Encapsulated engineered myoblasts can cure Hurler syndrome: preclinical experiments in the mouse model

Transplantable cell-encapsulation device using a semipermeable ethylene-vinyl alcohol copolymer membrane in a mouse diabetic model

Cell-based therapy is an attractive approach, and encapsulation of therapeutic cells is a promising strategy because it prevents immune responses and allows transplanted cells to be retrieved in case of dysfunction. Bioartificial pancreas, in which insulin-secreting cells are encapsulated in a semipermeable membrane bag, is a new class of medical device for treating type-I diabetes. In this study, we developed a macroencapsulation device in which the pancreatic beta cell line MIN6 was encapsulated in a semipermeable bag made of an ethylene-vinyl alcohol copolymer membrane. In vitro evaluation of ATP and insulin levels revealed that MIN6 cells grown in Matrigel within the device secreted insulin in response to glucose levels. Transplantation of the device lowered blood glucose levels for 30 days in diabetic mice. Histological observation revealed that MIN6 cells formed spheroids in Matrigel, and no host cells were detected within the device. Blood levels of inflammatory cytokines in the transplanted mice were similar to those in non-transplanted mice, and antibody levels in the device were lower than those in the intraperitoneal fluid. These results suggest that the semipermeable ethylene-vinyl alcohol copolymer membrane developed in this study is useful for cell encapsulation in cell-based therapies, including beta-cell macroencapsulation for type-1 diabetes.

Drosophila D-idua Reduction Mimics Mucopolysaccharidosis Type I Disease-Related Phenotypes

Deficit of the IDUA (α-L-iduronidase) enzyme causes the lysosomal storage disorder mucopolysaccharidosis type I (MPS I), a rare pediatric neurometabolic disease, due to pathological variants in the IDUA gene and is characterized by the accumulation of the undegraded mucopolysaccharides heparan sulfate and dermatan sulfate into lysosomes, with secondary cellular consequences that are still mostly unclarified. Here, we report a new fruit fly RNAi-mediated knockdown model of a IDUA homolog (D-idua) displaying a phenotype mimicking some typical molecular features of Lysosomal Storage Disorders (LSD). In this study, we showed that D-idua is a vital gene in Drosophila and that ubiquitous reduction of its expression leads to lethality during the pupal stage, when the precise degradation/synthesis of macromolecules, together with a functional autophagic pathway, are indispensable for the correct development to the adult stage. Tissue-specific analysis of the D-idua model showed an increase in the number and size of lysosomes in the brain and muscle. Moreover, the incorrect acidification of lysosomes led to dysfunctional lysosome-autophagosome fusion and the consequent block of autophagy flux. A concomitant metabolic drift of glycolysis and lipogenesis pathways was observed. After starvation, D-idua larvae showed a quite complete rescue of both autophagy/lysosome phenotypes and metabolic alterations. Metabolism and autophagy are strictly interconnected vital processes that contribute to maintain homeostatic control of energy balance, and little is known about this regulation in LSDs. Our results provide new starting points for future investigations on the disease’s pathogenic mechanisms and possible pharmacological manipulations.

Pre-clinical Mouse Models of Neurodegenerative Lysosomal Storage Diseases

There are over 50 lysosomal hydrolase deficiencies, many of which cause neurodegeneration, cognitive decline and death. In recent years, a number of broad innovative therapies have been proposed and investigated for lysosomal storage diseases (LSDs), such as enzyme replacement, substrate reduction, pharmacologic chaperones, stem cell transplantation, and various forms of gene therapy. Murine models that accurately reflect the phenotypes observed in human LSDs are critical for the development, assessment and implementation of novel translational therapies. The goal of this review is to summarize the neurodegenerative murine LSD models available that recapitulate human disease, and the pre-clinical studies previously conducted. We also describe some limitations and difficulties in working with mouse models of neurodegenerative LSDs.

Cell Encapsulation Within Alginate Microcapsules: Immunological Challenges and Outlook

Cell encapsulation is a bioengineering technology that provides live allogeneic or xenogeneic cells packaged in a semipermeable immune-isolating membrane for therapeutic applications. The concept of cell encapsulation was first proposed almost nine decades ago, however, and despite its potential, the technology has yet to deliver its promise. The few clinical trials based on cell encapsulation have not led to any licensed therapies. Progress in the field has been slow, in part due to the complexity of the technology, but also because of the difficulties encountered when trying to prevent the immune responses generated by the various microcapsule components, namely the polymer, the encapsulated cells, the therapeutic transgenes and the DNA vectors used to genetically engineer encapsulated cells. While the immune responses induced by polymers such as alginate can be minimized using highly purified materials, the need to cope with the immunogenicity of encapsulated cells is increasingly seen as key in preventing the immune rejection of microcapsules. The encapsulated cells are recognized by the host immune cells through a bidirectional exchange of immune mediators, which induce both the adaptive and innate immune responses against the engrafted capsules. The potential strategies to cope with the immunogenicity of encapsulated cells include the selective diffusion restriction of immune mediators through capsule pores and more recently inclusion in microcapsules of immune modulators such as CXCL12. Combining these strategies with the use of well-characterized cell lines harboring the immunomodulatory properties of stem cells should encourage the incorporation of cell encapsulation technology in state-of-the-art drug development.

Cell encapsulation: Overcoming barriers in cell transplantation in diabetes and beyond

Cell-based therapy is emerging as a promising strategy for treating a wide range of human diseases, such as diabetes, blood disorders, acute liver failure, spinal cord injury, and several types of cancer. Pancreatic islets, blood cells, hepatocytes, and stem cells are among the many cell types currently used for this strategy. The encapsulation of these "therapeutic" cells is under intense investigation to not only prevent immune rejection but also provide a controlled and supportive environment so they can function effectively. Some of the advanced encapsulation systems provide active agents to the cells and enable a complete retrieval of the graft in the case of an adverse body reaction. Here, we review various encapsulation strategies developed in academic and industrial settings, including the state-of-the-art technologies in advanced preclinical phases as well as those undergoing clinical trials, and assess their advantages and challenges. We also emphasize the importance of stimulus-responsive encapsulated cell systems that provide a "smart and live" therapeutic delivery to overcome barriers in cell transplantation as well as their use in patients.

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.

Effect of plasma components on the stability and permeability of microcapsule

Immobilization of hepatocytes in microcapsules has been a potentially alternative methodology for bioartificial livers (BALs). Moreover, the stability and permeability are the key parameters of these microcapsules. However, these alginate-based microcapsules are unstable if the surrounding medium disrupts the ionic interactions between alginate and the polycation. As hundreds of components are included in human plasma, the stability and permeability in plasma of microcapsules need to be sufficiently investigated. In the present study, the stability of three kinds of alginate-based microcapsules was evaluated when they were immersed in plasma. Our results showed that stability of alginate-α-poly (L-lysine)-alginate (α-APA) microcapsules was well maintained, better than those of alginate-ε-poly (L-lysine)-alginate (ε-APA) and alginate-chitosan-alginate (ACA) microcapsules. Also, factors affecting the stability of microcapsules in plasma were analyzed and it showed that heparin was the key factor that affected the stability of α-APA microcapsules, whereas heparin and low molecular electrolytes such as HCO3(-) and H2 PO4(-)/HPO4(2-) were the factors to ε-APA and ACA microcapsules. In addition, the permeability evaluation showed no decrease in permeability of microcapsules after incubation in plasma. Our study might provide a foundation for the selection and modification of materials for microcapsule-based BAL devices.

Mucopolysacccharidoses: From understanding to treatment, a century of discoveries

After the first description of a patient recognized as a MPS case was made in 1917, several similar cases were described and identified. Observations reported in the middle of the twentieth century concerning the presence of acid mucopolysaccharides (later called glycosaminoglycans, or GAGs) in tissues and especially in urine of patients were instrumental in providing an identity for these diseases, which became referred as "mucopolysaccharidoses" (MPS). In the late 1960's it was demonstrated that MPS were caused by defects in the breakdown of GAGs, and the specific enzyme deficiencies for the 11 types and subtypes of MPS were identified thereafter. Genes involved in the MPS were subsequently identified, and a large number of disease-causing mutations were identified in each one. Although individually rare, MPS are relatively frequent as a group, with an overall incidence estimated as 1:22,000. The increased excretion of urinary GAGs observed in the vast majority of MPS patients provides a simple screening method, the diagnosis usually being confirmed by the identification of the specific enzyme deficiency. Molecular analysis also plays a role, being helpful for phenotype prediction, prenatal diagnosis and especially for the identification of carriers. As the diseases are rare and diagnosis requires sophisticated methods, the establishment of reference laboratories for MPS identification is recommended. The successful experience of the MPS Brazil Network in providing access to information and diagnosis may be considered as an option for developing countries. The development of therapeutic strategies for MPS, including bone marrow/hematopoietic stem cell transplantation (BMT/HSCT) and enzyme replacement therapy (ERT), changed the natural history of many MPS types. However, some challenges still remain, including the prevention of cognitive decline which occurs in some MPS. Newer approaches, such as intratechal ERT, substrate reduction therapy, read-through, gene therapy and encapsulated modified cells may provide a better outcome for these diseases in the near future. As early diagnosis and early treatment seems to improve treatment outcomes, and as newborn screening is now technically feasible, pilot programs (including one in progress in an area with high-incidence of MPS VI in northeastern Brazil) should provide information about its potential impact in reducing the morbidity associated with MPS diseases.