Page 17 - Tailoring Electrospinning Techniques for Regenerative Medicine - Marc Simonet

Tissue engineering is a multidisciplinary field at the cross section of biology, medicine and engineering, aiming to develop functional substitutes for damaged tissues and organs. In 1988 it was define as: “The application of principles and methods of engineering and life science toward fundamental understanding of structure-function relationships in normal and pathological function”.1 Later, Langer and Vacanti further improved the definition to: “Tissue engineering is an interdisciplinary field that applies the principles of engineering and the life sciences towards the development of biological substitutes that restore, maintain, or improve tissue function.”2 This field emerged as one possible option to overcome the shortage of available organ transplants. Tissue engineering approaches are generally based on stimulating tissue formation using cells in combination with a biodegradable sca old that provides initial support and structure to the cells until they have produced their own extracellular matrix (ECM).
In its classical form tissue engineering relies on harvesting the patient’s own cells, expanding and culturing them on sca olds with targeted three- dimensional (3D) geometries outside the patient’s body (in-vitro) followed by implantation. Prior to implantation, cell-sca old constructs are usually placed in a bioreactor, where they are triggered to produce extracellular matrix until the tissue construct is mature enough to be implanted (Figure 1.1a).
A newer and more cost e ective approach, relying 1 on the patient’s natural regeneration potential, is in-situ
tissue engineering (Figure 1.1b). A 3D biodegradable
sca old, available o -the-shelf, is implanted at the
site of destination, where it gradually transforms into a neo-tissue by recruiting endogenous cells and using the patient’s body as the bioreactor. This approach poses high demands on sca old properties and development. The sca old has to be fully functional at the time of implantation, while supporting and guiding the production of a safe and functional living tissue replacement inside the patient’s own body.
For both of these approaches, the sca old represents the basis to engineer a living tissue replacement by providing mechanical and structural support and to guide the development of a well- organized and functional ECM. A current paradigm in tissue engineering is that this sca old should mimic and function as the ECM of the targeted tissue to fully unlock the potential of tissue engineering.
ECM is the nanocomposite microenvironment surrounding the cells. It largely consists of interweaved fibers of collagen, the main load bearing component, and elastin fibers, providing elasticity to the network. These fibers, with diameters ranging from a few nanometers to a few hundred nanometers, are covered with laminin and fibronectin to o er specific cell binding sites, all embedded in a gel of polysaccharides. In addition to providing the structure and shape of tissues, the ECM also regulates cellular
GENERAL INTRODUCTION
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