Engineering of Vascularized Bone

描述（由申请人提供）：骨移植在创伤、慢性疾病、肿瘤切除和先天性异常导致的骨骼缺损的外科重建中是迫切需要的。骨组织工程在改变骨骼重建的临床实践方面具有巨大的潜力。然而，几个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；相反，它是次优的血管化。我们和其他人的新工作已经开始探索产生骨和血管生成的两种不同的干细胞/祖细胞群体，即间充质干细胞（MSCs）和造血干细胞（hsc）之间令人兴奋的相互作用。通过造血干细胞和间充质干细胞共同移植的生物工程血管生成与目前的血管生成方法不同，包括生长因子输送或制造血管类似物。在发育过程中，造血干细胞和间充质干细胞协同作用诱导（血管化）成骨。在成人中，骨髓间充质干细胞与造血干细胞共同存在于骨髓壁龛中的其他基质细胞中，这是加强研究的重点。骨组织工程界通常将间充质干细胞作为贴壁细胞（组织培养聚苯乙烯）分离，而非贴壁的间充质干细胞通常被丢弃。我们的初步数据，正如最近在PloS One上的一篇报告所记载的那样，表明MSC和HSC谱系的联合移植产生血管化异位骨，比单独移植MSC或HSC更显著。这些发现，以及最近其他人发现的MSC-HSC串扰，激发了我们的中心假设，即MSCs和hsc共移植可以在原位模型中再生血管化骨。颅骨缺损是一种广泛应用的骨愈合模型，也是临床面临的重大挑战。目前的骨替代物如羟基磷灰石和移植物都低于外科医生的期望。因此，本提案的总体目标是通过造血干细胞和间充质干细胞的协同作用在体内原位工程血管化骨。虽然造血干细胞和间充质干细胞的联合移植在骨组织工程中是一个新概念，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，其中一些是在本提案中计划的。作为我们的长期目标，我们将探索一个令人兴奋的潜力，即骨髓间充质干细胞和造血干细胞可以在一次门诊骨髓抽吸手术中分离出来，并进行最低限度的操作以再生血管依赖组织，如骨、脂肪、神经和真皮移植。公共卫生相关性：骨移植在外科手术中是非常需要的，以重建由创伤、慢性疾病、肿瘤切除和先天性异常引起的骨骼缺损。自体骨移植是临床的金标准，但必然会造成供区创伤和发病率；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有关，合成材料如羟基磷灰石的整合性差。在本研究中，我们利用血管祖细胞和骨祖细胞的共同作用，构建了血管化骨移植物；血管化骨移植物可以定制任何形状和尺寸，并与宿主现有骨相结合，从而为骨缺损提供了一种改进的治疗方式。

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.