The porcine progenitor epithelial cells reported in this study share similarities with recently reported human and mouse cells that both cell types express Ccsp, but unlike human and mouse cells, porcine progenitor epithelial cells did not express mesenchymal markers such as CD29, CD44 and CD90 [13] . Porcine progenitor epithelial cells also expressed stem cell markers; Oct4 and SSEA-1; however, mouse and human cells were not tested for expression of these markers [13] . Similar to human and mouse bone marrow cells, porcine bone marrow progenitor cells expressed both Ccsp and SPC. Ccsp and SPC expressing broncho-alveolar stem cells (BACS) were recently identified in adult mouse lung [35] . Mouse BACS were found to express hematopoietic markers, whereas our porcine bone marrow progenitor epithelial cells lacked the expression of these markers. Importantly, we were able to passage progenitor epithelial cells up to passage 8 suggesting that these cells have extensive self-renewal and proliferation properties.