The Role of Matricellular Proteins Nov and Wisp1 In Aging and Myocardial Infarction

Abstract

Background. The Cysteine-rich protein, Connective tissue growth factor, and Nephroblastoma overexpressed protein (CCN) family of matricellular proteins are signaling molecules found in the extracellular space, which can have pro-angiogenic, anti-inflammatory and anti-fibrotic properties. Their expression and role in repair and remodeling after myocardial infarction (MI) remains to be better elucidated. In this study, the age-associated expression of Nov (CCN3) and Wisp1 (CCN4) were examined post-MI in mice. Methods and Results. In vivo, MI was induced in young (6 week) and old (12-14 months) mice. Cardiac function was assessed by echocardiography, showing that LVEF was reduced in old mice (33.9%) at 14 days post-MI compared to young mice (43.9%; p=0.002). RT-qPCR analysis of harvested myocardial tissue revealed that mRNA expression of several matricellular proteins in healthy tissue was decreased by 2.5- to 5-fold in old compared to young mice (p=0.03 for Nov, p=0.04 for Wisp1, p=0.0002 for TnC, p=0.04 for TSP-1). Post-MI, mRNA expression of Nov was reduced in the infarct (by up to 13-fold; p<0.03) and border zone (by up to 16-fold; p<0.002) in old compared to young mice. Nov and Wisp1 protein expression was also reduced in old compared to young mice in the infarct and border zones; specifically, for Nov in the infarct zone (p=0.01) and the border zone (p=0.009) at 2 days post-MI and for Wisp1 in the infarct zone at 2 days (p=0.0003) and 14 days (p=0.003), along with 7 days post-MI in the border zone (p=0.0003). To identify possible sources of matricellular proteins, in vitro culture experiments were performed. The expression of Nov protein was increased (1.9-fold; p=0.006) in TGF-B stimulated cardiac fibroblasts after 48h, as was the expression of the myofibroblast marker a-SMA (1.7-fold; p=0.035). Wisp1 mRNA expression was increased (4.5-fold; p=0.03) in stimulated cardiac fibroblasts after 48h in a hypoxic environment. There was also a trend for increased mRNA expression of Nov (p=0.118) and Wisp1 (p=0.121) in M2 macrophages. Cardiac fibroblasts treated with Nov+TGF-B exhibited greater proliferation (by 29%; p0.01), as did those treated with Wisp1+TGF-B (by 16%; p<0.05). Treatment with Nov or Wisp1 led to an increase in viability of cardiac fibroblasts both in the presence (Nov; p=0.0004, Wisp1; p=0.01) and absence of TGF-B (Nov; p=0.0005, Wisp1; p=0.003). Summary. There is an age-associated difference in the expression of matricellular proteins Nov and Wisp1 between both healthy and MI mice. In vitro studies suggest that cardiac fibroblasts may produce Nov and Wisp1 upon their activation to myofibroblasts. The presence of these proteins was also shown to increase the proliferation and viability of fibroblasts. Therefore, reduced levels of Nov and Wisp1 in old mice may negatively affect the repair and remodeling process post-MI compared to young mice. A better understanding of Nov and Wisp1 function in aging and post-MI repair may help identify novel therapeutic targets for limiting damage post-MI and improving repair and heart function.