Page 99 - Tailoring Electrospinning Techniques for Regenerative Medicine - Marc Simonet

5.2 Introduction
Most human tissues have a limited regeneration potential. In the case of tissue damage, the recovery of tissue structure and function is o en incomplete, usually leading to scar tissue. For fully di erentiated, load-bearing cardiovascular tissues, such as heart valves, regeneration is unlikely and replacement is a frequently applied therapy. Tissue engineering solutions are intensively studied for this purpose, mainly because of the option to create a living tissue replacement that can grow and remodel in response to changing environmental conditions. Key research questions in the area of heart valve tissue engineering are: ‘Can we create a functional valve equivalent with appropriate tissue structure and mechanical properties?’ and ‘Can we control tissue formation and organization by designing sca olds and culture conditions that favor these processes?’.
With recent advances in developmental and (stem) cell biology, tissue engineering is becoming increasingly oriented towards designing biologically inspired cellular microenvironments, aimed to guide cell growth, di erentiation and functional tissue organization. The premise is that in order to unlock the full potential of the cells, at least some aspects of the three-dimensional (3D) tissue environment associated with their renewal, di erentiation and organization needs to be mimicked in the applied sca old materials. The selection of the material,
as well as the processing of the material into a 3D structure, therefore becomes increasingly important to achieve both microscopic and macroscopic relevant material properties that favor tissue development and ultimate valve functioning.
In this chapter we discuss the target tissue to be replaced with engineered heart valve equivalents, the specific tissue requirements that may dictate macroscopic and microscopic sca old properties for this purpose, and the di erent electrospinning settings and modalities that can be applied to meet these requirements.
5.3 Tissue to be replaced – heart 5 valves
The human heart contains four heart valves, acting as one-way doors to guide blood flow into the proper direction in both the systemic and the pulmonary circulation. The atrioventricular valves (tricuspid and mitral valve) prevent backflow of blood from the ventricles to the atria, while the semilunar valves (pulmonary and aortic valve) prevent backflow from the arteries into the ventricles during diastole. All valves are believed to function in a passive pressure- driven manner. They open when pressure gradients force the blood forwards and close when backward pressure gradients push the blood backwards.
ELECTROSPINNING FOR HEART VALVE TISSUE REGENERATION
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