KC chemokine expression by TGF-beta in C3H10T1/2 cells induced towards osteoblasts.

The effects of TGF-beta on expression of the platelet-derived growth factor-induced KC protein were explored in mouse mesenchymal C3H10T1/2 and pre-osteoblastic MC3T3-E1 cells to identify a potential role for TGF-beta in expression of angiogenic cytokines during osteogenic differentiation. KC is a member of the CXC chemokine family with homology to human IL-8, a potent neutrophilic chemotactic cytokine. TGF-beta treatment results in increased KC mRNA and protein secretion in C3H10T1/2 induced towards the osteoblastic lineage with all-trans-retinoic acid. This is due to up-regulated transcription rather than enhanced mRNA stability. No induction of KC expression was seen in untreated C3H10T1/2 or MC3T3-E1 upon TGF-beta stimulation. Use of the translational inhibitor cycloheximide results in mRNA "superinduction" suggesting other factors are involved that normally function to down-regulate KC expression. TGF-beta-stimulated conditioned media were a potent chemostimulant for human microvascular endothelial cells (HMEC-1). This activity could be inhibited by pre-incubation with anti-KC neutralizing antibodies.