Thrombospondin-1 and Vitamin D in Children With Sickle Cell Anemia

BACKGROUND: Thrombospondin-1 (TSP-1) and 25-hydroxyvitamin D (25-OHD) play significant roles in the pathogenesis of sickle cell anemia (SCA). TSP-1 enhances cellular adhesion/inflammation, hence contributing to vaso-occlusive crisis (VOC); vitamin D, in contrast, retards inflammation and may lower rate of pain episodes. We determined serum levels of TSP-1 and 25-OHD in Nigerian children with SCA and their matched hemoglobin AA controls; and assess the relationship between the 2 biomarkers. METHODS: In total 90 children (32 SCA in steady state, 30 SCA in VOC, and 28 HbAA controls) were studied. Serum TSP-1 and 25-OHD levels were measured with ELISA and HPLC, respectively. RESULTS: The mean TSP-1 of children with VOC was significantly higher than those in steady state (P=0.022) and HbAA controls (P<0.001). Similarly, the mean TSP-1 of those in steady state was higher than the controls (P=0.007). However, mean serum 25-OHD of the children with VOC was significantly lower than those in steady state (28.9±8.2 ng/mL vs. 37.1±12.3 ng/mL, P =0.004). There was a significant inverse correlation between TSP-1 and 25-OHD among the VOC subgroup, r=-0.57, P=0.001. The mean TSP-1 of the 28 children with SCA who had suboptimal vitamin D (213.5±118.6 ng/mL) was higher than 144.2±58.7 ng/mL of the 34 SCA who had normal serum vitamin D, P=0.008. CONCLUSIONS: Children with SCA, especially those with VOC, had high serum TSP-1 and low 25-OHD. Also, an inverse relationship exist between serum 25-OHD and TSP-1 in children with VOC. These findings provide basis for further studies into the regulation of TSP-1 by vitamin D.