Microencapsulation and chondrogenic differentiation of human mesenchymal progenitor cells from subchondral bone marrow in Ca-alginate for cell injection.

The application of stem cells is a promising therapeutic approach for cartilage regeneration. For cell therapies, a biocompatible injectable carrier, which improves retention and cell distribution and enables cell differentiation, is a prerequisite. In this study, Ca-alginate microcapsules containing human subchondral cortico-spongious progenitor cells were prepared and the chondrogenic differentiation potential was verified by real-time reverse transcription-polymerase chain reaction analysis of typical chondrogenic marker genes. The results confirmed that these cells were able to differentiate along the chondrogenic lineage when encapsulated in Ca-alginate microcapsules with a mean diameter of 600-700microm and stimulated with TGF-beta3. Chondrogenic marker genes type II collagen, aggrecan and cartilage oligomeric matrix protein were induced together with type I collagen, whereas adipogenic and osteogenic marker genes showed no induction over 14 days. After 28 days, proteoglycans and type II collagen were evident histochemically and immunohistochemically. Mechanical stability as well as permeability of Ca-alginate capsules were analysed over the course of cultivation and found to be qualified for stable cell immobilization and sufficient exchange of solutes. Therefore, from the cell biology point of view, Ca-alginate, an established hydrogel scaffold material is suited for regenerative therapies of cartilage defects based on the injection of progenitor cells.

Diffusion barriers of tripartite sporopollenin microcapsules prepared from pine pollen.

Tripartite sporopollenin microcapsules prepared from pine pollen (Pinus sylvestris L. and Pinus nigra Arnold) were analysed with respect to the permeability of the different strata of the exine which surround the gametophyte and form the sacci. The sexine at the surface of the sacci is highly permeable for polymer molecules and latex particles with a diameter of up to 200 nm, whereas the nexine covering the gametophyte is impermeable for dextran molecules, with a Stokes' radius > or =4 nm (Dextran T 70), and for the tetravalent anionic dye Evans Blue (Stokes' radius = 1.3 nm). The central capsules obtained by dissolution of the sporoplasts showed strictly membrane-controlled exchange of non-electrolytes, with half-equilibration times in the range of minutes (monosaccharides, oligosaccharides) to hours (dextran molecules with Stokes' radii up to 2.5 nm). The dependence of the permeability coefficients of the nexine for non-electrolytes on Stokes' radius or molecular weight shows that the aqueous pores through the nexine are inhomogeneous with respect to their size, and that most pores are too narrow for free diffusion of sugar molecules. To explain the barrier function of the nexine for Evans Blue, it is assumed that at least the larger pores, which enable slow permeation of dextran molecules, contain negative charges.

[Exclusion chromatography for the separation of cryoprotective agents from freeze-preserved blood cells]. / Ausschlusschromatographie zur Trennung kryoprotektiver Substanzen von gefrierkonservierten Blutzellen.

A method for separating low molecular cryoprotectiva from freeze-conserved erythrocyte- and thrombocyte-concentrates by exclusion chromatography has been described. A new vesicular packing material has been used. Only 25 to 30 minutes are necessary in order to separate glycerol respectively dimethylsulphoxide (DMSO) completely from the cells. 86.5% of the erythrocytes and 75.4% of the thrombocytes were recovered after the separation process.