Effect of Age and Proteoglycan Deficiency on Collagen Fiber Re-Alignment and Mechanical Properties in Mouse Supraspinatus Tendon
Effect of Age and Proteoglycan Deficiency on Collagen Fiber Re-Alignment and Mechanical Properties in Mouse Supraspinatus Tendon
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DOI：
10.1115/1.4023234
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发表时间：
2013-02-01
影响因子：
1.7
通讯作者：
Soslowsky, Louis J.
中科院分区：
文献类型：
--
作者：
Connizzo, Brianne K.;Sarver, Joseph J.;Soslowsky, Louis J.
胶原纤维重新排列是肌腱响应负荷的一种机制。当肌腱结构改变时，例如在自然衰老过程中或基质蛋白（例如蛋白多糖表达）的改变，重新排列就会改变。虽然最近在开发过程中研究了重新排列和机械性能的变化，但尚未在（1）老化肌腱或（2）缺乏关键蛋白聚糖的情况下进行研究。在野生型 (WT)、核心蛋白聚糖缺失 (Dcn(-/-)) 和双糖链蛋白聚糖缺失 (Bgn(-/-)) 小鼠的三种不同年龄（90 天、300 天和 570 天）的小鼠冈上肌腱的插入位点和中质中，通过拉伸机械测试对胶原纤维重新排列和相应的机械性能进行量化。 WT 和 Dcn(-/-) 肌腱的松弛百分比随着年龄的增长而显着降低，但 Bgn(-/-) 肌腱的松弛百分比却没有显着降低。插入部位的线性模量随年龄的变化而变化，其中Bgn(-/-)肌腱中300天组大于90天和570天组，Dcn(-/-)肌腱中90天组小于300天和570天组。然而，没有发现 WT 肌腱的模量随着年龄的变化而变化。随着年龄的增长，WT 和 Bgn(-/-) 肌腱的中质纤维最初不太对齐。 WT 肌腱的重新排列随着年龄的增长而显着改变，老年组在机械测试中对负载做出了反应。这也出现在 Dcn(-/-) 中间物质和 Bgn(-/-) 插入中，但没有出现在其他位置。尽管一些研究发现 WT 机械性能随年龄的变化而变化，但本研究并不支持这些发现。然而，它确实显示出随着年龄的增长，两个位置的纤维重新排列发生了变化，这表明肌腱在以后的年龄中响应负荷的能力出现了下降。然而，在无蛋白聚糖的肌腱中，机械性能发生了变化，仅伴随着位置依赖性的重新排列变化，这表明这些分子在加载中具有位点特异性作用。最后，机械性能的变化并未与重新对准的变化同时发生，这表明仅典型的机械性能测量不足以描述结构改变如何影响肌腱对负载的响应。
Collagen fiber realignment is one mechanism by which tendon responds to load. Re-alignment is altered when the structure of tendon is altered, such as in the natural process of aging or with alterations of matrix proteins, such as proteoglycan expression. While changes in re-alignment and mechanical properties have been investigated recently during development, they have not been studied in (1) aged tendons, or (2) in the absence of key proteoglycans. Collagen fiber re-alignment and the corresponding mechanical properties are quantified throughout tensile mechanical testing in both the insertion site and the midsubstance of mouse supraspinatus tendons in wild type (WT), decorin-null (Dcn(-/-)), and biglycan-null (Bgn(-/-)) mice at three different ages (90 days, 300 days, and 570 days). Percent relaxation was significantly decreased with age in the WT and Dcn(-/-) tendons, but not in the Bgn(-/-) tendons. Changes with age were found in the linear modulus at the insertion site where the 300 day group was greater than the 90 day and 570 day group in the Bgn(-/-) tendons and the 90 day group was smaller than the 300 day and 570 day groups in the Dcn(-/-) tendons. However, no changes in modulus were found across age in WT tendons were found. The midsubstance fibers of the WT and Bgn(-/-) tendons were initially less aligned with increasing age. The re-alignment was significantly altered with age in the WT tendons, with older groups responding to load later in the mechanical test. This was also seen in the Dcn(-/-) midsubstance and the Bgn(-/-) insertion, but not in the other locations. Although some studies have found changes in the WT mechanical properties with age, this study did not support those findings. However, it did show fiber re-alignment changes at both locations with age, suggesting a breakdown of tendon's ability to respond to load in later ages. In the proteoglycan-null tendons however, there were changes in the mechanical properties, accompanied only by location-dependent re-alignment changes, suggesting a site-specific role for these molecules in loading. Finally, changes in the mechanical properties did not occur in concert with changes in re-alignment, suggesting that typical mechanical property measurements alone are insufficient to describe how structural alterations affect tendon's response to load.