CD34 and cardiovascular disorder: Moreover, because osteoblasts (whose activity can be assessed in terms of bone-type ALP expression [14, 15]) regulate the production of hematopoietic stem cells in the bone marrow [10–12], serum ALP level may correlate with vascular homeostatic activity, and a prospective study reported a strong association between a reduced number of endothelial progenitor cells (CD34-positive and KDR-positive cell) and risk of cardiovascular disease [23].