Scaffolds in tissue engineering bone and cartilage
Introduction
Bone and cartilage generation by autogenous cell/tissue transplantation is one of the most promising techniques in orthopedic surgery and biomedical engineering [1]. Treatment concepts based on those techniques would eliminate problems of donor site scarcity, immune rejection and pathogen transfer [2]. Osteoblasts, chondrocytes and mesenchymal stem cells obtained from the patient's hard and soft tissues can be expanded in culture and seeded onto a scaffold that will slowly degrade and resorb as the tissue structures grow in vitro and/or in vivo [3]. The scaffold or three-dimensional (3-D) construct provides the necessary support for cells to proliferate and maintain their differentiated function, and its architecture defines the ultimate shape of the new bone and cartilage. Several scaffold materials have been investigated for tissue engineering bone and cartilage including hydroxyapatite (HA), poly(α-hydroxyesters), and natural polymers such as collagen and chitin. Several reviews have been published on the general properties and design features of biodegradable and bioresorbable polymers and scaffolds [4], [5], [6], [7], [8], [9], [10], [11], [12]. The aim of this paper is to complete the information collected so far, with special emphasis on the evaluation of the material and design characteristics which are of specific interest in tissue engineering the mesenchymal tissues bone and cartilage. The currently applied scaffold fabrication technologies, with special emphasis on the so-called solid-free form fabrication technologies, will also be bench marked. Finally, the paper discusses the author's research on the design and fabrication of 3-D scaffolds for tissue engineering an osteochondral transplant.
Section snippets
Polymer-based scaffold materials
The meaning and definition of the words biodegradable, bioerodable, bioresorbable and bioabsorbable (Table 1)—which are often used misleadingly in the tissue engineering literature—are of importance to discuss the rationale, function as well as chemical and physical properties of polymer-based scaffolds. In this paper, the polymer properties are based on the definitions given by Vert [13].
The tissue engineering program for bone and cartilage in the author's multidisciplinary research curriculum
Scaffold design
Skeletal tissue, such as bone and cartilage, is usually organized into 3-D structures in the body [36]. For the repair and generation of hard and ductile tissue, such as bone, scaffolds need to have a high elastic modulus in order to be retained in the space they were designated for; and also provide the tissue with adequate space for growth [37]. If the 3-D scaffold is used as a temporary load-bearing device (Strategy II), the mechanical properties would maintain that load for the required
Scaffold fabrication
A number of fabrication technologies have been applied to process biodegradable and bioresorbable materials into 3-D polymeric scaffolds of high porosity and surface area. The conventional techniques for scaffold fabrication include fiber bonding, solvent casting, particulate leaching, membrane lamination and melt molding (Table 4). Several papers have reviewed the past and current research on scaffold fabrication techniques [43], [44], [45]. However, none of those papers has directly compared
Tissue engineering of a articular cartilage–bone interface
Articular cartilage repair, regeneration and generation have been reviewed by Buckwalter and Mankin [75] as well as Newman [76]. Both the reports have concluded that in the last two decades, clinical and basic scientific investigations have shown that the implantation of artificial matrices, growth factors, perichondrium, and periosteum, can stimulate the formation of cartilaginous tissue in osteochondral and chondral defects in synovial fluids. However, the available evidence indicates that
Conclusions
The application of regulatory approved biomaterials to design and fabricate 3-D scaffolds has strongly supported the drive for the establishment of tissue engineering research. Reviewing the experimental and clinical studies, it can be concluded that the ideal scaffold and matrix material for tissue engineering bone and cartilage has not yet been developed. In general, the tissue engineers do not implement innovative scaffold fixation features into their design concept. However, from a clinical
References (82)
- et al.
Foreign body reactions to resorbable poly(l-lactide) bone plates and screws used for the fixation of unstable zygomatic fractures
J Maxillofac Surg
(1993) - et al.
Femoral shaft reconstruction using tissue engineered growth of bone
Int J Oral Maxillofac Surg
(1996) - et al.
Chondrogenesis in a cell–polymer-bioreactor system
Exp Cell Res
(1998) - et al.
Biological principles of bone induction
Orthopedic Clinics North America
(1987) - et al.
Chondrogenesis in a cell–polymer-bioreactor system
Exp Cell Res
(1998) - et al.
Tissue engineered construct design principles
- et al.
Fabrication of biodegradable polymer scaffolds for tissue engineering
- et al.
Preparation and characterization of poly(l-lactic acid) foams
Polymer
(1994) - et al.
Laminated three-dimensional biodegradable foams for use in tissue engineering
Biomaterials
(1993) - et al.
Manufacture of porous biodegradable polymer conduits by an extrusion process for guided tissue regeneration
Biomaterials
(1998)