Cartilage in the aortic valve and its relationship with the aortic valve morphology in Syrian hamsters

We conducted a light-microscopic histologic study of the aortic valves of 224 Syrian hamsters aged between 1 and 771 days. Most of the hamsters examined belonged to a single laboratory-inbred family with a high incidence of bicuspid aortic valves (BAVs). In 146 specimens the aortic valve was tricuspid, and in 107 of them the ventral commissure was more or less fused. The remaining 78 specimens showed a BAV with the aortic sinuses oriented ventrodorsally. In 33 BAVs a raphe was located in the ventral aortic sinus. Cartilaginous foci were present in the aortic valves of 86 specimens, 40-771 days old. The foci were located at two different sites, namely in the ventral wall of the valve and/or in the dorsal aortic sinus. Statistical analyses substantiate that (1) chondrogenesis begins earlier in BAVs, and especially in those having a raphe, than in tricuspid aortic valves and (2) the location of the cartilaginous foci is significantly associated with the morphology of the aortic valve. The present findings support the hypothesis that, in the Syrian hamster, cartilage forms in the aortic valve as a response to locally intense mechanical stimulation.