INTER-ALPHA-INHIBITOR IS REQUIRED FOR THE FORMATION OF THE HYALURONAN-CONTAINING COAT ORE FIBROBLASTS AND MESOTHELIAL CELLS

Cultured cells of various origins have been shown to be surrounded by a hyaluronan-containing coat, a structure that can be visualized by it s ability to exclude large particles such as erythrocytes. When cultur ed in medium with no Or low concentrations of serum, the cells lose th eir coats, although they still produce hyaluronan; upon the addition o f serum, the coats are formed again. Here, we show that the serum prot ein inter-alpha-inhibitor can replace whole serum as an inducer of the formation of the coats on fibroblasts and mesothelial cells. The phys iological role of inter alpha-inhibitor has so far been unclear; our f indings, together with those obtained with cumulus cell-oocyte complex es (Chen, L., Mao, S. J., and Larsen, W. J. (1992) J. Biol. Chen. 267, 12380-12386), suggest that inter-alpha inhibitor and related proteins have a general function as stabilizers of hyaluronan-containing peric ellular coats.