title: Evidence that bone marrow cells do not contribute to the alveolar epithelium.
abstract: An ongoing controversy is the role of marrow cells in populating the alveolar epithelium. In this study, we employed flow cytometry and histologic techniques to evaluate this process. Donor bone marrow was harvested from transgenic mice expressing the LacZ or eGFP gene ubiquitously, or under the control of the human surfactant protein (SP)-C promoter, and transplanted into lethally irradiated, neonatal mice. In recipients transplanted with marrow that express eGFP or lacZ ubiquitously, light microscopy revealed cells whose morphology and location were compatible with a type II cell phenotype. Consistent with this, fluorescent microscopy suggested colocalization of eGFP and pro-SP-C proteins in single cells. In mice transplanted with SP-C-eGFP marrow, engraftment was not detectable by histology or flow cytometry. We therefore used deconvolution microscopy to reanalyze histologic sections that were thought to show marrow-derived type II cells. We found that all putative marrow-derived pneumocytes resulted from the overlapping fluorescent signals of an endogenous pro-SP-C+ type II cell and a donor-derived eGFP+ cell. Taken together, our observations underscore the technical difficulties associated with evaluating engraftment in lung, and argue against a contributory role for marrow cells in populating the alveolar epithelium.
authors.affiliation: The Pulmonary Center, Boston University School of Medicine, Boston, MA 02118, USA. jachang@lung.bumc.bu.edu
authors.forename: Jacqueline C
authors.initials: JC
authors.lastname: Chang
authors.forename: Ross
authors.initials: R
authors.lastname: Summer
authors.forename: Xi
authors.initials: X
authors.lastname: Sun
authors.forename: Kathleen
authors.initials: K
authors.lastname: Fitzsimmons
authors.forename: Alan
authors.initials: A
authors.lastname: Fine
mesh_terms: D000818:Animals; D001854:Bone Marrow Cells / Q000166:cytology / Q000502:physiology*; D016026:Bone Marrow Transplantation; D002469:Cell Separation; D005434:Flow Cytometry; D017930:Genes, Reporter; D049452:Green Fluorescent Proteins / Q000235:genetics / Q000378:metabolism; D006801:Humans; D051379:Mice; D008822:Mice, Transgenic; D008853:Microscopy / Q000379:methods; D010455:Peptides / Q000235:genetics / Q000378:metabolism; D011650:Pulmonary Alveoli / Q000166:cytology*; D037721:Pulmonary Surfactant-Associated Protein C; D020545:Respiratory Mucosa / Q000166:cytology* / Q000378:metabolism
chemical_list: D010455:Peptides; D037721:Pulmonary Surfactant-Associated Protein C; C489679:SFTPC protein, human; D049452:Green Fluorescent Proteins