Regulatory Role of Stanniocaicin 1 in Osteoblastic and Osteoclastic Differentiation

Abstract

ABSTRACT

Regulatory Role of Stanniocalcin1 in Osteoblastic and Osteoclastic Differentiation

Hwa Sung Chae Department of Molecular Genetics The Graduate School Seoul National University (Directed by Prof. Jeong-Hwa Baek, D.D.S., Ph.D.)

According to the pressure-tension theory in orthodontics, the first physiologic response in the pressure side during tooth movement is hypoxia in periodontal ligament (PDL). We recently performed a preliminary microarray analysis to examine differentially expressed genes in human PDL exposed to hypoxic condition for 24 hours and identified Stanniocalcin 1 (STC1) as one of the most significantly upregulated genes. The purpose of this thesis was to study the functional role of STC1 in the regulation of cell viability, osteoblast differentiation and osteoclast differentiation. To address the purposes, the primary cultured PDL cells were purchased from ATCC. Gaspak pouch was used to induce hypoxia. To evaluate apoptosis, quantification of the cells positively stained with Annexin V/Propidium Iodide and western blot analysis against Caspase 3 were performed. To investigate the effect of STC1, overexpression or knockdown of STC1 was induced. Treatment of cells with recombinant STC1 protein or neutralizing antibody to STC1 was also used. Osteogenic differentiation was evaluated by examining the expression levels of osteogenic marker genes, the activity of alkaline phosphatase, and matrix calcification. Osteoclastogenesis was induced by treating RAW264.7 or primary cultured mouse bone marrow-derived macrophages with RANKL. Osteoclast differentiation was evaluated by examining the expression levels of osteoclastogenesis related genes and the number of tartrate-resistant acid phosphatase (TRAP)-positive multinucleated cells. Under the hypoxic condition, PDL cells exhibited increased the expression levels of STC1. In addition, hypoxia increased the number of apoptotic cells and activation of caspase 3, which were attenuated by addition of rhSTC1. Under the normoxic conditions, knockdown of STC1 promoted apoptosis. When PDL cells were induced to undergo osteogenic differentiation, the expression of STC1 increased in a time-dependent manner. Overexpression of STC1 or recombinant STC treatment significantly increased osteogenic differentiation of PLD cells, whereas knockdown of STC1 or addition of STC1-neutralizing antibody attenuated osteogenic differentiation. STC1 induced the expression of VEGF, and knockdown of VEGF significantly suppressed STC1-induced osteogenic differentiation. STC1 inhibited the formation of TRAP-positive multinucleated cells as well as the expression of osteoclast marker genes. Taken together, these results suggest that hypoxia-induced STC1 in compression side contribute to the prevention of excessive alveolar bone loss or root resorption by protecting the cells from apoptotic cell death, enhancing osteogenic differentiation and inhibiting osteoclast differentiation.