Stanford, Calif. From the Hagey Laboratory for Pediatric Regenerative Medicine, Division of Plastic and Reconstructive Surgery, Department of Surgery, Stanford University School of Medicine.
Plast Reconstr Surg. 2011 Feb;127(2):595-602. doi: 10.1097/PRS.0b013e3181fed60d.
An understanding of the molecular mechanisms controlling bone formation is central to skeletal tissue engineering efforts. The observation that immature animals are able to heal calvarial defects while adult animals are not has proven to be a useful tool for examining these mechanisms. Thus, the authors compared expression of sclerostin, a bone inhibitor, between the calvariae of juvenile and adult mice.
Parietal bone was harvested from juvenile (6-day-old; n = 20) and adult (60-day-old; n = 20) mice. Sclerostin transcript and protein levels were compared between the parietal bone of juvenile and adult mice using polymerase chain reaction, Western blotting, and immunohistochemistry. Finally, osteoblasts from the parietal bone of juvenile and adult mice were harvested and cultured under osteogenic differentiation conditions with and without recombinant sclerostin (200 ng/ml). Terminal osteogenic differentiation was assessed at 21 days with alizarin red staining.
Polymerase chain reaction, Western blot analysis, and immunohistochemistry all confirmed greater expression of sclerostin in the parietal bone of adult mice when compared with that of juvenile mice. Osteoblasts, whether from juvenile or adult parietal bones, demonstrated reduced capacity for osteogenic differentiation when exposed to recombinant sclerostin.
Given the role of sclerostin in inhibiting bone formation, the authors' findings suggest that differences in expression levels of sclerostin may play a role in the differential regenerative capacity of calvariae from juvenile and adult animals. These findings suggest it as a potential target to abrogate in future tissue engineering studies.
理解控制骨形成的分子机制是骨骼组织工程努力的核心。观察到未成年动物能够修复颅骨缺损，而成年动物则不能，这一观察结果已被证明是研究这些机制的有用工具。因此，作者比较了幼年（6 日龄；n = 20）和成年（60 日龄；n = 20）小鼠颅骨中的骨抑制素 sclerostin 的表达。
从幼年（6 日龄；n = 20）和成年（60 日龄；n = 20）小鼠的顶骨中采集顶骨。使用聚合酶链反应、Western blot 和免疫组织化学比较幼年和成年小鼠顶骨中的 sclerostin 转录本和蛋白水平。最后，从幼年和成年小鼠的顶骨中采集成骨细胞，并在成骨分化条件下培养，有和没有重组 sclerostin（200 ng/ml）。用茜素红染色在第 21 天评估终末成骨分化。
聚合酶链反应、Western blot 分析和免疫组织化学均证实成年小鼠顶骨中 sclerostin 的表达明显高于幼年小鼠。暴露于重组 sclerostin 时，来自幼年或成年顶骨的成骨细胞的成骨分化能力降低。
鉴于 sclerostin 在抑制骨形成中的作用，作者的发现表明 sclerostin 表达水平的差异可能在幼年和成年动物颅骨的再生能力差异中起作用。这些发现表明它可能成为未来组织工程研究中消除的潜在目标。
