Osteogenic and angiogenic tissue regeneration to accelerate secondary bone healing during aging

临床前提：衰老与脆性骨折的频率增加有关，这通常会导致 巨大的经济和情感负担。对这些骨折的治疗无效会导致生产力下降和 经常增加与骨折相关的并发症的费用，包括增加死亡率。此外，风险 患者的合并症和代谢性疾病，如 糖尿病或骨质疏松症。这些骨折绝大多数是针对椎骨、股骨近端、股骨远端、 肱骨近端和桡骨远端。是否接受手术治疗(如股骨骨折或钢板固定) )或非手术(即石膏或吊带)，这些骨折通过软骨内骨化愈合。 在一个称为二次骨折愈合的过程中。各种骨合成代谢药物，最初设计的目的是 治疗骨质疏松症患者，已被试验增强骨折修复能力。然而，尽管他们已经建立了 在增加动态平衡骨量方面的疗效，它们在临床上加速应用取得了有限的成功 骨折修复。因此，寻找新的分子靶点以促进继发性骨修复残留物 最重要的是。此翻译研究应用程序的目标是加速次级骨 靶向增强骨膜细胞诱导的衰老小鼠体内修复的新调控通路 骨折骨痂形成过程中的成骨和血管生成。 科学前提：我们提供了令人信服的以下初步证据：1.RUNX3以 人和小鼠骨折的间充质细胞。2.愈伤组织中RUNX3的表达随培养时间的延长而降低 骨折会愈合的。3.骨膜细胞(CKO)中Runx3的条件性缺失导致次级骨增强 通过增加骨生成和血管生成来愈合。4.骨膜中RUNX3缺失导致 与对照组相比，CKO小鼠骨折股骨中IL-17a受体(IL-17ra)表达增加。 5.RUNX3直接与IL-17ra近端启动子结合。最后，6.RUNX3蛋白水平在 老年与幼年小鼠骨折骨痂中间充质细胞的比较。 我们的中心假设是骨膜细胞中Runx3的抑制将加速继发性骨折愈合 在衰老小鼠中，通过激活间充质细胞群中的IL-17信号。 具体目标：我们将确定骨膜细胞中Runx3的缺失可以加速骨再生和 通过增强骨折部位的骨形成和血管生成来促进衰老小鼠的二次骨愈合。 (目标1)。然后，我们将证明Runx3通过年龄延迟骨痂骨形成和血管入侵- 依赖抑制间充质细胞中的IL-17ra信号。(目标2 A)。最后，我们将使用水凝胶局部治疗 传递Runx3 siRNA复合纳米粒并检查该治疗方法的有效性和安全性 在促进老年性骨折愈合方面(目标2B)。

Clinical premise: Aging is associated with increased frequency of fragility fractures, which often result in significant economic and emotional burden. Ineffective treatment of these fractures leads to lost productivity and often increased expenses of fracture-associated complications, including increased mortality. Moreover, the risk of impaired or delayed bony union is further enhanced by patient co-morbidities and metabolic diseases such as diabetes or osteoporosis. The vast majority of these fractures target the vertebrae, proximal femur, distal femur, proximal humerus and distal radius. Whether they are treated operatively (i.e. nailing a femur fracture or plating a distal radius fracture) or non-operatively (i.e. cast or sling), these fractures heal via endochondral ossification in a process called secondary fracture healing. Various bone anabolic drugs, which were initially designed to treat osteoporotic patients, have been tested to enhance fracture repair. However, despite their established efficacy in increasing homeostatic bone mass, limited success was achieved in their clinical use to accelerate fracture repair. Therefore, identifying novel molecular targets to enhance secondary bone repair remains of paramount importance. The objective of this translational research application is to accelerate secondary bone repair in vivo by targeting novel regulatory pathways in aging mice that enhance periosteal cell-induced osteogenesis and angiogenesis during fracture callus formation. Scientific premise: We provide compelling preliminary evidence of the following: 1. Runx3 is expressed in mesenchymal cells of both human and murine fractures. 2. Runx3 expression in the callus decreases as the fracture heals. 3. Conditional deletion of Runx3 in periosteal cells (cKO) results in enhanced secondary bone healing through increased osteogenesis and angiogenesis. 4. Runx3 deletion in the periosteum resulted in increased expression of IL-17a receptor (IL-17ra) in fractured femurs of cKO mice compared to controls animals. 5. Runx3 directly binds to the proximal promoter of IL-17ra. Finally, 6. Runx3 protein levels remain elevated in mesenchymal cells in fracture calluses of aged compared to juvenile mice. Our central hypothesis is that repression of Runx3 in periosteal cells will accelerate secondary fracture healing in aging mice through activation of IL-17 signaling in mesenchymal cell populations. Specific objectives: We will establish that Runx3 deletion in periosteal cells accelerates bone regeneration and secondary bone healing in aging mice through enhanced bone formation and angiogenesis at the fracture site. (Aim 1). We will then demonstrate that Runx3 delays callus bone formation and vascular invasion by age- dependently inhibiting IL-17ra signaling in mesenchymal cells. (Aim 2A). Finally, we will use hydrogels to locally deliver Runx3 siRNA-complexed nanoparticles and examine the efficacy and safety of this therapeutic approach in accelerating senile fracture healing (Aim 2B).