Engineering of Vascularized Bone

描述(申请人提供)：在创伤、慢性病、肿瘤切除和先天畸形引起的骨缺损的外科重建中，骨移植是非常必要的。骨组织工程在改变骨重建的临床实践方面提供了巨大的潜力。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；相反，它是次优的血管形成。我们和其他人的新工作已经开始探索两个不同的干细胞/祖细胞群体之间令人兴奋的相互作用，这些干细胞/祖细胞产生骨和血管生成，即间充质干细胞(MSCs)和造血干细胞(HSCs)。干细胞和骨髓间充质干细胞联合移植的生物工程血管生成与目前的血管生成方法是不同的，包括生长因子传递或构建血管类似物。在发育过程中，HSCs和MSCs协同作用诱导(血管化)成骨。在成人中，骨髓间充质干细胞和造血干细胞共同居住在骨髓和其他基质细胞的壁龛中，这是加强研究的重点。传统上，骨髓间充质干细胞被骨组织工程界分离为贴壁细胞(与组织培养的聚苯乙烯)，而非贴壁的造血干细胞通常被丢弃。我们的初步数据，正如最近发表在《公共科学图书馆·综合》上的一篇报道所记录的那样，表明MSC和HSC共同移植产生了带血管的异位骨，比单独移植MSC或HSC更显著。这些发现，以及最近其他人对MSC-HSC相互作用的发现，激发了我们的中心假设，即共同移植的MSCs和HSCs在原位模型中再生血管化骨。颅骨缺损是一种广泛应用于骨愈合和临床挑战的模型。目前的骨替代品，如羟基磷灰石和移植物，低于外科医生的预期。因此，这项建议的总体目标是通过造血干细胞和骨髓间充质干细胞的协同作用在体内原位工程血管化骨。尽管HSCs和MSCs的联合移植在骨组织工程中代表着一个新的概念，但我们认为在将这种方法转化到临床环境之前，需要了解大量的基础生物学知识，其中一些是本提案中计划的。作为我们的长期目标，我们将探索一个令人兴奋的潜力，即MSCs和HSCs可以在单个门诊患者的骨髓抽吸程序中分离出来，并以最小的操作再生依赖血管的组织，如骨、脂肪、神经和真皮移植物。公共卫生相关性：骨移植在外科手术中是至关重要的，以重建因创伤、慢性病、肿瘤切除和先天性畸形而导致的骨缺损。自体骨移植是临床的黄金标准，但需要供骨部位的创伤和并发症；异体或异种骨移植与免疫排斥、病原体传播和次佳愈合有关，合成材料如羟基磷灰石缺乏整合。在这个方案中，我们利用血管前体细胞和骨祖细胞的共同作用设计了带血管的骨移植，这种带血管的骨移植可以定制成任何形状和尺寸，并与宿主现有的骨结合，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.