The current invention discloses compositions of matter, therapeutic protocols, and combination therapies utilizing previously unknown activity of Xenon alone or in combination with other Noble gases to augment therapeutic activity of regenerative cells, in one embodiment said regenerative cells comprising of mesenchymal stem cells. In one embodiment the invention provides use of xenon-pretreatment of cells prior to in vivo application in order to allow for enhanced efficacy of said cells. In other embodiments xenon alone, or in combination with other gases is utilized to modulate regenerative activity of cells in vivo.