Bobyn Justin D, Deo Nikita, Little David G, Schindeler Aaron
Orthopaedic Research & Biotechnology Unit, The Children's Hospital at Westmead, Sydney, NSW, Australia; Discipline of Paediatrics and Child Health, Faculty of Medicine, University of Sydney, Sydney, NSW, Australia.
Orthopaedic Research & Biotechnology Unit, The Children's Hospital at Westmead, Sydney, NSW, Australia; Discipline of Paediatrics and Child Health, Faculty of Medicine, University of Sydney, Sydney, NSW, Australia.
J Orthop Sci. 2021 Jul;26(4):684-689. doi: 10.1016/j.jos.2020.05.016. Epub 2020 Jul 23.
Spine fusion is a common procedure for the treatment of severe scoliosis, a frequent and challenging deformity associated with Neurofibromatosis type 1 (NF1). Moreover, deficiencies in NF1-Ras-MEK signaling affect bone formation and resorption that in turn impacts on spine fusion outcomes.
In this study we describe a new model for AdCre virus induction of Nf1 deficiency in the spines of Nf1 mice. The virus is delivered locally to the mouse spine in a fusion procedure induced using BMP-2. Systemic adjunctive treatment with the MEK inhibitor (MEKi) PD0325901 and the bisphosphonate zoledronic acid (ZA) were next trialed in this model.
AdCre delivery resulted in abundant fibrous tissue (Nf1 +393%, P < 0.001) and decreased marrow space (Nf1 -67%, P < 0.001) compared to controls. While this did not significantly impact on the bone volume of the fusion mass (Nf1 -14%, P = 0.999 n.s.), the presence of fibrous tissue was anticipated to impact on the quality of spine fusion. Multinucleated TRAP + cells were observed in the fibrous tissues seen in Nf1 spines. In Nf1 spines, MEKi increased bone volume (+194%, P < 0.001) whereas ZA increased bone density (+10%, P < 0.002) versus BMP-2 alone. Both MEKi and ZA decreased TRAP + cells in the fibrous tissue (MEKi -62%, P < 0.01; ZA -43%, P = 0.054). No adverse effects were seen with either MEKi or ZA treatment including weight loss or signs of illness or distress that led to premature euthanasia.
These data not only support the utility of an AdCre-virus induced knockout spine model, but also support further investigation of MEKi and ZA as adjunctive therapies for improving BMP-2 induced spine fusion in the context of NF1.
脊柱融合术是治疗重度脊柱侧弯的常见手术，脊柱侧弯是1型神经纤维瘤病（NF1）常见且具有挑战性的畸形。此外，NF1-Ras-MEK信号通路的缺陷会影响骨形成和骨吸收，进而影响脊柱融合的效果。
在本研究中，我们描述了一种通过腺病毒Cre（AdCre）病毒诱导Nf1小鼠脊柱中Nf1基因缺失的新模型。该病毒通过使用骨形态发生蛋白2（BMP-2）诱导的融合手术局部递送至小鼠脊柱。接下来，在该模型中试验了用MEK抑制剂（MEKi）PD0325901和双膦酸盐唑来膦酸（ZA）进行全身辅助治疗。
与对照组相比，AdCre病毒递送导致大量纤维组织（Nf1增加393%，P<0.001）和骨髓腔减少（Nf1减少67%，P<0.001）。虽然这对融合块的骨体积没有显著影响（Nf1减少14%，P=0.999，无统计学意义），但纤维组织的存在预计会影响脊柱融合的质量。在Nf1脊柱的纤维组织中观察到多核抗酒石酸酸性磷酸酶（TRAP）阳性细胞。在Nf1脊柱中，与单独使用BMP-2相比，MEKi增加了骨体积（增加194%，P<0.001），而ZA增加了骨密度（增加10%，P<0.002）。MEKi和ZA均减少了纤维组织中的TRAP阳性细胞（MEKi减少62%，P<0.01；ZA减少43%，P=0.054）。MEKi或ZA治疗均未观察到不良反应，包括体重减轻或导致过早安乐死的疾病或痛苦迹象。
这些数据不仅支持AdCre病毒诱导的基因敲除脊柱模型的实用性，还支持进一步研究MEKi和ZA作为辅助疗法，以改善NF1背景下BMP-2诱导的脊柱融合。
