Tissue engineering of cartilage in space

Abstract

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.

Figure 1

Experimental design. Cartilage cells were seeded onto polymer scaffolds, and the resulting constructs were cultivated in rotating bioreactors first for 3 months on Earth and then for 4 additional months either on the Mir Space Station (10⁻⁴–10⁻⁶ g) or on Earth (1 g).

Figure 2

Cell viability postflight. Cells isolated from a 7-month construct from the Mir group after 2 days of monolayer culture. (×200.) Intracellular esterase activity is indicated by green color.

Figure 3

Construct structure. (A and B) Full cross sections of constructs from Mir and Earth groups. (×10.) (C and D) Representative areas at the construct surfaces. (×200.) GAG is stained red with safranin-O.

Figure 4

Construct ultrastructure. Transmission electron micrographs of constructs from Mir (A) and Earth (B) groups at magnifications of ×3,500 and ×120,000 (Inset).