Evaluation of extracellular matrices and the plasminogen activator system in sheep inner cell mass and trophectodermal outgrowth in vitro.

Effects of extracellular matrices (ECM) and the plasminogen activator (PA) system on outgrowth of sheep inner cell masses (ICM) and trophectoderm in vitro were investigated. Experiment 1 evaluated the effects of plasminogen and ECM type on ICM and trophectodermal outgrowth, on glass Lab-Tek chamber slides coated with collagen IV, fibronectin, or laminin. ICM outgrowth areas were reduced (p < 0.05) by plasminogen and were greatest (p < 0.05) on fibronectin. Trophectodermal outgrowth was not supported in this system. Experiment 2 evaluated the effects of PA inhibitor-2 (PAI-2) or antiserum to urokinase-type PA (anti-uPA) on ICM outgrowth on fibronectin. Numbers of cells in the outgrowths were increased (p < 0.05) with PAI-2, and anti-uPA had no effect (p > 0.10). Experiment 3 evaluated the relationship between PA production and ECM type on ICM and trophectodermal outgrowth in microdrop cultures. PA production by ICM was greatest (p < 0.05) on fibronectin, but no differences (p > 0.10) were observed for trophectoderm. PA production was not correlated with ICM outgrowth areas (r = -0.12; p = 0.72) or numbers of cells in the ICM outgrowths (r = 0.09; p = 0.74) but was correlated with ICM areas (r = 0.75; p < 0.01) and numbers of cells in trophectodermal outgrowths (r = 0.57; p = 0.01). These results suggest that type of ECM, culture system, and alterations in the PA system influence cellular outgrowths by ICM and trophectoderm.