Circulating CD34⁺ Cells: A New Biomarker of Residual Pulmonary Vascular Obstruction after Pulmonary Embolism

Pulmonary embolism (PE) is a life-threatening condition with long-term complications, including residual pulmonary vascular obstruction (RPVO). RPVO is associated with an increased risk of venous thromboembolism recurrence, chronic symptoms, and reduced quality of life. We hypothesize that an endothelial activation and vascular injury play a central role in the pathophysiology of RPVO. This prospective monocentric study investigates the potential of circulating biomarkers, including CD34⁺ cells, circulating endothelial cells (CECs), and platelet-derived growth factor BB (PDGF-BB), as indicators of vascular sequelae and predictors of RPVO. We included 56 patients with a first episode of PE. Biomarker levels were measured at PE diagnosis and six months later, coinciding with RPVO assessment using ventilation-perfusion lung scans. This defined groups of patients with (RPVO ≥ 10%) and without (RPVO < 10%) perfusion defects. Associations between biomarker levels, presence of perfusion defects, and clinical parameters were analyzed. At PE diagnosis, CEC and PDGF-BB levels were significantly elevated in patients compared to healthy controls, while CD34⁺ levels showed no difference. At the six-month follow-up, patients with perfusion defects exhibited significantly lower CD34⁺ cell levels compared to those without (median 1440 cells/mL vs. 2960 cells/mL). No significant differences in CEC or PDGF-BB levels were observed at follow-up. In conclusion, low CD34⁺ cell levels at RPVO assessment suggest a decreased regenerative potential contributing to thrombus persistence. CD34⁺ cells may serve as biomarkers for perfusion defects and warrant further study for their potential role in guiding clinical management of PE complications.