Targeted conditional collagen XII deletion alters tendon function.
Targeted conditional collagen XII deletion alters tendon function.
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DOI：
10.1016/j.mbplus.2022.100123
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发表时间：
2022-12
影响因子：
--
通讯作者：
Birk, David E
中科院分区：
文献类型：
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作者：
Fung, Ashley;Sun, Mei;Soslowsky, Louis J;Birk, David E
建立条件性Col 12 a1缺失小鼠模型并进行表征。条件模型用于将Col 12 a1缺失靶向肌腱。靶向肌腱具有接近基线的Col 12 a1和胶原XII表达。肌腱中col 12 a1缺乏改变肌腱功能。胶原蛋白XII决定肌腱功能的内在作用。胶原蛋白XII是具有中断三螺旋的原纤维相关胶原蛋白（FACIT）。这种非纤维胶原是由三条α1（XII）链组装成胶原分子的同源三聚体，具有C末端胶原结构域和大的N末端非胶原结构域。在肌腱发育和生长过程中，胶原XII广泛表达于整个细胞外基质中，并在肌腱细胞周围的细胞周富集。在全球Col 12 a1-/-敲除模型中的肌腱表现出破坏的原纤维和纤维结构以及紊乱的腱细胞组织，突出了胶原蛋白XII在决定肌腱结构和功能中的关键调节作用。然而，在胶原蛋白XII敲除模型中，肌肉和骨骼也受到影响。因此，由于骨骼和肌肉的参与，可能会在整体敲除中发生对肌腱的继发性影响。全局敲除不允许定义涉及肌腱中的胶原蛋白XII的内在机制与涉及肌肉和骨骼的外在作用。为了解决这一限制，我们创建了一个条件Col 12 a1-null小鼠模型，并进行了表征，以允许对Col 12 a1表达进行空间和时间操作。通过将条件性Col 12 a1 flox/flox小鼠与Scleraxis-Cre（Scx-Cre）小鼠交配，将胶原蛋白XII敲除靶向肌腱，以产生肌腱特异性Col 12 a1-null小鼠系，Col 12 a1 Δten/Δten。Col 12 a1 Δten/Δten小鼠趾长屈肌腱（FDL）的mRNA和蛋白表达均降至接近基线水平。胶原蛋白XII的免疫定位显示，在肌腱适当的反应性的情况下，但有反应性周围的肌腱周围的细胞。这支持腱细胞中的靶向敲除，而来自非腱谱系的腱周细胞未被靶向并保留胶原蛋白XII表达。肌腱靶向的Col 12 a1 Δten/Δten小鼠前肢握力显著降低，步态改变，生物力学特性显著降低。而观察到的肌腱模量的降低表明，在没有Col 12 a1表达的情况下，肌腱材料特性的差异是功能缺陷的基础。总之，这些发现表明胶原蛋白XII对功能性肌腱的发育至关重要的内在作用。
A conditional Col12a1 deletion mouse model was created and characterized. The conditional model was used to target the Col12a1 deletion to tendons. Targeted tendons had near baseline Col12a1 and collagen XII expression. Col12a1 deficiency in tendons alters tendon function. Intrinsic roles for collagen XII determining tendon function were suggested. Collagen XII is a fibril-associated collagen with interrupted triple helices (FACIT). This non-fibrillar collagen is a homotrimer composed of three α1(XII) chains assembled into a collagenous molecule with a C terminal collagenous domain and a large N terminal non-collagenous domain. During tendon development and growth, collagen XII is broadly expressed throughout the extracellular matrix and enriched pericellularly around tenocytes. Tendons in a global Col12a1-/- knockout model demonstrated disrupted fibril and fiber structure and disordered tenocyte organization, highlighting the critical regulatory roles of collagen XII in determining tendon structure and function. However, muscle and bone also are affected in the collagen XII knockout model. Therefore, secondary effects on tendon due to involvement of bone and muscle may occur in the global knockout. The global knockout does not allow the definition of intrinsic mechanisms involving collagen XII in tendon versus extrinsic roles involving muscle and bone. To address this limitation, we created and characterized a conditional Col12a1-null mouse model to permit the spatial and temporal manipulation of Col12a1 expression. Collagen XII knockout was targeted to tendons by breeding conditional Col12a1flox/flox mice with Scleraxis-Cre (Scx-Cre) mice to yield a tendon-specific Col12a1-null mouse line, Col12a1Δten/Δten. Both mRNA and protein expression in Col12a1Δten/Δten mice decreased to near baseline levels in flexor digitorum longus tendons (FDL). Collagen XII immuno-localization revealed an absence of reactivity in the tendon proper, but there was reactivity in the cells of the surrounding peritenon. This supports a targeted knockout in tenocytes while peritenon cells from a non-tendon lineage were not targeted and retained collagen XII expression. The tendon-targeted, Col12a1Δten/Δten mice had significantly reduced forelimb grip strength, altered gait and a significant decrease in biomechanical properties. While the observed decrease in tendon modulus suggests that differences in tendon material properties in the absence of Col12a1 expression underlie the functional deficiencies. Together, these findings suggest an intrinsic role for collagen XII critical for development of a functional tendon.