【再生医学】衰老细胞的局部清除与创伤后骨关节炎再生

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Local clearance of senescent cells attenuates th developmentof post-traumatic osteoarthritis and creates a pro-regenerative environment浙江大学医学院附属第二医院骨科沈炜亮

发表状况： Nature Medicine， 24 April 2017

研究团队：Jennifer H Elisseeff（jhe@jhu.edu）约翰霍普金斯大学组织工程转化中心

编者有话说：

本文揭示了特异性地去除衰老细胞将延缓OA的发展，同时将创造有利于修复的外环境。

研究背景：

衰老细胞（SnC）随着年龄的增长积累在许多脊椎动物组织中，并且会促进与年龄相关的疾病的发生，并可能是通过分泌促成衰老相关分泌表型（SASP）的因子来实现的。去除SnC延迟了几个病情的发展并延长了健康的生命周期。

老龄化和创伤是发展骨关节炎（OA）的危险因素，骨关节炎（OA）是一种以关节软骨变性为特征，会导致疼痛和身体残疾的慢性疾病。另已从接受关节置换手术的患者中分离的软骨组织中获得衰老软骨细胞，但它们在疾病发病机理中的作用仍未知。

研究方法：

研究者创建并使用了p16-3MR转基因小鼠，其携带ap16INK4a（Cdkn2a）启动子驱动含有合成的Renilla荧光素酶和单体红色荧光蛋白结构域的融合蛋白的表达，以及截短式的单纯疱疹病毒1胸苷激酶（HSV-TK）。已达到定位衰老细胞以及定向去除衰老细胞的目的。

注（本文中主要用到的试剂及各自作用）：

1.p16INK4a（也称为细胞周期蛋白依赖性激酶抑制剂2a;由Cdkn2a基因座编码），常用于标识衰老细胞的生物标志物。

2.GCV:ganciclovir 更昔洛韦，其可通过HSV-TK结构特异性去除衰老细胞。

3.UBX0101: 最近发现的可选择性消除衰老细胞的制剂。

4.AP20187：一种可在表达p16INK4a的细胞中诱导凋亡的分子。

研究结果：

1、通过GCV清除SnC可减缓创伤后OA的发展。

2、通过UBX0101实现的SnC清除减轻了创伤后的OA病情，并产生了软骨形成前的环境。

3、清除SnC可减缓老年小鼠自然发生的OA和创伤后OA的病情。

4、UBX0101通过诱导凋亡来清除SnC，并改善人OA组织软骨细胞的软骨形成能力。

研究结论：

使用SnC作为治疗退行性关节病的治疗靶点是可行的途径。

英文摘要：

Senescent cells (SnCs) accumulate in many vertebrate tissues with age and contribute to age-related pathologies, presumably through their secretion of factors contributing to the senescence-associated secretory phenotype (SASP). Removal of SnCs delays several pathologies and increases healthy lifespan. Aging and trauma are risk factors for the development of osteoarthritis (OA), a chronic disease characterized by degeneration of articular cartilage leading to pain and physical disability. Senescent chondrocytes are found in cartilage tissue isolated from patients undergoing joint replacement surgery, yet their role in disease pathogenesis is unknown. To test the idea that SnCs might play a causative role in OA, we used the p16-3MR transgenic mouse, which harbors a p16INK4a (Cdkn2a) promoter driving the expression of a fusion protein containing synthetic Renilla luciferase and monomeric red fluorescent protein domains, as well as a truncated form of herpes simplex virus 1 thymidine kinase (HSV-TK). This mouse strain allowed us to selectively follow and remove SnCs after anterior cruciate ligament transection (ACLT). We found that SnCs accumulated in the articular cartilage and synovium after ACLT, and selective elimination of these cells attenuated the development of post-traumatic OA, reduced pain and increased cartilage development. Intra-articular injection of a senolytic molecule that selectively killed SnCs validated these results in transgenic, non-transgenic and aged mice. Selective removal of the SnCs from in vitro cultures of chondrocytes isolated from patients with OA undergoing total knee replacement decreased expression of senescent and inflammatory markers while also increasing expression of cartilage tissue extracellular matrix proteins. Collectively, these findings support the use of SnCs as a therapeutic target for treating degenerative joint disease.