Mechanistic insights into polyphosphate-mediated osteoinduction.

项目摘要 迫切需要创造具有成本效益的生物材料，以促进骨生成， 当受损骨生物学受损（例如，骨不连或临界尺寸缺损）或当骨生成 在通常缺乏骨的组织中所需的（例如脊柱融合）。目前使用的生物材料包括自体移植物， 同种异体移植物、合成基质和骨诱导生物制剂。自体移植是金标准;然而， 有限，在收获过程中引起疼痛，并增加护理成本。骨传导同种异体移植物和合成 加入或不加入骨诱导因子（例如BMP 2）的基质，已经以不同的 结果和成本效益问题。理由：我们已经确定，陶瓷的合成类似物 血小板聚磷酸盐纳米颗粒（聚P-NP，链长60-120个重复单元）促进体内骨化， 令人惊讶的是，通过软骨内骨化，而不是主要的膜内骨化， 重组BMP 2（rBMP 2）。目的/方法：在这里，我们的目标是确定最佳性能， 骨化机制和潜在的毒性，并比较大量可用的聚P-NP 60 -120 对rBMP 2的骨诱导功效和毒性。我们将进行明确的系统调查， 最大化陶瓷polyP-NP 60 -120的骨诱导特性（目的1），以确定软骨形成是否是 对于它们的血管生成和骨诱导特性是必不可少的（目的2），并评估 使用它们会发生凝血和炎症（目的3）。骨诱导和有害特性将是 与rBMP 2相比。所有实验均采用骨诱导的“Urist”模型在体内进行 其中将实验材料植入鼠腓肠肌。预期结果：我们 预期陶瓷polyP-NP 60 -120将具有至少与rBMP 2相当的骨诱导潜力， 软骨形成对于聚P-NP 60 -120介导的骨诱导性是必需的，而不是被破坏， 在rBMP 2介导的骨诱导性中观察到，聚P-NP 60 -120将引起局部，但不是全身， 激活凝血和炎症。影响：如果发现属实，这些结果将表明陶瓷聚P- NP 60 -120可能是rBMP 2的一个很好的替代品。具体来说，如果聚P- NP 60 -120是通过软骨细胞中间体，这将是有利的，因为软骨细胞装备良好 在缺乏血管的环境中存活并产生骨诱导因子，包括VEGF和BMP 2， 例如需要骨移植的临床情况。此外，鉴于其通过合成的相对可用性， 陶瓷polyP-NP 60 -120也可能代表比分离或重组更经济的替代方案 骨诱导因子，如rBMP 2。

PROJECT SUMMARY There is an urgent need for the creation of cost-effective biomaterials to promote osteogenesis in situations where injured bone is biologically impaired (e.g. non-union or critical sized defects) or when osteogenesis is desired in tissue normally devoid of bone (e.g. spinal fusion). Currently used biomaterials include autograft, allografts, synthetic matrices, and osteoinductive biologics. Autograft is the gold standard; however, its quantity is limited, causes pain during harvesting, and increases cost of care. Osteoconductive allografts and synthetic matrices with or without the addition of osteoinductive factors (e.g. BMP2), have been employed with varying results and questionable cost-effectiveness. Rationale: We have determined that synthetic analogs of ceramic platelet polyphosphate nanoparticles (polyP-NP, chain length 60-120 repeat units) promote ossification in-vivo - surprisingly through endochondral ossification as opposed to primarily intramembranous ossification, as is observed with recombinant BMP2 (rBMP2). Aims/Approach: Here, we aim to determine the optimal properties, mechanism of ossification, and potential toxicity of the abundantly available polyP-NP60-120 and to compare the osteoinductive efficacy and toxicity to rBMP2. We will perform a definitive systematic investigation designed to maximize the osteoinductive properties of ceramic polyP-NP60-120 (Aim 1), to determine if chondrogenesis is essential for their angiogenic and osteoinductive properties (Aim 2), and assess whether toxic activation of coagulation and inflammation occurs with their use (Aim 3). Osteoinductive and deleterious properties will be compared to rBMP2. All experiments will be conducted in vivo employing the ‘Urist’ model of osteoinduction where experimental materials are implanted into the murine gastrocnemius muscle. Anticipated results: We anticipate that ceramic polyP-NP60-120 will possess at least equivalent osteoinductive potential as rBMP2, that chondrogenesis is essential for polyP-NP60-120 -mediated osteoinductivity as opposed to being dispensable, as is observed in rBMP2-mediated osteoinductivity, and that polyP-NP60-120 will cause local, but not systemic, activation of coagulation and inflammation. Impact: If found true, these results would indicate that ceramic polyP- NP60-120 may represent an excellent alternative to rBMP2. Specifically, if the osteoinductive properties of polyP- NP60-120 are through a chondrocyte intermediate, it would be advantageous as chondrocytes are well equipped to survive and produce osteoinductive factors, including VEGF and BMP2, in a vascularly devoid environments such as the clinical situations requiring bone grafting. Additionally, given its relative availability through synthetic routes, ceramic polyP-NP60-120 may also represent a more cost-effective alternative than isolated or recombinant osteoinductive factors, such as rBMP2.