Department of Food Science and Biotechnology, Sungkyunkwan University, Suwon, Korea.
Nutr Res. 2013 Feb;33(2):162-70. doi: 10.1016/j.nutres.2012.11.006. Epub 2012 Dec 20.
Silk fibroins are biomaterials that have been applied to surgical sutures, drug delivery systems, food supplements, and tissue engineering. Studies have shown the antiadipogenic effects of silk proteins in 3T3-L1 cells and obese mice. Furthermore, other studies have shown that silk proteins increase osteogenic marker expression in osteoblast-like cells. Because osteogenic and adipogenic differentiation from common mesenchymal progenitor cells are often regulated reciprocally, we hypothesized that silk proteins would stimulate osteoblast differentiation. The objective of this study was to evaluate the effects of silk proteins on promoting osteoblast differentiation and identify the underlying mechanism. We showed that silk proteins dose dependently stimulated alkaline phosphatase (ALP) activity, osteoblast differentiation, and induced expression of osteoblast markers in C3H10T1/2 and M2-10B4 multipotent cells. In addition, silk proteins also induced the expression of osteoblast markers in primary rat bone marrow cells isolated from tibiae. Molecular studies showed that silk proteins suppressed the expression of Notch-activated genes and blocked activation of the Notch-specific reporter. Similarly, inhibiting Notch signaling with pharmacologic inhibitors and by small interfering RNA-mediated Notch1 silencing also induced ALP activity and messenger RNA expression. Finally, induction of ALP activity and messenger RNA expression by silk proteins was blunted in Notch1 knock-downed cells, further demonstrating Notch signaling as an important mediator for the pro-osteogenic effects of silk proteins. Taken together, our data suggest that silk proteins may serve as functional foods to promote bone healing and therapeutic interventions for bone fractures and osteoporosis.
丝素蛋白是一种生物材料，已被应用于手术缝线、药物输送系统、食品补充剂和组织工程。研究表明，丝蛋白在 3T3-L1 细胞和肥胖小鼠中具有抗脂肪生成作用。此外，其他研究表明，丝蛋白可增加成骨细胞样细胞中骨生成标志物的表达。因为成骨细胞和脂肪生成细胞从常见的间充质祖细胞分化通常是相互调节的，我们假设丝蛋白会刺激成骨细胞分化。本研究的目的是评估丝蛋白对促进成骨细胞分化的作用，并确定其潜在机制。我们表明，丝蛋白剂量依赖性地刺激碱性磷酸酶（ALP）活性、成骨细胞分化，并诱导 C3H10T1/2 和 M2-10B4 多能细胞中骨细胞标志物的表达。此外，丝蛋白还诱导从小鼠胫骨分离的原代骨髓细胞中骨细胞标志物的表达。分子研究表明，丝蛋白抑制 Notch 激活基因的表达，并阻断 Notch 特异性报告基因的激活。同样，用药理学抑制剂抑制 Notch 信号通路和通过小干扰 RNA 介导的 Notch1 沉默也诱导了 ALP 活性和信使 RNA 的表达。最后，在 Notch1 敲低细胞中，丝蛋白诱导 ALP 活性和信使 RNA 表达的作用减弱，进一步证明 Notch 信号通路是丝蛋白促成骨作用的重要介导因子。总之，我们的数据表明，丝蛋白可能作为功能性食品，促进骨愈合，并对骨折和骨质疏松症进行治疗干预。
