Effect of apelin on human osteoblasts / 中华内分泌代谢杂志

ABSTRACT

Objective To observe apelin and its receptor (APJ) expressions in human osteoblasts and evaluate the effect of apelin on osteoblasts.Methods The expressions of apelin and APJ in human osteoblasts were tested by RT-PCR and Western blot.After human osteoblasts were treated with apelin,cell proliferation was measured by [~3H] thymidine incorporation and cell counting.Cell function was measured by alkaline phosphatase (ALP) activity,the secreted osteocalcin level and typeⅠcollagen production .The activation of signaling cascades was tested by Western blot.Small-interfering RNA (siRNA) to blockade APJ was applied to observe effects of apelin on cell proliferation and the activation of signaling cascades.Results Both apelin and APJ were expressed in human osteoblasts.Apelin increased the proliferation and did not show the influences on ALP activity, osteocalcin secretion and type I collagen production in human osteoblasts.Apelin induced activation of phosphatidylinositol-3 kinase (PI3K) downstream effector (Akt),but not mitogen-activated protein kinase (MAPK) such as c-jun N-terminal kinase (JNK),p38 and ERK1/2 in human osteoblasts.Suppression of APJ with siRNA or LY294002 (PI3K inhibitor) abolished the apelin-induced cell proliferation and the activation of Akt.Conclusion Human osteoblasts express apelin and APJ.Apelin stimulates the proliferation of human osteoblast via APJ/PI3K/Akt pathway,but has no effect on osteoblast differentiation.