Role of pluripotent stem cells (PSCs) isolated from adult tissue in bone tissue regeneration

虽然轻微的骨损伤会自行愈合和/或再生，但先天性异常、创伤和手术切除病变组织导致的严重缺陷会压倒骨再生能力，导致多次昂贵的干预，并延长患者的痛苦。目前的治疗已经取得了不同程度的成功，然而与几个缺点相关。 组织工程（TE）技术，使用不同的组合，支架，生长因子和骨祖细胞，直接应用于骨缺损;持有很大的希望，实现最佳愈合，同时消除许多缺点。使用这些技术，我们和其他人已经纯化和扩增MSC，EPC和BM-MNC，并以不同的组合将它们接种到支架上，在动物模型中，治疗大的骨缺损，并已证明改善骨愈合。虽然大多数纯化细胞的组合促进愈合，但我们惊讶地发现，愈合的速度和质量并没有明显优于自体骨移植的常规治疗。这些意想不到的发现使我们重新检查BM-MNC部分中自体移植物的成分，试图确定哪些是促进观察到的骨愈合增强的主要因素。用于这些治疗的BM-MNC由含有间充质干细胞、造血祖细胞、内皮祖细胞和多能干细胞的单核细胞的异质混合物组成。后者已经由几个小组描述，并且取决于所使用的分离方案，已经分配了不同的名称;孢子样干细胞、多能成体干细胞（MASC）、多谱系分化应激耐受（Muse）细胞、多能成体祖细胞（MAP）、非常小的胚胎样干细胞（VSEL）。在大多数成人组织中发现了VSEL细胞，在体内模型中显示出多能性，并显示出刺激新骨形成。基于上述，我们形成了一个假设，即BM-MNC中的VSEL细胞在损伤后的骨再生反应中起关键作用。为了验证这一假设，我们将测量和比较BM-MNC，有和没有VSEL细胞，和VSEL细胞单独，在大鼠股骨临界尺寸骨缺损模型的骨愈合的影响。我们将结构的实验，以回答以下问题：是VSEL细胞，或其后代，目前在愈合骨在大鼠股骨？如果是这样，VSEL细胞是否有助于在基于BM-MNC的治疗中观察到的促愈合反应？VSEL细胞对骨愈合的哪些方面有贡献？

While minor bone injuries heal and/or regenerate on their own, major defects caused by congenital anomalies, trauma and surgical excision of diseased tissues, overwhelm bones regenerative capacity, resulting in multiple and costly interventions, and prolonged patient suffering. Current treatments have met with varying degrees of success, however are associated with several drawbacks. Tissue engineering (TE) techniques, that use different combinations of, scaffolds, growth factors, and osteoprogenitor cells, applied directly into the bone defect; hold great promise for achieving optimal healing, while eliminating many of the drawbacks. Using these techniques we and others have purified and expanded MSC, EPC and BM-MNC, and in different combinations have seeded them onto scaffolds and, in animal models, treated large bone defects, and have demonstrated improved bone healing.While most combinations of purified cells promote healing, we were surprised to find that the rate and quality of healing was not significantly better than, conventional treatment with autologous bone grafts. These unexpected findings led us to reexamine the constituents of autologous grafts, in the BM-MNC fraction, in an attempt to identify which is/are the primary actor(s) promoting the observed enhanced bone healing. The BM-MNC used in these treatments consists of a heterogeneous mix of mononuclear cells containing mesenchymal stem cells, hematopoietic progenitor cells, endothelial progenitor cells, and pluripotent stem cells. The latter have been described by several groups, and depending on the isolation protocol used, have been assigned different names; spore-like stem cells, multipotent adult stem cells (MASCs), multilineage-differentiating stress enduring (Muse) cells, multipotent adult progenitor cells (MAPs), very small embryonic-like stem cells (VSEL). They have been found in most adult tissues, have been shown to be pluripotent in an in vivo models and have been shown to stimulate new bone formation.Based on the above we formed a hypothesis that VSEL cells, within BM-MNC, play a key role in the regenerative response in bone following injury. To test this hypothesis, we will measure and compare the effects of BM-MNC, with and without VSEL cells, and VSEL cells alone, on bone healing in a rat femur critical size bone defect model. We will structure the experiments in order to answer the following questions: Are VSEL cells, or their descendants, present in healing bone in the rat femur? If so do VSEL cells contribute to the pro-healing response observed in BM-MNC based treatments? And what aspect of bone healing do VSEL cells contribute to?