Schematic representation of findings. (A) Interaction of normal BMPCs that produce proangiogenic (dark red) and antiangiogenic (dark green) factors, respectively. At a normal ratio, angiogenesis is restricted to the surrounding of BMPCs. (B) By proliferation and increasing number, aberrant as well as normal BMPC factors accumulate in the bone marrow microenvironment, inducing widespread angiogenesis.