Effect of 17β-estradiol on the proliferation of condylar chondrocytes.

OBJECTIVES

To study the effects of 17β-estradiol (E2) on the regulation of the proliferation of condylar chondrocytes and provide a preliminary discussion on the role of phosphorylate-mammalian target of rapamycin (p-mTOR) in this regulatory process.

METHODS

Condylar chondrocytes were isolated from 6-week-old female rats for primary culture. Drug treatment with different concentrations of E2 and/or rapamycin (RAPA) was carried out on second-generation cells. Cell Counting Kit 8 was used to measure the cell viability of condylar chondrocytes after culture for 24, 48, or 72 h, and reverse transcription-polymerase chain reaction (RT-PCR) was applied to detect the relative gene expression of estrogen receptor alpha (ERα), estrogen receptor beta (ERβ), collagen type Ⅱ (COLⅡ), autophagy-related gene 6 (Beclin-1), and autophagy-related gene 5 (ATG-5). Western blot was employed to determine the relative protein expression of ERα, ERβ, Beclin-1, lipid-modified light chain 3B (LC3-Ⅱ), and p-mTOR.

RESULTS

E2 could significantly promote the proliferation of chondrocytes cultured , and maximum promotion was achieved at a concentration of 10 mol·L. RAPA could significantly inhibit cell proliferation. E2 at aconcentration of 10 mol·L could greatly improve the gene expression levels of ERα and COLⅡ (0.01) with the protein levels of ERα and p-mTOR (0.05), and decrease the gene expression levels of Beclin-1 and ATG-5 (0.05) with the protein levels of Beclin-1 and LC3-Ⅱ (0.05). RAPA could also enhance the relative protein expression of Beclin-1 and LC3-Ⅱ (0.01), and reduce the expression of p-mTOR (0.01). Treatment with the ERα antagonist significantly reduced the expression of p-mTOR in cells (0.01).

CONCLUSIONS

At a concentration of 10 mol·L, E2 could effectively activate the phosphorylation of mTOR through the ERα-p-mTOR pathway, inhibit cell autophagy, and promote the proliferation of condylar chondrocytes.