Abstract-Bone marrow-derived cells have been proposed to form new vessels or at least incorporate into growing vessels in adult organisms under certain physiological and pathological conditions. We investigated whether bone marrowderived cells incorporate into vessels using mouse models of hindlimb ischemia (arteriogenesis and angiogenesis) and tumor growth. C57BL/6 wild-type mice were lethally irradiated and transplanted with bone marrow cells from littermates expressing enhanced green fluorescent protein (GFP). At least 6 weeks after bone marrow transplantation, the animals underwent unilateral femoral artery occlusions with or without pretreatment with vascular endothelial growth factor or were subcutaneously implanted with methylcholanthrene-induced fibrosarcoma (BFS-1) cells. Seven and 21 days after surgery, proximal hindlimb muscles with growing collateral arteries and ischemic gastrocnemius muscles as well as grown tumors and various organs were excised for histological analysis. We failed to colocalize GFP signals with endothelial or smooth muscle cell markers. Occasionally, the use of high-power laser scanning confocal microscopy uncovered false-positive results because of overlap of different fluorescent signals from adjacent cells. Nevertheless, we observed accumulations of GFP-positive cells around growing collateral arteries (3-fold increase versus nonoccluded side, PϽ0.001) and in ischemic distal hindlimbs. These cells were identified as fibroblasts, pericytes, and primarily leukocytes that stained positive for several growth factors and chemokines.

This trial demonstrates that, among PAH patients who remain symptomatic on bosentan or sildenafil, inhaled treprostinil improves exercise capacity and quality of life and is safe and well-tolerated. (TRIUMPH I: Double Blind Placebo Controlled Clinical Investigation Into the Efficacy and Tolerability of Inhaled Treprostinil Sodium in Patients With Severe Pulmonary Arterial Hypertension; NCT00147199).

When performed in experienced centers, right heart catheter procedures in patients with pulmonary hypertension are associated with low morbidity and mortality rates.