MMP9 and diabetes mellitus: Meanwhile, diabetes-induced myocardial fibrosis, as evaluated by Masson trichrome staining and Sirius Red staining (Fig. 8I to K) and TGFβ/MMP9 transcription (Fig. 8I to K), were also partly attenuated in diabetic Phb2S91D/+ mice and undetectable in diabetic Phb2S91D/D mice (Fig. 8L and M).