One of the most recent hormones to be identified and isolated is irisin, extracted from mouse skeletal muscle in 2012. Irisin has been proven to alter blood pressure, which has an impact on blood vessels, enhance endothelial functions, and prevent injury to endothelial cells. The current study aimed to study the effect of irisin on the ultrastructure of the rat thoracic aorta using the transmission electron microscope (TEM).

Twenty female rats were recruited for this study and divided into a control group (non-injected), and four experimental groups (injected groups) each consisting of 4 rats. The experimental groups were injected intraperitoneally with different doses of irisin (250ng/mL, 500ng/mL, 1000ng/mL, and 2000ng/mL) twice a week for 4weeks. Then, the descending thoracic aorta of all experimental rats were resected and proceeded with imaging.

The results of this study showed a change in the thickness of the tunica intima, internal elastic lamina, elastic lamellae, and external elastic lamina concerning increasing injected irisin concentration. While there was a significant increase in the thickness of tunica media (P<0.0001) and smooth muscle cells (P<0.05). Also, the results showed a significant increase in the number of elastic lamellae in the tunica media (P<0.0001).

Irisin had a major impact on the elasticity of the rat thoracic aorta wall, suggesting that it influences the growth factors of the wall and activates smooth muscle cells in addition to endothelial cells.