Human embryonic stem cells cultured on hydrogels grafted with extracellular matrix protein-derived peptides with polyethylene glycol joint nanosegments

Material surface conjugated with fibroblast growth factor-2 for pluripotent stem cell culture and differentiation

Fibroblast growth factor-2 (FGF-2) is a critical molecule for sustaining the pluripotency of human pluripotent stem (PS) cells. However, FGF-2 is extremely unstable and cannot be stored long periods at room temperature. Therefore, the following FGF-2-conjugated cell culture materials were developed to stabilize FGF-2: FGF-2-conjugated polyvinyl alcohol (PVAI-C-FGF) hydrogels and FGF-2-conjugated carboxymethyl cellulose-coated (CMC-C-FGF) dishes. Human induced pluripotent stem (iPS) cells were proliferated on recombinant vitronectin (rVN)-coated PVAI-C-FGF hydrogels and CMC-C-FGF dishes in medium without FGF-2. Human iPS cells could not be cultivated on rVN-coated PVAI-C-FGF hydrogels for more than two passages but could proliferate on rVN-coated CMC-C-FGF dishes. These results indicated that the amount of immobilized FGF-2 and the base cell materials are important, including the amount of immobilized rVN and the conformation of FGF-2 on the surfaces. When human iPS cells were proliferated on rVN-coated CMC-C-FGF surfaces in medium containing no FGF-2 for 10 passages, their pluripotency and potential to differentiate into cells originating from three germ layers were maintained in vivo and in vitro. Furthermore, the cells could extensively differentiate into cardiomyocytes, which can be used for cardiac infarction treatment in future and retinal pigment epithelium for retinal pigmentosa treatment in future. The FGF-2-immobilized surface could enable human PS cell culture in medium that does not need to contain unstable FGF-2. The amount of FGF-2 immobilization on the rVN-coated CMC-C-5FGF and CMC-C-20FGF dishes was reduced to 93.6 and 52.2 times, respectively, which is less than the conventional amount of FGF-2 used in culture medium for one passage (6 days) of human iPS cell culture. This reduction resulted from the stabilization of unstable FGF-2 by the immobilization of FGF-2, which was achieved by utilizing optimal base materials (CMC), coating materials (rVN) and long-joint segment (PEG4-SPDP) design.

Design of dual peptide-conjugated hydrogels for proliferation and differentiation of human pluripotent stem cells

Completely synthetic cell cultivation materials for human pluripotent stem cells (hPSCs) are important for the future clinical use of hPSC-derived cells. Currently, cell culture materials conjugated with extracellular matrix (ECM)-derived peptides are being prepared using only one specific integrin-targeting peptide. We designed dual peptide-conjugated hydrogels, for which each peptide was selected from different ECM sites: the laminin β4 chain and fibronectin or vitronectin, which can target α6β1 and α2β1 or αVβ5. hPSCs cultured on dual peptide-conjugated hydrogels, especially on hydrogels conjugated with peptides obtained from the laminin β4 chain and vitronectin with a low peptide concentration of 200 μg/mL, showed high proliferation ability over the long term and differentiated into cells originating from 3 germ layers in vivo as well as a specific lineage of cardiac cells. The design of grafting peptides was also important, for which a joint segment and positive amino acids were added into the designed peptide. Because of the designed peptides on the hydrogels, only 200 μg/mL peptide solution was sufficient for grafting on the hydrogels, and the hydrogels supported hPSC cultures long-term; in contrast, in previous studies, greater than 1000 μg/mL peptide solution was needed for the grafting of peptides on cell culture materials.