Porcine cardiac valvular subendothelial cells in culture: cell isolation and growth characteristics.

We established culture lines derived from the subendothelial region of the porcine aortic valve. These cells were isolated by extensive collagenase digestion of valvular tissue and were serially propagated with stable morphology. In sparse culture, valve subendothelial cells resembled skin fibroblasts. When confluent, the valve subendothelial cells formed ridges and piles similar to vascular smooth muscle cells. Endogenous in vitro labeling experiments using 35S-methionine showed that valve subendothelial cells synthesized and released several proteins not observed in parallel experiments using porcine skin fibroblasts and smooth muscle cells. Mitogen assays using media conditioned by porcine aortic valvular endothelial cells showed that the valve subendothelial cells, when compared to skin fibroblasts and smooth muscle cells, were particularly avid responders to the growth factors released by valve endothelial cells in vitro. The valve subendothelial cells also released 10-fold more prostacyclin in response to arachidonate than did skin fibroblasts or smooth muscle cells. We conclude that valve subendothelial cells show features that distinguish them from other cultured mesenchymal cells, and that this culture system will be useful for studies of the cellular basis of valvular heart disease.