Following damage, the majority of bone marrow-derived airway cells express an epithelial marker.
BACKGROUND
Adult-derived bone marrow stem cells are capable of reconstituting the haematopoietic system. However there is ongoing debate in the literature as to whether bone marrow derived cells have the ability to populate other tissues and express tissue specific markers. The airway has been an organ of major interest and was one of the first where this was demonstrated. We have previously demonstrated that the mouse airway can be repopulated by side population bone marrow transplanted cells. Here we investigate the frequency and phenotypic nature of these bone marrow derived cells.


METHODS
Female mice were engrafted with male whole bone marrow or side population (SP) cells and subjected to detergent-induced damage after 3 months. Donor cells were identified by Y chromosome fluorescence in situ hybridisation and their phenotype was assessed by immunohistochemistry on the same sections. Slides were visualised by a combination of widefield and deconvolved microscopy and whole cells were analysed on cytospin preparations.


RESULTS
The frequencies of engraftment of male cells in the airway of mice that show this (9/10), range from 1.0-1.6% with whole marrow and 0.6-1.5% with SP cells. Undamaged controls have only between 0.1 and 0.2% male cells in the trachea. By widefield microscopy analysis we find 60.2% (53/88) of male donor derived cells express cytokeratins as a marker of epithelial cells. These results were reinforced using deconvolved microscopy and scored by two independent investigators. In addition cytospin analysis of cells dissociated from the damaged trachea of engrafted mice also reveals donor derived Y chromosome positive cells that are immunopositive for cytokeratin. Using cytokeratin and the universal haematopoietic marker CD45 immunohistochemistry, we find the donor derived cells fall into four phenotypic classes. We do not detect cytokeratin positive cells in whole bone marrow using cytokeratin immunostaining and we do not detect any cytokeratin mRNA in SP or bone marrow samples by RT-PCR.


CONCLUSIONS
The appearance of bone marrow derived cells in the tracheal epithelium is enriched by detergent-induced tissue damage and the majority of these cells express an epithelial marker. The cytokeratin positive donor derived cells in the tracheal epithelium are not present in the injected donor cells and must have acquired this novel phenotype in vivo.
MacPherson
Heather
H
MRC Human Genetics Unit, Western General Hospital, Crewe Road South, Edinburgh EH4 2XU, UK. heather.macpherson@hgu.mrc.ac.uk
Keir
Pamela A
PA
Edwards
Carol J
CJ
Webb
Sheila
S
Dorin
Julia R
JR
D000818:Animals; D015415:Biomarkers / Q000378:metabolism; D001854:Bone Marrow Cells / Q000378:metabolism / Q000473:pathology*; D016026:Bone Marrow Transplantation / Q000379:methods*; D002454:Cell Differentiation; D002478:Cells, Cultured; D004847:Epithelial Cells / Q000378:metabolism / Q000473:pathology*; D005260:Female; D017493:Leukocyte Common Antigens / Q000378:metabolism; D008297:Male; D051379:Mice; D020545:Respiratory Mucosa / Q000378:metabolism / Q000473:pathology; D014132:Trachea / Q000378:metabolism / Q000473:pathology* / Q000601:surgery; D014133:Tracheal Diseases / Q000378:metabolism / Q000473:pathology* / Q000601:surgery
D015415:Biomarkers; D017493:Leukocyte Common Antigens