LACK OF AUTOCRINE EFFECTS OF IL-6 ON HUMAN BONE-MARROW STROMAL OSTEOPROGENITOR CELLS

Interleukin-6 (IL-6) produced by osteoblastic cells plays an important role in the regulation of bone remodeling, mainly by stimulating oste oclast action. Although the IL-6 receptor is also found in osteoblasti c cells, whether IL-6 exerts autocrine effects on osteoblastic cells i s a matter of debate. This led us to study the effects of IL-6 on prol iferation, osteoblastic activity as well as mRNA expression of various osteoblastic proteins in human bone marrow stromal osteoprogenitor ce lls (hBMSC). IL-6 did not affect cell proliferation assessed by [H-3]- thymidine incorporation and osteoblastic activity determined by alkali ne phosphatase activity and Ca-45 incorporation. The expression of mRN As for alkaline phosphatase, alpha 1(I)-collagen, osteopontin and deco rin also did not change significantly by IL-6 treatment. These results show that IL-6 does not have a significant autocrine role in regard t o proliferation and osteoblastic activity of hBMSC.