Adenovirus vector mediated LacZ transgene expression in synovial tissues. Synovium alone or synovium with cartilage from joint replacement surgery and synovectomy was implanted subcutaneously on the lower backs of C.B-17 severe combined immunodeficiency (SCID) mice. LacZ adenovirus (Ad-LacZ) in 0.1 ml PBS was injected at a dosage of 1011, 1010, or 109 particles into the middle of the grafted tissues. An equal amount of PBS was injected as a control. Three days after virus injection, synovial tissues were collected and LacZ transgene expression in the synovial tissues was detected by X-gal staining. (a) The dose of 1011 virus particles of Ad-LacZ per injection resulted in high transgene expression in human synovium; (b) the dose of 1010 virus particles of Ad-LacZ per injection resulted in lower transgene expression; (c) the dose of 109 virus particles of Ad-LacZ per injection failed to induce LacZ transgene expression, similar to (d) PBS injected control tissues. (e) The expression of LacZ transgene only was apparent in synovium but not in cartilage three days after injection of 1011 virus particles (the red arrow indicates synovium; the white arrow indicates cartilage). (f) There was no evidence of chondrocyte infection by Ad-LacZ in cartilage, as demonstrated by X-gal/hematoxylin and eosin staining (original magnification 200×). A variety of cell types including (g) synoviocytes, (h) lymphocytes, (i) macrophages, (j) granulocytes and (k) endothelial cells could be infected by adenovirus vector, indicated by LacZ transgene expression detected with X-gal staining (g-k) (original magnification 400×).