FOXP1 controls mesenchymal stem cell commitment and senescence during skeletal aging
Hanjun Li, … , Zhengju Yao, Xizhi Guo
Hanjun Li, … , Zhengju Yao, Xizhi Guo
Published February 27, 2017
Citation Information: J Clin Invest. 2017;127(4):1241-1253. https://doi.org/10.1172/JCI89511.
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Research Article Aging Stem cells

FOXP1 controls mesenchymal stem cell commitment and senescence during skeletal aging

Abstract

A hallmark of aged mesenchymal stem/progenitor cells (MSCs) in bone marrow is the pivot of differentiation potency from osteoblast to adipocyte coupled with a decrease in self-renewal capacity. However, how these cellular events are orchestrated in the aging progress is not fully understood. In this study, we have used molecular and genetic approaches to investigate the role of forkhead box P1 (FOXP1) in transcriptional control of MSC senescence. In bone marrow MSCs, FOXP1 expression levels declined with age in an inverse manner with those of the senescence marker p16INK4A. Conditional depletion of Foxp1 in bone marrow MSCs led to premature aging characteristics, including increased bone marrow adiposity, decreased bone mass, and impaired MSC self-renewal capacity in mice. At the molecular level, FOXP1 regulated cell-fate choice of MSCs through interactions with the CEBPβ/δ complex and recombination signal binding protein for immunoglobulin κ J region (RBPjκ), key modulators of adipogenesis and osteogenesis, respectively. Loss of p16INK4A in Foxp1-deficient MSCs partially rescued the defects in replication capacity and bone mass accrual. Promoter occupancy analyses revealed that FOXP1 directly represses transcription of p16INK4A. These results indicate that FOXP1 attenuates MSC senescence by orchestrating their cell-fate switch while maintaining their replicative capacity in a dose- and age-dependent manner.

Authors

Hanjun Li, Pei Liu, Shuqin Xu, Yinghua Li, Joseph D. Dekker, Baojie Li, Ying Fan, Zhenlin Zhang, Yang Hong, Gong Yang, Tingting Tang, Yongxin Ren, Haley O. Tucker, Zhengju Yao, Xizhi Guo

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Figure 5

Ablation of Foxp1 results in premature senescence of MSCs.

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Ablation of Foxp1 results in premature senescence of MSCs. (A) In vitro ...
(A) In vitro population doublings of MSCs from Foxp1Prx1Δ/Δ BM at 1 and 6 months. n = 4. (B) FACS analysis dot plot of BrdU+ labeled MSCs (defined as CD31–CD45–CD29+Sca1+) following 48-hour pulse-chase in BM of 3-month-old mice. n = 3. (C) Quantification of the percentages of BrdU+ MSCs in 3-month-old mice. n = 4. (D) qPCR assessment of cell-cycle inhibitor (p16INK4A, p21, and p27) expression in BM MSCs. n = 3. (E) Giemsa staining for the CFU-F colonies of BM MSCs from Foxp1Prx1Δ/Δ mutant mice at 3, 6, and 12 months. n = 3. (F) Quantification of the number of CFU-F colonies in E. n = 3. (G) Western blot detection of FOXP1, p16INK4A, H3K9me3, and LAP2β protein levels in BM MSCs. (H) SA–β-gal staining, Ki67, γH2AX, and LAP2β immunostaining of the second passage of MSCs. Scale bars: 50 μm. (I and J) Quantification of Ki67+ and γH2AX+ frequencies in MSCs from H. n = 3. (K) Quantification of the DCFDA fluorescence intensities reveals increased ROS levels in MSCs (CD31–CD45–CD29+Sca1+) from Foxp1Prx1Δ/Δ BM at 3 months old. n = 4. *P < 0.05; **P < 0.01; ***P < 0.001.