Abstract 760: Efficacy of Early, But Not Late Growth Human Endothelial Progenitor Cells in a Nude Rat Model of Pulmonary Hypertension
Our group and others have shown the ability of endothelial progenitor cells (EPCs) to prevent the onset of monocrotaline (MCT)-induced pulmonary hypertension in a rat model. However, uncertainty remains surrounding the optimal cell-type for treatment of the human disease. In this study we aimed to determine the therapeutic capacity of early (E-hEPC) and late outgrowth (L-hEPC) human EPCs cultured from peripheral blood leukapheresis samples using an athymic nude rat model of MCT-induced pulmonary hypertension.
Methods and Results: Two distinct populations of leukapheresis-derived human EPCs were characterized by flow cytometry. E-hEPCs appear within a few days of culture and disappear by 3 weeks, are positive for CD14 and KDR and negative for CD34. L-hEPCs appear after 2 weeks in culture, are highly proliferative, grow in a cobblestone pattern and express CD34 and KDR. Three days after intraperitoneal injection of MCT (0.7mg/kg), 106 cells (E-hEPC, L-hEPC, pulmonary arterial endothelial cells (hPAEC) or no cell sham) were administered to nude rats via central venous injection. Three weeks after cell injection, right ventricular systolic pressure (RSVP) was markedly elevated in MCT treated animals (61 ± 3.8 versus 27 ± 0.5 mmHg no MCT control). The administration of E-hEPCs prevented the onset of pulmonary hypertension (33 ± 3.2 mmHg, n=8, P<0.01), while delivery of L-hEPCs produced no improvement (60 ± 4.0 mmHg, n=14). Right ventricular hypertrophy was also observed in MCT and L-hEPC groups (0.45 ± 0.02 and 0.46 ± 0.01) but not with E-hEPC treatment (0.34 ± 0.03, all data are ratios of right ventricular to left ventricular weight plus septum). Interestingly, the delivery of hPAECs provided moderate protection against the onset of pulmonary hypertension (46 ± 3.6 mmHg) and right ventricular hypertrophy (0.37 ± 0.02). Endothelial cell specific oligonucleotide arrays revealed that E-hEPCs express relatively few endothelial genes, while L-hEPCs have a gene expression profile very similar to that of hPAECs.
Conclusion: Despite less endothelial differentiation, the largely mononuclear E-hEPCs were clearly superior in this model. This result is consistent with an indirect paracrine mechanism of action in the repair and regeneration of injured lung endothelium.