LAUSR

Irisin, a polypeptide hormone that is released from skeletal muscle in response to exercise found to improve endothelial functions, protect against endothelial injuries and change blood pressure which also affected blood vessels. The aim of this study is to study the histological changes of the rat thoracic aorta in response to irisin injection. Thirty rats were used. Then divided into two groups; the control group without irisin injection, and the irisin injected group was subdivided into four subgroups with different irisin concentrations (20, 40 and 160 nM, respectively) twice a week for four weeks, the control group and each subgroup consisted of 6 rats each. After 4 weeks all rats were sacrificed, and the descending thoracic aorta was treated for histological evaluation. Sections were stained with Hematoxylin and Eosin (H and E) and orcein stains. Morphometric measurement included: intima-media thickness (IMT), number of elastic lamellae and number of smooth muscle cells nuclei. Histological study has shown that intraperitoneal injection of different concentrations of irisin (20, 40 and 160 nM) in rats has increased intima-media thickness, number of smooth muscle cell's nuclei, and increase the number of elastic lamellae in media layer of the thoracic aorta in a dose dependent manner. Irisin has significantly affected the morphology of the wall of the rat thoracic aorta indicating a role for irisin in influencing the growth factors of the thoracic aorta walls and activate smooth muscle cells in the thoracic aorta layers.