Disclosed are stem cells and nanoparticles derived from said stem cells, useful for the treatment of acute radiation syndrome (ARS) and other inflammatory conditions. In one embodiment, Endometrial Regenerative Cells (ERC) are administered to patients having been exposed to radiation to augment recovery of endogenous hematopoietic stem cells. In another embodiment, exosomes, nanoparticles that are generated by various stem cells are used as a drug for treatment of inflammatory conditions.
