Histological and morphometric analyses of mouse heart valve aorta structure

AIM: To provide standard morphometric data of normal mouse aorta valve structure for the evaluation of transgenic mouse models of aortic valve diseases. METHODS: Adult mouse (postnatal 3 months) hearts were harvested and histological and valve morphometric analyses of valve cell population, distribution and collagen content as well as valve microstructure were conducted by light microscope (HE stain, immunofluorescence, Laser scanning confocal microscope and Masson’s trichrome stain) and transmission electron microscope. RESULTS: The aortic valve area of normal mice was (0.1978±0.003) mm2 with a perimeter of (9.18±0.06)×102 μm, average cell number (9.75±0.04)×102/mm2, endothelial cell number (3.23±0.10)×102/mm2, intersititial cell number (5.05±0.07)×102/mm2, and collagen content (21.62±9.33)%. Confocal laser scanning displayed some co-expressed CD31 and α-SMA cells under endothelium, indicating the existence of epidermal-mesenchymal transformation potential cells in adult aortic valves. Electron microscopy showed some morphological differences between the ventricular face of the valve and the aortic face of the valve endothelium. The ventricular face of the valve endothelium was flat, whereas the aortic face of the valve endothelium was square. Interstitial fibroblasts were in a quiescent state in which the cell bodies were short and long spindle-shaped, and endoplasmic reticulum and Golgi complexes were undeveloped. Extracellular matrix was collagen-rich, which was mainly concentrated in the outflow tract. CONCLUSION: Histological and morphometric data are provided for normal mouse aortic valve structure and are useful as reference standards for future studies of mouse models of progressive aortic valve diseases.