RESUMO
BACKGROUND/AIMS: Transplantation of endothelial progenitor cells (EPCs) plays a therapeutic role in pulmonary arterial hypertension (PAH). Meanwhile, recruitment of progenitors has potential inflammatory effects and exaggerates vascular injury. CD40 pathway is identified as a major player in vascular inflammatory events. In this study, we investigated the role of CD40 pathway in regulating early outgrowth EPC functions, and searched for improvements in PAH cell therapy. METHODS: EPCs were isolated from rat bone marrow and cultured for 7 days. After treatment with soluble CD40 ligand (sCD40L) for 24 hours, EPC migration, adhesion, proliferation, paracrine and vasculogenesis functions were tested. Rat PAH model was founded by subcutaneous injection of monocrotaline (MCT). Control EPCs or lentivirus vectors (Lv)-shRNA-CD40 EPCs were infused via tail vein at day 7, 14, and 21 after MCT injection. Therapeutic effects were evaluated at day 28. RESULTS: sCD40L dose-dependently impaired EPC migration, adhesion, proliferation, and vasculogenesis functions. However, paracrine effects of soluble intercellular adhesion molecule-1, vascular endothelial growth factor and interleukin-6 were dose-dependently improved by sCD40L. Control EPC-derived conditioned medium protected endothelial cell in vitro vasculogenesis, while sCD40L-pretreated ones showed detrimental effects. After MCT injection, sCD40L levels in rat serum increased gradually. Other than in vitro results, benefits of both two EPC treatments were obvious, even taken at day 21. Benefits of control EPCs wore off over time, but those of Lv-shRNA-CD40 EPCs were more effective and enduring, as characterized by both ameliorated rat hemodynamic and reversed vascular remodeling. Furthermore, Lv-shRNA-CD40 EPCs integrated into endothelium better, rather than into adventitia and media. CONCLUSION: sCD40L impaired protective effects of EPCs. Traditional EPC treatments were limited in PAH, while interruption of CD40 pathway of transplanted cells could apparently improve the therapeutic efficacy.