Elevated Circulating Stromal Derived Factor-1 Levels in Sickle Cell Disease.

Inflammation and angiogenesis are of importance in the pathophysiology of sickle cell disease (SCD). Recently, the chemokine Stromal Derived Factor-1 (SDF-1) has been shown to be a key mediator of angiogenesis and inflammation. In this study we determined serum SDF-1 levels in consecutive adult sickle cell patients during the clinically asymptomatic state as well as during painful crisis. Serum SDF-1 levels were significantly elevated in HbSS/HbSβ0-thalassemia patients ([n=39], 3805 pg/mL (2121–6790)) as opposed to HbSC/HbSβ+-thalassemia patients ([n=18], 2405 pg/mL (1365–3047)) and healthy HbAA controls (n=25, 2623 pg/mL (2435–2988)) (p=0.04). During painful crisis SDF-1 levels increased significantly in both HbSS/HbSβ0-thalassemia ([n=24]) 26040 pg/mL (20135–27960)) and HbSC/HbSβ+-thalassemia patients ([n=5], 12666 pg/mL (3936–24453)) (p<0.001 and p=0.01, respectively). Paired sample analysis was possible in 8 patients (SDF-1 determined in steady state and during painful crisis) and all patients demonstrated a strong SDF-1 increment from steady state levels (p=0.01) and serial measurements, available from 11 patients, showed persistently elevated SDF-1 levels well beyond crisis abatement (data not shown). Furthermore, SDF-1 levels were significantly higher in sickle cell patients with pulmonary hypertension as compared to patients without pulmonary hypertension in both HbSS/HbSβ0-thalassemia (PHT+ [n=8]: 6549 pg/mL (3893–7159), PHT- [n=24]: 2945 pg/mL (1560–6627)) and HbSC/HbSβ+-thalassemia (PHT+ [n=4] 3316 pg/mL (2900–6417) and PHT- [n=12] 2146 pg/mL (1138–2592)) patients (p=0.02 and p=0.01, respectively). SDF-1 levels were not related to other forms of organ damage, nor were they significantly associated with hemoglobin levels, the percentage of fetal hemoglobin or leukocyte counts in the clinically asymptomatic state (data not shown). Taken together, elevated circulating SDF-1 levels occur in patients with SCD and may play a role in the pathophysiology of acute and specific chronic disease related complications.