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DOI: 10.1055/s-0031-1297434
The influence of the cell source on the sufficiency of tissue engineered heart valves
Objective: To find the optimal cell source for autologous tissue engineered heart valves (TEHV) different cells have been evaluated in terms of proliferation, phenotype and synthetic activity, yet a major drawback of TEHV is the cell mediated tissue contraction which results in the shortening of the leaflets and thus in insufficient valves.
Our aim was to evaluate the influence of the cell source on tissue contraction in TEHV. Cells from ovine carotid artery (OCA), ovine umbilical artery (OUA) and human umbilical artery (HUA) were compared for phenotype and contraction of fibrin gels. To directly correlate cell contractility and valve sufficiency, TEHV made with OCA and OUA cells were compared on tissue contraction.
Methods: Cell phenotype was characterized by immunostaining of alpha-smooth muscle actin (αSMA).
For the contraction assay, fibrin gels with a cell concentration of 5·106/ml were moulded in a 24 well plate (n≥3) and their shrinkage was evaluated over 13 days by measuring the gels area in relation to the original area.
Fibrin based TEHV were moulded using OCA and OUA cells (10·106/ml). They were conditioned statically for 14 days in the closed leaflet configuration and successively dynamically in the open leaflet configuration in bioreactors for 30 days.
Results: OCA cells exhibited a highly contractile myofibroblast phenotype (high αSMA expression), in HUA cells a limited subpopulation expressed αSMA while OUA cells were mostly non-contractile fibroblasts with only few cells expressing αSMA.
After 13 days OCA gels were contracted to 23±1.1% of the original size. HUA gels shrank to 27.8±0.1% and OUA gels reached a size of 81.4±7.0%.
Hydroxyproline content was 1.00±0.34µg/mg (OCA), 0.81±0.27µg/mg (HUA) and 0.50±0.12µg/mg (OUA) of the initial area.
The leaflets of TEHV with OCA cells contracted and at the end of the conditioning protocol the valves were insufficient. Valves made with OUA cells showed no signs of contraction and were sufficient.
Conclusion: As shown by the contraction assay the cell source strongly influences cell-mediated tissue contraction and thus the sufficiency of TEHV. We were able to produce completely sufficient TEHV after in vitro conditioning by using non-contractile OUA cells. Further evaluation will include immunohistology and determination of collagen content.
The sufficient valves were implanted in lambs and are currently being evaluated in vivo for growth capability and hemodynamic performance.