Cell growth and hemoglobin synthesis in murine erythroleukemic cells propagated in high density microcapsule culture

An understanding of potential and limitations of alginate/PLL microcapsules as a cell retention system for perfusion cultures

Microcapsules for high cell density culture of mammalian cells have found an increasing interest, however, the poor stability of the microcapsules and the lack of characterisation methods led to few quantitative results. Alginate-poly-L-lysine (PLL) microcapsules have been studied in detail in order to form a basis for comparison of capsules made from different polymers. Since the microcapsules can be easily retained in the bioreactor without the need for a cell separation device, high cell densities were achieved with a maximum of 4 × 10(7) cell/ml(microcapsules), corresponding to a colonisation of 5% of the internal capsule volume. Measurement of microcapsule integrity and mechanical resistance showed that alginate-PLL microcapsules are not suitable for perfusion cultures since they are very sensitive to media composition, mainly the presence of non-gelling ions that have a higher affinity for alginate than PLL and Ca(2+), leading to the leakage of PLL and Ca(2+), and to microcapsule rupture.

Encapsulated human mesenchymal stem cells: a unique hypoimmunogenic platform for long-term cellular therapy

Cell encapsulation is a promising approach for long-term delivery of therapeutic agents. Nonetheless, this system has failed to reach clinical settings, as the entrapped cells provoke a host immune reaction. Mesenchymal stem cells (MSCs), however, potentially may overcome this impediment and serve as a promising platform for cell-based microencapsulation. They are known to be hypoimmunogenic and can be genetically modified to express a variety of therapeutic factors. We have designed alginate-PLL microcapsules that can encapsulate human MSCs (hMSCs) for extended periods, as demonstrated by fluorescence and H(3)-thymidine assays. The encapsulated hMSCs maintained their mesenchymal surface markers and differentiated to all the typical mesoderm lineages. In vitro and in vivo immunogenicity studies revealed that encapsulated hMSCs were significantly hypoimmunogenic, leading to a 3-fold decrease in cytokine expression compared to entrapped cell lines. The efficacy of such systems was demonstrated by genetically modifying the cells to express the hemopexin-like protein (PEX), an inhibitor of angiogenesis. Live imaging and tumor measurements showed that encapsulated hMSC-PEX injected adjacent to glioblastoma tumors in nude mice led to a significant reduction in tumor volume (87%) and weight (83%). We clearly demonstrate that hMSCs are the cell of choice for microencapsulation cell based-therapy, thus bringing this technology closer to clinical application.

Technology of mammalian cell encapsulation

Entrapment of mammalian cells in physical membranes has been practiced since the early 1950s when it was originally introduced as a basic research tool. The method has since been developed based on the promise of its therapeutic usefulness in tissue transplantation. Encapsulation physically isolates a cell mass from an outside environment and aims to maintain normal cellular physiology within a desired permeability barrier. Numerous encapsulation techniques have been developed over the years. These techniques are generally classified as microencapsulation (involving small spherical vehicles and conformally coated tissues) and macroencapsulation (involving larger flat-sheet and hollow-fiber membranes). This review is intended to summarize techniques of cell encapsulation as well as methods for evaluating the performance of encapsulated cells. The techniques reviewed include microencapsulation with polyelectrolyte complexation emphasizing alginate-polylysine capsules, thermoreversible gelation with agarose as a prototype system, interfacial precipitation and interfacial polymerization, as well as the technology of flat sheet and hollow fiber-based macroencapsulation. Four aspects of encapsulated cells that are critical for the success of the technology, namely the capsule permeability, mechanical properties, immune protection and biocompatibility, have been singled out and methods to evaluate these properties were summarized. Finally, speculations regarding future directions of cell encapsulation research and device development are included from the authors' perspective.

Culture of chondrocytes in alginate gel: variations in conditions of gelation influence the structure of the alginate gel, and the arrangement and morphology of proliferating chondrocytes

Sodium alginate, which gels in the presence of calcium ions, is commonly used for culture of anchorage-independent cells, such as chondrocytes. Normally, the gel appears microscopically homogeneous but, depending on the conditions of gelation, it may contain a varying number of small channels that extend inward from the surface. We have examined the influence of these channels on the morphology of cultured chondrocytes entrapped in alginate beads. Growth-plate or articular chondrocytes cultured in alginate normally proliferate and form rounded cell clusters but, in alginate beads containing numerous channels, many chondrocytes become aligned and form columns similar to those in the growth plate in vivo. As the pattern of cellular growth and morphology in alginate is profoundly influenced by the presence of channels in the gel, further studies were conducted to determine what specific conditions of gelation affect their formation. The channels are especially numerous when both the alginate and the gelling solutions lack sodium ions or other monovalent cations. The channels are cavities in the gel formed by particulate blocking of the rapid diffusion of calcium ions from the gelling solution into the boundary of the calcium alginate solution, and hence they extend inward from cells at the surface of the alginate gel. An understanding of the conditions under which these channels develop makes it possible either to avoid their formation or, alternatively, to enhance the number of channels in order to encourage proliferating cells to grow in radial columns, rather than in a less organized pattern characteristic of most culture systems.

The use of microcapsules for high density growth of human tumor infiltrating lymphocytes and other immune reactive T cells

The use of microcapsules to achieve high density growth of tumor infiltrating lymphocytes (TIL) and other antigen-specific human T cells is described. Whereas human T cells in suspension cultures usually do not exceed 1-2 x 10(6) cells/ml, densities approaching that found in living tissues (greater than 10(8) cells/ml) have been observed for microcapsule cultures. TIL and human peripheral blood-derived T cells can be routinely recovered from microcapsules with viabilities greater than or equal to 90%. The recovered cells retain their antigen reactivities and bear cell surface phenotypes identical to their counterparts grown in suspension culture. These findings suggest that microcapsule technology could prove valuable in generating the vast numbers of cells required for TIL therapy and other forms of adoptive immunotherapy with T cells.

Mass transfer effects in microencapsulated hybridoma cells producing monoclonal antibodies

Rat-mouse and mouse-mouse hybridoma cell lines were used for formation of monoclonal antibodies (MAbs) in microcapsules of different sizes. Microcapsules were made of poly L-lysine-alginate hydrogel membranes. The effects of extracapsule liquid film, intracapsule and transmembrane transfer limitations of nutrients/products on system's performance were investigated. An agitation speed of 45 rpm (4 cm/s tip speed) was found to be optimal in spinner flasks to overcome liquid film resistances around capsules. Capsule sizes need to be reduced to smaller than 350 mu in order to eliminate intracapsule transfer limitations with a typical initial viable cell concentration of 0.5 x 10(5) viable cells/mL capsule. Double coating of capsules to improve strength of capsules resulted in higher transmembrane transfer resistances.

Culture and growth characteristics of chondrocytes encapsulated in alginate beads

Methodology is described for the culture of avian and mammalian chondrocytes in ionotrophically gelled "semi-solid" and "hollow" alginate beads. Chondrocytes grown in "semi-solid" gels exhibited a spherical shape as opposed to a fibroblastic morphology observed in monolayer culture. In the "semi-solid" beads, the cells grew as small clumps and as large aggregates. The aggregates were round or elliptical in appearance and surrounded by a dense Alcian Blue positive halo. Preliminary studies with collagen and chitosan matrixes encapsulated in "hollow" beads suggest that cell growth and morphology are profoundly influenced by the composition of the cellular environment. Chondrocyte structure and function in the "semi-solid" and "hollow" beads were partially characterized by light microscopy, histochemical and biochemical means. The encapsulation methodology is readily applicable for the culture of chondrocytes in single beads, in multiwell dishes, or mass culture.