The effects of irisin on the rat thoracic aorta: a histological study

Irisin, a polypeptide hormone that is released from skeletal muscle in response to exercise, has been found to improve endothelial functions, protect against endothelial injuries and change blood pressure, which also affected blood vessels. The aim of this study was to assess the histological changes of the rat thoracic aorta in response to irisin injection.Twenty-four rats were used. They were divided into two groups: the control group without irisin injection and the irisin-injected group subdivided into three subgroups treated with different irisin concentrations (20, 40 and 160 nM, respectively) twice a week for 4 weeks. The control group and irisin-treated subgroups 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 haematoxylin and eosin and orcein stains. Morphometric measurement included: intima-media thickness, number of elastic lamellae and number of smooth muscle cells' nuclei.Histological study showed that intraperitoneal injection of different concentrations of irisin (20, 40 and 160 nM) in rats increased intima-media thickness, the number of smooth muscle cell's nuclei and the number of elastic lamellae in media layer of the thoracic aorta in a dose-dependent manner.Irisin significantly affected the morphology of the wall of the rat thoracic aorta indicating a role of irisin in influencing the growth factors of the thoracic aorta walls and activating smooth muscle cells in the thoracic aorta layers.