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

描述（由申请人提供）：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，这些数字还在增加。磷酸钙骨水泥（CPC）可以在原位成型和固化形成羟基磷灰石，具有骨导电性，并且可以被新骨吸收和替换。然而，CPC的低强度限制了其在非应力位置的使用。在最初的五年里，一组新的强大的大孔CPCs被开发出来。产生了用于组织长进长的大孔和量身定制的强度历史的支架。目前，用于干细胞输送的预制载体难以将细胞植入支架深处，也无法通过微创手术进行注射。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具有干细胞和生长因子输送的可注射、强、韧、大孔纳米磷灰石支架，用于牙科、颅面和骨科应用。在目标1中，将开发一类新的可注射，强，韧性和大孔cpc。假设是：(i)可以调整CPC成分以提高注射性和强度；优化强化和宏观孔隙将产生高应变的CPC，以适应组织内的微运动；（iii）仿生纳米磷灰石支架将增强来自大鼠骨髓的间充质干细胞（MSCs）的定植和分化。目标2将研究生长因子的传递并测试这些假设：(i)可以制定快速凝固、强效和大孔的cpc -生长因子载体；（ii） CPC中生长因子释放量与孔隙体积分数成正比；（iii）可实现多种生长因子的可控顺序释放，优化干细胞功能。目标3将提供干细胞并测试这些假设：(i)干细胞可以被包裹在水凝胶中并纳入CPC，而不会降低细胞的活力和分化；（ii）水凝胶珠溶解释放细胞，同时在CPC中形成相互连接的大孔；（iii）干细胞和生长因子可以在同一载体中共同递送，以增强细胞功能。目标4将评估动物模型中的骨再生并验证以下假设：(i)大孔CPC输送的干细胞、成骨和血管生成生长因子将被大鼠整个临界尺寸颅骨缺损完全吸收并被新骨取代；（ii）与传统CPC相比，可注射的强强大孔CPC具有更高的骨吸收和新骨形成率；（iii）优化支架的组成、大孔隙度和多种生长因子将大大促进干细胞成骨。这种具有干细胞和生长因子输送功能的新一代可注射、坚固和大孔纳米磷灰石支架有望在牙科、颅面和骨科领域得到应用，极大地增强了骨再生，改善了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.