Human leukocyte histocompatibility antigen class II-induced cytokines from human gingival fibroblasts promote proliferation of human umbilical vein endothelial cells: potential association with enhanced angiogenesis in chronic periodontal inflammation

The role of human leukocyte histocompatibility antigen (HLA) class II molecules on non-antigen-presenting cells has been a matter of controversy. We previously reported that HLA-II molecules on human gingival fibroblasts (GF) do not present antigens, but transduce signals into the cells, resulting in the expression of several cytokines, such as interleukin-6 (IL-6), monocyte chemoattractant protein-1 (MCP-1), regulated upon activation, normal T-cell expressed and secreted (RANTES) and IL-8. However, the exact role of these cytokines, as well as other cytokines which are potentially secreted from GF, in the pathogenesis of chronic periodontal inflammation is not fully understood. The aim of this study was to observe the effects of HLA-II-induced cytokines on the proliferation of human umbilical vein endothelial cells (HUVEC). Antibody-based cytokine-microarray analyses were performed to detect potential cytokines associated with angiogenesis. Next, cytokine productivity was confirmed by quantitative methods. Then, cell proliferation assay was performed to see whether these cytokines promoted the proliferation of HUVEC. Besides IL-6, MCP-1, RANTES and IL-8, growth-related gene product (GRO) was newly identified as an HLA-II-induced cytokine released from GF. This was confirmed by a quantitative method. Cell culture supernatant from HLA-II-stimulated GF cultures promoted the growth of HUVEC. Addition of anti-IL-8 neutralizing antibody, anti-CXC receptor (CXCR)1 antibody and anti-MCP-1 antibody inhibited the growth of HUVEC in a dose-dependent manner, while addition of anti-GRO alpha antibody did not. The HLA-II-induced IL-8, via CXCR1, as well as MCP-1 from GF, promotes endothelial cell proliferation, which is possibly associated with enhanced angiogenesis in chronic periodontal lesions.