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Talking about regeneration

by R Lieder & Dr O E Sigurjonsson,Science Relief Contributor
DNA double helix
Ramona Lieder and Dr Olafur E Sigurjonsson from Landspitali University Hospital’s Regenerative Medicine Laboratory (REModel) discuss current trends within tissue engineering and regenerative medicine...

The human body cannot functionally regenerate organs and tissues lost through injury or ageing. The main processes in response to tissue injury are repair mechanisms that predominantly aim at the restoration by scar tissue formation, rather than the regeneration of function and structure.

The objective of promoting the body to self-regenerate and restore normal cellular function is the basis for the interdisciplinary fields of tissue engineering and regenerative medicine. However, regeneration is by no means a spontaneous process, and approaches that aim at replicating tissue function need to provide the essential microenvironment, including cells, biomaterials or signalling molecules.

The field of tissue engineering mainly focuses on the technical aspects of regenerative medicine, especially the support and restoration of injured tissues by structural support matrices. In this aspect, natural biomaterials offer the potential for chemical modifications to meet the requirements of any particular application. Stem and progenitor cells have been considered important for tissue engineering due to their expansion properties and differentiation ability. Stem cells have the capacity to self-renew and differentiate, generating daughter cells identical to the mother cell, and/or cells with more restricted potential. Embryonic stem cells are the true stem cells although they do not persist for the lifetime of an organism while somatic stem cells have self-renewal throughout the lifetime of the animal, although their potential diminishes rapidly with age.

Implants produced from titanium and its alloys have been the gold standard in load-bearing orthopaedic applications for many years, in part due to their favourable biological and mechanical properties. Despite the obvious success, there is still room for improvement, particularly concerning the stabilisation of the implant and osseo-integration at the bone-implant interface.

Successful integration and stabilisation of the implant critically depends on the surface characteristics, including surface chemistry, roughness, topography and wettability. Osseo-integration – another factor critically determining the lifetime of the implant – describes the direct interaction of the implant with the bone tissue, ultimately favouring bone growth on the implant surface. During implantation, the contact of the implant with body fluids can result in the formation of a fibrous tissue capsule, preventing cell attachment and ultimately resulting in the loosening of the implant.

Surface characteristics and the biological microenvironment surrounding any biomaterial strongly influence the interactions with approaching cells and determine bioactivity. Surface considerations generally include not only the surface chemistry, topography and wettability, but also the influence of these material properties on polymer crystallinity, matrix protein adsorption and degradation rate. The surface characteristics critically determine the initial amount and the conformation of proteins that are adsorbed onto the biomaterial surface. This outermost layer of adhesive proteins is the primary interaction site for approaching cells and fundamentally affects integrin signalling, cell responses and regeneration processes. Even though the general parameters affecting cell responses and protein adsorption are known, the optimal surface characteristics and the detailed mechanisms at the bone-biomaterial interface are only partially understood.

Tissue engineering is growing into a large industry. It is a field that integrates expertise from engineering, materials science, chemistry, biology and medicine. What would now be welcome within clinical practice are methods to increase the biocompatibility of the implant surface and allow for an early strength development of the bone implant interface, without the risk of failure of the coatings. 

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Posted by Omkarr singh on Thursday, January 03, 2013. Filed under , , . You can follow any responses to this entry through the RSS 2.0

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