ cells was studied by x-gal staining, and the cells expressed prolonged beta-galactosidase activity. H528 hybridoma cells producing monoclonal antibodies (mAbs) against the human epidermal growth factor receptor (EGFR) were encapsulated in alginate, and the mAb release was determined. The release of mAbs stabilized around 400 ng/ml/h after 12 days in vitro. To actually demonstrate that alginate-encapsulated H528 cells potentially inhibit a heterogeneous glioma cell population, cell migration from human GaMg glioma spheroids was studied during stimulation with EGF in the presence of encapsulated H528 cells. The migration in vitro was totally inhibited in the presence of H528 encapsulated cells. Alginate beads with H528 cells were also implanted into rat brains, and after 9 weeks the distribution of mAbs within the brain was studied by immunohistochemistry. It is shown that the alginate entrapped H528 cells produce mAbs inside the brain for prolonged periods and that the mAbs are distributed within all CSF compartments. Encapsulated producer cells represent a potential delivery system for specific proteins to brain tumors. Different producer cells may be encapsulated in alginate to target phenotypic features and microenvironmental factors, which may influence the progressive growth of brain tumors.

Insights into the molecular pathogenesis of atherosclerosis and therapeutic strategies using gene transfer

Gene therapy for the treatment of atherosclerosis and related diseases has shown its potential in animal models and in the first human trials. Gene transfer to the vascular system can be performed both via intravascular and extravascular periadventitial routes. Intravascular gene transfer can be done with several types of catheters under fluoroscopic control. Extravascular gene transfer, on the other hand, provides a well-targeted gene delivery route available during vascular surgery. It can be done with direct injection or by using perivascular cuffs or surgical collagen sheets. Ex vivo gene delivery via transfected smooth muscle cells or endothelial cells might be useful for the production of secreted therapeutic compounds. Gene transfer to the liver has been used for the treatment of hyperlipidemia. The first clinical trials for the induction of therapeutic angiogenesis in ischemic myocardium or peripheral muscles with VEGF or FGF gene transfer are under way and preliminary results are promising. VEGF has also been used for the prevention of postangioplasty restenosis because of its capability to induce endothelial repair and production of NO and prostacyclin. However, further basic research is needed to fully understand the pathophysiological mechanisms involved in conditions related to atherosclerosis. Also, further development of gene transfer vectors and gene delivery techniques will improve the efficacy and safety of human gene therapy.

Encapsulation for somatic gene therapy

With the human genome project approaching its completion date of 2005, gene-based technology will play an increasingly important role in health-care delivery. Non-autologous somatic gene therapy is a novel application in which non-autologous cell lines engineered to secrete a recombinant protein are enclosed within immunoisolation devices and implanted into all patients requiring the same product for therapy. The development of this technology requires a multi-disciplinary effort towards optimization of the biomaterial used to manufacture the implantable devices and selection of the appropriate cell lines for enclosure. The efficacy of this technology is illustrated in the treatment of dwarfism and lysosomal storage disease in murine models. The potential of a safe and cost-effective gene-based delivery method should have wide applications in treating both classical genetic disorders and non-Mendelian diseases.

Method for measuring in vivo oxygen transport rates in a bioartificial organ

Oxygen transport is crucial for the proper functioning of a bioartificial organ. In many cases, the immunoisolation membrane used to protect the transplanted cells from the host's immune system can be a significant barrier to oxygen transport. A method is described for measuring the in vitro and in vivo oxygen transport characteristics of a planar immunoisolation membrane. The in vitro oxygen permeability of the membrane was found to equal 9.22 x 10(-4) cm/sec and was essentially the same as the in vivo value of 9.51 x 10(-4) cm/sec. The fact that the in vitro and in vivo membrane permeabilities are identical indicates that any fibrotic tissue adjacent to the immunoisolation membrane did not present a significant resistance to the transport of oxygen. The measured oxygen permeability was also found consistent with the solute permeabilities obtained in a previous study for larger molecules. Based on the oxygen permeability results, theoretical calculations for this particular membrane indicate that about 1,100 islets of Langerhans/cm2 of membrane area can be sustained at high tissue densities and only 660 islets/cm2 can be supported at low tissue densities.

Control of erythropoietin secretion by doxycycline or mifepristone in mice bearing polymer-encapsulated engineered cells

Cell encapsulation offers a safe and manufacturable method for the systemic delivery of therapeutic proteins from genetically engineered cells. However, control of dose delivery remains a major issue with regard to clinical application. We generated populations of immortalized murine NIH 3T3 fibroblasts that secrete mouse erythropoietin (Epo) in response to stimulation by doxycycline or mifepristone. Engineered cells were introduced into AN69 hollow fibers, which were implanted in the peritoneal cavity or recipient mice. Animals receiving doxycycline or mifepristone showed stable polyhemia and increased serum Epo concentrations over a 6-month observation period, whereas animals not receiving the inducer drug had normal hematocrits. Epo secretion could be switched on and off, depending on the presence of doxycycline in the drinking water. In contrast, polyhemia was hardly reversible after subcutaneous injections of mifepristone. These data show that a permanent and regulated systemic delivery of a therapeutic protein can be obtained by the in vivo implantation of engineered allogeneic cells immunoprotected in membrane polymers.

Delivery of recombinant gene products to the central nervous system with nonautologous cells in alginate microcapsules

Somatic gene therapy using nonautologous recombinant cells immunologically protected with alginate microcapsules has been successfully used to treat rodent genetic diseases. We now report the delivery of recombinant gene products to the brain in rodents by implanting microencapsulated cells for the purpose of eventually treating neurodegenerative diseases with this technology. Alginate-poly-L-lysine-alginate microcapsules enclosing mouse C2C12 myoblasts expressing the marker gene human growth hormone (hGH) at 95+/-20 ng/million cells/hr were implanted into the right lateral ventricles of mice under stereotaxic guidance. Control mice were implanted similarly with nontransfected but encapsulated cells. Delivery of hGH to the different regions of the brain at various times postimplantation was examined. At 7, 28, 56, and 112 days postimplantation, hGH was detected at high levels around the implantation site and also at lower levels in the surrounding regions, while control mice showed no signal. Immunohistochemical staining of the implanted brains showed that on days 7, 56, and 112 postimplantation, hGH was localized in the tissues around the implantation site. Mice implanted with encapsulated but nontransfected cells showed no signal. Hence, the feasibility of using encapsulated nonautologous cells to deliver recombinant gene products to the brain for extended periods may allow the application of this technology to the treatment of neurodegenerative genetic disorders.

Use of nonautologous microencapsulated fibroblasts in growth hormone gene therapy to improve growth of midget swine

The aim of the present study was to investigate the expression activity, both in vitro and in vivo, of the porcine growth hormone complementary DNA (pGH cDNA) in porcine fetal fibroblast (PFF) cells. The pGH gene had been constructed inside the bicistronic retroviral vector PSN and subsequently transfected into PFF cells further encapsulated with immunoprotective microcapsules. This would provide a way to evaluate the improvement in growth performance of Tao-Yuan swine by the use of nonautologous microencapsulated fibroblasts carrying the pGH cDNA via the technique of somatic gene therapy. Results from Southern blot analysis confirmed that the full length of the pGH cDNA was completely integrated into the genome of the PFF cells after they had been infected one to four times using a PSN retroviral vector. Moreover, Northern blot analysis showed that high transcription activity was present in clones infected twice, and exogenous pGH secretion was found when the pGH-infected PFF had been further cultured for 48 hr in vitro and subjected to immunoblot assay. Encapsulation of the pGH-PFF with an alginate-poly-L-lysine-alginate membrane did not show any deterioration in their proliferation and survival both in vitro and in vivo. The pGH gene in encapsulated recombinant fibroblasts was fully expressed after it had been transplanted into the peritoneal cavity of the Tao-Yuan swine, and reverse transcription-polymerase chain reaction (RT-PCR) analysis was performed on the microcapsules retrieved 1 month later. The feasibility of pGH gene therapy to improve midget Tao-Yuan swine growth enhancement is further supported by the fact that transplantation of the encapsulated recombinant fibroblast cells resulted in a much more significant increase in weight gain than in those swine in either the age-matched untreated control group or in those that had been transplanted with uncapsulated recombinant PFF cells (10.56 +/- 1.01 kg versus 6.95 +/- 0.94 and 5.27 +/- 1.30 kg; p < 0.05). These experimental data suggest that growth hormone gene therapy did provide an alternative approach for growth improvement in midget Tao-Yuan swine.

Host response to tissue engineered devices

The two main components of a tissue engineered device are the transplanted cells and the biomaterial, creating a device for the restoration or modification of tissue or organ function. The implantation of polymer/cell constructs combines concepts of biomaterials and cell transplantation. The interconnections between the host responses to the biomaterial and transplanted cells determines the biocompatibility of the device. This review describes the inflammatory response to the biomaterial component and immune response towards transplanted cells. Emphasis is on how the presence of the transplanted cell construct affects the host response. The inflammatory response towards a biomaterial can impact the immune response towards transplanted cells and vice versa. Immune rejection is the most important host response towards the cellular component of tissue engineered devices containing allogeneic, xenogeneic or immunogenic ex vivo manipulated autologous cells. The immune mechanisms towards allografts and xenografts are outlined to provide a basis for the mechanistic hypotheses of the immune response towards encapsulated cells, with antigen shedding and the indirect pathway of antigen presentation predominating. A review of experimental evidence illustrates examples of the inflammatory response towards biodegradable polymer scaffold materials, examples of devices appropriately integrated as assessed morphologically with the host for various applications including bone, nerve, and skin regeneration, and of the immune response towards encapsulated allogeneic and xenogeneic cells.

Delivery of recombinant gene product to canines with nonautologous microencapsulated cells

An alternative and potentially cost-effective approach to somatic gene therapy is to engineer a universal cell line secreting the desired product suitable for implantation into different patients without immune rejection. Encapsulating these cells in immunoprotective alginate microcapsules showed that this approach was effective in treating murine models of human diseases. We now report that this approach is also effective in delivering recombinant gene products to large animals. Canine MDCK cells encapsulated in alginate microcapsules were able to deliver recombinant human growth hormone to nonautologous dogs in vivo. However, the same microcapsules capable of prolonged delivery in mice soon disappeared after implantation in dogs. In contrast, when these microcapsules were modified by using a higher concentration of alginate cross-linked with barium instead of calcium, and by fabricating the alginate as a gelled bead without solubilizing the core, more prolonged and higher levels of recombinant product were obtained. Laminating the surface of the beads with poly-L-lysine and alginate provided an even more mechanically stable device that lasted for >2 months instead of <14 days in vivo and delivered >20 ng of human growth hormone/ml of plasma within the first week. The apparent disappearance of the growth hormone from the circulation after day 14 was due to rapid clearance by anti-human growth hormone antibodies and not due to loss of cell viability. However, all microcapsules provoked an inflammatory reaction, causing mild omentitis, and eventually disappeared from the intraperitoneal cavity. In conclusion, systemic delivery of recombinant gene products with nonautologous cells protected in alginate microcapsules has been shown to be feasible in canine recipients. While improved level and duration of delivery have been achieved by increasing the mechanical stability of the microcapsules, further improvements in biocompatibility and stability will be required for human application.

Enhanced anti-inflammatory effects of Cu, Zn-superoxide dismutase delivered by genetically modified skin fibroblasts in vitro and in vivo

PURPOSE

The purpose of this work was to evaluate the anti-inflammatory effects of secretable human Cu, Zn-superoxide dismutase (hSOD) delivered by genetically modified skin fibroblasts in vitro and in vivo.

METHODS

Rat skin fibroblasts were transfected with pRc/CMV-ILSOD including secretable SOD-coding cDNA. The effects of host and transformants on oxidative stress in vitro models using the xanthine/xanthine oxidase (X/XO) system were examined to study the paracrine SOD action. The anti-inflammatory effects by transplantation of host and transformants were evaluated in an acute inflammation model, carrageenin-induced paw edema, in rats.

RESULTS

The transformants (ILSOD cells) secreted SOD protein into the extracellular space, and the extracellular SOD activity in ILSOD cells cultures was significantly increased compared with that in host cell cultures. ILSOD cells diminished the cytotoxic activity by X/XO in a paracrine fashion. These protective effects of ILSOD cells against X/XO-induced cytotoxicity correlated well with the decrease in lipid peroxidation in the damaged cells. The in vivo study showed that transplantation of ILSOD cell suspensions into the hind paw in rats inhibited carrageenin-induced paw edema for at least 7 days, and the degree and the durability of these inhibitory effects were dependent on the number of ILSOD cells transplanted. These inhibitory effects of ILSOD cell suspensions were reduced by co-administration of antiserum for hSOD. Furthermore, the healing of paw edema caused by carrageenin was markedly enhanced by transplantation of ILSOD cells into the edemics hind paw.

CONCLUSIONS

The findings suggested that genetically modified skin fibroblasts are a suitable delivery system for obtaining an efficient and continuous supply of SOD to the target site, and this strategy may be a useful drug delivery system for therapeutic proteins.

Characterization of human amniotic epithelial cells transformed with origin-defective SV40 T-antigen gene

This paper describes characteristics of human amniotic epithelial cells (AEC) transfected with a gene of origin-defective simian virus (SV) 40 large T-antigen (pMTIOD). Normal AEC before transfection with pMTIOD exhibited only low proliferative potential under our culture conditions. On the other hand, AEC cells transfected with pMTIOD exhibited greater proliferative potentials. Flow cytometry and immunohistochemistry analyses showed that both the primary and the transfected AEC did not express appreciable levels of class II antigens. However, the expression of class I antigen of the transfected AEC cells was slightly increased. The cells obtained in this experiment have the ability to induce tumors in severely combined immunodeficiency mice. This finding suggests that established AEC line can be used as a tool to investigate possible expression of the desired gene in human AEC and the gene products, however, was not suitable as a gene carrier to the recipient. Further experiments will be required to establish AEC as a transgene carrier for somatic cell gene therapy.

Cytomedical therapy for IgG1 plasmacytosis in human interleukin-6 transgenic mice using hybridoma cells microencapsulated in alginate-poly(L)lysine-alginate membrane

Cytomedical therapy for human interleukin-6 transgenic mice (hIL-6 Tgm) was implemented by the intraperitoneal injection of alginate-poly(L)lysine-alginate (APA) membranes microencapsulating SK2 hybridoma cells (APA-SK2 cells) which secrete anti-hIL-6 monoclonal antibodies (SK2 mAb). IgG1 plasmacytosis in the hIL-6 Tgm was suppressed by a single injection of APA-SK2 cells, and the survival time of these mice was remarkably prolonged. The viable cell number and the SK2 mAb-secretion of APA-SK2 cells increased for at least one month both under culture conditions and in allogeneic recipients (in vivo). Moreover, SK2 mAb which were secreted from APA-SK2 cells injected into allogeneic recipients was detected in serum at high concentrations; 3-5 mg/ml from day 14 to day 50 post-injection. In contrast, the injection of free SK2 cells had no therapeutic effect on hIL-6 Tgm. These results strongly suggest that APA membranes microencapsulating cells which were modified to secrete molecules useful for the treatment of a disorder were effective as an in vivo long-term delivery system of bioactive molecules, as 'cytomedicine'.

Immunological studies of SK2 hybridoma cells microencapsulated with alginate-poly(L)lysine-alginate (APA) membrane following allogeneic transplantation

Microencapsulation of living cells or tissues has been proposed to prevent their immune destruction following transplantation. In this study, we examined whether SK2 hybridoma cells microencapsulated in an alginate-poly(L)lysine-alginate (APA) membrane (APA-SK2 cells) were immunoisolated from the allogeneic host's immune system using a cytotoxicity test. The APA membrane inhibited the activation of the host's cellular immune response, but did not prevent the production of cytotoxic antibodies against entrapped SK2 cells following allogeneic transplantation. However, the APA-SK2 cells remained vital in SK2 cell-immunized mice as well as in intact mice. We considered that complement regulatory factors which were present on cell membrane and had species-specific restriction blocked the complement-mediated cell lysis on allogeneic transplantation, since APA-SK2 cells were destroyed by rabbit anti-SK2 cell antiserum. Our results demonstrated that APA membrane could inhibit cell-cell contact between entrapped cells and the host's lymphocytes, but could not completely protect the entrapped cells from xenogeneic humoral immunity.

Microencapsulation--an alternative approach to gene therapy

Non-autologous somatic gene therapy' is a novel approach to gene therapy which does not depend on genetic modification of the patient's own cells. Recombinant cell lines secreting a desired therapeutic gene product can be implanted into different patients requiring the same product replacement. Graft rejection is avoided by enclosing these cells in immuno-isolation devices whose permeability excludes the host's immune mediators but permits the transit of nutrients and recombinant gene products. The feasibility of this strategy is demonstrated by expression of recombinant human enzymes, hormones and coagulation factors from fibroblasts or myoblasts enclosed within alginate-poly-L-lysine-alginate microcapsules. Its clinical efficacy is demonstrated by the correction of pathological phenotypes in murine models of human endocrine and lysosomal storage diseases. Hence, this approach may lead to a potentially cost-effective method of gene-based therapy.

Growth retardation--an unexpected outcome from growth hormone gene therapy in normal mice with microencapsulated myoblasts

Recently, we have succeeded in using nonautologous myoblasts engineered to secrete mouse growth hormone (GH) to correct partially the growth retardation of the Snell dwarf mice, which suffer from pituitary GH deficiency. The allogeneic myoblasts were protected from immune rejection by enclosure in permselective microcapsules fabricated from alginate, thus validating the clinical efficacy of using universal nonautologous cells for somatic gene therapy. Because GH therapy is considered also for treating patients with normal pituitary function, we now apply this protocol to treat normal mice to evaluate the potential consequences of using GH gene therapy in subjects with no demonstrated GH deficiency. When microencapsulated allogeneic myoblasts engineered to secrete mouse GH were implanted into normal male and female mice, contrary to expectation, the treated animals became significantly shorter and lost weight; their internal organs became smaller and their tibial growth plates were less differentiated, indicating reduced skeletal growth. Females were more severely affected than males and 2 animals died by day 13 of unknown cause. By day 70, most of the abnormalities were restored to normal except for body weights, which remained below normal. In conclusion, although somatic gene therapy for GH delivery is beneficial for pituitary dwarfism, it may have adverse metabolic consequences in those with normal hypothalamic-pituitary functions, and the female mice were more severely affected than males.