Reduced HO-1hiPMos in SCD patients at risk of VOC. (A) Soluble VCAM-1 levels in platelet-free plasma from race-matched HDs (n = 10) and SCD patients grouped as “Non-VOC” (n = 38) and “VOC” (n = 15, see “Methods” for patient characteristics) were tested by enzyme-linked immunosorbent assay. Absolute (B) neutrophil and (C) monocyte counts in peripheral blood were determined by Advia Hematology Analyzer. (D) Frequency of PMos within total circulating monocyte population. Absolute numbers of (E) PMos and (F) HO-1hi PMos were calculated based on monocyte counts and monocyte subset frequency. (G) Absolute numbers of HO-1hi PMos at monthly intervals in the VOC (n = 6) and non-VOC (n = 11) groups. The arrow indicates the timing of the vaso-occlusive event in the VOC group. Data represent mean ± SEM; means in panels A-F were compared using 2-tailed Student t test and means in panel G were compared using 2-way analysis of variance. *P < .05; **P < .01; ***P < .001.
