Bain Jennifer L, Culpepper Bonnie K, Reddy Michael S, Bellis Susan L
Int J Oral Maxillofac Implants. 2014 Nov-Dec;29(6):1437-45. doi: 10.11607/jomi.3759.
Allografts, xenografts, and alloplasts are commonly used in craniofacial medicine as alternatives to autogenous bone grafts; however, these materials lack important bone-inducing proteins. A method for enhancing the osteoinductive potential of these commercially available materials would provide a major clinical advance. In this study, a calcium-binding domain, polyglutamate, was added to an osteoinductive peptide derived from collagen type I, Asp-Gly-Glu-Ala (DGEA), to anchor the peptide onto four different materials: freeze-dried bone allograft (FDBA); anorganic bovine bone (ABB); β-tricalcium phosphate (β-TCP); and a calcium sulfate bone cement (CaSO4). The authors also examined whether peptide binding and retention could be tuned by altering the number of glutamate residues within the polyglutamate domain.
DGEA or DGEA modified with diglutamate (E2DGEA), tetraglutamate (E4DGEA), or heptaglutamate (E7DGEA) were evaluated for binding and release to the grafting materials. Peptides were conjugated with a fluorescein isothiocyanate (FITC) tag to allow monitoring by fluorescent microscopy or through measurements of solution fluorescence. In vivo retention was evaluated by implanting graft materials coated with FITC-peptides into rat subcutaneous pouches.
Significantly more peptide was loaded onto the four graft materials as the number of glutamates increased, with E7DGEA exhibiting the greatest binding. There was also significantly greater retention of peptides with longer glutamate domains following a 3-day incubation with agitation. Importantly, E7DGEA peptides remained on the grafts after a 2-month implantation into skin pouches, a sufficient interval to influence bony healing.
Variable-length polyglutamate domains can be added to osteoinductive peptides to control the amount of peptide bound and rate of peptide released. The lack of methods for tunable coupling of biologics to commercial graft sources has been a major barrier toward developing materials that approach the clinical efficacy of autogenous bone. Modification of osteoinductive factors with polyglutamate domains constitutes a technically straightforward and cost-effective strategy for enhancing osteoinductivity of diverse graft products.
同种异体移植物、异种移植物和异质生物材料在颅面医学中常用作自体骨移植的替代物；然而，这些材料缺乏重要的骨诱导蛋白。一种增强这些市售材料骨诱导潜力的方法将带来重大的临床进展。在本研究中，将一个钙结合结构域聚谷氨酸添加到源自I型胶原的骨诱导肽天冬氨酸-甘氨酸-谷氨酸-丙氨酸（DGEA）上，以将该肽锚定到四种不同的材料上：冻干同种异体骨（FDBA）；无机牛骨（ABB）；β-磷酸三钙（β-TCP）；以及硫酸钙骨水泥（CaSO4）。作者还研究了是否可以通过改变聚谷氨酸结构域内谷氨酸残基的数量来调节肽的结合和保留。
评估DGEA或用二谷氨酸（E2DGEA）、四谷氨酸（E4DGEA）或七谷氨酸（E7DGEA）修饰的DGEA与移植材料的结合和释放情况。肽与异硫氰酸荧光素（FITC）标签偶联，以便通过荧光显微镜或溶液荧光测量进行监测。通过将涂有FITC肽的移植材料植入大鼠皮下袋来评估体内保留情况。
随着谷氨酸数量的增加，加载到四种移植材料上的肽显著增多，E7DGEA表现出最大的结合能力。在搅拌孵育3天后，具有更长谷氨酸结构域的肽也有显著更高的保留率。重要的是，E7DGEA肽在植入皮肤袋2个月后仍保留在移植物上，这是一个足以影响骨愈合的时间间隔。
可变长度的聚谷氨酸结构域可以添加到骨诱导肽中，以控制肽的结合量和释放速率。缺乏将生物制剂与商业移植源进行可调偶联的方法一直是开发接近自体骨临床疗效材料的主要障碍。用聚谷氨酸结构域修饰骨诱导因子是一种技术简单且经济有效的策略，可增强多种移植产品的骨诱导性。
