The effects of T-cell derived exosomes obtained from osteoporotic patients and healthy individuals on osteoblastic function and gene expression profile

Abstract

Osteoporosis is a common skeletal disorder attributed to age and is defined as a systematic degradation of bone mass and the microarchitecture leading to bone fractures. The main cause of fractures is osteoporosis; especially, when women experience menopause. As osteoporosis pathogenesis is multifactorial, components of the immune system have strong impacts on the bone. Once the term 'osteoimmunology' refers to discoveries linked to the immune system function, which affects the equilibrium of bone remodeling, helping to understand the frequency of osteoporosis and inflammatory reactions. Hypothetically, the postmenopausal osteoporosis is characterized as an autoimmune and inflammatory process in which T-cells possess significant parts. The existence of exosomes has been reported in almost all biological fluids, and also during failure of bone remodeling. Such extracellular vesicles play several roles in the regulation of osteoclastic or osteoblastic networks. Material and methods: 20 ml of blood samples were obtained from osteoporotic and non-osteoporotic postmenopausal women. After peripheral blood mononuclear cells (PBMCs) isolation, T cells were separated via magnetic activated cell sorting (MACS) technique. CD9+, CD63+, and CD81+ exosomes, were then extracted from osteoporotic and non-osteoporotic T cells, and normal osteoblasts were treated with obtained T cell exosomes to assess osteoblastic function and gene expression. Results: The Runx2, type I collagen, osteopontin, and osteocalcin expression decreased in osteoblasts treated by osteoporotic T cell exosomes; while, an increased expression of mentioned genes was observed following non-osteoporotic T cell exosomes treatment. Additionally, osteoblasts alkaline phosphatase (ALP) activity treated with non-osteoporotic T cell exosomes decreased; however, this activity increased in other group.