Bone Abstracts

Introduction: Most chronic inflammatory bone diseases are characterized by loss of bone density due to an increase of osteoclastic activity without equally increased osteoblast activity which in turn is leading to an imbalance in bone repair and remodelling. Several studies have reported that green tea rich in polyphenols especially catechins could improve bone mass and structure and eventually increase bone formation. Data on black tea, also rich in polyphenols especially theaflavins however are scarce. The aims of this study were to compare green (GTP) and black tea polyphenol (BTP) treatment with regards to their influence on normal human osteoblast (NHOst) alkaline phosphatase (ALP) activity and bone matrix mineralization under normal and inflammatory conditions.

Methods: Total phenolic content (TPC) of green and black tea hot water extracts were determined by Folin-Ciocalteau method. NHOst cells were plated, induced with 0 and 1 ng/ml of TNF-α and treated with 5, 10, 50, and 100 μg/ml of GTP and BTP respectively at 2, 5 and 10 days. ALP activity was measured colorimetrically using an ALP reagent of p-nitrophenylphosphate (PNPP). Determination and quantification of mineralized bone nodules were assessed by alizarin red staining (ARS) technique. The dye was extracted from stained cells and quantitatively confirmed using a spectrophotometer.

Results: TPC measured for GTP and BTP were 77.1 and 83.13 mg GAE/g respectively. All BTP doses stimulated ALP activity in normal condition at each of the treatment days (P<0.05) except for 100 μg/ml dose at day 2. BTP managed to reverse ALP activity suppressed by TNF-α at all time points except for 50 μg/ml dose at day 2. Results demonstrated that ALP activity was increased with lower doses of GTP (5 μg/ml) at day 2 and 5 while in TNF-α presence, same dose exhibited same effect at day 2 (P<0.05) and day 5. ARS affirmed the presence of calcific depositions by cells. Increase in mineralized areas was observed by the presence of bright coloured bone nodules. Under normal conditions GTP and BTP enhanced mineralization with all tested doses significantly at all time points (P<0.05) implying that these polyphenols elevated osteogenesis in NHOst. In inflammation, all GTP and BTP doses exhibited a significant increase in ARS intensity (P<0.05) on day 2.5 μg/ml of both polyphenols induced mineralization on day 5, evident by a significant increase of ARS intensity (P<0.05). Likewise 50 (P<0.01) and 100 μg/ml (P<0.05) GTP significantly induced mineralization on day 5. All results were compared to control.

Conclusion: BTP exerted comparable anabolic effect to GTP on TNF-α stimulated NHOst by elevating ALP activity and mineralization thereby enhancing bone formation.