CCL3 in the bone marrow microenvironment causes bone loss and bone marrow adiposity in aged mice
Degang Yu, Shuhong Zhang, Chao Ma, Sen Huang, Long Xu, Jun Liang, Huiwu Li, Qiming Fan, Guangwang Liu, Zanjing Zhai
Degang Yu, Shuhong Zhang, Chao Ma, Sen Huang, Long Xu, Jun Liang, Huiwu Li, Qiming Fan, Guangwang Liu, Zanjing Zhai
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Research Article Aging Bone biology

CCL3 in the bone marrow microenvironment causes bone loss and bone marrow adiposity in aged mice

Abstract

The central physiological role of the bone marrow renders bone marrow stromal cells (BMSCs) particularly sensitive to aging. With bone aging, BMSCs acquire a differentiation potential bias in favor of adipogenesis over osteogenesis, and the underlying molecular mechanisms remain unclear. Herein, we investigated the factors underlying age-related changes in the bone marrow and their roles in BMSCs’ differentiation. Antibody array revealed that CC chemokine ligand 3 (CCL3) accumulation occurred in the serum of naturally aged mice along with bone aging phenotypes, including bone loss, bone marrow adiposity, and imbalanced BMSC differentiation. In vivo Ccl3 deletion could rescue these phenotypes in aged mice. CCL3 improved the adipogenic differentiation potential of BMSCs, with a positive feedback loop between CCL3 and C/EBPα. CCL3 activated C/EBPα expression via STAT3, while C/EBPα activated CCL3 expression through direct promoter binding, facilitated by DNA hypomethylation. Moreover, CCL3 inhibited BMSCs’ osteogenic differentiation potential by blocking β-catenin activity mediated by ERK-activated Dickkopf-related protein 1 upregulation. Blocking CCL3 in vivo via neutralizing antibodies ameliorated trabecular bone loss and bone marrow adiposity in aged mice. This study provides insights regarding age-related bone loss and bone marrow adiposity pathogenesis and lays a foundation for the identification of new targets for senile osteoporosis treatment.

Authors

Degang Yu, Shuhong Zhang, Chao Ma, Sen Huang, Long Xu, Jun Liang, Huiwu Li, Qiming Fan, Guangwang Liu, Zanjing Zhai

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Figure 3

Deletion of CCL3 counteracts in vivo bone loss and bone marrow adiposity of aged mice.

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Deletion of CCL3 counteracts in vivo bone loss and bone marrow adiposity...
(A) Femur length of young and aged wild-type (WT) and Ccl3–/– mice (n = 12). (B) BV/TV, Tb.N, Tb.Th, and Tb.Sp of distal femur from young and aged WT and Ccl3–/– mice (n = 12). (C) Representative micro-CT 3D reconstruction images. Scale bar: 500 μm. (D) Ct.Ar/Tt.Ar and Ct.Th of femur midshaft from young and aged WT and Ccl3–/– mice (n = 12). (E) Representative micro-CT 3D reconstruction images. Scale bar: 500 μm. (F) Double calcein labeling images and BFR quantification in femur of young and aged WT and Ccl3–/– mice (n = 12). Scale bar: 50 μm. (G) Quantification of maximum load and stiffness in 3-point bending test in femur of young and aged WT and Ccl3–/– mice (n = 12). (H) Quantification of Ad.Ar/Ma.Ar and Ad.N/Ma.Ar on the basis of Oil Red O staining of young and aged WT and Ccl3–/– mice femurs (n = 12). Scale bar: 500 μm. All data were obtained from 3 independent experiments. The images and numerical data are representative. Data are presented as mean ± SD; 2-way ANOVA. *P < 0.05, **P < 0.01, ***P < 0.001.