OP9/ephrin-B2 promoted EC sprouting in cultures using dissociated cells from P-Sp explants.

The E9.5 P-Sp region was dissociated enzymatically and cocultured with OP9/ephrin-B2 (▪) or OP9/vector (■) stromal cells in the presence of SCF and VEGF. Immunostaining by anti–PECAM-1 MoAb was performed at the indicated times. (A) The PECAM-1⁺ ECs formed mostly sheetlike structures on OP9/vector stromal cells (inset shows the cordlike structures in OP9/vector stromal cells), whereas the PECAM-1⁺ ECs formed cordlike structures on OP9/ephrin-B2 stromal cells (inset shows the sheetlike structure in OP9/ephrin-B2 stromal cells). The bar indicates 500 μm. (B) The number of sheetlike or cordlike structures on OP9/ephrin-B2 or OP9/vector stromal cells. The results represent the mean ± SD of triplicate cultures.