Western blot analysis of MMP9 protein expression in homozygous B-hMMP9 mice. Various tissue lysates were collected from C57BL/6N wild-type (+/+) mice and homozygous B-hMMP9 (H/H) mice, and then analyzed by western blot with anti-MMP9 antibody. 40 μg total proteins were loaded for western blotting analysis. MMP9 was detected in bone marrow, lymph node, lung and spleen both from wild-type and homozygous mice, as the antibody is cross-recognized both for human mouse MMP9. The molecular weight of mouse MMP9 is slight bigger than that of human MMP9, which might be mainly due to the number of amino acids and the post-transcriptional modification.

Strain specific analysis of MMP9 mRNA expression in wild-type C57BL/6N mice and B-hMMP9 mice by RT-PCR. Lung RNA were isolated from wild-type C57BL/6N mice (+/+) and homozygous B-hMMP9 mice (H/H), then cDNA libraries were synthesized by reverse transcription, followed by PCR with mouse or human MMP9 primers. Mouse Mmp9 mRNA was detectable only in wild-type C57BL/6N mice. Human MMP9 mRNA was detectable in homozygous B-hMMP9 mice but not in wild-type mice. And the PCR products were confirmed with Sanger sequencing.