Figure 1. Host response to single dose local radiation promotes BMDC mobilization and colonization in Matrigel plugs.

A. Eight-to-ten week old non-tumor bearing BALB/c mice were exposed to a single dose of local radiation (RT) (2 Gy, 6 Gy and 10 Gy) in the abdominal cavity. Blood was drawn from the retro-orbital sinus at baseline, 24, 72 and 144 hours after radiation. The levels of viable circulating endothelial progenitor cells (EPCs), hemangiocytes (Hems) and myeloid derived suppressor cells (MDSCs) in peripheral blood (PB) were evaluated as described in Materials and Methods (n = 4–5 mice/group). Statistical significance (p < 0.05) between baseline and 2 Gy (*), 6 Gy (#) and 10 Gy ($) local radiation is shown. B-C. Matrigel plugs containing 10% plasma collected from untreated control (Control) or locally irradiated mice (24 hours following 2Gy radiation) (RT) were implanted into the flanks of 8–10-week-old BALB/c mice. After 10 days, the plugs were removed and processed for histology and flow cytometry. Matrigel cryosections were stained with H&E (B). Matrigel plugs were prepared as single cell suspensions and the extracted cells were immunostained for various BMDC populations including macrophages (Mφ), MDSCs, endothelial cells (ECs), hemangiocytes (HEMs), and Mast cells. Results are presented as the number of cells per 1 mg Matrigel (C). Scale bars = 100 μm. D-E. Eight-to-ten week old SCID mice were orthotopically implanted with SW480 tumors and either left untreated (control) or exposed to 2Gy RT. After 72 hours, the tumors were harvested, sectioned and immunostained for endothelial cells (CD31, red). Nuclei were stained with DAPI (blue) (D). Scale bars = 200 μm. The number of microvessel structures per field was counted (n > 10 fields/group) (E). *0.05 > p > 0.01; **0.01 > p > 0.001; ***p < 0.001.