The Irisin Hormone Profile and Expression in Human Bone Tissue in the Bone Healing Process in Patients

Abstract

BACKGROUND Whether or not there is a relationship between the newly-discovered irisin hormone and bone healing is not yet known. The aim of this study was to investigate what effect irisin hormone has on the bone healing process. MATERIAL AND METHODS The study included 21 adult patients with a diagnosed fracture of the lower extremity (femur or tibia). Informed consent was obtained from all the patients. A total of four venous blood samples were taken from the patients: before fracture stabilization, then postoperatively on days 1, 10, and 60. In patients with femoral neck fracture who had hip prosthesis applied, bone tissue samples were taken from the removed femur head and irisin was determined immunohistochemically in muscle biopsies taken from the same patients. RESULTS In analysis, it was revealed that the mean value of irisin 60 days after operation is significantly higher than the values of irisin before operation, 1 day after operation, and 15 day after operation (p<0.001, p<0.001, p<0.001, respectively). Intense staining was observed in compact bone tissue, muscle tissue, and in hypertrophic vascular endothelium within the Havers canal. CONCLUSIONS The level of irisin hormone increased in the bone union process and affects fracture healing due to irisin receptors in human bone tissue.

Figure 1

Serum irisin levels in patients with fracture before fracture stabilization and on postoperative days 1, 15, and 60.

Figure 2

Serum irisin levels (mean ± standard error of the mean) before operation and on postoperative days 1, 15, and 60.

Figure 3

Irisin immunoreactivities in the spongy and compact bone tissue. Avidin-biotin immunoperoxidase technique, anti-irisin mouse antibody, Mayer’s hematoxylin counterstain. (A) Irisin activity in the capillary endothelia and osteoblasts (arrows), bar=250 micrometer (B) Irisin positive immunostaining in the osteoblast cytoplasm (arrows), bar=60 micrometer (C) Compact tissue irisin activity (arrows), bar=90 micrometer (D) Irisin immunopositive reactions in the bone marrow cells (arrows), bar=120 micrometer.

Figure 4

Irisin immunoreactivities in the skeletal muscle tissue. Avidin-biotin immunoperoxidase technique, anti-irisin mouse antibody, Mayer’s hematoxylin counterstain, bar=120 micrometer.