Oral and Dental Research Division, Department of Surgery and Medicine, National Research Center, Cairo, Egypt.
Tissue Eng Part A. 2012 Mar;18(5-6):665-75. doi: 10.1089/ten.TEA.2011.0148. Epub 2011 Dec 5.
The ability of recombinant human bone morphogenetic protein 2 on absorbable collagen sponge (rhBMP2/ACS) to regenerate bone in segmental defect has been well characterized. However, clinical results of rhBMP2/ACS constructs in secondary reconstruction of large mandibular and craniofacial defects have not been consistent. We hypothesized that rhBMP2 delivery triggers an endogenous response in the soft tissues surrounding the defect, in the form of expression of BMP2 and vascular endothelial growth factor (VEGF). Such osteogenic response will occur only after immediate, as opposed to delayed, rhBMP2 delivery, suggesting a new explanation to the difference in bone regeneration between the two settings. A 35-mm segmental bone and periosteum defect was created on one side of the mandible in 16 dogs divided in three groups. Group 1 (Gp1, n=6) ACS was loaded with 8 mL of rhBMP2 (0.2 mg/mL). In Gp2 (n=5) the same dose of rhBMP2/ACS was delivered into the defect 4 weeks after surgery. In Gp3 (control; n=5) the defect was reconstructed using ACS loaded with 8 mL of buffer only (devoid of rhBMP2). Tissues were collected after 12 weeks of reconstruction in all groups. Direct measurement of physical dimensions of regenerates and bone morphometry was performed to evaluate bone regeneration. The mRNA expression of both BMP2 and VEGF in the soft tissue surrounding the defect was evaluated using real-time quantitative PCR. Both BMP2 and VEGF proteins were quantified in immunostained sections. Immunoflurescence colocalization of BMP2 and acetylated low density lipoprotein (AcLDL) was done to detect the source of BMP2. Immediate delivery yielded better bone regeneration. Both BMP2 and VEGF mRNA expression was upregulated only in Gp1 (+7.3, p=0.001; +1.53, p=0.001, respectively). BMP2 protein was significantly higher in the immediate reconstruction group; however, VEGF protein was undetected in the examined sections. Immediate delivery of rhBMP2 seemed to induce endogenous release of BMP2 from the surrounding soft tissues, an effect that was lacking in delayed delivery and may explain the variability of clinical results associated with BMP2 use. Colocalization of BMP2 and endothelial cells (ECs) suggested that ECs could be the source of endogenous BMP2.
重组人骨形态发生蛋白 2 （rhBMP2）在可吸收胶原海绵上（rhBMP2/ACS）促进节段性骨缺损再生的能力已得到充分证实。然而，rhBMP2/ACS 构建物在大的下颌骨和颅面缺损的二次重建中的临床结果并不一致。我们假设 rhBMP2 的递送会以 BMP2 和血管内皮生长因子（VEGF）的表达形式触发缺损周围软组织中的内源性反应。只有在即刻而不是延迟递送 rhBMP2 后，才会发生这种成骨反应，这为两种情况下骨再生的差异提供了新的解释。16 只狗的一侧下颌骨上制作了 35mm 的节段性骨和骨膜缺损，分为三组。第 1 组（Gp1，n=6）将 8ml 载有 0.2mg/ml rhBMP2 的 ACS 加载到缺损中。第 2 组（Gp2，n=5）在手术后 4 周将相同剂量的 rhBMP2/ACS 递送到缺损中。第 3 组（对照组；n=5）仅使用载有 8ml 缓冲液的 ACS 重建缺损（不含 rhBMP2）。所有组均在重建后 12 周采集组织。直接测量再生物的物理尺寸和骨形态计量学来评估骨再生。使用实时定量 PCR 评估缺损周围软组织中 BMP2 和 VEGF 的 mRNA 表达。在免疫染色切片中定量 BMP2 和乙酰化低密度脂蛋白（AcLDL）的蛋白。免疫荧光共定位 BMP2 和乙酰化低密度脂蛋白（AcLDL）以检测 BMP2 的来源。即刻递送可产生更好的骨再生。只有在 Gp1 中，BMP2 和 VEGF 的 mRNA 表达均上调（分别为+7.3，p=0.001；+1.53，p=0.001）。即刻重建组中 BMP2 蛋白显著升高；然而，在检查的切片中未检测到 VEGF 蛋白。即刻递送 rhBMP2 似乎诱导了周围软组织中内源性 BMP2 的释放，而延迟递送则缺乏这种作用，这可能解释了与 BMP2 应用相关的临床结果的可变性。BMP2 与内皮细胞（ECs）的共定位表明，ECs 可能是内源性 BMP2 的来源。
