iKO mice exhibited the ultrastructure impairment of SMC. (A) Transmission electron microscope (TEM) images of aortic smooth muscle. WT and iKO mice were treated with tamoxifen injection parallelly, and ascending aortas were excised and fixed 14 days after injection. White boxes point out nuclei, showing karyopyknosis in iKO SMC. Length of longitudinal smooth muscle filaments, WT group:13.96±3.22μm (up left), iKO group: 2.71±0.57μm (up right). p < 0.001; Upper panel: scale bar, 2μm, middle scale bar, 1μm below scale bar, 200nm. (B) Transmission electron microscope (TEM) images of colonic smooth muscle. WT and iKO mice were treated with tamoxifen injection parallelly, and sigmoid colons were excised and fixed 14 days after injection. White arrows: vacuoles. Diametre of smooth muscle, 52.76±0.95μm (up left: WT group) vs. 37.48±2.56μm (up right: iKO group). p < 0.01; Upper panel: scale bar, 5μm, below scale bar, 1μm.