PECAM1 and cyclic hematopoiesis: In addition, SU5416 did not increase the radius of myocardial tissue served by each capillary (Fig. 3f), or significantly inhibit CH-PH induced RV EC proliferation (CD31+/CD45.2−/Ki-67+ cells; Fig. 4), though there was a non-significant reduction in RV EC proliferation in the SU5416 treated mice (P = 0.24 vs. CH-PH, Tukey’s multiple comparisons test).