Identification of mesenchymal stromal cells in lung tissue from lung-transplanted patients

Background: Multipotent mesenchymal stromal cells (MSC) have been isolated from a variety of human tissues. Previous studies have shown that MSC are present in the bronchoalveolar fluid from lung-transplanted patients where they were suggested to be an indication of a future bronchiolitis obliterans syndrome (BOS) onset. We hypothesize that MSC are lung-resident cells that are present in lung tissue from lung-transplanted patients. Objective: Our aims were to examine whether MSC are present in lung tissue from lung-transplanted patients and to evaluate whether these cells showed typical MSC characteristics such as adherent clonal growth and multi-lineage differentiation capacity. Methods: MSC were isolated from central- and distal biopsies obtained from lung-transplanted patients (3 mo. – 13 yrs. post transplantation). After dissociation, the resulting single cell suspension was subjected to colony-forming unit-fibroblast (CFU-F) assays to determine the frequency of mesenchymal progenitor cells. Further, the cells were assayed for their differentiation capacity towards adipocytes, chondrocytes and osteoblasts. The surface marker profile of lung-derived MSC was examined by flow cytometry. Results: MSC isolated from lung tissue adhered to tissue culture treated plastic, formed colonies when cultured in CFU-f assays and possessed multi-lineage potential. Immunophenotyping showed that lung-derived MSC were positive for the surface markers such as CD73, CD90 and CD105 and negative for CD45 and CD34. Conclusion: Our study suggests that there are MSC present in the lung tissue of lung-transplanted patients that possess multi-lineage potential and give rise to typical colonies in vitro .