Regeneration Of Cartilaginous Tissue Research Articles

Computed tomography‐based tissue‐engineered scaffolds in craniomaxillofacial surgery

Tissue engineering provides an alternative modality allowing for decreased morbidity of donor site grafting and decreased rejection of less compatible alloplastic tissues. Using image-based design and computer software, a precisely sized and shaped scaffold for osseous tissue regeneration can be created via selective laser sintering. Polycaprolactone has been used to create a condylar ramus unit (CRU) scaffold for application in temporomandibular joint reconstruction in a Yucatan minipig animal model. Following sacrifice, micro-computed tomography and histology was used to demonstrate the efficacy of this particular scaffold design. A proof-of-concept surgery has demonstrated cartilaginous tissue regeneration along the articulating surface with exuberant osseous tissue formation. Bone volumes and tissue mineral density at both the 1 and 3 month time points demonstrated significant new bone growth interior and exterior to the scaffold. Computationally designed scaffolds can support masticatory function in a large animal model as well as both osseous and cartilage regeneration. Our group is continuing to evaluate multiple implant designs in both young and mature Yucatan minipig animals.

Cultivation of cell‐polymer cartilage implants in bioreactors

Cartilage implants for potential use in reconstructive or orthopedic surgery can be created by growing isolated cartilage cells (chondrocytes) in vitro on synthetic, biodegradable polymer scaffolds. The scaffolds provide specific three-dimensional structures which support cell proliferation and biodegrade in a controlled fashion in parallel to cellular regeneration of cartilaginous tissue. Cartilage implants based on chondrocytes and fibrous polyglycolic acid scaffolds were recently shown to closely resemble normal cartilage histologically as well as with respect to cell density and matrix composition (collagen, glycosaminoglycan) [Freed et al., J Biomed Mater Res 27:11-23, 1993a]. These findings form the basis for developing straightforward procedures to obtain implants for clinical use from small, autologous cartilage specimens without any limitations in terms of availability of donor tissue or implant dimensions. Chondrocyte growth and cartilage matrix regeneration on polymer scaffolds are interdependent and also depend on in vitro tissue culture conditions. Under static culture conditions, cell growth rates are diffusionally limited due to increasing cell mass and decreasing effective implant porosity resulting from cartilage matrix regeneration. Optimization of the in vitro culture environment is thus essential for the cultivation of large, clinically useful cartilage implants. Preliminary studies indicate that major improvements can be achieved using bioreactors that provide efficient mass transfer and controlled shear rates at the cell and implant surfaces.

Sympathetic auricular chondritis in rats: a model of autoimmune disease?

Following the unilateral implantation of metal ear tags in female Crl:CD(SD)BR-rats, chronic inflammatory lesions were observed in both auricles in 7% and 24% of the animals after 30 and 60 weeks, respectively. Involvement of the collateral auricles was identified only after diffuse inflammation of the ear tag-marked pinnae had developed. Histological examination revealed a multifocal granulomatous chondritis, characterized by progressive destruction of the cartilaginous plate and excessive regeneration of cartilaginous tissue. IgG and complement deposits were present in the matrix of the marginal area of regenerating cartilage and at the destruction sites of autochthonous cartilage. It is likely that the pinally-restricted chondritis was due to an autoimmune response initiated by a chronic inflammatory process at the insertion site of the ear tag. Since the response was not due to immunity to type II collagen, this pathologic phenomenon in rats may provide a useful animal model to study autoimmunity involving other cartilaginous matrix molecules.