Targeting TGFb In Osteogenesis Imperfecta

项目摘要 成骨不全症是一组异质性脆性骨疾病。超过95%的患者 I型前胶原基因（COL 1A 1和COL 1A 2）中存在显性遗传结构突变，或 在I型胶原蛋白翻译后组装中重要的蛋白复合物中的reckonin遗传突变 和羟基化。目前，没有FDA批准的OI治疗方法。虽然抗骨吸收剂的标签外使用 双膦酸盐已成为事实上的标准治疗，特别是在患有OI的儿童中，其临床影响 骨折发生率、轻度I型OI（> 50%的患者）和成人重度OI伴下部骨形成尚不清楚。 这突出了对OI的治疗创新的迫切需要。采用合成代谢方法，我们已经证明 在成人OI中，特立哌酮（PTH 1-34）增加轻度OI I型腰椎BMD，但令人惊讶的是， 在严重的OI中具有显著的效果，提示了克服PTH不敏感性的组合疗法的可能性。 我们和其他人已经表明，胶原蛋白的过度修饰和改变的交联导致异常的 矿化和改变的细胞外基质（ECM）-细胞信号传导，特别是过度的TGFβ信号传导， 小鼠OI（Col 1a 2G 610 C/+和Crtap-/-）。泛抗TGFβ治疗挽救了这些小鼠的骨骼表型。 在原代胎鼠成骨细胞中，TGFβ下调PTH 1受体，这使我们假设TGFβ 在中度和重度OI中，信号传导导致PTH不敏感（Aim 1）。在极端情况下， 其他研究表明，Col 1a 1 Jrt/+小鼠也有TGFβ增加;然而，它们对抗TGF β没有反应， 在中度OI模型中有效的剂量。在我们的1期抗TGF β临床试验中， 单次给药后，在中度但非重度OI参与者中观察到脊柱BMD。我们未发表 初步数据还显示在我们的轻度Col 1a 1 +/- OI小鼠中TGFβ增加。因此，我们假设 不同OI严重程度和骨靶向抗体中抗TGF β的剂量/频率范围要求 可以提高所有类型的疗效和安全性（目标2）。TGFβ在骨折愈合中也至关重要。我们之前 发现Col 1a 2G 610 C/+和Crtap-/-小鼠骨折愈合延迟，骨痂尺寸减小，抗TGF β进一步 减少了这个。这一观察结果强调了研究抗TGF β在治疗过程中的作用的重要性。 骨折修复的未来临床管理（目标3）。最后，了解TGFβ过量的机制， OI骨可能导致新的治疗靶点。其中一个假设是减少互动 异常胶原蛋白和富含亮氨酸的小蛋白聚糖之间的关系，如核心蛋白聚糖，它可以隔离成熟的TGFβ (Aim 4）。我们的总体目标是回答有关在OI中靶向TGFβ的问题和未满足的需求。目标1.是 过量TGFβ导致小鼠和III/IV型OI患者PTH不敏感？目标二。把骨头- 靶向抗TGF β抗体，并确定轻度、中度和重度OI的剂量范围。目标3. 评估抗TGF β治疗在OI骨折修复中的短期和长期效果。目标4。确定 核心蛋白聚糖在调节OI中过量TGFβ中的遗传需求。

PROJECT SUMMARY Osteogenesis Imperfecta (OI) is a group of heterogeneous brittle bone disorders. Over 95% of patients harbor dominantly inherited structural mutations in the type I procollagen genes (COL1A1 and COL1A2) or recessively inherited mutations in the protein complexes important in type I collagen post-translational assembly and hydroxylation. Currently, there are no FDA-approved treatments for OI. While off-label use of anti-resorptive bisphosphonates has become a de facto standard of care especially in children with OI, their clinical impact on fracture incidence, mild OI type I (> 50% of patients), and adult, severe OI with lower bone formation is unclear. This highlights the critical need of therapeutic innovations for OI. Taking anabolic approaches, we have shown in adult OI that teriparatide (PTH 1-34) increases lumbar spine BMD in mild OI type I, but surprisingly, had no significant effect in severe OI, suggesting the possibility of combinatorial therapy to overcome PTH insensitivity. We and others have shown that collagen over-modification and altered cross-linking lead to abnormal mineralization and altered extracellular matrix (ECM)-to-cell signaling, in particular, excessive TGFβ signaling in OI in mice (Col1a2G610C/+ and Crtap-/-). Pan-anti-TGFβ treatment rescued the skeletal phenotype in these mice. In primary fetal rat osteoblasts, TGFβ downregulates PTH 1 receptor, which led us to hypothesize that TGFβ signaling contributes to PTH insensitivity in moderate and severe OI (Aim 1). On the severe end of the spectrum, others have shown that Col1a1Jrt/+ mice also have increased TGFβ; however, they did not respond to anti-TGFβ at doses that were effective in the moderate OI models. In our phase 1 anti-TGFβ clinical trial, increase lumbar spine BMD was observed in moderate but not severe OI participants after a single dose. Our unpublished preliminary data also showed increase TGFβ in our mild Col1a1+/- OI mice. We therefore hypothesize a wide dose/frequency range requirement for anti-TGFβ among different OI severities and a bone-targeted antibody can improve efficacy and safety across all types (Aim 2). TGFβ is also critical in fracture healing. We previously found delayed fracture healing with reduced callus size in Col1a2G610C/+ and Crtap-/- mice and anti-TGFβ further reduced this. This observation underscores the importance for studying the effects of anti-TGFβ in the course of fracture repair for future clinical management (Aim 3). Finally, understanding the mechanism of TGFβ excess in OI bone could potentially lead to new therapeutic targets. One hypothesis for this is decreased interaction between abnormal collagen and small leucine rich proteoglycans, like Decorin, which sequester mature TGFβ (Aim 4). Our overall goal is to answer the questions and unmet needs around targeting TGFβ in OI. Aim 1. Is PTH insensitivity in mice and patients with OI type III/IV due to excessive TGFβ? Aim 2. Develop a bone- targeted anti-TGFβ antibody and determine the dose range for mild, moderate, and severe OI. Aim 3. Assess the short and long-term effects of anti-TGFβ treatment in OI fracture repair. Aim 4. Determine the genetic requirement of Decorin in modulating excessive TGFβ in OI.