Up-regulation of site-specific remodeling, without accumulation of microcracking and loss of osteocytes
Up-regulation of site-specific remodeling, without accumulation of microcracking and loss of osteocytes
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DOI：
10.1016/j.bone.2004.12.016
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发表时间：
2005-07-01
期刊：
影响因子：
4.1
通讯作者：
Muir, P
中科院分区：
文献类型：
--
作者：
Gómez, TMD;Barrett, JG;Muir, P
在日常活动中，骨骼的功能适应通常会保护骨骼免受骨折的伤害。微裂纹的积累和骨细胞的丢失与骨的靶向(修复性)重建的调节和启动有关，在某些情况下，还与疲劳或应力性骨折的发展有关。对纯种赛马第三掌骨(Mc-III)中骨干背侧皮质进行碱性品红染色，制作钙化切片，进行组织学研究。纯种赛马是一名极端运动员，他的Mc-III骨骼在训练和比赛中经历了特别高的周期性应变。一组非运动马也被包括在实验中。量化下列变量：激活频率(Ac.f)；骨形成率(BFR)；吸收空间密度(Rs.N/T.Ar)；微裂纹密度(Cr.Dn)；微裂纹平均长度(Cr.Le)；微裂纹表面密度(Cr.S.Dn)；骨细胞密度(Ot.N/T.Ar；Ot.N/B.Ar)；骨体积分数(B.Ar/T.Ar)。使用数学算法估计Ac.f和BFR。使用共聚焦显微镜，检查骨骼的细微裂纹、弥漫性基质损伤和骨细胞合体的破坏。两组的Cr.Dn(#/mm(2))均较低(赛马和非赛马分别为0.022+/-0.008和0.013+/-0.006)。Cr.Dn与Ot.N/T.Ar、Ot.N/B.Ar、B.Ar/T.Ar、Ot.N/B.Ar、Ot.N/B.Ar、重构(Ac.f，Rs.N/T.Ar)、Ot.N/T.Ar、Ot.N/B.Ar无显著相关性。赛马的Mc-III背侧皮质有强烈的重构(Ac.f 12.8+/-7.4#/mm(2)/年；BFR 31.5+/-15.6%；Rs.N/T.Ar 0.19+/-0.09#/mm(2))，且显著高于非赛马。总体而言，重构与Cr.Dn呈弱相关(r(2)=0.15，P<；0.05)。明场显微镜无法检测到的细微基质损伤，在纯种骨的吸收间隙附近尤其明显。在非运动马中，骨水泥线和间质碎片相关的骨细胞树突状细胞突起的破坏更为明显。综上所述，这些发现表明，在高应变骨骼部位的骨功能适应过程中，部位特异性(靶向性)的重塑诱导并不依赖于微裂纹的积累或骨细胞的丢失。我们假设，运动能力可以通过不涉及经典线性微裂纹的途径直接影响这位极端运动员的骨转换。(C)2005 Elsevier Inc.保留所有权利。
Functional adaptation of bone normally protects the skeleton from fracture during daily activity. Accumulation of microcracking and loss of osteocytes have been implicated in the regulation and initiation of targeted (reparative) remodeling of bone and, in certain situations, the development of fatigue or stress fracture. We performed a histologic study of the dorsal cortex of the mid-diaphysis of the third metacarpal (Mc-III) bone of Thoroughbred racehorses after bones were bulk-stained in basic fuchsin and transverse calcified sections were prepared. The Thoroughbred racehorse is an extreme athlete whose Mc-III bone experiences particularly high cyclic strains during training and racing. A group of non-athletic horses was also included in the experiment. The following variables were quantified: activation frequency (Ac.f); bone formation rate (BFR); resorption space density (Rs.N/T.Ar); microcrack density (Cr.Dn); microcrack mean length (Cr.Le); microcrack surface density (Cr.S.Dn); osteocyte density (Ot.N/T.Ar; Ot.N/B.Ar); and bone volume fraction (B.Ar/T.Ar). Ac.f and BFR were estimated using a mathematical algorithm. Using confocal microscopy, bones were examined for fine microcracks, diffuse matrix injury, and disruption of the osteocyte syncytium. Low values for Cr.Dn (#/mm(2)) were found in both groups (0.022 +/- 0.008 and 0.013 +/- 0.006 for racing Thoroughbreds and non-athletic horses, respectively). There was no significant relationship between Cr.Dn and Ot.N/T.Ar; Ot.N/B.Ar, B.Ar/T.Ar, and Ot.N/T.Ar; Ot.N/B.Ar, and remodeling (Ac.f, Rs.N/T.Ar) and Ot.N/T.Ar; Ot.N/B.Ar. Intense remodeling of the Mc-III dorsal cortex was found in the racing Thoroughbreds (Ac.f 12.8 +/- 7.4 #/mm(2)/year; BFR 31.5 +/- 15.6%; Rs.N/T.Ar 0.19 +/- 0.09 #/mm(2)) and was significantly increased compared with non-athletic horses. Overall, remodeling was weakly correlated with Cr.Dn (r(2) = 0.15, P < 0.05). Subtle matrix injury, not detectable by bright-field microscopy, was particularly evident adjacent to resorption spaces in Thoroughbred bone. In non-athletic horses, disruption of the dendritic cell processes of osteocytes associated with cement lines and interstitial fragments was more evident. Taken together, these findings suggest that site-specific (targeted) induction of remodeling during functional adaptation of bone in a high-strain skeletal site is not dependent on accumulation of microcracking or loss of osteocytes. We hypothesize that athleticism can directly influence bone turnover in this extreme athlete through pathways that do not involve classical linear microcracks. (C) 2005 Elsevier Inc. All rights reserved.