Stem cell homing/engraftment in lung injury and repair

描述（由申请人提供）： 啮齿类动物的移植研究表明，损伤后，器官可以通过从骨髓中募集的前体细胞重新增殖，这表明成人骨髓源性干细胞具有相当大的可塑性。鉴定人骨髓中的全能性未定型干细胞群体对于包括肺在内的受损器官的再生将具有巨大的临床益处，并且表明通过外源性施用的免疫相容性干细胞损伤后肺泡上皮细胞再增殖的可能性。本提案的目的是确定产生肺泡上皮细胞表型的人类干细胞群体和植入环境，其长期目标是改善损伤后的肺泡上皮再生和肺功能恢复。我们假设：1）当体内移植到小鼠中时或当体外培养时，骨髓来源的人干细胞的特定亚群具有由肺微环境决定的不同谱系潜力，和2）人干细胞在肺中的移植和体外和体内向肺泡上皮表型的分化通过已知在肺损伤后局部释放的生长因子而增强。利用我们在干细胞和肺泡上皮细胞生物学方面的综合专业知识、已建立的人类移植异种移植模型和肺泡上皮细胞培养体外系统的可用性，我们将通过解决以下具体目标来研究这些假设：1）研究分级分离的人干细胞在肺损伤后重新填充免疫缺陷小鼠的远端肺上皮的能力，和2）分析微环境对分离的人干细胞体外分化的影响。拟定的研究将研究确定的人骨髓源干细胞群（间充质塑料粘附与造血非粘附）重新填充受损肺泡上皮的能力，并比较静脉内与静脉内给药的效率。将采用体外和体内方法的组合来评价因素（例如，肝细胞生长因子和角质形成细胞生长因子），其增强人干细胞募集或诱导向远端肺上皮表型分化。鉴定具有产生分化细胞类型的能力的成人干细胞群体将为损伤后肺（和其他器官）的修复提供非凡的治疗潜力。

DESCRIPTION (provided by applicant): Transplantation studies in rodents indicate that following injury, organs can be repopulated by precursor cells recruited from bone marrow, suggesting considerable plasticity of marrow-derived stem cells in the adult. Identification of a totipotent uncommitted stem cell population in human bone marrow would be of enormous clinical benefit for regeneration of injured organs including the lung, and suggests the possibility for repopulation of the pulmonary alveolar epithelium following injury by exogenously administered immunologically compatible stem cells. The objective of this proposal is to define human stem cell populations and implantation environments that generate lung alveolar epithelial cell phenotypes, with the long-range goal of improving alveolar reepithelialization and restoration of lung function following injury. We hypothesize that: 1) specific subsets of marrow-derived human stem cells have different lineage potential determined by the lung microenvironment when transplanted into mice in vivo or when cultured in vitro, and 2) human stem cell engraftment in the lung and differentiation towards an alveolar epithelial phenotype in vitro and in vivo is enhanced by growth factors known to be released locally following lung injury. Capitalizing on our combined expertise in stem and alveolar epithelial cell biology, availability of established xenograft models for human transplantation and in vitro systems for alveolar epithelial cell culture, we will investigate these hypotheses by addressing the following Specific Aims: 1) Investigate the ability of fractionated human stem cells to repopulate the distal lung epithelium of immune deficient mice following lung injury and 2) Analyze in vitro the effects of microenvironment on differentiation of fractionated human stem cells. The proposed studies will investigate the capacity of defined populations of human marrow-derived stem cells (mesenchymal plastic-adherent vs. hematopoietic non-adherent) to repopulate the injured alveolar epithelium, and compare the efficiency of intravenous vs. intratracheal administration. A combination of in vitro and in vivo approaches will be applied to evaluate factors (e.g., hepatocyte growth factor and keratinocyte growth factor) in the local lung milieu that augment human stem cell recruitment or induce differentiation towards a distal lung epithelial phenotype. Identification of an adult human stem cell population with the ability to generate differentiated cell types would offers extraordinary therapeutic potential for repair of the lungs (and other organs) following injury.