Nylon mesh ring system used to study HUVEC tubulogenesis. (A) Image of a
nylon mesh ring (MR) on which the collagen gel is cast. HUVEC tubes that
form in the collagen gel are viewed in the central “window” region (W)
of the gel. (B–D) Side-view diagrams of the setup for multiaxial (B, C)
and monolayer-sprout (D, E) culture modes. (B) HUVECs (black dots) are
dispersed in the collagen gel (CG). Nylon mesh ring (MR) and window
region (W) of the collagen gel are indicated. (C) The dispersed cells
organize into multiaxial HUVEC tubes in response to T-medium. In
monolayer-sprout cultures (D), a confluent monolayer (CM) of HUVECs on
top of the collagen gel is induced to sprout into the gel (E). Scale bar
size: A = 5 mm. Abbreviations: HUVEC, human umbilical vein endothelial
cell; T-medium, tubulogenesis medium.