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 trophect oderm in vitro were investigated Experiment 1 evaluated the effects of plasminogen and ECM type on ICM and trophectodermal outgrowth, on gla ss Lab-Tek chamber slides coated with collagen IV, fibronectin, or lam inin. ICM outgrowth areas were reduced (p < 0.05) by plasminogen and w ere 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 I CM outgrowth on fibronectin. Numbers of cells in the outgrowths were i ncreased (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 outgrow-th in microdrop cultures. PA production by ICM was greatest (p < 0.05) on fibronectin, but no diffe rences (p > 0.10) were observed for trophectoderm. PA production was n ot correlated with ICM outgrowth areas (r = -0.12; p = 0.72) or number s of cells in the ICM outgrowths (r = 0.09; p = 0.74) but was correlat ed with ICM areas (r = 0.75; p < 0.01) and numbers of cells in trophec todermal outgrowths (r = 0.57; p = 0.01). These results suggest that t ype of ECM, culture system, and alterations in the PA system influence cellular outgrowths by ICM and trophectoderm.