**New Strategies in Heart Valve Tissue Engineering and Regenerative Medicine**

**Chapter 8**

**The Immune Response in** *In Situ* **Tissue Engineering of**

The gold standard for treatment of advanced heart valve disease is surgical heart valve re‐ placement. None of the currently available mechanical and bioprosthetic heart valve substi‐ tutes resembles normal heart valve function. While mechanical heart valves offer excellent durability, they require life-long anticoagulation to control thromboembolism, which inher‐ ently leads to an increased risk of hemorrhage complications. Bioprosthetic valves on the other hand, retain a more physiological blood flow pattern, but these valves are prone to calcifica‐ tion and structural deterioration, limiting their lifespan. For both types of replacement valves, the main limitation is that they are non-living prostheses, incapable of adapting to changes in the hemodynamic environment. It was shown that a living autograft implanted in the aortic position (the Ross procedure) improves long-term clinical outcome compared to a non-living homograft [1]. This illustrates the importance of the regulatory and adaptive properties of a living valve substitute. Tissue engineered aortic valves can provide such an autologous, viable valve with the potential to grow, adapt, and regenerate within the hemodynamic environ‐ ment. Evidently, the pediatric and young adult population would benefit most from such a tis‐ sue engineered aortic valve. The valve's ability to grow as the recipient grows and matures,

Foundational principle of regenerative medicine is restoring the native tissue structure and function by providing a microenvironment necessary to promote tissue regeneration. Tissue engineering scaffolds are biomaterials designed to create this microenvironment and to pro‐ mote tissue regeneration [8]. The traditional tissue engineering paradigm for creating trileaflet heart valves consists of harvesting autologous cells from the patient, expanding the cells *in vi‐ tro,* and subsequently seeding the cells into a biodegradable scaffold. The cell-scaffold con‐ structs are conditioned in a bioreactor to promote extracellular matrix formation (ECM), while

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© 2013 van Loon et al.; licensee InTech. This is an open access article distributed under the terms of the Creative Commons Attribution License (http://creativecommons.org/licenses/by/3.0), which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited.

© 2013 The Author(s). Licensee InTech. This chapter is distributed under the terms of the Creative Commons Attribution License http://creativecommons.org/licenses/by/3.0), which permits unrestricted use, distribution,

**Aortic Heart Valves**

http://dx.doi.org/10.5772/54354

**1. Introduction**

F. P. T. Baaijens and C. V. C. Bouten

S. L. M. van Loon, A. I. P. M. Smits, A. Driessen-Mol,

Additional information is available at the end of the chapter

eliminates the need for repetitive surgeries. [2-7].
