Effect of EGF on number and properties of tunnels. Human keratinocytes
were plated on fibrin matrix and cultivated in medium containing hrEGF
at different concentrations. After 24 h, cultures were fixed, and
the number of helical tunnels was counted and expressed as percent of
total cells attached to the fibrin (A). The properties
of the tunnels, including the number of turns (B),
helical pitch (C), and the length of the track composing
the helix (D), were estimated from a total of 30 helical
tunnels.