Page 123 - Tailoring Electrospinning Techniques for Regenerative Medicine - Marc Simonet

6.2 Introduction
Heart valve disease is a major health problem causing significant morbidity and mortality worldwide. To treat the rising numbers of patients, mechanical and biological prostheses remain the gra s of choice. Although heart valve replacement generally results in enhanced survival and quality of life, these prostheses have serious drawbacks that limit their long-term e icacy.1 Bioprosthetic valves have a limited durability due to tissue degeneration and calcification and the quantity of allogra is limited. While mechanical valves can last for a life time and are readily available, they required life-long anti- coagulation therapy.2,3 In-situ tissue engineering aims at the development of a clinically and economically attractive new generation of heart valve prostheses, who are available o -the-shelf and aid to overcome the limitations of currently used prostheses.4,5
In-situ tissue-engineered heart valves are formed in-vivo. An implanted bare sca old has to function as a valve directly a er implantation accompanied by carrying the hemodynamic loading. Meanwhile, the implanted sca old is supposed to act as a template for circulating cells to adhere, di erentiate, and subsequently form neo-tissue. A er neo-tissue is formed, the sca old degrades and a heart valve originated from native host cells remains. For in-situ tissue engineering of heart valves, optimization of sca old materials is required with respect to their
mechanical properties, their ability to guide tissue regeneration in combination with their degradation rate. All these properties are tunable when selecting a synthetic polymer as basic material.6
Electrospinning is reported to be one of the
most promising methods to produce sca olds for
in-situ tissue engineering.7–9 Electrospinning o ers
a broad freedom in sca old design with respect
to material choice, fiber diameter, fiber alignment
and porosities, all influencing e.g. mechanical and
degradation properties of the sca old.10,11 Attractive
features of electrospinning are the possibility to
directly fabricate three-dimensional structures like
heart valves12–14 and the ability to add bioactive cues
such as peptides and proteins, e.g. growth factors.15
With electrospinning, tailor-made sca olds suitable
for in-situ tissue engineering of heart valves can be
designed. 6
In this study, we compared the feasibility and suitability of two electrospun PCL-based sca olds for in-situ tissue engineering of heart valves. Pure PCL was selected because of its wide use in tissue engineering research16 and because studies with electrospun PCL heart valve sca olds have already been reported.14,17 The second material tested was PCL-bisurea (PCL2kU4Un) a PCL based elastomeric polymer. It’s supramolecular chemistry involving its U4U-groups allows tuning of the mechanical
FROM A POLYMER TOWARDS AN IN-SITU TISSUE ENGINEERED HEART VALVE
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