Effect of grafting BMP2-derived peptide to nanoparticles on osteogenic and vasculogenic expression of stromal cells.

Bone morphogenetic protein-2 (BMP2) plays a major role in initiating the cascade of osteogenesis. However, high doses of exogenous BMP2 coupled with diffusion away from the intended site cause adverse side effects. An alternative is to use biodegradable polymeric nanoparticles (NPs) grafted with peptides of the active domains of BMP2. NPs present a multivalent form of the peptide for stronger interaction with cell surface receptors, leading to a stronger activation of osteogenic signaling pathways. The objective of this work was to compare osteogenic activity of the BMP2 peptide (BMP2Pe), corresponding to residues 73–92 of BMP2 protein (BMP2Pr), grafted to biodegradable NPs with that of BMP2 protein (BMP2Pr). BMP2Pe was functionalized with a cysteine residue and grafted to poly(lactide fumarate) and poly(lactide-co-ethylene oxide fumarate) (PLAF/PLEOF) NPs via a thioether link. The calcium content of bone marrow stromal (BMS) cells cultured in osteogenic media supplemented with BMP2 peptide/protein grafted NPs (BMP2Pe-gNP and BMP2Pr-gNP) was slightly higher than other BMP2 treated groups, but all osteogenic groups showed similar levels of mineralization after 21 days. The expression pattern of master transcription factors Dlx5 and Runx2 indicated that BMP2 protein induced a faster osteogenic signaling than the BMP peptide. The expression level of Osteopontin, Osteocalcin, and PECAM-1 in the NP grafted BMP2 groups was significantly higher than those of ungrafted BMP2Pr and BMP2Pe groups, which may be due to a more effective presentation of the peptide/protein to cell surface receptors, thus leading to a stronger interaction of the peptide/protein with clustered cell surface receptors.

骨形态发生蛋白 - 2（BMP2）在启动成骨级联反应中起主要作用。然而，高剂量的外源性BMP2加上从预期部位扩散开来，会导致不良副作用。一种替代方法是使用接枝有BMP2活性结构域肽段的可生物降解聚合物纳米颗粒（NPs）。纳米颗粒呈现出肽的多价形式，能与细胞表面受体更强地相互作用，从而更强烈地激活成骨信号通路。本研究的目的是比较接枝到可生物降解纳米颗粒上的BMP2肽（BMP2Pe，对应BMP2蛋白73 - 92位氨基酸残基）与BMP2蛋白（BMP2Pr）的成骨活性。BMP2Pe通过半胱氨酸残基进行功能化修饰，并通过硫醚键接枝到聚（富马酸丙交酯）和聚（丙交酯 - 共 - 环氧乙烷富马酸酯）（PLAF/PLEOF）纳米颗粒上。在添加了BMP2肽/蛋白接枝纳米颗粒（BMP2Pe - gNP和BMP2Pr - gNP）的成骨培养基中培养的骨髓基质（BMS）细胞的钙含量略高于其他BMP2处理组，但21天后所有成骨组的矿化水平相似。主要转录因子Dlx5和Runx2的表达模式表明，BMP2蛋白诱导成骨信号的速度比BMP肽更快。在纳米颗粒接枝BMP2的组中，骨桥蛋白、骨钙素和PECAM - 1的表达水平显著高于未接枝的BMP2Pr和BMP2Pe组，这可能是由于肽/蛋白能更有效地呈递给细胞表面受体，从而导致肽/蛋白与聚集的细胞表面受体之间更强的相互作用。