Angiogenesis induced by the injection of peripheral leukocytes and platelets

BACKGROUND: Peripheral leukocytes and platelets (LAPs) contain many kinds of cells with the ability to secrete several growth factors and cytokines. We attempted to induce therapeutic angiogenesis by injecting self-LAPs into a rat ischemic hindlimb model. MATERIALS AND METHODS: Supernatants from cultured LAPs were used for the endothelial cell (EC) proliferation assay, and LAPs were used in a cornea model to evaluate angiogenic potency. LAPs were injected directly into the male Dark Agouti rat ischemic hindlimb model, after which a microangiogram was done and the capillary/muscle fiber ratio was examined histologically. ELISA revealed the levels of contributing growth factors and cytokines present in the ischemic muscles. RESULTS: The EC proliferation assay showed that the supernatants of LAPs accelerated proliferation and that the LAPs induced angiogenesis in the cornea model. The microangiograms and histological evaluation revealed that angiogenesis was induced more effectively in the rats injected with LAPs (LAP group) than in the those injected with phosphate-buffered saline (PBS group). The levels of basic fibroblast growth factor (bFGF) in the ischemia, PBS, and LAP groups were significantly increased compared to those in the sham group. The level of interleukin-1beta (IL-1beta) in the LAP group was significantly more elevated than in the other groups. CONCLUSIONS: The injection of self-LAPs induced angiogenesis in a rat ischemic hindlimb model. Ischemia caused an elevation in the level of bFGF and also in IL-1beta derived from LAPs, which contributed to angiogenesis. This is a novel, yet simple and safe method of inducing therapeutic angiogenesis.