Department of Orthopedics and Rheumatology, University Hospital Marburg, Marburg, Germany.
PLoS One. 2011;6(9):e25462. doi: 10.1371/journal.pone.0025462. Epub 2011 Sep 28.
Adequate migration and differentiation of mesenchymal stem cells is essential for regeneration of large bone defects. To achieve this, modern graft materials are becoming increasingly important. Among them, electrospun nanofiber scaffolds are a promising approach, because of their high physical porosity and potential to mimic the extracellular matrix (ECM).
The objective of the present study was to examine the impact of electrospun PLLA nanofiber scaffolds on bone formation in vivo, using a critical size rat calvarial defect model. In addition we analyzed whether direct incorporation of bone morphogenetic protein 2 (BMP-2) into nanofibers could enhance the osteoinductivity of the scaffolds. Two critical size calvarial defects (5 mm) were created in the parietal bones of adult male Sprague-Dawley rats. Defects were either (1) left unfilled, or treated with (2) bovine spongiosa, (3) PLLA scaffolds alone or (4) PLLA/BMP-2 scaffolds. Cranial CT-scans were taken at fixed intervals in vivo. Specimens obtained after euthanasia were processed for histology, histomorphometry and immunostaining (Osteocalcin, BMP-2 and Smad5).
PLLA scaffolds were well colonized with cells after implantation, but only showed marginal ossification. PLLA/BMP-2 scaffolds showed much better bone regeneration and several ossification foci were observed throughout the defect. PLLA/BMP-2 scaffolds also stimulated significantly faster bone regeneration during the first eight weeks compared to bovine spongiosa. However, no significant differences between these two scaffolds could be observed after twelve weeks. Expression of osteogenic marker proteins in PLLA/BMP-2 scaffolds continuously increased throughout the observation period. After twelve weeks osteocalcin, BMP-2 and Smad5 were all significantly higher in the PLLA/BMP-2 group than in all other groups.
Electrospun PLLA nanofibers facilitate colonization of bone defects, while their use in combination with BMP-2 also increases bone regeneration in vivo and thus combines osteoconductivity of the scaffold with the ability to maintain an adequate osteogenic stimulus.
间充质干细胞的充分迁移和分化对于大骨缺损的再生至关重要。为此，现代移植物材料变得越来越重要。其中，静电纺丝纳米纤维支架是一种很有前途的方法，因为它们具有高物理孔隙率和模拟细胞外基质（ECM）的潜力。
本研究的目的是使用大鼠颅骨临界大小缺损模型，研究静电纺丝 PLLA 纳米纤维支架对体内骨形成的影响。此外，我们还分析了将骨形态发生蛋白 2（BMP-2）直接掺入纳米纤维中是否可以增强支架的成骨活性。在成年雄性 Sprague-Dawley 大鼠的顶骨上创建了两个临界大小的颅骨缺损（5 毫米）。缺损要么（1）不填充，要么用（2）牛松质骨、（3）PLLA 支架或（4）PLLA/BMP-2 支架处理。在体内以固定间隔进行颅 CT 扫描。安乐死后获得的标本进行组织学、组织形态计量学和免疫染色（骨钙蛋白、BMP-2 和 Smad5）。
植入后 PLLA 支架被细胞很好地定植，但仅表现出边缘骨化。PLLA/BMP-2 支架显示出更好的骨再生，在整个缺损中观察到几个骨化焦点。与牛松质骨相比，PLLA/BMP-2 支架在前 8 周也能更快地刺激骨再生。然而，在 12 周后，这两种支架之间没有观察到显著差异。在整个观察期间，PLLA/BMP-2 支架中的成骨标记蛋白表达持续增加。12 周后，PLLA/BMP-2 组的骨钙蛋白、BMP-2 和 Smad5 均显著高于其他组。
静电纺丝 PLLA 纳米纤维有助于骨缺损的定植，而与 BMP-2 联合使用也增加了体内的骨再生，从而将支架的骨传导性与维持足够的成骨刺激能力相结合。
