Tissue engineering of cartilage in space

Tissue engineering of cartilage, i.e., the in vitro cultivation of cartilage cells on synthetic polymer scaffolds, was studied on the Mir Space Station and on Earth. Specifically, three-dimensional cell-polymer constructs consisting of bovine articular chondrocytes and polyglycolic acid scaffolds were grown in rotating bioreactors, first for 3 months on Earth and then for an additional 4 months on either Mir (10−4–10−6 g) or Earth (1 g). This mission provided a unique opportunity to study the feasibility of long-term cell culture flight experiments and to assess the effects of spaceflight on the growth and function of a model musculoskeletal tissue. Both environments yielded cartilaginous constructs, each weighing between 0.3 and 0.4 g and consisting of viable, differentiated cells that synthesized proteoglycan and type II collagen. Compared with the Earth group, Mir-grown constructs were more spherical, smaller, and mechanically inferior. The same bioreactor system can be used for a variety of controlled microgravity studies of cartilage and other tissues. These results may have implications for human spaceflight, e.g., a Mars mission, and clinical medicine, e.g., improved understanding of the effects of pseudo-weightlessness in prolonged immobilization, hydrotherapy, and intrauterine development.

Cultured adherent cells from marrow can serve as long-lasting precursor cells for bone, cartilage, and lung in irradiated mice.

Cells from transgenic mice expressing a human mini-gene for collagen I were used as markers to follow the fate of mesenchymal precursor cells from marrow that were partially enriched by adherence to plastic, expanded in culture, and then injected into irradiated mice. Sensitive PCR assays for the marker collagen I gene indicated that few of the donor cells were present in the recipient mice after 1 week, but 1-5 months later, the donor cells accounted for 1.5-12% of the cells in bone, cartilage, and lung in addition to marrow and spleen. A PCR in situ assay on lung indicated that the donor cells diffusely populated the parenchyma, and reverse transcription-PCR assays indicated that the marker collagen I gene was expressed in a tissue-specific manner. The results, therefore, demonstrated that mesenchymal precursor cells from marrow that are expanded in culture can serve as long-lasting precursors for mesenchymal cells in bone, cartilage, and lung. They suggest that cells may be particularly attractive targets for gene therapy ex vivo.