| HOME | HELP | FEEDBACK | SUBSCRIPTIONS | ARCHIVE | SEARCH | TABLE OF CONTENTS |
|
|
|
|||||||
|
|||||||||
J Thorac Cardiovasc Surg 2005;129:470-472
© 2005 The American Association for Thoracic Surgery
Brief Communications |
a Department of Cardiothoracic Surgery, Southampton General Hospital, Southampton, United Kingdom
b Department of Bioengineering, Clemson University, Clemson, SC
Received for publication June 4, 2004; accepted for publication June 17, 2004. * Address for reprints: Thomas Boland, PhD, 502 Rhodes, Clemson, SC 29634 (E-mail: tboland{at}CLEMSON.EDU).
Tissue engineering may be defined as the science and engineering of functional tissues and organs for the replacement of diseased body parts.1 Traditionally, this has been done by the seeding of cellular material onto a suitable scaffold material to create 3-dimensional constructs.2 However there are a number of drawbacks to this technique. The degree of cellular penetration is variable and does not proceed uniformly through the scaffold. Organs consist of varied cell types in specific locations, and this is hard to replicate with this technique. Preformed, rigid scaffolds are not suitable for engineering contractile tissues, such as myocardium or vascular conduits. Perhaps the single most limiting factor with solid scaffold design is that of providing the developing structure with a vascular supply. Many of the top-down fabrication techniques that have been developed relate to the manufacture of microelectromechanical devices and are therefore unsuitable for biologic systems. It is therefore necessary to develop other strategies for assembling tissuelike constructs, a strategy that allows the creation of structures with distinct shapes and functions that are nurtured by vascular connectivity incorporating methods of vascularizing large, living, 3-dimensional tissue-engineered constructs.
Adapting bottom-up approaches to tissue engineering is a genuine challenge. Since the first application of fused deposition modeling for tissue engineering scaffolds,3 considerable effort has been focused on printing synthetic biodegradable scaffolds.4 Concurrently, a variety of rapid prototyping techniques have been developed to define macroscopically the shapes of deposited biomaterials, including photolithography,5 syringe-based gel deposition,6 and solid freeform fabrication.7,8 That these approaches have not yet led to the construction of harmonically organized complex tissues may be due to the difficulty of embedding the various cell types within the intricate designs. Our tissue engineering approach combines rapid prototyping procedures with microencapsulation to print viable freeform structures with custom-modified ink-jet printers.9-11 Inspired by developmental biology, this approach may provide the necessary cues, rules, and framework for hierarchic self-assembly. With this innovative technique, it is possible to place quickly and accurately a variety of cells layer by layer to create tissues faster than is possible with current methods.
In brief, ink-jet printers are modified by disabling the paper-feed mechanism and incorporating a stepper motor–controlled z-axis platform. An alginate-coated frame is used as a scaffold and was mounted on this z-axis platform. The ink cartridge is filled with bovine aortic endothelial cells in culture medium (bioink). This bioink is printed layer by layer, deep to superficial, onto the scaffold, resulting in a tubular structure measuring 50 mm long with an outer diameter of 4 mm.
We have printed tubes of many cell types this way, including Chinese hamster ovary cells, endothelial cells (Figure 1), smooth muscle cells, osteoblasts, and stem cells. Our initial studies focused on cellular viability, reducing bacterial contamination, and optimizing conditions of in vitro culture. We have printed dense, fused structures that can exhibit function when challenged with agonists in simple in vitro experiments. These include vasoconstriction properties of printed smooth muscle cell tubes and the potential of printed stem cells to differentiate into multiple lines, although we do not know yet how to control this differentiation.
|
A model of how this technique may be used for the assembly of more complex tissues is schematically shown in Figure 2. The first step is the detailed creation of a computer model of the structure to be created. The bioengineer will need to build up a layer-by-layer picture of the organ to be created by specifying the location, number, and type of cell within each layer. Once a computer-aided design file has been constructed, it can be saved and reused any number of times. The computer-aided design file is then transferred to the organ printer. This will be a purpose-built unit consisting of multiple nozzles and cartridges containing the different cell types and growth factors. The organ printer will have to be enclosed in a sterile environment in which the required structure is built layer by layer. Cellular viability will be maintained by choosing biocompatible polymers dissolved in isotonic buffer solution or culture media and noncytotoxic cross-linkers.
|
 |
References |
|---|
 Top References |
|---|
This article has been cited by other articles:
|
|
 |
|
  L. Tan, Y. Ren, and R. Kuijer A 1-min Method for Homogenous Cell Seeding in Porous Scaffolds J Biomater Appl, March 1, 2012; 26(7): 877 - 889. [Abstract] [PDF]
|
|
|
|
 |
|
 T. Burg, C. A. P. Cass, R. Groff, M. Pepper, and K. J. L. Burg Building off-the-shelf tissue-engineered composites Phil Trans R Soc A, April 28, 2010; 368(1917): 1839 - 1862. [Abstract] [Full Text] [PDF]
|
|
| ||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||
| HOME | HELP | FEEDBACK | SUBSCRIPTIONS | ARCHIVE | SEARCH | TABLE OF CONTENTS |
| ANN THORAC SURG | ASIAN CARDIOVASC THORAC ANN | EUR J CARDIOTHORAC SURG |
| J THORAC CARDIOVASC SURG | ICVTS | ALL CTSNet JOURNALS |
