CCL3 in the bone marrow microenvironment causes bone loss and bone marrow adiposity in aged mice
Degang Yu, … , Guangwang Liu, Zanjing Zhai
Degang Yu, … , Guangwang Liu, Zanjing Zhai
Published November 15, 2022
Citation Information: JCI Insight. 2023;8(1):e159107. https://doi.org/10.1172/jci.insight.159107.
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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 4

CCL3 improves the adipogenic differentiation potential of BMSCs via STAT3-mediated C/EBPα activation.

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CCL3 improves the adipogenic differentiation potential of BMSCs via STAT...
(A) Oil Red O staining of BMSCs (young) cultured with rCCL3. Scale bar: 10 μm. (B) mRNA expression of Pparg, C/ebpa, aP2, and Glut4 when BMSCs (young) undergo adipogenic differentiation with rCCL3 treatment (n = 12). (C) Oil Red O staining of BMSCs (aged) cultured with rCCL3. Scale bar: 10 μm. (D) mRNA expression of Pparg, C/ebpa, aP2, and Glut4 when BMSCs (aged) undergo adipogenic differentiation with rCCL3 (n = 12). (E) C/ebpa mRNA expression in young and aged BMSCs with rCCL3 treatment (n = 12). (F) Phosphorylated and total STAT3 protein expression in BMSCs with rCCL3 treatment (n = 12). (G) C/ebpa mRNA expression in response to rCCL3 and/or AG490 treatment in BMSCs (n = 12). (H) Luciferase activity of C/EBPα promoter deletion mutant–driven luciferase reporter gene vectors, including Luc (empty vector as negative control), –1,249 bp/+17 bp (containing putative STAT3 binding site) and –558 bp/+17 bp (putative STAT3 binding site deleted), with STAT3 overexpression, in BMSCs treated with rCCL3 for 48 hours (n = 12). (I) ChIP assay using STAT3 antibody against putative STAT3 binding site within C/EBPα promoter in BMSCs treated with rCCL3 and/or AG490. (J) Oil Red O staining of BMSCs (young) after undergoing adipogenic differentiation with rCCL3 and/or AG490 treatment. (K) mRNA expression of Pparg, C/ebpa, aP2, and Glut4 when BMSCs (young) undergo adipogenic differentiation with rCCL3 and/or AG490 treatment (n = 10). (L) Oil Red O staining of BMSCs (aged) after undergoing adipogenic differentiation with rCCL3 and/or AG490 treatment. (M) mRNA expression of Pparg, C/ebpa, aP2, and Glut4 when BMSCs (aged) undergo adipogenic differentiation with rCCL3 and/or AG490 treatment (n = 10). Hprt was used as internal control. All data were obtained from 3 independent experiments. Statistics, 2-way ANOVA. *P < 0.05, **P < 0.01, ***P < 0.001. Scale bar: 10 μm (J and L).