Involvement of type VI collagen in interleukin-4-induced mineralization byhuman osteoblast-like cells in vitro

We recently showed that interleukin-4 (IL-4) enhanced collagen and osteocal cin accumulation and caused mineralization in human periosteal osteoblast-l ike (SaM-1) cells. At that time, the expression of alpha 1(VI) collagen mRN A was induced. In the present study, the possible role of IL-4-induced type VI collagen in the in vitro mineralization in osteoblasts was investigated . Addition of IL-4 in the early stage (for the first 10 days) was essential for the mineralization. The mRNA levels of alpha 1(VI) and alpha 2(VI) col lagen and protein level of type VI collagen were transiently increased by I L-4 treatment up to day 5, whereas the alpha 1(I) procollagen mRNA level wa s greater at day 10 than at day 5. Addition of anti-type VT collagen antibo dy remarkably reduced the extracellular accumulations of calcium and hydrox yproline induced by IL-4. Furthermore, the transfection of antisense oligon ucleotides of alpha 1(VI) to SaM-1 cells in the presence of IL-4 partially inhibited IL-4-induced type I collagen accumulation. These results demonstr ated that type VI collagen played important roles for IL-4-induced minerali zation and hydroxyproline accumulation, mostly type I collagen accumulation , in human periosteal osteoblast-like cells. (C) 1999 Elsevier Science B.V. All rights reserved.