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Impact Of Calpain-9 On Intimal Hyperplasia In Human Pulmonary Vein Stenosis
Takahiro Inoue1,2, Hiroshi Matsushita1,2, Enoch Yeung1, James Beckett1, John Coulson1, Harry Dietz1, Narutoshi Hibino1,2,3.
1Johns Hopkins Medicine, Baltimore, MD, 2The University of Chicago,Chicago, IL. 3Advocate Children's Hospital, Chicago, IL

Objective(s): Severe progressive pulmonary vein (PV) stenosis remains very difficult to manage with limited treatments. Several growth factors, including VEGF, PDGF and TGF-β1, are involved in PV stenosis. However, increased knowledge of the downstream signaling cascades is needed to develop effective clinical interventions. Calpain provides an interesting candidate therapeutic target, since it is activated by EGF, PDGF and TGF-β1. We have also discovered that calpain-9 is associated with cell proliferation and fibrosis. In this study, we examined the role of calpain-9 in PV stenosis.
Methods: Non-stenosis (Ns-PV) and stenosis PV with vascular stents (S-PV) were harvested from a patient with congenital PV stenosis. H&E, Masson-Trichrome and calpain-9 staining were performed to measure intimal thickness and the number of calpain-9 positive cells. Furthermore, we examined the role of calpain-9 in neointimal hyperplasia using a mouse wire injury model.
Results: Intimal thickness of human PV was significantly greater in S-PV than Ns-PV (470.0±123.6 vs 128.8±40.2µm, P<0.01). The number of calpain-9 positive cells tended to be higher in S-PV than Ns-PV (16.6±6.2 vs 13.7±4.5/HPF, P=0.09). In a mouse model, the number of calpain-9 positive cells were significantly higher in wire injure group with significant intimal hyperplasia formation compared to the control group (45.9±10.9 vs 16.7±5.9/intima, P<0.01).
Conclusions: Calpain-9 is likely to be associated with intimal hyperplasia in human PV stenosis. Further study using a mouse wire injury model will be able to identify the detail effect of calpain-9 on intimal hyperplasia, which could develop a new target for the treatment of PV stenosis.