Aortic valve interstitial cells: an evaluation of cell viability and cell phenotype over time

In investigating the mechanisms of aortic valve disease processes and to accurately construct tissue-engineered heart valve prostheses, a complete understanding of the native interstitial cell population is required. Previously, autopsy samples have been deemed unsuitable for immunocytochemical studies due to the ischemic time before harvesting. In this study, the viability and phenotypic profile of cells explanted from normal porcine heart valves up to 120 h post mortem was examined.

The aortic valve leaflets of porcine hearts were excised at 0, 6, 24, 48, 72, 96 and 120 h post mortem; one half of the tissue was used to explant cells, and the other half was fixed in 3.7% formalin for sectioning. Samples taken at each time point were cultured and cell viability was determined using a trypan blue exclusion assay. Immunocytochemical and immunohistochemical analyses, using specific markers for fibroblasts, myofibroblasts and smooth muscle cells, were used to compare cell phenotypes both in vitro and in situ.

Absolute numbers of cells obtained from each leaflet decreased significantly over time; however, cell viability in culture was unaffected up to 96 h. At each time point, explanted cell populations expressed similar phenotypes when compared with histological samples prepared from the same valves.

Porcine aortic valve interstitial cells may be explanted up to and including 96 h post mortem, with no statistically significant change in cell viability in vitro, and with a population that phenotypically resembles aortic valve interstitial cells in situ. These data suggest that human aortic valve interstitial cells may be successfully harvested at autopsy for in vitro studies.