Bone Abstracts

Introduction: Recent studies have found anti-inflammatory, antioxidant and bone forming properties of green (GTP) and black tea (BTP) polyphenols. However most of these studies are focussed on specific genes or pathways. We wanted to know if GTP and BTP could help to reduce symptoms of chronic inflammation especially bone loss and what are the possible genes and pathways involved. We were especially interested in unexplored pathways which may play a role in regaining bone health. Therefore we used microarray to obtain an overview of significantly regulated genes and pathways involved in the response of chronic inflamed osteoblasts towards GTP and BTP.

Methodology: Normal human osteoblast (NHOst) were stimulated with 1 ng/ml TNF-α and treated with 5 μg/ml of GTP and BTP for 5 days. Affymetrix GeneChip Human Gene 1.0 ST was used and data analysis was performed by GeneSpring GX12.5 analysis software (Agilent Technologies, Inc., Santa Clara, CA, USA). Up- and down-regulated genes were determined with significant cut-off value of P<0.01 for each gene. DAVID (http://david.abcc.ncifcrf.gov/) and Panther Classification system (http://www.pantherdb.org) were used for annotation and visualization of pathways of significant regulated genes.

Results and discussion: Microarray analysis revealed 607 significantly regulated genes classified into 89 pathways. Most differentially expressed genes were observed in the Integrin signalling pathway (22 genes) and Inflammation mediated by chemokine and cytokine signalling pathway (20 genes) suggesting that GTP and BTP influence cell survival, differentiation, growth and inflammatory response of chronic stimulated osteoblast cells. Additionally a series of significantly regulated genes were found to be associated with the Wnt signalling pathway and TGFβ signalling pathway indicating the influence of GTP and BTP on osteoblast proliferation, differentiation and function, which could explain the bone forming properties of GTP and BTP treatment. Besides the above mentioned pathways we also found differentially expressed genes associated with apoptosis, however if these genes induce or inhibit apoptosis requires more investigations.

Conclusion and future directions: The present preliminary study showed promising results that GTP and BTP can significantly alter TNFα induced global changes in gene expression. As most of the significantly regulated pathways are connected with cytokine response and inflammation GTP and BTP seem to be able to revert TNFα induced inflammation and improve osteoblast function and differentiation regulated by genes of the Wnt pathway. Confirmatory studies of significantly expressed genes and proteins will be conducted next.