New calcification model for intact murine aortic valves

Abstract

Calcific aortic valve disease (CAVD) is a common progressive disease of the aortic valves, for which no medical treatment exists and surgery represents currently the only therapeutic solution. The development of novel pharmacological treatments for CAVD has been hampered by the lack of suitable test-systems, which require the preservation of the complex valve structure in a mechanically and biochemical controllable system. Therefore, we aimed at establishing a model which allows the study of calcification in intact mouse aortic valves by using the Miniature Tissue Culture System (MTCS), an ex vivo flow model for whole mouse hearts. Aortic valves of wild-type mice were cultured in the MTCS and exposed to osteogenic medium (OSM, containing ascorbic acid, β-glycerophosphate and dexamethasone) or inorganic phosphates (PI). Osteogenic calcification occurred in the aortic valve leaflets that were cultured ex vivo in the presence of PI, but not of OSM. In vitro cultured mouse and human valvular interstitial cells calcified in both OSM and PI conditions, revealing in vitro-ex vivo differences. Furthermore, endochondral differentiation occurred in the aortic root of ex vivo cultured mouse hearts near the hinge of the aortic valve in both PI and OSM conditions. Dexamethasone was found to induce endochondral differentiation in the aortic root, but to inhibit calcification and the expression of osteogenic markers in the aortic leaflet, partly explaining the absence of calcification in the aortic valve cultured with OSM. The osteogenic calcifications in the aortic leaflet and the endochondral differentiation in the aortic root resemble calcifications found in human CAVD. In conclusion, we have established an ex vivo calcification model for intact wild-type murine aortic valves in which the initiation and progression of aortic valve calcification can be studied. The in vitro-ex vivo differences found in our studies underline the importance of ex vivo models to facilitate pre-clinical translational studies.

S2 Heart Sound Detects Aortic Valve Calcification Independent of Hemodynamic Changes in Mice

“…Other transgenic mouse models with diet-induced CAVD have shown similar results, with only a percentage of mice developing calcific plaque over the course of 6–20 months ( 41 , 42 ). Commonly, calcification in mouse AoV leaflets is quantified by imaging AoV cross-sections and comparing the intensity of a calcium tracer to the AoV area ( 43 – 45 ). It is difficult to quantify total AoV calcification since the AoV area needs to be manually selected for each cross-section.…”

Organ Culture Model of Aortic Valve Calcification

“…The use of intact valve leaflets has the advantage that the VIC are retained in the physiological arrangement with respect to their association with the extracellular matrix and their relationship with the VEC. Intact valve leaflets from pigs and mice have previously been used to assess the effects of pro-calcific stimuli, including inorganic phosphate osteogenic media, osteogenic media supplemented with TGFβ1 and mechanical injury (11,12,(21)(22)(23)(24). These previous studies have largely relied upon osteogenic media, which contains β-glycerophosphate, dexamethasone, and ascorbic acid, to drive the calcification response.…”