In vivo delivery of recombinant human growth hormone from genetically engineered human fibroblasts implanted within Baxter immunoisolation devices

Sustained secretion of human growth hormone from TheraCyte devices encapsulated with PiggyBac-engineered retinal pigment epithelium cells

Growth hormone (GH) deficiency is characterized by impaired growth and development, and is currently treated by repeated administration of recombinant human GH (hGH). Encapsulated cell therapy (ECT) may offer a less demanding treatment-strategy for long-term production and release of GH into circulation. We used PiggyBac-based (PB) transposon delivery for engineering retinal pigment epithelial cells (ARPE-19), and tested a series of viral and non-viral promoters as well as codon-optimization to enhance transgene expression. Engineered cells were loaded into TheraCyte macrocapsules and secretion was followed in vitro and in vivo. The cytomegalovirus (CMV) promoter supports strong and persistent transgene expression, and we achieved clonal cell lines secreting over 6 µg hGH/10⁶ cells/day. Codon-optimization of the hGH gene did not improve secretion. ARPE-19 cells endured encapsulation in TheraCyte devices, and resulted in steady hormone release for at least 60 days in vitro. A short-term pilot experiment in immunodeficient SCID mice demonstrated low systemic levels of hGH from a single 40 µL capsule implanted subcutaneously. No significant increase in weight increase or systemic hGH was detected after 23 days in the GH-deficient lit/SCID mouse model using 4.5 µL capsules loaded with the highest secreting clone of ARPE-19 cells. Our results demonstrate that PB-mediated engineering of ARPE-19 is an efficient way to generate hormone secreting cell lines compatible with macroencapsulation, and our CMV-driven expression cassette allows for identification of clones with high level and long-term secretory activity without addition of insulator elements. Our results pave the way for further in vivo studies of encapsulated cell therapy.

Reprogramming adipose mesenchymal stem cells into islet β-cells for the treatment of canine diabetes mellitus

BACKGROUND

Islet transplantation is an excellent method for the treatment of type I diabetes mellitus. However, due to the limited number of donors, cumbersome isolation and purification procedures, and immune rejection, the clinical application is greatly limited. The development of a simple and efficient new method to obtain islet β-cells is a key problem that urgently requires a solution for the treatment of type I diabetes mellitus.

METHODS

In this study, Pbx1, Rfx3, Pdx1, Ngn3, Pax4 and MafA were used to form a six-gene combination to efficiently reprogram aMSCs (adipose mesenchymal stem cells) into ra-βCs (reprogrammed aMSCs-derived islet β-cells), and the characteristics and immunogenicity of ra-βCs were detected. Feasibility of ra-βCs transplantation for the treatment of diabetes mellitus in model dogs and clinical dogs was detected.

RESULTS

In this study, aMSCs were efficiently reprogrammed into ra-βCs using a six-gene combination. The ra-βCs showed islet β-cell characteristics. The immunogenicity of ra-βCs was detected and remained low in vitro and increased after transplantation. The cotransplantation of ra-βCs and aMSCs in the treatment of a model and clinical cases of canine diabetes mellitus achieved ideal therapeutic effects.

CONCLUSIONS

The aMSCs were efficiently reprogrammed into ra-βCs using a six-gene combination. The cotransplantation of ra-βCs and aMSCs as a treatment for canine diabetes is feasible, which provides a theoretical basis and therapeutic method for the treatment of canine diabetes.

Sustained subcutaneous delivery of secretome of human cardiac stem cells promotes cardiac repair following myocardial infarction

AIMS

To establish pre-clinical proof of concept that sustained subcutaneous delivery of the secretome of human cardiac stem cells (CSCs) can be achieved in vivo to produce significant cardioreparative outcomes in the setting of myocardial infarction.

METHODS AND RESULTS

Rats were subjected to permanent ligation of left anterior descending coronary artery and randomized to receive subcutaneous implantation of TheraCyte devices containing either culture media as control or 1 × 106 human W8B2+ CSCs, immediately following myocardial ischaemia. At 4 weeks following myocardial infarction, rats treated with W8B2+ CSCs encapsulated within the TheraCyte device showed preserved left ventricular ejection fraction. The preservation of cardiac function was accompanied by reduced fibrotic scar tissue, interstitial fibrosis, cardiomyocyte hypertrophy, as well as increased myocardial vascular density. Histological analysis of the TheraCyte devices harvested at 4 weeks post-implantation demonstrated survival of human W8B2+ CSCs within the devices, and the outer membrane was highly vascularized by host blood vessels. Using CSCs expressing plasma membrane reporters, extracellular vesicles of W8B2+ CSCs were found to be transferred to the heart and other organs at 4 weeks post-implantation. Furthermore, mass spectrometry-based proteomic profiling of extracellular vesicles of W8B2+ CSCs identified proteins implicated in inflammation, immunoregulation, cell survival, angiogenesis, as well as tissue remodelling and fibrosis that could mediate the cardioreparative effects of secretome of human W8B2+ CSCs.

CONCLUSIONS

Subcutaneous implantation of TheraCyte devices encapsulating human W8B2+ CSCs attenuated adverse cardiac remodelling and preserved cardiac function following myocardial infarction. The TheraCyte device can be employed to deliver stem cells in a minimally invasive manner for effective secretome-based cardiac therapy.

Immune Protection of Stem Cell-Derived Islet Cell Therapy for Treating Diabetes

Insulin injection is currently the main therapy for type 1 diabetes (T1D) or late stage of severe type 2 diabetes (T2D). Human pancreatic islet transplantation confers a significant improvement in glycemic control and prevents life-threatening severe hypoglycemia in T1D patients. However, the shortage of cadaveric human islets limits their therapeutic potential. In addition, chronic immunosuppression, which is required to avoid rejection of transplanted islets, is associated with severe complications, such as an increased risk of malignancies and infections. Thus, there is a significant need for novel approaches to the large-scale generation of functional human islets protected from autoimmune rejection in order to ensure durable graft acceptance without immunosuppression. An important step in addressing this need is to strengthen our understanding of transplant immune tolerance mechanisms for both graft rejection and autoimmune rejection. Engineering of functional human pancreatic islets that can avoid attacks from host immune cells would provide an alternative safe resource for transplantation therapy. Human pluripotent stem cells (hPSCs) offer a potentially limitless supply of cells because of their self-renewal ability and pluripotency. Therefore, studying immune tolerance induction in hPSC-derived human pancreatic islets will directly contribute toward the goal of generating a functional cure for insulin-dependent diabetes. In this review, we will discuss the current progress in the immune protection of stem cell-derived islet cell therapy for treating diabetes.

Biomaterials for Personalized Cell Therapy

Cell therapy has already had an important impact on healthcare and provided new treatments for previously intractable diseases. Notable examples include mesenchymal stem cells for tissue regeneration, islet transplantation for diabetes treatment, and T cell delivery for cancer immunotherapy. Biomaterials have the potential to extend the therapeutic impact of cell therapies by serving as carriers that provide 3D organization and support cell viability and function. With the growing emphasis on personalized medicine, cell therapies hold great potential for their ability to sense and respond to the biology of an individual patient. These therapies can be further personalized through the use of patient-specific cells or with precision biomaterials to guide cellular activity in response to the needs of each patient. Here, the role of biomaterials for applications in tissue regeneration, therapeutic protein delivery, and cancer immunotherapy is reviewed, with a focus on progress in engineering material properties and functionalities for personalized cell therapies.

Oxygenation strategies for encapsulated islet and beta cell transplants

Human allogeneic islet transplantation (ITx) is emerging as a promising treatment option for qualified patients with type 1 diabetes. However, widespread clinical application of allogeneic ITx is hindered by two critical barriers: the need for systemic immunosuppression and the limited supply of human islet tissue. Biocompatible, retrievable immunoisolation devices containing glucose-responsive insulin-secreting tissue may address both critical barriers by enabling the more effective and efficient use of allogeneic islets without immunosuppression in the near-term, and ultimately the use of a cell source with a virtually unlimited supply, such as human stem cell-derived β-cells or xenogeneic (porcine) islets with minimal or no immunosuppression. However, even though encapsulation methods have been developed and immunoprotection has been successfully tested in small and large animal models and to a limited extent in proof-of-concept clinical studies, the effective use of encapsulation approaches to convincingly and consistently treat diabetes in humans has yet to be demonstrated. There is increasing consensus that inadequate oxygen supply is a major factor limiting their clinical translation and routine implementation. Poor oxygenation negatively affects cell viability and β-cell function, and the problem is exacerbated with the high-density seeding required for reasonably-sized clinical encapsulation devices. Approaches for enhanced oxygen delivery to encapsulated tissues in implantable devices are therefore being actively developed and tested. This review summarizes fundamental aspects of islet microarchitecture and β-cell physiology as well as encapsulation approaches highlighting the need for adequate oxygenation; it also evaluates existing and emerging approaches for enhanced oxygen delivery to encapsulation devices, particularly with the advent of β-cell sources from stem cells that may enable the large-scale application of this approach.

Glucose-stimulated insulin release: Parallel perifusion studies of free and hydrogel encapsulated human pancreatic islets

To explore the effects immune-isolating encapsulation has on the insulin secretion of pancreatic islets and to improve our ability to quantitatively describe the glucose-stimulated insulin release (GSIR) of pancreatic islets, we conducted dynamic perifusion experiments with isolated human islets. Free (unencapsulated) and hydrogel encapsulated islets were perifused, in parallel, using an automated multi-channel system that allows sample collection with high temporal resolution. Results indicated that free human islets secrete less insulin per unit mass or islet equivalent (IEQ) than murine islets and with a less pronounced first-phase peak. While small microcapsules (d = 700 µm) caused only a slightly delayed and blunted first-phase insulin response compared to unencapsulated islets, larger capsules (d = 1,800 µm) completely blunted the first-phase peak and decreased the total amount of insulin released. Experimentally obtained insulin time-profiles were fitted with our complex insulin secretion computational model. This allowed further fine-tuning of the hormone-release parameters of this model, which was implemented in COMSOL Multiphysics to couple hormone secretion and nutrient consumption kinetics with diffusive and convective transport. The results of these GSIR experiments, which were also supported by computational modeling, indicate that larger capsules unavoidably lead to dampening of the first-phase insulin response and to a sustained-release type insulin secretion that can only slowly respond to changes in glucose concentration. Bioartificial pancreas type devices can provide long-term and physiologically desirable solutions only if immunoisolation and biocompatibility considerations are integrated with optimized nutrient diffusion and insulin release characteristics by design.

Encapsulated cellular implants for recombinant protein delivery and therapeutic modulation of the immune system

Ex vivo gene therapy using retrievable encapsulated cellular implants is an effective strategy for the local and/or chronic delivery of therapeutic proteins. In particular, it is considered an innovative approach to modulate the activity of the immune system. Two recently proposed therapeutic schemes using genetically engineered encapsulated cells are discussed here: the chronic administration of monoclonal antibodies for passive immunization against neurodegenerative diseases and the local delivery of a cytokine as an adjuvant for anti-cancer vaccines.

Oxygen supply to encapsulated therapeutic cells

Therapeutic cells encapsulated in immunobarrier devices have promise for treatment of a variety of human diseases without immunosuppression. The absence of sufficient oxygen supply to maintain viability and function of encapsulated tissue has been the most critical impediment to progress. Within the framework of oxygen supply limitations, we review the major issues related to development of these devices, primarily in the context of encapsulated islets of Langerhans for treating diabetes, including device designs and materials, supply of tissue, protection from immune rejection, and maintenance of cell viability and function. We describe various defensive measures investigated to enhance survival of transplanted tissue, and we review the diverse approaches to enhancement of oxygen transport to encapsulated tissue, including manipulation of diffusion distances and oxygen permeability of materials, induction of neovascularization with angiogenic factors and vascularizing membranes, and methods for increasing the oxygen concentration adjacent to encapsulated tissue so as to exceed that in the microvasculature. Recent developments, particularly in this latter area, suggest that the field is ready for clinical trials of encapsulated therapeutic cells to treat diabetes.

Encapsulated islets for diabetes therapy: history, current progress, and critical issues requiring solution

Insulin therapy became a reality in 1921 dramatically saving lives of people with diabetes, but not protecting them from long-term complications. Clinically successful free islet implants began in 1989 but require life long immunosuppression. Several encapsulated islet approaches have been ongoing for over 30 years without defining a clinically relevant product. Macro-devices encapsulating islet mass in a single device have shown long-term success in large animals but human trials have been limited by critical challenges. Micro-capsules using alginate or similar hydrogels encapsulate individual islets with many hundreds of promising rodent results published, but a low incidence of successful translation to large animal and human results. Reduction of encapsulated islet mass for clinical transplantation is in progress. This review covers the status of both early and current studies including the presentation of corporate efforts involved. It concludes by defining the critical items requiring solution to enable a successful clinical diabetes therapy.

Improvement of islet function in a bioartificial pancreas by enhanced oxygen supply and growth hormone releasing hormone agonist

Islet transplantation is a feasible therapeutic alternative for metabolically labile patients with type 1 diabetes. The primary therapeutic target is stable glycemic control and prevention of complications associated with diabetes by reconstitution of endogenous insulin secretion. However, critical shortage of donor organs, gradual loss in graft function over time, and chronic need for immunosuppression limit the indication for islet transplantation to a small group of patients. Here we present a promising approach to address these limitations by utilization of a macrochamber specially engineered for islet transplantation. The s.c. implantable device allows for controlled and adequate oxygen supply and provides immunological protection of donor islets against the host immune system. The minimally invasive implantable chamber normalized blood glucose in streptozotocin-induced diabetic rodents for up to 3 mo. Sufficient graft function depended on oxygen supply. Pretreatment with the growth hormone-releasing hormone (GHRH) agonist, JI-36, significantly enhanced graft function by improving glucose tolerance and increasing β-cell insulin reserve in rats thereby allowing for a reduction of the islet mass required for metabolic control. As a result of hypervascularization of the tissue surrounding the device, no relevant delay in insulin response to glucose changes has been observed. Consequently, this system opens up a fundamental strategy for therapy of diabetes and may provide a promising avenue for future approaches to xenotransplantation.

Continuous and high-level in vivo delivery of endostatin from recombinant cells encapsulated in TheraCyte immunoisolation devices

Endostatin (ES) is a potent inhibitor of angiogenesis and tumor growth. Continuous ES delivery of ES improves the efficacy and potency of the antitumoral therapy. The TheraCyte system is a polytetrafluoroethylene (PTFE) semipermeable membrane macroencapsulation system for implantation of genetically engineered cells specially designed for the in vivo delivery of therapeutic proteins, such as ES, which circumvents the problem of limited half-life and variation in circulating levels. In order to enable neovascularization at the tissues adjacent to the devices prior to ES secretion by the cells inside them, we designed a scheme in which empty TheraCyte devices were preimplanted SC into immunodeficient mice. Only after healing (17 days later) were Chinese hamster ovary cells expressing ES injected into the preimplanted devices. In another model for device implantation, the cells expressing ES where loaded into the immunoisolation devices prior to implantation into the animals, and the TheraCyte were then immediately implanted SC into the mice. Throughout the 2-month study, constant high ES levels of up to 3.7 microg/ml were detected in the plasma of the mice preimplanted with the devices, while lower but also constant levels of ES (up to 2.1 microg/ml plasma) were detected in the mice that had received devices preloaded with the ES-expressing cells. Immunohistochemistry using anti-ES antibody showed reaction within the device and outside it, demonstrating that ES, secreted by the confined recombinant cells, permeated through the membrane and reached the surrounding tissues.

Treatment of diabetic rats with encapsulated islets

Immunoprotection of islets using bioisolator systems permits introduction of allogeneic cells to diabetic patients without the need for immunosuppression. Using TheraCyte™ immunoisolation devices, we investigated two rat models of type 1 diabetes mellitus (T1DM), BB rats and rats made diabetic by streptozotocin (STZ) treatment. We chose to implant islets after the onset of diabetes to mimic the probable treatment of children with T1DM as they are usually diagnosed after disease onset. We encapsulated 1000 rat islets and implanted them subcutaneously (SQ) into diabetic biobreeding (BB) rats and STZ-induced diabetic rats, defined as two or more consecutive days of blood glucose >350 mg/dl. Rats were monitored for weight and blood glucose. Untreated BB rats rapidly lost weight and were euthanized at >20% weight loss that occurred between 4 and 10 days from implantation. For period of 30–40 days following islet implantation weights of treated rats remained steady or increased. Rapid weight loss occurred after surgical removal of devices that contained insulin positive islets. STZ-treated rats that received encapsulated islets showed steady weight gain for up to 130 days, whereas untreated control rats showed steady weight loss that achieved >20% at around 55 days. Although islet implants did not normalize blood glucose, treated rats were apparently healthy and groomed normally. Autologous or allogeneic islets were equally effective in providing treatment. TheraCyte™ devices can sustain islets, protect allogeneic cells from immune attack and provide treatment for diabetic-mediated weight loss in both BB rats and STZ-induced diabetic rats.

Soluble factor(s) from bone marrow cells can rescue lethally irradiated mice by protecting endogenous hematopoietic stem cells

OBJECTIVE

Ionizing radiation-induced myeloablation can be rescued via bone marrow transplantation (BMT) or administration of cytokines if given within 2 hours after radiation exposure. There is no evidence for the existence of soluble factors that can rescue an animal after a lethal dose of radiation when administered several hours postradiation. We established a system that could test the possibility for the existence of soluble factors that could be used more than 2 hours postirradiation to rescue animals.

MATERIALS AND METHODS

Animals with an implanted TheraCyte immunoisolation device (TID) received lethal-dose radiation and then normal bone marrow Lin- cells were loaded into the device (thereby preventing direct interaction between donor and recipient cells). Animal survival was evaluated and stem cell activity was tested with secondary bone marrow transplantation and flow cytometry analysis. Donor cell gene expression of five antiapoptotic cytokines was examined.

RESULTS

Bone marrow Lin- cells rescued lethally irradiated animals via soluble factor(s). Bone marrow cells from the rescued animals can rescue and repopulate secondary lethally irradiated animals. Within the first 6 hours post-lethal-dose radiation, there is no significant change of gene expression of the known radioprotective factors TPO, SCF, IL-3, Flt-3 ligand, and SDF-1.

CONCLUSION

Hematopoietic stem cells can be protected in lethally irradiated animals by soluble factors produced by bone marrow Lin- cells.

Cellular vehicles for cancer gene therapy: current status and future potential

Cancer is a difficult target for any therapeutic strategy; therefore, there is a continuous search for new therapeutic modalities, for application either alone or in combination. In this regard, gene-based therapy is a new approach that offers hope of improved control of tumors. Intensive research to apply gene therapy for cancer treatment has led to identification of the most important technical and theoretical barriers that need to be overcome for clinical success. One of the central unresolved challenges remains the issue of specific and efficient delivery of genes to target cells or tissues, emphasizing the importance of the gene carrier. Along with different viral and non-viral vector systems, mammalian cells have also been considered as vehicles for delivery of anti-cancer therapeutics. The cell-based delivery approach was introduced as the first attempt to apply gene therapy to cancer treatment, and in general, has followed most of the ups and downs of gene therapy applications, progressing alongside new knowledge gained in this field. As a result, significant progress has been made in some aspects of the cell-based approach, while the development of other essential issues is only just gaining speed. It appears that the initial phase of development of cell-based protocols - the achievement of efficient ex vivo cell loading with therapeutics - has largely been fulfilled. However, the desired efficacy of cell-based strategies in general has not yet been reached, and specificity of tumor homing needs to be improved considerably. There is hope that advances in related scientific fields will promote the utilization of cells as powerful and versatile vehicles for cancer gene therapy.

In vivo calcium deposition on polyvinyl alcohol matrix used in hollow fiber cell macroencapsulation devices

The encapsulation of genetically modified cells represents a promising approach for the delivery of therapeutic proteins. The functionality of the device is dependent on the characteristics of the biomaterials, the procedures used in its confection and the adaptability of the encapsulated cells in the host. We report conditions leading to the development of calcifications on the polyvinyl alcohol (PVA) matrix introduced in hollow fiber devices for the encapsulation of primary human fibroblasts implanted in mice. The manufacturing procedures, batches of PVA matrix and cell lineages were assessed for their respective role in the development of the phenomenon. The results showed that the calcification is totally prevented by substituting phosphate-buffer saline with ultra-pure sterile water in the rinsing procedure of the matrix. Moreover, a positive correlation was found, when comparing two fibroblast cell lineages, between the level of lactate dehydrogenase (LDH) activity measured in the cells and the degree of calcium deposition. Higher LDH activity may decrease calcium depositions because it generates in the device a more acidic microenvironment inhibiting calcium precipitation. The present study defines optimized conditions for the encapsulation of primary human fibroblasts in order to avoid potentially detrimental calcifications and to allow long-term survival of encapsulated cells.

Long-Term Erythropoietin Gene Expression from Transduced Cells in Bioisolator Devices

Recombinant erythropoietin (EPO) is widely administered for long-term treatment of anemia associated with renal failure and other chronic diseases. The ability to deliver EPO by gene therapy would have clinical and economic benefit. We compared autologous and allogeneic transduced primary vascular smooth muscle cells for their ability to provide sustained EPO gene expression when encapsulated in TheraCyte devices implanted subcutaneously (SQ) or intraperitoneally (IP) in rats. Cells were transduced with retrovirus vector LrEpSN encoding rat EPO cDNA. Rats that received either autologous or allogeneic transduced cells showed elevated hematocrits (HCTs) ranging from 50 to 79% that were sustained for more than 12 months. The HCT of control rats remained at baseline (45.8%). Rats that received second SQ implants of either autologous or allogeneic cells showed elevations in hematocrit that were sustained for up to 12 months, suggesting the absence of immunological responses to transduced cells or implant material. All experimental groups had statistically significant elevated HCT (p < 0.001) when compared with controls. Both SQ and IP implantation were equally effective in delivering EPO long term. There were no significant differences in white blood cell (WBC) or platelet (PLT) values between treated and control animals. Implantation of TheraCyte devices was well tolerated and histological evaluation of the devices up to 12 months after surgery revealed a high degree of vascularization and no evidence of host immune response. TheraCyte devices offer a simple and safe gene delivery system that provides sustained therapeutic gene expression, permit removal and implantation of new devices, and do not require immunosuppression of the host.

Optimization of human erythropoietin secretion from MLV-infected human primary fibroblasts used for encapsulated cell therapy

BACKGROUND

The transplantation of encapsulated cells genetically engineered to secrete human erythropoietin (hEpo) represents an alternative to repeated injections of the recombinant hormone for the treatment of Epo-responsive anemia. In the present study, the ability of primary human foreskin fibroblasts to secrete high levels of hEpo and the importance of cis-acting elements and infection conditions on transgene expression level were assessed.

METHODS

The transduction efficiency was first evaluated with beta-galactosidase (LacZ)-encoding retroviral vectors derived from the murine leukemia retrovirus (MLV) pseudotyped either with an amphotropic envelope or with the G glycoprotein of vesicular stomatitis virus (VSV-G). Human fibroblasts were then infected with an amphotropic hEpo-expressing retroviral vector, which was modified by insertion of a post-transcriptional regulatory element from the woodchuck hepatitis virus (WPRE) and a Kozak consensus sequence (KZ). Human Epo production was further optimized by increasing the multiplicity of infection and by selecting high producer cells. The survival and the transgene expression of these fibroblasts were finally evaluated in vivo. The cells were encapsulated into microporous hollow fibers and subcutaneously implanted in nude mice.

RESULTS

A secretion level of approximately 5 IU hEpo/10(6) cells/day was obtained with the basal vector. A 7.5-fold increase in transgene expression was observed with the insertion of WPRE and KZ elements. Finally, according to the optimization of infection conditions, we obtained a 40-fold increase in hEpo secretion, reaching approximately 200 IU hEpo/10(6) cells/day. The in vivo experiments showed an increase in the hematocrit during the first 2 weeks and elevated levels exceeding 60% were maintained over a 6-week period.

CONCLUSIONS

These results indicate that primary human fibroblasts represent a promising source for encapsulated cell therapy.

Fibroblasts and dermal gene therapy: a minireview

This review highlights our current understanding of the biology of, survival of, and transgene expression by genetically modified fibroblasts (GMFb) carrying stably integrated transgenes in vivo. Experimental data demonstrate that three elements will enhance expression by and survival of GMFb in vivo: a matrix scaffolding to take the place of the existing dermis, the presence of elements of the extracellular matrix in the construct used to move GMFb to the in vivo setting, and the utilization of immortalized fibroblasts to carry the transgenes. Although moving GMFb to an in vivo setting is an invasive procedure, there are a number of clinical settings where GMFb appear to be the suitable cell for gene therapy.

Sustained systemic delivery of monoclonal antibodies by genetically modified skin fibroblasts

In vivo production and systemic delivery of therapeutic antibodies by engineered cells might advantageously replace injection of purified antibodies for treating a variety of life-threatening diseases, including cancer, acquired immunodeficiency syndrome, and autoimmune diseases. We report here that skin fibroblasts retrovirally transduced to express immunoglobulin genes can be used for sustained long-term systemic delivery of cloned antibodies in immunocompetent mice. Importantly, no anti- idiotypic response against the ectopically expressed model antibody used in this study was observed. This supports the notion that skin fibroblasts can potentially be used in antibody-based gene/cell therapy protocols without inducing any adverse immune response in treated individuals.

Cell transplantation for endocrine disorders

Current hormonal replacement therapy for endocrine disorders cannot, unfortunately, reproduce the complex metabolic interactions of hormones. The organ or cell transplantation would be a more physiological approach to the treatment of endocrine disorders. For decades, remarkable progress in organ or cell transplantation in endocrine disorders has been made, especially in recent years. But there are many limitations in the widespread application of allotransplantation because of rejection. Various methods of immunomanipulations designed to overcome rejection have been proposed, which include immunosuppression, immunomodulation and immunoisolation. The transplantation of immunoisolated cells and some clinical results of the transplants were reviewed. Also a perspective for future directions on endocrine cell transplantation was provided in this review. Human islet cell transplantation for the cure of diabetes was emphasized in this chapter and other cell transplantation for endocrine disorders was also discussed briefly, including parathyroid tissue transplantation, bioartificial thyroid transplantation and adrenal cell transplantation.

Delivery of recombinant product from subcutaneous implants of encapsulated recombinant cells in canines

Delivering recombinant therapeutic proteins from a universal microencapsulated cell line is an alternate method for gene therapy. It has proved effective in the treatment of several murine models of human genetic diseases. However, in scaling up to large animal models, intraperitoneal Implantations of these microcapsules in canines were associated with excessive Inflammatory response and rapid degradation. We now show that subcutaneous implantation of microencapsulated cells in canines is effective in delivering recombinant product systemically for extended periods, provides a surgically benign site, leads to less inflammatory response, and permits longer-term survival of microcapsules. Allogeneic MDCK cells engineered to secrete human growth hormone (hGH) were microencapsulated in alginate-poly-L-lysine-alginate and implanted subcutaneously. Systemic delivery of hGH was evident within 4 hours and peaked by day 1 after implantation in all dogs. The gradual decline of hGH in the circulation in the first 2 weeks coincided with the development of anti-hGH antibodies by day 11. The high titer persisted for more than 1 month, demonstrating indirectly the persistent delivery of hGH. Microcapsules retrieved from the subcutaneous implant maintained their structure throughout the experiment and were free of host cellular adhesions. The mechanical integrity of the subcutaneously implanted microcapsules also appeared superior to that of the intraperitoneal implant. Hence the subcutaneously implanted microcapsules required minimal surgical intervention and led to a low level of inflammatory response, and the implant survived for at least 1 month, thus demonstrating the feasibility of systemic delivery of recombinant products via subcutaneous implantation in large animals.

In situ electrochemical oxygen generation with an immunoisolation device

The viability and function of transplanted tissue encapsulated in immunobarrier devices is subject to oxygen transport limitation. In this study, we have designed and used an in situ electrochemical oxygen generator which decomposes water electrolyticaly to provide oxygen to the adjacent planer immunobarrier diffusion chamber. The rate of oxygen generation, which increases linearly with electrical current, was accurately controlled. A theoretical model of oxygen diffusion was also developed and was used to calculate the oxygen profiles in some of the experimental systems. In vitro culture experiments were carried out with beta TC3 cells encapsulated in titanium ring devices. The growth and viability of cells with or without in situ oxygen generation was studied. We found that under otherwise similar culturing conditions, the thickness of the cell layer and the viability of cells was the highest in devices cultured in stirred media with oxygen generation, even though the thickness had not reached the theoretically predicted value, and lowest in those unstirred and without oxygen generation.