Mast cell activation by NGF drives the formation of trauma-induced heterotopic ossification
Tao Jiang, Xiang Ao, Xin Xiang, Jie Zhang, Jieyi Cai, Jiaming Fu, Wensheng Zhang, Zhenyu Zheng, Jun Chu, Minjun Huang, Zhongmin Zhang, Liang Wang
Tao Jiang, Xiang Ao, Xin Xiang, Jie Zhang, Jieyi Cai, Jiaming Fu, Wensheng Zhang, Zhenyu Zheng, Jun Chu, Minjun Huang, Zhongmin Zhang, Liang Wang
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Research Article Bone biology Immunology

Mast cell activation by NGF drives the formation of trauma-induced heterotopic ossification

Abstract

Soft tissue trauma can cause immune system disturbance and neuropathological invasion, resulting in heterotopic ossification (HO) due to aberrant chondrogenic differentiation of mesenchymal stem cells (MSCs). However, the molecular mechanisms behind the interaction between the immune and nervous systems in promoting HO pathogenesis are unclear. In this study, we found that mast cell–specific deletion attenuated localized tissue inflammation, with marked inhibition of HO endochondral osteogenesis. Likewise, blockage of nerve growth factor (NGF) receptor, known as tropomyosin receptor kinase A (TrkA), led to similar attenuations in tissue inflammation and HO. Moreover, while NGF/TrkA signaling did not directly affect MSCs chondrogenic differentiation, it modulated mast cell activation in traumatic soft tissue. Mechanistically, lipid A in LPS binding to TrkA enhanced NGF-induced TrkA phosphorylation, synergistically stimulating mast cells to release neurotrophin-3 (NT3), thereby promoting MSC chondrogenic differentiation in situ. Finally, analysis of single-cell datasets and human pathological specimens confirmed the important role of mast cell–mediated neuroinflammation in HO pathogenesis. In conclusion, NGF regulates mast cells in soft tissue trauma and drives HO progression via paracrine NT3. Targeted early inhibition of mast cells holds substantial promise for treating traumatic HO.

Authors

Tao Jiang, Xiang Ao, Xin Xiang, Jie Zhang, Jieyi Cai, Jiaming Fu, Wensheng Zhang, Zhenyu Zheng, Jun Chu, Minjun Huang, Zhongmin Zhang, Liang Wang

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Figure 4

NGF promotes traumatic HO progression without enhancing chondrogenic differentiation of tissue-resident stem cells.

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NGF promotes traumatic HO progression without enhancing chondrogenic dif...
(A) Schematic representation of saline, rmNGF, or GW administration and traumatic HO induction. (B) Representative μCT 3D modeling images and quantification (right) of ectopic BV in Achilles tendon from the indicated groups 8 weeks after tenotomy. Red dashed ovals represent ectopic bones. Scale bar: 2 mm. n = at least 6 biological replicates. (C and D) Representative images for SOFG and Masson’s staining, along with the quantification (right) of bone marrow (BM) areas in injured tendon sections from the indicated groups 8 weeks after tenotomy. The BM areas are expressed as a percentage of the total tendon area. Scale bar: 5 μm. n = 5 biological replicates. (E–H) Representative IF images quantification (right) for SOX9 (red), COL2A1 (green), RUNX2 (red), and OCN (green) of injured tendon sections in the indicated groups after tenotomy, with DAPI counterstaining (blue). Positive staining areas of these proteins were quantified. Scale bar: 5 μm. n = 5 biological replicates. (I and J) TB staining was performed on TDSCs challenged with rmNGF (1, 10, 100 ng/mL), GW (1 μM), or rmNGF (100 ng/mL) + GW (1 μM) in chondrogenic culture for 14 days, compared with control (Con) group and chondrogenesis-alone (Ch) group. (K and L) Under the aforementioned conditions (I and J), Western blotting and densitometric quantification (right) of COL2A1 and SOX9 were performed, with β-actin as the loading control. n = 3 biological replicates. Data are representative of 2 independent experiments (B–L). Data were shown as mean ± SD and compared with 1-way ANOVA with Tukey’s multiple-comparison test.