Mesenchymal Stem Cells in the Treatment of Lung Fibrosis

描述(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。干细胞疗法可能是修复受损肺的一种可行的选择。本实验室建立了一种从小鼠骨髓中分离间充质干细胞(MSCs)的可靠方法。MSC移植于小鼠肺内，采用肺泡上皮(AE)II型细胞表型，并明显减轻博莱霉素所致的炎症程度和胶原沉积。骨髓间充质干细胞的特点是CD44抗原表达均匀。CD44是骨桥蛋白(OPN)的受体。CD44和OPN在正常肺组织中低水平表达，在肺损伤过程中表达显著增强，CD44与OPN的相互作用可能在介导MSC在肺内植入的范围和解剖位置中发挥重要作用。肺移植后，MSCs的表型为AEII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，目前尚不清楚。MSCs在体外经历了上皮分化，我们的数据表明，这一过程与抑制MSCs的有丝分裂原FGF2和顺序激活BMP受体IA和IB有关。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，BMPR-IB的激活随后促进末端分化。MSCs结构性表达BMPR-IA，但不表达BMPR-IB。我们假设抑制FGF2促进了BMPR-IB的表达，促进了上皮MSC的分化。此外，我们假设在非炎性条件下，通过诱导骨桥蛋白的受控表达，MSC的植入可能被增强并靶向于肺上皮细胞。最后，我们推测，外源性给予MSCs植入肺内可以改善肺损伤。因此，骨髓间充质干细胞可能会被操纵，将治疗性基因输送到受损的肺。为了验证这些假说，我们提出了以下具体目标：1)确定MSCs分化为上皮细胞命运的分子机制。2)探讨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)探讨全身应用间充质干细胞能否改善损伤肺的纤维增生性反应。

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.