Fractures show delayed healing and increased possibility of re-fracture in OI murine models.

项目摘要/摘要 成骨不全(OI)是最常见的遗传性骨发育不良。它的特点是有骨头 因骨量减少和骨质质量受损而导致的畸形和骨折。大约85%-90%的案件是 主要遗传和由编码I型胶原(COL1A1和COL1A2)的基因突变所致， 骨基质的主要蛋白质。10%-15%的OI病例是隐性遗传的，大多数是由 包括软骨相关蛋白(CRTAP)在内的Pro-3-羟基化复合体成员的突变。 OI患者一生中骨折的风险增加。延迟愈合和骨不连 据报道，在OI患者中有24%的骨折和52%的截骨手术，高于健康人群 然而，关于这些愈合异常背后的分子机制的研究很少。 因此，有一个尚未得到满足的需要，以更好地了解OI影响骨折愈合的机制。它是 我的目标是确定OI在骨折愈合过程中的不同程度以及抗转化生长因子β治疗 可以正常化或改善小鼠骨折愈合和愈合的骨质量。我观察到一个 在CRTAP-/-小鼠中，骨痂大小和强度的减少表明骨折愈合延迟。这是我的假设 OI骨折的愈合效果不佳，这一过程最终导致骨骼变弱，从而导致 再次骨折的可能性增加。同时使用Col1a2+/G610C和CrTAP-/-小鼠(显性和隐性 OI模型)，我将使用开放性胫骨骨折手术来模拟长骨骨折愈合。这就做 通过收集骨折部位的胫骨，确定OI骨折愈合与野生型相比的差异 多个时间点观察骨折端骨痂软骨发育及成分变化 治愈的过程。此外，我将分析OI骨痂的结构和生物力学结构，以 确定OI表型对愈合/完全愈合的骨的强度的影响。最后，我们组 用COL1A2+/G610C和CrTAP-/-OI小鼠模型证实OI骨中转化生长因子β信号的增加 这是导致低骨量/骨质表型的原因。我们进一步证明了抗转化生长因子β治疗 改善两种OI小鼠模型的骨量和质量。因此，我将研究抗转化生长因子β的作用。 治疗对OI和WT小鼠骨痂成分、骨痂强度和愈合骨强度/质量的影响。 目前，抗转化生长因子β合成代谢疗法正在进行临床试验，但其对骨折愈合的影响尚未得到证实。 评估过了。因此，从这项研究中获得的知识将是全新的，对 OI管理领域。此外，Col1a2+/G610C和CrTAP-/-小鼠均通过胶原基因突变建立OI模型 或者胶原蛋白的处理以及细胞外基质结构对骨折愈合的影响还知之甚少。 通过了解OI的骨折愈合情况，其结果将对基本的骨折愈合具有广泛的意义 研究。这项建议不仅将确认和阐明OI的异常愈合，它还将确定 这些差异背后的机制，以及评估当前治疗方法对愈合过程的影响。

Project Summary/Abstract Osteogenesis Imperfecta (OI) is the most common genetic bone dysplasia. It is characterized by bone deformities and fractures caused by low bone mass and impaired bone quality. Roughly 85-90% of cases are dominantly inherited and result from mutations in genes encoding type I collagen (COL1A1 and COL1A2), the major protein of the bone matrix. 10-15% of OI cases are recessively inherited and the majority result from mutations in members of the prolyl-3-hydroxylation complex including Cartilage Associated Protein (CRTAP). OI patients are at an increased risk of fracture throughout their lifetimes. Delayed healing and non-union has been reported in 24% of fractures and 52% of osteotomies in OI patients, higher than in the healthy population yet there have been few studies concerning the molecular mechanisms behind these healing abnormalities. Thus, there is an unmet need to better understand the mechanisms by which OI affects fracture healing. It is my goal to determine to what extent the fracture healing process differs in OI and how anti-TGFβ treatment may normalize or improve fracture healing and healed bone quality in murine models. I have observed a decrease in callus size and strength indicating a delay in fracture healing in Crtap–/– mice. It is my hypothesis that OI fractures undergo suboptimal healing and that this process results in ultimately weaker bone leading to the increased possibility of re-fracture. Using both Col1a2+/G610C and Crtap–/– mice (dominant and recessive models of OI, respectively), I will model long bone fracture healing using open tibial fracture surgery. I will determine the differences in OI fracture healing when compared to wild-type by collecting fractured tibia at multiple timepoints to observe fracture callus cartilage development and composition changes throughout the healing process. Additionally, I will analyze the architectural and biomechanical structure of the OI callus to determine the effect of the OI phenotype on the strength of healing/fully healed bone. Finally, our group demonstrated increased TGFβ signaling in OI bone using both Col1a2+/G610C and Crtap–/– OI mouse models that contributes to the low bone mass/quality phenotype. We further showed that anti-TGFβ treatment improves bone mass and quality in both OI mouse models. Therefore, I will investigate the effect of anti-TGFβ treatment on callus composition, callus strength, and healed bone strength/quality in OI and WT mice. Currently, anti-TGFβ anabolic treatments are in clinical trials yet their effect on fracture healing has not been assessed. Therefore, the knowledge gained from this study will be entirely novel and of high importance to the field of OI management. Furthermore, both Col1a2+/G610C and Crtap–/– mice model OI via mutations in collagen or collagen processing and the effect of extracellular matrix structure on fracture healing is poorly understood. By understanding fracture healing in OI, the results will have broad significance for basic fracture healing research. This proposal will not only confirm and elucidate abnormal healing in OI, it will also identify the mechanism behind these differences as well as assess the effect of a current therapy on the healing process.