Together, these data suggest that the aging-related changes in hypertension and bradycardia observed in old WT are already present in young D3KO, and they indicate that these changes with age and in D3KO may be related to an increased interstitial fibrosis in the heart, possibly mediated by collagen type-I and MMP-9 pathways. The gene discussed is MMP9; the disease is Hypertension.