Estradiol inhibits chondrogenic differentiation of mesenchymal stem cells via nonclassic signaling

AbstractObjectiveWe undertook this study to examine the effects of estradiol on chondrogenesis of human bone marrow–derived mesenchymal stem cells (MSCs), with consideration of sex‐dependent differences in cartilage repair.MethodsBone marrow was obtained from the iliac crest of young men. Density‐gradient centrifugation–separated human MSCs proliferated as a monolayer in serum‐containing medium. After confluence was achieved, aggregates were created and cultured in a serum‐free differentiation medium. We added different concentrations of 17β‐estradiol (E2) with or without the specific estrogen receptor inhibitor ICI 182.780, membrane‐impermeable E2–bovine serum albumin (E2‐BSA), ICI 182.780 alone, G‐1 (an agonist of G protein–coupled receptor 30 [GPR‐30]), and G15 (a GPR‐30 antagonist). After 21 days, the aggregates were analyzed histologically and immunohistochemically; we quantified synthesized type II collagen, DNA content, sulfated glycosaminoglycan (sGAG) concentrations, and type X collagen and matrix metalloproteinase 13 (MMP‐13) expression.ResultsThe existence of intracellular and membrane‐associated E2 receptors was shown at various stages of chondrogenesis. Smaller aggregates and significantly lower type II collagen and sGAG content were detected after treatment with E2 and E2‐BSA in a dose‐dependent manner. Furthermore, E2 enhanced type X collagen and MMP‐13 expression. Compared with estradiol alone, the coincubation of ICI 182.780 with estradiol enhanced suppression of chondrogenesis. Treatment with specific GPR‐30 agonists alone (G‐1 and ICI 182.780) resulted in a considerable inhibition of chondrogenesis. In addition, we found an enhancement of hypertrophy by G‐1. Furthermore, the specific GPR‐30 antagonist G15 reversed the GPR‐30–mediated inhibition of chondrogenesis and up‐regulation of hypertrophic gene expression.ConclusionThe experiments revealed a suppression of chondrogenesis by estradiol via membrane receptors (GPR‐30). The study opens new perspectives for influencing chondrogenesis on the basis of classic and nonclassic estradiol signaling.