SYNTHETIC HYDROGELS AS SCAFFOLDS FOR MANIPULATING ENDOTHELIUM CELL BEHAVIORS

Synthetic hydrogels can be used as scaffolds that not only favor endothelial cells （ECs） proliferation but also manipulate the behaviors and functions of the ECs. In this review paper, the effect of chemical structure, Young＇s modulus （E） and zeta potential （ζ） of synthetic hydrogel scaffolds on static cell behaviors, including cell morphology, proliferation, cytoskeleton structure and focal adhesion, and on dynamic cell behaviors, including migration velocity and morphology oscillation, as well as on EC function such as anti-platelet adhesion, are reported. It was found that negatively charged hydrogels, poly（2-acrylamido-2-methylpropanesulfonic sodium） （PNaAMPS） and poly（sodium p-styrene sulphonate） （PNaSS）, can directly promote cell proliferation, with no need of surface modifcation by any cell-adhesive proteins or peptides at the environment of serum-containing medium. In addition, the Young＇s modulus （E） and zeta potential （ζ） of hydrogel scaffolds are quantitatively tuned by copolymer hydrogels, poly（NaAMPS-co-DMAAm） and poly（NaSS-co-DMAAm）, in which the two kinds of negatively charged monomers NaAMPS and NaSS are copolymerized with neutral monomer, N,N-dimethylacrylamide （DMAAm）. It was found that the critical zeta potential of hydrogels manipulating EC morphology, proliferation, and motility is ζcritical= -20.83 mV and ζcritical = -14.0 mV for poly（NaAMPS-co-DMAAm） and poly（NaSS-co-DMAAm）, respectively. The above mentioned EC behaviors well correlate with the adsorption of fibronectin, a kind of cell-adhesive protein, on the hydrogel surfaces. Furthermore, adhered platelets on the EC monolayers cultured on the hydrogel scaffolds obviously decreases with an increase of the Young＇s modulus （E） of the hydrogels, especially when E 〉 60 kPa. Glycocalyx assay and gene expression of ECs demonstrate that the anti-platelet adhesion well correlates with the EC-specific glycocalyx. The above investigation suggests that understanding the relationship between physic-chemical properties of synthetic hydrogels and cell responses is essential to design optimal soft and wet scaffolds for tissue engineering. Keywords： Synthetic hydrogel; Scaffold; Endothelial cell; Cell behavior

Supragel-mediated efficient generation of pancreatic progenitor clusters and functional glucose-responsive islet-like clusters

Although several synthetic hydrogels with defined stiffness have been developed to facilitate the proliferation and maintenance of human pluripotent stem cells(hPSCs),the influence of biochemical cues in lineage-specific differentiation and functional cluster formation has been rarely reported.Here,we present the application of Supragel,a supramolecular hydrogel formed by synthesized biotinylated peptides,for islet-like cluster differentiation.We observed that Supragel,with a peptide concentration of 5 mg/mL promoted spontaneous hPSCs formation into uniform clusters,which is mainly attributable to a supporting stiffness of∼1.5 kPa as provided by the Supragel matrix.Supragel was also found to interact with the hPSCs and facilitate endodermal and subsequent insulin-secreting cell differentiation,partially through its components:the sequences of RGD and YIGSR that interacts with cell membrane molecules of integrin receptor.Compared to Matrigel and suspension culturing conditions,more efficient differentiation of the hPSCs was also observed at the stages 3 and 4,as well as the final stage toward generation of insulin-secreting cells.This could be explained by 1)suitable average size of the hPSCs clusters cultured on Supragel;2)appropriate level of cell adhesive sites provided by Supragel during differentiation.It is worth noting that the Supragel culture system was more tolerance in terms of the initial seeding densities and less demanding,since a standard static cell culture condition was sufficient for the entire differentiation process.Our observations demonstrate a positive role of Supragel for hPSCs differentiation into islet-like cells,with additional potential in facilitating germ layer differentiation.