Chapter 069. Tissue Engineering (Part 1) doc

Modern tissue engineering combines the disciplines of materials sciences and life sciences to replace a diseased or damaged organ with a living, functional substitute.. The most common t

Chapter 069 Tissue Engineering

(Part 1)

Harrison's Internal Medicine > Chapter 69 Tissue Engineering

Tissue Engineering: Introduction

The origins of tissue engineering date to the sixteenth century when complex skin flaps were used to replace the nose Modern tissue engineering combines the disciplines of materials sciences and life sciences to replace a diseased or damaged organ with a living, functional substitute

The most common tissue engineering approach combines cells and matrices

to produce a living structure (Fig 69-1) These strategies also include the use of

scaffolding, cells, and growth factors to shape new tissues The term regenerative

medicine has emerged as a concept inclusive of tissue engineering and stem cell

therapy (Chap 67)

Figure 69-1

Schematic of basic principles of tissue engineering

[From Langer R, Vacanti J: Tissue engineering Science 260:1993 (Fig 1), with permission.]

Cellular Components of Tissue Engineering

The foundation of tissue engineering is the combination of a three-dimensional scaffold with live and functional cells Cells used in tissue engineering should be easily accessible and capable of proliferation while maintaining their differentiated function There are three possible sources for cells: autologous, allogenic, and xenogenic

Autologous cells are isolated directly from the patient They have the

advantage of avoiding immune-mediated rejection However, a potential limitation

is that they may not be available or able to proliferate to the required tissue mass

Allogenic cells are harvested from a donor other than the patient They have

the advantage of being more readily available, but the immune system must be modulated to avoid rejection

Xenogenic cells, or those from a different species, may also be used but

also risk immune rejection or transmission of animal pathogens

Although cells such as fibroblasts and smooth-muscle cells proliferate rapidly, other cells proliferate slowly or lose their tissue-specific function when cultured, thereby limiting their use In addition, cellular characteristics may depend on their location within the body

For example, the cell-to-cell interactions and function of endothelial cells

in the pulmonary microvasculature are different from those in the blood-brain barrier

The microenvironment of the cell, including the presence of other cell types, soluble factors, and the presence of physical or mechanical forces may also alter the function of a transplanted cell

Stem cells provide a promising cell source because they are capable of rapid proliferation and they can be induced to differentiate into multiple cell lineages (Chaps 66 and 67)

Human embryonic stem cells are capable of differentiating into endoderm, mesoderm, or ectoderm tissue types Multipotent adult stem cells have been found

in multiple mature tissues including the bone marrow, brain, heart, and liver In

addition to being able to differentiate into numerous lineages, adult stem cells generate a relatively muted immune response