Exosomes from human CD34(+) stem cells mediate their proangiogenic paracrine activity.

Rationale: Transplantation of human CD34(+) stem cells to ischemic tissues has been associated with reduced angina, improved exercise time, and reduced amputation rates in phase 2 clinical trials and has been shown to induce neovascularization in preclinical models. Previous studies have suggested that paracrine factors secreted by these proangiogenic cells are responsible, at least in part, for the angiogenic effects induced by CD34(+) cell transplantation.

Objective: Our objective was to investigate the mechanism of CD34(+) stem cell-induced proangiogenic paracrine effects and to examine if exosomes, a component of paracrine secretion, are involved.