Burt Kevin G, Kim Min Kyu M, Viola Dan C, Genualdi Joseph R, Marciano Gerard F, Chahine Nadeen O
Department of Orthopedic Surgery, Columbia University, New York, New York, USA.
Department of Biomedical Engineering, Columbia University, New York, New York, USA.
FASEB J. 2025 Jun 30;39(12):e70711. doi: 10.1096/fj.202402658R.
Frequently evaluated in musculoskeletal disease, damage associated molecular patterns (DAMPs) respond to tissue damage and cellular stress by facilitating an inflammatory response via macrophage activation and broad inflammatory pathway activation. In the context of disc degeneration (DD), high mobility group box 1 (HMGB1), a potent intracellular DAMP, is seen to be increased within severely degenerated human IVDs and to directly mediate inflammatory responses within disc cells in vitro. To further understand how HMGB1-mediated inflammation influences DD, this study evaluated the possible protective effect of an HMGB1 knockout on DD pathology following injury. Using a needle puncture injury model in murine caudal IVDs, we evaluated DD pathology within an IVD-specific Hmgb1 knockout (KO) model. Structural and compositional changes in IVD cellularity, histopathology, disc height, and biomechanics were evaluated in addition to an assessment of disc inflammation and macrophage presence throughout the course of degeneration. HMGB1 expression robustly increased shortly following needle puncture injury, and elevated levels were sustained up to 28 days post injury both in injured IVDs and in the IVDs adjacent to the level of injury. IVD-specific Hmgb1 KO mice had an increased disc height following injury both at the injured and adjacent to injury levels compared to wild type (WT) control IVDs. Hmgb1 KO also protected against tissue mechanical property losses at both the injured (dynamic modulus) and adjacent to injury levels (dynamic modulus, creep, and equilibrium modulus) compared to WT IVDs; however, there was no significant effect on histopathologic scores post injury. Hmgb1 KO did not alter basal expression of Ccl2 or Cxcl12 in uninjured discs. Disc puncture injury increased CCL2 secretion; however, these levels were similar in IVDs from WT and Hmgb1 KO mice. Hmgb1 KO reduced sub-acute (28-days post injury) macrophage (F4/80+) recruitment to injured IVDs in vivo. Reduced macrophage migration was also observed in vitro in response to the secretome of an injured Hmgb1 KO IVD compared to injured WT IVD secretome. Overall findings indicate that HMGB1 is upregulated regionally within IVDs, at both the injured level and at the level adjacent to the injury. Results suggest that IVD HMGB1 production plays a role in mediating structural and biomechanical responses of the IVD to injury, particularly in mediating sub-acute macrophage recruitment to the injured IVD.
在肌肉骨骼疾病中经常被评估的损伤相关分子模式（DAMPs），通过巨噬细胞激活和广泛的炎症途径激活来促进炎症反应，从而对组织损伤和细胞应激做出反应。在椎间盘退变（DD）的背景下，高迁移率族蛋白B1（HMGB1）作为一种强大的细胞内DAMP，在严重退变的人类椎间盘内含量增加，并在体外直接介导椎间盘细胞内的炎症反应。为了进一步了解HMGB1介导的炎症如何影响DD，本研究评估了HMGB1基因敲除对损伤后DD病理变化的可能保护作用。使用小鼠尾椎椎间盘针刺损伤模型，我们在椎间盘特异性Hmgb1基因敲除（KO）模型中评估了DD病理变化。除了在整个退变过程中评估椎间盘炎症和巨噬细胞的存在外，还评估了椎间盘细胞数量、组织病理学、椎间盘高度和生物力学的结构和成分变化。针刺损伤后不久，HMGB1表达强烈增加，并且在损伤的椎间盘以及损伤水平相邻的椎间盘中，升高的水平持续到损伤后28天。与野生型（WT）对照椎间盘相比，椎间盘特异性Hmgb1基因敲除小鼠在损伤水平以及损伤相邻水平的椎间盘高度在损伤后均增加。与WT椎间盘相比，Hmgb1基因敲除还能防止损伤水平（动态模量）以及损伤相邻水平（动态模量、蠕变和平衡模量）的组织力学性能损失；然而，对损伤后的组织病理学评分没有显著影响。Hmgb1基因敲除不会改变未损伤椎间盘中Ccl2或Cxcl12的基础表达。椎间盘穿刺损伤增加了CCL2的分泌；然而，WT和Hmgb1基因敲除小鼠的椎间盘内这些水平相似。Hmgb1基因敲除减少了体内亚急性（损伤后28天）巨噬细胞（F4/80+）向损伤椎间盘的募集。与损伤的WT椎间盘分泌组相比，在体外对损伤的Hmgb1基因敲除椎间盘分泌组的反应中也观察到巨噬细胞迁移减少。总体研究结果表明，HMGB1在椎间盘内局部上调，在损伤水平以及损伤相邻水平均如此。结果表明，椎间盘HMGB1的产生在介导椎间盘对损伤的结构和生物力学反应中起作用，特别是在介导亚急性巨噬细胞向损伤椎间盘的募集中起作用。
