Identifying Approaches to Enhance Bone and Cartilage Regeneration

骨折未能正确愈合与显著的发病率和死亡率相关。另夕h 需要适当地形成骨对于从关节置换到 脊柱融合术和牙科植入物。在人口老龄化的情况下，对生物医学的需求甚至更大。近期 鉴定骨骼祖细胞，由8个亚群组成，能够形成所有三个 骨骼、骨、软骨和基质的组成部分，有望对改善 这些治疗的结果。一个关键的问题仍然是什么因素影响最终的细胞命运， 这些骨骼祖细胞我们对基质细胞蛋白DEL 1的数据表明，它对 骨骼修复我们有初步数据表明它对骨骼祖细胞生物学有直接影响 我们认为DEL 1在它们的生物学中起着重要的作用。 在此之前，我们的数据显示DEL 1对软骨细胞有生物学作用，但对成骨细胞没有。我们 显示小鼠骨骼干细胞（mSSC）和骨、软骨、基质的数量减少， 骨髓祖细胞（BCSP），在骨折愈合中最重要的骨骼祖细胞，我们 提出骨折后骨形成减少的机制是由于对骨骼祖细胞的影响 骨折后的扩张能力。我们计划首先通过分离mSSC和BCSP来研究这一点， (KO)和野生型（WT）小鼠并比较它们的生物学。我们将在体外研究BCSP的生物学特性， 测定细胞增殖、成骨和软骨形成潜力。BCSP形成不同的表型 称为骨折BCSP（f-BCSP），其在骨折后具有更大的增殖能力和成骨潜力， 我们将测试同样的变化是否发生在我们的基因敲除小鼠身上。我们将进行体内试验， 通过将BCSP植入肾包膜来检查它们形成骨的情况。 理解DEL 1如何影响骨折后骨形成的一个关键问题是理解DEL 1是什么， 发生在WT和KO小鼠骨折后的骨骼祖细胞中。我们将使用血统追踪技术， 小鼠目前在我们的实验室检查子细胞的命运，从个别克隆的骨骼肌 祖细胞 最后一系列的实验代表了我们将DEL 1的使用转化为潜力的初步方法。 治疗首先，我们将进行一个精心控制的微阵列实验，以确定在KO中改变的途径。 与WT相比的骨骼祖细胞。我们将研究外源性DEL 1促进存活力的能力， 体外培养的骨骼干细胞的生长。我们将测试DEL 1刺激骨骼和软骨的能力， 植入肾包膜的骨骼祖细胞的形成。最后，我们将研究是否 将外源性DEL 1蛋白置于骨折部位可以促进正常骨折愈合。我们还将使用 另一个模型是接受后肢照射的小鼠骨折愈合不良。 总之，我们将研究Del 1如何影响骨骼祖细胞的生物学。除了 这些实验提供了将这些发现转化为治疗方法的步骤，可以为我们提供 关于缺乏Del 1如何导致骨折愈合中骨减少的机械答案。他们将提供 深入了解影响骨骼祖细胞潜在命运的因素。

Failure to properly heal bone fractures is associated with significant morbidity and mortality. Additionally, the need to properly form bone is vital to successful outcomes from surgeries ranging from joint replacement to spinal fusion to dental implants. In an aging population, the biomedical need is even greater. The recent identification of skeletal progenitor cells, composed of 8 subpopulations, capable of forming all three components of the skeleton, bone, cartilage and stroma, promises to have a major impact on improving the outcomes for these therapies. A key question that remains is what are the factors affecting eventual cell fate of these skeletal progenitor cells. Our data on the matricellular protein DEL1 have shown it has an impact on skeletal repair. We have preliminary data indicating that it has a direct effect on skeletal progenitor cell biology and we propose that DEL1 plays an important role in their biology. Prior to this, our data had shown DEL1 had a biological effect on chondrocytes, but not on osteoblasts. We demonstrated decreased numbers of mouse skeletal stem cells (mSSCs), and bone, cartilage, stroma progenitors (BCSPs), the skeletal progenitor most important in fracture healing in the fracture callus, and we propose the mechanism for decreased bone formation after fracture is due to an effect on skeletal progenitors ability to expand after fracture. We plan on examining this first by isolating mSSCs and BCSPs, from knockout (KO) and wild type (WT) mice and comparing their biology. We will examine the biology of BCSPs using in vitro assays for cell proliferation, osteogenic and chondrogenic potential. BCSPs develop a different phenotype termed the fracture BCSP (f-BCSP) that has greater proliferative ability and osteogenic potential after fracture, and we will test whether the same change occurs in our KO mice. We will perform in vivo assays for osteogenesis by implanting BCSPs into the renal capsule to examine how well they form bone. A key question in understanding how DEL1 affects formation of bone after fracture is to understand what happens to skeletal progenitors after fracture in WT and KO mice. We will use lineage tracing techniques with mice currently in our laboratory to examine the fate of daughter cells from individual clones of skeletal progenitors cells. The final series of experiments represent our initial approaches to translating use of DEL1 into potential therapies. First, we will perform a carefully controlled microarray experiment to identify pathways altered in KO skeletal progenitors compared to WT. We will examine the ability of exogenous DEL1 to promote viability and growth of skeletal stem cells grown in vitro. We will test the ability of DEL1 to stimulate bone and cartilage formation of skeletal progenitor cells implanted into the renal capsule. Finally, we will examine whether exogenous DEL1 protein placed at a fracture site can enhance normal fracture healing. We will also use a separate model of poor fracture healing with mice that have undergone hindlimb irradiation. In summary, we will examine how Del1 affects the biology of skeletal progenitor cells. In addition to providing steps to potentially translate these discoveries into therapies, these experiments can provide us with mechanistic answers about how lack of Del1 leads to decreased bone in fracture healing. They will provide insight into the factors that affect the potential fate of skeletal progenitor cells.