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以高死亡率为特征的致残性疾病。基于干细胞的疗法可能是修复受损肺的可行替代方案。我们的实验室已经开发了一种可靠的方法，基于免疫耗竭，从小鼠骨髓中分离间充质干细胞（MSCs）。MSC移植到小鼠肺内，采用肺泡上皮（AE）II型细胞表型，并显著降低炎症程度和胶原沉积对博莱霉素的反应。MSC的特征在于其CD 44抗原的均匀表达。CD 44是骨桥蛋白（OPN）的受体。OPN在正常肺中以低水平表达，在肺损伤期间OPN表达大大增强，因此，CD 44和OPN之间的相互作用可能在介导MSC在肺中植入的程度和解剖位置中起重要作用。肺移植后，MSC采用AE II型表型。这是细胞融合的结果还是高度调节的细胞分化程序的产物尚不清楚。MSC在体外经历上皮分化，并且我们的数据表明，该过程与FGF 2（MSC的有丝分裂原）的抑制以及BMP受体IA和IB的顺序活化相关。BMPR-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，然后BMPR-IB的激活促进终末分化。MSC组成型表达BMPR-IA，但缺乏BMPR-IB的表达。我们推测抑制FGF 2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，MSC植入可能会增强，并通过诱导骨桥蛋白的表达控制肺上皮细胞的目标。最后，我们假设外源性间充质干细胞移植到肺内，并改善肺损伤。因此，可以操纵MSC以将治疗基因递送到受损的肺。为了验证这些假设，我们提出了以下具体目标：1）确定调控MSC分化为上皮细胞命运的分子机制。2)目的：探讨CD 44/骨桥蛋白相互作用在骨髓间充质干细胞移植入小鼠肺中的作用。3)为了确定是否可以使用MSC的全身给药来改善在损伤的肺中观察到的纤维增生反应。

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.