Delivery of recombinant gene product to canine brain with the use of microencapsulation

Responses of Free Radicals to Subcutaneous Implantation of Alginate-Chitosan-Alginate (ACA) Microcapsules in Mice

The objective of this study was to characterize the levels of free radicals in serum and antioxidase activity after microcapsules were implanted into the subcutaneous space of mice. Cell viability was evaluated using AO/EB staining. Serum free radicals, malondialdehyde and superoxide dismutase levels were evaluated by colorimetry analysis. The mice were divided into three groups: saline injection group (n=15), empty microcapsules injected group (n=21), encapsulated cells injected group (n=21). Cell viability and serum analysis were executed at 1, 4 and 7 days post-implantation. Hydrogen peroxide and malondialdehyde levels initially increased in the recipients of the empty microcapsules, before decreasing to the basal level. However, in mice receiving the encapsulated cells, the levels were higher at the end of study. Nitric oxide and superoxide dismutase increased after the implantation of microcapsules with or without the BHK-21 cells, but were not changed in response to the saline injection. The viability of the encapsulated cells was high in vivo, although some microcapsules had broken by 7 days post-implantation. These results suggest that nitric oxide plays a role in the specific response to microcapsules. The levels of free radicals rapidly increased immediately following microcapsule transplantation, but they caused only slight cellular damage before the microencapsulated cells were exposed.

Optimization of alginate microcapsules containing cells overexpressing α-l-iduronidase using Box-Behnken design

Mucopolysaccharidosis type I (MPS I) is an autosomal recessive disease caused by deficiency of α-l-iduronidase (IDUA), which results in the lysosomal accumulation of glycosaminoglycans (GAG) leading to widespread clinical manifestations. The microencapsulation of IDUA overexpressing recombinant cells has been considered as a promising strategy for the treatment of MPS I. This study aimed at the optimization of alginate microcapsules containing recombinant BHK (Baby Hamster Kidney) cells (rBHK) overexpressing IDUA produced by electrostatic extrusion technique. The alginate microcapsule (MC-A) optimization study was carried out by means of an experimental Box-Behnken Design that allowed the simultaneous evaluation of the influence of voltage (kV), alginate/cell suspension flow (mL/h), and alginate concentration (%) on size and IDUA activity. The optimal conditions of voltage (10kV), flow (25mL/h), and alginate concentration (1.3%) made possible to obtain the smallest microcapsules showing the highest IDUA activity. After optimization, the microcapsules were sequentially coated with PLL and alginate (MC-APA) to increase their stability. MC-A and MC-APA presented monodisperse populations (span<1.22) with an average diameter of less than 350μm. The coating increased the mechanical stability of MC-APA by about 6-fold and modulated the permeability to the enzyme. Surface analyzes of MC-APA showed the presence of PLL bands, suggesting that the last alginate layer appears to have only partially coated the PLL. After 30days of subcutaneous implantation of the MC-APA microcapsules containing rBHK cells in a MPS I murine model, a significant increase in IDUA activity was observed in the skin near the implant. Histological analysis revealed an inflammatory infiltrate at the application site, which did not prevent the release of the enzyme under the conditions evaluated. Taken together, the overall results demonstrate the feasibility of MC-APA as a potential alternative for local treatment of MPS I.

Subcutaneous implantation of microencapsulated cells overexpressing α-L-iduronidase for mucopolysaccharidosis type I treatment

Mucopolysaccharidosis type I (MPS I) is caused by a deficiency of α-L-iduronidase (IDUA), resulting in accumulation of glycosaminoglycans (GAG) in lysosomes. Microencapsulation of recombinant cells is a promising gene/cell therapy approach that could overcome the limitations of the current available treatments. In the present study we produced alginate-poly-L-lysine-alginate (APA) microcapsules containing recombinant cells overexpressing IDUA, which were implanted in the subcutaneous space of MPS I mice in order to evaluate their potential effect as a treatment for this disease. APA microcapsules enclosing genetically modified Baby Hamster Kidney cells overexpressing IDUA were produced and implanted in the subcutaneous space of 4-month-old MPS I mice (Idua ^-/-). Treatment was performed using two cell concentrations: 8.3 × 10⁷ and 8.3 × 10⁶ cells/mL. Untreated MPS I and normal mice were used as controls. Microcapsules were retrieved and analyzed after treatment. Increased IDUA in the liver, kidney and heart was detected 24 h postimplantation. After 120 days, higher IDUA activity was detected in the liver, kidney and heart, in both groups, whereas GAG accumulation was reduced only in the high cell concentration group. Microcapsules analysis showed blood vessels around them, as well as inflammatory cells and a fibrotic layer. Microencapsulated cells were able to ameliorate some aspects of the disease, indicating their potential as a treatment. To achieve better performance of the microcapsules, improvements such as the modulation of inflammatory response are suggested.

Transplantation of alginate-encapsulated seminiferous tubules and interstitial tissue into adult rats: Leydig stem cell differentiation in vivo?

In vivo and in vitro studies were conducted to determine whether testosterone-producing Leydig cells are able to develop from cells associated with rat seminiferous tubules, interstitium, or both. Adult rat seminiferous tubules and interstitium were isolated, encapsulated separately in alginate, and implanted subcutaneously into castrated rats. With implanted tubules, serum testosterone increased through two months. Tubules removed from the implanted rats and incubated with LH produced testosterone, and cells on the tubule surfaces expressed steroidogenic enzymes. With implanted interstitial tissue, serum levels of testosterone remained undetectable. However, co-culture of interstitium plus tubules in vitro resulted in the formation of Leydig cells by both compartments. These results indicate that seminiferous tubules contain both cellular and paracrine factors necessary for the differentiation of Leydig cells, and that the interstitial compartment contains precursor cells capable of forming testosterone-producing Leydig cells but requires stimulation by paracrine factors from the seminiferous tubules to do so.

Factors influencing the use and interpretation of animal models in the development of parenteral drug delivery systems

Depending upon the drug and drug delivery platform, species-specific physiological differences can lead to errors in the interspecies extrapolation of drug performance. This manuscript provides an overview of the species-specific physiological variables that can influence the performance of parenteral dosage forms such as in situ forming delivery systems, nanoparticles, microspheres, liposomes, targeted delivery systems, lipophilic solutions, and aqueous suspensions. Also discussed are those factors that can influence the partitioning of therapeutic compounds into tumors, the central nervous system and the lymphatics. Understanding interspecies differences in the movement and absorption of molecules is important to the interpretation of data generated through the use of animal models when studying parenteral drug delivery.

Cell microencapsulation: a potential tool for the treatment of neuronopathic lysosomal storage diseases

Lysosomal storage disorders (LSD) are monogenic diseases caused by the deficiency of different lysosomal enzymes that degrade complex substrates such as glycosaminoglycans, sphingolipids, and others. As a consequence there is multisystemic storage of these substrates. Most treatments for these disorders are based in the fact that most of these enzymes are soluble and can be internalized by adjacent cells via mannose-6-phosphate receptor. In that sense, these disorders are good candidates to be treated by somatic gene therapy based on cell microencapsulation. Here, we review the existing data about this approach focused on the LSD treatments, the advantages and limitations faced by these studies.

Effects of cryopreservation and hypothermic storage on cell viability and enzyme activity in recombinant encapsulated cells overexpressing alpha-L-iduronidase

Here, we show the effects of cryopreservation and hypothermic storage upon cell viability and enzyme release in alginate beads containing baby hamster kidney cells overexpressing alpha-L-iduronidase (IDUA), the enzyme deficient in mucopolysaccharidosis type I. In addition, we compared two different concentrations of alginate gel (1% and 1.5%) in respect to enzyme release from the beads and their shape and integrity. Our results indicate that in both alginate concentrations, the enzyme is released in lower amounts compared with nonencapsulated cells. Alginate 1% beads presented increased levels of IDUA release, although this group presented more deformities when compared with alginate 1.5% beads. Importantly, both encapsulated groups presented higher cell viability after long cryopreservation period and hypothermic storage. In addition, alginate 1.5% beads presented higher enzyme release after freezing protocols. Taken together, our findings suggest a benefic effect of alginate upon cell viability and functionality. These results may have important application for treatment of both genetic and nongenetic diseases using microencapsulation-based artificial organs.

Gene therapy for lysosomal storage diseases (LSDs) in large animal models

Lysosomal storage diseases (LSDs) are inherited metabolic disorders caused by deficient activity of a single lysosomal enzyme or other defects resulting in deficient catabolism of large substrates in lysosomes. There are more than 40 forms of inherited LSDs known to occur in humans, with an aggregate incidence estimated at 1 in 7,000 live births. Clinical signs result from the inability of lysosomes to degrade large substrates; because most lysosomal enzymes are ubiquitously expressed, a deficiency in a single enzyme can affect multiple organ systems. Thus LSDs are associated with high morbidity and mortality and represent a significant burden on patients, their families, the health care system, and society. Because lysosomal enzymes are trafficked by a mannose 6-phosphate receptor mechanism, normal enzyme provided to deficient cells can be localized to the lysosome to reduce and prevent storage. However, many LSDs remain untreatable, and gene therapy holds the promise for effective therapy. Other therapies for some LSDs do exist, or are under evaluation, including heterologous bone marrow or cord blood transplantation (BMT), enzyme replacement therapy (ERT), and substrate reduction therapy (SRT), but these treatments are associated with significant concerns, including high morbidity and mortality (BMT), limited positive outcomes (BMT), incomplete response to therapy (BMT, ERT, and SRT), life-long therapy (ERT, SRT), and cost (BMT, ERT, SRT). Gene therapy represents a potential alternative, albeit with its own attendant concerns, including levels and persistence of expression and insertional mutagenesis resulting in neoplasia. Naturally occurring animal homologues of LSDs have been described in all common domestic animals (and in some that are less common) and these animal models play a critical role in evaluating the efficacy and safety of therapy.

Submerged electrosprays: A versatile approach for microencapsulation

The unearthing of fundamental science and technology associated with microencapsulation is an ongoing exciting scientific endeavour focused on by several scientists. Encapsulated structures (containing either a gas, molecules or materials) previously have been shown as having widespread applications across the physical and life sciences. In particular, such methodologies used for forming encapsulations in medical-related studies have shown great promise from diagnostics and imaging, to gene therapy and drug delivery which are only a few amongst several other applications. At present there are numerous 'jet-based' manifestations available for microencapsulation, these primarily root from either capillary or channel-based techniques. The driving mechanisms employed in these approaches exploit aerodynamic/pressure gradients to piezoelectricity. In this paper submerged electrosprays a multipurpose electric field driven jet-based technique is explored for forming near mono-dispersed encapsulations sized in the micrometer range. Our studies elucidate the ability to form microencapsulations containing either a gas or a micro/nanoparticulate-based material suspension as capsules sized in the ranges approximately 65-80 microm, approximately 8-25 microm to approximately 3-14 microm, respectively. We believe this technique can significantly contribute to the microencapsulation field of research based on both the size of the generated encapsulations to the containment of immiscible high viscosity particulate-based suspensions. Furthermore our investigations show the ability to control the production of these encapsulations in terms of both their size and rate of generation with ease; hence demonstrating this electrospray-assisted microencapsulation route as having a wide range of applications. It should be noted that in its present form this technique could be explored for generating emulsions with a variety of materials especially with living organisms for applications in the clinical and biomedical areas of research.

Novel candidate disease for gene therapy: metachromatic leukodystrophy

Metachromatic leukodystrophy (MLD) is a rare, fatal, inherited, autosomal recessive, lysosomal storage disorder, characterized by severe and progressive demyelination affecting the central and peripheral nervous systems. Despite some initial expectations in hematopoietic stem cell transplantation, and despite the ameliorated supportive therapy, MLD remains a life-threatening disease, with an extremely poor quality of life and a severe prognosis for all affected patients. Prospectively, in children affected by MLD, who have no other therapeutic option and an extremely poor prognosis, the potential risks associated with the use of a novel technology, such as gene therapy, might be well balanced by the potential benefit of a positive outcome. Thus, MLD might be considered an optimal candidate disease for testing innovative and potentially efficacious therapeutic approaches. Some of the gene therapy approaches discussed here, such as hematopoietic stem cells gene therapy, are likely to enter clinical testing in the near future.

Tumor Anti-angiogenic Gene Therapy with Microencapsulated Recombinant CHO Cells

Microencapsulation of recombinant cells is a novel promising approach to tumor therapy in which therapeutic protein is sustainable and long-term delivered by microencapsulated cells. The semi-permeable membrane of microcapsule can protect cell from host's immune rejection, increase the chemical stability of therapeutic protein and circumvent the problems of toxicity, limited half-lives and variation in circulating levels. Endostatin, a potent and specific angiogenesis inhibitor, could suppress the growth of primary and metastatic lesions in multiple murine tumor models. In this paper, APA microcapsules with high strength kept intact over 35 days and recombinant CHO cells kept the rapid proliferation viability and the continuous endostatin-expression function. The study of tumor treatment showed that the implantation of microencapsulated recombinant CHO cells decreased the neovascularization of tumor tissue by 59.4% and inhibited the B16 melanoma growth by 77.4%. Twenty days after tumor cell injection, 80% of animals treated with microencapsulated CHO-endo cells were alive compared to only 50% of animals in either control or mock control groups. Therefore, continuous delivery of endostatin from microencapsulated recombinant cells represents a feasible approach to tumor therapy.