Traditionally, the hematopoietic system destroyed by the chemotherapy or radiation therapy is rebuilt by CD34+ cells produced in the bone marrow. In the past few years, CD34+ cells have demonstrated in animal models, their ability to facilitate angiogenesis in the myocardium and peripheral and central nerve system after stroke. Despite the lack of complete understanding of such mechanism, evidence has shown that CD34+ cells can embed in the blood vessels and the paracrine system of the angiogenic factor to promote microvascular growth. 
 AR Mackie, et al. (2021). Tex Heart Inst J.CD34-positive stem cells: in the treatment of heart and vascular disease in human beings.