Transient expansion and myofibroblast conversion of adipogenic lineage precursors mediate bone marrow repair after radiation
Leilei Zhong, … , Wei Tong, Ling Qin
Leilei Zhong, … , Wei Tong, Ling Qin
Published April 8, 2022
Citation Information: JCI Insight. 2022;7(7):e150323. https://doi.org/10.1172/jci.insight.150323.
View: Text | PDF
Research Article Bone biology Vascular biology

Transient expansion and myofibroblast conversion of adipogenic lineage precursors mediate bone marrow repair after radiation

Abstract

Radiation causes a collapse of bone marrow cells and elimination of microvasculature. To understand how bone marrow recovers after radiation, we focused on mesenchymal lineage cells that provide a supportive microenvironment for hematopoiesis and angiogenesis in bone. We recently discovered a nonproliferative subpopulation of marrow adipogenic lineage precursors (MALPs) that express adipogenic markers with no lipid accumulation. Single-cell transcriptomic analysis revealed that MALPs acquire proliferation and myofibroblast features shortly after radiation. Using an adipocyte-specific Adipoq-Cre, we validated that MALPs rapidly and transiently expanded at day 3 after radiation, coinciding with marrow vessel dilation and diminished marrow cellularity. Concurrently, MALPs lost most of their cell processes, became more elongated, and highly expressed myofibroblast-related genes. Radiation activated mTOR signaling in MALPs that is essential for their myofibroblast conversion and subsequent bone marrow recovery at day 14. Ablation of MALPs blocked the recovery of bone marrow vasculature and cellularity, including hematopoietic stem and progenitors. Moreover, VEGFa deficiency in MALPs delayed bone marrow recovery after radiation. Taken together, our research demonstrates a critical role of MALPs in mediating bone marrow repair after radiation injury and sheds light on a cellular target for treating marrow suppression after radiotherapy.

Authors

Leilei Zhong, Lutian Yao, Nicholas Holdreith, Wei Yu, Tao Gui, Zhen Miao, Yehuda Elkaim, Mingyao Li, Yanqing Gong, Maurizio Pacifici, Amit Maity, Theresa M. Busch, Kyu Sang Joeng, Keith Cengel, Patrick Seale, Wei Tong, Ling Qin

×

Figure 4

Radiation quickly promotes MALP expansion.

Options: View larger image (or click on image) Download as PowerPoint
Radiation quickly promotes MALP expansion. (A) Representative fluorescen...
(A) Representative fluorescence images of Td+ cells (top) and Perilipin+ lipid-laden adipocytes (LiLAs) (bottom) in the bone marrow of 1-month-old Adipoq/Td femur before (NR) and after (R) focal radiation. Scale bar: 20 μm (top) and 100 μm (bottom). (B) The time course change of MALPs, LiLAs, and total adipogenic lineage cells (MALPs plus LiLAs) after radiation. BMA, bone marrow area. n = 3–5 mice/group. (C) Flow analysis of Td+ cells in bone marrow. n = 3–5 mice/group. (D) Representative fluorescence images of EdU incorporation in stromal and perivascular cells of Adipoq/Td mice before and at 3 days after radiation. Arrows point to EdU+Td+ cells. Scale bar: 20 μm. (E) Quantification of EdU+ cells in Td+ stromal cells (S) and pericytes (P). n = 4 mice/group. (F) qRT-PCR analysis of cell cycle–promoting genes in sorted Td+ cells before and at 3 days after radiation. n = 3 mice/group. (G) Representative fluorescence images of γH2AX and TUNEL staining in bone marrow. An arrow points to γH2AX foci. Scale bar: 10 μm. (H) Representative fluorescence images of CFU-F colonies from Adipoq/Td bone marrow with or without focal radiation. Scale bar: 100 μm. (I) Quantification of Td–, Td+, and total CFU-F colonies per 1 million bone marrow cells before and after radiation. n = 3 mice/group. (J) Representative Oil Red O staining of mesenchymal progenitors from nonirradiated (NR) and irradiated femoral bone marrow cultured in growth (top) and adipogenic (AD, bottom) medium. Scale bar: 20 μm (top) and 100 μm (bottom). (K) qRT-PCR analysis of adipogenic markers in mesenchymal progenitors cultured in adipogenic medium. n = 3 mice/group. Statistical analysis was performed using 1-way ANOVA with Tukey’s multiple-comparison analysis (B, C, E, and I) or nonparametric Student’s t test (F and K). *: P < 0.05; **: P < 0.01; ***: P < 0.001 (day 3 or day 7 vs. day 0). #: P < 0.05; ###: P < 0.001. (day 7 vs. day 14).