A therapeutic system for treating a disease in a patient, the system comprising: genetically altered mammalian endothelial progenitor cells, comprising exogenous nucleic acid encoding a genetically-engineered exogenous cell membrane marker molecule not normally found in natural, unaltered cells circulating in the bloodstream of the patient and at least one therapeutic gene product, wherein said cell membrane marker molecule is an osteogenic protein, a prostatic cell membrane protein, or an H-2K k surface protein, and said therapeutic gene product is selected from prostacyclin, calcitonin gene related peptide, vascular endothelial growth factor, angiogenin, anti-angiogenic factor, and fibroblast growth factor, said cells being capable of expressing said marker molecule and therapeutic gene product, and said cells to be administered to the patient so as to be present in the circulating blood of the patient; and a medical device for implantation into a blood vessel lumen of the patient comprising a coating; said coating comprising a flexible matrix bearing at least one ligand, wherein said ligand is selected depending on the genetically engineered cell membrane marker molecule and is capable of specifically recognizing and exclusively binding said cell membrane marker molecule of said genetically altered endothelial progenitor cells, and comprises an antibody, antibody fragment, or combination of antibody and antibody fragments; wherein, in use of the therapeutic system, said genetically altered endothelial progenitor cells arc captured from the circulating blood and bind in vivo to said medical device to form a confluent endothelium in situ and express and secrete said at least one therapeutic gene product. genetically altered mammalian endothelial progenitor cells, comprising exogenous nucleic acid encoding a genetically-engineered exogenous cell membrane marker molecule not normally found in natural, unaltered cells circulating in the bloodstream of the patient and at least one therapeutic gene product, wherein said cell membrane marker molecule is an osteogenic protein, a prostatic cell membrane protein, or an H-2K k surface protein, and said therapeutic gene product is selected from prostacyclin, calcitonin gene related peptide, vascular endothelial growth factor, angiogenin, anti-angiogenic factor, and fibroblast growth factor, said cells being capable of expressing said marker molecule and therapeutic gene product, and said cells to be administered to the patient so as to be present in the circulating blood of the patient; and a medical device for implantation into a blood vessel lumen of the patient comprising a coating; said coating comprising a flexible matrix bearing at least one ligand, wherein said ligand is selected depending on the genetically engineered cell membrane marker molecule and is capable of specifically recognizing and exclusively binding said cell membrane marker molecule of said genetically altered endothelial progenitor cells, and comprises an antibody, antibody fragment, or combination of antibody and antibody fragments; wherein, in use of the therapeutic system, said genetically altered endothelial progenitor cells arc captured from the circulating blood and bind in vivo to said medical device to form a confluent endothelium in situ and express and secrete said at least one therapeutic gene product.