Roth D A, Longaker M T, McCarthy J G, Rosen D M, McMullen H F, Levine J P, Sung J, Gold L I
Institute of Reconstructive Plastic Surgery, New York University School of Medicine, New York, USA.
J Bone Miner Res. 1997 Mar;12(3):311-21. doi: 10.1359/jbmr.1997.12.3.311.
The mechanisms involved in normal cranial suture development and fusion as well as the pathophysiology of craniosynostosis, a premature fusion of the cranial sutures, are not well understood. Transforming growth factor-beta isoforms (TGF-beta 1, beta 2, and beta 3) are abundant in bone and stimulate calvarial bone formation when injected locally in vivo. To gain insight into the role of these factors in normal growth and development of cranial sutures and the possible etiology of premature cranial suture fusion, we examined the temporal and spatial expression of TGF-beta isoforms during normal cranial suture development in the rat. In the Sprague-Dawley rat, only the posterior frontal cranial suture undergoes fusion between 12 and 22 days of age, while all other cranial sutures remain patent. Therefore, immunohistochemical analysis of the fusing posterior frontal suture was compared with the patent sagittal suture at multiple time points from the fetus through adult. Whereas the intensity of immunostaining was the same in the posterior frontal and sagittal sutures in the fetal rat, there was increased immunoreactivity for TGF-beta isoforms in the actively fusing posterior frontal suture compared with the patent sagittal suture starting 2 days after birth and continuing until approximately 20 days. There were intensely immunoreactive osteoblasts present during fusion of the posterior frontal suture. In contrast, the patent sagittal suture was only slightly immunoreactive. A differential immunostaining pattern was observed among the TGF-beta isoforms; TGF-beta 2 was the most immunoreactive isoform and was also most strongly associated with osteoblasts adjacent to the dura and the margin of the fusing suture. Since the increased expression of TGF-beta 2 during suture fusion suggested a possible regulatory role, recombinant TGF-beta 2 was added directly to the posterior frontal and sagittal sutures in vivo to determine if suture fusion could be initiated. Exogenously added TGF-beta 2 stimulated fusion of the ectocranial surface of the posterior frontal suture. These data provide evidence for a regulatory role for these growth factors in cranial suture development and fusion. Additionally, the intense immunostaining for TGF-beta 2 in the dura mater underlying the fusing suture supports a role for the dura mater in suture fusion. It is possible that premature or excessive expression of these factors may be involved in the etiopathogenesis of craniosynostosis and that modulation of the growth factor profile at the suture site may have potential therapeutic value.
正常颅缝发育与融合所涉及的机制，以及颅缝早闭（一种颅缝过早融合）的病理生理学，目前尚未完全明确。转化生长因子-β亚型（TGF-β1、β2和β3）在骨骼中含量丰富，在体内局部注射时可刺激颅骨形成。为深入了解这些因子在颅缝正常生长发育中的作用以及颅缝过早融合的可能病因，我们研究了大鼠正常颅缝发育过程中TGF-β亚型的时空表达。在斯普拉格-道利大鼠中，仅额后颅缝在12至22日龄之间发生融合，而其他所有颅缝保持开放。因此，从胎儿期到成年期的多个时间点，对正在融合的额后颅缝与开放的矢状缝进行了免疫组织化学分析。在胎鼠中，额后颅缝和矢状缝的免疫染色强度相同，但从出生后2天开始，直至约20天，正在融合的额后颅缝中TGF-β亚型的免疫反应性相较于开放的矢状缝有所增加。在额后颅缝融合过程中存在强烈免疫反应性的成骨细胞。相比之下，开放的矢状缝仅有轻微的免疫反应性。在TGF-β亚型之间观察到了不同的免疫染色模式；TGF-β2是免疫反应性最强的亚型，并且与靠近硬脑膜和融合缝边缘的成骨细胞关联也最为紧密。由于在缝融合过程中TGF-β2表达增加提示了可能的调节作用，因此将重组TGF-β2直接添加到体内的额后颅缝和矢状缝中，以确定是否能启动缝融合。外源添加的TGF-β2刺激了额后颅缝颅外表面的融合。这些数据为这些生长因子在颅缝发育和融合中的调节作用提供了证据。此外，在融合缝下方硬脑膜中TGF-β2的强烈免疫染色支持了硬脑膜在缝融合中的作用。这些因子的过早或过度表达可能参与了颅缝早闭的发病机制，并且在缝部位调节生长因子谱可能具有潜在的治疗价值。
