Figure 3.

Pulmonary sheet compaction is accelerated by endothelial/monocyte–activating polypeptide (EMAP) II, whereas cohesivity is decreased. The assembly of dissociated fetal lung cells into an aggregate within 48 hours into pulmonary sheets was assessed. HDs treated with EMAPII exhibited a more rapid rate (A) of compaction as compared with controls (P = 0.0038, Student's t test, representative experiment performed at least 10 times). Magnification, 100×. PBs subjected to TST were noted to have liquid properties and surface tension that, by linear regression, was shown to be independent of aggregate size (B) (r²=0.0008). (C) PB aggregates at precompression (top panels) and after PBs have reached force and shape equilibria (bottom panels). PB cohesivity was markedly decreased in aggregates treated with EMAPII as compared with controls (D) (P = 0.0002; n = 14). Dissociated fetal lung cells were stained with membrane intercalating green or red fluorescent dyes. After formation, PBs were fused in 3D HDs and envelopment assessed. The less cohesive EMAPII-treated PBs enveloped the more cohesive untreated PBs (G and H). Combinations in which like-aggregates were used fused along their midline and formed a planar interface (E and F). Scale bar, 40 μm.