Institute of Biomaterials and Biomedical Engineering, University of Toronto, ON, Canada.
J Anat. 2012 Dec;221(6):577-89. doi: 10.1111/j.1469-7580.2012.01537.x. Epub 2012 Jul 3.
Current surgical treatments for degenerative intervertebral disc disease do not restore full normal spinal movement. Tissue engineering a functional disc replacement may be one way to circumvent this limitation, but will require an integration of the different tissues making up the disc for this approach to be successful. Hence, an in-depth characterization of the native tissue interfaces, including annulus insertion into bone is necessary, as knowledge of this interface is limited. The objective of this study was to characterize the annulus fibrosus-vertebral bone (AF-VB) interface in immature (6-9 months old) and mature (18-24 months old) bovine discs, as well as to define these structures for normal adult human (22 and 45 years old) discs. Histological assessment showed that collagen fibers in the inner annulus, which are predominantly type II collagen, all appear to insert into the mineralized endplate zone. In contrast, some of the collagen fibers of the outer annulus, predominantly type I collagen, insert into this endplate, while other fibers curve laterally, at an ∼ 90° angle, to the outer aspect of the bone, and merge with the periosteum. This is seen in both human and bovine discs. Where the AF inserts into the calcified zone of the AF-VB interface, it passes through a chondroid region, rich in type II collagen and proteoglycans. Annulus cells (elongated cells that are not surrounded by proteoglycans) are present at this interface. This cartilage zone is evident in both human and bovine discs. Type X collagen and alkaline phosphatase are localized to the interface region. Age-associated differences in bovine spines are observed when examining the interface thickness and the matrix composition of the cartilaginous endplate, as well as the thickness of the mineralized endplate. These findings will assist with the design of the AF-VB interface in the tissue engineered disc.
目前针对退行性椎间盘疾病的外科治疗并不能完全恢复正常的脊柱运动。组织工程学方法构建功能性椎间盘置换可能是解决这一限制的方法之一，但需要整合构成椎间盘的不同组织，才能使这种方法成功。因此，深入了解天然组织界面，包括纤维环与骨的连接界面，是非常必要的，因为目前对这一界面的了解还很有限。本研究的目的是描述未成熟（6-9 月龄）和成熟（18-24 月龄）牛椎间盘纤维环-椎体骨（AF-VB）界面的特征，并定义正常成人（22 岁和 45 岁）椎间盘的这些结构。组织学评估显示，内层纤维环中的胶原纤维（主要为 II 型胶原）似乎全部插入矿化终板区。相比之下，外层纤维环的一些胶原纤维（主要为 I 型胶原）插入该终板，而其他纤维则以约 90°的角度向骨的外侧弯曲，并与骨膜融合。这在人和牛的椎间盘都可见到。纤维环插入 AF-VB 界面的钙化区时，穿过富含 II 型胶原和蛋白聚糖的软骨样区域。在该界面处存在纤维环细胞（未被蛋白聚糖包围的长形细胞）。在人和牛的椎间盘都可见到这种软骨区。X 型胶原和碱性磷酸酶定位于该界面区域。在研究牛脊柱的界面厚度、软骨终板的基质组成以及矿化终板的厚度时，观察到与年龄相关的差异。这些发现将有助于设计组织工程椎间盘的 AF-VB 界面。
