Influence of HA and of HA’ase on formation of the adherent layer. Primary bone marrow cells were cultured in 6-well plates without any addition (A, D, and G) or with the addition of 100 μg/mL of HA (B, E, and H) or with 0.1 U/mL HA’ase (C, F, and I). Photographs were taken after 1 (top panel), 4 (middle panel), and 8 (bottom panel) weeks of culture. Only adherent cells are shown. In (D), (E), (G), and (H), typical cobblestone-like cells are visible, which are increased in number in (E) and (H), whereas in (F) and (I) such cells are hardly detectable. The magnification was 400-fold.