Angiogenesis and Long-Term Bone Allograft Survival

描述（申请人提供）：本研究旨在开发一种不需要长期免疫抑制或诱导耐受的显微外科移植同种异体活体移植物替代骨和关节节段性缺损的方法。目前的重建方法不能充分复制原骨的大小、强度和功能。假体松动或骨折、晚期应力性骨折、不愈合或无法存活的同种异体移植物感染是常见的。带血管的自体移植物在大小和形状上都不合适，不能提供关节功能。显微外科移植带血管的同种异体移植物与缺损相匹配，可以提供稳定的重建，并具有良好的愈合和应激适应特性，从而改善临床结果。同种异体移植物的生存能力目前依赖于长期的免疫抑制，有潜在的严重并发症。它们的常规使用需要一种维持移植物活力而不长期免疫抑制的方法。在这些实验中，来自宿主血管的血管生成，在显微外科活骨同种异体移植时植入，将使用近交系大鼠模型来开发宿主来源的新血管生成骨循环。我们将测试在取消FK-506免疫抑制后，来自宿主维管束的新血管生成是否会维持骨血流量到血管化的异体骨移植物。观察免疫抑制、动静脉束植入及存活时间对血管生成、血管通畅及骨血流的影响。我们将使用组织形态计量学分析，探讨在血管生成手术和免疫抑制解除后，带血管的同种异体骨移植物是否维持骨重塑。我们将询问观察到的重塑是来自移植物来源的细胞，还是骨嵌合替代的影响，在性别不匹配的同种异体移植后使用Y染色体特异性标记的原位杂交。我们将证明宿主来源的内皮细胞替代和供体特异性耐受对移植物存活没有贡献。内皮细胞谱系及其与通畅的关系将评估移植物的适应性，来自相同近交系大鼠供体的第二次同种异体皮肤移植物的存活将测试供体特异性耐受的发生。临床应用的类似方法将提供用相似大小和形状的活组织替代缺失骨的能力，同时保持活骨优越的愈合和重塑能力。最重要的是，长期免疫调节的发病率和潜在死亡率可以通过维持足够长的免疫抑制时间来避免，从而使宿主衍生的血管生成发生。可以想象，其他肌肉骨骼组织也可以用类似的方法进行移植，包括部分或整个关节异体移植，甚至异种移植。

DESCRIPTION (provided by applicant): This research Aims to develop a method to replace segmental defects of bone and joint with microsurgically transferred living allografts, without need for long-term immunosuppression or induction of tolerance. Current reconstructive methods do not adequately replicate the size, strength, and function of the original bone. Prosthetic loosening or fracture, and late stress fracture, non-union or infection of non-viable allografts are common. Vascularized autografts are inadequate in size and shape, and do not provide for joint function. Microsurgical transfer of vascularized allografts matched to the defect should improve clinical outcomes, by providing a stable reconstruction combined with favorable healing and stress adaptation properties. Allograft viability currently depends upon long-term immunosuppression, with potentially serious complications. Their routine use requires a method that maintains graft viability without long-term immunosuppression. In these experiments, angiogenesis from host vessels, implanted at the time of microsurgical living bone allotransplantation, will be used to develop a host-derived neoangiogenic bone circulation using an inbred rat model. We will test whether neoangiogenesis from the host vascular bundle will maintain bone blood flow to a vascularized bone allograft after withdrawal of FK-506 immunosuppression. The effects of immunosuppression, arteriovenous bundle implantation and survival time on angiogenesis, vessel patency and bone blood flow will be determined. We will ask whether bone remodeling is maintained in vascularized bone allografts after surgical angiogenesis and withdrawal of immunosuppression using histomorphometric analysis. We will ask whether observed remodeling results from graft-derived cells, or is the effect of chimeric replacement of bone, using in situ hybridization for a Y chromosome-specific marker following sex-mismatched allotransplantation. We will demonstrate that graft adaptation by host-derived endothelial cell replacement and donor specific tolerance do not contribute to graft survival. Endothelial cell lineage, and its relationship to patency will evaluate graft adaptation, and survival of a second allogeneic skin graft from identical inbred rat donors will test the occurrence of donor-specific tolerance. Similar methods applied clinically would provide the ability to replace missing bone with living tissue of similar size and shape, while maintaining the superior healing and remodeling abilities of living bone. Most importantly, the morbidity and potential mortality of long-term immune modulation are obviated by immunosuppression maintained only long enough for host-derived vessel angiogenesis to occur. It is conceivable that other musculoskeletal tissues could be transplanted using similar methods, including partial or whole joint allo- or even xenotransplants.