Transforming growth factor-β1 SMAD effectors and medial cell number in ascending aorta diseases

In ascending aorta aneurysms and dissections, the extracellular matrix is degraded. Transforming growth factor (TGF)-β1 modulates its synthesis. The production and presence of SMADs, intracellular effectors of TGF-β1 signaling, were analyzed in patients with these diseases. To verify whether medial cells are lost, their total numbers were computed. Ascending aorta samples from 19 patients and 18 controls underwent immunoperoxidase reactions to SMADs 2, 3, 4, and 7. Positive and negative cells were counted, and total numbers of cells and positive/total ratios were calculated. Samples from other 14 patients and 7 normal controls were used for the quantification of SMAD3, SMAD4, and SMAD7 mRNA. For SMAD4, both mRNA (2.36 vs. 0.37, P = .03) and ratio of positive cells (0.94 vs. 0.73, P = .02) are increased in patients with ascending aortic diseases. SMAD3 mRNA was also increased (1.19 vs. 0.20, P = .05). The cell ratios of this and the other SMADs, SMAD7 mRNA, and the total cell count did not differ between groups. In conclusion, in ascending aortic aneurysms and dissections, there is an increase in SMAD4, implicated in extracellular matrix production, possibly as an attempt to compensate for extracellular matrix deficiency. Lost medial cells are replaced, since their number is not diminished.