Injectable and Strong Nano-Apatite/Stem Cell Scaffolds for Bone Regeneration

描述(申请人提供)：在美国，每年有700万人患有骨折。肌肉骨骼疾病每年花费2150亿美元。随着人口老龄化，这些数字正在增加。磷酸钙骨水泥(CPC)可以模塑并原位固化形成羟基磷灰石，具有骨传导性，可以被新骨吸收和替代。然而，CPC的低强度限制了其在非应力位置的使用。在这笔赠款的最初五年中，开发了一组新的强大和大孔的CPC。生成了具有用于组织内长和量身定制的强度历史的长大孔支架。目前，用于干细胞输送的预制载体难以将细胞种植到支架深处，也不能以微创方式注射。目前的可注射载体很弱，不能用于大范围的承重修复。因此，我们未来五年的目标是开发可注射、坚固、坚韧和具有干细胞和生长因子输送功能的大孔纳米磷灰石支架，用于牙科、颅面和整形外科应用。在目标1中，将开发一类新的可注射、坚固、坚韧和大孔的CPC。假设：(I)CPC成分可以定制以提高可注射性和强度；(Ii)优化加固和大孔率将产生高应变的CPC，以适应组织内的微观运动；(Iii)仿生纳米磷灰石支架将增强大鼠骨髓间充质干细胞(MSCs)的定植和分化。目的2将研究生长因子的传递，并检验这些假设：(I)快速固化、强大和大孔的CPC-生长因子载体可以被配制；(Ii)从CPC中释放的生长因子与孔体积分数成正比；(Iii)可以实现多种生长因子的可控连续释放，以优化干细胞功能。Aim 3将运送干细胞并检验这些假设：(I)干细胞可以被包裹在水凝胶中并整合到CPC中，而不会降低细胞的活力和分化；(Ii)水凝胶微珠可以溶解以释放细胞，同时在CPC中产生相互连接的大孔；(Iii)干细胞和生长因子可以在同一载体中共输送以增强细胞功能。目的4将评估动物模型的骨再生并验证这些假说：(I)大孔CPC运送干细胞以及成骨和血管生长因子将被完全吸收，并被整个临界大小的颅骨缺损中的新骨取代；(Ii)可注射的、坚固的和大孔的CPC比传统的CPC具有更高的吸收和新骨形成率；(Iii)优化支架组成、大孔率和多种生长因子将极大地促进干细胞成骨。这种新一代可注射、坚固和大孔的纳米磷灰石支架具有干细胞和生长因子输送功能，有望在牙科、颅面和骨科应用，极大地增强骨再生，改善数百万人的健康和生活质量。 与公共健康相关：美国每年有700万人患有骨折。肌肉骨骼疾病每年花费2150亿美元。随着人口老龄化，这些数字正在增加。该项目将开发第一代可注射、坚固、坚韧、大孔、具有干细胞和多种生长因子输送功能的仿骨纳米磷灰石支架，并将在动物模型中研究骨再生。潜在的应用包括牙科、颅面和骨科修复。它们包括上颌骨重建和微创手术，如填充和强化骨质疏松病变，极大地增强骨愈合和再生，以改善数百万人的健康和生活质量。

DESCRIPTION (provided by applicant): Seven million people suffer bone fractures annually in the U.S. Musculoskeletal conditions cost $215 billion/year. These numbers are increasing as the population ages. Calcium phosphate cement (CPC) can be molded and set in-situ to form hydroxyapatite, is osteoconductive, and can be resorbed and replaced by new bone. However, the low strength of CPC limits its use to non-stress locations. In the original five years of this grant, a new group of strong and macroporous CPCs were developed. Scaffolds with long macropores for tissue ingrowth and tailored strength history were generated. Currently, pre-fabricated carriers for stem cell delivery have difficulty in seeding cells deep into the scaffold, and cannot be injected in minimally-invasive procedures. Current injectable carriers are weak and cannot be used in a wide range of load-bearing repairs. Therefore, our objective for the next five years is to develop injectable, strong, tough, and macroporous nano- apatite scaffolds with stem cell and growth factor delivery for dental, craniofacial and orthopedic applications. In Aim 1, a new class of injectable, strong, tough and macroporous CPCs will be developed. The hypotheses are: (i) CPC composition can be tailored to improve injectability and strength; (ii) Optimizing the reinforcement and macroporosity will yield CPC with high-strain to accommodate for micro-motions within the tissues; (iii) The biomimetic nano-apatite scaffolds will enhance the colonization and differentiation of mesenchymal stem cells (MSCs) derived from rat bone marrow. Aim 2 will investigate growth factor delivery and test these hypotheses: (i) Fast-setting, strong and macroporous CPC-growth factor carrier can be formulated; (ii) Growth factor release from CPC is proportional to pore volume fraction; (iii) Controlled sequential release of multiple growth factors can be achieved to optimize stem cell function. Aim 3 will deliver stem cells and test these hypotheses: (i) Stem cells can be encapsulated in hydrogel and incorporated into CPC without decreasing cell viability and differentiation; (ii) Hydrogel beads can dissolve to release the cells and concomitantly create interconnected macropores in CPC; (iii) Stem cells and growth factors can be co-delivered in the same carrier to enhance cell function. Aim 4 will evaluate bone regeneration in animal models and test these hypotheses: (i) Macroporous CPC delivering stem cells and osteogenic and angiogenic growth factors will be completely resorbed and replaced by new bone across the entire critical-sized cranial defect in rats; (ii) The injectable, strong and macroporous CPCs have much higher resorption and new bone formation rates than traditional CPC; (iii) Optimizing the scaffold composition, macroporosity, and multiple growth factors will greatly enhance bone formation via stem cells. This new generation of injectable, strong and macroporous nano-apatite scaffolds with stem cell and growth factor delivery are expected to have dental, craniofacial and orthopedic applications, with greatly enhanced bone regeneration to improve the health and quality of life for millions of people. PUBLIC HEALTH RELEVANCE: Seven million people suffer bone fractures annually in the U.S. Musculoskeletal conditions cost $215 billion/year. These numbers are increasing as the population ages. This project will develop the first generation of injectable, strong, tough, macroporous, bone mineral-mimicking nano-apatite scaffolds with stem cell and multiple growth factor delivery, and will study bone regeneration in animal models. Potential applications include dental, craniofacial and orthopedic repairs. They include maxillary and mandibular reconstruction and minimally-invasive surgeries such as filling and strengthening osteoporotic bone lesions, with greatly enhanced bone healing and regeneration to improve the health and quality of life for millions of people.