Simvastatin does not diminish the in vivo degeneration of decellularized aortic conduits.

BACKGROUND: All present biological cardiovascular prostheses are prone to progressive in vivo degeneration, which can be partially impaired by decellularization. The administration of statins may provide an additional beneficial effect. We provide the first in vivo data on the effect of statins on decellularized cardiovascular implants. METHODS: Wistar rats with aortic valve insufficiency (day 14) were fed either with a pro-calcific diet (group C; n = 17), or the same diet additionally supplemented with simvastatin (group S; n = 16). Aortic conduits from Sprague-Dawley rats were detergent-decellularized, infrarenally implanted (day 0) in all recipients and explanted at day 28 or day 84. RESULTS: Sonographic competence of the conduit perfusion was 100%, and overall survival amounted to 97%. Simvastatin decreased the low-density lipoprotein cholesterol serum levels; however, it did not affect the calcification of the implants. Histology revealed alpha-smooth muscle actin-positive intima hyperplasia in both groups. Extensive matrix metalloproteinase activity was observed in calcified areas, especially in group S. Quantitative RNA analysis resulted in no differences with regard to several markers of calcifying degeneration (alkaline phosphatase, osteopontin, osteocalcin, osteoprotegerin, bone morphogenetic protein-2, runt-related transcription factor-2) and inflammation (tumor necrosis factor α, interleukin 1ß, receptor for advanced glycation end products, CD39, CD73), but significantly lower levels of interleukin-6 in group S. CONCLUSIONS: In a standardized small animal model of accelerated cardiovascular calcification, simvastatin failed to diminish the calcification of decellularized aortic conduit implants. This finding confirms the observations of recent clinical trials. However, further experiments are warranted to elucidate the value of partial benefits associated with lower circulating lipid and proinflammatory cytokine levels.

The degeneration of biological cardiovascular prostheses under pro-calcific metabolic conditions in a small animal model.

In order to allow for a comparative evaluation of the in vivo degeneration of biological and tissue-engineered heart valves and vascular grafts, a small animal model of accelerated cardiovascular calcification is desired. Wistar rats (n = 102; 6 groups) were fed ad libitum with regular chow and 5 different regimens of pro-calcific diet supplemented with combinations of vitamin D (VD), cholesterol (CH) and dicalcium phosphate (PH). Moreover, cryopreserved (n = 7) or detergent-decellularized rat aortic conduit grafts (n = 6) were infrarenally implanted in Wistar rats under severely pro-calcific conditions. The follow-up lasted up to 12 weeks. High-dose application of VD (300,000 IU/kg), CH (2%) and PH (1.5%) resulted in elevated serum calcium and cholesterol levels as well as LDL/HDL ratio. It increased the tissue MMP activity visualized by in situ zymography and caused significantly aggravated calcification of the native aortic valve as well as the aortic wall as assessed by histology and micro-computed tomography. (Immuno)histology and quantitative real-time PCR revealed chondro-osteogenic cell transformation, lipid deposition, nitrosative stress and low-level inflammation to be involved in the formation of calcific lesions. Despite pro-calcific in vivo conditions, decellularization significantly reduced calcification, inflammation and intimal hyperplasia in aortic conduit implants. A well balanced dietary trigger for pathologic metabolic conditions may represent an appropriate mid-term treatment to induce calcifying degeneration of aortic valves as well as vascular structures in the systemic circulation in rats. With respect to experimental investigation focusing on calcifying degeneration of native or prosthetic tissue, this regimen may serve as a valuable tool with a rapid onset and multi-facetted character of cardiovascular degeneration.