Heart valve engineering: decellularized aortic homograft seeded with human cardiac stromal cells

The adult human heart contains a cardiac mesenchymal stromal cell (CStC) population with residual cardiovascular plasticity. The study aim was to investigate the ability of CStCs to populate decellularized aortic homograft leaflets, without mechanical stimulation.

The ability of CStCs to acquire valve endothelial and interstitial cell phenotypes was tested using in vitro assays. First, trypsin-decellularized aortic leaflets were seeded with CStCs under static conditions; tissue section analyses were then performed before and after decellularization, and at 10, 20, and 30 days after reseeding.

Following in vitro treatment, the CStCs differentiated along the endothelial lineage, as shown by their capacity to uptake acetylated low-density lipoprotein and to secrete the pro-angiogenic factor, vascular endothelial growth factor. After seeding, CStCs were able to adhere to the leaflet surface, rescuing up to the 90% of the original cell density and expressing the mature endothelial marker, von Willebrandt factor. The CStC supernatants were also positive for matrix metalloprotease-2 (MMP-2), which confirmed the ability of these cells to penetrate within the leaflet structure; this also suggested that CStCs, once engrafted, would contribute to the extracellular matrix turnover. Accordingly, although at a lower efficiency, CStC repopulation was also evident in the inner portions of the leaflet.

Seeded CStCs were able to reconstitute, without mechanical stimulation, an endothelial-like layer and to partially infiltrate decellularized homograft leaflets. Hence, CStCs appear to be a potentially useful cell type for engineered heart valves.