Mesenchymal Stem Cells In The Treatment of Lung Fibrosis

描述（由申请人提供）：特发性肺纤维化是一种致残性疾病，其特点是死亡率高。基于干细胞的治疗可能是修复损伤肺的一种可行的替代方法。本实验室开发了一种可靠的基于免疫消耗的方法从小鼠骨髓中分离间充质干细胞（MSCs）。骨髓间充质干细胞移植小鼠肺，采用肺泡上皮（AE） II型细胞表型，对博来霉素的反应明显降低炎症程度和胶原沉积。间充质干细胞的特点是其CD44抗原的均匀表达。CD44是骨桥蛋白（OPN）的受体。OPN在正常肺中表达水平较低，但在肺损伤时表达水平显著增强，因此，CD44与OPN的相互作用可能在调节MSC在肺中植入的程度和解剖位置方面发挥重要作用。肺移植后MSCs呈AE II型表型。这是细胞融合的结果还是高度调控的细胞分化程序的产物尚不清楚。MSCs在体外经历上皮分化，我们的数据表明这一过程与FGF2 （MSCs的有丝分裂原）的抑制以及BMP受体IA和IB的顺序激活有关。BMP -IA的激活指示干细胞致力于特定的命运并诱导BMPR-IB的表达，其激活随后促进最终分化。MSCs组成性地表达bbmpr - ia，但缺乏bbmpr - ib的表达。我们假设抑制FGF2促进BMPR-IB的表达并促进上皮MSC分化。此外，我们假设在非炎症条件下，通过诱导骨桥蛋白的控制表达，MSC植入可能被增强并靶向到肺上皮。最后，我们假设外源性MSCs移植到肺中可以改善肺损伤。因此，MSCs可以被操纵以将治疗基因传递到受损的肺。为了验证这些假设，我们提出以下具体目标：1)确定调节MSCs分化为上皮细胞命运的分子机制。2)确定CD44/骨桥蛋白相互作用在小鼠肺间充质干细胞移植中的作用。3)确定全身给药MSCs是否可以改善损伤肺中观察到的纤维增殖反应。

DESCRIPTION (provided by applicant): Idiopathic pulmonary fibrosis is a crippling disease characterized by high mortality. Stem cell based therapies may represent a viable alternative to repair injured lung. Our laboratory has developed a reliable method based on immunodepletion to isolate mesenchymal stem cells (MSCs) from the bone marrow of mice. MSC engraft in mouse lung, adopt alveolar epithelial (AE) type II cell phenotype, and significantly reduced the extent of inflammation and collagen deposition in response to bleomycin. MSC are characterized by their uniform expression of the CD44 antigen. CD44 is a receptor for osteopontin (OPN). Expressed at low levels in normal lung, OPN expression is greatly enhanced during lung injury and therefore, interactions between CD44 and OPN may play an important role in mediating the extent and anatomical location of MSC engraftment in lung. Following lung engraftment MSCs adopt AE type II phenotype. Whether this is the result of cell fusion or the product of a highly regulated cell differentiation program is unknown. MSCs undergo epithelial differentiation in vitro and our data has shown that this process is associated suppression of FGF2, a mitogen for MSCs, and sequential activation of the BMP receptors IA and IB. Activation of BMPR-IA instructs stem cells to commit to a particular fate and induces expression of BMPR-IB, activation of which then promotes terminal differentiation. MSCs constitutively express BMPR-IA but lack expression of BMPR-IB. We hypothesize that inhibition of FGF2 facilitates expression of BMPR-IB and promotes epithelial MSC differentiation. In addition, we hypothesize that under non-inflammatory conditions MSC engraftment may be enhanced and targeted to the lung epithelium by inducing the controlled expression of osteopontin. Finally, we postulate that exogenously administered MSCs engraft in the lung and ameliorate lung injury. Thus, MSCs may be manipulated to deliver therapeutic genes to the injured lung. To test these hypotheses we propose the following specific aims: 1) To determine the molecular mechanism that regulates differentiation of MSCs into epithelial cell fate. 2) To determine the role that CD44/osteopontin interactions play during MSC engraftment in the mouse lung. 3) To determine whether or not the systemic administration of MSCs can be used to ameliorate the fibroproliferative responses observed in the injured lung.