Fig. 1

The histological differences between hydrogels from osteogenic and non-osteogenic culture conditions. H&E staining revealed differences in cell appearance between groups (a osteogenic, b non-osteogenic, black arrows show blurred cavity border, black arrowhead show the nucleus, scale bars 20 µm). Alizarin Red S staining indicated the high calcium ion content evenly distributed within the hydrogel in osteogenic group (c), whereas in control hydrogel was not stained (d *hydrogel, w culture well, scale bars 400 µm). The analysis of histological sections showed strong Alizarin Red S reaction of cells (black arrows) and hydrogel’s edges (white arrowheads) in osteogenic group (e), while in control only single cells (black arrow) and the superficial zone of hydrogel (black arrowhead) were positively stained (f scale bars 200 µm)