The Effects of Extracellular pH on Proliferation and Differentiation of human Bone Marrow Stem Cells

Objectives: The purpose of this study is to identify whether the change of pH affects the proliferation and the differentiation of human bone marrow stem cells (hBMSCs) and what mechanism is underlied. Methods: To achieve objective of this study, hBMSCs were cultivated in the conditioned media adjusted to potential of hydrogen (pH) ranging from 6.4 to 8.0 using addition of hydrochloric acid (HCl) and sodium hydroxide (NaOH). The ratio of proliferation of hBMSCs according to the change of pH was measured for 24 h, 48 h, and 72 h using water-soluble tetrazolium salt (WST)-8 method. To elucidate the mechanism involved, hBMSCs was subjected to blocking extracellular signal-regulated kinases (ERK) and calcium sensing receptor (CaSR) activation. The Osteogenicrelated genes and alkaline phosphatase (ALP) activity were tested under the conditioned media. Results: The proliferation of hBMSCs was promoted under extracellular alkali conditions (pH 7.6~8.0) via CaSR/ ERK pathway. On the other hand, the differentiation was inhibited/delayed via decreased ALP activity besides gene expression at pH 8.0. Conclusion: Extracellular alkali or acidic surrounding according to pH alteration can play a crucial role in hBMSC behavior including the proliferation and the differentiation. [Korean Journal of Bone Metabolism, 19(1): 35-46, 2012]