Fig. 6. Pleiotrophin induced UB cell tubulogenesis in vitro. (A) Bar graph demonstrating the morphogenetic effects of pleiotrophin on UB cells grown in three-dimensional extracellular matrix gels. UB cells were suspended in 20% Matrigel, 80% collagen gel mixture and grown for 4 days in the absence (control) or presence of purified pleiotrophin (PTN; 0.1-2.5 µg/ml). Whole BSN-CM served as a positive control. All conditions were supplemented with 1% FCS. The percentage of cells and/or colonies with processes was counted as an indicator for tubulogenic activity. 20 cells and/or colonies were counted in three randomly selected fields for each condition. Data is presented as mean ± s.e.m., *P<0.05 (by unpaired Student’s t-test). (B) Phase contrast photomicrographs of UB cells grown for 8 days in DMEM/F12 supplemented with 1% FCS (a, control) and either BSN-CM (b) or purified pleiotrophin (c). BSN-CM and pleiotrophin induced the formation of branching tubules with lumens (compare b and c). Scale bar, 50 µm.
