Simpson Querrey Institute (SQI), Northwestern University 303 E. Superior, Chicago, IL 60611, United States; Department of Orthopaedic Surgery, Northwestern University, 676 N. Saint Clair, Chicago, IL 60611, United States.
Dimension Inx Corp, 3440 S. Dearborn St., Suite 142S, Chicago, IL 60616, United States.
Acta Biomater. 2021 Jun;127:146-158. doi: 10.1016/j.actbio.2021.03.060. Epub 2021 Apr 6.
We recently developed a recombinant growth factor-free bone regenerative scaffold composed of stoichiometric hydroxyapatite (HA) ceramic particles and human demineralized bone matrix (DBM) particles (HA-DBM). Here, we performed the first pre-clinical comparative evaluation of HA-DBM relative to the industry standard and established positive control, recombinant human bone morphogenetic protein-2 (rhBMP-2), using a rat posterolateral spinal fusion model (PLF). Female Sprague-Dawley rats underwent bilateral L4-L5 PLF with implantation of the HA-DBM scaffold or rhBMP-2. Fusion was evaluated using radiography and blinded manual palpation, while biomechanical testing quantified the segmental flexion-extension range-of-motion (ROM) and stiffness of the fused segments at 8-weeks postoperatively. For mechanistic studies, pro-osteogenic gene and protein expression at 2-days and 1-, 2-, and 8-weeks postoperatively was assessed with another cohort. Unilateral fusion rates did not differ between the HA-DBM (93%) and rhBMP-2 (100%) groups; however, fusion scores were higher with rhBMP-2 (p = 0.008). Both treatments resulted in significantly reduced segmental ROM (p < 0.001) and greater stiffness (p = 0.009) when compared with non-operated controls; however, the degree of stabilization was significantly higher with rhBMP-2 treatment relative to the HA-DBM scaffold. In the mechanistic studies, PLGA and HA scaffolds were used as negative controls. Both rhBMP-2 and HA-DBM treatments resulted in significant elevations of several osteogenesis-associated genes, including Runx2, Osx, and Alp. The rhBMP-2 treatment led to significantly greater early, mid, and late osteogenic markers, which may be the mechanism in which early clinical complications are seen. The HA-DBM scaffold also induced osteogenic gene expression, but primarily at the 2-week postoperative timepoint. Overall, our findings show promise for this 3D-printed composite as a recombinant growth factor-free bone graft substitute for spinal fusion. STATEMENT OF SIGNIFICANCE: Despite current developments in bone graft technology, there remains a significant void in adequate materials for bone regeneration in clinical applications. Two of the most efficacious bone graft options are the gold-standard iliac crest bone graft and recombinant human-derived bone morphogenetic protein-2 (rhBMP-2), available commercially as Infuse™. Although efficacious, autologous graft is associated with donor-site morbidity, and Infuse™ has known side effects related to its substantial host inflammatory response, possibly associated with a immediate, robust osteoinductive response. Hence, there is a need for a bone graft substitute that provides adequate osteogenesis without associated adverse events. This study represents a significant step in the design of off-the-shelf growth factor-free devices for spine fusion.
我们最近开发了一种由等摩尔羟基磷灰石(HA)陶瓷颗粒和人脱矿骨基质(DBM)颗粒组成的重组生长因子免费骨再生支架(HA-DBM)。在这里,我们使用大鼠后路脊柱融合模型(PLF)对 HA-DBM 支架相对于行业标准和既定阳性对照,重组人骨形态发生蛋白-2(rhBMP-2)进行了首次临床前比较评估。雌性 Sprague-Dawley 大鼠接受双侧 L4-L5 PLF 植入 HA-DBM 支架或 rhBMP-2。通过影像学和盲手法触诊评估融合,生物力学测试在术后 8 周时量化融合节段的屈伸活动范围(ROM)和刚度。对于机制研究,在另一个队列中,在术后 2 天、1 天、2 天和 8 天评估了促成骨基因和蛋白的表达。HA-DBM(93%)和 rhBMP-2(100%)组之间的单侧融合率没有差异;然而,rhBMP-2 组的融合评分更高(p=0.008)。与非手术对照组相比,两种治疗均导致节段 ROM 显著降低(p<0.001),刚度显著增加(p=0.009);然而,rhBMP-2 治疗相对于 HA-DBM 支架的稳定程度显著更高。在机制研究中,PLGA 和 HA 支架用作阴性对照。rhBMP-2 和 HA-DBM 治疗均导致几个成骨相关基因的显著升高,包括 Runx2、Osx 和 Alp。rhBMP-2 治疗导致早期、中期和晚期成骨标志物显著增加,这可能是早期临床并发症发生的机制。HA-DBM 支架也诱导了成骨基因的表达,但主要是在术后 2 周的时间点。总的来说,我们的研究结果表明,这种 3D 打印复合材料作为一种无重组生长因子的骨移植物替代物用于脊柱融合具有很大的潜力。
尽管目前在骨移植物技术方面取得了进展,但在临床应用中仍然存在着显著的骨再生材料空白。两种最有效的骨移植物选择是金标准的髂嵴骨移植物和重组人源性骨形态发生蛋白-2(rhBMP-2),可作为 Infuse™商业购买。虽然有效,但自体移植物与供体部位发病率有关,而 Infuse™ 具有与其大量宿主炎症反应相关的已知副作用,可能与即刻、强烈的成骨诱导反应有关。因此,需要一种提供足够成骨作用而无相关不良事件的骨移植物替代物。本研究代表着为脊柱融合设计即用型无生长因子装置迈出了重要一步。