Single and double encapsulation of cell and cell clusters for regenerative medicine and cell transplantation

Abstract

Problem Conventional alginate microencapsulation has been tested in pre-clinical animal models, including non-human primates (NHPs) and in humans with unsatisfactory results. This is likely because of the large (600-1000\u3bcm) diameter of standard microcapsules that impairs oxygen and nutrients exchange and causes delays in secretion of trophic factors following cell stimulation by the host; and limited choice for transplantation sites due to the high total volume of the encapsulation product; finally long-term applications might fail due to the poor mechanical properties and poor in vivo stability of conventional encapsulation materials. Background Successful encapsulation of autologous, allogeneic or xenogeneic cells with a semipermeable barrier can be beneficial for many therapeutic applications, including improving preservation and shipment of coated cells and guaranteeing immunoprotection after transplantation for regenerative medicine. Especially in cell transplantation for treatment of autoimmune diseases, including type-1 diabetes, immunoisolating properties of capsules might allow transplantation in absence of or with reduced systemic immunosuppression. Hypothesis We hypothesize that by developing novel encapsulation technologies that address most concerns associated with conventional cell microencapsulation we can turn cell encapsulation into an effective and safe therapy and that by designing the procedure to be versatile, reproducible, and scalable we can facilitate its translatability to clinical applications. Research As an alternative to conventional alginate microencapsulation, we developed two novel encapsulation technologies: a \u201cconformal coating\u201d microencapsulation and a \u201cdouble conformal coating\u201d encapsulation and compared to alginate micrencapsulation. Conformal coating is achieved by exploiting a fluid dynamic principle that allows to wrap cell clusters with a 10-20\u3bcm layer of polymer, minimizing diffusion barriers and size of encapsulated cell product and allowing a wider choice of transplantation sites. The double coating technology confers a conformal coating as an extra layer to improve mechanical, permselectivity and immunoisolating properties of enclosed alginate microcapsules (400-600\u3bcm in diameter) that are obtained with a conventional micro droplet generator. Our combined encapsulation methods are versatile because they can be applied to any coating materials and to any cell type and are reproducible and scalable for clinical translation. Observations We have shown that both the conformal coating and alginate microencapsulation technologies do not to affect cell viability and function (i.e. secretion of trophic factor upon stimulation) of cell clusters of different origins and we are currently optimizing the double coating technology by combining the two encapsulation methods. We strongly believe that our platform for cell encapsulation will allow us to compare different encapsulation technology and tailor them for different therapeutic applications as a valid and may be superior alternative to standard alginate microencapsulatio