Abstract: Contemplated compositions and methods are directed to the use of microvesicles from an optionally recombinant donor cell to impart a desirable effect to a recipient cell. In certain preferred aspects, RNA of the microvesicles is employed to achieve the desirable effect. For example, microvesicles are used in vitro to increase the number of passages of a cell growing in a medium, reduce serum and/or growth factor requirements of a cell growing in a medium, and/or delay differentiation of a cell growing in a medium. Further preferred aspects include use of the microvesicles as therapeutic agents in which RNA, a membrane protein, and/or a cytosolic protein encapsulated in or coupled to the microvesicle provide a therapeutic effect. Additionally, diagnostic methods are contemplated in which RNA of a microvesicle isolated from a mammal is associated with a condition of the mammal.