Effect of advanced glycation end products on autophagic ability in osteoblasts.

Objectives: Excessive production of AGEs in diabetic patients will affect the normal function of osteoblasts, and this process may be related to autophagy of osteoblasts. This study aims to explore the effect of advanced glycation end products (AGEs) on autophagic activity during osteogenic differentiation in rat bone marrow mesenchymal stem cells (BMSCs).

Methods: BMSCs were isolated and cultured in vitro, treated with different concentrations (0, 50, 100, 200, and 400 mg/L) of AGEs for different time (3, 6, 12, 24, 48, and 72 h). The proliferation activity was detected by CCK-8 method. The mRNA and protein expression levels of Beclin1 and LC3 in cells were detected by real-time PCR and Western blotting, respectively.The autophagic vacuoles were observed under the transmission electron microscope. The cells were treated with autophagy promoter rapamycin or autophagy inhibitor 3MA. After 7 days of osteogenic induction, we performed alkaline phosphatase (ALP) staining and real-time PCR to detect the mRNA expression levels of osteogenesis-related genes.

Results: In the low-concentration groups, the proliferation activity in BMSCs was increased (<0.01), the mRNA and protein expressions of autophagy-related genes LC3 and Beclin1 were increased (both <0.01). The number of autophagosome also was increased. In the high-concentration groups, the results were just the opposite. In the low-concentration groups, the ALP staining was deeper than that of the 0 mg/L AGEs group, and the mRNA expressions of the osteogenic related genes were increased (<0.01). But the results were reversed in the presence of autophagy inhibitor 3MA. In the high-concentration groups, the ALP staining was lighter than that of the 0 mg/L AGEs group, and the mRNA expressions of the osteogenic related genes were decreased (<0.01). After the addition of the autophagy promoter rapamycin, the results were reversed.

Conclusions: Low concentration of AGEs can enhance the proliferative activity of BMSCs and promote osteogenic differentiation by accelerating autophagy. High concentration of AGEs can suppress the proliferation of BMSCs and inhibit osteogenic differentiation by reducing autophagy.