Biomaterials for sequential growth factor delivery

描述（由申请人提供）：肌肉骨骼疾病的成本平均占发达国家国内生产总值的3%，在美国每年消耗约2540亿美元。天然肌肉骨骼组织工程代表了一种有希望的新方法，以扩大可以有效治疗的条件范围。本研究的重点是开发一种再生自然骨骼组织的新方法，重点是利用蛋白质生长因子暂时控制成体干细胞的活性。这项工作的指导假设是，工程生长因子可以包含在无机基质的生长层中，导致在材料溶解时连续的生长因子递送。生长因子将被标记为矿物结合序列，以包裹入钙基矿物中，随后的基质溶解将实现顺序递送。每种生长因子的递送将被设计成引起不同的间充质干细胞（MSC）反应，允许对早期生成的新骨组织进行时间控制。在首次演示我们的方法的实用性时，我们将按顺序释放一个有丝分裂因子（FGF-2）和一个成骨因子（BMP-2）。具体目标1将开发和表征一种在大孔海藻酸盐水凝胶模板内生长钙基矿物的方法。这种方法受到自然生物矿化过程的启发，并采用生理处理条件来实现包含生物活性生长因子。Specific Aim 2将设计带有假定的矿物结合序列标记的生长因子，用于包被到矿物材料中，并将系统地表征生长因子的包被、释放和生物活性。重点将是在保持生物活性的同时实现对释放率的高度控制。然后，我们将使用这种方法依次释放影响MSC活性的两种生长因子：有丝分裂因子（FGF-2）和成骨因子（BMP-2）。具体目标3将评估sa 2中开发的矿物基质中暂时受控的MSC活性，重点是优化功能性分化成骨细胞的存在。这一目的是为了证明我们的方法在具有重大临床意义的应用中的效用：功能性骨组织工程。这一目标的结果将作为一个跳板，发展一个广泛的研究计划，重点是暂时控制生长因子向干细胞的呈递。

DESCRIPTION (provided by applicant): Costs of musculoskeletal conditions represent an average of 3% of the gross domestic product of developed countries, consuming an estimated $254 billion annually in the V.S.. Engineering of natural musculoskeletal tissues represents a promising new approach to expand the range of conditions that can be effectively treated. This proposal focuses on development of a new approach for regenerating natural skeletal tissues, with an emphasis on temporally controlling the activity of adult stem cells using protein growth factors. The guiding hypothesis of this work is that engineered growth factors can be included into growing layers of an inorganic matrix, resulting in sequential growth factor delivery upon material dissolution. Growth factors will be tagged with a mineral binding sequence for inclusion into calcium-based minerals, and subsequent matrix dissolution will enable sequential delivery. Delivery of each growth factor will be designed to elicit a distinct mesenchymal stem cell (MSC) response, allowing for temporal control over early generation of new bone tissue. In a first demonstration of the utility of our approach, we will release a mitogenic factor (FGF-2) and an osteogenic factor (BMP-2) in sequence. Specific Aim 1 will develop and characterize a method for growing calcium-based minerals within a macroporous alginate hydrogel template. This approach is inspired by natural biomineralization processes, and employs physiological processing conditions to enable inclusion of biologically active growth factors. Specific Aim 2 will engineer growth factors tagged with a putative mineral binding sequence for inclusion into mineral materials, and will systematically characterize growth factor inclusion, release, and biological activity. The emphasis will be on achieving a high level of control over release rates while maintaining biological activity. We will then use this approach to sequentially release two growth factors that influence MSC activity: a mitogenic factor (FGF-2) and an osteogenic factor (BMP-2). Specific Aim 3 will evaluate temporally controlled MSC activity within the mineral matrices developed in S.A.2, focusing on optimizing the presence of functional, differentiated osteoblasts. This aim is designed to demonstrate the utility of our approach in an application with substantial clinical significance: engineering of functional bone tissue. The results of this aim will serve as a springboard for development of an extensive research program focused on temporally controlling growth factor presentation to stem cells.