Dysregulated systemic lymphocytes affect the balance of osteogenic/adipogenic differentiation of bone mesenchymal stem cells after local irradiation.
While it is known that irradiation can induce local and systemic bone loss over time, how focal irradiation induces systemic bone complications remains unclear. Immune cells are thought to be crucial to bone homeostasis, and abnormal immune cells lead to serious disruption of bone homeostasis, such as in acute lymphoblastic leukaemia. This disruption primarily occurs due to inhibition of the osteogenic differentiation of bone mesenchymal stem cells (BMSCs).



In this study, we detected local and systemic bone loss in trabecular bone by micro-computed tomography (micro-CT) and measurement of peroxisome proliferator-activated receptor gamma (PPARγ) and runt-related transcription factor 2 (RUNX2) expression in BMSCs using real-time polymerase chain reaction and western blotting. Additionally, changes in lymphocytes (B cells and CD4+and CD8+T cells) in the peripheral blood and bone marrow were analysed by flow cytometry. BMSC-derived osteoblasts and adipocytes, cultured in osteogenic or adipogenic media or co-cultured with lymphocytes, were detected by BCIP/NBT, Alizarin Red S and Oil Red O staining.



Focal irradiation induced local and systemic bone loss in trabecular bone. Increased PPARγ expression and decreased RUNX2 expression were observed, accompanied by upregulated adipogenesis and downregulated osteogenesis of BMSCs. B cells and CD8+T lymphocytes were increased in the blood and bone marrow after irradiation, while CD4+T lymphocytes were decreased in the blood. Inhibition of RUNX2 expression and reduction of alkaline phosphatase activity and mineralization deposits were observed in lymphocyte-co-cultured BMSCs, accompanied by an increase in PPARγ expression and in the number of lipid droplets.



Focal irradiation induced local and systemic bone loss in trabecular bone. Increased B cells and CD8+T lymphocytes led to systemic bone loss by decreasing BMSC osteogenesis.
Department of Radiation Biology, Institute of Radiation Medicine, Fudan University, No. 2094 Xie-Tu Road, Shanghai, 200032, China.
Xiaoya
X
Xu
Obstetrics and Gynecology Hospital of Fudan University, No. 419 Fangxie Road, Shanghai, 200011, China.
Ruixia
R
Li
Department of Radiation Biology, Institute of Radiation Medicine, Fudan University, No. 2094 Xie-Tu Road, Shanghai, 200032, China.
Yi
Y
Zhou
Department of Radiation Biology, Institute of Radiation Medicine, Fudan University, No. 2094 Xie-Tu Road, Shanghai, 200032, China.
Qiong
Q
Zou
Department of Radiation Biology, Institute of Radiation Medicine, Fudan University, No. 2094 Xie-Tu Road, Shanghai, 200032, China.
Qiaoling
Q
Ding
Department of Radiation Biology, Institute of Radiation Medicine, Fudan University, No. 2094 Xie-Tu Road, Shanghai, 200032, China.
Jinfeng
J
Wang
Department of Radiation Biology, Institute of Radiation Medicine, Fudan University, No. 2094 Xie-Tu Road, Shanghai, 200032, China.
Weifang
W
Jin
Department of Radiation Biology, Institute of Radiation Medicine, Fudan University, No. 2094 Xie-Tu Road, Shanghai, 200032, China.
Guoqiang
G
Hua
Department of Radiation Biology, Institute of Radiation Medicine, Fudan University, No. 2094 Xie-Tu Road, Shanghai, 200032, China. mulei80@sina.com.|Department of Bone Metabolism, Institute of Radiation Medicine, Fudan University, No. 2094 Xie-Tu Road, Shanghai, 200032, China. mulei80@sina.com.
Jianjun
J
Gao
D017667:Adipocytes / Q000378:metabolism / Q000528:radiation effects; D050156:Adipogenesis / Q000528:radiation effects*; D000818:Animals; D001854:Bone Marrow Cells / Q000166:cytology* / Q000528:radiation effects; D004307:Dose-Response Relationship, Radiation; D005434:Flow Cytometry; D005720:Gamma Rays; D018655:Lymphocyte Count; D008214:Lymphocytes / Q000166:cytology* / Q000528:radiation effects; D008297:Male; D059630:Mesenchymal Stem Cells / Q000166:cytology* / Q000528:radiation effects*; D010006:Osteoblasts / Q000378:metabolism / Q000528:radiation effects; D010012:Osteogenesis / Q000528:radiation effects*; D012333:RNA, Messenger / Q000235:genetics / Q000378:metabolism; D017207:Rats, Sprague-Dawley
D012333:RNA, Messenger
Bone mesenchymal stem cells (BMSCs); Irradiation; Lymphocytes; PPARγ; RUNX2