Background:In postmenopausal osteoporosis, hormonal alteration leads to bone turnover and muscle weakness. Activin typeIIB receptors were revealed to increase bone & muscle mass. This experiment was designed to explore ActRIIB-Fc-ligands administration alone or with swimming-exercise might restore musculoskeletal system homeostasis followed negative effects of estrogen deficiency in ovariectomized rat model.

Methods:Fifty adult female albino rats were divided into 5groups: Group I (control sham rats) were subjected to i.p. PBS. In the other groups rats were exposed to ovariectomy procedures. Group II, III, IV rats were exposed to i.p. PBS, exercise-training-protocol, i.p. ActRIIB-Fc (5mg/kg/week) 7weeks respectively, while groupV rats were exposed to exercise-training-protocol and i.p ActRIIB-Fc. Finally, body weights & muscle strength tests were examined for all animals. After scarification, uterine weights and muscle mass (quadriceps femoris & gastrocnemius) measurements were obtained. Serum biochemical and histopathological parameters were examined; also, RNA was extracted from their right femora to perform genes expression.

Results:Exercise-training and ActRIIB-Fc were capable to reverse changes of muscle strength and bone mass measurements of OVX rats. Significant elevation in osteocalcin & P1NP and significant reduction in CTX, TOS, TAC, IL-1β, IL-6, and CK values, moreover, down-regulation of RANKL and up-regulation of OPG genes expression were detected. These significant values and histomorphometric osteoporotic variations were more pronounced in groupV.

Conclusion:Addition of ActRIIB-Fc ligand to exercise-training-protocol acts as a musculoskeletal-enhancing agent in OVX rats. This result was proved by reduction of osteoclast function and elevation of some osteoblast genes expression;therefore, it could be a respectable choice in musculoskeletal disorders management.