Acute leukemia decreases osteoblast numbers and function in humans and in mice. (A) Osteoblast number per trabecular bone area (N.Ob/T.Ar) in bone biopsies of 21 male subjects with AML or MDS, and 21 sex- and age-matched healthy controls. (B) Serum osteocalcin levels in a subset of 9 AML/MDS untreated subjects and 9 matched controls. (C-F) Representative vertebral section images from 2-month-old immunocompetent BALB/c or albino C57BL/6 mice injected with the myeloid-monocytic WEHI-3B (n = 8-10 mice per group) (C) or the lymphoblastic EL4 (n = 5-7 mice per group) (D) leukemia cells, respectively. Mineralized bone matrix is stained in black by Von Kossa reagent. Images at ×50. Serum levels of osteocalcin (E) and cross-linked C-telopeptide (CTX) (F) in WT animals and leukemic mice injected with WEHI-3B cells (n = 8-10 mice per group). *P < .05 vs normal control or WT mice. BFR, bone formation rate; BV/TV, bone volume per trabecular volume; N.Ob/T.Ar, number of osteoblasts per trabecular area; Oc.S./B.S., osteoclast surface per bone surface.