Hmox1 mRNA expression and quantification of Hmox1^+/+ DNA in transplanted Hmox1^−/− animals.Hmox1 mRNA expression levels in the tissues of KO BMT animals were partially restored to normal in the BM (A) and spleen (B), were twofold higher in the liver (C), and were negligibly low in the kidney (D) in comparison with WT animals. Data were obtained by quantitative reverse-transcription polymerase chain reaction. ND, not detected. (E) Percentage of WT cells in the tissues of KO BMT animals, as assessed by quantification of the WT Hmox1 gene in a total genomic DNA extracts; we observed that liver had the highest number of donor cells of the 3 key tissues analyzed, at 3%. Primers that target exon 3 of the Hmox1 gene, which was deleted in Hmox1^−/− mice, were used for the quantification.