Peptan Alexandra I, Lopez Aurora, Kopher Ross A, Mao Jeremy J
Department of Biomedical Engineering, Columbia University, College of Dental Medicine, New York, NY 10032, USA.
Bone. 2008 Feb;42(2):432-8. doi: 10.1016/j.bone.2007.05.014. Epub 2007 Jun 7.
Cranial vault and facial sutures interpose between mineralized bones of the skull, and may function analogously to appendicular and cranial base growth plates. However, unlike growth plates that are composed of chondrocyte lineage, cranial and facial sutures possess heterogeneous cell lineages such as mesenchymal cells, fibroblasts, and osteoblasts, in addition to vascular-derived cells. Despite recently intensified effort, the biological responses of intramembranous bone and sutures to mechanical loading are not well understood. This study was designed to investigate whether brief doses of tensile or compressive forces induce modeling and growth responses of intramembranous bone and sutures. In different groups of growing rabbits in vivo, cyclic tensile or compressive forces at 1 N and 8 Hz were applied to the maxilla for 20 min/day over 12 consecutive days. Computerized histomorphometric analyses revealed that the average sutural widths of both the premaxillomaxillary suture (PMS) and nasofrontal suture (NFS) loaded in either tension or compression were significantly higher than age- and sex-matched sham controls (P<0.01). The average cell densities of tension- or compression-loaded PMS and NFS were significantly higher than sham controls (P<0.01). The average osteoblast occupied sutural bone surface loaded under tension was significantly higher than that of sham control (P<0.05). Interestingly, tensile loading significantly reduced the average osteoclast surface, in comparison to sham control (P<0.05). For the NFS, tensile loading significantly increased the average osteoblast occupied sutural bone surface, in comparison with that of sham control (P<0.05). Also for the NFS suture, compression significantly reduced the average sutural osteoclast surface in comparison with sham control (P<0.05). Taken together, the present data suggest that high-frequency cyclic forces in either tension or compression induce modeling and growth changes in cranial sutures. Due to the structural complexity of cranial vault and facial sutures, either tensile or compressive forces likely are transmitted as shear stresses and upregulate genes and gene products responsible for sutural growth.
颅顶和面部缝线介于颅骨的矿化骨之间，其功能可能类似于四肢和颅底的生长板。然而，与由软骨细胞谱系组成的生长板不同，颅面缝线除了血管衍生细胞外，还拥有间充质细胞、成纤维细胞和成骨细胞等异质细胞谱系。尽管最近加大了研究力度，但膜内骨和缝线对机械负荷的生物学反应仍未得到充分了解。本研究旨在调查短时间的拉伸或压缩力是否会诱导膜内骨和缝线的塑形和生长反应。在不同组的生长兔体内，以1 N和8 Hz的频率对上颌施加周期性拉伸或压缩力，每天20分钟，持续12天。计算机化组织形态计量学分析显示，无论是拉伸还是压缩加载的前上颌缝（PMS）和鼻额缝（NFS）的平均缝线宽度均显著高于年龄和性别匹配的假手术对照组（P<0.01）。拉伸或压缩加载的PMS和NFS的平均细胞密度显著高于假手术对照组（P<0.01）。拉伸加载下成骨细胞占据的缝线骨表面平均面积显著高于假手术对照组（P<0.05）。有趣的是，与假手术对照组相比，拉伸加载显著降低了破骨细胞的平均表面面积（P<0.05）。对于NFS，与假手术对照组相比，拉伸加载显著增加了成骨细胞占据的缝线骨表面平均面积（P<0.05）。同样对于NFS缝线，与假手术对照组相比，压缩显著降低了缝线破骨细胞的平均表面面积（P<0.05）。综上所述，目前的数据表明，高频周期性拉伸或压缩力会诱导颅缝的塑形和生长变化。由于颅顶和面部缝线的结构复杂性，拉伸或压缩力可能都作为剪应力传递，并上调负责缝线生长的基因和基因产物。
