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. 2000 Mar 1;105(5):577–587. doi: 10.1172/JCI8316

Figure 1.

Figure 1

Low oxygen tension induces trophoblast outgrowth and increases proliferation, fibronectin synthesis, and gelatinase activity in villous explant cultures. (a) Villous explants from 5 to 8 weeks of gestation were maintained in culture for 5 days under normal (20% O2) or low (3% O2) oxygen tension. Note that exposure of villous explants to 3% O2 dramatically increases budding and outgrowth of EVT from the distal end of the villous tips when compared with villous explants kept at 20% O2. ×25, ×50. (b) Section of explants, cultured in either 3% or 20% O2, were stained for Ki67, a marker of cellular proliferation and α5 integrin. Strong positive nickel-enhanced immunoreactivity for Ki67 was observed in EVT of the outgrowth (EVT) of explants cultured in 3% O2. Similar immunolocalization was observed for α5 integrin. A few immunopositive cells for both Ki67 and α5 integrin were noted in explants kept at 20% O2 (arrows). S, villous stroma. (c) Explants incubated for 4 days in either low or normal pO2 conditions were metabolically labeled with [35S]methionine for 18 hours. Fibronectin was isolated from conditioned medium using gelatin-Sepharose beads. Samples were subjected to SDS-PAGE, and the position of the marker (with Mr = 200 × 103) is indicated. (d) Samples of medium conditioned by explants, cultured in either 3 or 20% O2, were collected at day 5 and subjected to analysis by gelatin zymography. Arrows indicate positions of gelatinase activity (gelatinase A/MMP-2: 60 and 68 kDa; gelatinase B/MMP-9: 92 kDa).