Method: hPDL was cultured in DMEM with variety of concentrations of PRL mimicked a non-pregnant (10 ng/ml), pregnant period (100 ng/ml) and pathological hyperprolactinemic conditions (600 and 1000 ng/ml). All isoforms of PRL receptor (PRLR) and its localization were investigated using RT-PCR and immunocytochemistry, respectively. Cell viability and the osteogenic differentiation were investigated after incubation with PRL for 24 and 48h.
Result: Short and long isoforms of PRLR mRNA were expressed in hPDL. The short isoform of PRLR gene was expressed in a greater amount when compared to that of the long isoform. Moreover, the PRLR proteins were localized all over hPDL membrane as well as cytoplasm. The incubation of PRL only at pathological levels (600 and 1000 ng/ml) significantly decreased hPDL cell number. PRL at non-reproductive level (10 ng/ml) and pregnant level (100 ng/ml) significantly upregulated markers of osteogenesis such as Runx2 and Bmp2 but not Sox9. However, periostin mRNA was not altered by PRL at any concentration.
Conclusion: The present study, for the first time, demonstrates the expression of PRL receptor in hPDL proposing the possible function of PRL in hPDL. The physiological levels of PRL upregulate the osteogenic genes expression, inducing hPDL to be differentiated into osteoblast or cementoblast.