Macrophage Infiltration Is a Causative Factor for Ligamentum Flavum Hypertrophy through the Activation of Collagen Production in Fibroblasts
Macrophage Infiltration Is a Causative Factor for Ligamentum Flavum Hypertrophy through the Activation of Collagen Production in Fibroblasts
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DOI：
10.1016/j.ajpath.2017.08.020
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发表时间：
2017-12-01
影响因子：
6
通讯作者：
Okada, Seiji
中科院分区：
文献类型：
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作者：
Saito, Takeyuki;Hara, Masamitsu;Okada, Seiji
黄韧带(LF)肥大导致腰椎管狭窄，导致老年人腿部疼痛和日常生活能力障碍。虽然以往对LF肥大的研究已有报道，但其发病机制尚未完全阐明。在这项研究中，我们证明了巨噬细胞的渗入是导致LF肥大的一个因素。用微创方法诱导巨噬细胞进入小鼠LF，可导致LF肥大，并伴有损伤部位的胶原沉积和成纤维细胞增殖，这与人类重度肥厚的LF的特征非常相似。然而，我们发现，通过注射含有氯屈膦酸盐的脂质体来耗尽巨噬细胞可以对抗LF肥大，即使是在微损伤的情况下。为了鉴定成纤维细胞，我们将I型胶原α(2)连接到绿色荧光蛋白转基因小鼠，并利用激光显微切割从微损伤的LF中选择性地分离出绿色荧光蛋白阳性的成纤维细胞。激光显微切割标本的定量RT-PCR结果显示，与未损伤部位相比，巨噬细胞浸润性损伤部位的成纤维细胞胶原基因表达明显增加。这些结果提示巨噬细胞通过刺激成纤维细胞产生胶原而在LF肥大中起关键作用，为进一步了解LF肥大的病理生理机制提供了依据。
Ligamentum flavum (LF) hypertrophy causes lumbar spinal canal stenosis, leading to leg pain and disability in activities of daily living in elderly individuals. Although previous studies have been performed on LF hypertrophy, its pathomechanisms have not been fully elucidated. In this study, we demonstrated that infiltrating macrophages were a causative factor for LF hypertrophy. Induction of macrophages into the mouse LF by applying a microinjury resulted in LF hypertrophy along with collagen accumulation and fibroblasts proliferation at the injured site, which were very similar to the characteristics observed in the severely hypertrophied LF of human. However, we found that macrophage depletion by injecting clodronate-containing liposomes counteracted LF hypertrophy even with microinjury. For identification of fibroblasts in the LF, we used collagen type I alpha(2) Linked to green fluorescent protein transgenic mice and selectively isolated green fluorescent protein-positive fibroblasts from the microinjured LF using laser microdissection. A quantitative RT-PCR on laser microdissection samples revealed that the gene expression of collagen markedly increased in the fibroblasts at the injured site with infiltrating macrophages compared with the uninjured location. These results suggested that macrophage infiltration was crucial for LF hypertrophy by stimulating collagen production in fibroblasts, providing better understanding of the pathophysiology of LF hypertrophy.