This finding gives rise to the possibility that notochordal cells play an important role in matrix homeostasis, providing a plausible explanation for the observed higher baseline expression levels of MMPs, ADAMTSs, and TIMPs in the NP than in the AF and differential imbalanced pattern of ADAMTS-4 and ADAMTS-5/TIMP-3 between the NP and AF. The gene discussed is ADAMTS4; the disease is atrial fibrillation.