Cell delivery for irradiated bone defects

描述（由申请人提供）：受辐射患者的骨愈合受损是由于局部细胞群损伤和脉管系统受损。细胞疗法是组织移植的一种强有力的替代方法，但其临床应用需要易于获得的人类细胞，具有血管生成潜力，并在适当的刺激下有助于骨形成。内皮集落形成细胞（ecfc）是内皮祖细胞的一个亚群，在缺氧条件下表现出强大的血管生成潜力，并能在体内形成功能性血管网络。间充质干细胞（MSCs）是一种易于获取、增殖迅速、具有成骨潜能和支持毛细血管形成的细胞。成功的骨愈合细胞疗法将通过利用能够协同促进组织修复的群体来确定，当将移植群体定位到缺陷部位时，同时也促进和增强细胞存活、增殖和分化。纤维蛋白凝胶模仿天然骨折部位愈合的第一步血块，因为它们具有生物可吸收性，可注射性，纤维蛋白可以从患者自己的血液中制备，并且像天然血块一样，它们有效地保持对愈合至关重要的细胞。纤维蛋白凝胶的化学和机械性能可以通过修改凝血蛋白的相对浓度来调整。较硬的基质驱动干细胞和祖细胞形成骨。作为增加纤维蛋白凝胶硬度所需的高凝血蛋白浓度的替代方法，我们最近开发了一种通过操纵离子强度来增加纤维蛋白凝胶硬度的方法。我们的中心假设是，具有增强物理特性的纤维蛋白凝胶将是直接参与新生血管和骨形成的细胞群共移植的有效载体。目的1。测定在硬度增加的纤维蛋白凝胶中共同培养的ecfc和MSCs的血管生成和成骨潜能。工程纤维蛋白凝胶支持被包裹细胞血管生成和成骨反应的能力将被量化。在辐照的啮齿动物颅骨缺损模型中，评估纤维蛋白凝胶内ecfc和MSCs共移植增强血管化和骨形成的能力。植入细胞对组织灌注和骨形成的贡献将通过无创成像方式进行评估。这项提议的研究具有创新性，因为它利用了组织愈合的天然参与者，纤维蛋白和组织形成细胞，来克服组织微环境中抑制正常修复的因素。我们将阐明ecfc和MSCs移植到头颈癌患者的辐照骨缺损时的作用。总的来说，这项研究将填补我们对血管和基质细胞如何促进毛细血管形成和组织修复的理解的关键空白，这些研究与治疗不可愈合的骨缺损、软组织缺损以及组织工程和再生医学的新兴应用直接相关。

DESCRIPTION (provided by applicant): Impaired bone healing in irradiated patients results from damage to local cell populations and a compromised vasculature. Cell-based therapies represent a powerful alternative to tissue grafts, yet their clinical application requires human cells that can be readily obtained, possess angiogenic potential, and contribute to bone formation upon appropriate stimulation. Endothelial colony forming cells (ECFCs) are a subpopulation of endothelial progenitor cells that exhibit robust angiogenic potential under hypoxic conditions and can form functional vascular networks in vivo. Mesenchymal stem cells (MSCs) are easily retrievable and proliferate rapidly, possess osteogenic potential, and support capillary formation. Successful cell-based therapies for bone healing will be identified by utilizing populations that can synergistically contribute to tissue repair when delivered with a matrix that localizes transplanted populations to the defect site, while also facilitating and enhancing cell survival, proliferation, and differentiation. Fibrin gels mimic the blood clot that is the first step of healing in a natural fracture site and are appealing because they are bioresorbable, injectable, the fibrin can be prepared from the patient's own blood and, like a natural blood clot, they effectively hold cells critical to healing. Chemical and mechanical properties of fibrin gels may be tailored by modifying the relative concentrations of clotting proteins. Stiffer substrates drive bone formation with stem and progenitor cells. As an alternative to high clotting protein concentrations necessary to increase fibrin gel stiffness, we recently developed a method for increasing the stiffness of fibrin gels by manipulating ionic strength. Our central hypothesis is that fibrin gels with enhanced physical properties will be effective vehicles for cotransplanting cell populations that directly participate in neovascularization and bone formation. Aim 1. Determine the vasculogenic and osteogenic potential of ECFCs and MSCs co-cultured within fibrin gels possessing increased stiffness. The ability of engineered fibrin gels to support the vasculogenic and osteogenic response of entrapped cells will be quantified. Assess the ability of ECFCs and MSCs cotransplanted within fibrin gels to enhance vascularization and bone formation in an irradiated rodent calvarial defect model. The contribution of implanted cells toward tissue perfusion and bone formation will be assessed using noninvasive imaging modalities. The proposed research is innovative because it exploits natural participants of tissue healing, fibrin and tissue-forming cells, to overcome tissue microenvironments that inhibit normal repair. We will elucidate the contributions of ECFCs and MSCs when implanted into an irradiated bone defects characteristic of patients with head and neck cancer. Collectively, this research will fill a critical void in our understanding of how vascular and stromal cells promote capillary vessel formation and tissue repair, and these studies have direct relevance for treating nonhealing bone defects, soft tissue defects, and emerging applications in tissue engineering and regenerative medicine. PUBLIC HEALTH RELEVANCE: The development of new cell delivery strategies that accelerate tissue formation and function upon implantation will greatly improve the quality of life for those who suffer from nonhealing tissue defects. We seek to determine if engineered fibrin gels possessing increased stiffness can promote vascularization and bone formation by transplanted vessel- and bone-forming cells.