Department of Orthopedics, Xijing Hospital, Fourth Military Medical University, Xi'an, Shaanxi 710032, China; Department of Surgery, Rocket Force 96110 Military Hospital of PLA, Yinchuan 750000, China.
Department of Orthopedics, Xijing Hospital, Fourth Military Medical University, Xi'an, Shaanxi 710032, China; Department of Orthopedics, Eastern Theater Air Force Hospital of PLA, Nanjing 210000, China.
Exp Neurol. 2024 Oct;380:114915. doi: 10.1016/j.expneurol.2024.114915. Epub 2024 Aug 7.
The inflammatory response and scar formation after spinal cord injury (SCI) limit nerve regeneration and functional recovery. Our research group has previously shown that the expression of astrocyte-derived lipocalin 2 (Lcn2) is upregulated after SCI, which correlates with neuronal apoptosis and functional recovery. Therefore, we speculate that astrocyte-specific knockdown of Lcn2 after SCI may lead to a better prognosis.
Tissue RNA sequencing, Western blotting, PCR, and immunofluorescence assays were conducted to assess the expression of Lcn2 following SCI in mice. Adeno-associated virus 9 (AAV9) transfection was employed to specifically reduce the expression of Lcn2 in astrocytes, and subsequent evaluations of scarring and inflammation were conducted. In vitro experiments involved treating primary astrocytes with TGF-β or an A1-induced mixture (C1q, TNF-α and IL-1α) following Lcn2 knockdown. Finally, the intrathecal injection of recombinant Lcn2 (ReLcn2) protein was conducted post-injury to further confirm the role of Lcn2 and its underlying mechanism in SCI.
Lcn2 expression was elevated in astrocytes after SCI at 7 dpi (days post injury). Lcn2 knockdown in astrocytes is beneficial for neuronal survival and functional recovery after SCI, and is accompanied by a reduced inflammatory response and inhibited scar formation. The inhibition of SMAD-associated signaling activation was identified as a possible mechanism, and in vitro experiments further confirmed this finding. ReLcn2 further activated SMAD-associated signaling and aggravated motor function after SCI.
The upregulation of Lcn2 expression in astrocytes is involved in neuroinflammation and scar formation after SCI, and the activation of SMAD-associated signaling is one of the underlying mechanisms.
脊髓损伤（SCI）后的炎症反应和瘢痕形成限制了神经再生和功能恢复。我们的研究小组先前已经表明，SCI 后星形胶质细胞衍生的脂钙蛋白 2（Lcn2）的表达上调，与神经元凋亡和功能恢复相关。因此，我们推测 SCI 后星形胶质细胞特异性敲低 Lcn2 可能导致更好的预后。
通过组织 RNA 测序、Western blot、PCR 和免疫荧光检测评估 SCI 后小鼠 Lcn2 的表达。采用腺相关病毒 9（AAV9）转染特异性降低星形胶质细胞中的 Lcn2 表达，并进行随后的瘢痕和炎症评估。体外实验涉及在 Lcn2 敲低后用 TGF-β或 A1 诱导的混合物（C1q、TNF-α和 IL-1α）处理原代星形胶质细胞。最后，在损伤后鞘内注射重组 Lcn2（ReLcn2）蛋白以进一步证实 Lcn2 在 SCI 中的作用及其潜在机制。
SCI 后 7 天（伤后天）星形胶质细胞中 Lcn2 表达升高。星形胶质细胞中 Lcn2 的敲低有利于 SCI 后神经元的存活和功能恢复，并伴有炎症反应减轻和瘢痕形成抑制。鉴定出 SMAD 相关信号激活的抑制是一种可能的机制，体外实验进一步证实了这一发现。ReLcn2 进一步激活了 SMAD 相关信号，并在 SCI 后加重了运动功能。
SCI 后星形胶质细胞中 Lcn2 的表达上调参与了神经炎症和瘢痕形成，SMAD 相关信号的激活是其中的一种潜在机制。
