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Increased TGFβ1 and SMAD3 Contribute to Age-Related Aortic Valve Calcification
Mrinmay Chakrabarti1, Aniket Bhattacharya1,2, Mengistu G Gebere1
1Department of Cell Biology and Anatomy, School of Medicine, University of South Carolina, Columbia, SC, United States.
Insights
Inhibition of TGFβ1 and SMAD3 signaling pathways rescues calcific aortic valve disease (CAVD) in klotho knockout mice. This finding offers potential for new pharmacological treatments for CAVD.
Area of Science:
- Cardiovascular Biology
- Aging Research
- Molecular Biology
Background:
- Calcific aortic valve disease (CAVD) is a prevalent heart condition in the elderly, currently managed with challenging surgical valve replacement.
- The aging-suppressor gene klotho plays a critical role in aortic valve calcification, with klotho knockout mice exhibiting severe calcification and reduced lifespan.
- Increased TGFβ1 and SMAD3 signaling are associated with AV calcification in klotho-deficient models.
Purpose of the Study:
- To investigate the potential of inhibiting TGFβ1 and SMAD3 signaling pathways to rescue aortic valve calcification.
- To determine the contribution of TGFβ1 and SMAD3 to AV calcification in klotho knockout mice.
Main Methods:
- Generated klotho knockout mice with heterozygous deficiency in Tgfb1 or Smad3.
- Evaluated aortic valve calcification using histological and morphometric analyses.
- Assessed gene expression of key calcification markers and TGFβ signaling components via mRNA and Western blot analyses.
Main Results:
- Significant reduction in aortic valve calcification was observed in klotho knockout mice with heterozygous deletion of Tgfb1 or Smad3.
- Smad3 heterozygous deletion was more potent in reducing AV calcification than Tgfb1 heterozygous deletion.
- Inhibition of TGFβ1, Pai1, Bmp2, Alk2, Spp1, and Runx2 mRNA expression was noted in both genetically modified groups.
- Western blot confirmed the inhibition of TGFβ canonical and non-canonical signaling pathways.
Conclusions:
- Inhibition of the TGFβ1-dependent SMAD3 signaling pathway effectively blocks the development of AV calcification in klotho knockout mice.
- These findings provide valuable insights into the signaling mechanisms underlying CAVD.
- Targeting TGFβ1-SMAD3 signaling presents a promising avenue for pharmacological intervention in CAVD.
Aims:
Calcific aortic valve disease (CAVD) is a progressive heart disease that is particularly prevalent in elderly patients. The current treatment of CAVD is surgical valve replacement, but this is not a permanent solution, and it is very challenging for elderly patients. Thus, a pharmacological intervention for CAVD may be beneficial. In this study, we intended to rescue aortic valve (AV) calcification through inhibition of TGFβ1 and SMAD3 signaling pathways.
Methods And Results:
The klotho gene, which was discovered as an aging-suppressor gene, has been observed to play a crucial role in AV calcification. The klotho knockout (Kl -/-) mice have shorter life span (8-12 weeks) and develop severe AV calcification. Here, we showed that increased TGFβ1 and TGFβ-dependent SMAD3 signaling were associated with AV calcification in Kl -/- mice. Next, we generated Tgfb1- and Smad3-haploinsufficient Kl -/- mice to determine the contribution of TGFβ1 and SMAD3 to the AV calcification in Kl -/- mice. The histological and morphometric evaluation suggested a significant reduction of AV calcification in Kl -/-; Tgfb1 ± mice compared to Kl -/- mice. Smad3 heterozygous deletion was observed to be more potent in reducing AV calcification in Kl -/- mice compared to the Kl -/-; Tgfb1 ± mice. We observed significant inhibition of Tgfb1, Pai1, Bmp2, Alk2, Spp1, and Runx2 mRNA expression in Kl -/-; Tgfb1 ± and Kl -/-; Smad3 ± mice compared to Kl -/- mice. Western blot analysis confirmed that the inhibition of TGFβ canonical and non-canonical signaling pathways were associated with the rescue of AV calcification of both Kl -/-; Tgfb1 ± and Kl -/-; Smad3 ± mice.
Conclusion:
Overall, inhibition of the TGFβ1-dependent SMAD3 signaling pathway significantly blocks the development of AV calcification in Kl -/- mice. This information is useful in understanding the signaling mechanisms involved in CAVD.
