Study on the iron accumulation-induced bone loss and hematopoietic autophagy dysfunction / 中华内分泌代谢杂志

ABSTRACT

Objective:Iron accumulation is related to the occurrence of postmenopausal osteoporosis. Meanwhile, autophagy abnormality of bone marrow hematopoietic cells is observed in hip osteoporotic fracture. This study is performed to investigate correlation between iron accumulation induced bone loss and hematopoietic autophagy dysfunction to explore the new risk factor of osteoporosis.Methods:Male iron accumulation mice model was established by intraperitoneally injecting ferric ammonium citrate. Serum ferritin and osteogenic indicator P1NP were tested by ELISA. Bone mineral density was measured by micro-CT. Femur and tibia bone marrows were collected for hematopoietic stem and progenitor cells proportion and cell apoptosis analysis. Autolysosome formation was measured by image flow cytometry. We used conditional mouse model Atg7 flox/flox; Vav-Cre(Atg7 -/-) in which Atg7 had been genetically deleted in the hematopoietic system. Bone marrow hematopoietic stem and progenitor cells were collected for RNA sequence. micro-CT scan was conducted for Atg7 -/- femur. Results:Ferritin level of iron accumulation mice was significantly higher than control group( P<0.05). Iron accumulation inhibited P1NP and induced decreased bone mineral density( P<0.05). Iron accumulation bone marrow displayed enhanced hematopoietic stem and progenitor cells proportion( P<0.05), with more cell apoptosis( P<0.05). Hematopoietic autophagy was deteriorated in iron accumulation bone marrow. Transcriptomic profiling showed up-regulation of iron activity in Atg7 -/- mice, with increased iron homeostasis and iron membrane transporter genes, including Lcn2, Tfr2, Slc40a1(Fpn1), Steap3, and Cpox. micro-CT revealed severe bone loss and decreased bone mineral density in Atg7 -/- mice( P<0.05). Conclusion:Iron accumulation induced bone loss is related to inhibition of hematopoietic cells. Hematopoietic autophagy dysfunction is associated with bone loss.