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Critical time periods of melatonin exposure enhance osteoblast differentiation from human mesenchymal stem cells
Author(s) -
WittEnderby Paula Ann,
Sethi Shalini
Publication year - 2008
Publication title -
the faseb journal
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.709
H-Index - 277
eISSN - 1530-6860
pISSN - 0892-6638
DOI - 10.1096/fasebj.22.1_supplement.728.12
Subject(s) - melatonin , mesenchymal stem cell , alkaline phosphatase , osteoblast , medicine , endocrinology , chemistry , stem cell , calcium , microbiology and biotechnology , cellular differentiation , biology , in vitro , biochemistry , enzyme , gene
We have previously shown that melatonin enhances bone stem cell differentiation (hAMSCs) into osteoblasts following 10 days melatonin exposure, that is dependent upon MT2 melatonin receptors (MT2R), internalization and MEK(1/2). We extended the exposure to 21 days as calcium deposition, an essential component of bone differentiation process, takes place between 14 and 21 days in culture. The objective of this study was to determine the critical time periods of melatonin exposure during a 21 day exposure to osteogenic medium. HAMSCs were cultured in osteogenic medium for 21 days and then exposed to melatonin for 2, 5, 10, 14 and 21 days. Melatonin increased alkaline phosphatase (ALP) activity, a differentiation marker, when cells were exposed to melatonin for 2 days or 21 days. Calcium deposition was increased by about 900% in presence of melatonin, but this was seen only when the cells were co‐exposed to melatonin for 21 days. Melatonin's effects on ALP activity at days 2 and 21 were dependent upon MT2R, as these effects were blocked with 4P‐PDOT, an MT2R antagonist. RT‐PCR studies show an increase in early, intermediate and late genes involved in osteoblast differentiation, which is dependent upon the duration of melatonin exposure. These studies indicate that melatonin acting through MT2R can drive the differentiation of hAMSCs into osteoblasts, perhaps by activating different genes at critical time periods.