In Situ Regeneration of Blood Vessel

描述（由申请人提供）：心血管疾病是导致死亡的主要原因。血管置换是血管疾病的常用治疗方法。然而，自体移植物受到可用性、需要额外手术和供体部位发病率的限制，而合成血管移植物由于血栓形成和小直径移植物的衰竭而局限于大直径血管。组织工程方法很有前途，可以改善血管移植物的生物相容性和性能，但体外制造细胞移植物需要数周时间，价格昂贵，并且难以扩大临床应用。一种临床可行的策略是原位组织工程，其中无细胞、生物活性和生物可吸收的血管移植物可以有效地招募内源性细胞来自我再生血管。在过去的几年里，我们已经开发出了非细胞的、具有生物活性的微纤维血管移植物，这种移植物可以在市面上买到。移植物抗血栓形成，可以募集内皮祖细胞（EPCs），增强内皮化和长期通畅；移植物还可以招募间充质干细胞（MSCs）和生物吸收，以促进组织重塑和成熟。我们已经鉴定出一种新型的MSCs，它是Sox10+，可以在血管移植物中分化为平滑肌细胞（SMCs）。然而，MSC或SMC募集的机制仍有待确定，MMP抗劈裂基质细胞衍生因子-1a （SDF-1a）和血管移植物的孔隙度是否能导致更好的移植物性能尚不清楚。此外，在大型动物模型中验证这种新方法对于转化为临床治疗是必要的。我们推测：(1)抗MMP劈裂形式的SDF-1a， S-SDF-1（S4V）会增加其稳定性，进一步促进血管移植物的内皮化和重塑；(2)血管移植物孔隙度的增加会促进MSCs的募集/浸润，加速血管移植物的重塑；(3)在血管移植物再生过程中，MSCs而不是成熟的SMCs被募集进行重塑。为了验证我们的假设，我们提出了三个特定的目的：(1)在大鼠和小鼠谱系追踪模型中，研究S- SDF-1（S4V）是否增加EPCs和MSCs的募集和血管移植物的重塑；(2)在大鼠血管移植模型中，确定血管的孔隙度如何调节MSCs的募集和移植物的重塑；(3)在猪模型中研究S- SDF-1（S4V）和移植物孔隙度对内皮祖细胞和间充质干细胞募集、血管移植内皮化和重构的影响。该项目的完成将促进我们对干细胞和祖细胞在血管再生中的作用的理解，并将导致下一代血管移植物的发展，这些移植物是现成的，具有生物活性的，并且可以招募内源性干细胞进行原位重塑。

DESCRIPTION (provided by applicant): Cardiovascular diseases are a leading cause of death. Blood vessel replacement is a common treatment for vascular diseases. However, autologous grafts are limited by the availability, the need for additional surgeries and the morbidity of the donor sites, and synthetic vascular grafts are limited to large-diameter blood vessels due to thrombosis and failure in small diameter grafts. The tissue engineering approach is promising and can improve the biocompatibility and the performance of vascular grafts, but the in vitro fabrication of cellular grafts takes weeks, is expensive, and is difficult to scale upfor clinical applications. A clinically viable strategy is in-situ tissue engineering, wherein an acellular, bioactive and bioabsorbable vascular graft can effectively recruit endogenous cells to self-regenerate the blood vessel. In the past few years, we have developed acellular, bioactive microfibrous vascular grafts that can be made available off-the-shelf. The grafts are anti-thrombogenic and can recruit endothelial progenitor cells (EPCs) for enhanced endothelialization and long-term patency; the grafts also recruit mesenchymal stem cells (MSCs) and bioabsorb to facilitate tissue remodeling and maturation. We have identified a novel type of MSCs that are Sox10+ and can differentiate into smooth muscle cells (SMCs) in vascular grafts. However, the mechanisms of MSC or SMC recruitment remains to be determined, and whether a MMP cleavage-resistant stromal cell-derived factor-1a (SDF-1a) and the porosity of vascular grafts can lead to better graft performance is not clear. Furthermore, validation of this novel approach in a large animal model is necessary for the translation towards clinical therapies. We hypothesize that: (1) A MMP cleavage-resistant form of SDF-1a, S-SDF-1(S4V), will increase its stability and further enhance the endothelialization and the remodeling of vascular grafts, (2) the increase in the porosity of vascular grafts will facilitate the recruitment/infiltration of MSCs and accelerate vascular graft remodeling, and (3) during the regeneration of vascular grafts, MSCs rather than mature SMCs are recruited for the remodeling. To test our hypothesis, three Specific Aims are proposed: (1) To investigate whether S- SDF-1(S4V) increase the recruitment of EPCs and MSCs and the remodeling of vascular grafts in the rat and mouse lineage tracing models; (2) To determine how the porosity of vascular grafts regulate the recruitment of MSCs and the remodeling of the grafts in the rat model; (3) To investigate the effects of S- SDF-1(S4V) and graft porosity on the recruitment of EPCs and MSCs and the endothelialization and the remodeling of vascular grafts in a swine model. The accomplishment of this project will advance our understanding on the roles of stem cells and progenitor cells in the regeneration of blood vessels, and will lead to the development of the next generation of vascular grafts that are available off-the-shelf, bioactive, and can recruit endogenous stem cells for in situ remodeling.