Targeting mitochondrial stress with SS31 reduces ascending aortic dilation and improves cardiac performance in a preclinical model of Marfan disease

Abstract Background and purpose Aortic dissection or rupture is the most devastating complication of aneurysms in the thoracic ascending aorta (TAA) of patients diagnosed with Marfan or Loeys-Dietz syndrome leading to death in 80-90% of patients. Reparative surgery is the only effective strategy and for this reason, we aim to determine new therapeutic strategies. Since mitochondrial dysfunction contribute to the pathophysiology of aortic aneurysm we aim to study the therapeutic effectiveness of the reduction of mitochondrial stress to limit development and progression of aortic aneurysms in Fbn1C1041G/+ mice during aging. Methods a transcriptomic analysis was performed by RNA sequencing using RNA isolated of ATAA tissue from patients diagnosed with a syndrome or with bicuspid aortic valve (BAV) and from the ascending aorta of multi-organ healthy donors. Differentially expressed genes (DEGs) related to mitochondrial dysfunction were identified with the DESeq2 package. Enriched pathway (Reactome) and protein interaction (PPI) analysis was performed with the clusterProfiles package. For the in vivo studies, the mitochondria-targeted tetrapeptide SS31 or the inactive peptide SS20 were administered to 4-months-old Fbn1C1041G/+ males and females at a dose of 3 mg/kg/day in the water intake during 3 months. The dilation of ascending aorta and aortic root and the cardiac function were monthly monitored by ultrasonography using the VEVO 3100 and the oxygen consumption rate (OCR) was measured in tissue explants of murine ascending aorta and heart to evaluate mitochondrial function. Briefly, punches of 2 mm diameter were obtained from fresh ascending aortic wall and from heart slices of 150 µm size and were placed into the wells of XF24 Islet Capture Microplates and OCR levels were analyzed in Seahorse XFe24 equipment. Results alterations in the expression of genes that encode proteins forming part of the mitochondrial respiratory chain and ATP synthase (MT-CO3, MT-CO2, MT-CYB, MT-ND1, MT-ND2, MT-ATP8 and MT-ATP6) were detected in syndromic patients but no in BAV patients. In the murine model of Marfan disease, the administration of SS31 reduced the dilation of ascending thoracic aorta and aortic root in males and females during aging whereas no differences in the body weight or water intake were registered between mice treated with SS20 and SS31. Analysis of the spare respiratory capacity of Marfan mice aorta and heart punches treated with SS31 improved significantly when compared to Marfan mice treated with SS20. Interestingly, a better cardiac performance was observed in those marfan males treated with SS31 vs. SS20 but no differences were reported between both groups of females. Conclusions our data show that mitochondrial dysfunction might have an important role in the aneurysm development of Marfan patients and in a murine model of this disease. Therefore, targeting mitochondrial stress is a promising therapeutic strategy for the treatment of ATAA.