Fate of a Chimeric Joint Construct in an Ectopic Site in SCID Mice

Shape, loading, and motion in the bioengineering design, fabrication, and testing of personalized synovial joints

With continued development and improvement of tissue engineering therapies for small articular lesions, increased attention is being focused on the challenge of engineering partial or whole synovial joints. Joint-scale constructs could have applications in the treatment of large areas of articular damage or in biological arthroplasty of severely degenerate joints. This review considers the roles of shape, loading and motion in synovial joint mechanobiology and their incorporation into the design, fabrication, and testing of engineered partial or whole joints. Incidence of degeneration, degree of impairment, and efficacy of current treatments are critical factors in choosing a target for joint bioengineering. The form and function of native joints may guide the design of engineered joint-scale constructs with respect to size, shape, and maturity. Fabrication challenges for joint-scale engineering include controlling chemo-mechano-biological microenvironments to promote the development and growth of multiple tissues with integrated interfaces or lubricated surfaces into anatomical shapes, and developing joint-scale bioreactors which nurture and stimulate the tissue with loading and motion. Finally, evaluation of load-bearing and tribological properties can range from tissue to joint scale and can focus on biological structure at present or after adaptation.

Collagen scaffolds for tissue engineering

There are two major approaches to tissue engineering for regeneration of tissues and organs. One involves cell-free materials and/or factors and one involves delivering cells to contribute to the regeneraion process. Of the many scaffold materials being investigated, collagen type I, with selective removal of its telopeptides, has been shown to have many advantageous features for both of these approaches. Highly porous collagen lattice sponges have been used to support in vitro growth of many types of tissues. Use of bioreactors to control in vitro perfusion of medium and to apply hydrostatic fluid pressure has been shown to enhance histogenesis in collagen scaffolds. Collagen sponges have also been developed to contain differentiating-inducing materials like demineralized bone to stimulate differentiation of cartilage tissue both in vitro and in vivo.

Phenotypic analysis of bovine chondrocytes cultured in 3D collagen sponges: effect of serum substitutes

Repair of damaged cartilage usually requires replacement tissue or substitute material. Tissue engineering is a promising means to produce replacement cartilage from autologous or allogeneic cell sources. Scaffolds provide a three-dimensional (3D) structure that is essential for chondrocyte function and synthesis of cartilage-specific matrix proteins (collagen type II, aggrecan) and sulfated proteoglycans. In this study, we assessed porous, 3D collagen sponges for in vitro engineering of cartilage in both standard and serum-free culture conditions. Bovine articular chondrocytes (bACs) cultured in 3D sponges accumulated and maintained cartilage matrix over 4 weeks, as assessed by quantitative measures of matrix content, synthesis, and gene expression. Chondrogenesis by bACs cultured with Nutridoma as a serum replacement was equivalent or better than control cultures in serum. In contrast, chondrogenesis in insulin-transferrin-selenium (ITS(+3)) serum replacement cultures was poor, apparently due to decreased cell survival. These data indicate that porous 3D collagen sponges maintain chondrocyte viability, shape, and synthetic activity by providing an environment favorable for high-density chondrogenesis. With quantitative assays for cartilage-specific gene expression and biochemical measures of chondrogenesis in these studies, we conclude that the collagen sponges have potential as a scaffold for cartilage tissue engineering.