Functional polymer hydrogels for embryonic stem cell support

Embryonic stem (ES) cells are pluripotent cells with the ability to differentiate among all embryonic and adult cell lineages. Derivation of human ES cells opened up the way for treatment of many serious disorders by stem cell-based transplantation therapy. One of the most exciting challenges in development of transplantation therapies is to repair the damaged part of the organ or tissue by transplantation of undifferentiated ES cells or their differentiated derivatives within three-dimensional polymer scaffold. This method allows both renewal of structure and restoration of function of the organ. To address this issue, new polymer hydrogels were synthesized and tested. Cationic hydrogel slabs were synthesized by bulk radical copolymerization of 2-hydroxyethyl methacrylate (HEMA) and 2-(dimethylamino)ethyl methacrylate (DMAEMA) with ethylene dimethacrylate (EDMA) or 1-vinyl-2-pyrrolidone (VP) with N,N'-divinylethyleneurea (DVEU) or EDMA in the presence of saccharose or NaCl as a porogen. Swelling studies of the synthesized copolymers showed a high water content in the swollen state. Biocompatibility was studied with the use of feeder-independent mouse ES cell line D3. Cells grown either on the surface or inside synthesized polymer slabs suggest that the tested slabs are not toxic. The ability of ES cells to proliferate was only partially limited in PHEMA slabs crosslinked with EDMA compared with standard culture conditions. When cultured for a limited period of time, ES cells retained their undifferentiated state independently of properties of the hydrogel slabs, presence or absence of surface charges, type of crosslinking agent and matrix (PHEMA or PVP). Notably, prolonged culture in superporous hydrogel slabs initiated ES cell differentiation. Compared with unmodified PHEMA, the number of proliferating ES cells was still lower in the presence of cationic polymers.