Anti-TGFβ (Transforming Growth Factor β) Therapy With Betaglycan-Derived P144 Peptide Gene Delivery Prevents the Formation of Aortic Aneurysm in a Mouse Model of Marfan Syndrome

Objective

We investigated the effect of a potent TGFβ (transforming growth factor β) inhibitor peptide (P144) from the betaglycan/TGFβ receptor III on aortic aneurysm development in a Marfan syndrome mouse model.

Approach and Results

We used a chimeric gene encoding the P144 peptide linked to apolipoprotein A-I via a flexible linker expressed by a hepatotropic adeno-associated vector. Two experimental approaches were performed: (1) a preventive treatment where the vector was injected before the onset of the aortic aneurysm (aged 4 weeks) and followed-up for 4 and 20 weeks and (2) a palliative treatment where the vector was injected once the aneurysm was formed (8 weeks old) and followed-up for 16 weeks. We evaluated the aortic root diameter by echocardiography, the aortic wall architecture and TGFβ signaling downstream effector expression of pSMAD2 and pERK1/2 by immunohistomorphometry, and Tgfβ1 and Tgfβ2 mRNA expression levels by real-time polymerase chain reaction. Marfan syndrome mice subjected to the preventive approach showed no aortic dilation in contrast to untreated Marfan syndrome mice, which at the same end point age already presented the aneurysm. In contrast, the palliative treatment with P144 did not halt aneurysm progression. In all cases, P144 improved elastic fiber morphology and normalized pERK1/2-mediated TGFβ signaling. Unlike the palliative treatment, the preventive treatment reduced Tgfβ1 and Tgfβ2 mRNA levels.

Conclusions

P144 prevents the onset of aortic aneurysm but not its progression. Results indicate the importance of reducing the excess of active TGFβ signaling during the early stages of aortic disease progression.

Pulmonary transit of contrast during exercise is related to improved cardio-pulmonary performance in highly trained endurance athletes

BACKGROUND

The mechanisms underlying the high interindividual variability demonstrated for right-ventricular (RV) adaptation to exercise have not yet been identified, but different pulmonary vascular adaptations among individuals could be involved. Pulmonary transit of agitated saline (PTAS) during exercise has been demonstrated to be a good estimator of vascular reserve.

AIM

The aim of this study was to evaluate the presence of PTAS among endurance athletes (EAs) of both sexes and its influence on RV adaptation to exercise.

METHODS

A total of 100 highly trained EAs performed a maximal cardiopulmonary exercise test. Bi-ventricular functional and structural characteristics as well as PTAS were evaluated at baseline and at peak exercise. Athletes were distributed between two groups based on the amount of PTAS during exercise as high (HTPAS; >12 bubbles) and low (LPTAS; ≤12 bubbles).

RESULTS

Overall, 11 EAs exhibited an intra-cardiac shunt at rest and 1 met the criteria for chronic pulmonary disease and were excluded from the study. Among the remaining 88 EAs (51% women), 47 (53%) athletes were classified as HPTAS and 41 (47%) as LPTAS. HPTAS capability was associated with significantly larger RV contractile reserve, larger pulmonary vascular reserve and an enhanced maximal exercise capacity. On multivariate analysis, females were the only independent correlate of the HPTAS capability.

CONCLUSION

In highly trained endurance athletes, a HPTAS capability during exercise corresponded to an increase in pulmonary vascular and RV contractile reserves as well as an enhanced maximal exercise capacity. The long-term clinical or performance implications of the absence or presence of pulmonary shunting, and the subsequent RV afterload increase while performing exercise, remains to be determined.