Immunohistochemical staining of Tet-regulated transgene expressing murine hearts. Eight week old mice were left uniduced or induced to express the stable HIF-1α-PPN-HA transgene over four weeks. A. HA immunohistological staining while left uninduced (On dox), B. HA immunological staining following doxycycline removal and transgene induction for; three days (3 days off dox), C. seven days (7 days off dox), and D. twenty-eight days (28 days off dox). A clear and progressive build-up of the stable HIF-1α-PPN-HA transgene can be seen over the course of four weeks. All images (20X); HA=hemagglutinin.