A low-serum medium for tendon cells: effects of growth factors on tendon cell growth and collagen production.

Primary avian tendon cells maintain a higher percentage of net collagen synthesis when cultured in low serum concentrations than in high. However, under these conditions the cells grow slowly and can only be subcultured one or two times. We therefore examined various growth factors for their effects on tendon cell multiplication in order to develop a new medium for these cells. Of the growth factors tested, epidermal growth factor, insulin, transferrin, and selenium each stimulated tendon cell division. We also investigated how these factors affected collagen synthesis, and found that they all increased both collagen and noncollagen protein synthesis equally, thus leaving the percentage of protein synthesis devoted to collagen the same. When combined with 0.2% fetal bovine serum in Ham's F12 medium, epidermal growth factor and insulin together stimulated cell multiplication to a level comparable to that of cells grown in Ham's F12 plus 10% serum. Cells could also be successfully subcultured in this medium. Thus, by using selected growth factors we have reduced significantly the serum requirements of cultured tendon cells without affecting population doubling time or subculture capability. This low-serum medium should prove useful for the study of the regulation of collagen biosynthesis.