Bone Marrow Cells as Precursors of Alveolar Epithelium

描述（由申请人提供）：肺损伤时，T1细胞优先受损，T1细胞代表肺的大部分气体交换表面。在目前的范例中，损伤信号T2细胞作为肺泡干细胞增殖并分化为新的T1细胞。这一过程不能充分补充T1细胞是ARDS和支气管肺发育不良等疾病死亡率和发病率的主要因素。到目前为止，由于缺乏可再生的肺泡上皮祖细胞来源，直接治疗递送替代细胞还不可行。然而，最近的研究表明，骨髓细胞可以产生以前被认为只起源于一种不同胚胎细胞层的细胞类型，这表明使用培养的骨髓细胞作为肺泡上皮细胞前体的替代来源的可能性。在这方面，我们发现静脉输送的塑料贴壁骨髓细胞（标记有大肠杆菌β -半乳糖苷酶），作为具有T1细胞形态和分子特征的细胞簇植入。在移植过程中，我们在注射后的早期和晚期时间点未检测到任何标记的T2细胞，发现T1细胞特异性表面标记物T1a在细胞掺入肺泡表面后出现表达。我们还发现骨髓细胞在气管内注射后可在大气道上皮中植入。我们的目标是通过解决与肺移植模式、T1细胞表型假设以及骨髓细胞作为分化气道上皮移植的能力相关的基本问题来扩展这些初步数据。为此，我们将确定特定骨髓标记物和肺上皮标记物作为肺细胞的表达，并分化为T1细胞。这些信息将与注射前骨髓细胞的标记分析相关联，以帮助制定策略来丰富具有移植潜力的细胞。此外，还将确定1型细胞簇形成的基础，以及不同阶段和类型的急性肺损伤对肺移植模式的作用。最后，我们将描述动力学，我们将进一步确定骨髓细胞类型移植为气道上皮。我们相信，这些研究将有助于为应用细胞疗法治疗与肺上皮表面广泛损伤相关的疾病提供基础。

DESCRIPTION (provided by applicant): During lung injury, T1 cells, which represent most of the gas-exchanging surface of the lungs are preferentially injured. In the current paradigm, injury signals T2 cells, as the stem cell of the alveolus to proliferate and to differentiate into new T1 cells. The inability of this process to sufficiently replenish T1 cells is a leading factor in the mortality and morbidity of conditions such as ARDS and broncho-pulmonary dysplasia. To date, direct therapeutic delivery of replacement cells has not been feasible because of the lack of a reproducible source of alveolar epithelial progenitors. Recent work demonstrating that bone marrow cells can give rise to cell types previously held to originate from only one of the different embryonic cell layers, however, suggests the possibility of using cultured bone marrow cells as an alternative source of alveolar epithelial cell precursors. In this regard, we found that intravenously delivered plastic adherent bone marrow cells (marked with E. Coli beta-galactosidase), engrafted as clusters of cells with the morphological and molecular characteristics of T1 cells. During engraftment, we did not detect any labeled T2 cells at early and late time points after injection and found, that expression of the T1 cell specific surface marker T1a occurs after incorporation of cells into the alveolar surface. We also found that engraftment in large airway epithelium occurred after intra-tracheal injection of marrow cells. Our objective in this proposal is to extend this preliminary data by addressing fundamental questions relating to the patterning of lung engraftment, the assumption of a T1 cell phenotype, and the capacity of marrow cells to engraft as differentiated airway epithelium. To do this, we will determine the expression of specified marrow markers and lung epithelial markers as cells home to the lung and differentiate into T1 cells. This information will be correlated with marker analyses of marrow cells prior to injection to help develop strategies to enrich for cells with engraftment potential. In addition, the basis for type 1 cell cluster formation, and the role of different phases and types of acute lung injury on the pattern of lung engraftment will be determined. Lastly, we will characterize the kinetics, and we will further identify the marrow cell type that engrafts as airway epithelium. These studies, we believe, will help provide a foundation for the application of cell-based therapies for conditions associated with extensive damage to the epithelial surfaces of the lung.