Engineering of Vascularized Bone

描述（由申请人提供）：骨移植物在创伤、慢性疾病、肿瘤切除和先天性异常导致的骨骼缺损的手术重建中是急需的。骨组织工程学在骨重建的临床实践中具有巨大的潜力。然而，一些关键的障碍限制了骨组织工程转化为临床实践。重要的是，骨组织工程的关键障碍之一不是骨本身，而是次优血管化。我们和其他人的新兴工作已经开始探索两种不同的干/祖细胞群体之间令人兴奋的串扰，这些干/祖细胞产生骨和血管生成，即间充质干细胞（MSC）和造血干细胞（HSC）。通过HSC和MSC的共移植的生物工程化血管生成偏离当前的血管生成方法，包括生长因子递送或制造血管类似物。在发育中，HSC和MSC协同作用以诱导（血管化）成骨。在成人中，MSC与HSC共同存在于骨髓龛中的其他基质细胞中，这些基质细胞是加强研究的重点。骨髓间充质干细胞通常作为贴壁细胞（组织培养聚苯乙烯）由骨组织工程界分离，而非贴壁的HSC通常被丢弃。我们的初步数据，如最近在PloS One中的报道所记录的，证明MSC和HSC谱系的共移植产生血管化异位骨，比单独MSC或HSC的移植更显著。这些发现，以及其他人最近发现的MSC-HSC串扰，激发了我们的中心假设，即共移植的MSC和HSC在原位模型中再生血管化骨。颅骨缺损代表了骨愈合的广泛使用模型和实质性临床挑战。目前的骨替代品，如羟基磷灰石和移植物低于外科医生的期望。因此，本提案的总体目标是通过HSC和MSC的协同作用在体内原位工程化血管化骨。虽然造血干细胞和间充质干细胞的共移植是骨组织工程的一个新概念，但我们认为，在将这种方法转化为临床环境之前，需要了解大量的基础生物学，其中一些计划在本提案中。作为我们的长期目标，将探索的一个令人兴奋的潜力是，MSC和HSC可以在单个门诊骨髓抽吸程序中分离，并最小限度地操作以再生血管依赖性组织，如骨，脂肪，神经和真皮移植物。公共卫生相关性：在外科手术中，骨移植物是重建由创伤、慢性疾病、肿瘤切除和先天性异常引起的骨骼缺损的关键。自体骨移植物是临床金标准，但需要供体部位创伤和发病率;同种异体或异种移植物与免疫排斥、病原体传播和次优愈合相关，而合成材料（如羟基磷灰石）的整合性较差。在这个提议中，我们从血管祖细胞和骨祖细胞的联合作用中工程化血管化骨移植物;血管化骨移植物可以被定制成任何形状和尺寸，并与宿主现有的骨整合，从而为骨缺损提供改进的治疗模式。

DESCRIPTION (provided by applicant): Bone grafts are critically needed in the surgical reconstruction of skeletal defects resulting from trauma, chronic diseases, tumor removal and congenital anomalies. Bone tissue engineering offers tremendous potential in transforming the clinical practice of skeletal reconstruction. However, several critical barriers have restricted the translation of bone tissue engineering into clinical practice. Importantly, one of the key barriers in bone tissue engineering is not bone per se; instead, it is suboptimal vascularization. Emerging work from us and others has begun to explore an exciting cross-talk between two distinctive populations of stem/progenitor cells that generate bone and angiogenesis, namely mesenchymal stem cells (MSCs) and hematopoietic stem cells (HSCs). Bioengineered angiogenesis by co-transplantation of HSCs and MSCs is a departure from current angiogenesis approaches including growth factor delivery or fabricating blood vessel analogs. In development, HSCs and MSCs function synergistically to induce (vascularized) osteogenesis. In the adult, MSCs co-reside with HSCs in bone marrow niches among other stromal cells that are the focus on intensifying studies. MSCs are conventionally isolated as adherent cells (to tissue culture polystyrene) by bone tissue engineering community, whereas non-adherent HSCs are conventionally discarded. Our preliminary data, as documented in a recent report in PloS One, demonstrate that co- transplantation of MSC and HSC lineages yielded vascularized ectopic bone, more significantly than the transplantation of MSC or HSC alone. These findings, and also recent discoveries of MSC-HSC cross-talk by others, have motivated our central hypothesis that co-transplanted MSCs and HSCs regenerate vascularized bone in an orthotopic model. The calvarial defect represents a widely utilized model for bone healing and substantial clinical challenges. Current bone substitutes such as hydroxyapatite and grafts are below the surgeon's expectations. Accordingly, the overall goal of this proposal is to engineer vascularized bone in vivo orthotopically from synergistic actions of HSCs and MSCs. Although co-transplantation of HSCs and MSCs represents a novel concept in bone tissue engineering, we believe that a great deal of fundamental biology needs to be understood, some of which are planned in this proposal, prior to the translation of this approach to clinical setting. An exciting potential that will be explored as our long-term goal is that MSCs and HSCs can be isolated in a single outpatient bone marrow aspiration procedure, and minimally manipulated to regenerate vasculature-dependent tissues such as bone, adipose, nerve and dermal grafts. PUBLIC HEALTH RELEVANCE: Bone grafts are critically needed in surgical procedures to reconstruct skeletal defects resulting from trauma, chronic diseases, tumor removal and congenital anomalies. Autologous bone grafts are the clinical gold standard, but necessitate donor site trauma and morbidity; allogeneic or xenogeneic grafts are associated with immunorejection, pathogen transmission and suboptimal healing and synthetic materials such as hydroxyapatite suffer from poor integration. In this proposal, we have engineered vascularized bone grafts from the combined actions of vascular progenitor cells and bone progenitor cells; the vascularized bone grafts can be tailored to any shape and dimension, and integrate with host's existing bone, thus providing an improved treatment modality for bone defects.