Introduction Marfan syndrome (MFS) is a rare genetic disorder caused by mutations in the fibrillin-1 gene. Aortic root dilatation and dissection is the main cause of morbidity and mortality in patients diagnosed with MFS. Imbalanced expression of matrix metalloproteases (MMPs) and their endogenous inhibitors (TIMPs) has been shown to play a critical role in extracellular matrix degradation and aortic wall instability in MFS. Therefore, the aim of our study is to establish a novel gene therapy approach for MFS by targeted overexpression of TIMP-1 in the aorta within a murine model of the disease.
Methods We utilized eight-week-old female Marfan mice (mgR/mgR, five mice per group). The mice were injected with adeno-associated virus (AAV)-9 vectors harboring the TIMP-1 cDNA or an EGFP reporter gene as control. Prior to injection, the AAVs were incubated with an endothelial-affine peptide, SLR, to ensure specificity for endothelial cells. After four weeks, aortic size was assessed by echocardiography. The degree of elastin degradation was analysed by Elastin van Giesson staining. To evaluate gelatinase activity, aortic sections were subjected to in situ zymography. In addition, the expression of tight junction proteins (ZO-1, occluding) was analysed by immunohistochemistry.
Results Aortic diameters were significantly reduced in mice injected with AAV-TIMP-1 as compared to controls. Importantly, AAV-TIMP-1 treatment led to normalization of gelatinase activity as well as a dramatic decrease in the number of elastin breaks within the aortic wall. Furthermore, overexpression of TIMP-1 led to increased expression of endothelial tight junction proteins.
Conclusion Overexpression of TIMP-1 in the aortic tissue of Marfan mice leads to increased aortic stability, improved elastin architecture, and decreased vascular permeability. Hence, this approach offers the potential to be further translated into a novel therapeutic approach for MFS.
