Section 4 Plastic and Reconstructive Problems

L. Ribeiro et al.

Resultados y conclusiones:

Hay posibilidades muy interesantes para futuros tratamientos en

otorrinolaringología que aplican los conceptos de la ingeniería de tejidos.

Introduction

In the current era the paradigm of medicine is constantly

changing, as new concepts and methods of life support

and disease control arise. Tissue engineering is becoming

one of the most promising weapons in medical practice.

Based on highly advanced technological procedures, tis-

sue and organ reconstruction may, within a short time,

become gold-standard treatments for a rising number of

medical conditions where classical pharmacological or surgi-

cal interventions have limited effectiveness. In fact, recent

developments in the area clearly show impressive results in

the rehabilitation of functionally or structurally committed

organs and tissues.

Otorhinolaryngology (ORL), as a medical specialty with a

wide range of medical and surgical interventions, naturally

assumes a position of leadership in the application of tissue

engineering techniques.

The aim of this review is the description of the fundamen-

tals of regenerative medicine and its potential applications

in ORL.

Fundamentals

The main goal of tissue engineering is restoring functional or

structural tissue by using living elements that will later be

integrated in patients.

In this process, 3 basic components

are generally present: cells, regulators/growth factors and

scaffolds, which may or may not be used simultaneously.

2,3

Cells

Most papers published within the past 20 years have focused

mainly on cell therapy,

which consists in the deposit of

selected living cells in an appropriate scaffold, that, when

exposed to a specific microenvironment, will multiply and

differentiate into the desired structure. Different cell sub-

types may be used: stem cells and adult cells.

1--3

Stem cells are characterized not only by their ability of

continuous and unlimited self-renewal, but also by the pos-

sibility of differentiation into any cellular phenotype.

Stem

cells are assumed as having the highest potential in regen-

erative medicine, although their use is limited by ethical

issues and the potential risk of neoplastic transformation.

Stem cells can be obtained from embryonic or mature tis-

sues. Embryonic stem cells are derived from blastocysts, and

therefore can differentiate into any mature cell type of the

3 germ layers.

On the other hand, adult stem cells can be

collected from certain niches in the body, namely bone mar-

row, adipose tissue or blood,

and are not totally pluripotent

as they are positioned in a later stage of the differentiation

line, having a finite capacity to multiply depending on the

origin of the tissue.

Adult cells can be obtained from a biopsy specimen of

the tissue to be regenerated, and their replication is induced

in vitro

before transplantation. Being phylogenetically more

advanced, adult cells do not have the ability to replicate

endlessly or to transform into different cell types. These

features, combined with the possibility of perpetuation of

pre-existing pathological changes in the donor organ or tis-

sue, represent important limitations in their use.

Regulators/Growth Factors

Growth factors are molecules that regulate proliferation,

differentiation and cell function, and therefore may induce,

accelerate or inhibit those cellular processes. They are an

essential element in regenerative medicine. Depending on

the technique used, these molecules can be included in

a scaffold, which serves as a means for their controlled

release, which will influence and control cell growth.

Scaffolds

Scaffolds are porous 3-dimensional structures that provide

mechanical support and physical protection to cells and

growth factors.

These should be composed of a biocom-

patible and reabsorbable matrix,

1,2,5

allowing for complete

tissue regeneration. Collagen and fibrin are among the most

commonly used materials, and are generally obtained from

natural sources; polyglycolic acid, a synthetic polymer, may

also be used.

Applications of Tissue Engineering

in Otorhinolaryngology

Laryngology

The vocal folds are able to vibrate at a frequency up to

1000 Hz

, due to their microstructure consisting of epithe-

lium, lamina propria and the vocal muscle. The lamina

propria is composed by a superficial layer (Reinke space), an

intermediate layer and a deeper layer, each of these having

specific cellular components, which are ultimately related

to the organ function.

The stratified epithelium covers the entire surface of the

vocal folds, and represents a barrier against physical, chemi-