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

项目摘要/摘要 美国每年有700万人骨折，肌肉骨骼疾病花费215美元 十亿/年。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，可被新材料吸收和替换 骨头。然而，CPC的低强度限制了其在非应力位置的使用。在这最初的五年里 Grant，开发了一组新型的强韧大孔CPC。长大孔支架材料 组织向内生长和量身定做的力量史被生成。目前，干细胞的预制载体 接种物难以将细胞种植到支架深处，并且不能以微创方式注射。 程序。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的、坚韧的、大孔的纳米 具有干细胞和生长因子输送的磷灰石支架，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。假说 是：(I)CPC成分可以量身定制，以提高可注性和强度；(Ii)优化加固 和大孔隙率将产生高应变的CPC以适应组织内的微观运动； 仿生纳米磷灰石支架将促进间充质干细胞的定植和分化 (MSCs)来源于大鼠骨髓。AIM 2将研究生长因子的传递并检验以下假设： (一)可配制速凝、强韧、大孔的CPC生长因子载体；(二)生长因子 CPC的释放与孔体积分数成正比；(Iii)多重生长的受控顺序释放 优化干细胞功能的因素是可以实现的。AIM 3将交付干细胞，并测试这些假设： (I)干细胞可以被包裹在水凝胶中并并入CPC中，而不会降低细胞活力和 分化；(Ii)水凝胶珠可以溶解以释放细胞，并同时产生相互连接的 (Iii)干细胞和生长因子可在同一载体中共输送以增强细胞 功能。Aim 4将评估动物模型中的骨再生并检验这些假设：(I)大孔 输送干细胞、成骨和血管生成因子的CPC将被完全吸收和 取而代之的是大鼠整个临界大小的颅骨缺损；(Ii)可注射的，坚固的和 大孔CPC的吸收和新骨形成率远高于传统CPC；(Iii) 优化支架成分、大孔率和多种生长因子将极大地增强骨骼 通过干细胞形成。这种新一代可注射、坚固和大孔的纳米磷灰石支架 干细胞和生长因子的输送有望在牙科、颅面和整形外科应用， 极大地增强了骨再生，改善了数百万人的健康和生活质量。

Project Summary/Abstract 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.