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

描述（由申请人提供）：在美国，每年有700万人遭受骨折，肌肉骨骼疾病每年花费2150亿美元。这些数字随着人口老龄化而增加。磷酸钙骨水泥（CPC）可在原位成型和凝固形成羟基磷灰石，具有骨传导性，可被吸收并被新骨取代。然而，CPC的低强度限制了其在非应力位置的使用。在最初的五年中，开发了一组新的强大和大孔CPC。生成具有用于组织向内生长的长大孔和定制强度历史的支架。目前，用于干细胞递送的预制载体难以将细胞接种到支架深处，并且不能在微创手术中注射。目前的可注射载体很弱，不能用于广泛的承重修复。因此，我们未来五年的目标是开发可注射的、坚固的、坚韧的、大孔的纳米磷灰石支架，其具有干细胞和生长因子递送，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的、强的、坚韧的和大孔的CPC。假设是：（i）CPC组合物可以定制以改善可注射性和强度;（ii）优化增强和大孔隙率将产生具有高应变的CPC以适应组织内的微动;（iii）仿生纳米磷灰石支架将增强源自大鼠骨髓的间充质干细胞（MSC）的定殖和分化。目的2将研究生长因子递送并测试这些假设：（i）可以配制快速凝固的、强的和大孔CPC-生长因子载体;（ii）CPC的生长因子释放与孔体积分数成比例;（iii）可以实现多种生长因子的受控顺序释放以优化干细胞功能。目的3将递送干细胞并测试这些假设：（i）干细胞可以包封在水凝胶中并掺入CPC中而不降低细胞活力和分化;（ii）水凝胶珠可以溶解以释放细胞并伴随地在CPC中产生互连的大孔;（iii）干细胞和生长因子可以共同递送在同一载体中以增强细胞功能。目的4将在动物模型中评估骨再生并验证这些假设：（i）大孔CPC递送干细胞和成骨和血管生成生长因子将在大鼠整个临界尺寸的颅骨缺损中被完全吸收并被新骨取代;（ii）可注射的、坚固的和大孔CPC比传统CPC具有更高的吸收和新骨形成率;（iii）优化支架组成、大孔隙率和多种生长因子将极大地增强通过干细胞的骨形成。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递送功能，预计将用于牙科、颅面和整形外科应用，大大增强骨再生，改善数百万人的健康和生活质量。 公共卫生相关性：在美国，每年有700万人遭受骨折，肌肉骨骼疾病每年花费2150亿美元。这些数字随着人口老龄化而增加。该项目将开发第一代可注射、坚固、坚韧、大孔、模拟骨矿物的纳米磷灰石支架，并将在动物模型中研究骨再生。潜在的应用包括牙科、颅面和整形外科修复。它们包括上颌骨和下颌骨重建以及微创手术，如填充和加强骨质疏松性骨病变，大大增强骨愈合和再生，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.